WAVE ENERGY: TECHNOLOGY TRANSFER & GENERIC R & D RECOMMENDATIONS
ETSU V/06/00187//REP
DTI Pub/URN 01/799
Contractor: Arup Energy Ove Arup & Partners International
Prepared by: D Scarr R Kollek D Collier
The work described in this report was carried out under contract as part of the Sustainable Energy Programmes, managed by ETSU on behalf of the Department of Trade and Industry. The views and judgements expressed in this report are those of the contractor and do not necessarily reflect those of ETSU or the Department of Trade and Industry.
First published 2001 © Crown Copyright 2001 EXECUTIVE SUMMARY
The Wave Energy Industry has developed successful prototypes for devices on the coastline and is currently in the process of developing prototypes for proving in near and offshore areas. As the industry moves offshore, the opportunity exists for transfer of technology from other industries, notably from the offshore oil and gas industry. Ove Arup & Partners (Arup) were invited by the UK Department of Trade and Industry (DTI) Wave Energy Programme to carry out a study to review the current status of the technologies in the emerging Wave Energy Industry, to identify the potential for transfer of technology from other industries and to make recommendations for priorities in future research and development. It should be noted that identifying device costs was not part of the study scope. Arup have reviewed the status of the industry by way of individual interviews with all teams currently active in the UK as well as by research of international activities in the area. A preliminary technology workshop was organised to identify and discuss key issues with the teams and other industries. The following technology areas were discussed: 1. Regulatory Environment, HSE, Design Codes and Verification 2. Construction Methods and Project Cost Estimation 3. Marine Operations 4. Mooring Systems 5. Operations and Maintenance 6. Materials 7. Hydraulic Systems 8. Pneumatic Systems 9. Subsea Cables and Connectors 10. Control Systems 11. Power Quality and Grid Connection The recommendations were made bearing in mind the proposed programme of Wave Energy Converter (WEC) prototype and power station development and the perceived need for further cost reductions. The major conclusions of the study were: • The Wave Energy Industry is poorly co-ordinated. At present, all teams are working independently and commercial considerations force them to keep their ideas secret. • There remains a lack of investor confidence and hence industrial support for the industry. Teams tend to be relatively small working out of University Departments or SMEs with some industrial backing. • No major technological barriers to the development of Wave Energy Prototypes have been identified. All the issues raised under design, construction, deployment and operation can be addressed by transfer of technology from other industries, especially the offshore industry. However, costs, risks and approvals will need to be addressed. • However, some technology gaps have been identified, notably in the areas of mooring and cable connections detailing, hydraulic machines and grid connection and energy storage. The major recommendations of the study were:
i • Set up a supported co-ordinating body to encourage technology transfer to the industry. • Government support should be directed at the proving of prototypes, thereby improving confidence and encouraging industrial support. High initial project costs, especially for offshore devices, will otherwise be a significant barrier to the development of prototypes. • Several generic R & D activities have been identified to address the technology gaps. The results of this study were presented in a Workshop organised by the DTI in East Kilbride, Scotland on 24 October 2000. The report has addressed issues raised by participants at this event.
ii CONTENTS
Page
1. INTRODUCTION 1 1.1 Objectives 1 1.2 Main Contributors 2 1.3 Additional Contributors 2
2. METHODOLOGY 4 2.1 Literature Review 4 2.2 Wave Energy Team Input 4 2.3 Issue Identification 4 2.4 Technology Workshop 5 2.5 Issue Clarification and Study Recommendations 5
3. WAVE ENERGY DEVICES 6 3.1 Wave Energy Collector Database 6 3.2 Classification 6 3.3 Wave Energy Collector Type 6 3.4 Location 6 3.5 UK Wave Energy Collector Schemes 7 3.6 LIMPET 500 8 3.7 Pelamis 9 3.8 Edinburgh Duck 10 3.9 PS FROG 11 3.10 Sperbuoy 12
4. KEY TECHNOLOGY ISSUES 13 4.1 Regulatory Environment, HSE, Design Codes and Verification 14 4.2 Construction Methods and Project Cost Estimation 18 4.3 Marine Operations 21 4.4 Mooring Systems 24 4.5 Operations and Maintenance 27 4.6 Materials 29 4.7 Hydraulic Systems 32 4.8 Pneumatic Systems 35 4.9 Subsea Cables and Connectors 37 4.10 Control Systems 40 4.11 Power Quality and Grid Connection 42
5. CONCLUSIONS AND RECOMMENDATIONS 45 5.1 Conclusions 45 5.2 Recommendations 46
6. FIGURES 50
7. ACKNOWLEDGEMENTS 63 APPENDICES
A. WEC CONTACTS DATABASE A1-6 A1. WEC Teams A2. Industry contacts
B. TECHNOLOGY WORKSHOP KEY ISSUES SLIDES B1-24
C. WEC TEAM QUESTIONNAIRE RESPONSES C1-32
D. TECHNOLOGY WORKSHOP MINUTES D1-9
E. TECHNOLOGY WORKSHOP QUESTIONNAIRE RESULTS E1-12
F. BIBLIOGRAPHY F1-3 F1. Literature Bibliography F2. Internet Bibliography F2.1 At Shore F2.2 Near Shore F2.3 Offshore F2.4 Academic F2.5 General 1. INTRODUCTION One of the largest potential areas for Renewables Energy Development is in the exploitation of Energy from the Waves. The Wave Energy Industry has developed successful prototypes for devices on the coastline and is currently in the process of developing prototypes for proving in near shore areas. As the industry moves offshore, the opportunity exists for transfer of technology from other industries, notably from the offshore oil and gas industry. The offshore oil and gas industry has itself undergone considerable development in the last ten to twenty years, with notable key developments in subsea, floating and unmanned facilities and technologies. Great efforts have also been made to reduce costs, notably the Cost Reduction in the New Era (CRINE) Initiative of the mid 1990s. The UK Department of Trade and Industry (DTI) Wave Energy Programme has recognised that this potential exists and has asked Ove Arup & Partners (Arup) to undertake a review of the current Wave Energy technologies and to identify areas where the potential for transfer of technology exists from other industries, notably the offshore oil and gas industry to the emerging wave energy industry. In addition, Arup were asked to identify where generic research and development might improve or adapt existing technology to enable the development of Wave Energy Converter (WEC) schemes. The Wave Energy Programme is currently being managed by the Energy Technology Support Unit (ETSU). Arup Energy, part of the Industrial Engineering Sector of Ove Arup, have carried out the study work. This report summarises the work carried out and in its draft version was used as preparatory material for a Technology Workshop organised by ETSU in East Kilbride, Scotland on 24 October 2000. Feedback from this workshop is included in this report. The study was carried out between August and December 2000.
1.1 Objectives The study had the following objectives: • Review existing wave energy technologies by consultation with current WEC developers and technologists. Identify the key technology issues facing the development of WECs. • Propose transfer of technology from other industries, notably the offshore oil and gas industries to the emerging Wave Energy Industry. • Make recommendations for generic research and development which would promote the development of WEC schemes. • Make recommendations for future priorities and research and development funding strategy to support the industry. This report does not attempt to provide solutions to technical problems of the Wave Energy Industry or to evaluate the performance of any of the devices. Rather, it aims to identify common issues faced by developers of Wave Energy Technology and suggest the methods by which the issues should be resolved.
Page 1 1.2 Main Contributors Arup Energy, part of Ove Arup & Partners, based in London, Aberdeen, Perth, Houston and Singapore provides multidisciplinary services focused on energy sector companies engaged in upstream activities from exploration and extraction to transmission and distribution. Projects include Steel and Concrete Offshore Platforms, Pipelines, Power Stations and Coastal Engineering. Arup Energy is a multidisciplinary organisation focusing on structural and civil engineering project design and management supported by core experience in naval architecture, hydraulics and mechanics, controls and instrumentation, risk and safety. Dr Tony Lewis from University College Cork assisted in the Arup study as a consultant for Wave Energy technologies. Dr. Lewis has monitored or been directly involved in the development of most of the Wave Energy schemes developed over the last twenty five years around the world. He has considerable experience in key wave energy technologies and has been previously involved in the European, UK and Irish Wave Energy Programmes. Dr Lewis is Director of University College Cork ’s Hydraulics and Maritime Research Centre.
1.3 Additional Contributors Arup Energy invited a number of WEC teams to contribute to the study. The following teams were interviewed: • Wavegen • Queens University Belfast • Ocean Power Delivery • Edinburgh University • Professor Michael French • Plymouth University The following WEC teams submitted a completed questionnaire: • Energetech, Australia • Hosepump, Sweden • OMI, USA • OWEC, USA • Professor Johannes Falnes, Sweden • Wavebob, Ireland Several companies provided input: • ETSU • Ramboll • Lloyds Register • HSE • Offshore Contractors Association • Noble Denton • Conoco • Rexroth • BHR Group • Alcatel Kabel • ABB
Page 2 • Econnect • Scottish and Southern Electricity • WS Atkins • Garrad Hassan • Tronic
Contact details are provided in Appendix A.
Page 3 2. METHODOLOGY The overall project process adopted was as follows: • Information was gathered through a review of published and internet based data • Active WEC teams were interviewed by Arup personnel • Key technology issues were identified in consultation with WEC teams • A Technology Workshop was organised in London to facilitate discussions and continue transfer of technology between offshore industry personnel and WEC teams and to refine the understanding of Key Technology needs • In each technology area, the potential for technology transfer was identified and recommendations for research and development made.
2.1 Literature Review The objectives of the early stages of the study were twofold: • To identify and contact teams developing WECs or involved with Wave Energy Technology. • Identify key issues for the development of WECs already publicised. Recent published information was reviewed. See Appendix F for a bibliography. A search of available internet sites was carried out. See Appendix F for a list of addresses.
2.2 Wave Energy Team Input There are only 6 WEC teams currently active in the UK. It was decided to meet with all of these teams. Teams outside the UK were also given the opportunity to participate in the study by email, fax and telephone. The teams were asked to identify key technology issues perceived by them as technically unproven, incurring significant cost or areas outside their immediate control. Discussions covered all stages in the development of their scheme; design (structural, mechanical, hydraulics, electrical, control, etc), construction, transportation and installation, inspection, maintenance, repair and removal. Responses were recorded on a pro-forma questionnaire. Responses are included in Appendix C. Wave Energy Teams outside of the UK were contacted by email. They were also requested to complete the questionnaire. Their responses are also included in Appendix C.
2.3 Issue Identification Responses to the questionnaires, minutes of meetings with WEC teams and all of the data collected to date were critically assessed by in-house specialists in each technology area. Consultation was sought with experienced parties in the offshore and other industries. Key technology issues requiring technology transfer and/ or research and development were identified in each technology area.
Page 4 2.4 Technology Workshop A Technology Workshop was organised to discuss and verify the Key Technology Issues identified. These were summarised in presentation slides used at the workshop (see Appendix B). The event provided an open forum to discuss problems faced by the Wave Energy Industry and current experience from the offshore and other industries. Participants were drawn from three fields: • WEC Teams • Offshore Oil and Gas Industries • Other Industries In addition, it provided an opportunity for Wave Energy Teams to meet and develop contacts with representatives from the other industries. The technology workshop was held on September 15 th at the Arup offices in London. Over 40 attendees attended from a wide range of sectors. The agenda was structured by Arup around the key technology areas identified from the interviews and earlier consultation. Each topic was introduced by an Arup Facilitator, the key technology issues raised and a relevant presentation was made by a representative from the offshore industry. The open discussion which followed was minuted (see Appendix D). A second questionnaire was introduced at the workshop to help gauge support for key technology issues in each area.
2.5 Issue Clarification and Study Recommendations Following the workshop, the key technology issues identified earlier were reviewed in the light of the workshop findings. The workshop minutes were examined and the workshop questionnaire responses were collated and main messages identified (see Appendix E). Using this information, the most important key technology issues were refined. The in-house specialists considered each of the key technical issues and recommended a suitable course of action for their resolution.
Page 5 3. WAVE ENERGY DEVICES
3.1 Wave Energy Collector Database A database has been compiled which lists all WECs under development worldwide. See Appendix A. The database contains the name, status, description and contact details for each device.
3.2 Classification Many different types of device are under development in the UK and worldwide. The approach of this study is to consider wave industry technology needs, without reference to specific devices. It was therefore decided to introduce a classification for families of devices that share similar features. There are many ways to classify devices. The system chosen for this study uses two methods; WEC type and location.
3.3 Wave Energy Collector Type
3.3.1 Buoyant Moored Device A device of this type floats on or below the water surface. It is moored to the seabed either with a taut or slack mooring system (Figure 3.1).
3.3.2 Hinged Contour Device A hinged structure follows the contours of the waves and takes power from the motion at the joints. It is slack moored to hold it on station (Figure 3.2).
3.3.3 Oscillating Water Column (OWC) An OWC uses an enclosed column of water as a piston to pump air. These structures can float, be fixed to the seabed or mounted on the shoreline (Figure 3.3).
3.4 Location
3.4.1 At Shore A device of this type is sited at a shoreline location on land.
3.4.2 Near Shore A near shore device will be sited in open water, within 12 miles of the shoreline. This distance has been arbitrarily chosen as the approximate average limit of visibility from the shore. Near shore should also be understood to refer to shallower water depths than offshore. Approximately 50m water depth has been arbitrarily chosen as the near shore water depth.
3.4.3 Offshore An offshore device will be sited further than 12 miles from the shoreline. Water depths of greater than 50m constitute offshore devices.
Page 6 3.5 UK Wave Energy Collector Schemes The following sections introduce (in no particular order) the current range of WEC schemes under development in the UK. A brief description of the devices and the current status of the project is described. Key technology issues identified by the teams themselves in interviews with Arup are listed. The devices selected are not an exhaustive list of the schemes or teams under development in the UK. Rather, they were selected, in discussion with the UK based teams, to represent the range of devices currently under consideration. A more complete list appears in Appendix A1. Table 4.1 illustrates the diversity of types of WEC under development in the UK. Table 4.1 Classification of UK WECs WEC Type Suitable for Location Scheme Buoyant Hinged OWC At Near Off Moored Contour Shore Shore Shore Limpet Z Z Pelamis Z Z Edinburgh Duck Z Z PS Frog Z Z Z Sperbuoy Z Z
Page 7 3.6 LIMPET 500
3.6.1 Device Description Limpet 500 is a shoreline, Oscillating Water Column (OWC) type WEC (Figure 3.4). It is currently supplying 0.5MW of power to the grid on the Scottish island of Islay. The wave energy collector is in the form of a partially submerged shell into which seawater is free to enter and leave. As the water enters or leaves, the level of water in the plenum chamber rises or falls in sympathy. A column of air, contained above the water level, is alternately compressed and expanded by this movement to generate an alternating stream of high velocity air in an exit blowhole. If this air stream is allowed to flow to and from the atmosphere via a pneumatic turbine, energy can be extracted from the system and used to generate electricity. 3.6.2 Current Status The LIMPET 500 was scheduled for commissioning in October 2000. Further modules are planned in a second stage of development in the future. Limpet has been developed to its current commercial stage as a collaborative project between Wavegen (a private company) and Queens University, Belfast who have been involved in the research and development of wave power generation for over 20 years. Wavegen are developing a new offshore WEC, details of which have yet to be released.
3.6.3 Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. • Clarification of HSE regulations and underwriter requirements. • Guidelines for OWC construction. • Wave data for WEC locations. • Data for structural slam loads from waves. • Estimating construction costs. • Construction contracts. • Rapid attach/detach moorings. • Site investigation data for prototype anchorage. • Design lifetime of components and materials. • Erosion of rust. • Power transmission by fluid to shore. • Difficulties with the use of pneumatic systems offshore. • Comparison between the different types of pneumatic turbines • Subsea connector and cabling costs. • Control algorithm optimisation • Grid information; demand and supply locations, available capacity from nuclear power plant decommissioning, unrealistic specification of grid, comparisons with grids outside the UK.
Page 8 3.7 Pelamis
3.7.1 Device Description The Pelamis WEC is a hinged contour device for deployment offshore (Figure 3.5). The wave induced motion of the joints is resisted by hydraulic rams which pump high pressure oil through hydraulic motors via smoothing accumulators. The hydraulic motors drive electrical generators to produce electricity. A 750kW device will be 150m long and 3.5m in diameter and composed of 5 modular sections. Power will be linked to the grid via subsea power cables. Key features incorporated into the concept include: • Survivability • Power capture efficiency • Non site specific • Minimum on-site work • 100% ‘available ’ technology • Modular construction and systems 3.7.2 Current Status Pelamis is being developed by Ocean Power Delivery (a private company). They have a development programme which aims to demonstrate the concept through a staged test programme. Model testing (both in the frequency and time domain) at 80th(survivability), 35 th(numerical code validation) and 20th(survivability and numerical model validation) scale have been successfully completed. The next immediate target is a 7th scale prototype for systems development to be deployed in early 2001.
3.7.3 Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. • Standard test site to assist in prototype deployment and device comparison. • Patent applications. • Power absorption in structural design calculations. • Estimating construction costs. • Approval permits required and timetable. • Fretting resistant design detail of mooring connection. • Rapid attachment/detachment moorings. • Mooring line material life. • Hydraulic seals. • Subsea cables and connectors. • Time domain modelling. • Short term smoothing of power. • Feasibility of isolating the device from grid fault conditions.
Page 9 3.8 Edinburgh Duck
3.8.1 Device Description Ducks (Figure 3.6) have a stubby aerofoil cross section. A number of them rotate independently about a long articulated spine which obtains stability by spanning wave crests. The angular variation of displacement of the front surface is designed to match wave particle motion. In moderate sea states the mostly cylindrical back section of the duck creates no stern waves but the larger movements induced by rough weather shed energy through wave making to the rear. Spine joint movements and moments are controlled by rams which contribute to overall power capture and which ‘give ’ to shed energy in large waves. This puts a defined upper value on the stresses and reduces the mooring forces. The mooring needs at least 80 metres of water and uses a system of submerged weights and buoys to give an almost constant tension.
3.8.2 Current Status The Duck team is led by Professor Salter at Edinburgh University. This concept requires the development of new technologies. The team is working on component parts of a high torque hydraulic system. These include ring cam pumps and fast hydraulic motors with low part-load losses. The displacement of these machines is varied by digitally controlled poppet valves. The team have also developed a Wells Turbine with variable pitch for use at the Pico, Azores Oscillating Water Column project and are researching the Sloped IPS Buoy wave energy device.
3.8.3 Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. • Estimating costs. • Constant tension loading on mooring lines. • Light, quite strong and cheap building material. (e.g. ultra light concrete). • High performance hydraulics, inc. high torque ring cam pumps. • Large, high velocity seals. • Squeeze film bearings.
Page 10 3.9 PS FROG
3.9.1 Device Description The P S Frog is a WEC of the buoyant moored, offshore type which aims to generate a mean output of 600kW per unit (Figure 3.7). It is entirely enclosed within a floating sealed hull, with no external working parts. The FROG behaves as a point absorber with large motions; this requires resonance to achieve a high dynamic magnifier. The whole hull works as a pendulum to supply the reaction. The motion can be analysed into forced pitching about P, which provides the reaction, combined with resonant pitching about G, which provides the motion of the working surface (the paddle). It is tuned to the prevailing wave frequency by moving water ballast (‘slow tuning’). A sliding mass restrained by hydraulic rams acts as the power take-off by providing an alternating gravitational torque about the pitch axis. There is a large hydraulic accumulator which provides both a store and smoothing, and a hydraulic motor driving the generator. Because real seas are irregular, the sliding mass must be controlled to achieve quasi-resonance, by switching the ram state between pumping, driving, idling and (judiciously) locked, (dynamic tuning).
3.9.2 Current Status The FROG has been developed at Lancaster University in a team led by Professor Michael French. Work thus far has been almost exclusively conceptual. Limited model testing was carried out to verify the theoretical performance. A lack of funding has restricted development beyond this stage. Since last year the team have modified the design to locate the sliding mass above the water and fill the bottom compartment with ballast. The team claim this should increase the output, reduce the mass required and simplify the engineering.
3.9.3 Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. • Wave data for use in design. • Estimating Costs (construction, marine operations, moorings). • Rubber joints used on moorings. • Reliability of compliant mooring systems. • Water based hydraulic systems. • Hydraulic seals and leakage. • Compatibility of cables with compliant moorings.
