Oregon State University SEA SOLAR PLANTS A FEASIBILITY STUDY

Ocean Engineering Design Project

Ocean Engineering Programs School of Engineering OREGON STATE UNIVERSITY Corvallis, Oregon

Spring 1974 Ocean Engineering Oregon State University

SEA SOLAR PLANTS A FEASIBILITY STUDY

Ocean Engineering Design Project

by

Robert Arneson Allen Boyce Byungho Choi Don Debok Blaine Hafen Thomas Heinecke Bruce Higgins Donie/ Lodd James Leshuk William Mercer James Wright Ken Hoven, Editor

Lorry Slotto, Professor Advisor to Ocean Engineering Design Class, CE 573

Spring 1974 FORWARD

This publication is the accumulation of the individual final reports of the thirteen students involved in Oregon State University's

Ocean Engineering Design Class from March 27 to June 5, 1974.

Ocean Engineering involves the application of the tools of all traditional engineering disciplines for the planning, design, construc­ tion, inspection and maintenance of systems used with and for the devel­ opment and protection of the oceanic environment. A relatively new and extremely challenging area within this broad field is the economical ex­ traction of energy from the sea. The storehouses for this energy within the sea include currents, waves, and thermal gradients among others.

The Ocean Engineering Design class for this term limited study solely to thermal energy conversion.

Student backgrounds entering the class included Ocean Engineering,

Civil Engineering, Mechanical Engineering, Economics, Oceanography and

Marine Resources Management. This diversity of background and experience provided for a full range of student viewpoints which greatly enhanced the advancement of our technical understanding of thermal energy conver­ sion concepts. With few exceptions, the students had no prior exposure to sea thermal energy conversion and had to build individually into the problem from their own background.

The unifying goal within the class was to establish whether or not a Sea Solar Power Plant concept was feasible, and, if so, whether or not the concept could be made practical. More specifically, the class

ii divided into two basic groups; the first concerned with the feasibility of physically sizing, constructing, operating and locating the plant, while the second concerned itself with the impact of the plant on the local environment and with the impact of that environment on the plant.

Throughout the short study period, time was our most precious re­ source. The procurement of outside lecturers, literature searches, and even individual tasks were adopted, initiated, and ended based on a pro­ ductivity per unit time input criterion. This rather unique project set-up prompted the initiation of the PERT analysis of our efforts by

Allen Boyce.

This then was our general approach for a first step into a very large field. It is hoped that this study will help to form a base for future studies at OSU and elsewhere to expand and refine our findings.

Larry S. Slotta, Director Kendall F. Haven

Ocean Engineering Programs Editor

iii ACKNOWLEDGEMENTS

Our many thanks are extended to Dr. Robert Zaworski,

Milt Larson, John Nath, and Tokuo Yamamoto for their unself­

ish donation of time and effort as both guest lecturers and

in individual conferences throughout the stuqy period. With­

out their guidance our efforts would have only produced a

small fraction of our actual final output.

Many thanks are also due to Miss Janice Baker and Mrs.

Susan Ellinwood for their excellent typing of this report,

and for their help in its organization and publication.

Finally, our deepest thanks are extended to Dr. Larry

Slotta, the class project director. His continued help with,

and criticism of our ideas and concepts contributed more than

any other single factor to our overall learning process and

in particular to our understanding of the sea thermal power

problem.

iv TABLE OF CONTENTS

PAGE PERT ANALYSIS OF PLANT FEASIBILITY STUDY by Allen Boyce ...... 3

SITE SELECTION by Bob Arneson. 25

HEAT EXCHANGER ANALYSIS by Dan Ladd. 35

PLANT SIZING by Don Debok and Jim Leshuk 55

MOORING AND ANCHORING SYSTEM DESIGN by Jim Wright, Blaine Hafen, &Byungho Choi . . . . 89

GEOLOGY AND BIOLOGY OF THE MIAMI PLANT SITE by Bruce Higgens...... 131

EFFECTS OF ENTRAINMENT AND INTAKE SCREENING CONSIDERATIONS by Ken Haven ...... 157

BIOFOULING CONSIDERATIONS by Thomas Heinecke 193

ENVIRONMENTAL IMPACT-AQUACULTURE POTENTIAL by William Mercer ...... 205

v SEA SOLAR POWER PLANTS

A FEASIBILITY STUDY

1

SEA SOLAR POWER PLANT - PERT ANALYSIS of PLANT FEASIBILITY STUDY

by

Allen Boyce

ABSTRACT

A Procedure Evaluation and Review complete a task. A Probabilistic Fac­ Technique (PERT) Analysis is applied to tor is also applied to some activities the conceptual design of a Solar Sea to account for repititions that may be Power Plant (SSPP) because of the lim­ required in an effort to reach an opti­ ited time within which the project has mal design. A time chart is constructed to be completed. A PERT analysis rath­ and manpower leveling applied to esti­ er than a Critical Path Method (CPM) mate the least possible duration of the was used because of the variability in project and best allocation of manpower time duration of activities required to to required activities.

3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 \,,\ • SEA SOLAR POWER PLANT - PERT ANALYSIS of PLANT FEASIBILITY STUDY

by

Allen Boyce

INTRODUCTION 9. Biofouling Prevention Methods study. The tasks undertaken in the Sea Solar Power Plant Feasibility Study are by no 10. Energy trade-off analysis. means intended to exemplify all those tasks required for the design and con­ 11. Maricultures Study. struction of a Solar Sea Power Plant. Tasks were chosen scrutinously in an ef­ 12. Environmental Impact Statement. fort to concentrate on those areas of greatest interest and concern, yet still These tasks were broken down into com­ allowing for the conceptual design as a ponent activities to give the level of whole. The initial tasks chosen were as control necessary for management of the follows: project.

1. A Study of Thermal Cycle requirements A three week orientation and organiaa­ for low temperature gradient power tion period is included on the PERT net­ production. work chart as an informational sidelight. This period was not considered as a part 2. An investigation into different of the PERT analysis. The activities possible working fluids. were:

3. A possible power output evaluation. A. Introduction to project by Dr. Slotta 4. A complete design of Heat Exchangers. B. Thermodynamics lecture by Dr. 5. An analysis of pumping requirements. Zaworski

6. A size and configuration design. C. Heat Transfer lecture by Dr. Larsen 7. Stationing on position design. D. Wave Forces &Mooring design 8. Design of screening devices. lecture by Dr. Nath

5 E. Large Volume pump design lecture or group of activities comprising a task by Associate Prcfessor Tom has therefore, become indefinite as has Heinecke the time duration for completion of the entire project. This is typical of a F. Literature revie'" of publications research oriented project delving in a by Massachussetts Un~versity and new field. A CPM analysis requires exact Carnegie-Mellon Institute of estimates of activity times which is not Technology on th3 subject possible here. Also, a PERT analysis allows for the application of probabilis­ G. Organization period tics.

PERT ANALYSIS PROBABILISTIC FACTORS

A PERT Analysis is applied to this There are several places in the design project because of the indeterminacy of where loops are encountered. This is exact times for the duration of activi­ caused primarily by the dependency of the ties necessary for the completion of the power output on the sizing of subsequent project. As an example of the typical units. To site the major example the situation encountered, consider the task pumping power requirements are dependent of "sight selection." In order to find on the heat exchanger sizes which are de­ a sight suitable for power production pendent on the power output desired. with the once through cool system of a Therefore, for a given net power output solar sea power plant, it is necessary we must increase the gross power produc­ to first situate the pl~nt in an area tion of the plant by the amount of power where an adequate temperature gradient required for pumping which in turn, in­ exists between the surface V'arm water creases the heat exchanger sizes and the and lower depth cool waters. It is also pumping requirement. This interdepen­ necessary to have adequate ~epth to keep dency contradicts a basic assumption of the cool water uptake & distance from the PERT method which states that the the bottom without exposing the primary precedence relationships of project ac­ structure to the influence of surface tivities must be completely represented currents and wave forces. Once these by a noncyclical network graph in which two criteria have been met it is then each activity connects directly to its necessary to establish the nearest pop~ immediate predecessor (Weist and Levy, centers and power transmission require­ 1969). Neither PERT nor CPM allows for ments. It may happen that there are no conditional activities or cyclical areas within the regions established by orderings. criterias 1 and 2 which meet 3. It is then necessary to reevaluate and adjust To account for the possibility of the initial criterion for 1, 2, and 3 having to repeat activities a probabilis­ and begin the sight selccti0n process tic factor may be applied to the initial over again or continue on the basis of time durations arrived at using the con­ the reevaluation. The readjustment of ventional PERT assumptions. It should be the criterion for any activities that noted that the probabilistic factor may are dependent on 1, 2, or 3 may also be not be applied to all the activities necessary. Even though initial design within a loop since the need for revamping criteria were established, they are of any designs is dependent on the magnitude necessity prone to alte·cation. The time of the correction when compared to the duration for completion of any activity overall design criteria. It can be seen

6 that some design aspects within a loop PROBABILITY FACTORS are sensitive to subsequent changes while others are not. n-1 General Egn: p = L: To account for the probability of re­ n i=O peating an activity more than once in coming up with an optimal design "Proba­ X....probability of no itterations bility Factors" will be given for each Y...•probability of having to itterate activity. More than one probability P ...probability of n itterations factor may be applied to some activities n which are contained in more than one loop. In this manner an activity dura­ LOOP 1: Activity #30 back to Activity #3 tion may be arrived at without distort­ ing the initial time duration estimates Assume 98% chance of only four ittera­ arrived at using the convention PERT tions therefore, Probability Factor assumptions. equals .75 by trial &error. Another alternative is to simply lump p = 4~1 X(Y)n 4 dependent activities into one activity i=O and/or increase the pessimistic time es­ 1 2 = .75 + .75(.15) + .75(.15) + timate for the activity(s) duration. Neither alternative is considered viable .75(.15) 3 = 98% because the relationship of the schedule Activities Affected: 3,9,11,13,14,16, to the actual process being modeled is 18,20,22,23,24,30. lessened.

It is more commnn to find activity LOOP 2: Activity #46 back to Activity #40 interdependencies existing because of lumping activities together which affords Assume 99% adequate design in three the simple remedy of breaking the activi­ itterations. Probability Factor equals ties into smaller tasks. .80 by trial and error.

Exact probability factors were re­ P = 3il (. 20 )n-l 3 solved from estimates given by the indi­ i=O viduals working on those phases of the 2 .80 + .80(.20) + .80(.20) project within each loop. The procedure = was to estimate as close as possible the = 99%. least number of itterations required to Activities Affected: 40, 42, 43, 44, insure a nearly 100% chance of comple­ 45, 46. tion. If some doubt did exist, but was not substantial enough to assume a high­ er number of itterations, the 100% fac­ LOOP 3: Activity #56 back to Activity #40 tor was adjusted as can be noted for loop 1 and loop 2. The general proba­ Assume 100% chance of adequate design bility equation used was arrived at by in three itterations. Probability Factor consideration of conventional applica­ = • 90. tions of probability to problems of this nature. From the general equation the P = 3~1 .90(.10)n-l 3 appropriate probability factor 'X' to be i=O 2 applied to each loop was solved by trial = .90 + (.90)(.10) + (.90)(.10) and error. = 99.9%

7 Activities Affected: 40, 42, 43, 44, may be optimistic (see resource alloca­ 45, 46, 51, 52, 55, 56. tion constraints). The extreme would be to assume only one man works on each ac­ tivity. To complete the project in six TABLE 1. NOTATIONS weeks this individual would have to work 64-1/2 hours per week. The closest esti­ Abbreviation Definition mate to the actual situation is 2-3 men per activity. At three men per activity H. E. Heat Exchanger on the critical path a work load of 22 W.W. WarnunWater hours per week is required to complete c.w. Cold Water the project in six weeks. W.F. Workir,g Fluid THRM'L. Thermal EXT. E:;ztraneous RESOURCE ALLOCATION PT. Point COMB. Combined A man power leveling was performed for CONV. Conventional the time table established from the PERT EMBED. Embediment time estimates in an effort to optimize E. I. Environmental manpower utilization over the span of the EFF. Effect project. The initial group of ten men is MARl. Maricl'lture split into two groups of five each, a structural design group and an environ­ mental group. The work of the men in these groups is restricted to activities PROBABILITY OF MEETING DUE ~ATE that fall under their specific category. The category which each of the activities D-Te comes under is fairly evident. Biofouling General Egn: z = -­ St and screening were included under the environmental groups tasks. It is also Z...... Probability number assumed that once a man is assigned toa D...... Due Date task he must stay on it to completion-­ Te······ .. Sum of time estimates on unless two men are already assigned to it. critical path These constraints were made to try to fit St········Standard Deviation of acti­ as closely as possible the actual condi­ vities on cri~ica1 path tions of the project. A man is assumed to work about sixteen hours per week. D = 6 wks x 16 hrs/wk x 4 men 384 hrs It was found that over the first half l:Te cr1t1ca· · 1 pat h = 387 hrs of the project that the structural group 1 2 carries the majority of the work load S [IVt ] / t = critical path = while the environmental group waits for needed information. During the later z = 384 - 387 = - 23 11.35 . portion of the project the critical ac­ tivities are shifted from the structural Probability of meeting due Gate = 40% group to the environmental group. The primary reason for this is the prerequi­ The above analysis assumGs four of site constraints of the activity. the men working on the project are available to work on cTitical activi­ Through an allocation of manpower a ties. In reality becaus0 of the con­ considerable shortening of the project straints imposed by splitting into duration can be accomplished. The total groups to handle different tasks this time duration for the project was

8 TABLE 2. PERT TIME ESTIMATES

Activity times Variance Expected Time Probability Adj. Ex­ # Activit,t t 0 tm tQ Vt Factor pect Time l Pumping Study 30 48 56 18.78 46 46 2 Temp. Theory 4 8 11 1.36 8 8 3 Power Out 6 13 15 2.25 12 .75 16 4 Temp. Sea 3 4 8 .69 5 5 5 Bathemetry 2 5 8 1.00 6 6 6 Upwelling 3 7 12 2.25 7 7 7 Biofou1 Envr. 6 10 13 1.36 10 10 8 Working Fluid 20 32 42. 13.44 32 32 9 H.E. Matr'l 8 11 15 1.36 12 .75 16 10 Inter. Flow 5 9 13 1.78 9 9 11 H.E. Surface 14 20 25 2.25 10 .75 13 12 Pop.!l Centers 3 6 7 •4-4 6 10 13 Boiler 16 21 26 2.78 21 .75 28 14 Condenser 16 21 26 2.78 21 .75 28 15 Trans. & Dist. 8 10 11 .69 10 10 16 W.W. Flow 3 5 6 .25 5 .75. 7 17 W.W. Pipes 2 5 7 ·. 69 5 5 i8 C.W. Flow 4 6 9 .69 6 .75 8 19 C.W. Pipes 6 8 10 .44 8 6 20 W.F. Flow 5 6 7 .11 6 .75 8 21 W.F. Pipes 4 5 6 .11 5 5 22 W.W. Pumps 2 2 2 0.00 2 .75 3 23 W.C. Pumps 2 2 2 0.00 2 .75 3 24 W.F. Pumps 3 4 5 .11 4 .75 5 25 Sediment 3 5 7 .44 5 5 26 Currents 5 10 12 1.36 10 10 27 Shipping 3 5 7 .44 5 5 28 Biofoul Growth 12 18 21 2.25 18 18 29 Site 11 18 20 2.25 17 17 30 Thrml. Cycle 17 24 30 4.69 24 .75 32 31 Boil 'r Housing 6 9 15 2.25 10 10 32 Condnsr Hsn'g 6 12 l7 3.36 12 12 33 Support Syst. 5 6 9 .44 6 6 34 Biology @ Site 28 36 45 8.03 36 36 35 Machinery 4 4 4 0.00 . 4 4 36 Ext. Pipe 4 8 12 1. 78 8 8 37 Weight 8 14 16 1. 78 14 14 38 Power/Cost 8 24 30 13.44 23 23 39 Bouyancy 4 8 12 1.78 8 8 40 Shape 8 12 16 1. 78 12 ( .80)( .90) 17 41 Maricultures 8 14 16 1. 78 14 14 42 Waves 7 8 9 .11 8 (.80)(.90) 11 43 Wind 9 10 11 .11 10 (.80)(.90) 14 44 Current Forces 7 8 9 .11 8 ( .80)( .90) 11 45 Misc. Forces 8 10 14 1.00 10 ( .80)( .90) 14 46 Stability 12 30 42 25.00 23 ( .80){ .90) 32

9 TABLE 2. cont.

Activity Times Variance Expected Time Probability Adj. Ex­ # Activity to tm tR Factor pect Time 47 Entrmnt. Fouling 8 10 14 1.00 10 10 48 Entrmnt. Biota 8 10 12 .44 10 10 49 Biofoul-Struc. 3 5 8 .69 5 5 50 Biofoul-Operat'n 5 8 17 4.00 8 8 51 Pt. Mooring 10 12 17 1.36 13 .90 15 52 Dyn. Position'g 10 12 17 1.36 13 .90 15 53 Screens 4 12 19 6.25 12 12 54 Biofou1 Prevent'n 12 18 24 4.00 18 18 55 Mult. Pt. Mooring 5 8 9 .44 8 .90 9 56 Comb. Pas. Syst. 6 9 11 .69 9 .90 10 57 Conv. Anchoring 8 12 14 1.00 12 12 58 Embed. Anchoring g 12 18 2.78 12 12 59 E. I. Entra i nmnt. 4 6 8 .44 6 6 60 E. I. Impingement 4 6 8 .44 6 6 61 Sea Circulation 3 5 10 1. 78 6 6 62 E. I. Circulation 6 12 18 4.00 12 12 63 Upwell Eff. Mari. 6 12 14 1.78 12 12 64 Imping. Eff. Mari. 2 3 4 .11 3 3 65 Biofou1 Eff. Mari. 3 6 7 .44 6 6 66 E.I. Biofoul Prvnt 3 6 l .44 6 6 67 Mari. Struc. 6 12 15 3.36 12 12 68 E. I. r~ari. 3 4 5 .11 14 14 69 E. I. Statement 10 12 18 1.78 13 13 70 Bene/Cost Mari. ,g 10 15 1. 36 11 11 71 Write-Up 65 8 108 51 .36 80 80

10 TABLE 3. BOUNDARY TIME TABLE

# ACTIVITY EARLY START LATE START EARLY FINISH LATE FINISH FLOAT

1 Pumping Study 0 51 46 97 51 2 Temp. Theory 0 0 8 8 0 3 Power Out 0 24 3 40 24 4 Temp. Sea 0 93 6 99 93 5 Bathemetry 0 93 6 99 93 6 Upwelling 0 244 7 251 244 7 Biofoul Envr. 0 217 10 227 217 8 Working Fluid 8 8 40 40 0 9 H. E. Matr '1 40 40 56 56 0 10 Inter Flow 40 47 49 56 7 11 H. E. Surface 56 56 69 69 0 12 Pop.!!. Centers 6 99 12 105 93 13 Bioler 69 69 97 97 0 14 Condenser 69 69 97 97 0 i5 Trans &Dist 12 105 22 115 93 16 W.W. Flow 97 100 104 107 3 17 W.W. Pipes 97 102 .102 107 5 18 C. W. Flow 97 99 105 107 2 19 C.W. Pipes 97 99 105 107 2 20 W.F. Flow 97 97 105 105 0 21 W.F. Pipes 97 100 102 105 3 22 W.W. Pumps 104 107 107 110 3 23 C.W. Pumps 105 107 108 110 2 24 W.F. Pumps 105 105 110 110 0 25 Sediment 22 100 47 125 78 26 Currents 22 115 32 125 93 27 Shipping 22 120 27 125 . 98 28 Biofoul Growth 10 227 28 245 217 29 Site 32 125 49 142 93 30 Thrml Cycle 110 110 142 142 0 31 Biol•r Housn'g 142 144 158 154 2 32 Condns•r Housn'g 142 142 154 154 0 33 Support System 142 148 148 154 !6 34 Biology @Site 49 201 85 237 152 35 Machinery 154 158 158 162 4 36 Ext. Pipe 154 154 162 162 0 37 Weight 162 162 176 176 0 38 Power/Cost 176 283 199 306 107 39 Bouyancy 176 176 184 184 0 40 Shape 184 184 201 201 0 41 Maricultures 7 251 21 265 244 42 Waves 201 204 212 215 3 43 Winds 201 201 215 215 b 44 Current Force 201 204 212 215 3 45 Misc. Forces 201 201 215 215 0 4q Stabi 1ity 215 215 247 247 0

11 TABLE 3. cont.

# ACTIVITY EARLY START LATE START EARLY FINISH LATE FINISH FLOAT

47 Entrnmt Fouling 201 237 211 247 36 48 Entrnmt Biota 201 237 211 247 36 49 Biofoul-Struc. 201 248 206 253 47 50 Biofoul-Operat'n 201 245 209 253 44 51 Ptl Mooring 247 260 262 275 13 52 Dyn. Position'g 247 269 262 284 22 53 Screens 247 247 259 259 0 54 Biofoul. Prvn't 209 253 227 271 44 55 Mult. Pt. Mooring 262} 275 271 . 284 13 56 . Comb. Pas. Syst. 271 284 281 294 13 57 Conv. Anchoring 281 294 •293 306 13 58 Embed. Anchoring 281 294 293 306 13 59 E.I. Entrainmnt 259 287 265 293 28 60 E. I. Impi ngmnt 259 287 265 293 28 61 Sea Circulation 259 259 265 265 0 62 E. I. Ci rc u1 at ion 265 281 277 293 16 63 Upwelling Eff. Mari. 265 265 277 277 0 64 Impinge Eff. Mari. 259 274 262 277 15 65 Biofoul Eff. Mari. 227 271 233 277 44 66 E.I. Biofoul Prvn't 227 287 233 293 60 67 t·1ari. Structure 277 277 289 289 0 68 E. I. Ma ri 289 289 293 293 0 69 E. I. Statement 293 293 306 306 0 70 Benefit/Cost Mari. 289 295 300 306 6 71 Write-Up 306 306 387 387 0

12 shortened from 387 hours to 117 hours. helps to clarify interdependencies of It can also be seen that three of the activities and time constraints which individuals in the environmental group are crucial with a project of limited are not needed until mid way through the duration. The critical activities can project. A further reduction in the be identified and the most judicious project duration could be realized if use of manpower applied in· order to the constraint allowing individuals to avoid time delays or unnecessarily over­ work only on activities within their burdening any one individuals responsi­ group was removed. bilities. By referring to the bar chart at the completion of activities it is possible to see if the proposed schedule BEGINNING AND ENDING NODES is being met. In the event that it is not, future slack period:::; \•here time Often confusion is generated in the can be made up are easily identified. use of activity diagrams because of in­ If slack periods are not available then adequate information about when an acti­ other management alternatives available vity begins and when it is complete. To such as eliminating portions of tasks, help alleviate this problem and further shifting the work load or working clarify activity descriptions the begin­ overtime can be considered. ning and ending points for each activity are given in the following table. Imme­ The advantage of activity diagrams diate prerequisites to each activity are and bar charts is difficult to measure, also given. but certainly clarity in activity re­ lationships and time durations contri­ butes to the smooth flow and ultimate CONCLUSIONS success of a project.

An activity diagram is of consider­ The complete PERT Network is shown able aide as a management tool. It in Figure 1; Resource Allocation in Figure 2; and Time Allocation in Figure 3.

REFERENCE

Weist, J. and Levy F. A Management Guide to PERT/CPM. Englewood Cliffs, N.J. Prentice-Hall, Inc. 1969.

13 TABLE 4. BEGINNING &END NODE DESCRIPTIONS

Activity Description Beginning &End Nodes Prerequisites

Begin: Literature Study at Library after task commitments 1. Cold Water Pumping Methods: End: Recommendations for pumping

Begin: Text Study of Workable Temperature ranges for power p·rodL:ction after task commit!Tients 2. ·remperature Range Theory Ana'Jys is: End: A workable theory for low temperature range power production Begin: Review of power production of preceding power units after task commitments 3. Gross Power Output Calculations: End: Recommendation for magnitude of power production ...... ~ Begin: Collect published material on subject after task commitment 4. Temperature Gradient of the Sea Study: End: When regions of adequate temperature range resolved Begin: Survey Bathemetry Maps 5. Bathemetry Investigation: End: When regions of adequate depth resolved

Begin: Search for published material on topic 6. Ocean Upwell in~ Study: End: Documentation of effects

Begin: Locate material on the subject 7. Biofouling as a Func. of Ocean Envir. Research: End: Documentation -- possibly chart of depth vs. creatures Begin: List all possible fluids 8. Optimum Working Fluid Investigation: End: Recommendation for specific fluid TABLE 4. cont.

Begin: F1om workillg fltJid l4 powei' range (pressure drop) list compatible materials 2 9. Heat Exchanger Material Analysis: End: Recommendations for compatible materials

Begin: When working fluid &power output recommended. 10. Working Fluid Flow Circulation Design: End: When flow pattern design requirement specified. 3,8

Begin: When flow pattern &material recommendations complete 11. Heat Exchanger Surface Configuration Design: End: When optimal configuration for heat transfer 3,8 documented Begin: Search for published material on regions near 12. Population & Industrial Centers Proximity Study: sea 9,10 End: When regions located ~documented , ...... (Ff Begin: Review recommendations for fluid &surface configuration 4,5 13. Size Boiler Units: End: When optimal unit size calculated &documen­ ted Begin: Review recommendations for fluid &surface configuration 14. Size Condenser Units: End: When optimal unit size calculated &documen­ 11 ted Begin: Review po~ &power needs near coast and distance to depth 11 15. Power Transmission &Distrib. System Design: End: Recommendation for type of transmission system Begin: Review bioler &condenser size 16. Calculate Warm Water Flow Rates: 12 End: List flow rates for unit designs

Begin: Review bioler &condenser size 17. Design Piping System Warm Water: 1, 13,14 End: When optimum theoretical piping design found TABLE 4. cont.

Begin: Review boiler &condenser sizes 1,13,14 18. Calculate Cold Water Flow Rates: End: List flow rates for unit design

Begin: Review boiler &condenser sizes 1,13,14 19. Design Piping System Cold Water: End: When optimum theoretical piping design found Begin: Review boiler &condenser requirements 20. Calculate Working Fluid Flow Rates: End: List flow rates through each unit 1,13,14

Begin: Review Boiler &condenser unit designs 21. Design Working Fluid Piping System: End: When piping design with material compati­ 1,13,.14

>-' bility found Q'\ Begin: When flow rates &piping system for warm water completed . 22. Design Pumping Units Warm Water: End: When power required calculated 1,13,14

Begin: When flow rates &piping system for cold water completed 23. Design Pumping Units Cold Water: End: When power required calculated .. 16,17.

Begin: Whenoflow rates &piping system for work­ ing fluid completed · 18,19 24. Design Pumping Units Working Fluid: End: When power required calculated

Begin: Search for bott~m ~urvey ~ublicatior.s with­ in power transm1ss1o~ reg1o~s . 25. Bottom Sediment Survey: End: When material on sed1ments 1n reg1ons docu­ 20,21 men ted Begin: Search for current profile material within - power transmission regions 26. Current Profile Analysis: End: When material documented 15 TABLE 4. cont.

Begin: Search for shipping lane maps in power 27. Shipping Channels Investigation: transmission regions 15 End: When material documented Begin: Upon identification of biofouling creatures 28. Biofouling Creatures Growth Rate Survey: End: When growth rates for pertinent creatures 7 established Begin: When material on sediments, temperature, 29. Site Selection: depth, shipping ¤ts compiled 25,26,27 End: When adequate size documented Begin: Review power &cycle requirements for units 30. Optimization of Thermal Cycle: End: When requirements for optimum cycle at 22,23,24 specific size met Begin: When size of unit for optimum thermal cycle 31. Size Boiler Housing: found 30,29 ,..... End: When housing size &material documented --.J Begin: When size of unit for optimum thermal cycle 32. Size Condenser Housing: found 30,29 End: When housing size &materials documented Begin: When size of thermal units found 33. Size Support System: 30,29 End: When recommendation for operation &required support system documented Begin: When sight selected 34. Biology of SSPP Sight Investigation: 29 End: When all relevant obtainable material documented Begin: Housing &support system requirements 35. Size Extraneous Machinery Required: completed 31,32,33 End: When major machinery placement decided upon Begin: Housing &support system requirements 36. Design Extraneous Piping Required: completed 31,32,33 End: When piping sizes &placement specified TABLE 4. cont.

Begin: :Jnit sizes & extraneous requirements specified 35,36 37. Calculate Weight Distribution: End: List weights Begin: Review weights &material specifications 38. Power/Cost Trade-Off Analysis: End: Recommendation on economy of plant 37 Begin: Calculate distribution of weights 39. Design Bouyancy Compensators: End: Documented recomme!'.nations on met!tcd: 37 size &placement Begin: Review unit sizts &bouyancy compensator 40. Design Configuration of Plant: sizes of compensator 39 End: Configuration recommendation Begin: Literature review of material on the 41. A Study of Maricultures: subject 6 End: Document possible maricultures at plant site f-' 00 Begin: Look at wave theory in relation to design 42. Calculate Wave Forces: configuration &placement 40 End: Documentation of forces Begin: Collect material on wind in region of site 43. Calculate Wind Forces: End: Document forces due to plant configuration 40 Begin: Review current data from site selection 44. Calculate Current Forces: End: Document forces on plant due to configuration 40 &placement in current Begin: List miscellaneous forces that could be acted 45. Calculate Other Source Forces: End: Document calculated forces acting &conditions 40 Begin: Compilation of all forces acting 46. Orientation Stability Analysis: End: Stable orientation recommendation 42,43,44,45 Begin: Review Biology for types biota entrained 47. Effect on Entrainment on Plant Operation: End: List effects, cause, remedies 40,34 TABLE 4. cont.

Begin: Review biology for types biota entrained 48. Effect of entrainment on Biota: 40,34 End: List adverse effects &cause Begin: Review design configuration &biology of 49. Structural Effects of Biofouling: sight 40,34,28 End: List adverse effects and further design considerations Begin: Review plant flow &materials imposed 50. Biofouling Influence on Plant Performance: End: 40,34,28 List possible performance hindrance &cause Begin: Review stability requirements, forces & 51. Single Pt. Mooring Analysis: weight distribution 46 End: Investigation into multiple pt. mooring Begin: Review stability requirements 52. Dynamic Positioning Analysis: 46 End: Recommendation with power requirement f-' (.0 specifications Begin: Analysis of entrainment results & 53. Design Screening Device: configuration effects 46,47,48 End: Documented design for required screening Begin: When types &rates of growth of biofouling 54. Biofouling Prevention Methods: creatures on structure complete 49,50 End: Documented recommendations from latest literature on innovative design Begin: When single pt. mooring analysis complete 55. Multiple Pt. Mooring Analysis: End: Searched into possible combined dynamic & 51 pt. mooring systems Begin: When dynamic and multiple pt. investigation 56. Combined Positioning Systems: recommendations documented 52,55 End: When review of all positioning system recommendations made Ti\1\LE 4. cont.

Begin: When design recommendations for 57. Conventional Anchoring Design: positioning made 56 End: When field thoroughly investigated & recommendations documented Begin: When design recommendations for 58. Embedient Anchoring Design: positioning made 56 End: When field thoroughly investigated & recomraendation:::. documented Begin: Review effect entrainment on biota 59. Environmental Impact Entrainment: 52 End: Documentation of impact concerns Begin: Review effect of impingement 60. Environmental Impact Impingement: 52 End: Documentation of impact concerns Begin: Review screening device flow patterns 61. Sea Circulation About SSPP: 52 N End: Diagramming of flow pattern 0 Begin: Review of upwelling &flow pattern 62. Environmental Impact Circulation & 40,61 Upwelling: End: Document impact considerations Begin: Review upwelling flow pattern 63. Circulation Upwelling Effect on & & 40,61 Mariculture: End: Document possible effects

Begin: ~fuen impingement effects on biota 64. Impingement effect on Mariculture: documented 40,53 End: Adverse effects documented

65. Biofouling Prevention Influence on Begin: When biofouling prevention method decided 40,54 Mariculture: End: Impact consideration documented Begin: When biofouling prevention method 66. Environmental Impact Biofouling Prevention Method: decided 54 End: Impact consideratior documented TABLE 4. cont.

Begin: When circulation, biofouling agents & 67. Mariculture Containment Structures: screening effect known 63,64,65 End: When possible structures conceptual design completed Begin: When type of culture &structures known 68. Environmental Impact Maricultures: 67 End: When documentation of possible effects complete Begin: When all structural, operational, biology 69. Environmental Impact Statement: aspects documented 59,60,62,68,66 End: Necessary considerations documented Begin: When mariculture type &structure 70. Benefit/Cost Analysis of Maricultures: investigation complete 67 End: When analysis documented

N ...... Begin: When final recommendations complete 71. Write-Up: 38,57,69,70 End: When last page typed

SOLAR SEA POWER PLANT PERT NETWORK

38

..~/1~> 7. . ~ ,'I-'

57 7 12, 1.00 87, 51.36

121105 I \ 15 I \ 10, .69 \ \ \ \ I I \ \ I I \ \ \ \ \

6 41 7, 2.25 14, 1. 78

28 18, 2 . 2!5 LEGEND'

Activity no. Duration, Variance SOLAR SEA POWER PLANT RESOURCE ALLOCATION

cr>­ w 0 PUMP STUDY 0:: 2 w ::> ::r: WORKING 1 f­ H. E. THRM L CURRENT 3 FLUID 1 w t; a..: MATR L I BOILER CYCLE ::> H. E. a.. 1------i ~

- . TRANS S DIST CURRENTS SITE ENTRNMNT BIOTA 1­ BIOLOGY @ SITE ~ 7 I SEA TEMP I BIOFOUL . ENVR. I ISEDIMENT :::i: z 8 0 ~ 9 > r5 10

SOLAR SEA P 0 WE R PLANT TIME C H ART

POWER I COST ~------~------176 199

WAVES "'

CURRENT FORCE r;----r.---­SUPPORT SYST 142 148

PUMPING STUDY MISC. FORCES PT. MOORING EMBED. ANCHORING _

293

COMB. , TEMP THEORY WORKING FLUID 801 LE R WF FLOW PUMP THR'ML CYCLE EXT PIPE I WEIGHT BUOYANCY SHAPE WIND STABILITY POS. SYST. lcoNV. ANCHORINJ( _ f WRI;!'E,-UP

40 56 ~ D ~ 104 IS4 12 215 247 2il ~~ 293 ~ > ,.fo======;o£\ I 8 I I POWER OUT FLJ_!t____ CONDENSER [w.F PIPEl : E.L ENTRN~r:!I______~~------liNTER. l 1 I 1\ 16 40 49 69 97 102 10 t SEDIMENT I ~ I ~---- 20! 27 I TEMP SEA 1SHIPP,!_~Q __ ------J 22 27

SITE BIOLOGY (I) SITE •9

28 209 233 293 306 SEA SOLAR POWER PLANT ­ SITE SELECTION

by

Bob Arneson

ABSTRACT

The processes of selecting a site lo­ the current was that it offered the nec­ cation for the Sea Solar Power Plant are essary temperature profile for operation discussed. One major area not included of the sea solar power plant. A benefit is political bearing on the siting. The received from the current is the disper­ location chosen is approximately 16 sal of the warm condenser discharge miles east of Miami, Florida in the At­ water before it can be recycled into the lantic Ocean . It is positioned in the boiler intake. The close proximity of Florida Current which follows the conti­ major population centers provides poten­ nental shelf along the coast of Florida. tial customers for the power generated The major reason for choosing a site in by the plant.

25

SEA SOLAR POWER PLANT - SITE SELECTION

by

Bob Arneson

INTRODUCTION PROPOSED SITE

The process of site selection can be The exact location of the proposed plant approached from a number of different site is 25° 53' N, 79° 50' W. This is 16 viewpoints. Some of the factors which miles off the coast of Miami, Florida. A must be considered are the water depth, site temperature profile taken by the Uni­ bottom conditions, current, wave data, versity of Miami on January 18, 1963 at temperature gradient, and proximity to 25° 36' N, 79° 53' W is shown in Table 1. population and shipping lanes. Of these This is close to the selected site, and is the one which must be given top priority also within the Florida Current, so it may is the temperature gradient, since this be considered representative of on site is the theoretical basis for the solar conditions. sea power plant. Other groups have found suitable sites which exhibit this It can be seen from Table 1 that temper­ necessary temperature gradient. For the ature remains essentially constant down to United States these include areas in the 83 meters, · where it reaches a fairly sterp Gulf Stream and along the southern Cali­ thermocline. From 377 meters to the bottom fornia coast (Solar Sea Power Plant Con­ it is again essentially constant. The ference, 1973). This study has chosen a sounding at this position was 444 meters site in the Florida Current which flows (University of Miami, 1964). The surface north along the continental shelf be­ layer of 23°C water will be used for the tween Florida and Cuba and the Bahamas. warm water intake and the 8°C water taken At approximately 33° N, which is just from depth is the cold waterr condenser sup­ south of Cape Hatteras, North Carolina, ply. Although there are seasonal varia­ the current leaves the shelf and goes tions of this temperature profile, they northeast into deep water. It JOlns the do not appear to be of sufficient magni­ Antilles Current to become the Gulf tude to halt plant operations (Stommel, Stream (Stommel, 1958). 1958).

27 TABLE 1. TEMPERATURE PROFILE IN THE layers (8°C or less). If a position were FLORIDA.STRAITS chosen where only minimal clearance for (University of Miami, 1964, pp 20-22) the pipe was obtained, there would be a tendency for wave action, however slight, Depth, '1'emperature, to cause grounding of the pipe. There in :ln degrees would also be a suction of the bottom ma­ meters centigrade terials into the cold water intake. The selected location provides several hundred 1 23.88 feet of separation from the bottom, thus 9 23.88 eliminating these potential problems. 18 23.86 Conversely, it would not be desirable to 32 23.46 chose a site in very deep water. Added 83 22.14 depth would increase the anchoring prob­ 133 18.94 lems and costs. 182 15.00 280 9.66 By being only 16 miles off the coast of 377 8.33 Miami, the plant will be easy to reach by 424 8.08 both helicopters and small surface ships. 433 8.05 Even though it is not planned to exchange crews more than once every several weeks, being relatively close to shore makes this operation a short and simple procedure. Since we are dependeut on this temp­ Further, transportation of produced power erature difference which exists in the to shore by cable over that distance will current, any meandering by the current be relatively inexpensive, easy, and will could seriously affect plant operations. exhibit minimum line loss. The plant site In 1937, Church demonstrated that the is also in the vicinity of large popula­ position of the Gulf Stream is not al­ tion centers to consume the electrical ways the same. In 1950, from results output. of the Multiple Ship Survey, meanders in the Gulf Stream were again observed Even though the plant is going to be (Stommel, 1958). More 1ecent investiga­ submerged most of the time, it would still tions have also been conducted on these not be desirable to place it in a shipping meanders (Robinson, 1974). None of lane. Some deep draft ships would pose these studies showed data in the Gulf potential hazzards, especially in adverse Stream south of Cape Hatteras. However, weather conditions. Further, the plant it appears that the Florida Current in would pose a hazzard to all shipping when the region of this site does not meander surfaced. The chosen site location is or shift its position radically (Stommel several miles west of the shipping lanes. 1958). Therefore, it appears that the (Atlas of Pilot Charts, 1955). However, necessary temperature profile will re­ it would still be prudent to have a lighted main on site throughout the year. buoy marking the position of the plant.

On Figure 1, it is s~en that the The current is the resource which causes depth of water at the p1ant site is 300 the favorable temperature profile. It is fathoms, or 1800 feet. This depth was also what causes the problems of position­ chosen for several reasons. The water ing the plant. The magnitude of the cur­ must be deep enough for the cold water rent can be seen on the profile in Figure pipe to penetrate to the bottom cold 2 from University of Miami May data, 1964.

28 G H

200

(f) n::: w ~ w 400 ~ z I I I I ~ 600 Q_ SITE~ w 0 LOCATION l I ® I 800 I I I I (CURRENT IN KNOTS)

FIGURE 1. May Plant Current Profile (U.S. Naval Oceanographic Office, 1965)

29 E F

\ " \ \ .. \ ... \ . . \ \ .. I 200 I .. I .... I .. I · I ... . . (/) ~ .. 0:: \S ...... w I .... r- I I .. w I I .. 400 \ I ... ~ \ I .·· \ I .. z ,_/ /

I r­ ()_ w 600 0 ®

800 .. ..·~...... • • ••..·~••• =~: ...... -=-_:·---:.·: ·: :._· : . . . (CURRENT IN KNOTS)

FIGURE 2. August Plant Current Profile (U.S. Naval Oceanographic Office, 1965)

30 The coordinates of points G and H are 25° The current is a major drag force on the 55' N, 80° 04' W and 25° 47' N, 79° 16' plant. The other factors to consider are W, respectively. The dotted line shows the wave action and wind forces. If the the location of the plant. At this point plant were a floating or semi-submerged the current decreases from 3.5 knots at design it would be prudent to design for the surface to zero at 500 meters. The the most severe conditions. A margin of N indicates that the general direction of safety would also have to be included. flow is to the north. The flow in the Since the plant will be submerged with the current is always northerly; however, exception of crew changes and some main­ there is evidence to indicate slight tenance, it is not necessary to take the southerly flow on the edges of the cur­ most sever conditions as design factors. rent. This phenomenon, occuring in Aug­ It is desired to operate the plant at a ust, is shown on Figure 3. The coordi­ depth below the affect of surface forces nates of points E and F are 25° 39' N, and wave action. If the surface conditions 79° 56' Wand 25° 27' N, 79° 16'W, re­ are worse than those designed for, the spectively. Although the speed of the plant can remain submerged until conditions current is continuously changing, a sea­ permit surfacing for required crew changes. sonal comparison of surface current shown on Table 2 indicates the mean The wave and wind forces for the area speed and percentage of the time at a of the plant vary seasonally as the current certain speed to be relatively constant. does. The roughest month is September with the waves being greater than 12 feet Another asset provided by the current three percent of the time with a maximum is a mixing and dispersal of the warm height of 28 feet. The wind is Beaufort water as it leaves the condenser. This Force 7-12, three percent of the time, or should preclude recycling of condenser greater than 28 knots (U.S. Naval Oceano­ discharge to warm water intake. Due to graphic Office, 1963). the great depth to the cold water and the fact that the warm water is less Political and social considerations dense. There should be no problem of have not been mentioned. They are many the warm water sinking and being recir­ and varied and it is felt that they are culated into the cold water intake. beyond the scope of this report. For those wishing to investigate this area, background should be provided by the oil TABLE 2. SURFACE CURRENTS IN THE companies from their vast experience with FLORIDA STRAITS. the oil platforms. (U.S. Naval Oceanographic Office, 1965)

Directional Speed, Time at CONCLUSIONS Season mean speed, in Speed in knots knots (%) 1. The selected site (25° 53'N, 79° 50'W) >4 5 will provide a stable thermal gradient on a Winter 3.0-3.9 24 year round basis sufficient for plant (January, 2.5 N 2.0-2.9 31 operation. February, 2.0 NE 1.0-1.9 23 March) 0.1-0.9 17 2. Other site advantages, including: local water depth, proximity to major population >4 8 centers and to shore, local current to re­ Summer 3.0-3.9 29 move exhaust flows and site seperation from (July, 2.7 N 2.0-2.9 29 shipping lanes, far outweigh the one main August, 2.0 NE 1. 0-1.9 18 site disadvantage of increased drag force September) 0.1-0.9 16 from relatively high local currents.

31 BATHYMETRY OF FLORIDA STRAITS AND THE BAHAMA ISLANDS >l ', tOO '-t.j \ \

~·1, S? ~ ~ 2POO'N CONTOUR INTER-/··.~~\ vAL =5o FATHoMs::\ · :.::·:: I . ~' \ UNCERTAIN ... 1 C::JNTOURS . i I ....:.I ADDED . : : CONTOUFlS (oth '/ th<..n 50 fathom·::_: [ ln~ervol) · .· ::": / . ·.-::·:! 0 ~FIORUEGG~I-~~ D RIDGE •

CAY 25°30'N GJ :::0 [Tl l> --1 rn l> :r 25°00'N l> ~ l> rn l> 2 .24°30'N A:

FIGURE 3. Bathymetry of Florida Straits and the Bahama Islands (U.S. Naval Oceanographic Office, 1965)

32 REFERENCES

Atlas of Pilot Charts, Central American Waters and South Atlantic Ocean, H.O. Pub. No. 576, Second Edition. 1955. U.S. Navy Hydrographic Office, Washington, D.C. March, 1955.

Hurley, R.J. "Topography of the Straits of Florida." Investigations of American Tropical and Subtropical Seas. Institute of Marine Science, University of Miami, Miami, Florida. July 1963.

Oceanographic Atlas of the Nortb Atlantic Ocean, Section I Sea and Swell. Pub. No. 700, U.S. Naval Oceanographic Office, Washington, D.C. 1963.

Oceanographic Atlas of the North Atlantic Ocean, Section II Tides and Currents. Pub. ~o. 700, U.S. Naval Oceanographic Office, Washington, D.C. 1965.

Robinson, A.R., Luyten, J.R., and Fulister, F.G. "Transient Gulf Stream Meandering. Part I: An Observational Experiment." Journal of Physical Oceanography. 4(2): 237-254, April, 1974.

Stommel, Henry. The Gulf Stream. London: Cambridge University Press. 1958.

Sverdrup, H.V., Johnson, M.W. and Flemming, R.N. The Oceans. Englewood Cliffs, N.J.: Prentice Hall, Inc. 1942.

University of Miami. "A Report of Data Obtained in the Florida Straits and Off the West Coast of Florida, January- June, 1963." 64(1). Institute of Marine Science, University of Miami, January 1964.

"Workshop On: Power Plant Siting, Economic and Political Problems, Environmental Considerations." Proceedings, Solar Sea.Power Plant Conference and Workshop. Carnegie -Mellon University, Pittsburg,· Pennsylvania, June, 1973.

33

SEA SOLAR POWER PLANT - HEAT EXCHANGER ANALYSIS

by

Dan Ladd

ABSTRACT

This discussion shows the procedure ments go down for higher heat ex­ used in analyzing the operating charac­ changer-water temperature differences. teristics of a particular heat exchanger design. The design used was chosen for (2) Surface area decreases, while pumping its ease of construction and maintenance. power increases for increasing water The operating parameters varied were the velocity. condensing and evaporating temperatures, the water velocity through the exchangers, (3) Flow area decreases for increasing and the exit water temperatures. The de­ water inlet-outlet temperature wired design parameters were the heat ex­ differences. changer volume, surface area, flow area and pumping power requirements for parti­ Finally, the optimum design consists of cular operating conditions. balancing the heat exchanger operating characteristics within the physical The conclusions reached were: limitations of a sea solar power plant (I) Surface area and pumping require­ design.

35 j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j SEA SOLAR POWER PLANT - HEAT EXCHANGER ANALYSIS

by

Dan Ladd

INTRODUCTION u Overall heat transfer coeffi­ cient, One of the most important considera­ Btu tions in any attempted design of a sea Hr ft 2 °F solar power plant, is the design of the Heat transfer area, referred heat exchangers, as these represent the to U, ft2 largest and most expensive components of LMTD Logrithmic mean temperature any conceivable plant. This discussion difference, oF shows the procedure used analyzing the . Volume flow rate, operating characteristics of a particu­ v sec lar heat exchanger design, operating at .f. h Btu the conditions of a particular site loca­ c Speel 1c eat, ~F tion. The operating parameters varied Exit temperature were the condensing and evaporating temp­ Texit eratures, the water velocity through the T. Inlet temperature exchangers, and the water exit tempera­ ln lb tures. The heat exchange design parame­ G Area volume flow rate, -­ ters desired were the volume, surface ft2sec area, flow area, and pumping power re­ f Friction factor quirements for particular operating con­ lb ditions. Nomenclature used for this re­ p Density, ft3 port is listed in Table 1.

TABLE 1. NOMENCLATURE AMMONIA CYCLE Symbol Definition Figure 1 is a skematic of the heat Btu Q Heat flow rate, --­ engine cycle proposed for the Sea Solar sec Power Plant (SSPP). Ammonia was chosen as the working fluid as it appears that Heat flow rate at the evapor­ this is the most satisfactory fluid, from ator purely efficiency considerations (Olson, et al., 1973). Thermodynamic analysis of Heat flow rate at the conden­ the ammonia cycle res'Jlts in the follov:j ng ser equations .• Btu Q = MN (hl- h4) ...... (1) h Specific enthalpy, -rb evap • H3 lb (h3- h2) ...... (2) Mass flow rate, --­ Qcond = ~NH3 sec [(h - h )-(h - h )] ... (3) Work ne t= --NH3M__ 2 1 4 3

7.7 0 QEVAP. WORK I ·"'EVAP ~-----__,..._...TURBINE

PUMP 0 OcoNo

ENTROPY

FIGU~E 1. Ideal Ammonia Cycle

33 Figure 2 is a result of calculations or, using the above equations. The temper­ U = Aht ~LMTD) ...... (4a) 3 ature difference refers to difference and, Pumping Power= G Ahtf ······· ·· (S) between the cycle working fluid temper­ 2p atures and the seawater ambient tempera­ 2 or, f = (Pumping Power) 2p ...... (Sa) tures in the condensor and evaporator where seawater temperatures are taken to G3~t be 47°F and 73°F for cold and warm water intakes respectively. It is assumed U is calculated as the inverse of the that these temperature differences are sum of the individual heat transfer re­ the same for both the evaporator and sistances. The assumptions involved in condensor. Thermodynamic data was taken the calculation of U are as follows. The from Van Wylen- Sonntag (1965). Tur­ condensing and evaporating coefficients bine and pump were assigned efficiencies were taken to be the same and equal to of 85%. This figure is representative Btu of existing designs and is adequate for 800 hr ft 2 oF . the level of calculations presented. Although this is certainly wrong, any analysis that involves changing the par­ ticular inside heat transfer coefficients HEAT EXCHANGER DESIGN involves the ammonia velocity which de­ pends on the individual heat exchanger Figure 3 is a cross section of the geometry, for which this analysis heat exchanger design used. This design hopes to solve. In any case, the inside was chosen for its ease of construction heat transfer coefficients have negligi­ and maintenance, and because of its rel­ ble effect on the overall resistance, and atively low cost with reasonable heat the value picked is certainly on the con­ transfer characteristics (Anderson, servative side. The inside and outside Sept. 1973). Aluminum was chosen as the fouling resistances were taken to be heat exchanger material primarily be­ 005 hr ft2 oF cause of its good heat transfer charac­ · Btu teristics. Work done by J.H. Anderson The water side resistances were taken (Sept. 1973) considered many different from Table 5.4.1, lines 26 to 29, J.H. materials, including plastics, but alum­ Anderson (Sept., 1973) as were the fric­ inum seemed to be least costly overall. tion factors. These values evolved from The corrosion problems associated with the data in Figure 32 of Kays &London aluminum in seawater seem possible to (1965). overcome (Godard, et al., 1967, and Anderson, Sept. 1973). Using eq. (4), and knowing there­ quired heat flux from Figure 2, Figures For simplicity, the design of the 5 and 6 can be drawn showing the require­ condenser and evaporator were taken to ments of the product U x Aht for varying be identical, as were the properties of condensing (evaporating) temperatures seawater at the condensing and evapora­ and for seawater exit temperatures. From ting temperatures. Figure 4 shows the Figure 5, Figure 7 can be drawn. Althougr variation in overall heat transfer co­ Figure 7 is drawn for a seawater exit efficient (U) and the friction factor temperature of 50°F and velocity of 4 ft/ (f) as a function of seawater velocity. sec, it shows the general trend, that U and f are defined by the following both condenser area and pumping power dro1 equations. to a minimum at a condensing temperature Q = U ~t (LMTD) ...... (4) of about 55°F. This curve stems from two separate forces. Initially, the increasir

39 100 60,000

0 80 M 50,000

0 QEVAP. en 3: nl 0 0 0) CD _J ~ 60 OcoNo. 40,000 -1 u ~ c w :E en

40 30,000

20 20,000 WARM SIDE TEMP= 73° F COLD SIDE TEMP= 47° F

~--~--~--~--~--~----~10,000 2 4 6 8 10 12 TEMPERATURE DIFFERENCE °F

FIGURE 2. NH3 Flow Rate and Heat Flux vs. Condensor-Evaporator Seawater Temperature Difference ·

40 11 .030 ALUMINUM I II I" -+.,.._­ ALCLAD 4 4

FIGURE 3. Condenser Cross Section Design

41 .009

300

.008 I X.. - I OLL ..,.. I N ::::> 200 1--C\J (1) I­ lL 0::: I I I ~ I ,.007 I 100 ----

1.0 2.0 3.0 4.0 5.0 VELOCITY FEET PER SECOND

FIGURE 4. Heat Transfer Coefficient and Friction Factor vs. Seawater Velocity 24,000

20,000

16,000

12,000

8,000

4,000

48 50 52 54 56 CONDENSOR EXIT TEMP.

FIGURE 5. UXAHT vs. Condensor Exit Temperature

43 24,000

20,000 TEVAP. )oF) 65 16,000 <(13 :::>~ 12,000

8,000

4,000 ..______._____.....____._____~___, 64 66 68 70 72 EVAPORATOR EXIT TEMP

FIGURE 6. .UXAHT vs. Evaporator Exit Temperature

44 \ 200 \ .10 (\J \ J­ LL \ 0 \ 0 \. 0 \ .... ., / ..._.. 150 / ::> a...... _..,/ J­ " __ / ::> " 0

J­ J­ <1: ~ 100 .05 <( (!) w ~

0:::: w a... EXIT TEMP= 50 F <( 50 w 0:::: SEAWATER VELOCITY = 4 FPS <(

51 53 CONDENSING TEMPERATURE °F

FIGURE 7. Pumping Power Requirements vs. Output Power for Varying Condensing Temperatures

45 condensing temperature i~creases the log­ the condenser must have a greater frontal rithmic mean temperature difference so area, to accomodate the greater water that the area decreases. However, at a­ flow, and thus the condenser depth must bove 55°F, the amount of heat rejected decrease, to have the same volume. This needed to produce one megawatt of power results in a broad, shallow condenser, increases so drastically (Figure 2), as which due to other plant considerations to more than cancel out the effect of the may not be practical. increasing LMTD. In the simplified anal­ ysis used, the 55° cond0nsing temperature Although this discussion deals mostly corresponds to a 65° evaporating tempera­ with the condenser, using the previous ture, with the exception that both the assumption, this work can be applied area and the pumping power would be about equally well to the evaporator, with the three percent higher for the evaporator. slight correction that the area and pump­ ing requirements will be about three per­ Figures 8-11, show the effect of in­ cent higher for that operation. creasing water velocity on the area and pumping power requirement of the conden­ ser for various Tcond· While the pumping CONCLUSIONS power goes up, for increasing velocity, the area goes down. The pumping power 1. The optimum condensing and evapora·· was calculated from equ~tion (5), assum­ ting temperatures, for the given site ing an 85% pump efficiency. Entering and location, using the assumptions in this leaving losses were ignored, as these are paper, is about 55°F and 65°F respective­ somewhat a function of actual plant lay­ ly. The actual optimum operating temp­ out. eratures may be somewhat different from these, as they are restricted by the Figures 8-11 also show that as the ammonia flow rate the plant can be condenser seawater exit temperature de­ economically designed for. creases, the pumping power and area also decrease. However, in accordance with 2. The optimum seawater velocity is a the equation, trade off between minimum heat exchanger size and minimum pumping power. Q = VH20PH20 C(Tc ex1...·~- Tc·1n ) ...... (6) 3. The seawater temperature change as the inlet-outlet water temperature de­ across the heat exchangers has a direct creases, the water flow rate must in­ bearing on the physical dimensions of crease to remove the same amount of ener­ the heat exchangers, and is thus inte­ gy. This is illustrated in Figures 12 and grally related to the whole design of 13. This in fact places a lower limit on the plant. the condenser seawater exit temperature, and an upper limit on the evaporator exit 4. The optimum heat exchanger design temperature, as at some point, the pumping consists of balancing the various heat losses, other than those at the heat ex­ exchanger operating characteristics changes, (ie, pipes, water distribution within the physical limitations of a etc.) will become excessive. Figure 14 Sea Solar Power Plant. shows another interesting effect of the lower seawater exit temperature, at the condenser. At the lowe~ exit temperatures,

46 300 0.15

I 1­w w I IJ._ SEAWATER EXIT w CONDENSING I 0::: TEMPERATURE <{ I 1­ :J :J 0 0.. (/) 1­ 200 \ I I 0.10 :J 0 0 0 I I 0 0:: 5 w XI I 3: 1- I 5 0 :J 0.. a... I ~ I 1­ 0::: :J w 0 I;' 0.. 1­ 0::: 1­ w <( !If 3: 3: 0 <{ 0.. (!) w 1.1 ~ 100 0.05 ~ 0::: 0.. w ~ 0.. :J //// 0.. <( w / /// 0::: <{ /// _..,.,/

CONDENSING TEMPERATURE -= 55° F

2 3 4 5 SEAWATER VELOCITY FEET PER SECOND

FIGURE· 8. Affects of Increased 'Jelocity on Pumping and Condensor Area Requirements

47 SEAWATER I EXIT I I TEMPERATURE I J­ w w lL I \/ / w 52 I I J­ 0::: . I ::::)

FIGURE 9. Affects of Increased Velocity on Pumping and Condensor Area Requirements

48 300 I .15

1­ I w SEAWATER w EXIT I LL. TEMPERATURE/ w a::

2 3 4 5 SEAWATER VELOCITY FEET PER SECOND

FIGURE 10. Affects of Increased Velocity on Pumping and Condensor Area Requirements

49 SEAWATER EXIT I 300 TEMPERATURE I .15 I ..... w 48/ w I..L ..... I :::> w 0.. 0::: I ..... <( :::> :::> 0 0 I ... (/) 200 .10 0::: 0 / w 0 ~ 0 0 0.. ... I ..... 0::: :::> w 0.. I 0.. J-­ :::> I 0::: 0 I w ..... ~ ..... / 0 <( / 0.. ~ <( 100 / .05' (.!) (.!) w z ::?; 0.. ~ 0::: :::::> w 0.. 0.. CONDENSING <( TEMPERATURE= 49° F w 0::: <(

2 3 4 5 SEAWATER VELOCITY FEET PER SECOND

FIGURE 11. Affects of Increased Velocity on Pumping and Condensor Area Requirements

50 800 r--T~-r----r----r-----r---., r­ 700 :::::> a.. r­ :::::> 0 600 r­ tr 3: <( (.!) 500 w ~ w0::: a.. 400 0 z 0u w 300 (f)

0::: w a.. 200 r- w w l.L u 100 55 ro u:::::> 0 47 49 51 53 55 CONDENSOR WATER EXIT TEMP °F

FIGURE 12. Seawater Flow Rate vs. Exit Temperature

51 r­ 700 ::::> 0... r­ ::::> 0 600 r- r­

0::: w 200 0... r­ w w LL 100 64 (.) (l) ::::> (.) 0~----~----~------~----~----~ 63 65 67 69 71 73 EVAPORATOR WATER EXIT TEMP. °F

FIGURE 13. Seawater Flow Rate vs. Exit Temperature

52 250 I 50 I

(\J .,_ I (") I..L 200 40 ~ I 0 fT1 .,_ I z .,_ (f) <( 0 I ::::0 ~ <( (.!) 150 I 30 r w fT1 ~ I z G)_, 0:: w I :c a..

<( 100 20 TJ w I _, 0:: <( I

_J I ~ / COND TEMP= 53 F z 50 0 //wATER VELOCITY = 4 FPS 10 0:: I..L /

48 49 50 51 52 EXIT TEMPERATURE °F

FIGURE 14. CondensGr Frontal Area and Length for Varying Exit Temperatures

53 REFERENCES

Anderson, J. Hilbert. 11 Heat Exchangers for Sea Solar Power Plants." Technical Report NSF/RANN/SE/GI-34979/TR/73/15. Sept, 1973.

Anderson, J. Hilbert. "Tur·oines for Sea Solar Power Plants" Proceedings ­ Solar Sea Power Plllnt Conference and Workshop. Proceedings, Carnegie­ Mellon University, Pittsburgh, Pennsylvania. June, 1973. Godard, Jepson, Bothwell &Kane. The Corrosion of Light Metals. New York: Wiley &Sons, 1967. Kays &London. Compact Heat Exchanger. McGraw Hill, 1965. Olson, Pugger, Shippen &Avery. "Preliminary Considerations for the Selection of a Working MediP.m for the Solar Sea Power Plant." Solar Sea Power Plant Conference and Workshop. Proceedings, Carnegie - Mellon University, Pittsburgh, Pennsylvania. June 1973.

Van Wylen - Sonntag. Fundamentals of Classical Thermodynamics. New York: Wiley &Sons, 1965. Welty, Wicks &Wilson. Fundamentals of Momentum Heat and Mass Transfer. New York: Wiley &Sons, 1969.

54 SEA SOLAR POWER PLANT - PLANT SIZING

by

Don Debok &Jim Leshuk

ABSTRACT

The size, weight, and internal power cold water pipe and hull were the primary requirements of a 25 megawatt, gross, sea weight considerations. The investigation solar power plant were investigated. The showed the plant to be fairly large in design plant selected was an underwater relation to its gross output, but within plant to act as a shore side electric state-of-the-art. The resultant config­ feeder. Equipment for plant operation uration is very adaptable to multiple was considered, and items of critical units or mating with other devices. size and weight were selected. The eva­ Plant power requirements for the various porator and condenser were investigated production and life support systems is as the primary space consideration. The investigated and compared to unit gross plant output.

55

SEA SOLAR POWER PLANT - PLANT SIZING

by

Don Debok &Jim Leshuk

INTRODUCTION Beyond the initial input data, deci­ Overall plant size of a Sea Solar sions more directly relating to size and Power Plant is one of the major questions weight were made.t These included: still to be answered in the minds of technical people. Before they will con­ 1. Intake pipes should be hinged at sider the idea to be of merit they must the plant to reduce the need for overly believe that it can produce reasonable thick pipe wall. power from a size conceivable to them. To this end the size, weight and intern­ 2. The design calls for general op­ al power requirements, of a 25 megawatt eration by 12 men, with the ability to (Net) plant were evaluated. support 24 men for periods of repairs. Estimated stay time for each crew is 21 To make this evaluation certain input days, rations will be allowed for 42 decisions were required. This input was days. considered to be the result of a separ­ ate decision making process, and includes 3. The capability for periodic sur­ decisions for: a submerged plant, ammon­ facing for routine supply purposes must ia as a working fluid, an Electrical be provided at zero or reduced power out­ Feeder Plant, and 25 megawatts net power. put. This down time will be 12 hours maximum. In evaluating the size of a submersi­ ble plant, it is important that overall 4. A majority of required maintenance weight also be determined. Plant volume will be performed on site. The minimum on must provide neutral buoyancy. Adjust­ site design time is five years. Routine able ballast must be sufficient to ab­ maintenance must be allowed for while the sorb weight variations in the plant. plant is operational. Major repairs will be by subsystem modular replacement.

57 The identification of systems neces­ 5. Space effective means of changing sary to plant operation was the first water direction step in actual sizing of the plant. These items were classified according to Calculations for total volume of the the manner in which they might effect the condenser and evaporator units were plant size and weight. Table 1 summar­ based on internal surface area per out­ izes this classification and estimates put megawatt (S.A.), required pumping the importance of each system within the power (MWp/MWg) and flow rate (Q) obtain­ classification (five being of greatest ed from data calculated by Dan Ladd in a importance). The major efforts were un­ preceeding report. To account for pump­ dertaken in the sizing uf the boiler, ing costs in both the evaporator and con­ condenser and cold water pi~e. A con­ denser, Q and S.A. must be increased by ceptual layout was made to estimate the weight of the plant hull and the ballast 2X MWp/MWg or, tanks. Other items were estimated from off the shelf equipment or from research New Surface Area (NSA) = information. (1 + 2 :P)SA . • • . . • (1) g PLANT VOLUME ESTIMATION and Gross Flow Rate (QG) = MW The estimation of total plant volume (1 + 2 MWP)Q. . . . . • • . (2) is important to the overall cost and g feasibility of a Sea Solar Power Plant. Then Total Heat Exchange Volume (THEV) It is also important in determining may be expressed as, plant layout and drag forces for mooring and anchoring. To determine overall THEV = NSA/48ft3/1000ft2SA .... (3) size, two groups of items were consider­ ed. 1) Those whose size varied with Since water occupies 44% of this volume, plant operating parameters; and 2) Those Total waterside Volume (TVW) = (.44)(THEV). of size that is relatively constant, Also, condenser length (L) may be expres­ being based on initial decisions. sed as,

Items whose size varjes are the boil­ L = TWV/QG/V = TWV/PAw er, condenser and water intake pipe. The size of the boiler and ~ondenser is where PAw = the project area of the a function of intake water temperature waterside of the heat exchanger. (Tin)· Water exit temperature (Texit), flow velocity (V), and ammonia condens­ From this, Total Projected Area (TPA) ing temperature (Tcond). Tin is estab­ = THEV/ L ...... ( 4) lished by site selection. In order to and Total Boiler Unit Volume (TV8) minimize total plant size a general lay­ = TPA(L + 25) ..... (5) out was selected. This arrangement, shown in Figures 1 and 2, was chosen for Similarly, the Condenser Unit Total its: Volume (TVc) may be expressed as, TVc

1. Streamlined shape 2. Adequate space for buoyancy 3. Optimum position of machinery space Figures 3, 4, 5 and 6 illustrate the 4. Ease of condenser and pump main­ effects of varying these parameters. tenance Selected final operating levels were:

58 J 0 I{) I & •.-1 Ul

+J § ,...., 0... ,....,

,....,

U-1 ~ ::::.J c.:J H !:.I..

,.______0-----~!'­

59 _.______-0______~1 (J) <(

I 0::: w (J) z w 0 z :s: (]) 0 •r-i u > § 1'­ ..--l ro c..

-~ b.O •r-i Vl (]) C:

~ -~ CIS ..--l c..

N 0::: ~ :;:, l9 w H­ _j t:I-. - 0 m

-lO Jt-~~~t... --~--1'- •I

60 14xl03 ~--~----~----~----~----~

!'()­ 1- 3 LL. 12xl0 -w ~ ::) _j 0 > 6 FPS 0:: w _j 3 - 10xl0 0 en ' 5 FPS

BOILING TEMPERATURE =63° F 3 8xl0 68° 70° 72° BOILER EXIT TEMPERATURE ( °F)

FIGURE 3. Boiler Volume vs Exit Temperature For 63° F Boiling Temperature

61 3 14 X I0 r------...------.r-----r------.------.

5 FPS

f()­ I­ 3 -LL 12x 10 w ~ ::) _j 0 > 0:: w _j 3 - lOx 10 0 en

BOILING TEMPERATURE = 65° F 3 8 X I 0 ,______..______._____~______._____, 68° 70° 72° BOILER EXIT TEMPERATURE (°F)

FIGURE 4. Boiler Volume vs Exit Temperature For 65° F Boiling Temperature

62 lL 0 1'0 l() w 5 FPS 0:: ::J 3 ~ 16x 10 0:: w ()_ ~ w I­ (..9 z (f)z w 0z .o 3 0 14x 10 ~ ...--.. t() I­ ...... LL . . w ~ ::J _J

§Z 3 (..9 12xl0 z CONDENSING (f)z TEMPERATURE= 53° F w 0z 0 0 48° .50° 52° CONDENSING EXIT TEMPERATURE (°F)

FIGURE 5. Condenser Volume vs Exit Temperature For 53° F Condensing Temperature

63 4 FPS 3 16x 10

!'()- ~ LL ...... 6 FPS w 3 ~ :::> 14x 10 _j 0 > 0::: w (f) z w 0 z 0 (.) 3 12x 10 CONDENSING TEMPERATURE = 55° F

48° 50° 52° CONDENSER EXIT TEMPERATURE (°F)

FIGURE 6. Condenser Volume vs Exit Temperature For 55° F Condensing Temperature

64 TABLE 1. PLANT SYSTEM CLASSIFICATION

I Added Added Added Area of Added Power Volwne Volwne Volwne Interest i Weight Requirement Added Neutral Added Only I Item Buoyancy Buoyancy Weight

Boiler 5 I i Condenser 5 ! ' I Turbine 'I 4 I I Generator 2 I 4 I ! I Transformers 1 ! 1 I' I I I Air Compressor 1 I 1 I Ammonia Pumps 4 3 Water Pumps 5 I 4 I Heating/Air Cond. 3 I 1 I I I Life Support 3 I 3 I Dewatering Equipment 1 I 1 I ' Communication Equip. 1 I 1 Emergency Escape 1 i I ' Fresh Water Production 3 3 Fresh Water Storage 3 Batteries 1 2 Living Space 3 4 I Hot Water Tank 2 1 I Tools/Spare Parts 3 Pressure Hull 4 Cold Water Pipe 5 I Fire Fighting Equip. 1 2 Control Station 3 Ballast Tanks 4 Anchor Hand. Equip. 2 Air Storage 2 Plant Hull 5 Ammonia Piping 4 Lighting 1

65 Bo1l1ng. . Temperature 65°F Boiler Water Exit Temperature 68°F Volgr = p + PL Vol . . . (8) Condensing Exit Temperature 55°F P cond Condensing Water Temperature 51°F where Flow Velocity Sfps P = Net power of the plant Vol d = Original condenser volume con This selection results in a plant of To obtain the new pipe diameter (Dgr) the dimensions shown in Figures 1 and 2. p + PL Q Total volume of this configuration is Qgr = p 1.18 X 106 ft3. and, D f4 Qgr]~ The sizing of the cold water pipe is = l TIV • . . . • . . . (9) dependent on the flow rate Q established by the operating parameters. The length To compare the costs, condenser vol­ is established by the site selection. ume was converted to weight per cubic The pipe diameter is dependent on the foot of condenser (C.C.) and pipe dia­ flow rate and flow velocity. The deci­ meter was converted to weight/foot dia­ sion on size requires balancing the need meter (P.C.). Since there is no fuel for smaller diameter to reduce drag and cost involved, the construction costs construction cost against the need for may be compared directly. Maintenance lower pumping cost. As indicated later and anchoring costs are considered small in this report, the pumping loss due to per pound of material. A detailed analy­ the density difference is tne major pipe sis of cost per pound of material fabri­ loss up to four feet per second. Beyond cated was not undertaken as it is intui­ this point frictional losses become in­ tive that condenser fabrication is con­ creasingly important. siderably more expensive. Figure 7 demonstrates the trend of the lowest The pipe may be sized to a minimum cost (P.C. + C.C.) for various velocities diameter by balancing the dollars saved and ratios of C.C./P.C. in construction by reducing the pipe size with dollars spent increasing con­ Actual sizing of water pumps was not denser size to provide ~dditional re­ undertaken. A set of propeller pumps quired pumping power. This analysis of this capability within the space requires a determinatio11 of the total allowed was considered within state-of­ power loss (PL) for the established flow the-art capabilities. rate for several velocities. Items fixed in size by initial condi­ fL l) v2~ Q PL = ( D + L:K + 2g .... (7) . tions were living quarters and machinery spaces. Fraser (1968) gives examples where and compilation of confined space situa­ f = friction factor tions. In general, the cases for con­ L = pipe length finement space for three weeks were D = pipe diameter space ship examples. Due to the repeated L:K = sum of the minor losses nature of the manning and desire for v = flow velocity crews' comfort. Chamberlain's (in Fraser, g acceleration of gravity 1968, p. 456) recommendation of 2000 ft3/ ~ = specific weight man was adopted. To allow additional Q = flow rate space for maintenance personnel, approxi­ mately 30,000 ft3 was allowed for living To obtain the new condenser volume re­ space. The author's (Debok) shipboard quired (Volgr), experience confirms that 30,000 ft3 is adequate for up to 24 individuals. This

66 ,, ,,' ' \ ' \ ' \ ' 0::: 0 CJ) z w w a.. 0 a.. z INCREASED 0 LJ... (.) 0 FLOW RATE LJ... 0 0 z 0 ~ z 0 ~ a.. 0 a.. 0::: w 0::: a.. w I­ a.. CJ) r­ 0 (f) (.) 0 (.)