Page 11 3.10 Sperbuoy
3.10.1 Device Description The Sperbuoy is a floating oscillating water column device for deployment in the near shore environment (Figure 3.8). The device has four vertical capture chambers of different length. A floatation unit around the circumference provides buoyancy and the power take off sits on the top of the device. The unit is 12m long and 5m diameter. The aim of the multiple chambers is to extend the capture bandwidth of the device to improve efficiency. Power take off will be from an impulse turbine which drives a generator. The power generation target is 5kW although the prototype device will not supply the grid; it will be used to collect data. The device is transported to site on board a vessel. It is deployed by winching it overboard and attaching it to pre-laid moorings.
3.10.2 Current Status The project was initiated by Embley Energy and is being developed under the European Commission CRAFT scheme. The partners involved are a consortium of Small to Medium Enterprises (SME): Embley Energy Ltd CTP Limited IBK Bernard Bonnefond Hippo Marine Products There are also 3 Research to Development performers (RTD): PEP, University of Plymouth University of Cork Chalmers University of Technology The prototype Sperbuoy was scheduled for launch in the Plymouth Sound in November 2000. It will operate for a period of months during which time data will be collected on its behaviour.
3.10.3 Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. • An archive of previous work to assist in research. • Data on wave climate. • Flexible attachment to the mooring system. • Quick release mooring systems. • Installation guidelines. • Investigation of the relative efficiencies of a Wells Turbine and an Impulse Turbine. • CFD analysis of the pneumatic system. • A flexible power connection which floats.
Page 12 4. KEY TECHNOLOGY ISSUES The perceived Key Technology Issues affecting the Wave Energy Industry were identified and reviewed. The issues were discussed with the WEC teams active in the UK. Teams active outside of the UK were given the opportunity to contribute by way of questionnaires. The issues were verified at the Technology Workshop held in September. During this process, the following technology areas were identified for detailed consideration:
1. Regulatory Environment, HSE, Design Codes and Verification
2. Construction Methods and Project Cost Estimation
3. Marine Operations
4. Mooring Systems
5. Operations and Maintenance
6. Materials
7. Hydraulic Systems
8. Pneumatic Systems
9. Subsea Cables and Connectors
10. Control Systems
11. Power Quality and Grid Connection
In the following sections, the Key Technology Issues for each technology area are identified. For each issue, the current status and recent advances which affect this issue are discussed, potential for technology transfer is identified and any generic research and development needs are recommended.
Page 13 4.1 Regulatory Environment, HSE, Design Codes and Verification
4.1.1 Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: • What Regulations will apply? These questions were raised by the WEC teams because the Will Energy Making Devices be treated planning and approvals process the same as Offshore Oil and Gas for WEC prototypes is not well Installations? defined. They were aware that Will prototypes be treated differently to offshore wind schemes have full scale WEC Power Stations? experienced difficulties because of the many authorities What is the Planning Approvals and responsible for coastal and Licensing Route? offshore locations. • Are there parallels with other Industries; e.g. Parallels - in terms of lessons Offshore Wind? learned regarding design codes, approvals and technologies. • Which Design Codes apply? Are the codes developed for offshore oil and gas applications still applicable for the design of WEC schemes? There are considerable design philosophy differences where human life is directly at risk and hazardous inventories are involved. • What is the Verification and Underwriting Design verification, underwriting Process? and insurance will be required to gain approvals. • What Deficiencies exist in Input Data to the Are there areas such as wave Design Process? incidence, height, spectral information or persistence data missing for important sectors of the seas around the UK?
4.1.2 Potential for Technology Transfer
Applicable Regulations
The Health and Safety Executive (HSE) Regulations that apply to unmanned Wave Energy Devices were clarified at the Technology Workshop. They are: • Health and Safety at Work Act (HSWA) • Construction Design Management (CDM) Regulations • Management Regulations. A Wave Energy Device does not fall into the same category as an offshore installation. Amendments are being made to the HSWA to classify Wave and Wind
Page 14 Energy Converters as “Energy Structures”. A period of open consultation concluded on 11 August 2000. The amended regulations will come into force in mid 2001. The expected definition will be, “A fixed or floating structure, other than a vessel, for producing energy from wind or water.” WECs which supply power to an offshore installation will be classified as a “Supplementary Units”. They will be regarded as part of the installation which they support and Safety Case Regulations will apply. There is currently no reason to believe that WEC Prototypes will be viewed any differently from Full Scale WEC Power Stations. Planning Approvals and Licensing Route Currently, WEC Planning may require the approval of many authorities: • The Health and Safety Executive • Local and Central Government • Crown Estates • Fishing Industry • Shipping Authorities Wind Energy companies have found the approvals process for offshore wind farms to be time consuming and complex. Approvals for the Blyth Wind farm took around one year and involved applications to thirteen different bodies. Since then, Wind Energy Companies have worked with the various authorities to streamline the procedure within 12 miles of the shoreline. This may assist at shore and near shore WECs. An exercise has been carried out in the Irish Republic to streamline the approvals process[1.14]. A similar study to investigate approvals in the UK will be useful for WECs. Design Codes Specific design codes for WECs do not currently exist, however there are a large number of different codes which may be used to design offshore structures: Det Norske Veritas (DnV), American Petroleum Institute (API), British Standard (BS), [1.1] to [1.12]. Extensive offshore industry engineering experience exists in selecting the correct parts of these codes and combining them in a consistent and compatible manner. This experience will be very useful to Wave Energy Teams during the design process. Verification and Underwriting Process Lloyd’s Register and Det Norske Veritas are commonly involved in design verification of vessels and offshore structures in the oil and gas industry. The process for verification of WECs would be similar. The legislative framework would, as always, take account of the National Authorities, International Law, Existing Regulations (see Applicable Regulations above). Each design would be required to produce a functional specification and performance criteria and would be judged to applicable engineering standards. Some level of risk assessment should also be expected. The key issues for the design verification will be:
Page 15 • Performance issues Design life, maintainability and power output. • Safety issues Risks to personnel during construction, installation and operation, loss of structural integrity or vessel worthiness and interference with other users; shipping channels, etc. • Environmental issues Visual impact, fisheries, waste and emissions.
Data Deficiencies Considerable work was done as part of the former Department of Energy’s wave energy programme and by Queen’s University Belfast in the 1990s on Metocean Data gathering and interpretation. However, it has been suggested that Metocean data deficiencies may exist in the following areas for near coastal areas for the development of coastal WECs: • Coastal wave spectra, scatter diagrams, persistence data • Coastal wave shapes and fluid loading These issues have, for near and offshore uses in the North Sea and more recently West of Shetlands, all been well researched and documented by the Offshore Oil and Gas Industry. Omissions certainly exist for coastal areas. However, it is unlikely that these omissions will seriously affect the structural design of a coastal structure such as a breakwater or seawall as their design is covered by the British Standard for Maritime Structures [1.10] and the American Army Shore Protection Manual [1.11]. A special case not covered by the codes is the inside of an OWC chamber. The JONSWAP (Joint North Sea Wave Project) Spectrum is commonly used for offshore platform design for fetch or duration limited seas. Other spectra commonly used are the Bretschneider and Pierson-Moskowitz spectra [1.1]. Scatter diagrams and persistence data applicable to near and offshore locations are also abundant. Their applicability for near coastal waves is questionable and incorrect wave statistical modelling will affect the prediction of power output from coastal devices. Near and offshore wave shapes and fluid loading have been exhaustively examined for the type of structure commonly encountered in the offshore oil and gas industry. Morison’s equation and diffraction analysis methods [1.1] are commonly used to predict loading on fixed structures and floating bodies. For coastal areas, there is considerably less data and design codes are more empirical [1.10, 1.11, 1.12]. For offshore sites (see favoured Wave Energy Locations from [1.13], Figure 4.1), Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial; i.e. BP Foinaven and Schiehallion.
4.1.3 Generic Research and Development Needs No generic R & D needs were identified. Although gaps in data exist (see previous sub-section), these are considered to be for coastal schemes only and are specific to location.
4.1.4 Conclusions and Recommendations The major conclusions of this sector are:
Page 16 • The Planning and Approvals process for at shore and near shore WEC schemes should benefit from the recent work carried out by the Wind Energy Industry. The approvals process for WECs requires clarification, and a study, similar to the one carried out in Ireland, should be commissioned. • The Design and Verification Processes are well established for the Offshore Oil and Gas and Shipping Industries. These methods can be readily transferred to the design and verification of WECs. • Although some data gaps exist, particularly for coastal areas, no generic research is recommended because each data gathering exercise will be site specific. Structural designs can be established based on existing offshore oil and gas and shipping industry methods and data. Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial.
4.1.5 References [1.1] Dynamics of Fixed Marine Structures, Barltrop and Adams, 3rd Edition, Butterworth and Heinemann, 1991. [1.2] Floating Structures; A Guide for Design and Analysis, Barltrop, Oilfield Publications, Inc., 1998. [1.3] Health and Safety Executive, (HSE), Offshore Installations: Guidance on Design, Construction and Certification, 4th Edition and Amendments to 1996, London HMSO. [1.4] American Petroleum Institute (API), Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Allowable Stress (API-RP2A-WSD 20th Edition, 1993 or Load and Resistance Factor (API- RP2A-LRFD 1st Edition, 1993), etc. [1.5] Det Norske Veritas, (DnV), Guidelines and Classification Notes for Fixed Platforms, 1998, Mobile Offshore Platforms, 2000. [1.6] American Bureau of Shipping (ABS), Rules for Building and Classing Steel Barges, 1991; Steel Vessels, 1999. [1.7] Lloyds’ Register, Rules and Regulations for the Classification of Fixed Offshore Installations, 1989, Mobile Offshore Units, 1996, Ships, 1999. [1.8] British Standard for Structural Use of Concrete, BS 8110: 1997. [1.9] British Standard for Structural Use of Steel, BS5950: 1995. [1.10] British Standard of Maritime Structures, BS 6349. [1.11] American Coastal Engineering Research Centre; Shore Protection Manual, 4th Edition, 1984. [1.12] Rock Armour Manual, CIRIA. [1.13] Wave Energy, The Department of Energy’s R&D Programme 1974 -1983, ETSU for the Department of Energy, March 1985. [1.14] Discussion Document on Policy for Offshore Wind and Wave Electricity Generation, Irish Ministry for Marine and Natural Resources, February 2000.
Page 17 4.2 Construction Methods and Project Cost Estimation
4.2.1 Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: How to estimate project costs accurately This major issue is necessary for within the design process? WEC teams to make cost effective design decisions. What yards/ factories/ contractors are Information on fabrication available? facilities significantly affects detailed designs. • What construction/ fabrication methods and Fabrication information can guidelines can be considered? significantly affect detailed design.
4.2.2 Potential for Technology Transfer Cost Estimation The Offshore Oil and Gas, Onshore Civils and Manufacturing Industries have the means to accurately cost projects of this nature. Engineering Consultancies routinely need to estimate project costs for construction, installation and operation with only a conceptual design available. Most of this experience exists within Engineering Consultants and is regularly updated by new live projects and input from Fabricators, Installation Contractors and Operators [2.3]. In addition, Fabricators and Installation Contractors have excellent means of estimating their own yard or vessel costs. However, both parties tend to be reluctant to divulge this information as it is considered commercially sensitive.
In short, suitable costing databases and costing methods exist and this experience and data needs to be accessed to carry out accurate cost estimates for WEC prototype development and, subsequently, WEC power station development.
Only when the design process encompasses all the project driving issues of construction, installation and operation, can true life cycle costing estimates be achieved.
However, notice should be taken of the differences between wave energy devices and offshore installations within these cost estimates. Most offshore oil and gas projects are prototypes with a complete design process applied to each project. Wave energy projects are not considered viable if this approach is adopted here. The returns on investment are much lower. The wave energy industry should endeavour to select costs and technology gained in the offshore oil and gas industry, but, at the same time, to realise economies of scale and repeatability of design to keep costs down.
Available Contractors The next step for each WEC team is to include input from construction/ installation experts and, ideally, the potential fabricator and installation contractor. This input
Page 18 should initially take the form of collaboration at concept definition stage and subsequently partnerships or alliances should be formed to include designers, fabricators, installers and operators. Directories are readily available giving contact details by technological area in the onshore and offshore construction industries [2.1], [2.2]. Construction and Fabrication Guidelines A great deal of experience has been gained in the onshore and offshore construction industries as to the most cost effective ways of realising concrete and steel construction (Figures 4.2, 4.3). All fabricators will be able to give high level guidance about material usage, stockpiles, and favoured fabrication methods. The design can and should be modified to suit as far as possible. Successful inclusion of fabricator input at the concept design stage will minimise design complexity, the chance of failure and unforeseen increases in fabrication costs.
4.2.3 Generic Research and Development Needs In general, no generic technical work can or should be done to support the industry as a whole. Each device team would benefit from seeking advice from one of the industries identified above. All conceptual WEC schemes need to be subjected to Detailed Design, Fabricator and Installation Contractor Input and Cost Estimation along the lines outlined above. This can be done on a scheme by scheme basis by the WEC team contacting an appropriate contractor and engaging in discussions as to how cost savings can be achieved. For example, cheaper materials may be available for re-use, construction methods may offer considerable savings if a small design change is made, or economies of scale could be explored. To facilitate this process, a study should be commissioned to prepare a contact list of contractors interested in becoming involved with WEC teams and willing to engage in discussions. This should include: • Onshore and Offshore Construction Yards (Steel and Concrete) • Shipyards • Manufacturing Industry • Construction Technologists and Consultants • Installation Contractors (see also Marine Operations) A start has been made as part of this project (see Contacts Database, Appendix A), but a more complete and thorough review of all relevant industries; offshore oil and gas, coastal protection, onshore construction and manufacturing industry taking in suppliers of conventional materials as well as those supplying more exotic materials such as plastics and alloys. It is recommended that a second study be commissioned to summarise simple construction and installation guidelines for steel and concrete construction with the goal of short-circuiting the WEC prototype design cycles and estimating realistic final project costs at an early stage of development. This study could be combined with the Wind Energy sector which is also currently extremely interested in construction and installation method guidelines.
Page 19 4.2.4 Conclusions and Recommendations All the above issues are symptomatic of the Wave Energy Industry making the initial steps from Research and Development Projects to Prototype and Power Station Developments. The major conclusions of this sector are: • Significant opportunity for transfer of costing information and methods exists from the Offshore Oil and Gas, Onshore Civils and Manufacturing Industries. However, notice should be taken of the differences between wave energy devices and offshore installations within these cost estimates. Most offshore oil and gas projects are prototypes with a complete design process applied to each project. Wave energy projects are not considered viable if this approach is adopted here. The returns on investment are much lower. The wave energy industry should endeavour to select costs and technology gained in the offshore oil and gas industry, but, at the same time, to realise economies of scale and repeatability of design to keep costs down. • A study is recommended to prepare a full contact list of all parties interested in being or becoming involved in WEC schemes. This to facilitate the design process of WEC prototypes and power stations and to enable more reliable cost estimates to be achieved. • A study is recommended outlining fabrication and installation guidelines for WEC schemes to be produced from steel and concrete in offshore and onshore industry facilities. This should include manufacturing guidelines for WEC schemes that are likely to benefit from the production line manufacturing philosophy.
4.2.5 References [2.1] Offshore Oil and Gas Directory; published annually, Miller Freeman Information Services, Tel: 01732 367301, http://www.mfplc.com. [2.2] Maritime Guide (Dry Docks, Shipbuilders Directory), ISBN 1900839156, Lloyds Register of Shipping, 1997. [2.3] SPON’s European Construction Costs Handbook, Edited by Davis Langdon and Everest, Third Edition, currently in production.
Page 20 4.3 Marine Operations
4.3.1 Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: • What Marine Operations can be All near shore and offshore WECs considered? need to be transported to site and installed. The available technology, procedures and costs require investigation. • Metocean Data Marine operations will be subject to prevailing weather conditions. Major cost and safety consequences result from poor statistical data and inadequate contingency planning. • Risk and Safety Assessments These will be required to meet HSE approvals and to gain verification.
4.3.2 Potential for Technology Transfer
Installation Guidelines A great deal of experience has been gained in the offshore oil and gas industries on the most cost effective ways of performing marine operations (Figure 4.3, 4.4). A vast array of vessels are now available [3.2] to carry out a variety of offshore tasks; lifting operations, transport operations, diver support, Remote Operating Vehicle (ROV) deployment, cable laying, pipelaying, trenching, etc. Acceptable sea states for vessel operation and different marine procedures are well known by Marine Contractors. The basic guidelines for planning offshore operations should be: • To be well informed of Metocean data statistics and forecasting • To minimise activities and time offshore • To minimise exposure to unfavourable weather conditions with knock-on delays and exponential cost increases • To plan for contingencies WEC designs should include careful consideration of these guidelines from early conceptual planning. This should be done by the teams including early input from marine operations experts and, ideally, the would be installation contractor. Successful inclusion of marine operations input and inclusion of the temporary condition load cases in the design at the concept design stage will minimise the chance of design complexity, offshore failure and unforeseen increases in marine operations costs.
Page 21 To facilitate this process, a study should be commissioned to prepare a contact list of Installation Contractors interested in becoming involved with WEC teams. This should include Operators of: • Tugs • Crane Vessels • Pipe Laying Vessels • Cable Laying Vessels • Piling Vessels • Construction Jack-ups • Diving Spreads and Diver Support Vessels • Remote Operating Vehicle (ROV) Suppliers • Marine Operations Technologists
The study should include a summary of marine operations guidelines and approximate day rates and mobilisation costs with the goal of enabling the WEC teams to make informed decisions on these cost driving issues at an early part of the design process. Published directories exist giving contacts of vessel owners and operators, as well as marine technologists [3.1], [3.2]. Metocean Data Metocean data collected for use by offshore operators will help WEC teams to identify an installation weather window. This data will tend to be limited to those areas used by Oil and Gas Operators for platform sites, tow routes or pipeline routes. Hence, significant data exists from past and current projects in the North Sea and more recently, and more pertinently perhaps, the West of Shetlands area. Some sources of available data in the North Sea are given in references [3.3], [3.4]. Deficiencies in data have been identified in some coastal areas; see Section 4.1 for recommendations. Risk and Safety Assessments Risk and Safety Assessments are now well embedded in the Design Process for all Offshore Oil and Gas Facilities. Within UK waters, the Health and Safety Executive introduced a requirement to provide an Operational Safety Case for (A case for the safety of) all offshore Oil and Gas facilities following the Piper Alpha disaster of 1988. These typically consist of hazard assessment studies, consequence and risk assessment studies which, taken together with the ‘ALARP’ principle (As Low As Reasonably Practicable), argue the case for the Operator having taken due care and attention in the design and operation of the facility. Similar issues will need to be assessed as part of the design process for WEC schemes, although current legislation is not expected to require as comprehensive an assessment as is typically required for offshore oil and gas facilities. This is largely because of the relatively low risk to human life and environmental damage associated with WEC schemes. Several companies have developed in the last ten years who specialise in these safety assessments for all types of offshore operations [3.1].
4.3.3 Generic Research and Development Needs No generic needs have been identified in this area.
Page 22 There are many different types of WECs and each requires different marine operations. It is difficult to identify common ground where a generic study would benefit the whole industry. The Offshore Industry has installed a wide range of structures and the current range of WECs could be installed as a matter of routine.
4.3.4 Conclusions and Recommendations All the above issues are symptomatic of the Wave Energy Industry making the initial steps from Research and Development Projects to Offshore Prototype and Power Station Development. The major conclusions of this sector are: • Each device team would benefit from collaboration with the offshore industry in the above Key Technology Transfer issues. • All conceptual WEC schemes need to be subjected to Marine Operations Input and Cost Estimation and Risk and Safety Assessment as part of the Design Process. This should be done on a scheme by scheme basis by the WEC team contacting the Installation Contractor and engaging in discussions as to how cost savings can be achieved. • To facilitate this process, a study should be commissioned to prepare a contact list of Installation Contractors interested in becoming involved with WEC teams. The study should include a summary of marine operations guidelines and approximate day rates and mobilisation costs with the goal of enabling the WEC teams to make informed decisions on these cost driving issues at an early part of the design process. • Offshore Operators can be recruited to supply Metocean data for tows and installation weather windows.