2 FPS 15 FPS VELOCITY OF WATER IN COLD WATER PIPE

FfGURE 7. Construction Cost

67 space would include all berthing, mes­ be considered independently by virtue sing, recreation, food ~torage and san­ of its design), external machinery, ex­ itary spaces. ternal storage, structure, exostructure, ballast systems, and miscellaneous. In the initial layout the same space Miscellaneous items were those which it was allowed for living and machinery was felt contributed negligible amounts areas. Table 2 lists major machinery to the total weight and/or displacement. items and their volume. The allotment These included positioning controls, of 30,000 ft appears adequate but per­ communications interfacial systems, haps cramped. In general, added space and external maintenance systems. would be free volume converting adjust­ able buoyancy to fixed buoyancy. The relationship of these two does not ap­ HEAT EXCHANGERS pear critical to the design at this time. Using the aluminum heat exchanger design presented by Dan Ladd in a pre­ vious paper, a linear variation of PLANT WEIGHT ANALYSIS ammonia quality between state points, six mil thick aluminum, a 1.34:1 cor­ Accurate plant weight estimation is rugation ratio, and 1/4" spacing for especially critical for the Sea Solar both seawater and ammonia sides were Power Plant due to the requirement for assumed. On that basis, the weight of neutral buoyancy. The basic analysis the condenser including ammonia was approach here was similar to that for calculated at 23.79 lbm/ft 3 of heat ex­ volume estimation. Major.plant subsys­ changer, the weight of the evaporator at tems were identified as to their rel­ 23.94 lbm/ft3 of heat exchanger, and the ative importance and state of refinement displacement of both units at 0.560 ft 3 / with the most analytical effort being ft3 of heat exchanger. spent on those potenti&lly large systems not available off the shelf. Some iter­ For our 25 mw net output plant, con­ ative calculations were necessary, but denser heat exchanger volume was deter­ the system was, in general, proven mined to be 186,000 ft 3 and the boiler quite stable in this respect. Large volume to be 170,000 ft 3 . Thus the changes in mass and volume affected on­ total weight of the condenser is 4.43 x ly mooring and trim systems. These in 106 lbs with a displacement of 1.04 x turn, only impacted mass and volume es­ 105 ft3. The evaporator weight is 4.07 timates slightly. Ultimately, identi­ x 106 lbs with a displacement of 9.52 x fication of mass, material, and configu­ 10 4 ft 3 • ration will be of great value in the capital cost analysis of the prototype design. PRESSURE HULL

The constituent subsystems for which While significant contributors to weight and displacement estimates and weight, such as prime movers and distri­ calculations were to be performed were: bution and control systems, are con­ heat exchangers and protective shell, ceived to be housed in a pressure hull, ammonia boiler, life support hull, ser­ the most important contribution of the viceable machinery hull (which includes pressure hull to the weight analysis is the bulk of prime movers, auxilary in terms of displacement. This para­ pumps, switching, transformers, and meter in turn is influenced primarily controls), cold water pjpe (which can by human factor considerations, which

68 TABLE 2. PLANT MACHINERY SYSTEM VOLUMES

Item Volume Source

Turbine 700 ft 3 Anderson Standard Handbook for Mechanical Generator 2000 ft 3 Engineers estimate Fresh Water Storage 432 ft 3 Volume of 4000 gals

Fresh Water Production 35 ft 3 Personal observation (DeBok)

Life Support Equipment 200 ft 3 Personal observation (Arneson)

Ammonia Pump 500 ft 3 Estimate of 50 HP pump

Air Compressor 300 ft 3 Estimate of 25 HP air compressor

69 were researched for the ass1~ed 12 man except lead acid emergency power stor­ crew. Beyond this, other major studies age batteries. For a 1500 amp-hour were conducted of power, gas, food, and reserve, 240,000 lbs of batteries are water storage, generator and turbine required. sizing, life support equip~ent, and gen­ eral warehousing. The studies are arbi­ The propane turbines are small in trarily divided into two categories, comparison as only an eight foot dia­ those housed in the crew hull, and those meter turbine is required for 30 mw housed in the machinery hull. output. Thus if the weight of the batteries and generators are consider­ Crew Hull Interior: Major weights, ed to constitute the bulk of the weight packing factor, and volume requirements (approximately 90%), the weights of the of items contained in the crew hull are turbines and all other components can shown in Table 3. These values were safely be neglected. If the same size chosen primarily from ship :md submarine hull is picked for the machinery sphere outfitting references &nd experience. as the personnel hull (for purposes of standardization and economy), the same The largest impact on displacement displacement is achieved, 29,187 ft3 comes from living space considerations but the new weight is 1,209,400 lbs as for the work crew. Greatest contribu­ shown in Table 4. tors to weight are water and food storage. COLD WATER PIPE Total weight of the interior furnish­ ings are estimated at 144,300 lbs. A 22 Weight analysis of the cold water ft diameter hull was arbitrarily select­ pipe is perhaps the most important ed for the pressure hulL Allowing for single calculation. The determination the total internal volli~e of 28,658 ft 3, is simplified by the existence of pre­ this yields a length of 75.4 ft. Assum­ cedents, particular hydro-power pen­ ing an inch thick HY-80 hull with three stock design criterion. Nonetheless, inch atends and 10% additional for bulk­ some examination of the assumptions heads and decks (also serving as struc­ behind these criterion and some modifi­ tural reinforcement), a total displace­ cation of them for seawater service was ment of 29,187 ft3 and weight of 424,200 necessary. lbs is achieved for the personnel hull. Steel was assumed to be the best Machinery Hull: The machinery hull material for pipe construction from the contains all those comp0nents which need standpoint of economy, corrosion, fab­ only occasional attendance and life sup­ rication, strength and fouling. The port systems which might pr%ent a haz­ top joint was assumed to be flexible, ard or nuisance to the work crews. The thus eliminating bending stresses. primary contributors to vreight were con­ Fabrication was assumed to be an on­ sidered to be the generators, turbines, shore process with the plant towed to and lead-acid emergency power storage site. Weld efficiency of 90% and a batteries. design stress of 15,000 psi was assumed.

Generator information was obtained Stress conditions examined were from standard AC central power plant buckling under pressure differential, equipment. This resulted in a weight of both for new and corroded pipe. and 237,200 lbs, including the exciter. collapse from the structures own weight This weight is at least an order of mag­ while being fabricated on land, calcu­ nitude greater than any other component lated for the new pipe only, sincere­ moval from the water is not forseen. 70 TABLE 3. PERSONNEL HULL WEIGHT TABULATION

Weight Component Space Req't (ft3 ) (lbs)

Freshwater Production 35 6,000 Freshwater Storage 432 24,000 Living Space &Personnel Furn. 26,000 4,800 Hot Water Production &Storage 40 2,500 Refrigeration 300 15,000 Contaminant Control 196 2,000 Emergency Breathing Equipment 40 1,200 Carbon Dioxide Scrubbing 20 200 Oxygen Supplies &Gen. 125 7,000 Food Storage 120 72' 000 Food Preparation 600 6,000 Ventilation 300 400 Sanitary Facilities 400 2,000 Communications 10 200 Controls 40 1,000 Sub-total 28,658 144,300 Hull (Includes airlock &escape tube) 529 279,900 Total - Personnel Hull 29,187 424,200

71 TABLE 4. MACHINERY HULL WEIGHT TABULATION

Volume Weight Component (ft 3) (lbs)

Turbines (2, 40 kw each) * * 2 Generators (2, 40 kw each) 2,000 605 000 ( ) ' Auxiliary Pumps &Compressors * * Switch Gear * * Transformers (Local) * * Cooling System * * Piping * * Cabling * * Power Storage 750 240,000 Tools &Shop * * Warehousing * * Ballast Tank Compressor * * Ammonia-Boil-Off Tanks * * 1 X 1.1 2 Internal Totals 28,658 929,500 Hull (Includes Airlock &Escape Tube) 529 279,900

Total 29,187 1,209,400

1 Weight of all minor items assumed to be 10% of the total weight source. 2 Calculated hull internal volume, not the sum of component volumes.

72 The thickness dictated by the pressure displacement and 13.1 lbs to the differential criterion is quite small weight of the plant. (on the order of 0.5 inches) since maxi­ mum pressure differential from suction For the 45,120 ft2 of area of sur­ head created by the pumps is only about face computed (exclusive of heat ex­ three feet (approximately 1.5 psi). changer armor), the structure and exo­ This value is somewhat dependent on structure displaced 3760 ft 3 and pumping velocity. weighed 562,000 lbs.

Corrosion rates are about 10 mils per The heat exchanger armor was com­ year (mpy) on the inside and four mpy on puted using the same formula, but the the outside due to differing local water surface area is more sensitive to velocities inside and outside the pipe. plant siting parameters. For a 75 foot diameter and 42.8 foot high condenser, The thickness dictated for land con­ the armor displacement is 840 ft 3 and struction was calculated from methods weight is 126,000 lbs. For a 75 foot discussed by Sarcaria (1958). This diameter and 46.8 foot high evaporator, value was determined to be 1.55 inches. the displacement is 919 ft 3 and weight Thus, if the pipe were to corrode at 14 is 137,000 lbs. mpy, it would be 75 years before a pipe designed to this criterion would fail The total mass of structure and exo­ from the first criterion. structure constitutes roughly 5% of the weight of the plant and 7% of the Assuming a thickness of 1.55 inches, buoyancy. In light of this, if more an inside diameter of 50 feet, and a refined design information became length of 737 feet with the last 50 feet available, some additional time spent radiused into a bell shape (using a 50 on improving this estimate would be foot radius) to give the smooth entrance justified. assumed by power loss calculations, the displacement of the pipe would be 17,667 ft 3 and the weight would be 8,640,000 EXTERNAL EQUIPMENT lbs. Equipment mounted external to the pressure hulls was assumed to include STRUCTURE AND EXOSTRUCTURE pumps for moving the cool and warm water, storage of large spares not A rather simplistic approach was affected by seawater or pressure, and taken to the structure and exostructure oil filled transformers. containing the plant, tieing together sub-systems, and providing a £aired Five pumps, similar to Allis­ shape. Chalmers units designed for the city of Ottumwa water system, low head, high The total area of surface surround­ volume with fixed blades with enclosed ing the heat exchangers and pressure electric motors were located above the hulls was determined from the general evaporator heat exchanger. Five simi­ layout. One inch thick epoxy reinforced lar units were located above the con­ with 85% glass fibers was assumed to denser heat exchanger. The weight of constitute the exostructure, alon6 with the units used was 28,000 lbs each, 5% of this volume being aluminum struc­ with a displacement of 220 ft 3 each. tural members and fasteners. Using this formula, every square foot of external External storage was assumed to surface contributed .0876 ft 3 to the occupy 5000 ft 3 and have an empty weight of 30,000 lbs.

73 Oil filled transformers were assumed this table does not include the volume to be placed in compensated pressure occupied by the cold water discharge housings outside the plant. Without flow beyond the pumps, and free volume more complete data on power distribu­ areas within the plant superstructure tion, the transformers were assumed to not associated with any particular displace 10,000 ft3 and weigh 640,000 component. Adding these neutral water lbs. To minimize the impact of this volumes to the Table 6 displacement 5 large unknown on the ba~ance of the total yields 10.852 x 10 ft 3 . Thus plant, they were assumed to be construc­ 2.7 x 105 ft3 remains as ballast control ted to be neutrally buoyant. This esti­ area. The total buoyancy of this bal­ mate could use considerable refinement last area is 17.3 x 106 lbs which is if an electrical distribution design was more than adequate for plant buoyancy included in the prototype report. maintenance and for surfacing and freeboard requirements.

MISCELLANEOUS ITEMS PARASITE POWER Those subsystems identified but not quantified for purposes of the weight An accurate determination of para­ estimate include items which are either sitic power consumption is essential of such small magnitude as to represent to the sizing and feasibility study of insignificant numbers in the total dis­ an SSPP. It was excessive power con­ placement and/or weight. These are sumption by auxiliary systems, particu­ listed in Table 5 along with their ex­ larly cold water pumping, that contri­ pected order of magnitude. A note on buted in part to the failure of the the mooring lines is in order. It was Claude Cuban and Abidjan thermal power determined that the forces encountered extraction plants. could be handled with nylon line of practical diameters. Njlon line is The percentage of pumping power re­ nearly neutrally buoyant, thus it would quired to gross output is extremely not enter into an iterative process on dependent on temperature. A tempera­ weight and displacement calculations, ture difference drop of a few degrees despite large quantities needed in will greatly increase the parasitic mooring. power. This makes quantification of these losses most important. Some of the other losses are relatively fixed, WEIGIIT SUMMARY such as hotel load for a manned plant. Thus, while a plant can be designed to Totals for the weight analysis for provide a certain gross output, regu­ the various components are shown in lation of the variable parasitic power Table 6. The net weight of the plant is losses is essential to determine the 11.27 x 10 6 lbs and that of the cold economic feasibility of such a plant. water pipe is 8.64 x 106 lbs for a total Figure 8 shows the justifiable invest­ weight of the entire st:mctnre of 19.91 ment per kilowatt (net output) in a x 106llbs. Displacemerrt of the various fuel-free plant for various prices of systems is also shown. However, these fuel for fuel fired plants. figures ignore the seawater sides of all components. Thus the actual volume of This section will identify and typ­ the condenser is 22.7 x 104 ft3 with ify, if not quantify, these parasitic 17.3 x 10 4 ft3 being water filled and losses for the prototype SSPP design. neutrally buoyant. This is also true for the evaporator and pumps. Further, While water pumping is the most significant loss, other losses to be

74 1800 r------r-----r------....,..---r----.

..... :::::> 1600 a...... :::::> 0 1400 ..... w z ~ 1200 ~ 0::: w a.. 1000 -f:FT ...... z w ~ 800 t­ (f) w > z 600 ..... z

0 20 40 60 80 100 ANNUAL LOAD FACTOR

FIGURE 8. Investment in Fuel Free Plant Equated to Energy and Investment Costs in a 300 MW (Trojan = llOO MW) Fuel Fired Plant for Various Load Factors and Energy Costs TABLE 5. MISCELLANEOUS ITEM WEIGHT TABULATION

Item Displacement Weight (ft3) (lbs)

Position Control * * Thrusters 10 3 10 5 Lines * * Communications Buoy * * Diver Support 103 104

* Does not affect net buoyancy.

TABLE 6. WEIGHT SUMMARY

Weight Displacement Buoyancy Net Buoyancy Component 3 (lbs x 106) (ft X 10 4 ) (lbs) (lbs)

Condenser 4.43 10.40 Condenser Armor 0.13 0.08 Evaporator 4.07 9.52 Evaporator Armor 0.14 0.09 Personnel Hull 0.42 2.92 Machinery Hull 1. 21 2.92 Evaporator Pumps 0.14 1. 25 Condenser Pumps 0.14 1.77 External Storage 0.03 0.50 Transformers Neg Neg Mooring Cables Neg Neg Structure &Exostructure 0.56 0.37

Plant Subtotals 11.27 29.82 19.08 X 106 +7.81 X 106

Coldwater Pipe 8.64 1.77 1.13 X 106 -7.51 X 106

Totals 19.91 31.59 20.22 X 106 +0.31 X 106

1. Control surfaces and thrusters not included. 2. For buoyancy computation, p = 64 lbs/ft3.

76 identified and investigated are those The pumping load was further broken associated with bringing warm surface down into constituent parts to yield a water to depth, circulating the working general expression for pumping work: fluid, disposing of plant discharge, ~nd cooling of the various pieces of machln­ W = Qg (pliH + lip H). • • • . . • (9) ery. where W Work (watts) Other, minor loads that at least de­ Flow (L 3/T) serve order of magnitude consideration Q p Density (M/L 3 ) are those associated with life support = H = Headloss (L) system, hotel load, control of m~chi~ery, mooring, positioning, and commun1cat1on. DENSITY DIFFERENCE LOSSES Water Pumping Power: The preliminary concept locates the plant in a major current, thereby eliminating the need Perhaps the least understood and for pumping warm water to the boiler most significant underwater transport side heat exchanger, and discharge from loss is that encountered in overcoming density differences. In most engineer­ both heat exchangers. However, the current decreases with increasing depth ing applications these losses ar~ s~all and the equivalent head from density (though the analagous case for a1r 1s the crux of draft and chimney calcula­ differential necessitates the expendi­ tions) and are neglected. However, at ture of pumping power to bring the cool low velocities and heads, they can be benthic water to the condensers. While significant. Not suprisingly, they several pumping schemes are feasible, a variable pitch propeller type pump is have been neglected in some other stu­ the plan design pump as it is a low dies of SSPP cold water pumping studies, thus casting dispersion on the credibil­ head, high volume, low maintenance pump. ity of those results. Multiple fixed pitch pumps would be a suitable alternate. These pumps will The concept is probably most easily be located at the downstream end of the cold water flow loop. Cavitation was visualized if the pumping system is thought to act across two fluids of not seen as a problem with this atypical nifferent density in a vertically stra­ arrangement, since the relatively great tified situation rather than over a depth of the plant provides a net posi­ density gradient (see Figure 9). This tive suction head of approximately six can be validly assumed since work is a atmospheres, far in excess of the total line integral, dependent only on the pressure head developed in such a pu~p­ ing operation. For purposes of provld­ end states, and independent of path. Thus, no matter what shape the pipe may ing design temperatures to the heat ex­ take, or whatever density gradient changer, the cold water pipe was assumed might exist, the density difference to extend 730 ft below the plant to an absolute depth of 1,000 ft. It has been pumping head remains constant for_con­ discussed that the pipe would hang near­ stant conditions of state at the 1nlet ly vertically, and that it would possess and outlet. a well-rounded entrance, a trash rack to For the prototype SSPP design the keep out debris, and possess one 90% conditions at the inlet and outlet are: bend, with no valving or control other than the ability to regulate pump speed Depth Temp. Salinity and pitch. Outlet 275 ft 73.0°F 36.45% I:nlet 1000 ft 47.0°F 34.98%

77 THESE THREE SYSTEMS ARE EQUIVALENT IN THE AMOUNT OF DENSITY DIFFERENTIAL PUMP WORK TO BE DONE FOR THE SAME END CONDITIONS AND FLOW RATES.

1 1 l -~ ­ ' SG= 1.02510 r ~ SG= 1.02510 SG=I.02510 ···-··· //'L-.,JASG :.:: ·~ l~f-::~...... :·.-.;.".· -~.·: r:.;...... ].: "-! ~:: •· 00 r:· ; ~f} ? ::·:: ::~ ( :{ ·:.- .: :.· .~ ::.· .·., ~!~: .~ ~. ·: r:. :~ .:::· :.: (TWO LAYER :::. ·~' +~ SYSTEM) ...... £·:· .:

rr:.:.·· il... 1{~:: . : tr. :.~ PUMP~.:) PUMP DENSITY . DENSITY DENSITY SG=I.02712 SG = 1.02712 SG =1.02712

FIGURE 9. Concept-Denisty Differential Pumping Work Using a nomograph published by the This was done in Figure 11 for a Navy Hydrographic Office (Figure 10), geometry described by these values can be related to specific gravity by determining 0t = (S.G.-1) x Pipe Length = 730 feet 1,000, and ultimately to density. The Ke, loss coefficient for entrance = .o3F corresponding specific gravities at in­ Ks, loss coefficient for screen= 1.10E let and outlet are 1.02712 and 1.02510 Kb, loss coefficient for 90° vaned elbow respectively for a density difference = 0.60° of 0.000411 slug/ft3. Pipe roughness was assumed to be con­ stant over varying diameter. At three As seen from the pump work equation, feet per second and below, fouling with this density differential and vertical barnacles 1/4" high was assumed. At distance can be related to gravity head velocities of three and four feet per at constant density. This equivalent second, friction factors were computed gravity head is 1.523 ft of seawater for a roughness corresponding to asphalt (S.G.= 1.0256). covered rolled steel plate.

Using this in the work equation, a The units of the abcissa of Figure 10 specific loss of 142.4 watts/ft3/sec, are expressed in watts per cubic foot or 1.07 mw, results for a 7500 cfs cold per second, thus facilitating the power water flow rate. loss computation for any flow rate. The ordinate is pipe diameter in feet. If a flow rate and velocity is assumed, the VELOCITY RELATED LOSSES IN PIPE diameter must be calculated by: Head loss in pumping the cold water D =J ~~v ...... (11) exclusive of gravity effects and heat exchanger losses can be expressed as Similarly, for a given flow and dia­ follows. meter, velocity can be determined by:

Velocity v - 4Q Minor Friction - nn0 2 . (12) Head Loss Loss v2 fL v2 where n number of equal diameter pipes H = L:h= zk v2 + 2g + 2g o 2g · · (lO) used. where Several interesting trends can be v = Fluid velocity surmised from Figure 11. It can be seen g = Acceleration of gravity from the two plots for three feet per k = Minor loss coefficient for second velocity that surface roughness various deviations from regular has a minor effect on pumping losses, conveyance particularly at the larger diameters. f = Friction factor This is because wall friction is a very L Pipe length and, small contributor to total losses. By D = Pipe diameter this same token, additional pipe length would increase losses only very slightly. Thus, a portion of the pumping load For the range of velocities and diameters can be expressed as a series of terms that are considered, in no case did vel­ which are a function of flow velocity ocity dependent losses approach the den­ and geometry, and which are proportion­ sity differential losses by more than al to the square of velocity for a 60%. given geometry. By establishing the desired {low and pipe geometry, these Bearing in mind that optimizing a losses can be described as a function sub-system independently of the whole of pipe diameter. 79 S%o (J

MATCHING SYMBOLS: a)-O d)-0 35.0 b)- 6 e)- \7 c)- o

FIGURE 10. Nomograph for the Determination of Density from Salinity and Temperature of Sea Water (U.S. Navy Hydrographic Office, H.O. 007)

80 100~~~~~~~------~--~~--~~~~ ~ 80 V= 4 FPS, € =.0004 0 ~(SMOOTH, COATED) uw 60 (/) V=3FPS, €=.02 yt/(BADLY ENCRUSTED) 0:: 40 w Q_ /;;----===== 1­ V= 2 FPS, € =. 0004 0 (SMOOTH, COATED) f2 20 u en :::> u 10 0:: ~ w 8 V=2 FPS, €=.02 Q_ (/) 6 I­ I­

(.9 z Q_ ~ :::> Q_ 4 6­ 8 10 20 40 60 80 100 DIAMETER IN FEET

FIGURE 11. Pumping Power vs Pipe Diameter for Various Velocities &Friction Factors

81 can detract from the overall efficiency, of the design from a functional stand­ an optimal diameter can be determined poing, a constant loss of 13% of gross based on Penstock Design Economics power was assumed in the design of both (Sarkaria, 1958). This was computed boiler and condenser side of the heat for a flow rate of 7500 cfs to be 102' exchanger, this value having been de­ and a corresponding velocity of .92 termined from optimization of condenser feet per second, yielding a loss of 3.3 sizing. Thus this same value will be watts/cfs or 25 kw total velocity-re­ used for the calculation of total para­ lated loss. The same flow divided over sitic power. three pipes results in a di&meter of 63. 7', a velocity of . 79 fps, and a loss of 1.5 watts/cfs. WORKING FLUID PUMPING LOAD

Using a Bureau of Reclamation (1973) Working fluid pumping load is an in­ formula, the optimal velocity for a trinsic quantity determined by the Penstock operating under the same con­ thermodynamic cycle chosen for the ditions would be 1.22 fps with a cor­ plant. Only losses and pump ineffi­ responding diameter for a single pipe ciencies will alter this figure upward of 88.3 feet and a specific loss of 5.5 from the minimum value determined by watts/cfs. the cycle. In our prototype design, ammonia was chosen as the working fluid Using five fps and a 50' diameter, between temperature limits of 55°F and the friction losses are roughly 100 65°F. The heat exchangers, deemed the watts/cfs, or . 75 mw for 7500 cfs. most critical element of our design, were designed about these and other Efficiencies in pumps of the size we existing conditions. are dealing with approach 100%. How­ ever, if one wanted to take a more con­ The pumping load was computed in the servative position, the above power report by Dan Ladd on cycle and working ratings could be divided by .9 thus fluid considerations, and can be repre­ yielding a more cautious estimate. · sented by the work in going from state three to state four on a temperature entropy diagram. This portion of the HEAT EXCHANGER PUMPING LOSSES pumping power can also be determined by using the formula (Hawkins, 1967): In the design of the plant, it was determined that the amb1ent water temp­ ~ == Vllp ...... (13) erature at the main plant was adequate M to run the ammonia boiler, thus elimi­ where nating the need for warm water piping. p = Power Further assuming selection of a site to v = Specific volume provide a steady current to move warm lip Pressure at state four minus and discharged water to and from the . pressure at state three heat exchangers, discha~ge piping is M = Mass flow rate of working eliminated. All that remains is the fluid loss occuring from moving the warm water across the heat e:Y.changers at the For the temperature limits of 65° and desired flow rate. This same loss must 55° respectively be added to the cold water pumping loss. P4 = 117.8 psi p3 = 98.1 Since the heat exchangers were deter­ mined to be the most critical element

82 Therefore, PL = 1.05*(1-n)*P n . . . . (14) 6p = 19.7 psi and, V = 38.5 ft /lb or, .55 mwatts for a 40 mw unit. Thus, The turbine selection criteria used w • = 140.3 Btu/lb of working by Anderson (June, 1973) suggests an M fluid. efficiency of .85 is possible for For a working fluid flow rate of ammonia. Approaching this in the same 2000 lb/sec, this portion of the pump­ manner as equation 14, the parasitic ing work is .2806 mwatts. load of the turbine is (1.05)(1-n)P/n or 7.41 mw for a 40 mw gross output. Since the working fluid flow path is simple and large diameter conduits do not represent a significant heat loss HOTEL POWER LOAD problem because of the low temperature differential, it is assumed that fric­ Providing power for life support and tion losses in this system are negli­ comfort of a manned crew represents a gible. A more conservative approach parasitic load on the plant output. would be to assume a reasonable conduit These demands, along with an investiga­ diameters and calculate friction head tion of the need for air conditioning for crew and serviceable machinery areas at: v2 are summarized below. (5 to 10) x 2g . A pump efficiency of .90 in this flow Relying heavily on data available for rate and pressure range would be appro­ nuclear and research submarine life priate. support and hotel loads, the breakdown shown in Table 7 was achieved. Total parasitic load for these functions is PRIME MOVER about .15 mw.

Another area which falls into the An investigation of the need for air category of parasitic power is that of conditioning/heating showed that because prime mover efficiency. Any prime of the range of water temperatures near­ mover efficiency not only represents a by being at, or slightly below room loss of potential work from the thermo­ temperature, the need for internal dynamic cycle, but these losses usually temperature control is minimized. The manifest themselves as waste heat, for analysis concludes that the crew area which pumping or blower power must at with a three inch thick steel and 1/4" times be expended to remove, as in the thick fibreglass will need heating of case of turbine and generator bearings, approximately 3300 Btu/hr, but that the and generator windings. machinery area will need substantially more cooling (434,260 Btu/hr) for the For purposes of this study, a stand­ same insulation. By eliminating the ard 40 mw generator was selected (Mark, machinery area insulation, this value 1967). The efficiency of this unit is ca~ be reduced to a net loss. It is 98.7. Since a heat sink is readily then practical to assume that an inter­ available (the ocean), coolant pumping mediate amount of insulation would give losses were considered to be small (5% a slight net heat surplus from the of the heat load). Thus the parasitic machinery area, which could be used to load of the generator is given by: heat the crew quarters. More detail on this budget would be needed for complete

83 TABLE 7. PARASITIC POWER ASSOCIATED WITH MANNED PLANT

Item Load (kw)

Life Support 02 Generator 2

C02 Scrubber 1 CO &H Burner 1 Gas Analyzer Compressor Pumps 10 Ventilation 8

Sub total 22 kw

Hotel Distillation, Personal Water 60 Hot Water Heating 16

Cooking &~ood Preparation 4 Lighting 3 Communications Receivers 5 Refrigeration 10 Laundry &Dishwashing 20 Waste Water Pumping 1

Sub total 119 kw

Heating/Cooling Heat Pump 2

Total 143 kw

84 system design. A value of heat input A summary of parasitic power require­ pumping has been included in the hotel/ ments is shown in Table 9. It will be life support power load summary. noted that approximately 45% of gross plant power is required for internal An actual need for air-conditioning plant operation and only 55% is avail­ in the crew area may occur while the able for export power. plant is at or near the surface in warmer water. While this would not affect parasitic power inasmuch as the CONCLUSIONS plant is not operable under these con­ ditions, provision should be made for 1. The 25mw plant considered in this the installation of air-conditioning to paper is viewed purely as a protot;~e be powered from shore or support ship. size plant. Final operating plant design Further, if computer or automation would either be significantly larger, or equipment is included, the temperature be based on clusters of plant modules and humidity must be more closely con­ based on a 25mw to 50mw output for each trolled. It is apparent that, in any module. This study has established that event, some dehumidification scheme the physical size of a 25mw module is not should be included. excessive but is well within reasonable limits for the magnitude of physical facility required. MISCELLANEOUS PARASITIC POWER 2. The selected plant design appears The remaining items which were iden­ ideally suited for incorporation into the tified as contributing to parasitic module concept. Further, the design pro­ power, but which were considered out of notes on station stability end minimiza­ scope of the study by virtue of their tion of plant volume. apparent relative insignificance or of their dependence on arbitrary out-of­ 3. While the cold water pipe is negative­ scope assumptions, are enumerated in ly buoyant, the main plant structure pos­ Table 8. Also included are estimates sesses sufficient free space for conver­ of their order of magnitude and comments sion to ballast tanks to allow adequate on the areas of investigation needed to buoyance for on station maintenance and refine the estimate, with the exception for surfacing. of transmission transformer losses, which depend heavily on the socio-eco­ 4. For a 25mw net output, approximately nomic-political decision. As to the form 45mw gross output will be required. 45% of electrical power produced and the of this gross will be needed for plant in­ distribution system, most of these losses ternal operation, with 55% available as can be proven minor and easily quantified export power. While a direct comparison once the subsystems are designed. The is not entirely appropriate as this system other losses are assumed to total to requires no purchased energy input, a very less than one percent of the gross out­ favorable comparison can be made between put of the plant. these figures and either fossile or nucleaJ power plants having plant efficiencies of approximately 33% and 40% respectively.

85 TABLE 8. MISCELLANEOUS PARASITIC POWER CONTRIBUTIONS

Power Component Consumption Comments (watts)

Communications

Radio Transmitter/Telephone 10 2 - 104 Intermittent Warning Lights/Sirens 10 3 - 10 4 Intermittent

Position Control Winches 0 - 105 Intermittent Thrusters 0 - 106 See Mooring Section, Intermittent Ballast Pumps 104 - 10 5 Intermittent Control Surfaces 102 - 104 Intermittent

Plant Control

Switch Gear 10 2 - 104 Valves 10 3 - 10 5 Computer 104 - 10 5 Transformer Losses 10 2 - 106 Dictated by Desired Power Output Form

86 TABLE 9. PARASITIC POWER REQUIREMENTS SUMMARY

Power Requirement Component (kw)

Cold Water Pumping (density) 984 For 6900 cfs @ 4fps (friction) 690

Evaporator and Condenser Pumping 12,400 (26% of gross output) 1

Working Fluid Pumping 281 (for 2,000 lbs/sec)

Total Pumping Power Required 14,355

Pump Inefficiencies 1,608 (1-.9/.9) (l.Ol)Pp

Generator Inefficiencies 685 (1.3% of gross output)

Turbine Inefficiencies 4,500 (10% of gross output)

Hotel Load 1,213

Total Parasitic Power Required 21,291

1 For 25mw net output.

87 REFERENCES

Allis-Chalmers Co. Turbines and Auxilaries. (Advertising Brochure). Allis-Chalmers Co. 1950.

Ambs, L.L. and J. Marshall. "Ocean Thermal Difference Power Plant Turbine Design", Technical Report: NSF/RANIV/SE/GJ-3497/Tl2/73/17. University of Massachusetts, 1973.

Anderson, J.H. "Turbirre Design: Sea Solar Plants", Technic

Charlier, R.H. "Harnessing the Energies of the Ocean", Marine _Technology Soci~![_Jou~al. 3(2): 13-32, May, 1969.

Hawkins, G.A., and J.B. Jones Jr., Engin~~ri~_g Thermodynamics. New York: Wiley and Sons, 1967.

Hodgson, C. W. "Modern Thermal Station Design'', Construction Engineering. September, 1963.

King, E.F. and H.W. King. Hardbook of_Ijydraul!_cs. New York: McGraw Hill Book Co. 1963.

Ley, W. _En~ine~r's Dreams. New York: Wiley and Sons, 1954.

Mark, L.S., ed. Mechnir.:.al Engineers Handbook. New York: McGraw Hill Book Co. 1967.