4.3.5 References [3.1] Offshore Oil and Gas Directory; published annually, Miller Freeman Information Services, Tel: 01732 367301, http://www.mfplc.com. [3.2] Construction Vessels of the World, 5 th Edition, OPL, Oilfield Publications Ltd. [3.3] Health and Safety Executive, (HSE), Offshore Installations: Guidance on Design, Construction and Certification, 4th Edition and Amendments to 1996, London HMSO. [3.4] Meteorological Office Home Page; http://www.meto.gov.uk/.
Page 23 4.4 Mooring Systems
4.4.1 Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: • New Developments Taut Moorings, Synthetic Fibre Ropes, Floating Production, Storage and Offloading (FPSO)s, Tanker Offloading Systems, Dynamic Positioning Systems • Reliability and Maintainability All offshore WECs will be moored in some way to the seabed. The reliability of these systems will be paramount to their successful deployment, operation and verification. • Deployment and Retrieval Quick Release/ Re-attachment
4.4.2 Potential for Technology Transfer New Developments Great potential for transfer of technology exists from the Offshore Industry to the Wave Energy Industry [4.1], [4.2]. Relevant technologies are Floating Production, Storage and Offloading (FPSO) systems. Of particular interest, because of their location, will be the recent experience West of Shetlands in the BP Foinavon and Schiehallion Fields. Also relevant are recent developments in Tanker Offloading Systems in general, as well as the use of Dynamic Positioning Systems in vessels which may be maintaining the WEC schemes. A major development in offshore mooring systems has been the use of synthetic ropes and taut leg moorings. The Campos Basin B27 installation is a good example. Synthetic ropes [4.2] potentially offer significant advantages over a conventional mooring line. They have a much higher strength to weight ratio and improved extreme dynamic tensions. The lower weight reduces some of the buoyancy required by a traditional catenary. Taut leg moorings may be of interest to developing WEC Schemes located in deep water. They have a smaller footprint and smaller wave frequency tensions than a catenary mooring system. The latter property could prove advantageous for snatch loading which was identified as an issue by one of the device teams. These recent developments could be utilised in the designs for Offshore WEC Schemes under certain circumstances.
4.4.3 Generic Research and Development Needs Reliability and Maintainability The Offshore Oil and Gas Industry has considerable experience in the reliability of key components in the design and operation of offshore facilities. However, it is understood that long term fatigue issues of lines and connection points at either end have not been analysed in detail to date. A useful study could be commissioned to
Page 24 address this. The issues and references are discussed in Operation and Maintenance (Chapter 4.5). Deployment and Retrieval The Offshore Oil and Gas Industry now has considerable experience in the installation of buoys and mooring systems. A means of quick release and re-attachment between WEC devices and its mooring system for change out and retrieval has been identified as a potential technological issue. A specific review of the available technology for achieving this would be valuable and, it is recommended that the development of a standard connection detail resilient to extreme and fatigue loads should be supported. All offshore WECs will benefit from this development. As part of the above study, the design of the means of connecting subsea dynamic cables to WEC devices should also be considered; either along mooring lines or as a separate system. The connector for the cable should also be considered and it is recommended that the search for a standard connection design should be supported. A series of mooring studies for the major different types of Wave Energy Devices would provide useful generic information; essentially a technology and cost audit of leading WECs. The costs associated with laying anchors and mooring lines (site investigations, marine operations) represent a high proportion of project capital expenditure. For prototype testing, these one off costs are prohibitively high. A WEC test site would encourage prototype testing. In addition, current numerical modelling techniques for motion predictions of individual units are good, but for arrays of floating devices are limited. Software should be developed to improve this as the expected configuration of offshore WECs will be in groups of devices.
4.4.4 Conclusions and Recommendations Mooring systems used in current WEC designs are mainly conventional systems, such as a catenary or angel and sinker. They use chain or wire with concrete gravity blocks or a pull in anchor. The major conclusions of this sector are: • Great potential for transfer of technology exists from the Offshore Industry to the Wave Energy Industry. Particular reference should be made to recent developments in the use of synthetic ropes and taut moorings. • Generic studies are recommended into the following Key Technology Issues; long term fatigue issues of lines and connection points, standard connector designs for the quick release and re-attachment of mooring systems and subsea cables. • A series of mooring studies for the major different types of Wave Energy Devices would provide useful generic information; essentially a technology and cost audit of leading WECs. • Software development is recommended in the area of predictive modelling of the motions of arrays of devices in a given sea-state.
Page 25 4.4.5 References [4.1] Single Point Moorings of the World, Halyard Offshore, OPL, Oilfield Publications Limited. [4.2] Deepwater Fibre Moorings; An Engineers’ Design Guide, Noble Denton, OPL, Oilfield Publications Limited.
Page 26 4.5 Operations and Maintenance
4.5.1 Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: • How to Keep Operational Development of a maintenance strategy Costs Down? sufficiently robust to withstand minimal routine maintenance and plan for major refits as required is a goal of all WEC teams. 4.5.2 Potential for Technology Transfer This technology area can be addressed largely by transfer of knowledge and technology from the offshore oil and gas industry. To achieve the above target, the WEC operational strategy and design criteria should be: • Design for Unmanned Operation • Design for Zero Maintenance • Design for Long Distance Performance Monitoring • Design for Annual Inspections (or less frequent inspections) in calm weather periods • If major refits are required, affected parts of the device should be retrieved, returned to shore and replaced. These criteria are similar to the design criteria for unmanned offshore oil and gas facilities, notably subsea installations, buoys, tanker offloading systems and not- normally-manned installations.
For inspection and light maintenance activities, Diving Intervention and Dedicated Remote Operating Vehicles (Figure 4.5) can be considered, but costs are high, safety issues would need to be addressed, and use should be limited to annual inspections or less often. It follows that the vessels, operational strategies and material selection used for these facilities may also be relevant for the design of the WEC schemes. The MET office can offer predictions of suitable weather windows and past data for the preparation of O & M procedures of wave energy devices. Five day weather predictions are offered by the MET in support of operational and installation decisions. A desk study is recommended to describe how the offshore oil and gas industry currently undertakes inspection and monitoring of subsea or unmanned floating or fixed facilities, maintenance and repair (for example how change out operations are performed for subsea units). This would also include a list of contacts in this industry for suppliers of technology and services of this nature.
4.5.3 Generic Research and Development Needs No generic technical needs have been identified; operational strategies will be very dependent on WEC device types.
Page 27 As discussed in Section 4.3, Marine Operations, WEC Design Operational Strategies should be prepared in consultation with Vessel Operators and designs should be selected which minimise maintenance, inspection and repair activities.
4.5.4 Conclusions and Recommendations The major conclusions of this sector are: • Great potential for transfer of technology exists from the Offshore Industry. • No generic technical needs have been identified; operational strategies will be very dependent on WEC device types. • A desk study is recommended to describe how the offshore oil and gas industry currently undertakes inspection and monitoring of subsea or unmanned floating or fixed facilities.
Page 28 4.6 Materials
4.6.1 Key Technology Issues The following issues were identified as a result of industry interviews and from the Technology Workshop: • What Corrosion Strategies can be considered? • How to achieve a balance between low cost and high performance materials? • How to carry out Life Cycle Analyses? WEC teams made the following additional requests during the workshop: • Information on trends in reliability of materials. • Erosion of rust due to wave action and water-borne solids.
4.6.2 Potential for Technology Transfer The opportunity exists for the technology and experience gained from the offshore oil and gas industry to benefit the WEC teams. The performance of the two most commonly used materials (steel and concrete) likely to be utilised by the WEC industry for the main structure in the offshore environment is well understood. In component manufacture, more exotic materials are more likely to be relevant, and here again, current industry experience should be exploited. Primary material producers, e.g. Corns in the case of steel or Avesta Sheffield in the case of stainless steels, are good and reliable sources of information. Technology transfer in the form of either material processing or manufacturing technology or proprietary products may prove to be beneficial, e.g. the wind energy industry is currently adopting the use of a product known as ‘Bi-steel’, produced by Corns, which may have potential in wave energy devices. Corrosion Strategy Corrosion strategies for the protection of steel can be prepared on the basis of well proven predictive methods and reliability data. Strategies [6.1, 6.2] can involve: • Coatings, • Cathodic protection • Corrosion allowances, • Adopting more corrosion resilient alternatives, or • A combination of the above However, it should be noted that corrosion protection control with respect to conventional offshore structures is based upon service life requirement of 20 to 30 years. For structures with longer lives the approaches given in the references may need modification. Concrete is highly durable in the marine environment as long as adequate cover is included in the design and quality control procedures are maintained throughout the construction process. This is demonstrated by the concrete substructures used by the oil and gas industry. Usually, no additional maintenance or repair is required.
Page 29 WEC teams are currently concentrating on proving prototypes with relatively short design lives. Accordingly, corrosion resistance is not a high priority. This will, however, become of greater importance during WEC Power Station development. Balance between Low Cost and High Performance Materials Achieving this balance is the goal of all designers. The most fruitful way of achieving this is to consult relevant materials specialists and suppliers who are able to predict behaviour and refine designs and operational strategies in consultation. Life Cycle Analysis Life cycle analysis or life cycle costing is increasingly becoming a key driver in material selection, and is an issue that successful designs cannot ignore. In very simplistic terms it enables an appropriate balance to be achieved between capital and operational costs of materials within the design process. The importance of life cycle costing in the design process has been internationally recognised through the publication of an ISO standard, [6.3]. It is understood that work is in hand drafting a specific part of the ISO standard which deals specifically with maintenance and life cycle costing, but the likely publication date is unknown. The methods of Life Cycle Costing are well established and can be readily applied to WEC schemes. Reliability of Materials (trends) Reliability performance of materials in particular application can be gained directly from primary materials producers. Alternatively, specific data can be sourced from OREDA [6.4]. Erosion Damage Some erosion damage has been reported in association with turbine blades used in OWCs. This is assumed to be the result of water droplets entrained in the air stream passing through the turbine impinging on the blades. This issue may be addressed through technology transfer. Generic Research and Development Needs A huge range of materials with widely different properties are currently used everyday for applications in offshore environments. The development of ‘new’ materials for the WEC industry in isolation is not considered necessary.
4.6.3 Conclusions and Recommendations The major conclusions of this sector are: • The opportunity exists for the technology and experience gained from the offshore oil and gas industry to benefit the WEC teams. • A reliability data library and contact database should be set up to include materials data and suppliers of materials likely to be instrumental in the development of WEC schemes. • No generic research and development work is recommended.
Page 30 4.6.4 References [6.1] NACE RP176-94. Corrosion Control of Fixed Offshore Platforms Associated with Petroleum Production. [6.2] DnV RP B401, Recommended Practice Cathodic Protection Design, 1993. [6.3] ISO 15686: Building and Constructed Assets - Service Life Planning - General Principles. [6.4] Offshore Reliability Data Handbook, 3rd Edition, OREDA Participants, 1997.
Page 31 4.7 Hydraulic Systems
4.7.1 Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: • Hydraulic fluids Hydraulic fluid containment is an issue for performance and environmental reasons, as oil based fluids might leak. • Power conversion and There did not appear to be any consensus on transmission the question of hydraulic power conversion. Each team appears to be pursuing its own concept and the designs are quite disparate. Questions may arise in the future as to which concepts should be progressed towards commercialisation and how the potential viability of such concepts should be evaluated prior to significant levels of support. • System integrity Long term survival and response to extreme environmental events was recognised as a potential problem for the majority of WECs using hydraulic power takeoff.
4.7.2 Potential for Technology Transfer Hydraulic fluids If oil is used as a medium, containment must be the priority. The performance and durability of dynamic hydraulic seals is currently seen as a problem. Whereas static seals are widely used in many applications and high standards are achievable, the performance of dynamic seals depends on a number of factors, including distance and velocity of travel, quality and retention of surface finish, and the cleanliness of hydraulic fluid and the surrounding media. The potential for technology transfer is likely to be limited and may come from areas where maintenance is highly restricted, e.g. offshore engineering. Power conversion and transmission Component parts of hydraulic systems are already widely used in many industries. Wave power requires an element of role reversal. Hydraulic rams, used typically as actuators in industry, will be required in wave power, in one configuration or another, to act as pumps. Rotary hydraulic machines, used more commonly as pumps in industry, would be required by wave power to act solely as motors. The opportunities for technology transfer may be application specific, taking into account such facts as speed and torque capacity, controllability, part load performance and efficiency. Rectification generally takes place in hydraulic systems through the use of non-return valves. Throttling losses in such devices may detract from efficiency, especially at part load. Development of alternatives could be of value. Material choice will be
Page 32 relevant should designers opt for water-based hydraulic fluids if longevity is to be achieved and performance maintained. Published literature suggests that hydraulic accumulators suitable for wave power duty for multi-wave storage are likely to be very costly. Some form of short term energy storage (intra-wave) is nevertheless essential if fluctuations in hydraulic pressure are to be avoided during the power generation cycle. Compressed gas offers the most obvious basis for workable hydraulic accumulators. Issues likely to arise are containment, sealing, choice of fluids and the provision of a suitable gas-liquid interface. There could be some benefit in linking clusters of devices together and combining their outputs in common generation systems. System integrity Corrosion, erosion and protection of working metal surfaces in an aggressive environment are important for long term survival. Hydraulic use in other industries has shown long term performance and reliability depend on low rates of wear of fundamental hydraulic components and seals and long life hydraulic fluids. These in turn tend to be dependent on velocities and distances of travel. Maintainability is a problem. There was general recognition that maintenance intervals should be as long as practicable and that the practicability of maintenance of devices at sea is highly problematic, if not impossible. Designs should therefore allow for shore based maintenance at the concept stage. Survival in the extreme event takes two forms: • the “end stop” problem of hydraulic rams exceeding their design travel • the high forces imposed during extreme events, especially if linear devices are designed with limited travel. There is a generic problem which relates to the application of fender type systems to absorb energy and reduce forces at the end stop problem. All such mechanical devices require similar systems and the transfer of technology from the fendering industry could be investigated.
4.7.3 Generic Research and Development Needs Hydraulic fluids The workshop participants recognised the theoretical benefits of fresh water or seawater as a hydraulic fluid. This is not well established although the difficulties in using water and water based fluids seemed to be well recognised. It was suggested that leakage rates using water based fluids could exceed those for high viscosity fluids one thousand-fold. Specific sealing problems included temperature, pressure, speed, size, cycling and deposition of solids. Dynamic seal performance is currently not well understood. There is a specific requirement for the testing and development of suitable materials for long term dynamic sealing for wave energy applications. Power conversion and transmission In line with the published literature, little interest was shown at the workshop in remote hydraulic power transmission. It was generally considered that any potential benefits would be outweighed by the disadvantages of long and costly pipework systems, pressure losses and the potential for water hammer.
Page 33 Because of the specific requirements of WEC systems it may be necessary in the long term to develop a whole new family of hydraulic devices to cope with these. The part load performance of existing hydraulic systems must be investigated.
4.7.4 Conclusions and Recommendations The major conclusions of this sector are: • Static seal technology is well advanced. Dynamic seal technology needs to be developed. The use of oil as a hydraulic fluid is well established technology. An elegant and environmentally friendly solution would be to use water as the hydraulic fluid, but considerable research will be required in this area to achieve adequate seal effectiveness here. • The component parts for a WEC prototype with a hydraulic take off mechanism already exist. Technology should be transferred from other industries to facilitate prototype development. For full scale WEC power stations with a longer design life than a prototype development work is required to improve reliability and economic returns. To prepare for WEC Power Station deployment in the medium term, the following research and development activities are recommended: • Dynamic Seal development and testing is undertaken to extend the design life of a system. • A study of the potential for the Fendering industry to mitigate the “end-stop” problem. • Development of hydraulic machines (motors with low part load losses, high torque pumps). • Development of systems using water as the hydraulic fluid.
Page 34 4.8 Pneumatic Systems
4.8.1 Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: • Turbine development Self rectifying air turbines are used in all OWCs, but which type is the best? • Reliability and There is limited data available on the long term Maintainability performance of Wells Turbines (Figure 4.6).
4.8.2 Potential for Technology Transfer Turbine development This type of system is rather specific to WEC devices so there are not many other industries which could contribute here. The design and fabrication of turbine blades using novel materials could be transferred from the aircraft industry. Reliability and Maintainability Benefit may be derived from the Wind Energy Industry in generic matters such as value engineering, long maintenance life and, from future offshore wind developments, resistance to aggressive environments and electrical connections.
4.8.3 Generic Research and Development Turbine Development Initial experience of pneumatic transmission is with the Wells turbine in single row configuration. This technology has been demonstrated and shown to work in several locations worldwide. Recent developments of the concept include twin rotor machines and the use of guide vanes. Alternatives to the Wells turbine which are near demonstration are reported to include a self rectifying design of impulse turbine and a variable pitch aerofoil turbine. There is little information available on the mechanical efficiency of the basic Wells configuration or the potential benefits of the more highly developed versions. It is therefore not clear at this stage whether there would be economic merit in developing the concept further on account of uncertainties over: • the improvements in efficiency potentially available • the likely demand for onshore devices, which are site specific and probably unsuitable for large scale implementation on account of visual intrusion and acoustic disturbance. These devices may therefore be limited in their potential for large scale development but will be a means of raising the immediate profile of wave energy. Interest was however expressed at the Workshop in the comparative testing of different types of turbine and improvements in durability in respect of bearings and blade erosion of high performance aerodynamic machinery in marine environments.
Page 35 4.8.4 Conclusions and Recommendations The major conclusions of this sector are: • Pneumatic turbines are most suited to operation in an at shore WEC (rather than near shore or off shore). At shore WECs are a maturing technology although a few areas for development do still exist. • It is recommended that a series of turbine trials be undertaken in one facility to test the various turbines and their efficiency.
Page 36 4.9 Subsea Cables and Connectors
4.9.1 Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: • How to select and install Cables, Connectors and their Installation are cables and connectors at low generally high cost items. How can this cost be cost? reduced? • Can cables be used with Buoyant Moored and Hinged Contour WECs may flexible moorings? require a flexible power connection. What is established practice for use in these circumstances? • Reliability and Maintenance Design Life and Reliability of Cables will significantly affect overall WEC project costs. This is not a technology area developed in detail by Wave Energy Teams to date. They generally believe the technology essentially exists and the major barrier is its cost. Most hope that sponsorship can be gained for offshore prototype schemes for the relatively short distances required to prove the prototypes. In the longer term, it is hoped that economies of scale will result in overall project cost reductions per unit power generated. Many hope that prices will also fall following standardisation and mass production of subsea connectors and the expansion of offshore wind and WEC Power Stations.