Sarkaria, G.S. "Economical Diameter For Penstocks", Water Power. 10(9): 352-356, September, 1958.

Streeter, V.L. Fluid Mechanics. New York: McGraw Hill Book Co. 1966.

U.S. Bureau of Reclamation. Design of Small_Dams. Washington D.C.: U.S. Government Printing Office, 1973.

88 SEA SOLAR POWER PLANT - MOORING AND ANCHORING SYSTEM DESIGN

by

Jim Wright, Blaine Hafen, &Byungho Choi

ABSTRACT

General state-of-the-art design cri­ Wide scatter still exists in such funda­ terion and methods of approach in se­ mental aspects as the values of Co and lecting a mooring and anchoring system CI as used in the Morrison equation. for the Sea Solar Power Plant are dis­ Thus mooring system design is still an cussed. Static and dynamic systems are experimental science and a conservative compared and evaluated. For this evalu­ design can only be obtained for any ation a complete description of load and given conditions. Finally, potential force source and type from the ocean en­ anchoring systems are discussed and vironment and the plants dynamic re­ evaluated. sponse to these forces is required.

89

SEA SOLAR PO\ffiR PLANT - MOORING AND ANCHORING SYSTEM DESIGN

by

Jim Wright, Blaine Hafen, &Byungho Choi

INTRODUCTION

While a Sea Solar Power Plant cannot of the plant, the depth of the water on function without the successful operation site, and to the current velocity in of all subsystems, certainly no single the Florida current. subsystem is any more critical than the mooring and anchoring system. This cri­ 3. The current state-of-the-art of ticality of the mooring and anchoring mooring and anchoring system design is system arises from three sources, with such that definite solution of the con­ each greatly magnifying the effects of ditions described in 1 and 2 for a spe­ the other two. These are: cific system stress requirement is not possible. Such basic parameters as Co 1. The great diversity of source and · and c1 for the Morrison equation have types of loads to be absorbed by the sys­ not yet been assigned definite values tem. Wind, wave, and current forces in­ so that wide scatter still exists over cluding steady state and transitory ele­ their potential ranges. ments and the plants' dynamic response to these forces will form a very complex This paper will define and analyze and diverse integrated system of loads the expected load forces on the plant for the mooring and anchoring system to and discuss potential mooring and an­ counter. choring systems for use with the plant. Certainly more research is required 2. The magnitude of these forces will before the mooring and anchoring system be far greater than those encountered by requirements can be fully defined. existing mooring and anchoring systems. This magnitude is due to the large size

91 LOAD SOURCES AND CONDITIONS subsequent determination of forces was generated from averaging seasonal val­ Currents: Surface currents will af­ ues at depths and approximating these fect the drift and stabilization of the by polygons. Figure 1 shows that the Sea Solar Power Plant (SSPP) when in a velocity of the current has dropped to surfaced condition. Subsurface currents approximately 2.10 feet per second at a affect the stabilization of the struc­ depth of 200 feet. Therefore, in a ture as well as the anchorage. Currents submerged condition the SSPP will still result in the following load conditions: have considerable current forces to 1) a dr~g force which is proportional to overcome. The forces due to currents the square of the velocity, and 2) an are mainly those caused by drag, and a interference with mooring lines through drag coefficient and design current the action of vertical and ~orizontal must be selected. It should also be shear. noted that the vector sum of the steady current and wave particle velocity Two major types of currents must be should be considered in a swift current considered, near-sea-floor turbidity such as the Florida Current. currents and major oceanic currents. Near-sea-floor turbidity currents caused Winds: Much of the information on by submarine landslides are intermittent wind measurements has been based on at best but have caused the fastest cur­ data gathered over land areas. Thus rents know with velocities of almost 50 data for wind description over water is knots on the sea floor. Th~ir infre­ generally lacking and the design wind quent occurrence obviates their use in speed must be selected on the basis of design criteria, although an on-site a statistical evaluation of area records. survey should include ~' analysis of Methods such as the Beard Method (Beard, this type of disturbance. There is 1952) and Gumbel's Standard Skewed Dis­ little known about how far above the sea tribution (Gumbel, 1958) can be applied floor these currents act; however, the to the problem of obtaining design wind interaction between the cold water in­ speed. There are several methods avail­ take pipe and this current is considered able to proceed further and correlate improbable as over 600 ft. separates the wind speed and fetch with wave heights. cold water intake and the ocean floor. Bretschneider (1959) was one of the first to apply a correlation method for Major ocean currents related to den­ design purposes. His dimensional analy­ sity distribution can reach speeds of sis method provided the basis for some greater than four knots (Ippen, 1966). of the more complicated and restrictive A velocity profile for the Florida Cur­ methods also used today. Other methods rent is shown in Figure l. Open-ocean are discussed in Ippen (1966). Falvey streams do not tend to flow along con­ (1974) recently has devised a correla­ stant paths unless confined, as in the tion method and compared his results case of the Florida Current. Thus the with standard wind casting curves. His complexity of load calculation is some­ method predicts values of significant what simplified due to the basically wave heights accurately by replacing steady state nature of the Florida Cur­ complex mathematical formulations with rent. Average net transport for this empirical formulas. current is 26 x 106 m3 per second. Wind loads however will not be consi­ Currents may here be deflned as fluid dered as critical for the SSPP as the velocities which may be treated analyti­ plant is submerged approximately 98% of cally as steady-state phenomena. There­ the time. It is assumed that when sur­ fore, the design profile used in the faced, the structure will exhibit 20

92 80°03'W 0 25° 53.5' N 79°37 1 1600 6. w 25° 52.5'N 79°50'W 0 25°53' N

~ POLYGON APPROX. 2000 TO CURRENT PROFILE 2200==~~--~--~--~--~--~----~ 0 2 3 4 5 6 7 CURRENT FEET I SECOND

FIGURE 1. Florida Current Velocity Profile

93 feet of freeboard and eA~erience a maxi­ The range of usefulness of all wave mum wind of 20 knots since the surfacing theories cannot be precisely determined. capability allows optimization of wind One suggested criterion would be to use and wave conditions. Myers (1969) indi­ the breaking index curve (h/T2 vs. cates procedures used in calculating HB/T 2) as by Weigly (1971), or by Myers wind forces, where the most difficult (1969) who includes a comparison of sin­ determinations as far &s engineering usoidal, cnoidal, and solitary wave judgment is concerned, revolves about theories. The decision to use first­ the values of CL and Co, coefficients of order or higher order will depend on lift and drag. Occasionally dynamic ef­ the problem to be studied and the magni­ fects must be considered. Turbulent tude of the design wave height. Higher eddies or gusts of wind having frequen­ order theories generally predict higher cies near the natural frequency of the velocities with very little change in structure can excite resonance. acceleration (Ippen, 1966). Thus a higher order theory should be chosen Wave: In simplified form, the forces where the drag force is important. on a structure in the marine environment Prior to describing the forces on a can be classified as forces due to waves solid body it is assumed that the struc­ and forces due to currents. In deter­ tural dimension is small with respect mining wave forces on a structure, the to the wave length so that its presence following steps are noted: 1) selection is not detectable in terms of wave and of a design wave height and period; 2) current motion a short distance away. selection of an appropriate wave theory A large structure will significantly to compute water particle velocities and modify the wave and current fields rela­ acceleration; and 3) selection of drag tively far from the structure. and inertia coefficients from experimen­ tation or experience which may be applied There exist two types of forces in to a suitable wave-force equation. the direction of the wave. One is a drag force which is due to the relative The determination of a design wave is velocities between the structure and the greatly dependent on a statistical ap­ fluid. It requires real fluid effects proach as is the determ~nation of a use­ (friction, vorticity, shear, turbulence) ful wave theory. Beginning with Gerst­ and produces a net shear and pressure ner's first wave theory in 1802, many force on the structure. The other is an approaches have since been proposed inertia force which is due to relative (Bascom, 1964). As a first approxima­ accelerations between the structure and tion to the wave forces on the SSPP, the the fluid. It can exist in an ideal as Airy wave theory found iirectly from the well as a real fluid and potential flow linearized hydrodynamic equations will theory is satisfactory for its computa­ be used. Here the amplitude is consi­ tion. It produces a net pressure force dered half the wave hei~ht. Hence, on a body and is associated with unsteady flows relative to the body or fluid. The drag force may be divided further into ag cosh k(h+z) ¢ = ;- cosh kh cos(kx-0t) ...... (1) skin drag (due to flow parallel to the surface) given by: ulul -~ = agk cosh k (h+z) . (k _0 t) (2) = CfpA -- .•.•••••••.•.•. (4) u = 3x 0 cosh kh Sln x · Fo s 2 where 3u cosh k(h+z) cf = skin friction coefficient 3t = -agk cosh kh cos(kx-0t) ...... (3) (derived from boundary layer theory)

94 A= area parallel to flow, the effect of a solid boundary or air­ and, U = approach velocity. sea interface. As an example lift be­ and into form drag (due to flow perpen­ comes important for a cylinder where dicular to surface) given by: e/D < 1.5. In other words, within certain limits, as the distance between ulul an object and a solid boundary decreases Fo = CoAp -2- ...... (5) the coefficient of lift, CL, in where c = drag coefficient which is a 0 FL-_ PCLD -u!ul--- .•...•.•.•.••.•.• (7) function of the shape of the 2 body, increases (Yamamoto, 1973). This may and, A = frontal area. also be compared with work by Ippen (1966). Since Cf is approximately 0.01, the con­ tribution of skin drag to total drag is In summary, the following parameters small and will be neglected in SSPP will be used in the determination of calculations. forces on the structure: For a fixed structure in an accelera­ = 20 knots ting fluid, the inertial force equals the Surface wind = 20 feet displaced fluid mass times the accelera­ Freeboard Design wave H = 15 ft tion of the fluid mass plus the added (Airy Theory) T = 10 sec mass of adjacent fluid particles times L = 512 ft that acceleration (Ippen, 1966). Thus the total forces on a body under wave As calculated later in this paper action is: th~s gives a total maximum drag of 1:2 x ulul au 10 pounds due to wind, wave, and cur­ FT = F0 + FI = C0A - 2- + CIP"'§t .. (6) rent forces. where is determined experimentally, and c0 RESULTANT FORCES DUE TO LOADS CI is determined from potential flow theory. Currents: Ocean currents vary not Note that in Weigle (1971) and Yamamoto only with time but with position; there­ (1963) there is considerable scatter as fore, current is a dynamic loading con­ dition, and will interact with the to values of CI,Co in an oscillating structure dynamically. In the time do­ wave situation. It has been assumed for main the current will have a spectral the SSPP, that CI = 2.0 and = 1.0. c0 density, and if the dominating frequency However, as has been indicated, these does not correspond to the first model values can only be assigned true value frequency of the structure, the loading through experiment. Yamamoto (1973) in­ due to current can be considered as dicates where Fo and FI are important to consider by comparing h/L to H/D. static. The maximum loading condition should be used. Another force which may occur on a In a uniform velocity the following structure is due to asymmetries in the forces apply: velocity field about the stagnation stream line. This results in forces at right angles to the flow field and FT = Ff + Fo ...... (8) is called lift. Asymmetries e.xist in Ff = friction force velocity fields because of vortex shed­ ding, circulation (Kutta-Jonkowski) or F0 = drag force

95 Ff Cf V2 /2 BL The lift force for R "'6 x 10 3 is approximately 25% of the longitudinal pAV 2/2 Fo c0 force and when the wake is fully turbu­ where lent, the maximum lift force is approxi­ co = drag coefficient mately 40% of the longitudinal force. p = density--(varies with depth, temp., and salinity) Thus, if the loading due to the cur­ B = transverse wid·::h rent can be considered static, the L = length of surface parallel to forces due to current can be calculated flow based on equations (8) and (9). A = cross-sectional area Cf friction coefficient Wind: Loading due to wind can be considered as three separate components: 1 28 For laminar flow, Cf = ·! wind-induced water current, static load due to mean wind velocity and dynamic 5 loading due to turbulence in the air. for transition flow (3 X 10 ~ R 5 X ~ A further breakdown of these loads in­ 10 5). cludes (Plate and Nath, 1969): 0.455 1~700 = ; and cf (log R) 2. 58 - R 1. Wind-induced water current': for turbulent flow (R > 5 x lOs), F = CoPw AV2/2 ...... (10) where c - 0.455 f - (log R) 2. 58 V is the surface velocity proportional to shear velocity, and As the Reynolds number increases vortex shedding occurs in the lee side of the structure. The frequency of this shed­ V = rc;;- C'ws = water surface shear ding can be characterized by the J-p; stress exerted by wind). Strouhal number, i.e., S = fD/V where f = frequency of shedding. As indicated Not a lot is known about this force, in Figure 2, the Strouhal number for 10 2 however, an approximation of 3% of wind < R < 6 x 10 5 is ~ .2. Due to this speed has been used. shedding, a lift force is created which is perpendicular to the direction of 2. Static load due to mean wind flow. This force alternates from side velocity: to side. Therefore, the lo~ding is a -2 dynamic loading and the frequency of F = CoAPA ( UA)avg DL/2 ...... (11) shedding needs to be c01npared with the model frequency of the structure. The CoA = drag coefficient lift force can be calculated as follows: ITA = local temporal mean velocity 2 (avg. with respect to height) FL = CLpAV /2 ... (OSU Engr. Exp. L = some length parameter of structure Sta., 1971) ... (9) A = refers to air motion PA = mass density of air (should contain sea spray) Note: Review of Bishop and Hassen (1964) indicates that the oscillation of a cylinder in fluid flow increases the drag force as much as fourfold. More research is needed in this area to determine tl1e actual effect. Since it can be assumed that any motion of the structure will influence the forces, the dynamic response of the structure must be examined for all loading conditions (i.e., ,comparison of model frequency to loading frequency) before a static condition can be assumed. 0.3

0.2

0 ::J 1­

II en 0.1

0

FIGURE 2. Variation of Strouhal with Reynolds Numbers, Circular Cylinders (Ippen, 1966)

97 3. Dynamic loading: Dynamic loading where is of much greater consequence because Cm = coefficient of added mass = it may add to dynamic loading of waves. C + 1 (2.0 for cylinder, Forces due to air turbulenc~ are gener­ p9tential flow) ally small; however, air turbulence and u and u are obtained from Airy wave spectra have their peaks at larger fre­ theory. For deep water conditions, h/1 = quencies than wave spectra and thus clo­ 1/2, FT can be approximated by: ser to frequency of structure; therefore, their effect may be appreciable. FT = y C~D a 2 cosat lcosatl ­ Waves: As indicated for currents, the 7rD2 . dynamic response due to waves must first y em~ a s1nat ...... (14) be investigated with reference to a sea­ surface spectral density vs. frequency and total moment by: graph to determine if static condition can be approximated. MT = y C~D a2h co sat Icosat I r-k~h~J ­

For a force on cylindric~! pile due 2 y Cm;D ah sinat ...... (15) to a passing wave (5) the Morrison equa­ tk~hlj tion can be applied which consists of drag and inertia components as follows In general: (Nath and Harleman, 1970): h+n · . FT = C~pD J u(s)Ju(s) I ds + ¢(z,t) = CDAP ulul + Bpu re1 0 . 7rD2 Jh+n + c1Bpurel ...... (12) CmP -­4-­ ~(s)ds ..... (16) where 0 B = volume of cylinder p = mean density o£ water Tangential Forces: As has been indi­ c1 = inertia coefficient cated the SSPP has an operating depth of u = relative horizontal bed of 200 feet to take maximum advantage of the 1 re fluid particle with respect existing thermal gradient while being to structure beyond the effective depth of surface u = horizontal acceleration of wave forces. Thus the maximum uplift fluid particle forces will occur when the plant is sur­ u = relative horizontal acceler­ faced for crew rotation or minor repairs. 1 re ation of fluid particle with Assuming again a 20 foot freeboard sur­ respect to structure faced condition with deep water wave con­ u, and u can be calculated from the ap­ ditions of H = 15 feet, L = 512 feet, propriate wave theory (see Figures 3 & T = 10 sec. : 4). However, for design cm1siderations 2 the Airy wave theory can be used as a Tangential drag force (ft)=CfAW /2 .. (17) first approximation. Since both u and ~ where vary with depth, the for-.e due to waves in an integral form (Ippen, 1966) are: w = vertical velocity = agk sinh k (h+Z) cos(kx-at) h+n c · 2 0 cosh kh 9P 2 2 cosh ks I I FT= --2- Da a sinh2kh cosat cosat ds­ A = total surface area parallel to W 0f 5 2 "' 8.8 X 10 ft for SSPP h+n 2 C pnD a~ 2 cosh ks Cf "' 0.01 Of m 4 v sinh kh sinat ds .... (13)

98 _.._ BREAKING (\j -I LIMIT 0 ~ Q) 10 CJ) ...... : ..__..'+­ STREAM (\j FUNCTION V r-­ AIRY ...... -2 I 10 CNOIDAL

,.SHALLOW I I DEEP~ WATER WATER WAVES WAVES -3

10 -2 1 1 10 10- 10° 10 2 2 d I T , ( ft./sec. )

FIGURE 3. Periodic Wave Theories Providing Best Fit to Dynamic Free Surface Boundary Condition (Analytical and Stream Function V Theories)

99 BREAKING ...--... ~ N. -I LIMIT (.) 10 Q) (J) ...... +­ [ill] STOKES V .....__'+­ N ... • AIRY J­ ...... 2 ~ CNOIDAL I I 10

DEEP .. WATER WAVES 163 ~------~------~------~ 10-2 10-1 10° 10 1 2 d I T , ( ft. I sec~)

FIGURE 4. P0riodic Wave Theories Providing Best Fit to Dynamic Free Surface Boundary Condition (Analytical Theories Only)

100 rrH KZ will occur due to the shedding of vor­ Therefore maximum = e w T tices. The nature of the shedding is not well known in oscillatory flows and total drag = JZ ft dZ "' 2000 lbs (Ippen, 1966). The vortices shed in 0 the wake of a circular pile for in­ stance occur at a frequency which is a As mentioned before, this force is function of both the free stream velo­ fairly negligible compared to form drag city and the diameter of the pile. The forces. frequency data are usually presented through the use of the -Strouhal number. Other Forces: S = fD/U ...... (18) l. Wave induced vibrations: In all the wave force treatments of the SSPP The relationship between the Strouhal prior to this a static loading condi­ number and the Reynolds number has been tion is assumed. In actuality the shown in Figure 2. The lift forces on structure will respond to the action of the piling as an example is defined as: the waves and currents in such a way that the equations of motion of the dFL CLpD U2/s dS ...... (19) structure must be satisfied. Experimen­ tal tests, beyond the scope of this re­ where CL is the lift coefficient. If port, are necessary to determine the dy­ the vortex shedding period for a flexi­ namic responses of the structure. Ippen ble cylinder, 1/f, is near the natural (1966) has some experimental data rela­ period of the cylinder, lift forces ting to rigid moored structures. In could occur which were over four times order to accurately determine the re­ the drag force based on a uniform steady sponse of the structure, both the energy flow at the same velocity (Ippen, 1966). spectrum (i.e. the energy per unit fre­ Thus it seems evident that wave induced quency) and the frequency of occurrence vibrations must be considered in the should be determined at the proposed lo­ final design of the SSPP. It has been cation of the structure. These are dis­ shown that in some experiments that the cussed by Kinsman (1965). The structure ratio of maximum lift to maximum longi­ should be designed such that its natural tudinal force is about 40% (Weigle, 1971). frequency is well above the surface wave spectrum in order to avoid a resonance 2. Wave-making drag: Another force condition between the wave and struc­ encountered in designing the SSPP posi­ tural frequencies. Most semi-submerged, tion stabilization system, .especially in pile supported, offshore structures have a swift current such as the Florida been designed with a minimum vibrational Current, is wave-making drag. This is mode period of one second or less. Sta­ the drag resulting from the creation of tic assumptions have been justified in surface waves by the structure in a sur­ these cases since sea spectra do not faced position. The presence of the normally contain significant energy con­ structure causes both local disturbances tent at this low frequency. called bow waves and divergent waves and also transverse or free waves. All of A secondary cause of structural vi­ these waves remain with the structure bration is the vortex shedding in the depending on the free stream velocities. wave induced flow past a structure. Theoretical and experimental data on Even if the natural frequencies of the wave resistance are usually presented in structure are above the wave spectrum, the form of a drag coefficient (CR) as a these frequencies may still be in the function of the Fronde number (U/gh) range of those due to vortex shedding. which in turn is based on body length. As a wave passes a structure, lift for­ The values of CR must be experimentally ces which are quasi-periodic in nature determined for the SSPP and the drag

101 will add to the total ~orce in a sur­ The values of Co, CL, and em are faced condition. determined experimentally, and for the steady state condition the value of c0 3. Coupled heaving and pitching: In is as depicted in Figure 5 and Table 1, a surfaced condition the SSPP will ex­ and a value of 2.0 for Cm has been cal­ perience rectilinear motions of heave, culated from potential flow; however, surge, and sway and the angular motions the fact that the motion at sea is un­ of pitch, roll, and yaw. Due to the 730 steady and oscillatory has precluded ft. cold water intake pipe and the posi­ the direct application of steady state tion stabilization system (dynamic or drag coefficients. Investigation has static) some of these six degrees of its limitations due to the inter-rela­ freedom can be neglected. Thus only the tion of and em (Myers, 1969). Most c0 motions of heave, and pitch will be dis­ of the work to determine drag and mass cussed. McCormick (1973) offers a solu­ coefficient in accelerating flows is tion to these problems through the strip listed in Table 2. A significant rea­ theory method. Other examples are given son for the scatter previously shown in by Myers (1969) with a moored structure, Figure 1 can be attributed to the rela­ the cable tension at the point of attach­ tive roughness of the cylinder. At sea ment to the structure is an additional this condition will be accentuated by constraint on the equations of motion. hie-fouling and corrosion; therefore, a It is also indicated that a symmetric correction to the drag and mass coeffi­ structure with a fairly constant cross cient must be accounted for in their section and a characteristic length use. Figure 6 illustrates the net equal to an integer multiple of the gen­ effect of a roughened cylinder; however, eral wavelength of the design sea state no concrete values for application have will experience no net heaving force. been established and a conservative The structure will experience only a estimate should be used. pitching movement induced by the waves. Also the heaving and pitching motions of a submerged structure decrease expo­ LOAD CASE COMPARISON nentially with depth. However from several experimental results (McCormick, Submerged Loading: It has been 1973) a semi-submerged ~tructure such as shown that in a submerged operating the SSPP will experience little heaving mode, the SSPP will experience loading or pitching motion for all but extremely primarily due to current forces and long waves. Quinn (1972) relates that will respond dynamically and statically the heaving motion from the mean posi­ to these forces. The flow is assumed tion of an unmoored 800,000 DWT tanker turbulent in the region of the cold in a beam sea with 15 foot oscil~atory water pipe and also in the region of waves is less than one-half the wave the main plant. This is based on the height in the vertical direction. overall first design approximation and the critical Reynolds numbers. As a Coefficients: All the forces listed first approximation to the dynamic re­ above have in some way depended on a sponse of the plant with regard to vor­ drag or lift coefficient; therefore, it tex shedding, the factor of 40% of the is appropriate to discuss the limita­ maximum longitudinal force was assumed tions of their use and the relative (Weigle, 1971). Thus including minor range of their values for actual condi­ wave forces and marine growth, a first tions to be expected at sea. estimate of the total force on the sub­ merged structure is 6.0 x 10 5 pounds.

Note: Drag and inertia coefficients are not known for wire or synthetic rope; therefore, they must be estimated from shapes such as those shown in Figure 5. This applies as well to the longitudinal drag coefficient. (An analytical approach has been proposed by Nath, Smith and Yamamoto, 1974).

102 PLATE _L . TO FLOW 10 INFINITE SQUARE \ CYLINDERS~ ·

INFINITE CIRCULAR ----=---=----­----­ CYLINDERS _?------, FINITE CIRCULAR --- 't1 -I CYLINDER 1:4 ELLIPTICALf'-l 10 LID= 5 CYLINDER . STREAMLINED STRuy­' c/D=4, L/c=5 -2 10 ~~~~~~~~~~~~~~~~~~~~--~ -I 2 3 4 6 10 10 10 10 10 10 NR = DV/v

FIGURE 5. Drag Coefficient for Two-Dimensional Bodies

103 TABLE 1. APPROXIMATE VALUES OF DRAG COEFFICIENT AND DISK RATIO FOR VARIOUS BODY FORMS

Disk Form of Body L/D R CD Ratio

Circular disk >10 3 1.12 Tandem disks (L = spacing) 0 >10 3 1.12 1.0 1 0.93 0.83 2 1.04 0.93 3 1.54 1.37

3 Rectangular plate (L ~ length) 1 >10 1.16 5 1. 20 20 1. so 00 1.95 Circular cylinder 0 >10 3 1.12 1.0 (axis parallel to flow) 1 0.91 0.81 2 0.85 0.76 4 0.87 0.78 7 0.99 0.88 Circular cylinder 1 >10 5 0.63 (axis perpendicular to flow) 5 0.74 20 0.90 00 1. 20 5 >5xl0 5 0.35 00 0.33

4 Streamlined foil (1:3 airplane strut) 00 >5xl0 0.10 Hemisphere: Hollow upstream >10 3 1.33 1.19 Hollow downstream 0.34 0.30 Sphere >10 5 0.47 0.42 >3xl0 5 0.20 0.18 ' Ellipsoid (1:3, major axis parallel >2xl0 5 0.06 0.054 to flow) Airship hull (model) >2xl0 5 0.042 0.038

104 TABLE 2. DRAG AND INERTIAL COEFFICIENT VALUES FOR CIRCULAR CYLINDERS IN ACCELERATING FLOWS (FROM [6])

Coefficient Authority Nature of Cylinder Value Type of Flow Diameter and Date Experiments (remarks) (inches) CD eM (1) (2) (3) (4) (5) (6)

Crooke, 1955 Model 2, 1' 1/2 1.60 2.30 Oscillatory Keulegan and Model 3' 2 1/2' 2 1. 34 1. 46 Oscillatory Carpenter, (av. of 29 1956 tabulated values) 1 1/2, 1 1/4 1. 52 1. 51 (av. of 57 tabulated values)

Keirn, 1956 Model 1' 1/2 1. 00 0.93 Accelerated, monoscillatory

Dean, 1956 Model 3 1.10 1.46 Accelerated, monoscillatory

Wiegel et Prototype 24 1.00 0.95 Ocean waves, al.' 1956 west coast (based on their Fig. 15)

Reid, 1956 Prototype 8 5/8 0.53 1.47 Ocean waves, Gulf of Mexico

Bretschneider, Prototype 16 0.40 1.10 Ocean waves, 1957 Gulf of Mexico

Wilson, 1957 Prototype 30 1.00 1.45 Ocean waves, Gulf of Mexico

] (' 5 f'­ 0 I 1 'ss3NH9 noCJ co 9NIS\13CJJNI ! ll o::j :! . I W· I !I ol ll Zj ! I _j' ! : I >-! I II Ul : I I II ~! {f)j i iI C\J . w· ! I 0:: :cl i : I w <.9j !I 0 :::::). i : I z I - ol ! _j - 0 ! ! u ! i II ! co I = I I ~ i i 0 !,,I 0 i i ~ (/)

. /' v C\J

I{) 0 q 0 co <.q C\J C\J 0 Q 0 0 a (.)

FIGURE 6. Effect of Roughness of Drag Coefficient in Supercritical Region

106 Surfaced Loading: The response of the 6. Appropriate coefficients are: structure in a surfaced condition is in­ deed the most critical in the determina­ a. Co = 1.0 cylinder tion of stability calculations. Aside b. Cm = 2.0 cylinder and rope from current, wind, and wave forces one must consider the forces due to structu­ 7. Airy waye theory may be used to ral vibrations caused by waves and shed­ predict u and u (at z = -L/6 for sur­ ding vortices and also forces due to faced condition). wave-making drag and coupled heaving and pitching. It is noted that a small de­ 8. Plant will remain stationary in sign wave and relatively calm sea state a wave (lne spar buoy). has been assumed in the surface loading condition. It is emphasized again that 9. p = canst = 1.98 slugs/ft3 the sea state into which the plant will be surfaced can be chosen at an optimum time. As shown before, the total force FORCES CALCULATION (SUBMERGED CONDITION) due to winds, waves, and current includ­ ing lift forces from flow field asymme­ Current for the turbulent condition: tries is on the order of 1.2 x 10 6 pounds. The vibrations due to waves can ~ (2.5)(50) R . 1.2xl07 , increase the frequency of vortex shedding plpe 1.01 x 1o-s = which in turn will increase lift forces. ~ (5.5) (90) The added forces due to wave-making drag 4.6 X 10 7 , R 1.07 x lo-s and heave will be determined by experi­ plant mentation. 0.455 Cfpipe = (log R)2 58= .0029, and 0.455 MOORING SYSTEM COMPARISON Cfplant = (log R)2 58 = .0024 For the purpose of a comparison analy­ sis of the two types of moorings (dynamic and static), order of magnitude forces For these turbulent conditions, Table will be calculated based on the following 3 summarizes the submerged loading assumptions previously discussed in this forces. From those calculations, paper: therefore, FTr F1' Total F = 498,341 lbs. ~ 1. Dynamic response of the structure long 1/ to waves, current, and wind is such that a static analysis can be made. With F = 498,341 lbs, FL---->j''-"J,T long 2. Current profile at site is as FTr shown in Figure 1. FT rans = ( · 4)(F long ) = 199,336 lbs 3. Plant physical configuration is as shown in Figure 7.

4. Surfaced condition will exhibit Wave: Wave forces would be felt for 20 feet of freeboard. a portion of the plant length since L/2 = 256'; however, their effect would 5. In surfaced condition plant will be minor compared to the current forces. be subjected to: Therefore, in this analysis, a force of ~ 6 x 105 lb will be assumed in the sub­ a. 20 knot wind ( UA ) merged condition (wave effect will influ­ b. 15 foot waves , 10 sec period, ence the tension in the mooring line 512 ft long since the plant will not follow the wave). c. h = 2000' 107 1 1s1' 1 200 ~~~~-~~~~~7f'- •••••••..••••••••••••••••••••••••••••.••••••••••••••••••••••••••••••••••••••• 270 !fl{!l!~ u -.I~ 400 -.,.__ -'+-­ I ...c.,.__ .. ~. :·!!!=~! ~· 0.. Q) iiiii!iiii>il Fronta I area 0 600 :llllil!lll!l~ pipe: 36,500 ft 2 :~rl~lt! plant: 6,3oo ft2 •••••••••••••• 'f~i~~~:~~:n

800

•••••••••••••• I 1000 ±ill

FIGURE 7. Elevation View. of Plant

108 TABLE 3. PLANT SUBMERGED CURRENT LOADING

Section Area Velocity I lb Co c£ H/sec Ff lb Fo

Vertical 5,000 1.0 0.0029 1. 26 9.0 7,859 pipe 9,000 1.0 0.0029 2.10 26.0 39,293 14,750 1.0 0.0029 2.95 51.0 127,078 7,000 1.0 0.0029 4.22 125.0 121,525

Plant 2,250 1.0 0.0024 4.22 212.0 39,400 5,400 1.0 0.0024 5.50 947.0 161 '716

Totals 1,370.0 496,971

109 FORCES CALCULATION (SURFACED CONDITION) Current: V = (0.03)(33.8) = 1.01 ft/sec­ Current: Ff is minor and will be dissipates over 50', therefore 1.01 ft/ ignored. Table 4 summa:rizes Fo for this sec is used for 25'. condition. 2 Flong = c0 P~V = 4,545 lbs ...... (21) TABLE 4. PLANT SURFACED CURRENT LOADING R = (l.Ol)(90) = 8.4 x 106 (turbulent) 1.07 x 1o-s Section Area Vel. Fo F = 1,818 lbs. trans

Plant 4,500 6.94 214,350 Waves: Again, maximum loading will be calculated for wind load acting in Pipe 2,500 6.94 119,205 the same direction as current loading. 3,250 6.34 129,329 _ agk cos h k(h+z) 4,000 5.50 119' 790 u - - h kh ...... (22) (J cos 9,000 4.22 148,673 14,750 2.95 127,078

2,500 2.10 10,915 where a = 7.5 Total 879,340 k = 2 /L = 0.0123 kh = 24.54 z = -60' for the plant, and z = -145' for the pipe; and, Therefore, F = 879,340 lbs long F = Co pA Yh1 + CmpBv...... (24) 2 and, Ft rans = 351,736 lbs

Wind: Maximum loading will be calcu­ Plant: lated for wind load acting in the same direction as current loading. u = [(1.5)(32.2)(0.0123) /(2~/10)] [(cos h 23.86)/(cos h 24.54)] Static load: = 2.395 ft/sec Flong-- CDA PA ( -UA)avg 2 DL/2 ...... (20) u = [(7.5)(32.2)(0.0123)] =[(1.0)(2.34 x lo-3)(20 x 1.69)2] [(cos h 23.86)/(cos h 24.54)] [ (90) (185)/2] = 1.505. ft/sec2 = 22,350 1bs u and u are 90° out of phase with max "u" at the crest of the wave. Ther~fore V = 33.8 ft/sec forces are taken at that point for u = 0. (33.8)(90) 7 (1.0)(1.98)(90)(90)(2.395) 2 R = 1.7 X 10-4= 1.8 X 10 (turbulent) F = long 2 = 45,997 lbs Ft rans = 8,940 lbs

110 2 4 R = ( ' )(90) = 2 0 x 107 turbulent TABLE 5. MW AND HP TABULATION FOR 1.07 X 10-5 ' VARYING VELOCITY Ftrans = 18,399 lbs. v ft/sec Q ft3/sec HP Mw Pipe: 8 606,060 70,085 52.3 U = ((7.5)(32.2)(0.0123)/(2TI/10)] 10 202,020 36,502 27.2 [(cos h 22.82)/(cos h 24.54)] 12 121,212 31,538 23.5 = .85 ft/sec 15 75,758 30,799 23.0 (1.98)(50)(175)(.85)2 F long 2 = 6,259 lbs 17 60,606 31,647 23.6 16 67,340 31,149 23.2 = (.85)(50) - 4 8 106 R 1.07 X 10-5- ' X turbulent Fn-n..n~ Ftrans 2,504 lbs. = Also, J/'FT TID 2 f 1.91"\-~---", Q pAV = p -4- v Total: Flong = 1,035,000 lbs j~F. F-Trc:Lr6 1 Ftrans = 414,000 lbs or, D2 = ~~v ...... (27)

FT = (FL 2 + FTR 2) = 1,114,729 Therefore, for V = 15 ft/sec, use 1.12 x 106 lbs as an order of magnitude D = = 56 ft or its [~]!zp7rV equivalent DYNAMIC POWER REQUIREMENTS Therefore for dynamic positioning a If dynamic mooring is used, then a minimum of 23.00 Mw must be expended to thrust of approximately 1.2 x 106 lbs maintain plant on station. If a loca­ must be generated by the plant to stabi­ tion which minimizes current is found lize the plant at the surface. As this for the plant then the magnitude of the power needed will be reduced since cur­ ~hrust must come from the power plant, 1ts computation is necessary. rent is the predominant force. In this case it would be impractical to use = dynamic positioning as 23 Mw of the 25 Knowing F pQ(V 1 -7) (at surface V "' 7 ft/sec) Mw plant output would be required for positioning. If, however, the same F profile is used as in Figure 8 but with or, Q = p (V-7) · · .. · · · .. · · ...... (25) the currents normalized such that sur­ face velocity is 1 ft/sec, then current yQ(V 2 /2g) forces would be as shown in Table 6. and, HP = 550 ...... (26) From Table 6 then, required horsepower and required mega­ F = 18,186 lbs, and watts (Mw) may be calculated as summar­ long ized in Table 5. Ftrans = 7,274 lbs.

111 j

j

j

j

j

j e ? j j I j I D/SCONE j ANTENNA j WIRES j

j

j

j

j

j

j

j

j

j

j PRESSURE j j

j

j

j

j j

j

j

j

j

FIGURE 8. j Free-Body Diagram of Buoy with All Forces Shown Schematically j

j

j 112 j

j Thus by changing only current forces D =9ft., and at V =6ft/sec, D = and leaving other contributing loads 34 ft. unchanged we have, In this situation dynamic position­ F = 98,915 lbs, ing is possible and since the plant is 1ong to be manned, the system would be reli­ Ftrans = 39,567 lbs, and able such as that proposed for Hawaii model city (Seidl, 1973). FT = 106,535 ~ 1.1 x 10 5 lbs.

STATIC MOORING - MOORING LINE ANALYSIS TABLE 6. NORMALIZED PLANT DRAG FORCES ' For the analysis of the total ten­ Area Vel FD sion in the mooring line of a static Section (ft3 ) (fps) (lbs) mooring system and hence the sizing of the line and anchor system, drag forces Plant 4,500 1.0 4,461 similar to those for the structure must be considered. This analysis would 2,475 Pipe 2,500 1.0 only consider static forces due to gra­ 2,664 3,250 .91 vity, steady wind and current. Second­ 4,000 . 79 2,472 ary considerations are the oscillating 9,000 . 61 3,315 forces due to waves and gusty wind. 14,750 .42 2,576 Another oscillating force results from 2,500 .30 223 the steady drag on the body which gives Total 18'186 rise to vortex shedding and thus oscil­ lating forces previously mentioned which are perpendicular to the direc­ Dynamic mooring: From equation (25), tion of the current, waves,,and wind with a normalized velocity of 1 fps we (strumming). Longitudinal drag will have, effect the frequency response of the line (Nath, Yamamoto and Smith, 1974). Q = F/p(V-1) Another varying force which will Thus, Hp and Mw values may again be effect the position of the buoy is tabulated as shown in Table 7. current. This effect is discussed by Fofonoff and Garrett (1968), as shown TABLE 7. NORMALIZED MW AND HP CALCULA­ in Figures 9 and 10, who plot the ex­ TIONS FOR VARYING VELOCITIES cursions of a single point moving surface buoy. v ft/sec Q ft 3 /sec HP Mw To account for the dynamic forces from waves and gusty winds a numerical 2 55,556 401 . 3 4 18,518 535 .4 procedure was developed by Nath and 6 11,111 722 .54 Felix (1970). The position and condi­ 8 7,937 917 . 7 tion of the buoy and line due to steady forces were determined as the 10 6,173 1,115 '83 initial condition for the dynamic case. 12 5,050 1,314 1.0 The resulting force equations which 14 4,273 1,513 1.1 are keyed to Figure 8 are as follows: 20 2, 778 2,007 1.5 25 2,222 2,509 1.9

Since, from equation (26) D = [(4Q)/ CIAXL PT V Az2 ...... ···· (29 ) (pTIV)]~, it follows that, at V = 20ft/sec,

113 .------SPEED (FE::T I SECOND) 1.0 1.0

1­ w w LL

I 1­ (l_ w 0

500

1000

1500 Ds ------­ .06

9 2000

FIGURE 9. Polygonal Approximation

114 SPEED (FEET/SECOND) -

~300 I 1­ a.. w Cl 2 500

1000

1500

2000

FIGURE 10. Polygonal Approximation

115 where where product of total polygonal CDAXL = drag coefficient in axial Bs = direction length by line density W = h(n) W/sin¢(n) with h(n) = depth CIAXL = inertial coefficient in wn axial direction of uniform current region "n" A = vertical surface area w0 = o T = static line tension DB = drag on the buoy relative velocity between Vz2 = OM drag on segment m Do = 0 water and buoy at lower chine = PT = mass density of water psi = ~pCdV~hm cubic ft. with d = diameter of line Az2 = relative acceleration at p = water density lower chine hm = width of layer "m" v = submerged volume and, n=i-1 (Fo + Fr)x2 = cDRAD APT vx2\Vx2\ + ¢i = tan- 1 [(B8 L Wn)/ n=O CIRAD PT VT Ax2 ...... (30) m=i-1 where (DB+ L Om)] .... (32) m=O = drag coefficient in x2 where direction Ti and ¢i are the tension and angle CIRAD = inertia coefficient in X2 of inclination of line at node "i" direction respectively. relative velo~ity between Vx 2 = water and buoy For a normalized velocity profile VT total submerged volume of given in Figure 9, and using a 1.75" buoy wire rope (3 x 46), Ax2 = relative acceleration between water and beoy DB = 1.1 X 10 lbs, As summarized by Nath and Felix (1970), w = 5.12 lb/ft' "the motions and position of all points = (20,000 ft)(5.12) 102,400 lbs, on the line are determined from the Bs forces acting on it and from the line d = .146 ft' and state of the previous increment of time. c = 1.0. The tension at the top of the line is determined from the strain at the top, These calculations are summarized by which is influenced by the buoy node in Table 8. position..." It is obvious from the angle of in­ A determination of the relative magni­ clination of the line that tow under tude of the lift and drag forces at the will probably occur due to the inclusion surface can be approximated with the use of dynamic forces. To avoid this con­ of the following equation from Berteaux dition a multi-point mooring should be and with Figure 9. utilized to reduce the amount of drag experienced by any one line. This would n=i-1 m=i reduce the value of 08 and thus increase Ti = (Bs L Wn) 2+(Ds + L DM) 2 •.• (31) the scope thereby increasing the angle n=O m=O of inclination.

116 TABLE 8. MOORING LINE FORCES BY NODE

0 Node E E D (1b) Wn (1b) m Ti (1b) h

0 0 0 1 915.6 99 149,736 43.0° 2 1,407.3 152.3 149,442 42.6° 3 2 ,013. 6 201.7 42.5° 4 3,383.0 231.2 42.3° 5 5,643.2 462.3 41. go 6 7 ,041. 9 488.4 41.2° 7 10,348.6 501.9 40.8° 8 15 '772. 2 503.9 140,412 39.8°

117 If the scope = 12 for a single point Then, mooring, BB ~ (length)(Wwr) +buoyancy of buoy w= 30 lb/ft, (reserve) where ¢i = tan- 1 6.55 = 81.3°, and Wwr = lb/ft for 1" wire rope (3 x 19) Ti = 728,354 lbs. or W= 5.12 lbs/ft. However, one is now outside the present state-of-the-art for ancaorage systems Thus, BB ~ 18,000 lbs, which will hold this large a force. W = 5.12 lbs/ft, However, if a multi-point is used, T ~ 20,000 lb, the system will loose the capability to surface. Since this is a primary pre­ u = .16 slugs/ft requisite of the design, a multi-point L = 17,000 ft, and mooring cannot be recommended. f = 7.35 HZ. Therefore, no reasonance is to be expected and a static approach COMBINED SYSTEM can be taken. Using Figure 10, Table 9 is generated. If the plant is stabilized by both dynamic and static mooring, i.e., dyna­ TABLE 9. COMBINED SYSTEM MOORING LINE mic when surfaced and static when sub­ TENSION merged, then the drag force will have an order of magnitude of 1.0 x 10 4 lb when conditions have been normalized Node l:Wn lb l:Dm lb T lb

Strouhal number = fD/V where the 1 223 7.0 60.9° diameter= 1" wire rope (3x46), 2 751 14.5 60.6° 3 3 R = range 6.6 X 10 - 1.5 X 10 3 1,076 17.0 59.9° s .2 = 4 1,841 19.0 59.4° .2V/D f = 5 2,740 19.4 18,256 58.2° range = 1.46 to .14HZ 6 56.7° Equations for modal frequency for transverse vibrations (Nath, et al, 1973) is: length of line 2, 000 ft. , free body at anchor fi = (T/u)/(2L) ...... (33) 15,260 where fi = modal frequency in HZ, 18,256 lbs T = average line tension, u = effective mass per foot, and ....______..,. 10, 02 3 1bs L = line length.

Note: Wire rope has been used because 1) failure of other types of lines from fish bites; 2) buoy will not be surface-following, so elasticity is not needed; and 3) required accurate position against large loads.

118 Thus when plant is surfaced the drag CONCLUSIONS force will be overcome by dynamic posi­ tioning and the mooring line will support 1. The results of this study indi­ only itself and the reserve buoyancy of cate that submerged plant operation has the plant. Rechecking frequency of shed­ considerable advantage over surfaced ding, operation. Surface wave and wind for­ ces are essentially eliminated and f = .14 to 2.4 cycles/sec, current forces substantially reduced. frequency of wave ofT~ 10, f = .63 cycles/sec. 2. Dynamic mooring is impossible for the 25 Mw plant in a high velocity current Therefore, there will be no re-sonance as more power is required for that mooring and the system can still be considered than is produced. It appears that, while static. dynamic mooring may become feasible for larger plants, the excessive amount of power required will make it undesirable. MOORING SYSTEM SUMMARY 3. Based on this study, it can be The analysis of a mooring system es­ concluded that the forces generated in sentially is composed of three parts: a high velocity current are such that 1) investigation of resonance frequency dynamic positioning is not feasible of system versus oscillating forces; 2) and static mooring reliability at best static analysis of system to design con­ only about 54%, based on the presenta­ ditions; and 3) dynamic interaction of tion by Walden and Panicker (1973). system with forces. Presently many areas In fact, current is one of the main remain under investigation, such as 1) sources of failure experienced in that the values of c0 , CI and CL to use and study where a high current was consid­ under what conditions the values can be ered approximately two ft/sec. There­ used; 2) the dynamic interaction between fore, an area with a low current pro­ forces and system; 3) mooring motion and file is desirable for mooring, and in response of mooring lines, etc. In prac­ this situation the best mooring for a tice the designer relies heavily on "surfacing" plant might be a combination Morrison's equation, Airy wave theory, a static-dynamic system, i.e., static and Co and CI values derived from steady, submerged, dynamic surfaced. uniform flow conditions. Many unknowns exist as to the validity of this method; 4. Multiple point mooring shows sig­ therefore, normally large safety factors nificant advantages for on-site mooring. are used and the system is over designed However, the requirement for periodic so that it will last. The state-of-the­ plant surfacing negates their use. art is not at the point where a most eco­ nomical design can be used; therefore, in 5. Extensive additional research this approach to the problem of static vs is needed in the general area of moor­ dynamic mooring, an order of magnitude ing line analysis. Current state-of­ study was used to present a logical ap­ the-art limitations must be pushed proach to the problem and point out areas back a considerable distance in order where refinements can be made. to fully specify the requirements of a Sea Solar Power Plant mooring and anchoring system.

119 REFERENCES

Bascom, Willard, Waves and Beaches. New York: Doubleday &Company, Inc. 1964.

Beard, R.L., Statistical Methods in Hydrology. U.S. Army Office of Chief of Engineers, July, 1952.

Berteaux. "Introductio~1 to the Status of Single Point Moored Buoy Systems", Woods Hole Oceanographic Institute, Technical Memo No. 11-68. 1968.

Bishop and Hassan, "The Lift and Drag Forces on a Circular Cylinder Oscillating in a Flowing Fluid", Proceedings of the Royal Society (London). Series A, Vol. 277: p. 51-75. 1964.

Bretschneider, C. L., "Wave Variability Spectra for Wind Spectra for Wind­ Generated Gravity Waves." Tech Memo No. 118, Beach Erosion Board. U.S. Army Corps of Engineers. 1959.

Dantz, P. A. "The Padlock Anchor - A Fixed Anchor System", Naval Civi 1 Engineering Laboratory Technical Report No. R 577. U.S. NCEL: Port Heuneme, California. 1968.

Daugherty and Fromzini. Fluid Mechanics with Engineering Applications. New York: McGraw-Hill. 1965.

Falvey, Henry T. "Prediction of Wind Wave Height", Journal of the Waterways, Harbors, and Coastal Engineering Division. ASCE IDD(WWI): 1-12. February, 1974.

Fofonoff and Garrett, "Mooring Motion", Woods Hole Oceanographic Institute Technical Bulletin. No 58-31, 1968.

Fluid Mechanics for Hyciraulic Engineers. Dover: Hunter House, 1961.

Gumbel, E.J. Statistics of Extremes. New York: Columbia University Press, 1958.

Ippen, Arthur T. Estuary and Coastline Hydrodynamics. New York: McGraw-Hill Book Co. 1966.

Kinsman, B. Wind Waves. New Jersey: Prentice-Hall. 1965.

McCormick, Michael E. Ocean Engineering Wave Mechanics. New York: John Wiley & Sons. 1973.

Myers, John J. Handbook of Ocean and Underwater Engineering. New York: McGraw­ Hill Book Company. 1969.

Nath, John. "Some Considerations for Buoys and Their Moorings." Oregon State University Circular No. 41. 1971.

Nath, et. al. Offshore Research Tower. Oregon State University Department of Oceanography. December, 1973.

120 Nath and Harleman, "Response of Vertical Cylinders to Random Waves", Journal of Waterways and Harbor Division. ASCE. May, 1970.

Nath, Yamamoto and Smith, "Longitudinal Motion of Taut Moorings", Journal of Waterways and Harbors Division ASCE. February, 1974.

Oregon State University Engineering Experimental Station. Seminar Proceedings: Topics in Ocean Engineering. OSU Engineering Experimental Station C1rcular No. 41, 1971.

Plate and Nath, "Modeling of Structures Subjected to Wind Waves", Journal of Waterways and Harbors Division, ASCE. November, 1969.

Quinn, Alonza DeF. Design and Construction of Ports and Marine Structures. New York: McGraw-Hill Book Co. 1972.

Seidl, "Hawaii Floating City Development Program", NSF Technical Report No. 2, May, 1973.

Smith, J. E. "Investigation of Free-Fall Embedment Anchor For Deep Ocean Application", Naval Civil Engineering Laboratory, Technical Note No. 805, Port Hueneme, California. 1966.

Smith, J.E., R.M. Beard, and R.J. Taylor. "Specialized Anchors for the Deep Sea" Naval Civil Engineering Laboratory Technical Note No. 1133, Port Hueneme, California. 1970.

Taylor, R.J. and R.M. Beard, "Propellant-Actuated Deep Water Anchor: Interim Report", Naval Civil Engineering Laboratory Technical Note No. 1282, Port Hueneme, California. 1973.

Taylor, R.J. and H.J. Lee, "Direct Embedment Holding Capacity", Naval Civil Engineering Laboratory Technical Note No. 1245, Port Hueneme, California. 1972.

Tudor, W. J. "Mooring and Anchoring of Deep Ocean Platforms''. 1967 ASCE Conference, Proceedings, San Francisco, California. 1967.

U.S. Navy, Naval Facilities Engineering Command. Design Manual - Harbor and Coastal Facilities. NAVFAC DM-26. July, 1968.

U.S. Naval Oceanographic Office. Oceanography Atlas of the North Atlantic Ocean. Pub.No. 700, Sec. IV. 1963.

Walden and Panicker. "Performance Analysis of Woods Hole Taut Moorings", Woods Hole Oceanographic Institute Technical Report. No. 73-31. June, 1973.

Weigle, R.L. "Waves and Their Effects on Pile Supported Structures", Seminar Proceedings: Topics in Ocean Engineering. OSU Sea Grant Circular No. 41. 1971.

Yamamoto, Nath and Slotta. "Yet Another Report on Cylinder Drag or Wave Forces on Horizontal Submerged Cylinders", OSU Bulletin No. 47. OSU, 1973.

121 ANNEX 1.

ANCHORING SYSTEM EVALUATION

CONVENTIONAL ANCHORS 8. Strength and ruggedness to with­ stand maximum holding powers, vertical Other than in the case of "dynamic breakouts, and lateral pulls. positioning", an anchorage 3ystem must rely on its attachment to the ocean Several serious disadvantages of floor to obtain fixity at one location. conventional anchors are: Securing to the ocean floor may best be achieved with implements embedded deep­ 1. Considerable horizontal distance ly and firmly into the bottom material. is required to adequately set this type Design of conventional anchorages gen­ of anchor, necessitating large amounts erally utilizes the standard drag-type of rope and gear and a massive mooring anchors. complex to make the plant.

The following characteristics of con­ 2. Resistance to uplift is small ventional anchors for adequate holding and minor uplift loads can seriously power and reliability are summarized reduce normal holding capacity. from the Naval Facilities Engineering Command design manual (NAVFAC DM-26, 3. Since the anchor offers primarily 1968). horizontal resistance, even a group of anchors placed at 120 degrees to each 1. Correct angle between flukes and other may not provide the desired re­ shank for digging in (35 degrees for straint for a majority of contemplated sand and 50 degrees for mud) structures which will impose large uplift forces. 2. Large fluke area for anchor weight. Schematic diagrams and details of conventional anchor design are dis­ 3. Large tripping palms for use in cussed by P.A. Dantz (1968). mud.

4. Sharply pointed, thin flukes. DIRECT EMBEDMENT ANCHORS

5. A stabilizer or stock to prevent At present, the primary means of cockscrewing or rotating. securing structures to bottom in depths 500 feet and greater is by using dead­ 6. Ability to bury itself quickly weights. Many shapes, materials and without excess drag. constructions are used, but all gravity anchors have low efficiency developing 7. Good efficiency meas~red by the only their own weight in resistance to ratio of holding power to weight. horizontal forces. Also, they are un­ stable and unreliable on sloping bottoms.

122 Conventional drag-types are unsatis­ Detailed diagrams and design speci­ factory for use in deep water. They are fications of direct embedment anchors designed to be embedded into the bottom are discussed by Taylor and Beard by dragging to develop horizontal pull (1973). resistance and once embedded they lose holding capacity if uplift forces are applied. Generally, a dragging place­ HOLDING CAPACITY ment procedure may be impra~tical in water more than 500 feet deep. Also in Techniques for predicting the maxi­ great depths, it is difficult to prevent mum uplift forces which may be applied uplift forces from being applied. To to direct embedment anchors without overcome dragging and the uplift force causing the anchor pullout are provided problem, conventional anchors sometimes by Talor and Lee (1972). are used in tandem on the anchor line with another anchor or a deadweight. Though slight advantage gained by this FT = A(CNc + YbDNq) ...... (1) procedure, handling and placement prob­ where lems are increased. FT = holding capacity (lbs) The direct embedment anchor best sat­ A = fluke area (ft2 ) isfies the requirements of a deep ocean anchorage. Two advantages of this type C = cohesion of soil (psf) anchor are the capability to embed direct­ Yb buoyant unit weight of soil (psf) ly into the bottom without the necessity = of dragging and the capability to resist D = fluke embedment depth (fl) significant uplift loads. Direct embed­ Nc,Nq = holding capacity factors ment shortens the lowering and placement time, enhances the precision of placement, and reduces the quantities and sizes of For rectangular flukes, accessory gear. Uplift resistance pro­ vides for both reduced amounts and vari­ FT = A(CNc + YbDNq)(0.84 + .16 B/L) ety of connective gear and greater flexi­ ...... (2) bility of application of the anchor. Of where the direct embedment anchor types, eg. B = fluke diameter or width vibratory, propellant-actuated, hydrosta­ tic, free-fall; the propellant-actuated L = fluke length anchor proved most simple, reliable and economically feasible. Characteristics Strength of soils by the Mohr-Coulomb of one propellant-actuated anchoring sys­ equation, tem are shown in Table A-1. Tf = C + N tancjl ...... (3) Although additional tests will be re­ quired at various depths and into differ­ where ent types of seafloors to fully charac­ = shear strength terize this type of anchoring system, Tf initial trials indicate that the explo­ c = cohesion sive type of propellant activated anchor N normal force on failure plane is: 1) most workable; 2) achieves accept­ = able holding capacities in silt seafloors; cp = initial friction angle 3) assemble quickly and easily; and 4) revolutionary fluke keys rotate quickly For cohesive soils, equation (2) reduces and show no distress from penetration or to: pullout (Taylor and Beard, 1973). FT = A(CNc + YbD)(0.84 + .16 B/L) .. (4)

123 TABLE A-1. A PROPELLANT-ACTUATED DIRECT EMBEDMENT ANCHOR (Taylor and Lee, 1972)

Characteristic

Functional water depth ------100-20,000 ft. Capacity-----Minimum long term holding capacity - 20,000 lbs.

Sand fluke Clay fluke

Length (in) 38 63 Width (in) 18 30 Plan area (ft ) 4.5 12.5 Fluke weight (lbs) 147 337 Piston weight (lbs) 116 116 Piston extension weight (lbs) 24 24 Connective gear weight (lbs) 13 13

Gun barrel 37 inch long, 26 inch projectile stroke, 11 inch cartridge Short start pressure 3,000 psi Propellant Navy Pyrotechnic Projectile weight 300 lbs and 490 lbs Launch vehicle weight 1,540 lbs Projectile muzzle 225 fps, 490 lb projectile velocity goals 275 fps, 300 lb projectile Maximum allowable gun barrel pressure 35,000 psi

124 Nc = 3.8(0/B) (. 7/C + 0.3) ...... (5) is retrievable where the anchor deploy­ ments in water depths is less then or, Nc 9, whichever is smaller, for = 500 feet. 0.75 psis C ~ 4 psi.

For cohesionless soil, equation (2) SELECTION OF ANCHORING SYSTEM reduces to: Anchor designs, special apperten­ FT = AYbD Nq(0.84 + .16 B/L) ...... (6) ances, connective gear, and special operational techniques are among the more critical areas that need improve­ INSTALLATION ment. The single most important consi­ deration is the anchor design as im­ Having characterized the several proved anchors can alleviate problems types of anchoring systems, a brief re­ in the other areas. While considera­ view of installation techniques should tions such as expense, ease of handling be made. Three installation techniques and storage will influence the choice will be covered: free-fall, dragging of anchor, the single most important (both used for conventional anchoring characteristic is the anchor's holding systems), and propellant-activated power. It is this fact which makes the (used for the direct embedment anchor). holding power to weight ratio so impor­ tant. For any given anchor, this ratio Free-fall: The free-fall technique is not fixed, but depends particularly is adequately described in Figure A-1. on the nature of ocean bottom. Certain anchors are designed for certain types Dragging: Application of the requi­ of bottom considerations and therefore site horizontal force at great depths may not work well when they encounter require excessive gear, and it is diffi­ other than the design type surfaces. cult if not impossible to sense the Formulas to roughly estimate the hold­ amount of movement and depth of embed­ ing power of various types of anchors ment achieved. for different bottom conditions have been developed, but for any given situa­ Therefore, the current procedure is tion the actual holding power of an to determine the amount of tension de­ anchor should be determined in tests at sired in the connecting apparatus during the site. installation and then to drag the anchor until this amount of tension is achieved. Selection of a specific anchoring Next, the tension on the line is kept system for the Sea Solar Power Plant within established maximum and mimimum cannot appropriately be made without the limits until installation is complete. inclusion of a number of considerations Thereafter, it can be deduced by perfor­ outside the scope of this paper. Figure mance of the moor whether or not the A-2 details a schematic for one approach anchor is embedded as desired. to anchor system selection. While not all background information required for Direct embedment anchor (Propellant­ full use of this schemitized method is actuated anchor): The anchor assembly presented in this paper, the required and the launching system is lowered steps and step flow ordering can still into the sea. When a probe protruding be understood. 26 inches below the fluke tip contacts the seafloor, the firing sequence is At some stage of development of a initiated. After penetration is com­ Sea Solar Power Plant, a similar analy­ plete, a small pull on the main cable sis will be required to determine an causes the fluke to keg (rotate into its actual anchoring system. Beyond the resistive position). The launch vehicle general discussion included in

125 Surface marker buoy FREE-FALL used in multileg buoy buoy one~~~g~~::

-z.._lowering line disconnected

__...-z--- mooring sound waves line from bottom detector

..... N 0\ -1 bottom sensing - distance

~f:~·,tr:!?[K}?::t??:?=:

Surface buoy Lowering stopped Anchor lowered Anchor system streamed astern when detector gently to in place - anchor being impacts bottom bottom

c lowered rapidly

FIGURE A-1. Free-Fall Installation Technique FIELD TEST FIELD TEST Obtain short­ Take measured term holding Cohesive Cohesion less holding capacity, capacity, Fr Fr

Estimate friction Obtain Fr angle, :.0, and unit Obtain Fr weight, 'Yb

Short Short Repeated -term Predicted holding and static capacity is Fr f--:=,o.:..:.n;;..g-< term static

Holding capacity long-term is 1/2 Fr static

Develop design to Estimate· drained reduce effects of repeated loading friction angle, 0 with factors of safety = 10

Holding capacity Calculate drained for design purposes holding capacity, Fm is 1/2 Fr

Using D/B, calculate Fr

Holding capacity Holding capacity Holding capacity is Fr is Fro is 1/2 of Fr

FIGURE A-2. Block Diagram Illustrating Suggested Procedure for Predicting Embedment Anchor Holding Capacity

127 this Annex, Table A-2 lists the charac­ method can be applied where the bottom teristics of a number of anchoring sys­ is essentially level and currents in tems which could be used to support such the area are of low magnitude. an analysis. 2. Direct Embedment Anchors: The Certain general conclusions may be propellant-actuated type, as compared drawn about the deep water anchoring with other types of embedment anchors system: (vibratory, hydrostatic, free-fall), offers simplicity, reliability, and 1. Conventional Anchors (see Squaw economy. Results indicate a 300-lb Anchorage System): To prevent uplift embedded anchor can develop 20,000 lbs force, deadweights were used. This holding power.

128 TABLE A-2. ANCHOR SYSTEM CHARACTERISTICS

Type Characteristics

Mass anchor. Simple. Holding power to \\:eight ratio is low. Handling and transporting lS expensive. These anchors are not reliable on sloping hard bottoms and are easily moved laterally when loaded with a vertical and horizontal load.

Mushroom anchor. . Poor penetrating powers. It is considered a good mud anchor usually sinking by its own weight through soft mud to firm strata, and getting good bearing against a large volume of mud ahead of it. However, if the anchor should ever drag under load, it will probably come out.

Stock (Admiralty) anchor Old fashioned or common anchor. The area of the palm is not so large for its weight and, therefore, it depends on digging deep to get good holding power.

Navy stockless anchor.. Approximate holding-power-to-weight ratio of 6 to 1 in a sand bottom and 2 to 1 in a mud bottom. Anchors weighing from 20,000 to 30,000 pounds do not dig into sand until the fluke angle has been restricted to 35 degrees. A stabilizer bar increases the holding resistance by approximately 10 percent.

Lightweight anchor . Fluke angle is 30 degrees. The holding power i in sand does not vary as a constant times the weight of the anchor, but approximately as a constant times the weight raised to the 9/llth power. As the size of an LWT anchor increases, the holding power drops off in relation to its weight.

NAVFAC STATO anchors . . Rates of holding power to weight larger than 20 to 1 in sand or 15 to 1 in mud can be obtained if the anchors are preset, or if the mooring site will permit drag distances longer than 50 feet. Anchors are not to be loaded beyond 30 times the anchor weight.

Umbrella pile anchor High holding capacities and resistance to uplift where conventional anchorage systems are unsuit­ able. It is limited to uncemented homogeneous soil. Driving anchor in over 200 feet is diffi­ cult. A hammer with energies from 15,000 to 20,000 foot-pound is required for emplacement.

129 TABLE A-2. cont.

Stimson deep-sea anchcr . . . High holding power by its own weight plus the resistance to pull out due to its embedment. It should be lowered with sufficient tension to ensure its landing in an upright position.

Free-fall embedment anchor.. The holding-power-to-weight ratio is approximate­ ly 3 or 4 to 1. The free-fall anchor concept as it applies to the specified objectives and cri­ teria is not feasible. A minimum ratio of 7 to 1 is considered necessary.

Screw type embedment anchor . Suitable for pipeline anchoring system. Shallow water use. Driving anchor in over 200 feet is difficult. Explosive (Propellant­ actuated) embedment anchor. . Opening fluke and shieldlike shape type. Three different flukes are needed for sand, clay and rock conditions. The holding power of the SO­ kip rated in coastal waters has been recorded at 60,000 pounds in sand and clay and the 300 kip rated anchor has been recorded at 200,000 pounds holding power in sand and clay. Quick and easy handling, assembling.

Padlock anchor...... A tripod configuration with bearing pads located at the extremities of the arms. The reliability of this system depends on the reliability of the embedment anchors. Successful discharge and test 1oading to the depth of 6, 000 feet have demon­ strated the potential of this anchor complex for deep ocean application.

Pulse-jet anchor...... Two principal parts called a mass drag reactor and a ballistic embedding anchor. It was unable to achieve an experimental model of the design envisioned.

Vibratory anchor...... Large flukes for low strength soils and small flukes for high strength soil. Concept is feasible, exceptional holding capacities were achieved in several tests. Anchors take verti­ cal pull over 80 times its own weight. Handling is simple. Balanced design that matches the energy required to achieve proper embedment with fluke size to obtain the rated holding capacity in different types of seafloors. j

130 SEA SOLAR POWER PLANT - GEOLOGY AND BIOLOGY OF THE MIAMI PLANT SITE

by

Bruce Higgins

ABSTRACT

The criteria for an idea site are Nearby cores are brought to light for outlined and the pros and cons of this the anchoring of the plant and the site are discussed in the geological animals which will be living there. and biologicallaspects. The narrow The fishing, both sport and commercial, continental shelf gives good access to are discussed. An outline of the cold, deep water as well as the Flor­ specific studies to be conducted prior ida current continuously refresshing to construction are included. A brief the supply of both surface and bottom investigation of the variability of waters. The offshore sediments, their ., sediments and transits in animals is strength and composition are discussed. brought into focus.

131 1

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1 SEA SOLAR POWER PLANT - GEOLOGY AND BIOLOGY OF THE MIAMI PLANT SITE

by

Bruce Higgins

INTRODUCTION 4) Wave, Wind, and Tide The proposed site for an offshore ther­ These are important if the mal power plant is the Miami, Florida plant is to remain long on the surface area. We will look here at the basic geo­ for repairs and effort should be made logical, physical, and biological features to minimize their presence. of the area. The reasons this site was chosen become apparent when viewed in the 5) Geothermal light of the general site analysis. The Other sources of hot water principal elements and critical factors should be looked for other than the to be investigated include: ocean and incorporated if feasible.

1) Bottom Survey 6) Water Quality The water should be deep near­ A broad term which includes shore and have a hard bottom. The area chemistry and biological activity in should be geologically stable. the area. Effort should be made not to disturb "Mother Nature" more than 2) Water Temperature absolutely necessary. The water should be very stra­ tified, and have a minimum of seasonal variations. PHYSICAL AND CHEMICAL PARAMETERS

3) Currents Basic physical and chemical background Depending on the design, they information has been compiled in Table 1. can be avoided or greatly depended on. The facts look dry but some very impor­ They should be well accounted for and tant observations come from this informa­ not changing seasonal in site area. tion.

133 TABLE 1. MIAMI AREA

Depth Physical Parameters 200 ft 1000 ft

Temperature 21° - 26° c go - 10° c Salinity 36.3°/00 35°/00 Current Velocity 2. 0 fps 0.9 fps Total Transport 26 X 106 m3/sec Weather - Hurricanes 1 per 3 years for 70 years

Depth Chemical Parameters 200 ft 1000 ft

Dissolved Oxygen 5.5 mt/t 2 mt/t Total Nitrogen 1 11g-atom N/t 6 llg-atom N/t Nitrate 1 llg-atom N/t 50 llg-atom N/£ Inorganic Phosphorus 0.1-1 11g-atom P/t 4 llg-atom P/£ Dissolved Organic Phosphorus 0.01 11g-atom P/t 0.5 llg-atom P/t Organic Carbon 1 mg C/t 8 mg C/t Silicate 10 11g-atom Si/t 160 llg-atom Si/t Carbon Fixation 150 1150 mg/m2day PH 8.2 8.1 Light 1/30 to l/50th of none I surface value

134 The physical parameters show the site Charts in Figures 6 and 7 provide more to have a large stable temperature gra­ detail of on site bottom sediment and corn­ dient which is disturbed primarily by position as this information is critical hurricanes which can leave large cold to anchoring system design. The sediment water pockets near the surface for up to is thick with 300 feet appearing maximum eight days. These have been observed in closer to shore and the area composed of the Gulf of Mexico and there are some calcareous ooze and forrniniferal sand. theories on their formation. This is an The escarpment though is as free as can area of research where attention should be found of sediment with bed rock show­ be paid to future developments. The ve­ ing in places. The deep trough at the locity of the current and the mass tran­ base of the escarpment is an errosional sport are not as stable as one might be­ feature and is maintained by the Florida lieve. So, plots were obtained for Current. yearly mass transport (Figure 1) and for average surface velocity (Figure 2) A fault zone through the area brings which show interesting variations. The up the question of area stability. In designer will have to study the specific recent years, the number of recorded site with care, but the peak values quakes in this area are few, and of very would be useful. low magnitude. The detailed record of these could not be found but would be The chemical parameters show that very useful information. there is a wide fluxuation in values with depth. A graph of dissolved oxygen The sub bottom geology is most easily (Figure 3) demonstrates the magnitude of seen through the use of Table 2 which the fluxuations of which the Florida wa­ includes information on the penetrometer ters are capable. In most cases it ap­ readings of a nearby site. More detailed pears that there is a larger quantity of information for the specific site is desired nutrients at depth. The trans­ desired but this available data provides port of these to surface layers by the insight as to the range of numbers ex­ plant is being studied for aquaculture pected at the sea solar power plant site. potential. A rnonitering station and search for more complete data in the area would prove very valuable. SITE BIOLOGY

The biological species of the region SITE GEOLOGY are best handled in the fo1~ of lists as their behavior in the off shore waters of The geology of the area provides very the plant site are not fully understood. deep water very near shore. This region Table 3 gives the major benthic types has one of the narrowist continental found in these waters, at the bottom shelves on the eastern sea board. The depth of the plant site. Major fish spe­ sediment has a knoll like feature due to cies are summarized on Plates 1 - 7. possible solution holes from previous up Details on the characteristics and toler­ lifted time. The included chart of the ance limits of each one are out of the area (Figure 4) does not include all of scope of this report. The fish are known the details known of the area, but the to school and the catches of economically overview information is sufficient at important fish are listed on Table 4 along this time. The near shore and sub bot­ with the catch obtained by fishing fleets torn geology are included in Figure 5 to of the region. The shell fish of the re­ present a general picture of the composi­ tion are also very important and a list of tion of the coast. these is included in Table 5. The size of

135 the numbers reflects the catches near shore as it has been observed that few CONCLUSIONS fish are taken in water deeper than 300 feet depth and that there are no impor­ This site is found to be a very fav­ tant fishing grounds east of 80°W. The orable location, The questions of the phytoplankton of the region will surely fault and depth of sediment still must travel through the plant no matter what be looked into but are not drastically plant design is used. Species known to different from most of the east coast. exist in the site area are included in The biology of the site is favorable in Table 6. that there is diverse, and extremely active populations which is much more Typical diurnal migration of these adaptable to the changes that might be zooplankton is shown in Figure 8 which imposed by the plant. This paper was gives magnitude of the population and intended to be an overview of the in­ depth variation with time in one day. formation on the Miami area. Much more From this figure we see that the plant detailed on-site work will be required will not be able to avoid influencing a to define the environment of this area portion of the plankton population in and the impact of a sea solar power the region. More detailed work is plant upon it. needed near the plant site to isolate the dominant fish and plankton species.