4.9.2 Potential for Technology Transfer There is considerable potential for transfer of technology from both static and dynamic cables and subsea/ wet matable connector experience in the offshore oil and gas industry. Cable and Connector Selection and Cable Laying - Cost Issues The Power Transmission Industry and the Offshore Oil and Gas Industry has laid static high voltage cables subsea to provide power to isolated communities and offshore platforms and facilities. Typically, these are laid by dedicated cable laying vessels and a typical lay rate of 5km/ day can be expected. More recently, the Offshore Oil and Gas Industry has also developed dynamic cable technology which will be extremely attractive for WEC schemes as they move offshore. Cable selection and WEC scheme location needs to take account of the following general guidelines. • The process of cable laying makes up a significant part of the total cost. The vessel used is an important consideration; it should be selected in consultation with an experienced operator. Typical considerations are: Weather This is affected by the location and the time of year. A large vessel will have a higher day rate than a smaller vessel. However, the larger vessel will be able to operate in more extreme sea states and will have less down time from weather than a smaller vessel. This increased productive use of paid
Page 37 time can make a larger vessel more economic than a smaller one. Cable quantity The required deck space for the cable increases with the cable length and the minimum bend radius. Water depth A deep water depth creates a high tension in the cable as it is laid and hence increases the required vessel buoyancy. Seabed conditions A cable damage assessment and seabed investigation will be carried out and protection for the cable chosen (exposed, covered or buried). Depending on the type of protection and seabed conditions, Dynamic Positioning (DP) may be required or a Remote Operating Vehicle (ROV). An ROV will be required to avoid freespans if seabed contours suggest that this may be likely. Current regime Both tidal and dominant currents are factors. It is possible to lay cables in currents up to 4-5 knots near the seabed. • Static cables are significantly less expensive than dynamic cables so should be used over long distances. Dynamic cables should be considered for connecting a floating offshore WEC scheme to the seabed or to each other (if appropriate). To give an idea of the state of the art; in 1996, the Troll Platform in the Norwegian Sector of the North Sea was connected to shore via a static AC cable; 20MW power, 67km length at 52kV. The cable contains 3No. core 240mm2 cables and is protected by an XLPE lead sheath (Figure 4.7); in the vicinity of the Asgard platform dynamic supply cables have been installed for the heating of pipelines. The cable contains 4No. core 1600mm 2 cables at 12kV and has 210mm outer diameter and unit weight 135kg/m (Figure 4.8); dynamic cables have been designed for up to 90kV voltage level. Dynamic cables have been installed in up to 400m water. • Lower voltage cables are less expensive to fabricate. However, lower voltage cables experience greater percentage electrical losses. 3 core AC submarine cables can be used up to 70-80 km route length. Beyond this, percentage losses or project costs become unacceptable. Polymer insulated submarine cables can be used up to 145kV voltage level. A wet design philosophy may be used up to 36kV. Above this voltage, radial water blocking is required and connector costs increase. • Shorter Cables are less expensive, but since a large component of the cost will be for mobilisation of a vessel, the laying of a short length of cable may well be similar in cost in the laying of a long one. Key factors which influence the costs are vessel availability, seabed material, current regime, weather, cable size, water depth and beaching. Cables can be buried on a sand bed using water jets which avoids the need to excavate a trench. Cables lade on a rock bed must be buried by rock dumping. • Connectors increase in cost with size and the need for protection from water ingress. All connectors for small WECs will need to be of the “wet” rather than “dry” type. The cost of connectors is high although a significant part of this cost is associated with the marine operations rather than the material and fabrication costs. Connectors currently in use are over-specified from the point of view of a WEC. Typically a connector for an oil and gas project is designed to be fitted underwater by a ROV. There is potential to rewrite this specification for use with WECs and reduce the price.
Page 38 Use with flexible moorings systems Flexible connections are widely used in the offshore industry. A good example is shown schematically in Figure 4.9. It is important to consider the cabling in the mooring analysis and to ensure the connector rigidity is less than that of the moorings. Heavy cables can affect device behaviour significantly, especially if the device is small and lightweight. They will cause the WEC to attract additional drag, and in extreme cases additional buoyancy may be required on the WEC. Flexible moorings are usually used in deep water (greater than 60m), if they are used in shallower water the cable may experience significant wear at the seabed. Specific protection with bend restrictors needs to be designed here. Reliability and Maintenance Properly designed and maintained dynamic and static cables are now extremely reliable. Alcatel, for example, claim a failure rate for all their cables as 0.18 faults per 100km per year. The major cause of faults is damage by accidental anchoring or fishing vessel clashes. Other hazards are damage during installation, icing, seabed clashes, and over-voltage. Most of the above can be mitigated by good design and adherence to construction and operating procedures. Increased reliability can be achieved by keeping cables buried in the seabed, dumping rocks over the cables where embedment is not possible and by inspection and monitoring at regular intervals. Static cable repairs would be attempted by replacement of the damaged section. Dynamic cable lengths would be replaced not repaired.
4.9.3 Generic Research and Development Needs The only generic research and development project identified as being potentially valuable for the wave energy industry as a whole is: • Development of a standardised, flexible connector. Currently cables and connectors used offshore are bespoke designs. Standardisation would help to reduce the currently very high prices of these elements. This type of connector would be valuable both for floating wind and wave devices as they move offshore. However, suitable connectors exist already and although expensive, can already be used for WEC prototype proving.
4.9.4 Conclusions and Recommendations The major conclusion of this sector is: • There is considerable potential for transfer of technology from experience of static and dynamic cables and subsea/ wet matable connectors in the offshore oil and gas industry. No technical barriers to prototype development exist but costs are still very high for cables and connectors. To reduce these costs study work is recommended to develop standardised, flexible connectors by revising existing specifications for Oil and Gas facilities.
Page 39 4.10 Control Systems
4.10.1 Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: • System control Optimisation of power take off and survival in extreme events are key features of any WEC. • Remote control and Because of the extreme or remote conditions at monitoring the WEC, it is often desirable to monitor or control it remotely. • System reliability The measurement and control systems need to be highly reliable and have minimal maintenance requirements.
4.10.2 Potential for Technology Transfer System Control The broad range of WECs under development have many different control inputs, outputs and system requirements. This means that system control is not really an area which lends itself to generic consideration. Once WEC systems have been developed and a control system is in place, it is recognised that improvements in efficiency can be realised by the optimisation of control strategies. To determine the best control strategy simulation and modelling will be required. The majority of control system companies have skills in developing advanced control algorithms and some have the facilities for basic simulation. There are also specialist simulation companies offering comprehensive simulation services but these tend to be expensive. Control strategies have primarily been developed by the wave energy device teams themselves and/or in universities. The use of proprietary systems offered by industry may offer the advantages of flexibility and faster reconfiguration times, since they use more highly developed, higher level configuration tools. These facilities, in combination with telemetry, may prove very useful during development stages. Remote control and monitoring WEC schemes need the ability to monitor the status and performance of the WEC and possibly remotely control some tuneable parameters. During development, the ability to experiment with different control schemes (strategies) and reconfigure or download software may be required. Proprietary systems to help do this already exist. The most obvious areas for technology transfer are in SCADA and communications systems. Communications technology has become cheaper and more widely used since there is a more established infrastructure. Satellite communications, for example, is much more commonplace. System reliability All WEC devices will need to be reliable and have minimal maintenance strategies. Control and Instrumentation systems employed in the petro-chemical industry (not just offshore oil/gas) have been developed to have high levels of availability. They achieve this by various designs, but self diagnostics and auto testing techniques are widely used to warn of critical failures before they happen.
Page 40 Equipment packaging and protection will also be important for improving reliability. Systems are available that can be fitted within enclosures which are sealed against the environment. These vary from weather protection to fully submersible systems. Subsea controls and measurement have developed most rapidly in recent years, although this technology is probably still too expensive to be directly useful.
4.10.3 Generic Research and Development Needs System Control The area which still needs research and development is the modelling and simulation of the proposed devices. This is so device specific that it is best done by WEC teams individually and is not an area for generic research. The issue of modelling and forecasting the wave input on a real time basis still needs to be addressed.
4.10.4 Conclusions and Recommendations The major conclusions of this sector are: • Great potential for transfer of technology in the key technology areas of system control, remote control and monitoring and system reliability from the offshore oil and gas and petro-chemical industry exists. The facility to remotely reconfigure a WEC control scheme will be particularly useful. • Device specific system response modelling should be carried out by individual device teams. Research into real time forecasting of detailed wave time behaviour is recommended.
4.10.5 References The Institute of Measurement and Control 87 Gower St, London, WC1E 6AF. http://www.instmc.org.uk/ The Instrumentation, Systems and http://www.isa.org/ Automation Society
Page 41 4.11 Power Quality and Grid Connection
4.11.1 Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: • Grid WEC teams have requested information on areas of demand, geography supply and connection points. They have also identified significant hurdles in the planning and approvals process. • Grid Connection to the grid requires standards of power quality to Connections be met. This impacts on the generator type, control, and energy storage requirements • Supplying Such problems have been encountered in connecting to the Isolated grid that the supply of isolated communities has been Communities perceived as a potentially more suitable proving ground for individual WEC prototypes. • Fault This concerns protecting the grid from faults on the device, Condition and protecting the device from faults in the grid Management
4.11.2 Potential for Technology Transfer National Grid Geography Technology transfer from the Grid companies and Wind Energy Industry on this issue can assist WEC teams greatly in the short term. There is, however, a clear mismatch between demand and supply in the areas where the wave energy resource is greatest. The inevitable result of this is inadequate distribution capacity in these areas. A further effect is the potential for reverse power in the distribution system which cannot be accepted without modifications, both technical and in operating procedures. There is a wider issue of infrastructure development here which is beyond the remit of this study but needs to be considered for the development of natural energy sources in general. No map has yet been published of the location of suitable grid connections for significant attachment of wave generated electricity to the public system. The Scottish Executive is currently looking to update their 1993 Renewable Energy Report which identified on a geographic basis across Scotland the network capacity to accept new sources of electricity generation. In addition, the problem is being investigated by the DTI working group on Network Issues. WEC teams have found the process of connecting to the grid to be expensive. However, grid companies have suggested that for the small sizes of generator (below 0.5 MW) currently under development there will be locations where a relatively low cost connection is achievable. Co-ordination between WEC teams and grid companies is recommended during scheme planning.
Page 42 Very high capital costs were quoted at the Technology Workshop for sufficient grid upgrades to permit the export of a significant quantity of wave generated electricity from the West Coast of Scotland to England. The only realistic driver for such upgrades is a real and substantial increase in the demand for renewable electricity in combination with the technology demonstrated at a prototype level. Currently, the attachment of prototypes is handled on a case by case basis. An assessment of the power quality which is acceptable to the grid Operator and the WEC Operator is established and a maximum power level agreed taking account of demand on the grid and the supply reliability. The wind industry has considerable experience of this problem and the potential for receiving advice from these other industries should be explored. The procedure is currently highly complicated and very dependent on the weakness of the grid in the most remote areas of the country. Efforts need to be made to streamline these discussions and it is recommended that one part of the grid be upgraded to readily accept these prototypes and to utilise the energy produced from them. It is recommended that the grid operators need, where possible, to promote the changes which facilitate the attachment of renewable energy devices to the grid. A study is recommended to identify the optimum location for testing of future prototypes. This will need to involve renewable energy teams and the grid operators. Supplying Isolated Communities The cost and complexity of grid connection has led to the suggestion that wave energy devices may, at least initially, be better suited to supplying isolated communities. Isolated communities are really only suitable for small scale deployment of prototypes as the local grid is usually dated, small and incapable of absorbing large amounts of power. However, as long as the power needs of the community are compatible with the prototype WEC device output, and back-up generation systems can be brought on stream during prototype testing, this may be a more fruitful course of action. A study is recommended to identify whether this is indeed the case and, if so, which communities would benefit or be interested in being involved. Fault Condition Management There exists a large amount of experience with the electrical utility regarding dealing with embedded generation related to the wind and hydro industries. No further study is therefore recommended.
4.11.3 Generic Research and Development Needs Grid Connections The issue of grid interfacing is common to all WEC schemes as well as other intermittent sources. Power quality was recognised as an issue. It was suggested that there is a technical limit to the proportion of conventional asynchronous generation that can be accepted by the system. There is a requirement for the grid operator to determine the capability of the local grid to accept such irregular generation. Alternative generator types may involve power conditioning at the point of generation. Power electronics systems for such conditioning are available and the adaptation to WEC use needs investigation. Energy storage is a generic issue for Renewables generators, although the demand for storage may be greater for wave energy than for other renewable sources. Storage
Page 43 may take numerous forms and work is at various stages of development. Recent publicity suggests that chemical storage is close to commercialisation whereas the development of a “hydrogen economy” is probably a long way off. An interesting footnote to the question of storage is that in circumstances that electricity is used wholly or partially for desalination, the issue of electricity storage falls away. Ongoing work into the development effective storage devices is therefore recommended. Fault Condition Management Some WEC teams have experienced high grid connection costs which are apparently driven by grid fault conditions. There is a need to investigate the potential for fault detection and effective intervention strategies in the grid. Study work is recommended to achieve this.
4.11.4 Conclusions and Recommendations The outstanding issues in this area are, in general, generic to the generation of electricity from intermittent sources of renewable energy and a function of the UK grid being least capable of accepting near sources of energy in its least robust sections without significant upgrading. The major conclusions of this sector are: • A grid map needs to be provided for the west coast of the UK so that potential WEC developers can identify the most suitable sites for future connection of devices. • A study of the grid capacity with a view to recommending areas for upgrading in the vicinity of the more suitable locations for WEC development is recommended. The study should involve WEC operators (who can provide input on wave climate and device characteristics) and grid operators (who can provide input on grid topology). This to be included in a study to identify the best places for establishing a centre for standardised proving of WECs. • Some generic areas for future R & D are recommended: 1. Testing and development of power conditioning modules for use in WEC systems is recommended. 2. Ongoing research into effective means of storing the energy during downtime is recommended. 3. Technology for the remote monitoring of faults should be studied and intervention strategies should be formulated.
Page 44 5. CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
5.1.1 The Wave Energy Industry is not co-ordinated All the WEC teams are relatively small. They are either university research departments or in two cases SMEs. Consequently, the speed of progress is slow towards development of first WEC prototypes and ultimately WEC power stations. It is apparent from the current study work that many disciplines are involved in the design and construction of a WEC prototype; it is not realistic for such small teams to cover the breadth of knowledge required. At present, all teams are working independently and commercial considerations force them to keep their ideas secret. This secrecy compounds the slow progress and delays any return on their good ideas.
5.1.2 Technology used in the Offshore and Other Industries can be transferred to the Wave Energy Industry. There are no major technological barriers to the deployment of a WEC prototype device. All of the operations of a WEC scheme (design, construction, transportation and installation, inspection, maintenance, repair and removal) have been developed in the offshore industry. Some WEC components still require refinement, but this is anticipated to be carried out during prototype development and is normally device specific. Significant opportunity for transfer of costing information and methods exists from the Offshore Oil and Gas, Onshore Civils and Manufacturing Industries. However, notice should be taken of the differences between wave energy devices and offshore installations within these cost estimates. Most offshore oil and gas projects are prototypes with a complete design process applied to each project. Wave energy projects are not considered viable if this approach is adopted here. The returns on investment are much lower. The wave energy industry should endeavour to select costs and technology gained in the offshore oil and gas industry, but, at the same time, to realise economies of scale and repeatability of design to keep costs down.
The study has identified those issues within each Key Technology Area faced by the Wave Energy Industry that have already been largely developed by the Offshore or other Industries. 5.1.3 There are areas where generic research and development would be useful Technology gaps were identified where generic research and development would be beneficial (see Key Technology Area in Section 4). In general, these would not prevent deployment of prototype devices. However, the majority of these issues should be addressed for the development of a WEC power station.
5.1.4 There is a lack of investor confidence in the industry Investment in Wave Energy is very small. The Wave Energy Industry received less support in the last ten years compared with other Renewable Energies. The device
Page 45 technology is perceived as being far from commercial realisation, carrying a high risk and having a long time scale on return for investors. To date, internationally, there have been no successful long term demonstration projects of the technology.
5.1.5 There are issues common to both the offshore wind and wave energy industries There are several areas in which the Offshore Wind Energy and Wave Energy Industries have common interests. Typical examples are planning approvals, subsea cabling, mooring systems, operating and maintenance strategies. Amongst these is the development of grid capacity to handle energy produced.
5.2 Recommendations The following actions are recommended to support the wave energy industry both in the UK and the rest of Europe. The recommendations are made bearing in mind the proposed programme of WEC prototype and power station development (Figure 5.1) and the perceived need for further cost reduction.
5.2.1 Promote co-ordination within the industry An immediate need exists for a co-ordinating body, similar to the Offshore Wind Energy Network (www.owen.eru.rl.ac.uk) or the British Wind Energy Association (www.bwea.com ). This should be responsible for setting up of an internet based information service (for example www.wavepower.org) to transfer contacts, knowledge and technology, to transmit technical and commercial data, provide a forum for the sharing of ideas and developments and to assist in design decisions for the development of WEC prototypes and power stations. This will require the input of all WEC teams, technologists, consultants, operators and suppliers. The following urgent study work to support the development of an internet based WEC information system needs to be undertaken and maintained on a regular basis: • References of previous technical work on Wave Energy to be compiled. This to include UK and international work on WEC and related technologies. • Costing Database and Industry Guidelines for Construction, Installation, Operation and Maintenance activities of future WECs, (also relevant to offshore wind). • Contacts List of interested parties; WEC design teams, operators, verification bodies, contractors, suppliers, technologists in WEC development or in related technologies. • Reliability Database References; sources of information for construction materials and equipment.
This activity could be linked in with the European Commission’s WAVENET project.
5.2.2 Transfer of Technology The following technology transfer studies are recommended to support WEC teams and to feed the proposed web site. Several issues were identified in Section 4 as having potential for technology transfer.
Page 46 Recommendations for WEC Prototype Deployment • Offshore Industry guidelines on the use of appropriate structural design codes and verification. • Offshore Industry guidelines for construction and marine operations planning. • Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial; i.e. BP Foinaven and Schiehallion. • Oil and Gas Operator’s Metocean data for identification of tow and installation weather windows. • Grid company information on the best locations to connect WECs to the electrical grid. • Offshore oil and gas industry inspection and monitoring procedures for remote facilities.
Recommendations for WEC Power Station Development • Use of synthetic ropes and taut moorings. • Proprietary systems to reconfigure or download different control schemes (strategies). • Self diagnostics and auto testing control schemes. • The use of proprietary systems to optimise control strategies. • SCADA and communications systems. 5.2.3 Implement generic research and development The following generic R & D studies are recommended to support WEC teams and to feed the proposed web site: • A study to identify the potential locations for a prototype test facility for connection to the electrical grid. Input will be required from WEC teams and grid companies. • A study to identify the capacity of the grid at specific locations identified above. • Investigation into the potential for fault detection and effective intervention strategies in grids. • Testing and development of power conditioning modules for use in WEC systems. • A series of mooring studies relevant to the different types of WECs. • Generic mooring detail studies; long term fatigue issues of lines and connection points, standard connector designs for the quick release and re-attachment of mooring systems and subsea cables. • A series of turbine trials undertaken in one facility to test the various turbines and their efficiency. • Enhanced modelling techniques for systems involving multiple devices. • Research into real time forecasting of detailed wave time behaviour. • Development of hydraulic systems based on water or other environmentally acceptable fluids. • A standardised, flexible electrical connector. • Research and development to continue to drive down the costs of cable and connector fabrication and cable laying. • Development of hydraulic machines (motors with low part load losses, high torque pumps). • Storage of energy.
Page 47 5.2.4 Build investor confidence by proving the technology Investment is required to enable WEC teams to demonstrate the technology as soon as reasonably practicable. Successful demonstration will generate future investor confidence and industrial support. Governments (both individual countries and European) and Industry (Wave, Offshore Oil and Gas companies and onshore Fabricators/ Manufacturers) need to combine together in a co-ordinated funding programme in support of the proving of WEC prototypes. The government needs to support the creation of an environment which encourages the increased co-operation and organisation between device teams. Once developed, WEC Prototypes need to be compared and proven in a standardised wave environment in order to attract investment. Prototype demonstration will also assist in making well-informed decisions on the development of Offshore WEC Power Stations. However, a decommissioned oil and gas facility could be appropriate as an offshore WEC prototype proving base; such as the shortly to be decommissioned Phillips Maureen Articulated Loading column (Figure 5.2).
5.2.5 The Offshore Wind and Wave Energy Industries should work together Efforts need to be made to identify generic efforts which would benefit both the offshore Wind Energy Industry and the Wave Energy Industry; e.g. subsea cabling, mooring systems, operating and maintenance strategies, grid connection. Combining funding programmes will lead to more efficient use of funds. There is potential to combine the power transmission from an offshore wind farm and a WEC. Multiple schemes could share a transmission cable, distributing the high overheads of cable laying amongst several parties. The Planning and Approvals process for at shore and near shore WEC schemes should benefit from the recent work carried out by the Wind Energy Industry. The approvals process for WECs requires clarification and a study, similar to the one carried out in Ireland should be commissioned. Official bodies who grant permission for the deployment of WECs should be encouraged to co-ordinate themselves now to streamline the planning approvals process. A study is required to assess the work required to upgrade the grid to handle large numbers of renewable energy devices. 5.2.6 Recommended Priorities The immediate priority of the Wave Energy Industry should be to direct government and industry resources towards successful deployment of successful prototypes. Devices closest to the market should be supported to achieve this goal. Industry co-ordination: immediate priorities An internet based information service should be established. Study work should be funded to support an internet based information service, containing: • References of previous technical work on Wave Energy. • Costing database and industry guidelines
Page 48 • Contacts List of interested parties. • Reliability database. Efforts should be made to align the Wave Energy Industry with the Wind Energy Industry as they move offshore. Prototype deployment: immediate priorities Technology transfer study work should be funded in the following areas: • Offshore Industry guidelines on the use of appropriate structural design codes and verification. • Offshore Industry guidelines for construction and marine operations. • Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial; i.e. BP Foinaven and Schiehallion. • Oil and Gas Operator’s Metocean data for identification of tow and installation weather windows. • Grid company information on the best locations to connect WECs to the electrical grid. • Offshore oil and gas industry inspection and monitoring procedures for remote facilities. Some generic research and development aimed at prototype deployment should be funded: • A study to identify the potential locations for a prototype test facility for connection to the electrical grid. Input will be required from WEC teams and grid companies. • A study to identify the capacity of the grid at specific locations identified above. Research and Development for the Longer Term In addition, during the next five years generic research and development activities described in the previous section should be supported to address the issues which will be faced when WEC power stations are deployed. Some of these issues will require long term effort; study work should therefore begin at the earliest opportunity if solutions are to be found which meet the target programme.