136 -bj ~40 (f) 0::: w I­ ~ 30 u en ::) 20 u w 0 ...... 10 ~ 0 0... (f) z AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY <{ 0::: I- 1952 195 3

FIGURE 1. Mass Transport of Florida Current - Key West to Havana (Stommel, 1965)

137 150

(.) w (f) ...... ~ 100 (.) z >­ I­ (.) 50 0 _j w >

0 MIAMI CAT KEY

FIGURE 2. Average Surface Velocity of the Florida Current (Murry, 1952)

138 -(/) a:: w I- 1000 w ~ ...... I I­ ()_ w 2000 0

3000~----~~----~------~------~ 0 2 4 6 8 OXYGEN CONCENTRATION ML/L

FIGURE 3. Characteristic Oxygen Profile of the Atlantic (Stommel, 1963)

139 20'

50 ... . .·.·.· .•·: ...... ·:: .. ..:· .. : ::":" .. .. ::- .. ·.··.

40'

20'

0 (/) w _J ~ _J 10 <( u 25°N i= :::> <( z 20

1 40 20' 80°W 40'

FIGURE 4. Bathymetry of Miami Terrace (Koford and Malloy, 1965)

140 OCEAN B A

...... -!'­

. MIAMI []. OOLITE

FORT THOMPSON KEY LARGO ~ FORMATION ~ LIME STONE UPPER TAMIAMI CALOOSHATCHEE 'f.~· FORMATION MARL

FIGURE 5. Biscayne Aquifer - Dade County Florida Generalized Geologic Cross-Section (Runnels, 1971) .:.:: ...... ·.

FIGURE 6. Sediment Distribution Near Miami (Pratt, 1971)

142 CONTOUR INTERVAL · ·::/ . . . .: 50 FATHOM · .· :.:: . . .. : ...... ·.... ::...... :: .. . . ·:· . -· .. : .....·:...... ::: . . . . . ·:

...... ·..·.. . 0 • : ••••:.·••• ., ..•... :::'r!! •

t­ -J :::J Lt UP DOWN

FIGURE 7. Bed Rock Contours and Fault Trace (Kofoed and Malloy, 1965)

143 SUNSET 0 10:00 PM. SUNRISE 1:oo P.M.

20

-(f) 0::: 40 w I­ w f-0 60 .j>. ~ .j>. ..._... ------­_f~~~~TWATER l_iNTAKE DEPTH I 80 I­ 0.. ~ 100

120

140

FIGURE 8. Diurnal Migration of Adult Female Calanus Finmachiuus (Sverdrup, 1942) TABLE 2. GLOMAR CHALLENGER SUB-BOTTOM GEOLOGY DATA

Site: Hole 48 Location: Just south of Miami (25° 22.95' N, 77° 18.68' W) Sub-bottom Characterization: 0-120 M: Foram nanno ooze which spans Holocene­ Pleistocene to the Oligocene period. Baleocene reflector at 280 M. Penetrometer Readings: Depth Penetrometer Reading 5 M 9 M 15 M 12 M 20 M 6 M 225 M 6-7 M Site: Hole 4 Location: Farther south and east (24.5° N, 73.8° W) Sub-bottom Characterization: 0-10 M: Calcarenite foram overlying clay 10-75 M: Calcarenite largely foram and nanno planton marl 75-130 M: Pebbly mud stone with limestone clasts Matrix of clay and nanno marl Some interbedded with nanno chalk 130-190 M: Nanno marl and chalk with chert 190-250 M: Nanno chalk

TABLE 3. LARGE DEEP-SEA ANIMALS BELOW 200 M (From: Heezen and Hollister, 1971)

Sessile Coelenterates Sponges Gorgonians Pennatulids Actinarians Antipatharians Mobile Echinoderms Arthropods Crinoids Isopods Astezoids Decapods Ophiuroids Arachnoids Echinoids Holothurians Chordates Hemichorates Molluscs Tunicates Cephopods Fish Annelids Polychaets

145 REQUIEM SHARKS

MACKEREL SHARKS

NURSE SHARKS

PLATE 1. Primary Area Sharks

146 MANTAS

SHARKS . ·...... · ..·.·

...... :·· .··

WHIPTA IL STINGRAYS

PLATE 1. Continued

146a ...... 0. 0 •••••• . . .:.·. ·. ·..·.:.·. ·. ·. ·.. :: 0:.: :. ·.. 0 ·.:,.·••••

......

FINTAIL STINGRAYS

EAGLE RAYS

PLATE 1. Continued

146b ,.

SEA BASSES

HERRINGS

PLATE 2. Primary Game and Commercial Species

147 DOLPHINS

JACKS, SCADS 8 POMPANOS

SURGEONFISHES

PLATE 2. Continued

l47a ANCHOVIES

TUNAS AND MACKERELS

BARRACUDAS

MULLETS

PLATE 2. Continued

147b THREADFINS

SAWFISHES

TARPONS 8 LADYFISHES

PLATE 3. Primary Game and Commerc1·al Species

148 SOAPFISHES AND ALLIES

BASSLETS

PLATE 3. Continued

148a BONEFISHES

CARDINALFISHES

SNOOKS OR ROBALOS

LIZARDFISHES

PLATE 3. Continued

148b TONGUEFISHES

SOLES

PLATE 4. Primary Bottom Fish

149 BUTTERFISHES

PLATE 5. M"lnor Gamefish

150 SAND STARGAZERS

CL IN/DS

JAWFISHES

PLATE 5. Continued

150a SCORPIONFISHES

COMBTOOTH BLENNIES

THREEFIN BLENNIES

PLATE 5. Continued

I SOb DRAGONETS

SEA ROBINS

FLY!N(} GURNARDS

PLATE 5. Continued

150c TRIGG£RF/5H£5 a FIL£FISH£S

TRUNK FISHES

TOADF/SH£5

PLATE 6. Minor Area Species

151 PORCUPI NEFISHES

.~;2::~

TRUMPET FISHES

CORNET FISHES

FROGFISHES

PLATE 6. Continued

15la ~r:Z~n:~r;;~~::~~';:~::;;.;:;;;;:,;;::D::.::::~;,~·~

SEAHORSES AND PIPEFISHES

PUFFERS

PLATE 6. Continued

15lb BATFISHES

CL/ NGFISHES

PLATE 6. Continued

ISle TABLE 4. FLORIDA LANDINGS IN DADE COUNTY 1970 (Florida Dept. of Natural Resources, 1970) '

Species: Fish Pounds .. Ballyhoo (Halfbeak) 142,856 Blue fish 5,988 Blue Runner 11 '259 Cabio 225 Crevalle (Jacks) 6,095 Croaker 5,236 Dolphin 4,205 Drum (Black) 587 (Red) 1'113 Groupers 70,745 Grunts 39,314 Hog fish 2,393 ' Jew fish 696 King Mackeral 51,237 Mullet (Black) 50 (Silver) 211 '846 Permit 18 Pompano 12,585 ! Scup 2,408 I Sea Trout (Spotted) 8,282 Sharks 3,250 I Sheepshead 1,480 Snapper (Lane) 977 (Mangrove) 26,107 (Mutton) 42,410 (Red) 108,169 (Vermi 1 ion) 111 (Yellow tail) 153,902 Spanish Mackeral 327' 164 Unclassified 21,882 Total 1,262,590

152 . TABLE 5. FLORIDA LANDINGS IN DADE COUNTY 1970 (Florida Dept. of Natural Resources, 1970)

Species: Shellfish, etc. Pounds

Conchs 30

Crabs (Blue, hard) 12,570 (Stone) 109,751

Lobster (Spiny) 2,766,858

Turtles (Green) 744 (Loggerhead) 469

Sponges (Grass) 4,533 (Sheepswool) 4,505 (Yellow) 2,549 Total 2,902,009

153 TABLE 6. PHYTOPLANKTON SPECIES COMMON TO THE GULF OF GUINEA, THE WESTERN TROPICAL ATLANTIC, CARIBBEAN SEA AND STRAITS OF FLORIDA (Wood, 1968)

DIATOMS Planktoniella formosa c. minutum P. sol c. pentagonum Actinocyclus ovatus Pleurosigma capense c. praelongum Asterolampra grevillei Pl. directum c. pulchellum A. marylandica Pl. hippocampus c. rani.pes Asteromphalus brookei Pl. naviculaceum c. setaceum A. flabellatus Pseudoeunotia doliolus c. symmetricum A. heptactis Rhizosolenia alata c. teres A. hookeri R. bergonii c. trichoceros A. roperianus R. calcar avis c. tripos Bacteriastrum delicatulum R. castracanei Ceratocorys armata B. varians R. cylindrus C. horrida Biddulphia chinensis R. delicatula Cochlodiniwn faurei Cerataulina pelagica R. imbricata Dinophysis exigua Chaetoceros affine R. setigera D. ovum Ch. coarctatum R. stolterforthii Dipeopsalis lenticula Ch. concavicorne R. styliformis Erythropsis sp. Ch. decipiens Schroederella delicatula Exuviaella baltica Ch. denticulatum Striatella interrupta Goniaulax birostris Ch. laeve Synedra superba G. diegensis Ch. lorenzianum S. ulna G. kofoidi Ch. messanense Thalassiosira rotula G. monacantha Ch. neapolitanum Thalassiothrix frauenfeldii Goniodoma polyedricum Ch. pendulum T. longissima Gymnodinium flavum Ch. similis T. medtierranea G. gelbum Ch. socialis Tropidoneis affirmata G. marinum Ch. vanheurckii G. mirabile Climacodium frauenfeldianum. G. simplex CYANOPHYCEAE Corethron criophilum Murrayella biconica Coscinodiscus africanus Richelia intracellularis Ornithocercus magnificus c. concinnus Trichodesmium thiebautii 0. quadratus c. excentricus 0. steini c. lineatus DINOFLAGELLATES 0. thurni c. marginatus Oxytoxum belgicae c. radiatus Amphidinium klebsi 0. constrictum Dactyliosolen mediterraneus A. turbo 0. milneri Detonula confervacea Amphisolenia bidentata o. scolopax Eucampia cornuta A. globifera 0. tesselatum Fragilaria linearin Blepharocysta splendormaris 0. turbo F. striatula Ceratium arietinum Parahistioneis para Goasleriella tropica c. azoricum Peridinium brochi Guinardia flaccida c. belone P. cerasus Hemiaulus hauckii c. buceros P. depressum H. membranaceus c. candelabrum P. divergens H. sinensis c. carriense P. globulus Hemidiscus cunieformis c. extensum P. grande Leptocylindrus danicus c. falcatiforme P. grani Mastogloia rostrata c. furca P. pendunculatum Navicula acus c. fusus P. steini Nitzschia closterium c. gibberum P. subinerme N. gracilis c. gravidum Phalacroma cuneus N. lonaissima c. kofoidi Ph. dolichopterygium. N. seriata c. massiliense Ph. doryphorum

1 C:.-1 TABLE 6. cont.

Ph. hindmarchi Pr. scutellum Michaelsarsia elegans Ph. mitra Protoceratium reticulatum Scyphosphaera apsteini Ph. ovum Pryocystis fusiformis Dictyocha fibula Ph. parvulum Py. lunula Eutreptia viridis Ph. rotundatum Py. pseudonoctiluca Halosphaera viridis Podolampas palmipes Pyrophacus horologicum Isochrysis sp. Pod. elegans Warnowia atra Platymonas sp. Pod. bipes Pyramimonas sp. Porella perforata OTHER FLAGELLATES J.l-flagellates Prorocentrum dentatum Pr. micans Coccolithus huxleyi

155 REFERENCES

Bohlke, and Chaplin. Fish of the_ Ba_h_a_El_a_:;_ anE_A

Florida Department of Natural Resources. Summary of Florida Commercial and Marip~ La.!ldings. 1971.

Gentry, R.C. "Hurricanes - One of the Major Features of Air-Sea Interaction in the Caribbean Sea." Symposium of Investigations and Resources of the Caribbean Sea and Adjacent Regions. 1968.

Heezen and Hollister. The Face of the Deep. New York: Oxford University Press. 1971.

Hill, ed. The Sea, Volume 3. New York: Inter Science Publishers. 1965.

Kofoed, J., and Malloy, R. "Bathymetry of the Miami Terrace." Southeastern Geology. 6(3): 117-175, July, 1965.

Pratt, R.M. "Lithogy of the Rocks Dredged from the Blake Plateau." Southeastern Geology. 13(1): 1-89, May, 1971.

Shepard, F.D. Submarine Geology. Scripps Institution of Oceanography, 1973.

Stommel, A. The Gulf Stream. University of California Press. 1965.

Sverdrup, H. V. The Qc!'_ans, Their Physical C_?emi~a_l~and_G_enera}_ Biology. New Jersey: Prentjce Hall, Inc. 1942.

Wood, E.J. Ferguson. "Phytoplankton Distribution in the Caribbean Region." Symposium of the Investigation and Resources of the Caribbean Sea and Adjacent Regions. 1968.

156 SEA SOLAR POWER PLANT - EFFECTS OF ENTRAINMENT and INTAKE SCREENING CONSIDERATIONS

by

Ken Haven

ABSTRACT

Effects of entrainment into the plant 1) prevent entrainment of any object or on biota through both warm and cold wa­ organism large enough to be potentially ter intakes and screening methods to pre­ harmful to the plant, 2) prevent entrain­ vent such entrainment are discussed. ment of as many living organisms as possi­ Changes in physical and chemical p:roper­ ble so as to avoid the ill effects of en­ ties and their affect on biota as the en­ trainment on them, and 3) to prevent harm vironment is entrained through the vari­ to biota during the exclusion process. ous unit operations in the plant are an­ In general, optimum screening systems will alyzed. These unit operations include: be a function of the local environment at intake screens, intake pipes, pumping the intake, critical pipe dimension of the systems, internal piping, condenser/eva­ plant, and value of local marine popula­ porator systems, and discharge. In gen­ tions. Some minimum level of screening eral no part of the environment emerges will be required to protect plant opera­ from the discharge flow unchanged. As tion. Beyond that, additional screening none of these effects are beneficial to protection capabilities may be purchased the entrained environment, discussion of for improved environmental protection de­ potential screening systems for both the pending on the results of a trade-off be­ warm and cold water intakes is included. tween construction and operation cost ef­ The objectives of such screening are to: fectiveness and environmental protection.

157 I j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j SEA SOLAR POWER PLANT - EFFECTS OF ENTRAINMENT and INTAKE SCREENING CONSIDERATIONS

by

Ken Haven

INTRODUCTION

A sea solar power plant may be viewed can be internalized into plant cost con­ as an externality thrust upon the natural siderations in the form of improved aquatic environmental ecosystem. The screening systems required to prevent presence of the plant will cause some entrainment. changes, or rebalancing, of that ecosys­ tem. In evaluating the total costs and benefits of the power plant then, some EFFECTS OF ENTRAINMENT attempt should be made to internalize into the calculations costs and benefits Entrained seawater is introduced into which occur to the environment as a re­ the plant through both the warm water sult of the plant. Such an accounting (200 ft depth) and cold water (1000 ft would have to include costs and benefits depth) intakes and passes through the in a number of general areas including: following plant elements before discharge effects on the marine biotic environment at a 270 ft depth: intake screens, intake and behavior from the physical presence piping, pumping systems, internal piping, of the plant; effects of excretions from condenser/boiler tubing, and discharge. the plant (leaks, sewage, biofouling re­ This report will consider the effects of tardation agents, etc.); effects of en­ each element seperately before summarizing trainment of a portion of the environ­ the total effects of entrainment on the ment into and through the plant; effects environment. Hydraulic and temperature on local circulation and current patterns gradelines throughout the plant are shown as a result of the plant. This paper will in Figure 1. evaluate only the effects of entrainment and will introduce some basic considera­ Intake Screens: tions for plant circulation and recircu­ Water velocities across these intake lation in Annex 1. screens are 2 fps and 4 fps for the warm and cold water intakes respectively. Once the effects on local organisms of Actual screening systems proposed for use entrainment have been evaluated, they

159 ..

WARM WATER DISCHARGE INTAKE AMBIENT CONDITIONS

. INTAKE IDISCHA RGEI I PUMPS IPIPING I CONDENSER I ps1 ...... (J\ 0

COLD WATER DISCHARGE INTAKE AMBIENT CONDITIONS

TEMPERATURE

-20°F -13° F JI'V

FIGURE 1. Plant Hydraulic and Temperature Gradelines at each intake are discussed later in There are several species of phyto­ this report. It is sufficient at this plankton sufficiently large to be impin­ point to say that the main screens at ged (Sverdrup, 1942). Their total per­ each intake will be 1/8 inch mesh cent of this open ocean population cannot screens, either traveling or serviced be known without an on site population by a rotating scraper. The effect survey. However, this percent, both in then of forcing the environment across species numbers and in population number, these screens is as follows: is generally small (Hill, 1965). Those few who are impinged are, with rare ex­ Chemical: No chemical changes or ception, killed (Clark and Brownell, effects will result from transition 1973). Intake screens do not pose a ma­ across the screens. jor threat to phytoplankton, and the vast majority of this population will pass Physical: No major physical changes through the screens undamaged. A much will accompany traverse of the screens. lesser number will suffer some mechanical There will be a minor head loss experi­ damage, and a very few will be impinged enced. However, this is not significant and killed. either in itself or to the life forms associated with it. Zooplankton and small invertebrates: This class includes members of several Phytoplankton: Phytoplankton are mi­ invertebrate phylums which generally con­ croscopic plant forms, including such stitute zooplankton (Phylum Protozoa and species as algae, which form the basis Arthropoda which contain among others, of the marine food chain. They lack in­ dinoflagellates and crustaceans respec­ dependent motion, and are found exclu­ tively) (Sverdrup, 1942) and the larval sively in the euphotic zone of the ocean and juvenile stages of many other species. (that top layer of the ocean which re­ This group is found predominately in the ceives direct solar light). This zone euphotic zone, but is represented by a in the Florida current normally extends number of species at depth. For example, downward to the 250 ft layer (Murry and over 30 species of crustaceans are found Hjort, 1965). Thus phytoplankton are at 1000 ft and several are centered at not found in the environment of the cold that depth range (Sverdrup, 1942). Cer­ water intake and are a concern only of tainly the total zooplankton population the warm water flows. at the 1000 ft depth is a small percentage of that in the upper layers. Intake screens, in general, have no effect on phytoplankton. The extremely Many zooplankton, like phytoplankton, small size of this group means they are are sufficiently small to avoid impinge­ too small to be trapped by, or impinged ment and pass through intake screens. upon, the intake screens, and will pass However, a substantial number of species through into the plant itself. There are large enough to be impingable (Hill, will be some mechanical damage from col­ 1965). As zooplankton also lack any real lision of individual phytoplankton with swimming capability, these biota will be mesh wires. This damage however will be impinged and killed. Thus zooplankton minimal as the wire surfaces of the mesh suffer somewhat more damage at the screens represent only 21% of the gross mesh ar­ than do phytoplankton. Mechanical damage ea and are "no-flow" areas. Thus, the is increased slightly and kill rates are natural flow of water around the mesh increased substantially. will tend to direct phytoplankton away from the wires.

161 Large invertebrates and vertebrates: of freeing themselves for escape. Those This group includes ali of the larger in­ that do escape normally have suffered vertebrates, as jelly fish, starfish, some degree of mechanical damage, and etc., and all true vertibrates in the many die some time later as a result ocean. The population is spread through­ (Sonnichsen, 1973). The second potential out the nektonic regions with essentially for impingement of this plant is in the all classes, except for several benthic fact that the intakes are vertically phylum and classes, represented at all oriented. Fish are much better able to depths. Population densities are gener­ resist a horizontal current than a verti­ ally much higher in the upper layer, due cal one (Sonnichsen, 1973). Thus any to increased food supply there, but sub­ fish brought under the influence of these stantial numbers still inhabit the depths intakes have a higher probability of (Murry and Hjort, 1965). being pulled into the screens than they would if the intakes were horizontal. Intake screans are designed primarily to exclude this class of nekton from en­ Screens can pose a very large danger try into the plant. With the exception to large invertebrates and vertebrates. of a very few of the smaller species, Screen, options listed later can mini­ this is precisely what happens. However, mize this impact. The potential impact this does not say they are not damaged of screens, however, is large kill rates and/or killed, only that they are exclu­ and extensive mechanical damage. ded from the plant itself. Clark and Brovmell (1973) report on a number of Intake Pipes: large screen kills which have occurred As the warm water intake is directly at existing large power plants and con­ adjacent to its associated pumping sys­ clude that, "Screen kills are a major tem, there is no intake pipe to consider. and growing problem with large power The cold water intake pipe is a major plants located on estuaries, using once structure and has a large impact on the through cooling... ". If intake screens entrained environment. These effects are not designed specifically to avoid include: such fish kills, these screens can have a greater impact on the vertebrates than Physical: Travel up the cold water would the rest of the plant were the intake pipe entails a vertical assent of screens not present. 700 ft. Associated with this assent will be a pressure change of over 310 psi. In The potential cause for these verte­ addition the water temperature will rise brate and large invertebrate kill rates slightly- something less than l°F -due at this plant are two-fold. First, fish to warming from the ambient water outside are naturally attracted to the type of the tube. At 4 fps this trip will take velocity gradients associated with this 175 seconds, or just under 3 minutes. plant's intake flows (Sonnichsen, 1973). Thus, the time rate of change of pressure, Once there they tend to allign with or pressure gradient will be just over those gradients. In a relatively short 1.75 psi per second. time, depending on the fish size, type and current velocity, they lose the abil­ Chemical: No significant chemical ity to resist the intake current, and changes should be experienced. through exhaustion, are pulled into the intake screens and impinged. Once im­ Phytoplankton: As phytoplankton will pinged, they will either remain impinged not be present in the cold water flow, until death occurs, or will be capable there will be no effects on phytoplankton from intake piping.

162 Zooplankton and small invertebrates: Physical: The physical effect~ of It has been reported by Sverdrup (1942) pumping will generally be confined to the that "(because of the seawater stability) pressure increase designed for the pumps. ... the organisms (primarily zooplankton) In this case, that pressure increase is in general, have not developed highly slightly under 10 psi. Associated with specialized integuments and regulatory this there will be a slight temperature systems to protect themselves against increase, but again this should be less sudden and intense environmental changes than l°F in either the warm or cold water ... It follows that even slight changes flow. in the aquatic medium are promptly brought to play upon the population." Chemical: Again, no significant chem­ ical effects are foreseen. The intense, rapid pressure change associated with this assent will severly Phytoplankton: Effects to phytoplank­ affect most zooplankton species. Some ton will include: 1) some mechanical of the more sensitive species will show damage from the pump blades and pump significant kill rates, and the vast ma­ housing, and 2) effects of the sudden jority will undergo some form and degree pressure change. The effects of sudden of shock (Sonnichsen, 1973). changes in pressure are different for different species of phytoplankton, but Large invertebrates and vertebrates: in general these effects are a function No general effects can be identified for of the absolute magnitude of the change, this group. Effects will vary drastic­ the duration of the change before return ally from species to species. Those with to normal conditions, the rate of change, swim bladders will generally be unable or gradient, and the species involved to survive this pressure change. The (Sonnichsen, 1973). Insufficient data gradient is more severe than that which exists at this time to specifically eval­ most species are able to compensate. uate the effect of any or all of these They will literally explode. Those with­ variables on a given species. In general, out such bladders should be basically as any of these factors increases, the unaffected by this pressure differential. detrimental effects of that change will However, at a depth of only 1000 ft, also increase. there are relatively few species without swim bladders (Thorson, 1971). The In the case of this plant, the magni­ temperature change is sufficiently small tude of that pressure change will be that few species will be affected by it; approximately 10 psi, the increasing however, many species will suffer some pressure gradient across the pumps will form of mild shock from general environ­ be extremely steep, and a 20 second trip mental changes (temperature, velocity, through the evaporator will be consumed etc.) (Murry and Hjort, 1965). returning that pressure to ambient con­ ditions. Pumping Systems: Pumping systems for this plant are One case is related by Clark and currently designated as variable pitch, Brownell (1973) where in a 15 psi pressure variable speed, propeller type pumps. change held for 10 seconds had minor to Effects related here are geared as speci­ moderate affect on the sample. It is felt fically as possible to this type of pump that for this plant, the effect of pumping without considering differing effects and associated pressure change will be rel­ from alternative pump types. atively light on phytoplankton species, with most of these detrimental effects con­ centrated in the more sensitive species.

163 Zooplankton and small invertebrates: There will be a minor pressure drop due to Greater mechanical damage will be exper­ piping head loss, and there will be addi­ ienced by this group th~n was felt by the tional minor mechanical damage on larger phytoplankton due to irrcreased average individual species. Beyond this, internal organism size. This mechanical damage piping will have no significant effect on should be light to moderate, with most of the environment. the damage concentrated in the larger species. Zooplankton reaction to pres­ Condenser/Evaporator System: sure changes appear to be similar in na­ The physical composition of these sys­ ture, and in dependence on the magnitude, tems is fully described in other reports. duration, and gradient of the change, to The critical dimension of these assemblies that of phytoplankton (Sonnichsen, 1973). is the 1/4 inch diameter of the actual However, the tolerance levels of most tubes. Anything larger than 1/4 inch species of zooplankton are considerably will be impinged on the tube entrance higher than for phytoplankton species. plates. Velocities through the tubes Thus it is felt, though neither substan­ will remain 4 fps. The environmental tiated nor refuted by a literature effects of this system include: search, that damage to zooplankton from pumping will not be severe. An ernperi­ Physical: Pressure drops of under 10 cal validation of this assertion is that psi will be experienced uniformly over planktonic samples are often run through the 18 second trip through these tubes. pumps during on board ship processing Simultaneously there will be a uniform with little if any damage (Curl, 1974). temperature decrease of 4°F for the warm Certainly the pressure change from such water flow and a temperature increase of a pumping operation is much less than 4°F for the cold water flow. that from the pumping system at this pow­ er plant; however, the analogy does add Chemical: Minor effects only will be weight to this viewpoint. experienced by the chemical environment. It is possible that the relatively high Large invertebrates and vertebrates: dissolved carbonate levels in the cold Pumping effects on this group must be water flow, and especially the calcium termed severe. Extensive mechanical da­ carbonates will begin to precipitate out mage will result from the size of this of solution under the influence of re­ group of organisms and the speed of the duced pressure and warmer temperatures pumps. Very few vertebrates will pass (Sverdrup, 1942). Should this occur, through such a pumping system without efficiency of the condenser would be sig­ undergoing extensive damage, Clark and nificantly impaired. Brownell (1973) sight several examples of this type of inner plant kill in Phytoplankton: Most of the effects of which many millions of fish were killed the changes associated with the evaporator by mangling within a relatively short system are residual effects tied to the period of time. initial pressure change at the pumps. That is, the reduction back to normal Internal Piping: levels here will merely define a limit on There is a minimum of internal p1p1ng the effects of the initial 10 psi pressure in this plant due to the large flow change rather than define a new effect on rates involved. It is only a very few the phytoplankton. This total pressure feet from the pumps to the condenser/ effect has already been discussed. The boiler assemblies. Over this short a temperature change of only 4°F would be distance there will be very few changes insignificant by itself (Clark and Brown­ brought to bear on the environment. ell, 1973, and Sonnichsen, 1973).

164 However, it may have some additive effect inch tubes. Therefore the majority of when combined with the plant pressure those delivered to this point will be­ changes. At present this is not known; come impinged at the tube entrances and however, it appears that any effect on will die. phytoplankton from this slight tempera­ ture change would be minimal and would Clorine added: One of the probable be concentrated in the IraTe sensitive biofouling reagents added to the flow at species. some point, especially to the warm water flow, will be clorine gas in very small Zooplankton and small invertebrates: smounts. This action would affect phyto­ Simularly to phytoplankton, the effects plankton in that flow since as little of this pressure drop will be tied to the as 0.5 ppm of clorine gas can be lethal effects associated with the initial pres­ to phytoplankton (Hirayamo and Hiramo, sure increase at the pumps, and will not, 1970). This effect, of course, is a therefore, be an independent effect of function of the individual species, and the condenser/boiler system. Turbulence not all species are affected at that con­ at the entrance to the individual tube centration level. However, phytoplankton will increase mechanical damage somewhat. kill rates from such added clorine could Finally, the temperature change of 4°F be significant. will have minor effect on all but the most sensitive zooplankton species. One Discharge: test indicated that 80°F temperatures The discharge of warm water flow is at would result in, "death or damage to an a 270 ft depth and is directed vertically appreciable portion of the more sensitive downward. That for the cold water flow species" (Clark and Brownell, 1973). is at a 270 ft depth and is also directed They further showed that sustained 95°F vertically downward. Effects of this temperatures were required to kill es­ action include: sentially all zooplankton species tested. Temperatures in the warm water flow will Physical: The warm water flow, at never exceed the mid 70's (°F) and the discharge, is at ambient pressure and is evaporator condenser drop will leave the approximately 4°F below ambient tempera­ flow temperature prior to discharge in ture. As the discharge is directed down­ the mid to high 60's (°F). Similarly, ward, most of this water would penetrate the cold water flow temperature will to lower depths before its kinetic energy never have a gradient or magnitude of was disipated. Thus the temperature dif­ change large enough to significantly af­ ference between this flow and the mean fect zooplankton populations prior to final ambient conditions is close to 3°F. discharge. The cold water flow is discharged at ll°F below the ambient conditions. Whether Large invertebrates and vertebrates: this discharge will form an integral In reality very few live functioning plume and retain certain of its own members of this group would ever pene­ characteristics or will disipate into trate to the condenser/evaporator sys­ local current.flows and achieve ambient tems. Those that do penetrate to this standards is not know at this time. point will encounter severe mechanical damage from turbulence at the tube en­ Chemical: Chemical changes for the trance and from the small size of the warm water flow at this point will be tubes themselves. Few species of this negligible as ambient chemical environ­ class are small enough to negotiate the ~ ment is essentially identical with that

165 at the warm water intake. The cold water discharge, however, wi l1 meet significantly d i ffercnt chemical conditions. Dissolved nTAKE SCREENING CONSIDERATIONS oxygen level is very low at 1000 ft but is much higher at the lower edge of the The previous section established a very euphotic zone. pH is slightly higher at low probability of survival for marine 300 ft than at 1000 ft. More important, organisms entrained into either plant nitrogen and phosphorous are some 8 and intake flow. As examples of this sort 5 times more concentrated at depth than of damage the following inner power at 300 ft, respectively. As these are plant kill data is presented (Clark critical to marine life, their release at and Brownell, 1973): this level could be significant (Svedrup, 1942), even though it is being released 1. Brayton Point Power Plant, Mass.: near the bottom of the euphotic zone. 50 million fish killed in 11 days by "mangling" in August 1971. Phytoplankton: As mentioned above the phytoplankton are being released with a 2. Millstone Power Plant, Conn.: downward velocity which should carry them 36 million fish killed in 16 days, out of the euphotic zone. As phytoplankton November 1971 . require the light present in the euphotic zone for growth and reproduction, this Certainly these cases are somewhat extreme choice of release point and direction will and not representative of normal operating result in a very high percent of population conditions. However, they do dramatically effective kill. demonstrate the potentail danger of en­ trainment. The question of whether this Zooplankton and Small Invertebrates: offshore, submerged solar power plant Discharge will have little effect on this could duplicate such kill rates is yet group, especially for those in the warm to be definitely answered. With con­ water dischRrge. A significant number siderably less dense populations out of of the more sensitive species in the cold the shore/estuarine areas and especially water flow will undergo some degree of with the low density populations at the shock to the ll°F temperature rise if that 1000 ft depth (Sverdrup, 1942), the outflow mixes fully with ambient waters. same entrainment force would entrain (Clark and Brownell, 1973). fewer organisms. However, while many shorebased plants use intake velocities Large Invertebrates and Vertebrates: in the .8 to 1.2 fps range, this plant There will be little if any reaction will use a 2+ fps intake for the warm to discharge by species in the warm water water flow and a 4 fps velocity for the flow. Some, more sensitive species in the cold water intake flow. This will sig­ cold water flow will undergo a numbing nificantly increase the attractive power type of shock, or disability, at the su­ of this plant. Available data indicates den temperature change associated with the start of a sharp upward trend in the discharge. Compared to other effects of percent of available fish entrained at the plant on species of this group, how­ intake velocities of around 0.9 fps ever, this final effect will be relatively (Clark and Brownell, 1973). Further, minor. most shore based intakes are horizontally oriented, while the intakes for this A summary of these effects of entrain­ plant are vertical. It has been demon­ ment on each segment of the marine biota strated (Sonnichsen, 1973) that fish have is contained in Table 1. a natural ability to oppose horizontal

166 TABLE 1. ENTRAINMENT ENVIRONMENTAL IMPACT SUMMARY

Environmental Element Cold Water Intake Warm Water Intake

Physical Net ~P = 310 psi, net ~T = 20°F Net ~P = 42 psi, net ~T = 2°F Net depth change = 700 ft. Net depth change = 100 ft. Net ~ time = 230 sec. Net ~ time = 42 sec.

Chemical Substantial salinity, pH, N, P, Negligible and 0 level changes after discharge ~' 0\ and mixing with ambient water '--1

Phytoplankton No phytoplankton present Light mechanical damage Light kill from ~T and ~P Severe kill from discharge below euphotic zone

Zooplankton and Moderate mechanical damage Moderate mechanical damage small invertebrates Moderate-extreme kill from ~P Minor kill from ~T and ~P and ~T Moderate impairment and shock

Large invertebrates Massive kills from mechanical damage Massive kills from mechanical damage and vertebrates Light kills from ~T and ~P Severe shock, exhaustion and impair­ Severe shock, exhaustion, and ment to living individuals impairment to living individuals currents, but not vertical. Lastly, the Conversely, screening designs to pro­ quantity of water passing through this tect local marine organisms are, in plant, 7.Sxlo3 ft3/sec per intake, is general, screening over and above that much higher than for conventional plants. required for plant protection. Such screening may consist of more elaborate Whether or not these factors balance, or more extensive mesh networks or some or overbalance, the population reduction provision for directional stimulation at the plant site is not known, and is and intake escapes. These devices, how­ an appropriate subject for further on ever, represent diseconomies, or extern­ site study. For the present it seems alities, to economic power production fully appropriate to assume that the at the plant. Additional dollars spent potential exists for large marine for this type of screening will not pro­ organism entrainment damage, and that duce a return of either greater power this damage represents a viable problem output, or higher plant reliability. for plant design. Thus additional biota protection screening represents an internal cost with an exter­ To avoid the ill effects of this en­ nal benefit which cannot accrue to the trainment, screening devices are used to plant. There is no economic motivation exclude as much of the ma.rine population for this type of screening. Large screen as is physically or economically practical. fish kill figures attest to this lack of This report will present considerations motivation. Nonetheless, society as a for evaluating the limits and desirability whole does accrue at least a portion of of these practicalities, and screening the fish protection benefits. It is to design options to meet them. society's benefit to ~1ave the plant pro­ vide protective screening, and political DESIGN PURPOSE AND PROBLEMS and legislative pressures are being applied in that direction for all coastal The purpose of intake screening is in zone industries. This tradeoff between fact twofold, To this point, only envi­ cost reduction and fish protection is ronmental protection has been mentioned, manifested over a range of options in and this certainly is one of the purposes screen design. This report includes of intake screening. The other purpose discussion of the basic design type in is plant protection. This second pur­ this range. pose is the original purpose for which screens were introduced, and still the The screen designs presented in this prime motivation for screening. Screen­ range are not identical with comparable ing for plant protection consists of shore based facilities designs because the exclusion of any organisms or matter several unique problems are present at capable of damaging or clogging any part this plant which are not present at con­ of the power plant. The most vulnerable ventional shorebased, or even conventional element of the plant is normally the eva­ offshore intakes. These include: poration and condenser tubes and plant protection screening is geared to their 1. No free surface: Most screening protection requirements. Thus screen systems take advantage of a free water design is often taken as a function of surface for fish direction, exclusion, condenser tube material type and diameter. or for fish escape routes (Fair and The obvious importance of this type of Geyer, 1971). No such feature is present screening is that clogging of, or damage at either intake to this plant. to, these tubes reduces heat transfer on which the operation of the plant is based. 2. Temperature isolation: The sea The benefits from screening to protect solar power plant receives both heating the plant, then, are internal to the and cooling from ocean waters. The economic operation of the plant, and temperature difference between the heat represent a positive return on the screen­ source and its sink is thus only 20°F ing investment. or less. Once the cold water is entrained

168 at the 1000 ft depth, it must remain 2. Nekton: Nekton pose a threat to thermally isolated from the ambient the power plant in two ways: first they water outside the intake pipe. Thus may damage or clog some elements within the any fish escape mechanism for the cold plant, as pump blades, piping, or condenser/ water intake must maintain this iso­ evaporation tubes. This would reduce the lation while still allowing fish to efficiency of that element, and thus reduce pass from the cold water tube out. that of the entire plant. Second, Nekton can be impinged upon the screening device. 3. High intake velocity and volume: This reduces the net area of the screen and High intake velocities increase the head increases the head loss across it. Cer­ loss across the intake screen, especially tainly no one fish could create a signif­ for such fine mesh screens as will be icant increase in head loss; but impinge­ used at this plant. Further these veloc­ ment of even small schools of fish could ities increase impingement on the screens. easily create such a loss. Moreover, it The high volume flows require larger has been demonstrated that, when confronted screen systems which increase power with sudden velocity and current direction consumption of the screen system and changes, fish tend to align with and remain reduce plant power output. aligned with that gradient (Sonnichsen, 1973) Thus the intake area of a plant will tend to 4. Differing local environments at be a congregational point for local popula­ the 200 ft and 1000 ft levels will result tions. This tendency, combined with the in differing screening criterion for the previously mentioned inability of fish to warm and cold water intake screens. resist vertical currents, could tend to increase the percent of locally available SCREENING REQUIREMENTS fish pulled into the intake apparatus, and thus increase impingement and associated Screening requirements for plant pro­ losses. tection will be considered as mandatory requirements for any screening system. 3, Plankton: In general, plankton (both The impact of additional measures for phytoplankton and zooplankton) are of such marine biota protection may then be small size as to represent no threat to the evaluated by the added complexity and plant (Hill, 1965 and Sverdrup, 1942). cost of the screening system. There are, however, a substantial number of zooplankton species sufficiently large Requirements for plant protection to pose a threat of clogging to screening must first be viewed by condenser/boiler tubes at this plant. answering, "Protection from what?" Screens designed to exclude nekton from Certainly, in general it is protection the plant should exclude these species of from the marine environment, but the zooplankton equally well. However, it must specific elements within that environ­ be remembered that, lacking the ability to ment from which the plant must be pro­ resist any current, these zooplankton will tected include: definitely be impinged.

1. Debris: While debris screening 4. Biofouling agents: The biofouling (trash sacks) are an integral part of problem is a very important one for this shorebased, surface intakes, debris can­ plant and is dealt with in a separate report not be considered as a threat to this by T. Heinecke. plant. The two intakes for the plant are each several hundred feet away from 5. Plants: Large sea plants, such as an ocean boundary (bottom or surface). kelp should not pose a threat to this plant As debris will either float on the sur­ as these forms tend to be coastal zone face or tend to sink to the bottom, the and/or surface layer inhabitants and are probability of debris being present in found in large quantities only in these the vicinity of either of these intakes areas (Raymont, 1967). Stray plants is sufficiently low so that the low risk approaching the warm water intake would be does not seem to justify protection impinged upon the intake screen. specifically designed against it.

169 Now knowing what is to be screened, 1. Millstone Power Plant, Conn: the next question is how to screen it. kill of over 2 million menhaden in A current standard criterion for plant 1971 (Clark and Brownell, 1973). protective screening is that the screen must not allow penetration of any matter 2. P.H. Robinson Power Plant, Texas: which is greater than one half of the 7.2 million fish impinged in 12 months condenser tube diameter (Sonnichsen, (69-70). 1973). As the diameter for the sea solar power plant is 1/4 inch, the screens must 3. Suny Power Station, Va: 6 million exclude everything larger than 1/8 inch herring killed in 2-3 months (1972). in diameter. This requirements is much more stringent than that for conventional The conclusion by Clark and Brownell was plants which often use 3/8 inch mesh that, "Screen kills are a major and screens (Clark and Brownell, 1973). Fur­ growing problem with large power plants ther, this requirement excludes bar located in estuaries using once through screens as a potential main screening cooling ... " Thus inadequate screening device. In order to exclude everything can easily do as much harm as good from with a dimension greater than 1/8 inch an environmental viewpoint. Design these bars would have to have gaps criterion to improve the environmental around one third that width or 1/24 protection capability of these screens inch, as a common height to breadth by marine biota groups include: ratio for many juvenile species is 3 to 1 (Sverdrup, 1942). Thus the prime Plankton: Screening, in general, can­ screening device will be 1/8 inch mesh not be designed to offer any protection screen. Monel wire is recommended for to plankton. Lacking a true swimming its corrosion resistant properties in capability plankton will be pulled into this environment, and is commonly used the plant if the mass of water they for shore based intake screens (Sonnichsen occupy is pulled in. To exclude even 1973). In addition to this screen, larger the larger species of zooplankton merely bar screens may be used to exclude any­ results in their impingement and near thing sufficiently large to damage the certain death on the screen.(Clark and screen. Lastly, this sort of screen is Brownell, 1973). As it is, this large often either equipped with a rotating class of zooplankton fare best during scraper or is a traveling screen with entrainment. Screens represent a net stationary scrapers so as to remove "bad" for the plankton class regardless accumulated impinged material. of the type of screen. They would be better off with no screen at all. In order to now provide some addi­ tional measure of protection for those Nketon: It is possible through direc­ marine organisms pulled into the intake, tional motivation measures to appreciably we must first define the consequence of affect the probability of kill for members the type of screening system just defined of the class. Such control measures on the various organisms in the marine include: velocity, temperature, physical environment. While these screens will barriers, light, electric shock, and exclude fish and larger invertebrates others. These may be combined to form from the plant and thus prevent inner a wide range of directional stimuli for plant kills, they do not automatically fish. The Bonneville Power Authority reduce fish kills. In fact, fish kills has conducted extensive testing in this by impingement on, or damage from in­ area with salmon. Other similar research take screens have been as devastating is summarized by Sonnichsen (1973). While as the inner plant kills these screens this research shows some of these stimuli were to prevent. Examples of such mass­ measures produce either inconsistent or ive fish kills include: non-uniform motivational results, the

17C effects of partial physical barriers, such dieted vertebrate size distribution, as screens, combined with sudden velocity will be larger than the mesh size re­ gradients produce unifrom predictable re­ quired to protect the plant. To match sults. Further, these phenomena are readily that 1/8 inch mesh size, the controlling available at the sea solar power plant. fish size would be less than 2 inches in Sonnichsen also details the application of length and 0.4 inches in depth. Cer­ this result into the angled barrier concept, tainly there is a full spectrum of biota shown in Figure 2. The basis of this con­ sizes in any sector of the ocean. How­ cept is a fish's natural tendency to align ever very few organisms of this size perpendicular to and pointing away from the range will be found at a depth of 1000 ft, barrier. and a very small percentage of the verte­ brates in open waters. Thus if the mesh Another concept potentially applicable is maintained at 1/8 inch for plant pro­ to this plant is the establishment of a tection, we are virtually guaranteed of screening line outside of the influence near total vertebrate exclusion from the are of the intake. Any organism at such plant, and the entrainment damages to a screen would not feel any influencing vertebrates mentioned earlier may be force from the intake current. This con­ avoided. cept would result in an extremely larger spherical screen around the intake, and SCREEN OPTIONS presupposes that most, if not all, fish under the influence of only the natural There are substantial differences in currents, will, when presented with a the environments and in the marine pop­ spherical screen mesh in that current, ulations at 200 ft and at 1000 ft depths be capable and willing to circumvent it in the Florida Current. Due to these in their natural meanderings and migra­ differences it will be easier to con­ tions. Our literature search disclosed sider screen options for each intake nothing to either substantiate or refute separately. This is not intended to be this assertion. an exhaustive list but a list representa­ tive of the various major types of As was true with plant protection screening options and trade offs. requirements, mesh size is critical to proper fish exclusion. Normal mesh size Warm Water Intake Options: criterion to exclude fish in power plant design is given by: 1. No screen: This represents a "least initial cost" solution. As stated M = .04 (L-1. 35) F 5::;Fs6.5 ...... (1) this plan would also benefit plankton and classes. However, increased real cost M .03 (L-0.85)F 6.5::;Fs:8 ...... (2) due to increased risk to evaporator/ condenser tubes is far greater than the where M = mesh size dollar savings in initial costs. This L = fish length in inches does not appear to be a viable solution D = fish body dpeth irt inches unless some new pumping design can be F = L/0 = fineness ratio found which will guarantee break-up of any matter entering the plant greater For example, for a fish 15 inches long than 1/8 inch. Even with such a new with 3 inches of body depth, F = L/0 pump, the no screen solution will not 15/3 = 5. Thus equation (1) applies and, reduce fish kills, and so is rejected as a potential screening plan. M .04 (15-1.35)5 M = 2. 7 inches 2. Bars only: A bar screen consists of parallel bars placed over the intake Initial site population study indicates entrance. Normal dimensions for these that the mesh size required to exclude fish, bar screens on shore based intakes are using the above equation and based on pre­ 1/2 to 5/8 inch bars at 4 inch to 4 1/2

] 71 I I I I I eylI I

for 8 < 45°

Vc = current velocity Vs = fish swimming velocity V = resultant actual velocity

FIGURE 2. Physical Barrier Direction of Fish

172 inch bars at 4 inch to 4 1/2 inch centers. gross aTea across the screen where a g As the sea solar power plant does not have and, a = net area across the scTeen. to plan for large debris and suTf zone n foTces, these dimensions could be Teduced Thus, a = (75')(75') for a 75 ft squaTe g to 3/8 inch baTs at 3 inch centeTs. Head screen 2 loss acToss the baT scTeen may be calcu­ or a 5625 ft lated through a numbeT of methods. g and a = a -(area of bars) Applicable formula include: n g

4 If the bars are on 3 inch centers then h = S(w/b) /~vsin8 (Fair & Geyer, there are 1971) ...... (3) (75 ft)(l2 ft/in) where h = head loss = 300 bars w max. width of bars = 3/8 in. (3 in/bar) b = minimum spacing between thus, bars = 2 5/8 inch an 5625- 300 (3/8)(1/12)(75) 8 = the angle between the screen and the flow = 5625 - 352 2 and S = a coefficient dependent on the a = 5273 ft shape of the bars. n then, S values vary from a high of 2.42 for rec­ a /a = 5273/5625 = .937 tangular bars, to 1.79 for circulaTe bars, n g and to a low value of 0.76 for "tear drop" shaped bars. In order to minimize head from equation (5), loss, tear drop shaped bars (semicircular 2 facing the current tapered to small swmi­ Kt = 1.45 (.45)(.937) - (.937) circular end facing downstream) will be = 1.45 .421 - .878 used and S = 0.76. As indicated in Figure 3 however, the orientation of this baT screen ' Kt = .15 to the actual flow direction, when that flow arrives at the screen, is not a con­ and from equation (4) using a 4 fps stant and in fact varies from near 20° up stream velocity, to 90°. FaT approximate calculation pur­ 2 h Kt vn /2g = .15(42/64.4) poses, a mean value of 45° may be used. 1 Then with 8 = 45° from equation (3), hL = .0384 ft 1 4 3 h = 0.76 [(3/8)•(21/8)- ] / . 4 sin(45°) for an intake velicty V = 2 fps,

hL = .149 ft hL = . 0096 ft.

A second method, and more consistent with The head loss figures by this second other available data, is one proposed method will be used from this point on. by the U.S. Department of Interior. Their criterion is: An additional head loss is associated 2 with this and all subsequent designs. The basic intake design for this plant hL = Kt g ...... ( 4) ~n approximates an inward projecting pipe into a reservoiT, the ocean. Associated where water velocity acToss the with this device is a K value of 1.0 vn scTeen (Fairbanks, MoTse, 1959). From equation (4) this yields an h = 0.062 ft. It and, l.45-0.45(an/ag)-Can/ag): .. (5) 1

'77; 1 I~ ANGLE OF WATER CROSSING BAR SCREEN

lJ ---+­ SCREEN

PLANT

FIGURE 3. Current Patterns Across Horizontal Bar Screen

174 is not known how the addition of a 2 fps We have already established a head loss current perpendicular to the intake will for the bar screen. affect the distribution of this loss. It is very probable that it will absorb K = 0.15 some of the loss, and possible that it bar screen will absorb essentially all of it. In To find a and an for use in equation (5) either case the resultant hL associated for the scre@n the mesh must first be de­ with the internal pumping system is small fined. The 1/8 inch mesh has 1/64 inch and is identical for all intake screen thick monel wires surrounding 1/8 inch systems. Further research is required square gaps. This wire thickness is some­ to evaluate the actual value of this loss times used in larger meshes (Clark and and it will not be included in the cal­ Brownell, 1973) and is used here to provide culations for any of the following greater strength and durability. Taking a screen systems. As previously 9 inch by 9 inch unit area and letting mentioned, a bar screen system alone N = the number of these 81 sq. in. areas will not provide the exclusion required in the mesh we have: for plant protection. This screening technique therefore cannot be considered a = (9)(9)(N) = 81 N in2 g as a principal screening device. a = N(81) - [area of wires in one 3. Stationary screen with rotating n direction + (area of wires in scraper: This type of plant intake second direction - area of junction)] screen is a fairly popular one with con­ or, ventional power plant intake designs and a N(81) - [(64 wins) (9 in) (1/64 should provide adequate plant protection n inches/wire)+ 64 [(9)(1/64)-64 for the sea solar power plant. This (1/64) (1/64)]] system consists of circular monel 1/8 inch screen mesh over the intake with a = 64N in2 a multiple blade rotating scraper op­ n erating over it. For this system then 1 a /a = 64N/81N .79 n g 4000 ft 2 of the mesh would be required for the 75' circular warm water intake. and from equation (5), Operating costs in the form of power 2 requirements for the scraper motor are Kt = 1.45 0.45(.79)-(.79) also introduced with this system. How­ 1.45 .355 - .624 ever this power requirement should re­ main less than 1 KW which represents K h = .47 0.025% of the output power of the plant. mes Considerably more power will be used for K = K + K = .15 + .47 total bar mesh lighting the crew quarters. The cost, then, of this system remains extremely Kt = • 62 low compared to the benefits it provides in terms of plant protection. This then from equation (4), screen, however, does nothing to pre­ 2 vent fish kills. It has been stated hL = .62 V /2 g that fish will tend to congregate near these intakes, and that kill rates from for V = 2 fps at warm water intake, this type of screen can be high. This n is the borderline then between mere hL = . 0386 ft plant protection, and plant and environ­ mental protection. 4. Angled traveling screen: The place­ Normally a bar screen would be employed ment and general operation of this screen to protect the mesh from damage by large is shown in Figure 4. The diagonally fish or objects. Head loss for the total traveling 1/8 inch screen mesh provides system may now be calculated. adequate directional stimulus to direct

175 L I • 75{"J BAR SCREEN T / 40 ....

1 I I

I ' Vc =·CURRENT VELOCITY I V5 .= FISH SWIMMING VELOCITY 187 70

' V = NET MOTION

' ,_. . 1 '-l - 0\ 75

\. j

~

•J FIGURE 4. Traveling Warm Water Intake Screen System most fish to the downstream (back) end This system should furnish adequate of the screen well where a horizontal marine organism protection. However this fish escape is located. It will be protection is purchased at prices which remembered from Figure 3 that the cur­ includes: rent across the bar screen at the top of the screen well is not a vertical Construction cost: This screen system current except at the back edge of the uses 15,300 ft2 of monel 1/8 inch mesh well. Thus, when a small fish first instead of 4000 ft2 used by the stationary penetrates the bar screen and begins to screen. Further this screen system requires align with the mesh screen and velocity roughly 13,000 ft2 of additional wall con­ gradients in the well, the natural cur­ struction for the screen well and escape tube rents will force him toward the back of and will require construction of a screen the screen well. The farther back in support and screen drive system. This the well a fish goes, the more vertical screen well will also increase current is the current attacking him. The fish's forces on the structure and thus result in inability to withstand this current forces increases in the mooring and anchoring him deeper into the well. Eventually he system. It must, however, be realized that will be forced toward the lower rear wall these costs represent a small part of the where he will pass beyond the back wall total plant costs. of the screen well and out of the vertical current to the escape tube where he is Operational costs: Operational costs once again in a horizontal current forcing may be divided into two categories. The him out of the intake. first of these is screen drive power con~ sumption. No exact figures are available It is assumed that horizontal velocity for this power requirement, however 5KW components of the flow as it enters the is surely a liberal estimate. Again, screen well from the upstream side will this figure represents 0.125% of the total create a positive relative pressure at the output, and still less than crew quarters head of the escape tube, which will result lighting requirements. The second of in a net downstream, or escape, flow. these categories is added head loss. This Actual flow modeling would be required to added head loss is derived from the fact substantiate this assumption. Should such that the intake flow must cross the screen modeling reveal a net upstream current twice (see Figure 3) before it enters the through this tube, either modified bucket plant. scraper systems could be adapted to use as scraping and pumping devices to force Thus Kmesh total = 2 x Kmesh 2 X .47 a downstream flow (Sonnichsen, 1973), or water jets could be added for the same or Kmesh(t) = · 94 purpose. Total hL then is derived from Kt = ~ar Certainly this method of fish direction + K = .15 + .94 will not work in every case. Some verte­ mesh(t) brates, invertebrates, and all planktonic forms will still be impinged on the screen. or Kt = 1.09 As the screen moves toward the lower back From equation (4), edge of the well, it passes under the back wall of the well before reaching the turn­ 2 2 ing sprocket and stationary scraper blades. hL = Kt Vn /2g = (1.09) V /64.4 At this point, without the direct vertical using V = 2 fps, current influence some vertebrates will n escape the screen themselves and enter the escape tube. The remainder will be hL 4.36/64.4 scraped off the screen and carried away from the plant by the downstream current. hL .0678 ft Small debris remaining on the screen will While this is an increase of .029 ft in hi! be removed by the intake current. it is still within the limits of the planf pumping potential. One additional benefit of this This relatively high K value would seem screening system, covered in more to render this system less desirable detail in Annex 1, is that it provides than that shown in Figure 6. This system an additional 40 feet of vertical sepa­ uses a cylindrical, horizontal intake ration between the warm water intake under a solid intake well cap. By allowing and discharge. This added separation intake flow from all sides the internal could be beneficial in reducing the 90° elbow is eliminated. By use of a probability of recirculation at the horizontally rotating screen and either plant. Complete plant flow modeling scraper of water jet system with a pro­ would be required to determine the ex­ tected fish escape on the downstream side tent to which these 40 feet were needed. of the intake adequate environmental pro­ tection can be provided. This traveling, angled screen system still meets all requirements for plant protection; and, for the added costs Costs associated with angular and listed above, will provide greatly cylindrical system construction and superior environmental protection. It operation are shown in Table 2. would appear that this trade off is a good one as the total net benefits are Finally, the rectangular system will high and the costs moderately low, even provide a greater increase in total plant though these benefits do not accrue to drag force and thus result in a larger the plant itself. increase in mooring and anchoring require­ ments. 5. Horizontal intake: The use of a horizontal intake would eliminate verti­ Either of these screen systems will pro­ cal intake currents associated with other vide both adequate plant protection and systems and thus remove a major cause of adequate environmental protection. Their fish entrainment. Two possible designs total costs are similar in magnitude to for such an intake are shown in Figs. 5 &6. the angled traveling screen system, as Figure 5 shows a single rectangular hori­ are derived benefits. zontal opening facing the local current with a vertically traveling screen assem­ 6. Ball screen: as previously men­ bly. Two drawbacks to this design are: tioned, and as shown in Figure 7, this 1) A 90° elbow is added to the internal screen is based on the principle that if piping system with an associated K value marine biota are prevented from entering of 0.8; and 2) as demonstrated earlier the influence area of the intake current with the Millstone, P.H. Robinson, and they will neither be attracted to it nor Surry power station screen kill figures, be impinged upon the ball screen. The all of which were based on horizontal ball screen would be centered over a intake flows, the elimination of aver­ . circular intake opening between 1/2 and tical intake current alone does not 1/3 radius above the intake. The ball necessarily reduce fish kill rates. radius is estimated to be approximately Through the use of a downward traveling equal to the intake diameter, or 75 ft. screen (see Figure 5) and an adequate With an average natural current of approx­ fish escape system at the bottom of this imately 2 fps at this depth (Sverdrup, screen, the second drawback can be sub­ 1942) and with an intake velocity also of stantially reduced. However the first 2 fps this size seems more than adequate. cannot be reduced and results in a total Only plant flow modeling can accurately K value for the screening system of 1.89* define the limits of intake influences under various actual current conditions. *K = 1.89 derived from summation of Quite probably the final screen shape K values for bar screen (0.15), twice that would deviate from spherical due to local for the 1/8" mesh screen (2x 0.47) (the current influences. Mesh size of this flow must cross the screen twice), and a screen would be 1/8 inch. 90° elbow (0.8).

178 -7o'-l -t 401 1

FIGURE 5. Vertically Traveling Screen with Horizontal Intake.

179 FIGURE 6. Horizontal Traveling Screen with Horizontal Intake.

180 BALL MESH ~ SCREEN

OUTFLOW r..----'A'------..,

FIGURE 7. Ball Screen Design

181 TABLE 2. HORIZONTAL INTAKE CONSTRUCTION COST COMPARISON

i Construction Parameter Rectangular Intake Cylindrical Intake

1/8" monel mesh 11,000 ft2 9,400 ft2 wall construction 22,500 ft2 4,500 ft2 screen support minor cost major cost item screen drive system relatively simple more extensive &complex power requirements approx. same as option #4 approx. same as option #4

The costs for this form of environ­ Cold Water Intake Options: mental protection include: Before discussing actual options for Construction cost: If a spherical the cold water intake screen a brief shape with 75 ft radius is assumed, this discussion of the 1000 ft depth environ­ screen requires 69,400 ft2 of mesh as com­ ment and its population is appropriate. pared to 4,000 ft2 for the stationary The population at the 1000 ft level is screen, and 15,300 ft2 for the traveling void of phytoplankton (Sverdrup, 1942; screen. In addition, some screen support Hill, 1965) It also has a small zoo­ system would have to be constructed and plankton population. Even though a large this increased plant weight would have number of species, including, as an example, to be accounted for and countered. over 30 species of crustaceans, the total number of biota present is fairly small. Operating costs: A plus for this Nektonic populations are also somewhat screen system is that there are no asso­ reduced in total numbers of representatives ciated operating costs. As the screen at this level, even though almost every is outside of the influence of the intake, species is capable of existence there. the loss across the screen will not be Moreover, nekton at this depth do not absorbed by the intake system. The nat­ tend to "school" and 1000 ft depth popu­ ural currents will absorb this loss. lations are made up of individuals or There are, however, two operational prob­ small groups of individuals; thus the lems associated with the ball concept. threat of sudden mass impingement is First is biofouling. As this screen greatly reduced. would be well within the euphotic zone biofouling agents would be free to attach The natural current at this level is and grow on it. In the long run this re­ much lower (0.9 fps) than at 200 ft and duced screen net area would force the in­ the design intake velocity is higher take system to pull water across the (4 fps) due to the smaller intake pipe. screen. The second problem is, in essence, Thus the area of influence of this intake a solution to the first. This is cleaning. will be larger than that of the warm Periodic cleaning will control biofouling. water intake. Finally, game and com­ However, cleaning of this screen presents mercial fish do not tend to populate such several problems of its own, including depths. It appears then that the net size and location of the screen. It is change from 200 ft to 1000 ft is to re­ assumed that some economical cleaning duce the benefits of environmental pro­ system would have to be developed to tective screening by reducing both the make this screen effective for the warm population to be protected and its direct water intake. value to man.

182 From this basis, cold water intake minimal sessile population. Thus screen options are: cleaning requirements would be minimal and cleaning could be scheduled during 1. No screen: While this option is major plant shutdown and repair periods. somewhat more attractive here than at the warm water intake, its minimal cost savings This screen system entails no opera­ are still vastly outweighed by the economic tional costs and no operating parts rsik of damage or clogging to condenser with associated risk of failure at a tubes. In general, even large fish lack 1000 ft depth and difficulty of main­ the ability once trapped in the intake tenance or repair at that level. pipe to resist the vertical current and escape out the bottom (Sonnichsen, 1973). Thus the ball screen is more attrac­ Thus no screening provides few benefits, tive for the cold water intake than high risks and is still an unsatisfactory at the warm water intake and appears to option. be a plausible system for the lower screen. 2. Bar screen: A bar screen across the cold wate.r intake similar to that described 4. Mesh screen with rotating scraper: for the warm water intake would certainly This system would place a bar screen at exclude most organisms at this depth. How­ the intake entrru1ce and a horizontal ever, they would allow a steady, low volume, mesh screen with rotating scraper in the flow of fish larger than plant protection cold water intake pipe. It would be requirements will allow. If the decreased benifical for the mesh screen to be as cost, and ease of operation of the screen near to the plru1t as possible to facili­ can justify the potential requirements for tate maintenance on the scraper motor significantly more frequent plant shut downs and screen assembly. However, this for condenser cleaning, this may be a viable endru1gers the required thermal isolation alternative. It does not appear at this of the cold water flow as an exit port time that it is. Further, use of a bar is required for scrapings and for a fish screen only allows no provision for reduc­ escape. One solution is to equip the tion of impingement or for screen cleaning. escape port with a pump or with a water Periodic cleanings are extremely imprac­ jet system to prevent warm ambient waters tical at the 1000 ft level, and the ex­ from entering the cold water flow. pense to install an on-site cleaning Either of these devices would also assist system negates the one real advantage of in jettison of mesh scrapings and in fish a lone bar screen. In either case, a lone escape. The several disadvantages of bar screen does not appear adequate. the system include:

3. Ball screen: A modified ball a. Locating the mesh screen assembly screen based on the criterion that intake at plant level means entrained biota influence at the screen will be "minimized" will rise 700 ft before screening. The instead of non-existent, could be an appro­ full effects of such a rise have been priate solution to the cold water screening described earlier. In summary, they are requirements. This change in size criterion all detrimental to entrained orgru1isms. would counter the tendency of an increased The result is that mechru1ical damage at influence area of this intake to expand the the screen will be increased as will ball screen still larger. The ball screen scraper damage ru1d damage from the jettisor would offer the same advantages of both system. This problem may be overcome by plru1t and expanded environmental protec­ locating the screen assembly at the 1000 ft tion it did for the warm water intake. level. However, this additional environ­ Biofouling is not a problem at this depth, mental protection brings with it a re­ and impingement would be minimized by the quirement to provide increased reliability lower population level especially by the for the scraper drive and jettison assemblies.

183 b. Screen head loss: As a result of considerably lower than at the warm water the increased velocities in the cold water intake. While this is a perfectly good intake pipe and of the stringent plant pro­ screening system, the high construction tection requirements for mesh size, head cost and high cost of insuring long term loss across the screen is significantly system reliability may be higher than the increased over that of the warm water in­ total returning benefits of environmental take. If either the mesh requirement protection. Further on-site population (reducing screen K values) or intake ve­ study is required to better evaluate this locity could be reduced, screen head loss trade off. would be significantly lowered. This relationship is shown in Figure 8. 6. Angled traveling mesh screen: This screen would be structured similarly c. Power consumption would also be to the one for the warm water intake, and increased with this system with both would either be located just before the scraper drive and jettison systems in entrance to the plant or at the pipe operation. However, construction costs entrance. If it were located adjacent would be reduced from those of the ball to the plant, the added expense for screen as only 1,950 ft2 of monel mesh directional stimuli would essentially will be required. be wasted, since, as mentioned above, fish arriving at that site are severely This system provides adequate plant impaired, and, in general, would not protection. Environmental protection is respond properly to the stimuli (Sonnich­ somewhat reduced, but environmental damage sen, 1973). The additional costs associ­ should not significantly increase as a ated with locating this screen at the result because of reduced local popula­ cold water intake entrance are prohibit­ tion levels. ively high for the increased benefits associated with the reduced local popu­ 5. Horizontal intake: Addition of a lation levels. This screening method horizontal intake similar to those des­ then seems to represent environmental cribed for the warm water intake would "overkill" for the cold water intake and improve environmental protection at the is not recommended. cold water intake over the previous plan. Such a horizontal intake screen would A summary of potential screen systems have to be located at the intake entrance for each intake is shown in Table 3. (1000 ft) to avoid bringing fish under the influence of the vertical intake flow. CONCLUSIONS: This intake screen, as described for the warm water intake, will provide adequate l. Initial entrainment is a function protection for the cold water intake local of intake velocity and orientation. The environment. However, the cost of either vertical intakes, and high intake veloc­ type of horizontal intake screen is sig­ ities associated with the plant will sig­ nificantly higher than that of the sta­ nificantly increase the number of organ­ tionary screen system. Complexity of the isms entrained at both intakes. screen drive mechanism is also signifi­ cantly higher, especially for the cylin­ 2. Cumulative affects of entrainment drical design. Thus reliability goes down on the living biota of the natural environ­ and risk of failure rises. Further en­ ment include: . ' v1ronmental protection at this level isn't worth as much as it is at the warm Phytoplankton: Light to moderate water intake. There are many fewer total mechanical damage from screens, pumps organisms and few, if any, game or com­ and boilers; light kill rates from mercial catch species present. Thus the pressure changes; moderate impairment total benefit of environmental protection from pressure and temperature changes; beyond plant protection requirements is complete cessation of growth and repro­ duction, and large kill rates from location and direction of discharge.

184 .20

.18

.16

i= .14 LL

.J ..c: .12

.10

.08

.06

.04

.02

0 2 3 4 5 6 INTAKE VELOCITY ( F PS)

FIGURE 8. Screen hL as a Function of K Values.

185 TABLE 3. PLANT INTAKE SCREENING OPTION SUMMARY

Screen System Cold Water Intake Warm Water Intake

Bar screen Inadequate Inadequate Stationary screen Probable optimum Adequate plant protection with scraper Inadequate biota protection Ball screen Acceptable Impractical; excessive biofouling Horizontal intake Acceptable; may have Acceptable screen excessive cost Traveling screen system "Overkill;" excessive cost Acceptable

Zooplankton and small invertebrates: been achieved, additional dollar expen­ Moderate to extensive mechanical damage ditures, as both initial investment and from screens, pumps a.nd boilerI condensers. as operational power consumption, may be Minor to moderate kill rates and extensive invested to provide increased marine biota shock and impairment from presure and protection. For this plant the required temperature changes. Net effect: this increased investment is relatively small class should fare better than anyother, for a major increase in biota protection. however, a majority of entrained organisms will still undergo death or severe impair­ 4. Differing environments at the two ment before discharge. intakes create different screening design criterion for the two intakes. As a result Large invertebrates and vertebrates: different screen systems appear as accept­ Under normal operation screens will ex­ able for the two intakes. Acceptable clude essentially all of this group. systems for the warm water intake include Kill rates and damage at the screen are the angled traveling screen system and a function of screen design. If this horizontal intake system, while the cold group is allowed to be entrained severe water optimum appears to be either a modi­ mechanical damage would result to most fied ball screen, or a stationary mesh organisms. In the vast majority of cases screen with scraper and associated bar this damage will lead to death. For the screen. remainder, light to moderate shock should be experienced from pressure and temp­ 5. Additional research is required to erature changes, and most vertebrates will fill several important gaps in the avail­ suffer from exhaustion from attempts to able information. Areas indicated for oppose the intake currents. The net special emphasis include: effect will be that essentially all or­ ganisms in this group will be killed if a. Long term on-site population study entrained. Those who are not killed to determine population densities, moni­ will be moderately to severely impaired. toring values and size and age character­ istics for local environments at both 3. It seems economically essential to intakes. This study should also include have some form of screening at both the data on seasonal variations. warm and cold water intakes. After this minimum essential level of screening has

186 b. A current flow model study for the c. Additional study on motivational plant. This study would include effects stimuli response emphasizing species of warm and cold water intakes and outflows prevalent at this site. on local circulation patterns, potential recirculation currents and their prevention, d. Expanded investigation in the and a definition of the area of influence effects of entrainment of various species for each intake. Data should be collected through the various components included for natural high, mean, and low current in a sea solar power plant. velocity levels.

REFERENCES

Clark, J. and W. Brownell. Electric Power Plants in the Coastal Zone: Environ­ mental Issues. American Littoral Society Special Publication #7, October 1973.

Curl, Herbert. Discussions. School of Oceanography, Oregon State University, Corvallis. April 1974.

Fair, G. and J. Geyer. Elements of Water Supply and Waste Water Disposal Systems. New York: John Wiley and Sons, Inc. 1971.

Fairbank, Morse &Company. Hydraulics Handbook. 3rd edition. Kansas City: Fairbank, Morse &Company. 1959.

Hill, N.E. The Sea, Vol. 2. New York: Inter Science Publishers. 1965.