Page 49 6. FIGURES
Figure 3.1 WEC Type 1: Buoyant Moored Device Figure 3.2 WEC Type 2: Hinged Contour Device Figure 3.3 WEC Type 3: Oscillating Water Column Figure 3.4 Oscillating Water Column Chamber of LIMPET Figure 3.5 Pelamis 750kW device Figure 3.6 The Duck Figure 3.7 PS Frog Mark 4 Figure 3.8 Sperbuoy Figure 4.1 Favoured Wave Energy Locations Figure 4.2 Construction and Installation Options Figure 4.3 Concrete Offshore Platform Dry Dock Construction Figure 4.4 Installation and Deballasting of Subsea Oil Tank Figure 4.5 Subsea Remote Operating Vehicle (ROV) Figure 4.6 The Wells Turbine Figure 4.7 Troll Static Cable Figure 4.8 Asgard Dynamic Cable Figure 4.9 Asgard Dynamic Cable Arrangement Figure 5.1 Potential Programme for Development of Wave Energy Schemes Figure 5.2 Offshore Prototype Testing and Proving Facility
Page 50 Figure 3.1 WEC Type 1: Buoyant Moored Device
Page 51 Figure 3.2 WEC Type 2: Hinged Contour Device
Page 52 Figure 3.3 WEC Type 3: Oscillating Water Column
Page 53 Figure 3.4 Oscillating Water Column Chamber of LIMPET
Figure 3.5 Pelamis 750kW device
Page 54 Figure 3.6 The Duck
Figure 3.8 Sperbuoy
Page 55 ftr.w.
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Ey w nrt Atfnmjt r +c tinctia-k-J taiu >■ l ie-'-u-h -yihb-5 ?fncdpciT.-j'- ?,it Ei .| aii.1 v.i. .1 ru-iiirajqlid'.'. ’a-li^L a- AZ hhV rr llj LCIC +.11 ITUll LT I'C-OCKCI TTrl r^Hl * lY-HlH- Y i:r 5. 1:|l|-vb:ll. - ^ dlHfltl Figure 4.1 Favoured Wave Energy Locations Page 56 '•rm-* • zc Figure 4.2 Construction and Installation Options Page 57 Figure Figure V- 4.4 4.3 Installation Concrete Offshore and Deballasting Platform Page Dry of 58 Subsea Dock Construction Oil Tank Figure 4.5 Subsea Remote Operating Vehicle (ROY) (photo by Sonsub) Figure 4.6 The Wells Turbine (photo by Wavegen) Page 59 Figure 4.9 Asgard Dynamic Cable Arrangement Page 60 At shore WEC prototype test Off shore WEC prototype test At shore power station development Off shore power station development Figure 5.1 Potential Programme for Development of Wave Energy Schemes Page 61 Figure 5.2 Offshore Prototype Testing and Proving Facility Page 62 7. ACKNOWLEDGEMENTS Thanks to all participants at the Technology Workshop and to all those Individuals, Research Teams and Companies who donated time, effort and material towards the successful completion of this project. Page 63 Appendix A WEC Contacts Database Page A1 A1. WEC TEAMS A2. INDUSTRY CONTACT Page A2 APPENDIX A - WEC CONTACTS DATABASE A1. - WEC TEAMS Scheme Location Description Status Contact Shoreline OWC Pico Azores Azores, Lisbon uni OWC in concrete box, Wells Turb. Prototype Prof. Antonio Falcao Limpet - Islay Islay OWC in concrete box, Wells Turb. Operational Allan Thompson Prof. Trevor Whittaker Dr. Bill Beattie Energetech, Port Kembla, OWC with parabolic reflection, impulse Under Dr. Tom Dennis Australia Australia NSW turb construction TAPCHAN Bergen, Norway Tapered channel lifts water above MSL Decomissione Prof. Johannes d Falnes Pendulator Japan Hinged at top (easy access) or bottom Prototype Tomjii Watabe (more efficient) OWC India India, Madras OWC with Wells Turb later changed to Prototype M Ravidran Impulse Turb OWC Norway Trondheim, Norway OWC on shoreline Decomissione Prof. Johannes d Falnes Japan OWC Sakata, Japan OWC Prototype Shiegeo Takahashi Near shore FWPV vessel Sweden + UK contact floating TAPCHAN Model tests Fredrik Sandberg Wave dragon Danish floating TAPCHAN with parabola Model tests Page A1 OSPREY Scotland floating OWC Decomissione Allan Thompson d Mighty Whale Japan Floating OWC Prototype Salter's duck Edinburgh, Scotland line of cam shaped devices, hydraulic Prototype Prof. Stephen take off Salter Danish piston Denmark float/ piston/ submersible turb Model tests Kim Nielsen Wave Plane Denmark floating TAPCHAN, swirling turbine intake Prototype Erik Skaarup Sper buoy Plymouth uni, UK multiple OWC for different wave Prototype Fraser Johnson frequency Offshore Pelamis Scotland, Edinburgh Seasnake, hydraulic take off, novel Model tests Richard Yemm anchorage OPT buoy USA submersed moored buoy + ? Prototype Gordon Taylor McCabe Wave Ireland 2xpontoons + hydraulic take off Prototype Peter McCabe Pump Archimedes Wave Netherlands vertical float motion drives hydraulic pumpPrototype Hans van Breugel Swing PS Frog Lancaster uni table tennis bat, weight moves back and Scheme Prof. Michael forth French Inter Project, Sweden large water ram, few details Scheme Gunnar Fredrikson Sweden Techocean Sweden volume change of anchored hose drives Scheme Gunnar Fredrikson hosepump air turb. OMI Pump California, USA multiple floats below offshore platform Scheme Michael Houser Swedish IPS Edinburgh float and piston Scheme Prof. Stephen Salter Wave bob Ireland relative motion between submerged and Model tests William Dick surface float OWEC USA circular floats and springs Scheme Foerd Ames Page A2 APPENDIX A - WEC CONTACTS DATABASE A2. - INDUSTRY CONTACTS Company Contact Description Preliminaryworkshop invitees WD Loth Bill Loth Underwater Control Systems Rexroth Ian Chase Hydraulic systems BHR Group Bob Flitney Hydraulic systems ABB John Wilkins Offshore control systems Alcatel Norge Gunnar Evensett Subsea cables Scottish & Southern Ian Tait Electrical grid Lloyds Bob Boon Design Verification Noble Denton John Ridehalgh Marine Consultants HSE Dr. Don Smith Safety regulator Shell Terry Rhodes Offshore operator Conoco Rick Jefferys Offshore operator BP Paul Rutter Offshore operator Econnect Nigel Scott Electrical consultant ETSU Tom Thorpe Government agency WS Atkins Rod Rainey Engineering consultancy Marine Foreshight Panel John Griffiths Tecnomare SpA Ing. Gnone Engineering consultancy, subsea vehicle design, trenching, accoustic control systems, inspection systems Ramboll Kim Nielsen Engineering consultancy Offshore Contractors Norman Thompson Offshore construction Association Garrad Hassan Tim Camp Wind Energy Consultants Page A3 Mooring BPP M H Patel Mooring systems Balmoral Marine Ltd Dr Robert Oram Mooring systems Lloyds Beal Ltd J. Topalian Mooring supplier SBM J. Pollack Mooring systems Bluewater Graham Gray FPSO mooring Hydraulics Helipebs J. Anderton Hydraulic systems Sonsub Keith McGregor ROVs Hydraudyne Theo Werners Hydraulic engineering Artemis Hydraulic systems Subsea cabling Pirelli A Holm Cables JDR Cables Michael Grimm Cables Duco Tony Hanson Cables Tronic Mark Jones Subsea connectors Control Kongsberg Simrad D. Shand Subsea control Siemens Peter Gilks Electrical equipment Fisher Travis Hesketh Control equipment Foxboro Bill Hunt Control equipment ABB Instrumentation Tony Bundock Process instrumentation ABB Automation John Wilkins Control & electrical equipment Fantoft Jonathan Teuten Process Simulation Silvertech Andy Cooper Control & Safety System designers IEE Prof. Herbert Scottish institution Wittington Centre for Renewable Allison Whilte Researchers Energy Systems Page A4 Design, Ops and Maintenance Exxon Mobil V. G. Lee Offshore operator Elf Exploration Elgin Franklin Offshore operator Phillips Petroleum Peter Broughton Offshore operator Texaco York LeCorgne Offshore operator Wood Group Fraser Morrison Maintenance DnV Iain Light Certification RINA Institution IMarE Institution National Engineering Ray Hunter Research Laboratory Marine Operations Rockwater Subsea contractors Smit Martin Pope Offshore vessels Van Oord ACZ P. Van Oord Offshore vessels Construction Fluor Daniel R. Gallagher Civil Contractors Laing Civil Contractors Kier J. Dodds Civil Contractors Kvaerner David Riddet Civil Contractors Cammell Laird group Tom Benson Shipbuilders Harland and Wolff F. Black Shipbuilders Swan Hunter J Veldhuizen Shipbuilders A&P Group Clive Towl Shipbuilders Institution of Civil Engineers Andrew Tillbrook Institution Pneumatics Wavegen Allan Wells Turbine Inventor Generation AUR Hydropower RP Scott Micro-hydro generation Newage International Paul Radford Generator manufacturer Page A5 TXU Europe Power Paul Henry Energy consultant PB Power Andrew Pringle Energy consultant Scottish Power Alan Mortimer Utility ESB Utility Materials Corus Steel/Aluminium Avesta Sheffield Geoff Thompson Stainless steel British Cement Association Mike Webster Concrete promoter Steel Construction Institute Tony Biddle Steel promoter Page A6 Page A1 Appendix B Technology Workshop Key Issues Slides GENERIC TECHNOLOGY DEVELOPMENT OF WAVE ENERGY DEVICES - WORKSHOP Organised by Arup Energy, London 15 September 2000 PageBl WORKSHOP AGENDA Welcome (10.00am) Objectives Workshop Planning Wave Device Classification Technology Session 1 (10.15am to Lunch) Chair: David Collier (Arup Energy) Technology Session 2 (2.00pm to 4.45pm) Chair: Dr. Tony Lewis (UCC) Summing Up Close (5.00pm) WORKSHOP OBJECTIVES Identify Technology Requirements to Develop Wave Power Industry Identify Current Potential for Transfer of Technology from other Industries especially Offshore Oil & Gas Identify R & D Priorities and propose Future Funding Strategy Chair: David Collier WORKSHOP TECHNOLOGY AREAS Regulatory Environment, HSE, Design & Certification Construction Methods, Cost Estimating Installation & Mooring Systems Offshore Operations, Maintenance & Materials Hydraulic & Pneumatic Systems I Subsea Cables & Connectors Controls Systems Power Quality & Grid Connection WORKSHOP FORMAT LaJ Facilitators to introduce Key Issues Presenters to Respond Open Discussion (Minuted) Participants to complete Questionnaire (for Return) and propose new issues Chair to close discussion WORKSHOP RULES LaJ Keep comments positive & brief No design No selling Use generic device names Write any comments not stated on the questionnaire WAVE DEVICE CLASSIFICATION Tethered Buoyant Hinged Wave Contour Oscillating Water Column At shore Near shore (approx. lOmiles) Offshore PageB7 Session 1: Design, Construction, Installation & Maintenance Chair: David Collier Arup Energy 10.15am Regulatory Environment & HSE Issues What Regulations will apply? Will Energy Making Devices be treated the same as Offshore Oil & Gas Installations? Planning Approvals/ Licensing Route Prototypes and Energy Making Devices - Any Differences? Parallels? Offshore Wind, etc. Facilitator: Alan Macleay Design Codes & Certification Issues Which Codes apply? DnV, HSE, API, BS? etc. Certification and Underwriting Process Present Data Gaps; coastal wave environment database, wave shapes, wave loading, etc. Facilitator: Alan Macleay PageBlO Construction Methods/ Cost Estimation Issues Mow ao you estimate accurately? Selecting the right Location and Method of Construction Offshore/ Civil Methods Installation Methods Manufacturing Methods Prototype versus Production Costs Life Cycle Costing Facilitator: Phil Bramhall PageBll Installation Issues Metocean Criteria Floatout/ Towout Installation Options; Self-installing, Marine Equipment Ease of Removal Risk & Safety Assessments Facilitator: Gordon Jackson PageB12 Mooring Systems Issues Conventional Options - Chain, Wire & Anchor? Recent Developments Taut Moorings Synthetic Fibre Ropes Transfer of Technology FPSOs Tanker Offloading Dynamic Positioning Quick Release/ Re-attachment Reliability, Maintainability Deployment/ Retrieval Facilitator: Gordon Jackson PageBU Offshore Operations & Maintenance Issues How to Keep Operational Costs Down? How to achieve Zero/ Low Maintenance Strategy? Major Refit Strategy; Return to shore & Replace? Facilitator: Richard Kollek PageBM Materials Issues Corrosion Strategy Balance between low cost and high performance materials? Life Cycle Analysis Facilitator: Simon Cardwell Session 2: Power Generation & Transmission Chair: Dr. Tony Lewis University College Cork 2.00pm: Introduction Hydraulic System Issues Long Term Performance, Reliability & Maintainability? Hydraulic Fluid Containment against spillage. Hydraulic Motors & Rectification? Remote Hydraulic Power Transmission Response to Extreme Environmental Events? Facilitator: Robert Hyde PageBl? Pneumatic System Issues Wells Turbine Development? Other Pneumatic Systems; Impulse Turbine Development? Reliability and Maintainability? Wind Turbine Transfer of Technology Facilitator: Robert Hyde PageBIS Subsea Cables & Connectors Issues Transfer of Technology; Subsea Oil and Gas, Wind Power Industries? How to install at Low Cost? Balance between high reliability and low cost? Use with Flexible Mooring Systems? Reliability and Maintainability? Limitations for Cable Laying? Facilitator: Alan Macleay PageBlP Controls Systems Issues Measurement & control to optimise power take-off? Measurement & control in extreme sea- states - equipment protection? System modelling, simulation & advanced control Remote control/monitoring - SCADA/comms? Suitable 'packaging' for the environment? Technology Transfer; robust packaging, high reliability, subsea technology, comms? Control of Power Generation Facilitator: Peter Horsley Power Quality & Grid Connection Issues Mismatch of Demand & Supply? Location of Grid Connections? Power Quality? Generator Type & Control Energy Storage Requirements Grid or Isolated Communities? Fault Condition Management? Technology Transfer - Wind Market? Planning Approvals Route? Facilitator: Robert Hyde Page B21 Summing Up by: David Collier, Arup Energy 4.45pm Reminder: ETSU Wave Energy Workshop James Watt Conference Centre, East Kilbride 24 October 2000 for details see Dti Website: www.dti.gov.uk/renewable/wave.htm Appendix C WEC Team Questionnaire Responses Wavegen Alan Thompson Tom Heath (15/08/00) - Minutes by David Scarr Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment For next scheme they are concentrating offshore. They think it must be retrieved and returned to shore once a year (say) for maintenance. Maintenance cannot be carried out offshore because of the waves around the device. Rapid attach/details moorings or anchors are therefore of interest. Schemes that currently exist in the offshore industry are prohibitively expensive. Associated with anchoring are geology/topography/SI surveys which are expensive too. They have a small scheme for tension and catenary moored buoys. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Their next scheme will probably use hydraulic power take off. They are very keen on this area. Interested in pumping fluid ashore rather than using a power cable. Interested in overlap from Raw Water Injection and would like to talk to people working on sub sea pumping. Interested to use hydraulic storage to store energy long term (i.e. to cover periods of low wave activity). Pneumatic power generation systems Wells operates @ p = 1 bar max p = 7 kPa average They do not intend to develop the Wells turbine further. Theirs operates at a peak efficiency of 80% maximum (although usually it is 55 - 60%). They believe a variable pitch device could perhaps improve 80 up to 90%. But this will take time. They used to be a partner in the Salter Turbine but thought the project too long term. They believe simplicity is important for reliable operation and variable pitch is too complex. Offshore environment is not good for Wells. Current device has large inertia wheel to smooth power to grid. A more robust grid would use a smaller wheel. Azores turbine was damaged before installation therefore vibrations probably not a big problem. Construction and Installation methods OWC Construction Did not lift in Limpet because of; need for large crane, didn’t know how to tie into wall, short weather window for lift, Consultant (KMM) required more wave data. See future in incorporation into breakwater. 30yr life, used AQWA for design. They have problems assessing construction costs abroad. Installation offshore. Upset by huge marine costs. See future as small devices which can be towed and installed by harbour tugs. Subsea power connection, power take off, flexible cables Seem confident that the technology for this exists, their only concern is the expense (especially the connections). AMcL tells them there is 40km of cable in Aberdeen from a decommissioned platform which is available. Wave energy conversion devices and control systems Have considered seabed transducer like Energetech, but believe it is a research project for QUB, not a business move right now. They have a lot of data for control but have yet to work through it all and carry out tests. They will collect data on everything at limpet and examine it (turbine speed, wave heights, damping, valves, air P, vibration, power out). They can control torque resistance, power factor inverters, valve position (1.5 secs total close). Aim to match turbine damping with input to maximise power out-perhaps. They have written their own software in C to develop algorithms and use Metertechnique a Danish supplier. Yes have dead start procedure and auto cut if too much power. Power Quality - Connection to the grid Spec. for connection to the grid is tough, tight +f limits on Voltage and Frequency. To meet it they have a short term (20s) control algorithm and a fly wheel and smoothing circuits. They need more information on grid; where is the demand, where is the supply, is wind taking all the available capacity. Many wave sites require large grid investment just to be connected - wave schemes can’t find this. How does this compare with abroad? Should waves be connected to the grid? They think not. Offshore is AC or DC best? Power storage comes up a lot. They think a method of day this is very important. Gasometer? Diaphragm? Danish Piston? Development of Design, Operation and Maintenance codes for certification and due diligence Insurance is a concern because of high premiums. Maybe tough for under-writers to see the schemes meeting any existing design codes. Insurers have asked for a whole series of checks to be carried out which lengthens design. Answer requires device to be inspected every 6 months which is expensive for offshore. Department Energy HSE regs are a problem. Their device is classed as a rig when they feel something like a fish farm is more appropriate. Design codes don’t acknowledge wave devices absorb a lot of the loads therefore don’t need to resist them? They used offshore oil and gas codes (IMUR) for Ospery and loads from 1st principals. Long term corrosion resistance materials Didn’t talk a lot about this but they are very, keen especially regarding their new device. Suggest extended to erosion resistant materials. They’d like a database of design lives/time to failure of components. Others They are concentrating offshore because; more space free from environment problems, more energy. Floating rather than bottom mounted because of installation risk and cost and they think a low profile avoids big wave loads. Recognise the problem is the greater distance from the market. Would like a test site established for use by all teams. Site establishment costs (surveys etc), power line and grid connection costs are all large 1 offs which could be avoided. Design info, wave regimes like TL database would be good. Many problems with ETSU. Requirements for private funds matching the grant. Requirements for partners Conflict of interest between business (short term project) and academic (long term). Slow response time by DTI (1yr). Wavegen are privately funded (funding venture capital shareholder funding). More successful with EU funds although exchange rate is poor right now. They have patents on some aspects of Limpet geometry. How about DTI funding patent applications? Ocean Power Delivery Richard Yemm (15/08/00) - Minutes by David Scarr Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment Currently Pelamis weather vanes by *90° - later may use active moorings. Subsea connection is simple concrete block - easy. Connection to device has a fretting problem which requires work. Interested in data for mooring lines (especially long term corrosion). Permissible detach/attach time can be several hours. Perhaps parallels with flare buoys? Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Hydraulic system can potentially achieve 70-75% efficiency. Has considered using seawater/fresh water/biodegradable oils but this is a future idea only. Hydraulics supplier (Helipebs) is keen to stress reliability. Oil flow is smoothed by accumulators. Energy dissipation via heat exchs. is required. Accumulator ^ motor ^ generator. Modular power packs (Deity) are very reliable. Maintenance seals need to be good, long term priority. Contaminant technology in low permeability bladders exists. Pneumatic power generation systems Max. Wells T. efficiency = 50%, lower than hydraulics. Not applicable to this scheme. Construction and Installation methods Philosophy is existing technology, short development time, non-site specific, test before development (waves scale well), must not use prototype components in a prototype device, mooring pre-laid, device constructed on-shore. Device will be towed initially (near shore site), in future hopes to off load from a ship. Compare with pipe laying. Core team doesn’t know how much about structural design (WS Atkins are helping), but knows it can be done. Also, need more data on costs to assist in design decisions. Would like to know what permits are required and timescale for process. Subsea power connection, power take off, flexible cables Single umbilical to seabed. Believes technology exists for this - if it doesn’t offshore wind will solve the problems. Interested in redundancy / reliability required. Must they be designed to be retrieved for fixing? Prototype will not generate power so not an immediate issue. Although connections are expensive now, mass production of a specific design will drop costs. Duco giving him cable advice. Tronic re connectors. Wave energy conversion devices and control systems Very device specific therefore hard to do generic research. Inputs: power out, position, oil pressure and temperature. Outputs: damping. Very important and a major strength. Damping of hydraulic rams is controlled to time device to sea state. For survival condition too. Lots of f domain modelling, T domain ongoing. For prototype lots of data will be collected (this has not been done by other schemes). Applied to DTI grant for this. Data acquisition must by Garrad Hassan? AmcL questioned reliability. Many problems with subsea controls - RY is keen on any data on this. Prototype data to be UHF link to shore. Future fibreoptic / acoustic. System must be tested thoroughly before full deployment. Control system adjusts damping to eliminate voltage stutter. Power Quality - Connection to the grid Doesn’t see a problem here. Device must latch to store power short term. Thinks ABB’s DC system (like wind power) is good. Find connection costs are related to upgrades required to handle fault conditions. These are high. Contracts do no consider possibility of the device ‘constrained off’. Would like to introduce this (Yorkshire electric and Denmark). Trading uses 6 hourly plots. Waves are very easy to predict of wind. Interested in having more wave data, especially for the atlantic. Development of Design, Operation and Maintenance codes for certification and due diligence Design codes are difficult since devices we all different and are at an early development state. Feels it would constrain design too much. However, did like the DnV first ship code. Maintenance to be minimised. Autonomous operation, 15yr service life and 100% decomissionable. Lots of redundancy in unit - survivability. For problems simply replace power unit module. Loss of 1 unit not fatal. Hose and seal life main issue (7yrs). Design packages don’t consider power absorption. Certification could be done at standard test site. Insurance - hasn’t tried but will go for minimum cover possible. Interested to know what is minimum required. Patents on parts of scheme. Long term corrosion resistance materials Prototype and early units are steel, for ease. Considers concrete long term, if construction method and point load problem can be sorted out. Otherwise considers this a future a problem. Plastic bearings? Interested in corrosion allowances required. Edinburgh University Stephen Salter Wave Power Study 2000 This note follows the list of topics given in an attachment to an e-mail from David Scarr dated 10 August 2000. Existing wave power technology. Wave energy devices studied at Edinburgh have been • Asymmetrical oscillating water-columns. • A series of floats and flaps which evolved into the long spine-based close-packed Duck system. This was intended to maximise the use of sea space and needed the invention and development of many new types of bearing, hydraulic machine and seal. Although estimates of its generation costs have been attractive, the crest-spanning requirement has to involve installations of several tens of megawatts and so its deployment is far in the future. The design has triggered ideas for several novel hydraulic power conversion techniques which are finding application in other fields such as wind, tidal-stream and vehicle transmission. The tank-testing programme provided information on bending-moments and mooring forces on compliant spines as a function of length and stiffness in directional seas. • A solo Duck with active heave and surge axes. This turned out to be very productive in