Hirayama, K. and R. Hirano. "Influences of High Temperature and Residual Chlorine on Marine Phytoplankton," Marine Biology 7:205-213. 1970.

Ingle, R.M. Summary of Florida Commercial Marine Landings--1968. Florida State Board of Conservation, 1970.

Joyce, E.A., Jr. The Commercial Shrimp of the Northeast Coast of Florida. Professional Paper Series #4, Florida State Board of Conservation, 1965.

Moe, M.A., Jr. A Survey of Offshore Fishing in Florida. Professional Paper Series #7, Florida State Board of Conservation. January 1963.

Murry, J. and J. Hjort. The Depths of the Ocean. New York: Stechert­ Hoffman Service Agency, 1965.

Raymont, J. Plankton and Productivity in the Oceans. Oxford, England: Pergamon Press, 1967.

Sonnichsen, J., et al. A Review of Thermal Power Plant Intake Structure Designs and Related Environmental Considerations. National Technical Information Service, 1973.

l87 Sverdrup, H.V., et al. The Oceans: Their Physics, Chemistry and General Biology. Englewood Cliffs, N.J.: Prentice-Hall, Inc., 1942.

Thorson, Gunnar. Life in the Sea. New York: World University Press, 1971.

U.S. Department of the Interior. Design of Small Dams. U.S. Government Printing Office, 1965.

188 ANNEX 1

CIRCULATION AND RECIRCULATION CONSIDERATIONS

There are two questions which should be plant flow, 7.5 x 103 x 2 = 15 x 10 3 answered with respect to circulation and represents only 0.1% of the natural flow flow around the sea solar power plant. through this 1/12 mile area. Said dif­ These are: 1) Will the presence of this ferently, this means that 99.9% of the plant and its induced flows significantly water flowing through this 1/12 mile alter the general circulation patterns, wide sector will not be entrained into and if so, what area will this change the plant. Certainly more water than affect? And 2) Will the proximity of dis­ this will be influenced, and diverted, charge ports to intakes induce recircula­ as a result of the plant flows, but only tion patterns to form around the plant? those waters passing through the plant will undergo, or cause, any major shift Some perspective of size of the flows in circulation patterns. Thus we may will shed light on the first question. tentatively conclude that plant induced The Florida Current has a average net currents will not have a significant transport of 2.6 x 107 m3jsec, or 7 x effect on normal current patterns out­ 108 ft3jsec, spread over a 50 mile width side the immediate vicinity of each (Sverdrup, 1942). The power plant will intake and discharge. intake 25 x 103 ft3/sec through each of two intakes, as shown in Figure kl, and Data gathered for this study will only uses two separate discharges. Depths point toward a solution to the question associated with each activity are noted of recirculation. Sonnichsen (1973) has on the left of that figure. suggested that 60 feet of vertical sepa­ ration between intake and discharge is To compare these two flows we must sufficient to prevent recirculation for consider the area over which the plant conventional plants on lakes, Compared intake flows could possibly hold any to that situation, here the flows are influence. With a vertical intake an much larger than in a conventional plant, appropriate horizontal maximum influ­ which would require greater vertical sepa­ ence width would be on the order of ration. However, natural dominant currents twice the diameter of the upper, and are also present here which tend to reduce 3 to 3 1/2 times the diameter of the required separation. Finally, these are lower.intake on each side of there­ vertically oriented flows directed away spective intake. These differing from each other. This also would reduce ratios are a result of the differing required separation. natural current levels and differing intake velocities at the two depths. To what extent these factors counteract Widths of influence are then 5 x D, each other is not known, and is an appro­ or 5 x 75 = 375 ft, for the warm water priate subject for further research. intake, and 8 x D, or 8 x 50 = 400 ft, Should the increased flow criterion pre­ for the cold water intake. For conven­ dominate, the 70 ft vertical separation ience we may assume this influences between warm water intake and warm water 1/12 mile total width, or 440 ft. The discharge may not be sufficient to prevent transport of the Florida Current over recirculation pattern development. There 3 this same 1/12 mile = (1/12) (7xl0 /50) lies an additional advantage of the angled = 1.5 x 106 ft3/sec. Thus the combined traveling mesh screen for the warm water

189 FIGURE A-1. Plant Flow Patterns and Elevations

190 intake. This screening system would pro­ intake. Natural current forces will vide an additional 40 ft of vertical sepa­ provide adequate separation. Further, ration between these flows. as the cold water discharge ,port is horizontally displaced downstream from A second solution to this problem would the warm water discahrge and is dis­ be the insertion of horizontal stabilizer charging colder, heavier water, recircu­ plates on the sides of the plant between lation from the cold water discharge to the warm water intake and discharge. While the warm water intake will not occur if these plates would increase the drag forces recirculation from the warm water dis­ and weight loads for the mooring and anchor­ charge to the warm water intake can be ing system, they would provide additional prevented. isolation between the warm water intake and discharge ports. Thus it appears that recirculation v:ill not present a serious problem. However With 700 ft of separation between the the sensitivity of this plant to tempera­ cold water intake and discharge, there will ture fluctuations which could be caused be no recirculation into the cold water by recirculation indicate further study in this area is warranted.

191

SEA SOLAR POWER PLANT - BIOFOULING CONSIDERATIONS

by

Thomas Heinecke

ABSTRACT

Possible undesirable affects of bio­ position. If construction occurs at a fouling on a offshore, submerged struc­ nearshore site, biofouling will probably ture are studied; the types of marine occur. If the structure spends extended life to be expected, probable growth time on the surface for repairs, etc, rates of this life, and state-of-the-art problems may occur. prevention techniques are considered. Paints or coating are available with Only limited attachment and growth is protection capabilities up to and ex­ expected to occur once the structure is ceeding three years. Electrolysis tech­ at the selected site, in a submerged niques are available for protection of smaller, more sensitive equipment.

193

SEA SOLAR POWER PLANT - BIOFOULING CONSIDERATIONS

by

Thomas Heinecke

INTRODUCTION 1. Increased drag forces causing in­ For this report, biofouling can be creased demands on the mooring considered the attachment and growth of and anchoring systems. marine organisms on exposed materials. This usually causes a performance and 2. Increased weight, affecting the maintenance problem for structures flotation capabilities of the placed in a water environment. These structure. "structures" may range from ocean going vessels to timber pilings. For vessels, Less obvious, but significant problems a six-month growth of barnacles can that would also be encountered are: cause up to a 40% increase in drag or fuel consumption (Starbird, 1973). A 1. Increased corrosion (crevice and large tanker may have 15 tons of marine pitting). growth within a few years time. Pilings can be completely destroyed, if not pro­ 2. Increased headless within piping tected, within short periods of time by systems. marine borers. 3. Reduction of heat transfer Our particular concern is for the characteristics. effect of biofouling on the Sea Solar Power Plant. Physically it is a large, 4. Loss in general mechanical/struc­ , submersible structure, to be constructed tural efficiency. in a nearshore environment, towed to a chosen site and moored. The structure This report will approach the bio­ will be capable of controlling its buoy­ fouling problem through the following ancy characteristics. The two most im­ areas of concern: mediate problems that would be caused by biofouling are: A. The types of biofouling flora and fauna expected at the plant.

195 B. The critical marine environments 2. Hydroids for biofouling growth. 3. Tubeworms 4. Barnacles C. The probable organism growth 5. Sea squirts (Tunicates) rates, and relative importance of 6. Mussels the various organisms. Slime (bacterial and algal growth) can D. The present techniques used to be on most marine structures in a matter prevent or discourage growth. of a few days (Haderlie, 1968 and Dolgo Dovskava, 1969). This type of growth, E. Expected unique problems for the sometimes considered minor, can however proposed power plant. affect drag coefficients on ships and therefore, would affect our structure. This type of growth can get to be several TYPES OF FLORA AND FAUNA EXPECTED centimeters long. Another related prob­ lem is that this growth creates an envi­ Naturally the particular types of ronment attractive to other organisms marine life that would cause problems (mainly food) . would vary from site to site. This re­ port will be concerned with types of Hydroids, usually considered to be marine organisms which seem to generally littoral marine forms, have been found cause the more serious biofouling prob­ growing in depths up to 7000 meters. lems. All are found generally through­ Most of these organisms reach a maximum out the oceans. Again, the occurance is length of 20 centimeters, but some have a function of the water environment, been found up to two meters in length. (temperature, salinity, light, turbidity, current, food available, the attachment Tubeworms are usually the first major surface for sessile organisms, etc) typ­ animal to attach and start adult growth. ical of many fouling, sessile (attached) They may be found on structures in less organisms is the characteristic of having than two months. more than one form. Different physical forms usually occur for the following Approximately next in time are the stages: barnacles. Three of the more common species in U.S. waters are BaZams 1. Free swimming or floating Balanoides~ EZiminius Modestus and (nauplii stages) TubuZaria Larynx~ (over 100 species of barnacles cause fouling problems). 2. Period of settlement (cyprid Growth, in ideal conditions, can be up stages) to a few centimeters in height in less than a year. 240 feet is the approximate 3. Final growth and maturity (adult depth limit for many barnacles. stage) Tunicates or sea squirts, (a leathery­ The problem flora and fauna in a com­ texture shapeless animal) and mussels mon order of time sequence attachment (marine bivalve mollusks) also may cause onto a structure, are as follows (Love­ problems. As most of the literature grove &Robinson, 1966): available considers the algal and bacter­ ial growth, the hydroids, and the barna­ 1. Slime, algae and bacteria (Enter­ cles of greater importance, the emphasis omorpha and ectocarpus) Physical in this report will be on these particu­ form - brown and green weeds. lar organisms.

196 CRITICAL MARINE ENVIRONMENTS This material has been condensed into Table 1. The majority of the studies accom­ plished thus far state that the near­ Most of this information comes from shore environment is by far the "better" the California coast, with a bit from environment for the organisms mentioned England. Generalizing we can see that earlier. Some tests by NCEL of the barnacles, tubeworms, and mussels are Coast of California in greater than most predominately found in shallow 6,000 feet of water found only hydroids water, nearshore environments, growing and slime on test panels after 36 months in terms of one to two centimeters high (Muraoka, 1970). Shallow water (less within months, and with 100% coverage than 200 feet) is also desirable (Ray, of the exposed structure possible within 1959). Basically the shallow, nearshore 1 1/2 years. In deeper offshore waters, environment provides the best environ­ test panels showed a lack of barnacle ment for the organisms. and mussel growth (these panels were not exposed to a nearshore environment at Water currents are also important in any time). They did show a 100% algal providing the proper environment. In and bacterial coverage, and a 50% hydroid steady currents exceeding about 1.6 knots coverage within two to three years. (approximately three ft/sec), most ses­ sile organisms have difficulty in attach­ The majority of the reports emphasized ing to an object (Starbird, 1973). Bar­ the nearshore environment for the nacles, once attached however, can with­ following reasons: stand currents up to 12 knots before being dislodged. 1. Nearshore is considered to be the "worst case" location. Basically, the fouling organisms causing the majority of the problems 2. It is assumed that nearshore live and grow best in: characteristics could be related to deep water conditions. 1. Shallow, nearshore environments (a major exception is the goose 3. Nearshore, shallow-water testing barnacle, Lepas) is less expensive.

2. Euphotic zone 4. Common collection sites (buoys, platforms, etc.) are generally in 3. Currents less than 3 ft/sec. the near shore area.

It appears that once a site for a Sea PROBABLE GROWTH RATES, RELATIVE Solar Power Plant is identified, on site IMPORTANCE OF THE VARIOUS ORGANISMS studies should be made to pinpoint local biofouling characteristics. This section will primarily be a compilation of several reports, inclu­ The relation between biofouling and ding Haderlie (1968), Muraoka (1970), corrosion rates were considered by Walters (1966), and Thompson (1967). Muraoka (1970) and will be mentioned The intent is to indicate which marine here. Comparing heavily fouled shallow organisms can cause major biofouling water test panels to deep water lightly (and corrosion) problems at given fouled panels, the corrosion rate of depths and distances offshore. Also steel and aluminum was two to four times included will be the average growth greater on the heavily fouled panels. rates and sizes of various organisms. The lightly fouled panels were corroding

197 TABLE 1. GROWTH RATE OF ORGANISMS ON METALS AT VARIOUS DEPTHS AND LOCATIONS

Off Individual Growth Organism Location Depth Near No. of Organisms Shore Shore Rate

Algae, Bacteria Calif. 50'-100' X 30cm long/mo. 100% coverage/8 mos. Algae, Hydroids Calif. 25' X 100% cov./70 days I Hydroids, Anenomes Calif. 60' X 100% cov./18 mos. ! Barnacles Calif. 100' X 13mm high/3 mos. 10 organ./mo./sq.ft. Tubeworms, Barnacles, "-' \.0 Mussels Calif. 25' X 100% cov./1 yr. 00 !z" dia./ 2/3 yr. Barnacles England X 1 organ./sq.cm./day Barnacles, Mussels Calif. 60' X 90% cov./18 mos. Barnacles Calif. X 14gms/day/sq.meter Hydroids, Slime Calif. 6800' X 100% cov./3 yrs. Bacterial Slime Calif. 6000' X 100% cov./3 yrs. Hydroids, Anenomes Calif. 200' X 50% cov./21 mos. Barnacles, Mussels Calif. 6800' X 0% cov./3 yrs. Barnacles Calif. 200' X 0% cov./21 mos.

~------·-···------­ ----­ ---­ ------·-···----­ ------­ ----·-· ------­ at about twice the rate of the control would be detrimental to the use of the panels, (in a sterile sea water environ­ area, and where coatings might also ment). Therefore biofouling does con­ affect usage (radio antennae, radar, tribute to corrosion (primarily by en­ etc.). Anodes and cathodes are placed hancing crevice and pitting corrosion). at close intervals (two to ten feet), either as point sources, or as strips, and D.C. or A.C. currents are induced. PRESENT TECHNIQUES USED TO PREVENT OR A thin layer of chlorine at the surface DISCOURAGE GROWTH of the metal is sufficient to inhibit growth. In approximately two knot It should be apparent that the pre­ currents, two ppm to ten ppm free chlo­ vention of biofouling is an important rine at the source seems to give about design consideration. A few of the 0.1 ppm to one ppm protection, depending possible techniques that could be used on the surface shape, turbulence, etc. to prevent or retard biofouling are: Continuous treatment of one ppm prevent­ ed all fouling during a testing program 1. Protective Coatings. (Lovegrove &Robinson, 1966) along the 2. Clorination coast of Miami, Florida with down to 0.25 3. Increased Temperature ppm residual chlorine preventing fouling. 4. High Water Velocity Environment The dosage need not be toxic to the or­ 5. High Frequency Sound ganisms to prevent attachment. Just creating an unsatisfactory environment The last three are used in special (called exomotive dosage) is sufficient. cases (such as piping, small mechanical For example, in a free chlorine concen­ devices, etc.). The first two methods tration of 0.02 to 0.05 ppm, after sever­ will be considered here in more detail. al hours, mussels detach and leave, but are not killed by that dosage. The pur­ Coating Systems: Coating systems of pose however is to prevent initial toxic paints, coal tars, epoxy are in attachment. For example, barnacles once common usage for protection of ships and attached do not leave, and if killed other marine structures. Some of the still leave an attached shell. more common naval coatings are listed in Table 2. The electric current can be applied in an intermittent or continuous manner. Much of the antifouling paints (80% It has been found (Lovegrove &Robinson, in 1972) are copper based. As copper is 1966) that twice the current for 1/2 the leeched out of the paint, it prevents time length can be more effective. One bacterial and algal growth. Table 3 problem with intermittent treatment shows the minimum concentration in sea­ (even up to eight hours on), is that water for various compounds to inhibit some organisms (mussels and anemones) the growth of algae. may just close up and wait. Using A.C. current seems to be at least 40% more Coating systems are available to ef­ effective, besides preventing major de­ fectively prevent biofouling, and of posits on the cathode. Tables 4 and 5 course are dependent on the structural give some indication of dosage and design and metals chosen. effectiveness of this method.

Clarine Generation: Another techni­ Free chlorine would be produced at que used to prevent biofouling is the the anode and hydrogen at the cathode. electrolytic generation of chlorine. Other possible secondary reactions near This method is normally used in local­ the anode are: ized, sensitive areas where any growth

199 TABLE 2. SHIP COATING SYSTEMS

Coating Effective Life Recoating Procedure Against Biofouling

Coal Tar 1 year Dry Environment Vinyls 2 to 3 years " Epoxy 2 to 3 " " Chlorinated Rubber 2 to 3 " " Fiberglass 2 to 3 " " Bitumous Metal Pigmented 1 year " Zinc Silicates several years* "

*Corrosion resistant application only.

TABLE 3. MINIMUM CONCENTRATIONS OF COMPOUNDS TO INHIBIT ALGAL GROWTH

Compound Concentration (ppm)

Arsenic 15 to 17 Phenarsazine Cloride 0.8 Copper Chloride 7 to 10 Cuprous Thiocyanate 7 Mercury 4 to 5 Phenyl Mercury 1 Dibutyl Lead Diacetate 2 Tributyl Tin Oxide < 1 Tributyl Tin Fluoride < 1

200 1. Hypochlorite Ions ranged from about six to twelve volts, 2. Chloramine or an energy requirement in the order 3. Chlorate Ions of 0.1 to 0.4 watts per square foot. 4. Iodide, Bromide, etc. Even though protection seems to be good, energy requirements could get Other possible reactions at the cathode quite high if a large structure was to include: be entirely protected in such a manner. If the entire Sea Solar Power Plant 1. Magnesium Precipitation structure was to be protected in such 2. Production of Calcium Hydroxides a manner, using some approximate sizing, the energy requirements for continuous protection would be approximately 500 TABLE 4. LENGTH OF TIME TO KILL ALL kilowatts. Additional cost considera­ ORGANISMS, CONTINUOUS DOSAGE tions would include installation and maintenance of the cathodes and anodes. (This cost may be partially offset by Organism Dosage (ppm) cathodic protection provided for the 10 2.5 1 structure against corrosion.)

Anemones 4 days 6-8 days 15+ days Mussels EXPECTED PROBLEMS FOR THE PROPOSED 5 5 12-15 POWER PLANT Barnacles 3 4 5-7 As stated before, the nearshore shallow-water environment is the envi­ ronment most likely to cause biofouling. TABLE 5. LENGTH OF TIME (DAYS) TO KILL Our structure will probably be fabrica­ ted in a nearshore environment, and ALL ORGANISMS, INTERMITTENT DOSAGE during that period (approximately 1 year), would be exposed to all forms of biofouling. (This could be significant­ Organism Period of Treatment (hrs/day) ly reduced by using a fresh water con­ 1 2 4 8 24 struction site.) Either each wetted portion of the structure would have to be individually protected as it was Anemones 10+ 10+ 10+ 10+ 4 built, or a rather large maintenance Mussels 10+ 10+ 10+ 10+ 5 project would result before plant move­ ment to its final site. Barnacles 10+ 10+ 10+ 5 3 The most likely method of short term protection for this construction phase would be use of some coating system. To produce the concentration of chlo­ Any parts to be protected by electroly­ rine required, currents on the order of sis would have to use an external source 200 milliamps down to 50 milliamps are of power, or not be installed until the required, depending upon the size and final operational site. Again, if the shape of the area to be protected, cur­ construction stage spends at least a few rents, etc. From the testing program weeks in salt water before towing to sea, previously mentioned, 200 milliamps pro­ biofouling could be a problem. tected an area of about five square feet and 50 milliamps, an area of about three When the plant is at its final site, square feet, for about 1/2 year (approxi­ it will be located at a depth of 200 to mate length of the test). The voltages 270 feet. This is just at the depth

201 where biofouling becomes less of a pro­ CONCLUSIONS blem (bottom edge of the euphotic zone in many areas). At this depth rate of 1. Possible biofouling organisms attachment and growth would be slower. include algae, bacteria, hydroids, However, this is somewhat a function of barnacles, mussels, and tubeworms. how well the protection has prevented biofouling from occuring at the near­ 2. The biofouling organisms can shore construction site, as the struc­ increase drag coefficients by 40%. ture may bring its own community of or­ They can also create buoyancy problems ganisms with it. None of the studies from the added weight. encountered looked at such a possibility. Assuming no community and a good protec­ 3. Growth rates may range from tion system, new biofouling at that 100% barnacle coverage and up to a depth and location should be slight. centimeter high within a few months, to only algal and bacterial slime The structure will also be in a after a few years, depending upon the surfaced position approximately once environments. every 14 days for crew replacement and routine maintenance. Even though the 4. Protection against biofouling structure is at an offshore location, for the nearshore phase (the worst attachment of organisms, especially condition) and for the offshore site goose barnacles, could occur during will be necessary. It will probably these surfaced periods. consist of a coating system with some production of chlorine. The most likely organisms to attach and grow at the offshore (submerged) site would be algae, bacteria, and hydroids, unless other organisms were brought to the site.

202 REFERENCES

Dolgo Dolskava, M.A. "Biological and Physico-chemical Factors Influencing Effectiveness of Antifouling Paints", Corrosion Engineering, 1969.

Haderlie, E.C. "Marine Boring and Fouling Organisms in Open Water of Monterey Bay, California", A Thesis, U.S. Navy Post Graduate School, Monterey, California, 1968.

Lovegrove, T. and T. Robinson. "Prevention of Fouling by Localized Chlorine Generation", University of Miami, 1966.

Muraoka, T.J. "Relation Between Marine Fouling and Corrosion Rate of Carbon Steel and Aluminum Alloy at Surface and at 6, 000 Ft." Naval Civil Engineering Lab Technical Report No. 681. NCEL, May, 1970.

Naval Ships System Command. Preservation of Ships in Service. Technical Manual Chapter 9190. U.S. Government Printing Office, 1970.

Ray, D.L., ed. Marine Boring and Fouling Organisms. Seattle: University of Washington Press, 1959.

Coating Systems Guide__ for Hul.L_Deck and Superstructure. T & R Bulletin 4-10. The Society of Naval Architect and Marine Engineers, 1967.

Starbird, E. "Friendless Squatters of the Sea", National Ge.Qgraphic. 144(S): 622-633, November, 1973.

Thompson, J.C. "Effects of Deep and Shallow Ocean Environments on Construction Materials", Naval Civil Engineering Lab Technical Report, 1593. NCEL, 1967.

Walters, A.H. Biodeteriorization of Mate~ials. London: Elsevier Publishing Co., 1966.

203 j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j SOLAR SEA POWER PLANT

ENVIRONMENTAL IMPACT - AQUACULTURE POTENTIAL

by

William G. Mercer

ABSTRACT

The regions of natural upwelling, It is the utilization of this area of representing about one tenth of one upwelling, and the resulting increase of percent of thetotal ocean surface, are biological productivity associated with it, producing approximately one half of the to provide a substantial source of fish world's fish supply. By bringing deep protein with the minimal amount of cost in­ nutrient laden water, containing nitro­ curred, which this study investigates. gen and phosphorus, from approximately 1000 feet depth, up to the solar sea By providing an area of protein available power plant to be utilized in the con­ for human consumption, as well as a source densers and then released, an artificial of energy; such a plant concept could pro­ upwelling is caused in the surrounding vide a step toward solutions of the global area. shortages of food as well as energy.

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1 SOLAR SEA POWER PLANT

ENVIRONMENTAL IMPACT - AQUACULTURE POTENTIAL

by

William G. Mercer

INTRODUCTION PRESENT FORMS OF AQUACULTURE

The economic feasibility of a solar Aquaculture has been practiced at a very sea power plant, such as the one under low level throughout most of the world, es­ study depends upon the utilization of pecially in the United States and Europe. all aspects related to its operation. One of the major reasons for this is that Because of the artificial upwelling cre­ these countries have traditionally been ated by bringing nutrient laden water up what could be considered agricultural coun­ from a depth of approximately 1000 feet, tries, with relatively little interest in the possibility of aquaculture as a re­ fish consumption, and therefore, fish farm­ sulting by-product of the basic opera­ ing or aquaculture. Another reason for the tion has great potential. low level of aquaculture to date in the western nations is that the people have had While the present population of the fastidious tastes and therefore, rarely eat world is increasing at a rate of three other than a very small portion of the num­ percent per year, food production is on­ erous edible seafood types available. ly increasing at a rate of 2.7 percent; with food shortages presently being rea­ In contrast to this, the people of Japan lized throughout the world. What is consume a greater variety of seafood than needed is a low cost food supplement any other country in the world. Accordingly, rich in high quality protein. At the they also have the highest degree of aqua­ present time biological life in the culture developed to date. oceans is the least tapped protein source of unknown abundance. Closed Water Aquaculture: Aquaculture in closed waters is a costly The major objective of this report is business resulting in a costly product. In to investigate the possibility of utili­ order to be advantageous it must usually be zing the artificial upwelling as a means conducted by producing food to be bought of a protein base in the form of aqua­ with a minimum amount of processing and culture. transportation, or to produce such high

207 demand products as oysters, mussels, by the sunlight, where the artificially clams or shrimp, which the customer is upwelled nutrients may be utilized in an willing to pay for the expenses incurred. area of high photosynthesis. In these cases large-scale controlled aquaculture can be achieved in restrict­ Due to technological advances this form ed lagoons and estuaries, where the mi­ of aquaculture is the most recent to be gratory fish, as well as the fertiliza­ experimented with and therefore, the least tion of the water with essential nutri­ amount of reference exists for this as ents, can be retained. compared to the other types of aquaculture.

Offshore Pumping to Onshore Ponds: In this method of aquaculture, cold UTILIZATION OF AQUACULTURE WITH THE SOLAR deep offshore water is pumped up through SEA POWER PLANT large diameter pipes, and then run into lagoons, tanks or ponds where it will Applicable Forms of Aquaculture: stimulate the photosynthetic process by As can be seen in prior sections of providing the necessary nutrients. The this report, the general nature of the resulting phytoplankton can then be uti­ Solar Sea Power Plant would be an artifi­ lized by organisms higher up the trophic cial upwelling of deep nutrient laden chain. Such a study was conducted in water, and therefore, either offshore 1969 by O.A. Roels, R.D. Gerard, and pumping to onshore ponds or to open sea A.W.H. Be, of the Lamont-Doherty Geolog­ could be utilized. However, in this case, ical Observatory of Columbia University where the prototype plant would be located (Costlow, 1971). This study was con­ approximately sixteen (16) miles off of ducted at an experimental station at St. the coast of Miami, Florida, offshore Croix, where water was pumped to shore pumping and open sea·aquaculture is the from a mile offshore where the water type chosen as the most beneficial to depth was approximately 1000 meters. study.

The results of this study showed that The rate of primary production is known at least 35 microgram-atoms nitrate ni­ to be highly variable. John H. Ryther trogen per liter seawater were present (1969) states that nearly 90% of the ocean at the nutrient maximum at the St. Croix is essentially a biological desert. The station. They assumed approximately 65% open oceans produce a negligible fraction of the nitrogen content in the water was of the world's fish catch at present, and in the form of nitrate nitrogen and have little or no potential for yielding therefore, assuming a 10% efficiency of more in the future. Upwelling regions, on conversion of phytoplankton to a high the other hand, which total no more than priced secondary consumer, they could approximately one-tenth of one percent produce 3.3 tons of secondary producer (0.001) of the ocean surface produce about per year in 5,000 sq.ft. half of the world's fish supply. The other half is produced primarily in coastal Offshore Pumping and Open Sea waters and the few offshore regions of Aquaculture: comparably high fertility. This is the type of aquaculture which is basically under study in this project. Photosynthesis is carried on mainly in By this method water is pumped up from the upper layer of solar light penetration well below the surface (approximately where single cell organisms are produced, 1000 ft. in our study) and. then dispers­ whereby larger marine growths are produced, ed in the upper layer of water penetrated step by step according to different trophic

208 levels. The larger the plant cells at solar sea power plant under study. With the beginning of the food chain, the the shortages of food, as well as energy, fewer the trophic levels that are re­ which are seen today, such a system may quired to convert the organic matter in­ not provide the final answers, but would to useful form. When this life dies the definately be concentrating efforts in remains settle slowly to the ocean the right direction. depths where they break down and disin­ tegrate. The residues of these remains Major Factors of Open Sea Aquaculture: then are carried, both in solution and One of the major considerations for the as particles back to various areas of utilization of an optimal aquaculture ven­ upwelling. In these upwelling areas the ture as a by-product of the solar sea food chains are potentially shorter than power plant is the level at which the nu­ in non-upwelling areas as the organisms trient laden water brought up from approx­ produced are large enough to be directly imately 1000 ft. is discharged. The max­ utilized by man from trophic levels very imum depth in most areas to which sunlight near the primary producers. This is due penetrates for the production of phyto­ to the fact that the phytoplankton in plankton and zooplankton is roughly 300­ these upwelling regions are of large 350 feet. In our prototype, the discharge size and that many of these species are level has been established at approximately colonial in habit. 270 feet below the surface. Therefore, the utilization of the artificially upwelled For example, the eight most abundant waters will be less than optimal. species of phytoplankton in the upwell­ ing region off Peru (one of the most Another major consideration would be fertile upwelling regions of the world) the economic feasibility of conducting an are: Chaetoceros socialis~ C. debilis~ aquaculture project at an offshore power C. lorenzianus~ Skeletonema costatum~ plant. Due to the extremely high costs Nitzshia seriata~ N. delicatissima~ of both installation and maintenance it Schroederella delicatula~ and Asteria­ would be impractical to have containments nella japonica (Reeve, 1968). which are customary to normal methods of aquaculture. These containments, such as Much of these phytoplankton can be pens, nets, or rafts, would require too readily eaten by large fishes without much capital expenditure to be considered special feeding adaptation. Also many for use in this side by-product of the of the clupeoid fishes (sardines, ancho­ actual solar sea power plant. vies, etc.) have specially modified gill rakers for removing the larger species Rather than having a confined area of of phytoplankton from the water. There­ certain forms of aquaculture, the power fore, there exists a one or two step plant could provide areas of approximately food chain between phytoplankton and concentric shape whereby an optimal zone man in most areas of upwelling, as com­ would be established at which biological pared with at least a three step food life could prosper in proper conditions chain between phytoplankton and man in (i.e. temperature, salinity, dissolved typical coastal waters. oxygen, effects of biofouling, predators, and areas have the highest amounts of us­ The already observed advantages in able nutrients). The exact levels of areas of natural upwelling seem to point these various parameters would be dependent out the great potential in the study of upon the specific combinations produced on artificial upwelling as would be seen in the existing ambient conditions with the the utilization of aquaculture with the addition of the discharged deep water.

209 The types of products which could ex­ there would be increased biological pro­ ist and be utilized by the artificial ductivity with a minimum amount of con­ upwelling of the solar sea power plant tamination, it is pos?ible that the sys­ under study would be those which best u­ tem, acting as an attractant to fishes tilize the diatoms present around such a and other animals, could present other system and then in turn be beneficial to problems. If impingement at the intake man with the least amount of trophic and entrainment of small organisms into chain manipulations. Such creatures the cooling system is density-dependent, would be shrimp, sardines, and possibly the effect of attraction of biological anchovies. The possibility of oysters activity could prove to be detrimental. was studied, but rejected as they would However, since the nutrients, which will require physical equipment such as rafts, be brought up from the deep water by ar­ and could be produced more efficiently tificial upwelling, must be in the upper closer to shore in warmer waters. layer of water for a period of time before being utilized by higher trophic chains, Since our system would not have any and because the power plant is located in confinements for those products being a relatively strong current; it is felt raised, the problem of disease control that the zone of highest productivity and would be minimized. Those animals not increased biological activity, and thus strong enough to fight the current could the highest concentration of fish, will not remain in the high productivity zone be in an area away from the plant itself. surrounding the solar sea power plant. The larvae and other very small creatures Other factors must also be considered produced by the adult size organisms in the system under study. Although the would also be carried out of our system, artificial upwelling will cause a substan­ but other adult size organisms would be tial increase in the amount of the princi­ attracted and therefore, a fairly stable pal nutrients nitrogen, phosphorus, and ecosystem could be established. carbon, and thus, provide a richer habitat for diatoms, the changed water temperature The problem presented by periodic may cause a shift in species composition plant shut down for crew charge and favoring less desirable green and blue­ maintenance should not present any seri­ green algae. The actual degree to which ous detrimental effects to the proposed this type of algae would flourish would aquaculture system because the amount of again depend upon the actual location down time is not sufficiently long to sight of the solar sea power plant. In cause break up of the ecosystem. The the case of our model, being located ap­ system would have to be down for a per­ proximately sixteen miles off of the coast iod of time closer to a week in order to of Miami, Florida, with the deep cold water do substantial damage to the dependent brought up from upwelling being discharged ecosystem. If such a long shutdown per­ at a temperature of approximately 50°F, iod was to occur, it is very possible this should not present any significant that fish would be effected by cold problem. shock which in turn could inhibit feed­ ing and predator avoidance or even cause death directly. CONCLUSIONS

Although it is felt that the solar The presence of the solar sea power sea power plant under study would pro­ plant, located off of the coast of Miami, vide a system which would induce an ar­ Florida, should provide a beneficial envi­ tificial form of upwelling in which ronment for increased biological activity

210 for the trophic chains discussed. Since, Since no confining equipment, such as in our case, the current velocities are nets and pens, would be used, there would significant, and the direction is rela­ be no cost of maintenance, and not only tively stable, an area will be created would such a system provide a source of which will attract fish and other forage fish protein fo.r. human"'~pnsumption, but it animals. The plume will provide a more would provide a good indicator to .....b,e uti­ constant and suitable area for growth, lized to insure the level., at which the especially during the colder months of solar sea power plant e~fects the imme­ the Fall and Winter. diate environment.

It is noted that production is not e­ This type of noncontained aquaculture quivalent to potential harvest since it should provide an area of substantially in­ will also be eaten by other top-level creased biological production at a minimal carnivores, besides man, such as birds, cost, and therefore, be considered advanta­ squid, tuna, and other natural predators. geous to the installation and design of a solar sea power plant, such as the one under study.

REFERENCES

Behrman, Daniel. The New World of the Oceans. Boston: Little, Brown and Company. 1970.

Chapman, W.M. Potential Resources of the Ocean. Serial Publication 89-21, 89th Congress, Government Printing Office, Washington, D.C. 1965.

Costlow, John D., Jr. Fertility of the Sea. Vol. 2. New York: Gordon and Breach Science Publishers. 1971.

Duxbury, Aly C. The Earth and its Oceans. Reading Massachusetts: Addison­ Wesley Publishing Company. 1971.

Eppley, Richard, et al. Biological Asp~cts o~~ffshore Nuclear Power Plants. Power Siting Workshop, Rockville, Maryland. 1973.

Firth, Frank E. The En~£~edia of Marine Resources. New York: Van Nostrand Reinhold Company. 1972.

Hull, Seabrook. The Bountiful Sea. Englewood Cliffs, New Jersey: Prentice Hall, Inc. 1969.

Othmer, Donald F., and Roels, Oswald A. Power, Fresh Watera.~nd Food from Cold, ~Sea W_?.ter. Science 182: 121-125. . • ..... Ryther, John H. photosynthesis and Fish Production in the Sea. Science 166: 72-76, October, 1969.

Reeve, M.R. ~mposium Marine Food Chains. Aarhul, 1968.

211