wide tank tests but an unpowered model tethered with tension legs showed unacceptably high snatch loads after any of the lines went slack. • A solo, bottom-hinged device known as the Mace designed explicitly for testing big ring-cam pumps at sea. It has a flat but rather low efficiency band and, thanks to the sudden onset of vortex losses at excursions of 12 meters, excellent extreme wave survival features. A single Mace could be a useful research base. A pair of Maces could simulate the properties of a long spine to allow tests of very short lengths of Duck string with as few as four Ducks. • A solo, sloped buoy using the Swedish IPS stroke-limitation method designed for mobility and free-range testing of hydraulics. Tests on a fixed slide show that slope movement gives a very much higher and wider efficiency band than the conventional vertical heaving one. Its hydrodynamics should be similar to but more linear than a solo Duck. We are now starting work with a free floating version using an internal dynamometer. The Edinburgh philosophy is for hard-skinned, asymmetric devices with good wave-making capability which are inherently resonant at the useful parts of the spectrum without the need for large amounts of reactive loading. We want short stress paths with no stress hot spots and means to remove all stresses higher than those which occur at the economic power limit. We want continuous, intelligent control of the power conversion forces, access to energy storage and synchronous phase-locked generation. It seems that these are best provided by high- pressure oil. We favour free-floating deep-water systems with very compliant attachments to any sea-bed geology. We like things that can be built in a shipyard rather than needing on-site construction. The hydraulic machines planned for Ducks all use digital control of poppet valves to give variable displacement. Big, slow ring-cam pumps can have torques up to 108 Newton metres or more. Fast multi-bank motors can combine oil flows from several variable sources to drive a single shaft at generator speeds at power ratings up to 10 megawatts. The selectable poppet valve technology means that oil is never pressurised unless it is going to be used for useful work. This makes the part-load efficiency much higher than for conventional machines with swash plate or bent-axis control of displacement. Low power units are now being developed by a spin-off company, Artemis Intelligent Power Ltd. Larger ones could be used in wind and tidal-stream plant and also in many land-based power control duties. The design calculations suggest that performance gets better as size increases. We believe that upstream energy storage is a crucial requirement for renewable energy inputs to slender grids. Suitable stores can be interfaced with hydraulics. Poppet valve hydraulics can also provide a convenient replacement for the loaded moving parts of the clean, quiet and potentially very efficient Stirling Engine. This could allow thermal energy storage and also fuel burning renewable generators. Work on vertical axis tidal-stream generators has led to a self-embedding anchor with good weight-to-holding ratio for soft sea beds and a post-tensioned pile for rock. Wave energy research in the seventies triggered the design of new types of wave maker which could absorb reflections and make accurate and repeatable multi-directional sea states. These techniques are now being used in many test tanks. Our original wide tank may have to be demolished and we are designing a replacement which would combine waves and currents with control over 360 degrees. General areas where research and development are needed. Historic information recovery The test results from device teams and some of the reports from the technical advisory groups from the early days of wave energy would be a valuable education to new wave inventors and even to new programme controllers. Unfortunately most of the information is not available in electronic form. The conversion of a selection of the most useful material to a publicly accessible electronic form, perhapswith additional notes written with hindsight, would be a useful activity and would recover some of the value of the money spent. Computer models Numerical predictions of the behaviour of wave devices in the linear wave regime have got much cheaper, quicker and better. We should make suitable software and also well-tabulated previous results available to the entire wave community. We should extend software capability to handle thin-edged plates, power-conversion hardware and, if possible, non-linear behaviour in currents and large waves. Numerical modellers still strongly support tank testing. It confirms their more surprising predictions. So far it is the only way to handle non-linear conditions. There have been several examples of a simulation problem which was though to be too difficult being quickly solved after the sight of a model in a tank. If possible, the computer people should work alongside the tank testers. Parametric costs The optimisation of a wave energy device requires the careful combination of wave climate data and tank results with the costs of maintenance and construction. The latter may be very difficult to obtain. Commercial groups who are tendering for contracts would fire any engineer who released cost information or ideas on how costs could be reduced. Some of the information used in the first UK wave energy programme was ludicrous. For example the cost estimates for parts of anchors were higher per tonne than those for high precision machine tools. The sources must not come from consultants who live on a percentage of the contract cost but from constructors who live on the difference between the estimate and the actual cost. Extending the power rating of fast hydraulic machines. There are existing fast hydraulic motors with power ratings up to a megawatt which could be used to drive the generators of early prototype wave plant. Their part load efficiency is not good and they can take oil from only one source. These two problems are being tackled by Artemis Intelligent Power. Ten electronically controlled pumps have been made. A combined pump-motor system is being built for tests in a vehicle transmission and a double-bank pump unit is in service in a demining application. However the sizes are still rather small, less than 20 kW. In theory the technical problems should reduce with increasing size because clearances become larger in proportion to the size of dirt in the oil. There should be a series of machines, built with increasing power in steps of about two, aimed at applications in heavy goods vehicle and locomotive transmissions. Cheaper gas accumulators The present cost of gas accumulators for energy storage is far too high to be used for wave energy. The cost is hard to understand unless it has been driven up by safety requirements, some of which may not be applicable to underwater plant. It may be possible to make large reductions by building tubular nitrogen bladders into high-pressure oil pipes. Geometrically tolerant, hydrostatic bearings running on sea water. Hydrostatic bearing technology could offer the very high loads and long life needed for some wave power devices but would usually demand much tighter clearances than allowed by highly stressed frames of wave devices especially if the bearing are fed with fluids of the viscosity of sea water. Work on the bearings for the variable-pitch tidal stream rotor could be extended to waves. Direct electrical conversion. In the early seventies we tried to design direct electrical conversion for Ducks with advice from Professor Eric Laithwaite. We concluded that even if we could afford all the iron and copper, the weight would sink them. There have since been large improvements both in permanent magnet technology and in the semiconductors used for changing frequency, so our initial conclusion may now be wrong. Marcus Mueller at Durham is trying to do a direct electro-magnetic conversion for Ducks. The key figure will be the estimate for torque per kilogram. The mechanical problems will be maintaining fine air gaps despite geometrical distortion under load and resisting the large attraction forces between poles. If these problems can be solved then the possibilities are very exciting. Direct electro-magnetic technology is better for rotary devices than for linear ones because all the bits can be active all the time. A reciprocating flow wind tunnel. The most popular medium for power conversion in wave energy is low-pressure air because of the ease with which speeds high enough for electrical generators are achieved. This enthusiasm has not been shared by the Edinburgh group because of the narrow range of air velocities which give reasonable efficiency. Our prejudice has not been changed by involvement with the design and manufacture of a variable-pitch turbine for the Azores. However, if we are wrong, and low- pressure air has a future then it will be much cheaper and quicker to develop the turbines with a reciprocating-flow wind-tunnel rather than with wave-driven air. This will give instant safe shut down, exact calibration and operation regardless of weather conditions. It should have a power rating of about 500 kW. It could also be used for gust research for wind energy. We can show an outline design with energy recovery driven, inevitably, by high-pressure oil. Internal flows in oscillating water columns The water chamber of an oscillating water column can have a very complicated set of resonances and the viscous damping of full size ones may be smaller in proportion than models. Large amounts of internal sloshing will increase the probability of water getting into air turbines. The problem could be studied at model scale by building an oscillating water column containing a cylindrical body driven in up to three axes by a control system with negative damping so that sloshing modes can be deliberately induced. The pattern of the modes and the size of the negative damping coefficient will reveal what happens and how close we are to danger. The effects of detuning devices such as internal webs can be compared. Anti-erosion cladding for air turbine blades. The tip speeds needed to obtain sufficiently high damping coefficients for oscillating water columns are in the region where some materials will suffer erosion from any water droplets entrained in the airflow. This problem may be particularly serious for the blades of variable-pitch machines if they are made from carbon-fibre composites. It would be useful to know how to apply claddings from materials like nickel directly to carbon. Our tests suggest that erosion seems to be made worse if droplets hit material which has been taken past its yield point. This may be because yielding opens up micro crevices and the impact pressure can act along the full depth of the crevice. A crevice-free deposit of electroless nickel may be a good solution. Super-plastic forming/diffusion bonding of titanium for turbine blades Work from the JOULE programme on variable-pitch turbines suggested that titanium had very attractive properties for blades but that its tooling costs could not be justified for a single machine. If larger number of machines are made this would have to reconsidered Grid interactions and embedded generation If a malevolent engineer had deliberately tried to design the transmission and distribution network of the UK to be as hostile to wave energy as possible, the result would be close to what exists now. Even if renewable energy sources can produce steady, phase-locked electricity there may still be problems about injecting it into parts of a network which has evolved for a different pattern of generation. I am sure that the problems of power factor and voltage regulation are all soluble but we want to have a very clear understanding of what they are and what modifications to the tap settings of distribution transformers are needed. Long range power transmission Iceland has enormous reserves of both geothermal and hydro electricity which are far more than it could ever use. Both are easily regulated and both may benefit from idle periods for recovery. There have been plans to build an electrical link from Iceland to Europe. If deep water wave devices could feed power into this link and if the Icelandic generators were used to supply shortfalls during the absence of waves, then Europe could eventually build up a firm source of 2 to 300 GW with 600 TWh a year coming from waves. The scheme would benefit from an extended period of steady state construction. Duck-specific areas where research and development are needed. Despite the several closures of the UK wave programme, work has continued on many of the critical items of Duck hardware by seeking small-scale, land-based applications for some of the ideas. The biggest remaining problem is the manufacture of a large face seal to enclose the ring cam using the Dutch ‘Ceramax ’ coating which has now been shown to have long term survival in sea water. We would prefer to apply high pressure ring-cam technology initially to power conversion in wind or tidal-stream plant, both of which offer good accessibility, before using it for wave energy. Large ring-cams will have to be made on a special machine tool which would use spherical rather than linear geometry. Even very large cams can be made on compact machines by exploitation of the Peaucellier straight-line motion modified to generate large radii. The design of each sub assembly of a ring cam machine must be proved with test rigs in the laboratory. We believe that there are still improvements to be made in the control of Ducks using the technique of complex-conjugate control studied by Paul Nebel. This will involve the co-operative working of the Duck power conversion and the spine joints. The Duck-to-spine magnetic squeeze-film bearing has to work in sea water, take loads of several thousand of tonnes with poor alignment and no rubbing or frictional losses. It has been the subject of a PhD thesis by Colin Anderson and the operating principle has been proven in the laboratory on a small unit. This was a 1.2 metre diameter circular thrust bearing that could support the weight of an adult for over sixty seconds. There is still work to be done on the axial location of the magnets and the full scale assembly method. This would benefit from advice of the heavy construction industry. The present Duck spine is made from a series of short concrete ‘cups’ post-tensioned together between end-caps to give a series of separate compartments which could survive a leak into two adjacent compartments. Later stages in the assembly involve rotating a floating spine between centres, like a work-piece on a very large lathe. I am sure that this too could be improved by advice from the construction industry. While post-tensioned concrete is exactly right for the Duck spines it is too strong for the Duck bodies. It is also too heavy so that the Duck has to be built with a series of sealed inner compartments which involve expensive shuttering. It would be better if Ducks could be cast solid with a material which averages the strength and density properties of concrete and expanded polystyrene. (One such is a mixture of ice and wood pulp). Its is possible to make foam-concrete with the right properties but it shows an undesirable long-term porosity. We believe that wave energy would benefit from new materials based perhaps on mixtures of air, concrete and carbon fibre. We have already made sprayed polyurethane rolling seals at 1.2 metres diameter, larger than needed for the Duck joint rams. However the production process should be improved and worries about the creep of polyurethane addressed. An effective method for reducing the motion of Ducks for maintenance has been tested in a narrow tank. A signal proportional to Duck angular velocity was fed into the adjacent heave joints. The Duck pitch angle could be reduced to less than 2 degrees in sea states up to 2.5 metres significant wave height. According to a maintenance model developed by Roy Taylor, this figure is particularly important for access for maintenance. The pitch cancellation technique would have to be confirmed with free-floating spine models. Reliability analysis by Whickam and Thorpe showed that it would be necessary for Ducks to have ‘jump leads ’ to bypass electrical faults in the spine collection system. We will need to identify sources for suitable cables and connectors, preferably ones that can be mated live. The detailed design of the joints between sections of Duck spine will benefit from the experience of the Pelamis being built by Ocean Power Delivery Ltd. It would be very useful if joints could be made slightly buoyant and changed at sea without heavy lifting gear. Ducks become more attractive when sea space becomes scarce because they use all of it. Until then such close-packed devices suffer an economic handicap because of the initial investment in the large numbers needed for crest-spanning. However it may be possible to mount very short lengths of Duck between a pair of Maces. This should be tested at small scale. We have a great deal of information on the statistics of tension and bending of both mooring cables and electrical down-feeders. Neither seem to be a problem for Ducks because they reflect very little energy and transmit all the excess energy towards the beach. Some of the beachward transmission is at a higher frequency so the mean mooring force can reduce with higher sea states. For this reason little attention has been given to sea bed attachments and the costs have been based on rather crude clump anchors. This may not be the best solution. Ways of meeting requirements for R&D The cost of wave energy research is still quite low relative to the money being spent on energy in general and could be regarded as a very small repayment to our descendants in return for using the fossil fuel they might feel was partly theirs. Good research work can be done in both industry and universities but few industrial groups will want to pay for research unless there is a clear path to a return on the investment over a fairly short time. This means that universities should concentrate on the earlier stages of entirely new fields where the received opinion suggests that that the chances of success are marginal and the potential pay-off are distant but large. The supply of trained wave engineers will be crucial to the success of the industry and the range of techniques needed for wave energy is so wide that the people produced are highly employable in a wide range of engineering activities. Alumni of the Edinburgh group have made distinguished contributions to wind and offshore technology. One academic observer commented that for a long time this might be a more valuable product than the energy itself. This is particularly true with regard to the improvement of reliability that is so important for obtaining acceptable load factors. DTI should encourage EPSRC to set up a training unit where young engineers can obtain graduate qualifications and more experienced people from maths physics and computer science can get a conversion course in renewable energy. Even when everyone is trying hard, it is very difficult to transfer information from a university to a well-established industry because its import is subconsciously taken as an insult to the research teams in the company. Without a determined product champion, many imported ideas fail. The classic example is the rejection by IBM successively of transistors, integrated circuits and the mouse. It seems to be much better to encourage trained people who will start new companies. Industrial research is more suitable if it needs very large or expensive equipment or if it relies on the previous experience of the company. However there will be a strong incentive for the company to keep new results to itself. This is quite legitimate if the company is spending its own money but less so if it is a shared project. British companies have historically had a poor track record with regard to the fraction of their turnover which they spend on research. It might be possible to improve this by more generous allowances or even negative corporation tax for indisputable research spending whether by the company or by a university team working for it. It is however common for companies to exploit the technical ignorance of civil servants and use research and development contracts as cash cows. Schemes which rely on 50% sharing of research costs will often produce an increase of overheads by a factor very close to two! It is difficult for short-term commercial accounting pressures to respond to long term concepts such as planetary survival. Examples of industries which sacrificed long term good for short term profit are whaling, hunting of the North American buffalo and the present forestry practices in South East Asia and Brazil. It should be the duty of Government to moderate and redirect the immense power of the market. While we now think we know quite a lot about the necessary features of a good wave power device we cannot be sure that that the best ones have been identified. It is important that we do not stifle the development of new ideas. We can avoid wasting time on the awful ones which keep recurring by a sympathetic filtering process and an easily-completed costing spread-sheet. The established wave energy community faces a difficult decision with regard to investor- supported start-up companies. We want to make sure that every good device gets the chance to develop properly but we do not want to be dragged down by the failure of a device caused by rushed over-optimism. American investors seem to be particularly gullible and the originators of one wave energy company ended in prison for fraud. The non-existence of test data and design calculations is obscured for ‘reasons of commercial secrecy.’ Unsuccessful tests at sea damage the credibility of the entire technology and drive up the insurance costs for later plant. The DTI, in conjunction with the EU, should seek ways to ensure that devices are not deployed prematurely without proper tank tests in extreme waves and comprehensive fatigue calculations. The series of rigorous model tests over a range of gradually increasing sizes and linked to sound theoretical modelling, as being followed by Ocean Power Delivery, will allow the many inevitable mistakes to be revealed cheaply and safely. However I believe that there are other young companies who are rushing to sea with inadequate preparation or understanding and who are ignoring the lessons learned from tank experiments. One solution would be for commercial wave power companies to disclose all their test results and design calculations for impartial and independent scrutiny by people who have won the trust and confidence of everyone. This very difficult task was achieved by Tom Thorpe. A very difficult decision must be made about the balance between tank testing of small models and larger scale outdoor work. Enthusiasts for ‘real sea ’ tests can rightly claim that the confidence of the public and the politicians will be greatly increased by a successful outdoor demonstration because there is no way to ‘cheat reality’. But for exactly the same reasons there will be a great reduction in public confidence resulting from a spectacular failure which might be the result of a very minor problem, quite unconnected with the essential features of a device. The chances of failure are much greater if design and tank testing have been rushed, corners have been cut, money has been short and the test schedule set for reasons of public relations and investor confidence. People working on the early tenth-scale trials have privately admitted that almost nothing was learned from them even though they swallowed much of the money. Good wave sites are bad construction sites and even worse laboratories. It is accepted that most the important forces on most wave devices follow Froude scaling rules and so tests at scales as small as one in a hundred are safe. With indoor tanks you can have exactly repeatable extreme waves and automatically sweep through a year’s wave climate in a few hours with concentration on the most dangerous conditions. When something breaks you can stop and repair it and nobody gets killed. With outdoor tests it is impossible to control or repeat the test conditions and quite difficult even to measure what they are. Some devices are even too dangerous to approach when the sea state is at its most interesting. The work of many commercial tanks used to involve the measurement of the drag of ship models and, more recently, tests of marine structures in a pre-arranged set of sea states for insurance requirements. In many cases it is possible to say exactly how long the procedure will take and even to print the test results on a standard form. Wave energy tests are much less predictable because more dimensions such as ballasting and the power conversion strategy are being explored and we are less familiar with the devices under test. We may not even be completely sure of what we are trying to discover. Perhaps because of advice from towing tanks, many wave inventors grossly underestimate the amount of tank time that will be needed to make sure that their devices are safe and will make plans for launch dates which cut testing time to far below safe levels. When enquiries are made about behaviour in extreme conditions the reply is that the missing information is there but commercially sensitive. The minimum requirements are: • Tests corresponding to about 15 minutes at full scale in a realistic spectrum of directionally spread waves over at least five energy periods with a sweep up the amplitude range to about 30% above the maximum of the annual scatter diagram. The peak and root-mean-square values of every design parameter should be recorded. The tests should be done with normally operating power-conversion and also with the power-conversion, a fraction of mooring lines and any other controls out of action. Any peak value above 3.5 times the root-mean-square value is an indicator of a possibly dangerous non-linearity and should be investigated more closely. The first results should be examined to see if the test points are close enough in the interesting places. The results should be combined with the annual probability of the various sea states to allow a fatigue life prediction. • Wide devices should repeat the above tests with the addition of variation of directional spread. • This would be followed by repeated tests in a wave group which includes a steep version of the 100 year extreme wave but with the model placed at a series of positions relative to the nominal break point. All the critical forces and accelerations should be measured and the worst combination of conditions explored. • The calibration techniques must be carefully explained and the degree of repeatability demonstrated by replication of tests. The economics of tank testing are dominated by the fraction of time for which the tank is in use. An accountant would look at the cost of building the tank and the interest to be paid over the period over which it is written off. This will be divided by the number of hours for which the tank is used to give a rather high hourly cost. Many visitors to big tanks are surprised at how often no work is in progress. A very low use factor means a very high hourly rate which in turn means an even lower use factor. Because the hourly cost is high, the thoughts of every user are dominated by the ticking of the money clock. This is an unfortunate intrusion on scientific research. It can lead to skimped calibrations, missed double-checks and the failure to follow up puzzling observations. The alternative calculation would say that the money to build the tank has been spent and that, for the nation to get good value in return, every possible hour should be used. Users should be able to have 24-hour days and 31-day months. Rations of off-peak time should be given free to students and, ideally, any would-be wave inventor who has enough determination to make a test model. Commercial tank operators make the biggest profit by repeating previous test procedures for new clients. Academic users are always looking for the unexplained. I have worked in both commercial and academic tanks and I firmly believe that for wave energy in its present state the best conditions will be achieved in a University environment especially if this has several energetic students on hand. The value of staff working with sophisticated installations rises steadily with their experience. A tank needs a secure core funding for both mechanical and electronics maintenance and enhancement of the instrumentation systems. When disaster occurs to a final design, everyone involved has a motive to conceal the reasons. It is expensive to recover the broken bits for forensic analysis and nobody wants to pay to do so. Many boilers burst, ships sank and aeroplanes crashed before we achieved present safety levels. We should follow the pattern of investigation of aircraft accidents with full circulation of findings so as to maximise the value of the lessons. This could be made a contractual requirement for the receipt of public money. The economics of demonstrations can be ruined by lengthy local authority planning procedures and by the costs of grid connection which can double the total cost. It is interesting to ask if blanket planning permission for a vaguely-described family of wave-energy devices could be obtained for a rather wide sea area, once and for all. Transfer of technology from the offshore oil and gas industries. The academic wave energy community will take great interest in what is available if the information can be provided in a complete form with the maximum of hard numbers especially with regard to costs and the way costs would change with higher production rates. We have also learned many useful things from anecdotal ‘atrocity stories ’ of things that went wrong, often revealed late in a social evening. Of particular interest will be information on safe stressing of materials subject to fatigue loading, techniques for the survey of sea beds needed for safe laying of transmission cables and experience with cable entrenching vehicles. The techniques developed by the offshore industry for accurate navigation and station keeping will be useful for maintenance. The areas of wave power devices exposed to biologically active water will be larger in proportion than for oil and gas platforms and so we are interested in bio-fouling and anti-fouling treatments. Recommendations for Government R&D funding strategy. While there might be a natural separation between industrial support channelled through DTI and academic support channelled through EPSRC it is desirable that the two routes are kept in close contact. University research teams and small start-up companies employ people with high motivation who work hard, learn fast and can be highly innovative. They are a valuable national asset. They are in the game for the love of it not for the money. But the DTI must realise that they are financially much more fragile and easily scattered than the large commercial companies. The typical official decision period for both DTI and EPSRC from a call to the start of work has been eighteen months -often longer than the period of the contract itself. Research teams can never build up capital resources to survive that sort of delay or deploy people to other projects. The decision time must be reduced and ways found to keep activities going steadily. Committee structures seem to be set up to spread responsibility so thinly that no heads roll after bad decisions. This does not lead to good ones. One improvement might be to allow a highly trusted official or small group who work together every day to take contract decisions without reference to a part-time committee or to the phase of the financial year. Another might be to let slightly vague generic core contracts which boil down to ‘you lot are hard working fellows who know lots about the subject and what is needed most. Here is some money. Do something sensible with it and then tell us what you have done. If we like what you do, we may give you some more. When we think of anything that we want you to do we will expect you to deliver it very quickly.’ The armed services manage very well on this basis. Such a proposal would demand open accounts and saintly financial behaviour on the part of the recipients. It would horrify every treasury official. However it must be pointed out that the present, very strict contract procedures used by MOD, DTI and DSS do not ensure financial efficiency or the rapid development of good equipment. The accountants in big commercial companies try to make them earn the greatest amount of money for the lowest quality of work that will just not lose them the next contract. University groups may soon be forced to operate in the same way but used to take pride in how much had been achieved on slender resources. Stress on device teams during the first wave programme was greatly increased by the synchronising of the reporting cycle to bring it into phase with the financial year. This meant that assessments of very different devices had to made at inconvenient times, quite regardless of their test programme or state of development. It should be left to a device team to set the time for appraisal when they are convinced that things are right. The payment of a bounty (NFFO, SRO, IRO etc) for electricity generated from various designated renewable sources specifically excluded waves but was successful for several of the more mature technologies. The replacement of this scheme by the requirement on electricity distributors to sell a certain fraction of power from any unspecified renewable source will have the effect of the most mature being able to stifle all emerging challengers. This is not a good way to encourage the diversity of supply. A large part of the cost of renewable energy is the repayment of initial capital and so the test discount rate is a vital input to the cost-estimating spread sheets. Historically new public investments were tested against a real return of 5% even though the actual return on capital by the old CEGB was as low as 2.5%. The test discount rate was later changed for renewable energy and values of both and 8% and 15% have been used. High rates favour technologies with short construction periods even if lifetime is short and fuel costs are high. They are particularly hostile to tidal barrage schemes which would provide slightly expensive electricity for twenty-five years and then almost free electricity for the next hundred years. Meanwhile interest rates in Japan to Japanese were for a long time almost zero. This meant that much of the non-fossil fuel obligation went directly to people who could borrow money from Japan. It could be argued that this is taking free trade to unnecessary lengths. Lancaster University Michael French (29/08/00) - Minutes by David Scarr Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment Tuneable moorings. A system with a stiff reaction causes extreme event problems. The attachment must be softened for peak loads. Alternatively, its vulnerability must be reduced (e.g. dive below surface). The FROG has an angel and sinker system, but only 2 moorings. Tank tests showed model tended to rotate but they don’t know why. Rubber joints for the moorings would be worth considering. 150te anchor pull required. Interested in durability of moorings. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Believes work is required on water hydraulics and seabed collection, pivots, seals and leakage of lubricants. A large hydraulic pump is required for pumping water to tune the FROG. Pneumatic power generation systems No work on this. Construction and Installation methods Plans a wet tow with tugs for the FROG (1500te device weight incl. 500te moving mass). Subsea power connection, power take off, flexible cables Can power cables run to devices along compliant moorings? Wave energy conversion devices and control systems Believes a good wave energy device has a small surface area and a large movement to minimise forces and maximise capture for cost effectiveness. Reaction is from either: 1. Phase diversity - several waves (e.g. the duck). 2. Amplitude diversity - change with depth. 3. Fixed to the seabed. 4. A mass provides a reaction. No tank tests on the FROG since 1986. It needs a large gas accumulator for storage. Hydraulic valves can be used to tune the time period by pumping water around inside the device. This concept needs to be checked to ensure it is a net energy gatherer (is more energy used to move the mass than the increase in capture efficiency). Do the BHR group have a rectifier? Also has a scheme design called the FROND which is similar to Salter’s mace. This is championed by Dr RV Chaplin at Lancaster. This doesn’t have dynamic tuning and needs some mathematical modelling. Power Quality - Connection to the grid No work on this. Development of Design, Operation and Maintenance codes for certification and due diligence Designed for minimal maintenance. It would be difficult getting aboard. Interested in data on the spatial form of waves - he uses the Matsui spectrum. Interested in arrays of devices - how close can they be placed. Long term corrosion resistance materials Currently only using cheap steel. Other Lots of problems with ETSU procedures/communication. Plymouth University Kate Bowling Fraser Johnson (31/08/00) - Minutes by David Scarr Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment Their device is catenary moored from a 10te anchor to float and then to device. Possible fretting problem at device attachment. Quick release not looked at - no plans for maintenance so have not considered retrieval scenario. Very confident of mooring analysis - done by Karen dynamics c/o Chalmers Uni. in Norway. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Hydraulics not part of scheme, rejected because of end-stop problem. Pneumatic power generation systems They have rejected a conventional Wells turbine because of low efficiency rating and problems with starting up. They are using an impulse turbine, believe this is better because of Japanese research paper. Babinsten turbine designed by IBK in Neurenburg and will be manufactured at Plymouth. Blades will be made from a composite for cost rather than performance. Would like to do CFD work on the turbine Construction and Installation methods Construction - they have lots of minor modifications they would like to include with the benefit of hindsight. Small, local steel fabricator building the device. Another local firm doing polymer floatation collar. Bottom 2m of longest OWC are fibreglass to cushion crashing into seabed. Installation - they have a scheme which looks rather using a local boat. They have not worked out detailed procedures or a retrieval method yet. Subsea power connection, power take off, flexible cables Power is dissipated in a resistor bank for this prototype. A full scale device would have a floating connection taken along a mooring line. This would affect the mooring analysis. A flexible connector is essential for large scale. Wave energy conversion devices and control systems They have been unable to match their tank test results (at UCC) with their numerical modelling. As a result they have problems matching the power take off system to the wave chamber. The prototype will be fully instrumented and data recorded to help this process. To collect the data they must board the device every 3 weeks - they didn’t trust reliability of a radio link and other transmission options were too expensive. Power Quality - Connection to the grid No experience of this. They are aiming very small - 5kW. AC Generator manufactured by French co. Believe a 15% efficiency will make the project economic. Development of Design, Operation and Maintenance codes for certification and due diligence Have not found any specific codes applicable. They’d like more wave data to be available in the public domain. Also an index of available previous work would be good. Loads have been calc’d from first principles and all structural design is to a BS (but FJ and KB are not sure which). Design has been done entirely by the Naval Architect. Probs with tank tests because they were unable to model the air flow through the device. Their device is insured by the university. No maintenance procedure yet. Long term corrosion resistance materials They are using a moulded composite for the turbine blades - reason is cost rather than function. Other EC funding under CRAFT Framework 4 (like Pico) - requires several countries to be involved. Note that the CRAFT funds allocated for Framework 5 are less than previously available. Scheme pioneered by Embley Energy and Rod Newlton (ex DTI, physics background). Since his death his assistant has provided commercial advice. They have patented the idea of multiple oscillating water columns. Queens University Trevor Whittaker William Beattie (23/08/00) - Minutes by David Scarr Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment Not applicable to any of the QUB work to date. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Interested in possibility of an alternative take off method for the OWC on Islay. Believe that a hydraulic take off scheme must use existing technology. Interested in hydraulic transmission back to shore. Pneumatic power generation systems This is where the majority of their experience lies. They do not particularly see a future in refining the mechanics of the Wells turbine. They believe that future efficiency gains will only be small and not improve dramatically the cost effectiveness of the scheme. The Islay plant has 3 chambers and only 1 is currently utilised (with a counter-rotating turbine). They are keen to test other types of Wells turbine (mono plane, dual plane and variable pitch) in the same wave regime on Islay. Japanese have tried a pneumatic accumulator without much success. u S scheme Neptune attempted to float on the surface but they see this as too difficult and unnecessary. Osprey II would suffer from many of the same problems as offshore wind. Construction and Installation methods Very interested in this. They believe reducing the high construction cost of Limpet will make it much more feasible. They do not like the contractual options (the first Islay scheme was an admeasured contract, the Limpet is design and build fixed price lump sum). They find offshore contractors are too conservative and onshore contractors have limited experience of building in this environment. Hydrodynamics of a breaking wave are not well known (esp. in horizontal distribution) causing conservatism in design. Constructors are averse to risk. Subsea power connection, power take off, flexible cables Not applicable to any of the QUB work to date. Wave energy conversion devices and control systems The Islay device is currently being instrumented up with pressure sensors. They are keen to gather data and analyse the wave regime and observe the power produced. In particular they wish to produce accurate wave data for the site - the spectrums they have used in the tank tests look different to the sea observed at Islay. They have a DTI contract for this work. They would like to produce standard sea patterns in the time domain to help tie in with the model tests. The difference between near shore and offshore waves is that they are taking off all of the incident waves, not just the extremes. A time series analysis is required. Near shore waves are naturally filtered by the topography. Interested in control overlaps with wind energy and would welcome any available information. Power Quality - Connection to the grid Integration and distribution are key issues. Storage of energy has long been identified as essential and only ever really achieved by Tapchan. There are 3 stages of storage 1. Over 1 wave cycle (10s) this can be achieved by a flywheel. 2. Modulated wave packet (1 to 5 mins) 3. Longer term (hours). These final 2 are very difficult to achieve. For power supply, there are 2 scenarios: 1. Desert island, no need to meet onerous grid requirements 2. Developed country, better quality expected. Generic rather than device specific research is required. 50% private funding requirement causes many problems here. They believe that grid reinforcement is required and it is not feasible for wave power to pay for it. They note that the current grid does not meet it’s own spec. They note that dealings with the grid have been much more difficult since privatisation. Development of Design, Operation and Maintenance codes for certification and due diligence They do not see the benefit in being too prescriptive up front. They note the current construction methods have lots of potential for accidents. Long term corrosion resistance materials They are interested in the cost effectiveness of their materials or turbines. Is it better to replace or recycle? Other They are interested in an energy accounting study as a measure of sustainability. Wavebob William Dick Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment We have asked MCS International in Galway to assist in the design of slack moorings and risers. MCS are experts in this aspect of the offshore oil and gas industries, calm buoy offloading systems being a relevant instance. Visit www.mcs-international.com We have every confidence in their ability to develop practical and appropriate solutions, but there will be a need for R&D here as an array of floating units poses some new challenges. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure The DTI, through the TCS scheme, provided some assistance in the early proof-of-concept stages of the PTO design. This work was carried out at Queen’s University, Belfast and Musketeer Engineering, Lisburn, Co Antrim. The results were very promising and R&D into more technical design developments is merited (see Power Quality, below). We intend using off-the-shelf hydraulic and other components where possible, especially where proven in the off-shore industries, and will design accordingly. Pneumatic power generation systems Not something that we have considered. Serious reservation regarding condensates, temperature differences and power-to-weight ratios. Construction and Installation methods Presently being looked after by Harland and Wolff Technical Services and Harland and Wolff SHI. H&W have good expertise in the design and fabrication of platforms and rigs for the offshore industry. Subsea power connection, power take off, flexible cables We have direct access to what expertise is available in this area. I am not really in a position to give you any useful comment, - no doubt there’s always going to be an R&D requirement. Breeding grounds, trawling, lobster and shellfish fisheries feature in the environmental aspects of placing cables. The Wavebob will be deployed in arrays so the connection costs, whilst substantial, will be spread over many units. Wave energy conversion devices and control systems I don’t understand the question, - isn’t this what we’re at ? Wave climate forecasting, from seasonal changes to down to a few minutes ahead will be required input. Power Quality - Connection to the grid The alternators will be driven by constant speed hydraulic motors and in the bench tests we had little difficulty in synchronising output with the mains. However a considerable R&D effort remains before a commercially viable system can be fully specified. To that end application has been made to the EPSRC / Research in renewable and new energy technologies, by Dr Colin Tindall, Queen’s University Belfast: ‘Design and control of hydraulic transmission systems for wave and wind energy converters’. Development of Design, Operation and Maintenance codes for certification and due diligence Maybe a bit premature, - can we adapt standard practices ? Long term corrosion resistance materials Not yet considered in detail. Sheet steel, appropriately protected, will be the main material for the full- scale prototype; other materials (GRP, ferro-concrete, UPVC) may have cost and performance advantages for certain elements. Bearing surfaces, rollers and rubbing strakes, etc, will feature. The offshore industries’ expertise has to be relevant. Energetech Tom Denniss Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment There is definite O&G expertise in this area, relevant to moored wave energy technologies. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure I'm sure there's something to be learned here form the O&G industry Construction and Installation methods With regard to our technology, I am sure there is expertise in the offshore oil and gas industry for the construction and installation of concrete gravity structures, and also the design of such structures based upon extensive experience with likely maximum breaking wave forces. Wave energy conversion devices and control systems Good control systems are necessary, but these seem to be developing adequately in-house among the handful of wave energy companies there is. Power Quality - Connection to the grid More research is needed. Long term corrosion resistance materials This is definitely an area where the offshore O&G industry can add value. Norwegian University of Science and Technology Johannes Falnes Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment Probably such a component or system will be very useful for an offshore wave-energy converter (WEC). I remember from the late 1970s, when we co-operated with the company Kvaerner Brug, that such a component was proposed (and probably even designed) for a wave-power buoy (point absorber) which force-reacted against a sea-bed mounted anchor, through a pre tensioned strut, rod or steel rope. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure For a successful break-through of wave-power utilisation I consider it very important to develop such components/systems. During the years from 1975 to 1979 we co-operated with the company Kvaerner Brug on the development of a wave-power buoy[7]1 which had a hydraulic system for phase control and power take-off[356]. Following the "wave-energy fashion” of the time, we subsequently changed to pneumatic machinery[11,15,25,328-332] instead of hydraulic machinery. In retrospect, I now regret that we did not continue with a hydraulic machinery. Since 1994 we have again pursued the development of WECs with hydraulic power take- off[36,41,43,45,113,363,364,369,370], however with significantly less financial and personal resources than were available to us during the years around 1980. I am afraid that hydraulic machines developed and used in other industries, including the offshore petroleum industry, do not have sufficiently high energy-conversion efficiency as required for application in wave-energy conversion. Pneumatic power generation systems These may be of interest for first-generation WECs of the OWC type. But in the long term, I believe that hydraulic machinery has a better potential, than pneumatic machinery, to be developed to a stage of the high energy-conversion efficiency which is required for future WECs which are controlled for obtaining optimum oscillation, where the target is to obtain a high converted useful power, not with respect to the natural wave-power level in the sea, but with respect to cost of capital investment, maintenance and operation. Construction and Installation methods When, sometime in the future, a prospective WEC has been developed, it will also be important to consider particular construction and development methods. Subsea power connection, power take off, flexible cables Concerning this matter, I have little experience and knowledge, but I may mention that, when we in 1982 worked on a proposal of a power plant consisting of 410 phase-controlled pneumatic wave-power buoys[330] off the Norwegian west coast (near 62 o N), an internal (not published) report no. 82-112 from the company Technocean i Goteborg AB, Gothenburg, Sweden, on the electric transmission part of the project, was written by Mr. A. Kinnander on contract from us. Wave energy conversion devices and control systems This matter, including measurement sensors and electronic software, is, in my view, the most important branch of technical components/systems to develop in order to make wave-energy competitive. Power Quality - Connection to the grid On this matter I have little experience and knowledge. Development of Design, Operation and Maintenance codes for certification and due diligence Since, in contrast to ships and offshore oil-production platforms, WECs are usually unmanned, less restricted codes are required. Long term corrosion resistance materials When, sometime in the future, a prospective WEC has been developed, it may be important to consider long-term corrosion resistance materials. When we in 1982 worked on a proposal of a power plant consisting of 410 phase-controlled pneumatic wave-power buoys[330] off the Norwegian west coast (near 62 o N), we also considered corrosion problems, and we then benefited from the offshore petroleum technology to find solutions to corrosion problems. ADDITIONAL COMMENT: In my above comments I have several times referred to experience from our own projects. I have less detailed knowledge about other Norwegian wave-energy projects. However, I may draw your attention to a review paper[110] which I wrote in 1993, and to several of the papers in the Proceedings of the Second International Symposium on Wave Energy Utilisation (H. Berge, ed), pp 323-344, 1982. Tapir, Trondheim, Norway. (ISBN 82-519-0478-1), namely by A.Vinjar pp.11 -21, K.Torsethaugen pp.81-97, K.Karal pp.211 228, I.Fylling pp.229-251, N.Ambli et al. pp.275-295, R.Hardell pp297-304 and E.Mehlum pp.419-420. (1) Number within brackets ([...]) refers to entry # in our publications-and-reports list which may be seen on http://www.phys.ntnu.no/instdef/grupper/miljofysikk/bolgeforsk/publwave.html Swedish Hosepump Gunnar Fredrikson Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/restraint and mooring systems for rapid attachment and detachment Our flexible mooring system has functioned without problems. Forces in anchoring lines have been lower than calculated. No need for diver service. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Hose pump system was tested practically in the mid -80's with good results. The new HP-combination will need further practical, long-time full-scale testing. High pressure oil hydraulic system is based on standard components with high reliability. Pneumatic power generation systems No comments. Construction and Installation methods Construction according to standard ship-building and civil engineering practices. Installation (deploying)'can be done using a "full size" motorboat - type family cruiser. No divers needed. Subsea power connection, power take off, flexible cables Clusters of buoy units can be "hooked" together with hoses to one generator buoy. Have been tested practically without problem. Flexible cables will need further practical testing - long time. Wave energy conversion devices and control Conversion devices such as hydraulic displacement pumps and pelton turbines are available "from stock" - no problems. Control systems - such as-phase control - have to be tested and developed. Power Quality - Connection to the grid According to "grid people" in Sweden, UK and Ireland the power quality can be handled with available standard equipment. Development of Design, Operation and Maintenance codes for certification and due diligence No problem so far. Long term corrosion resistance materials Standard shipbuilding steel qualities have been used so far + glass fibre reinforced plastic (tubes). Stainless steel is an alternative for some parts. Special concrete has also been discussed - but not tested. Corrosion can be treated with standard paint - ship qualities. Ocean Motion International Michael Houser Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment Ocean Motion will utilise & further develop oil industry technology. Further technical research and development is necessary and would be beneficial. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Ocean Motion will utilise & further develop oil industry technology. Further technical research and development is necessary and would be would be beneficial. Pneumatic power generation systems Ocean Motion will not be using pneumatic technology. Construction and Installation methods Ocean Motion will utilise & further develop oil industry & present civil engineering technology. Further technical research and development is necessary and would be would be beneficial. Subsea power connection, power take off, flexible cables Ocean Motion will utilise & further develop oil industry & present civil engineering technology. Further technical research and development is necessary and would be would be beneficial. Wave energy conversion devices and control systems Ocean Motion’s patented designs are unique. Ocean Motion will utilise & further develop oil industry & present civil engineering technology. Power Quality - Connection to the grid Ocean Motion will utilise & further develop oil industry & present civil engineering technology. Development of Design, Operation and Maintenance codes for certification and due diligence Ocean Motion will utilise & further develop oil industry & present civil engineering technology. Long term corrosion resistance materials Ocean Motion will utilise & further develop oil industry & present civil engineering technology. Ocean Wave Energy Company Foerd Ames Wave Power Study 2000 Future development questionnaire With regard to the following areas of the Wave Power Industry, please identify opportunities where: • technical research and development would be beneficial. • an opportunity exists to transfer technology from offshore or other industries. Anchorage/ restraint and mooring systems for rapid attachment and detachment Many wave energy conversion designs typically necessitate high maintenance, costly, taut moorings or foundations per unit for operation while only using the extreme upper strata of an ocean site for energy conversion. Additionally, taut mooring deployment is limited to primarily onshore locations. Technology transfer is desirable for sea-based systems, particularly, with development of neutral buoyancy and damping techniques, self-supported impervious cabling, and quick dis/connects having security features. Hydraulic transmission, power drive systems, containment of hydraulic fluid under consistent high pressure Ocean Wave Energy Company (OWECO) avoids hydraulic fluid use in its OWEC Ocean Wave Energy Converter. Hydraulic circuits add unnecessary diversion and conversion steps from wave energy to electricity. Leaks are analogous to an electrical short circuit and additional troubleshooting is difficult. Instead, OWECs accumulate and distribute electrical energy using more standardised transmission components. Pneumatic power generation systems OWECs utilise relatively small-scale point absorbers having fixed buoyancy. Since buoyancy drives the system, energy conversion means are matched to average and maximum power take off available from a range of waves. OWECs are scalable to all wave ranges and arrays may include OWECs of various sizes. Construction and Installation methods The diffuse nature of waves requires a number of devices to generate significant electricity. Unfortunately, extremely few systematic techniques have been achieved. Extensive commercial development and utilisation is partly restrained due to practical limitations of many former devices that suffer inefficiencies of maximal potential use of available resources and materials. Commonly, wave energy converters are designed with absence of neutrally stabilised unit modularity by which methodology a self-supported module is interconnected with other similar modules of an array for expansion or reduction to any desired quantity. This quality is vital for matching the electrical product to changing end use demands. OWEC is a modular system benefiting manufacturing and deployment techniques. It is perceived that oil tanker holds could be retrofitted to contain multi-decks permitting close-pack OWEC module storage. At hydroface, OWEC rows are assembled into arrays and slipped into position. Take-up is achieved by process reversal. Analogy is made to highway Jersey barrier placement and take-up techniques. Subsea power connection, power take off, flexible cables OWECO continues searching for seaworthy self-sealing quick disconnect couplings combining mechanical and electrical attributes. We could greatly benefit from the knowledge and experience of offshore or other industries. Wave energy conversion devices and control systems OWEC utilises control features emphasising robust simplicity. An Ocean Wave Energy Web (OWEB) forms a sensor network that may be remotely operated, for example, over the Internet. Thus, forecasting analysis is a control for system pre-tuning. Power Quality - Connection to the grid The modular nature of OWEC allows several solutions, for connecting to the grid, each indicating a magnitude of scale. First use occurs with small scale, remote applications. As maritime operations grow, an umbilical cord may be attached to near shore-based functions. Over large scale, OWEC electrolysis operations may store and transport hydrogen, in the form of metal hydrides or the like, that allow great autonomy. Development of Design, Operation and Maintenance codes for certification and due diligence Codes development must permit latitude for ongoing industry innovations. With respect to deployment, site leases should include impact analysis and assurance of environmental quality maintenance. After useful life, installations must be completely removed with minimal or no long term effect on surroundings. Long term corrosion resistance materials OWECO has been following materials development over the years. Accelerating improvements in the availability of various plastics and coated metals now almost obviate corrosion problems, raise long-term reliability, and bringing down costs. Other concerns focus on sediment and marine growth. It is imperative to use non-toxic means to control upper levels of organism attachment to any sea-based device. Bio-based solutions must regard long-term environmental interactions and life form redistribution. Appendix D Technology Workshop Minutes Page D1 Wave Energy Technology Workshop Potential for Transfer of Technology from the Offshore Oil & Gas Industry Organised by Arup Energy, Ove Arup & Partners Friday 15 September 2000 @ Fitzroy Room, 6 th Floor, No 8 Fitzroy Street, London Chair 9.30am Registration 10.00am Welcome & D. Collier, Arup Energy Introduction Design, Construction, Installation, Maintenance Presenters Facilitator (Arup Energy) 10.15am Regulatory Environment A. Macleay &HSE Bob Boon, Lloyds Design Codes & Certification Dr. Don Smith, HSE 11.00am Norman Thompson, P. Bramhall Construction Offshore Contractors Methods/ Cost Association Estimation 11.30 am Morning Coffee 11.45am John Ridehalgh, G. Jackson Installation & Noble Denton Mooring Systems 12.15pm Rick Jefferys, Conoco R. Kollek Offshore S. Cardwell Operations & Maintenance Materials 1.00pm Lunch Power Generation & Transmission 2.00pm Introduction T. Lewis, UCC Presenters Facilitator (Arup Energy) Ian Chase, Rexroth R. Hyde Hydraulic Bob Flitney, BHR Systems Group, Prof. Stephen Salter, Edinburgh University 2.40pm Prof. Trevor Whittaker, R. Hyde Pneumatic QUB Systems Page D2 3.00pm Dr. G. Evenset, Alcatel A. Macleay Subsea Cables & Kabel Connectors 3.30pm Afternoon Tea 3.45pm Controls Systems Tony Bundock, ABB P. Horsley 4.15pm Power Quality and Grid Nigel Scott, Econnect R. Hyde Connection 4.45pm Summing up D. Collier 5.00pm Close Format for each Discussion: Facilitator introduction of the topic; key themes/ questions 5 minutes Presenters give overview of current technology and future developments 5 to 10 minutes Open Discussion chaired by Facilitator 20 minutes Attendee List: Name Organisation Wave Device Teams Dr. Tom Heath Wavegen Richard Yemm Ocean Power Delivery Prof. Stephen Salter, Jamie Taylor Edinburgh University Prof. Michael French Lancaster University Fraser Johnson, John Blight, Dr Ming Dai Plymouth University Prof. Trevor Whittaker, Dr. Bill Beattie Queen’s University Kim Nielsen Ramboll William Dick Wavebob Suppliers & Technologists, Certification, Regulatory Bodies Ian Chase Rexroth Bob Flitney BHR Group John Wilkins, Tony Bundock ABB Gunnar Evensett Alcatel Norge Nigel Scott Econnect Bob Boon Lloyds John Ridehalgh, Stuart Guy Noble Denton Norman Thompson Offshore Contractors Association Dr. Don Smith HSE Page D3 Rick Jefferys Conoco Rod Rainey WS Atkins Dr. Tim Camp Garrad Hassan Client Tom Thorpe, Richard Boud ETSU Chair David Collier Arup Energy Dr. Tony Lewis University College, Cork Facilitators Phil Bramhall Arup Energy Rick Kollek Arup Energy David Scarr Arup Energy Alan Macleay Arup Energy Peter Horsley Arup Energy Gordon Jackson Arup Energy Robert Hyde Arup Energy Simon Cardwell Arup R & D Apologies due to Petrol Shortages Terry Rhodes Shell Ian Tait Scottish & Southern Mark Jones, Wayne Jackson Tronic Page D4 Job title ETSU Wave Energy Study Job number 66032 Meeting name & number Preliminary Workshop File reference Location Fitzroy room, No.8 Fitzroy St Time & date 10.00 15 September 2000 Purpose of meeting Identify needs and transfer technology Present See Agenda Apologies Page D5 1. Regulatory Environment & HSE Presentation - Dr Don Smith, HSE The presentation outlined the applicable regulations HSWA and noted that an unmanned Wave Energy Converter (WEC) would fall outside of the regulations applicable to an offshore installation. The HSWA excludes some features applicable to wave energy devices and is accordingly being amended. An open consultation period ended 11-8-00 and the new amendments will come into force mid-2001. In addition, Management Regulations and CDM will apply. Discussion It was noted that offshore wind farms are experiencing many difficulties with the approvals procedure. Offshore wind companies are currently working to streamline this process. A request was made of official bodies to co-ordinate amongst themselves now, so they are able to grant permissions expediently when WEC’s approach them in the near future (next year). It was recognised that external investors would view a project more favourably if it could demonstrate its safety credentials. Design Codes and Certification Presentation - Bob Boon, Lloyd’s Register The criteria necessary for certification were outlined. Key issues for wave energy devices were highlighted and a comparison made with an offshore installation. Discussion The Schiehallion vessel was used as evidence of the unsuitability of using available design guides to estimate offshore loads. The importance of checking the applicability and compatibility of codes was stressed. A lack of design data for slam load calculation was noted and hence the importance of model testing. A lack of wave data in the shallower, coastal waters of the UK was also identified - perhaps HR Wallingford could help here. It was suggested that even with improved knowledge of wave loading a safety factor above unity must be retained to acknowledge the consequences of a failure event. Forcing the failure mode can improve safety. It was proposed that early prototype devices should have high factors of safety to survive and thus boost credibility although objections were raised that this would raise costs. 2. Construction methods & cost estimation issues Presentation - Norman Thompson, Offshore Contractors Association A description of the shipyard facilities at Nigg was given. Discussion A request was made by the WEC for more details of fabrication facilities. A request was made by the WEC teams for generic cost data. It was pointed out that this was not possible because construction costs are a function of many factors. A factor of 3 or 4 was quoted between the generic cost of a 1 off and the actual cost of a device. The best source of cost data is by working closely with a fabricator. Fabrication man-hours should be readily available from a fabricator. The best source of cost reduction is by working with a designer who has experience of similar works and fabrication techniques. A suggestion was made that fabrication costs could be reduced greatly if a relaxed schedule was possible. The importance of building a close team which covered all of the necessary disciplines was discussed. A cautionary note was made; EU competition rules forbid guaranteeing business in some instances. 3. Installation issues Presentation - John Ridehalgh, Noble Denton John briefly described the important aspects of any successful installation. He emphasised the need to consider all parts of the device life at the design stage. Discussion Page D6 It is recognised that if wave energy devices of the current style are to be economic, large numbers of them will be required. Therefore, they must be simple to install. Since WEC’s are sited in areas of high wave activity with significant background swell, the installation weather window will be short. Perhaps we need new technology to meet safety constraints here. Planning at the detailed design stage should be geared towards making best use of the available weather window. Given the risks to the project, perhaps experienced offshore installers should install the first generation of offshore devices. It was pointed out that such companies had a very low workload at present and would welcome new markets. A cautionary note was made about being over ambitious; it is better to successfully install a smaller device using methods you can afford than to lose a larger device because you cannot afford the correct installation methods. Mooring systems issues Presentation - Stuart Guy, Noble Denton Current mooring system technology was described. Discussion Pull-in plate anchors have been developed in recent years; they resist uplift making them suitable for taut leg mooring systems. Moreover, they are cheaper than standard anchors that are not configured to resist uplift. Achieving compliance is difficult. Chain fatigue, even at low loads, was identified as a problem not addressed adequately by codes. Mooring systems in shallow water can be equally complex as those in deep water. 4. Offshore Operations and Maintenance Issues Presentation - Rick Jeffreys, Conoco To reduce costs, Rick recommended against the use of divers or ROV’s. He suspected that it would be difficult to maintain a device in situ because of access in the working sea state (safety problems with boat transfers and unsuitability of heli-decks). Perhaps, it should be towed ashore for repairs. The question of the best material from a cost effectiveness point of view is difficult but his instinct is that concrete will be best. Discussion It will be interesting to see the procedures adopted by offshore wind. These have a gravity foundation and therefore are forced to be maintained offshore. Perhaps, unreliability must be factored into WEC schemes so that some malfunctions can be tolerated. Again, the failure mode must be designed into the system. Materials Issues Facilitator - Simon Cardwell, Arup R&D Reliability is considered to be the critical criteria in making appropriate material selections. Direct experience and expertise already exists for the performance of most common materials to be readily predicted. WEC teams must develop corrosion strategies to obtain a balance between low costs and high performance materials. Life cycle costing is likely to be an important aspect of material selection. Discussion WEC teams requested information on trends in reliability of materials. Erosion of rust (which is protecting the metal beneath) is an area for study. A review by an independent body of materials would be useful. The Siren on-line database is used by the offshore industry. Reliability data must be submitted by tenderers for MOD contracts so this information should be available from specific manufacturers. 5. Hydraulic System Issues Page D7 Presentation - Bob Flitney, BHR Group Ian Chase, Rexroth Stephen Salter, Edinburgh University The types of seal currently available were outlined. It was noted that elastometric seals are not very well developed at present. The problems associated with using different fluids were considered. The power spectrum of a typical wave train was discussed. An interpretation is that the high peaks represented the cost of a system and that the (much lower) mean value represented the return. Bringing these limits together (which may be done with a farm of OWCs) will increase the cost effectiveness of a design. Discussion Coatings produced by Hydradyne were recommended for corrosion protection. This coating is not machinable and is only suitable for low speed devices; a high speed one is under development. Seals were identified as a component which must be reliable to minimise maintenance although also cause significant losses. Water systems are subject to high leakage rates. A water/glycol based system can tolerate a degree of organic growth and has been used at pressures up to 200 bar. Hybrid systems were also suggested. Critical areas for a typical hydraulic system are contamination, fluid loss and temperature control. Power transmission by fluids has been done successfully over a distance of 2x100m (there and back) with 3-4% losses. Distances beyond this have been problematic due to water hammer effects and were not approved of by the audience. It was suggested that the need for control of a wave device necessitates a variable displacement pump. Energy storage for 100s was mooted as a requirement for synchronous generation (although storage of 25s would help considerably). It was noted that hydraulic accumulators are expensive and the possibility of reducing this cost suggested. For large WECs, an increase in efficiency of 1% of the hydraulic motor was sufficient to justify a factor of 2 on the upfront cost. Work using multiple input sources has been carried out by Artemis in Edinbugh. The novel solution to the end-stop problem by the IPS system was mentioned. A reliability database was requested although it was acknowledged that current data may not be representative in an offshore environment. 6. Pneumatic System Issues Presenter - Prof. Trevor Whittaker, Queens University Belfast The three types of pneumatic devices were described and a historical overview of their development given. The most successful OWC projects were detailed with advantages and disadvantages of the concept. Power take-off options were outlined. Suggestions were made for future areas of R&D and discussion points. Discussion The cost effectiveness of developing the Wells Turbine was questioned. A more important consideration is perhaps the control strategy and use of bypass valves. It was suggested that shore based OWCs are not a mainstream solution but a profile raising devices. Turbine bearings were identified as the principal maintenance issue. 7. Subsea Cables and Connectors Issues Presenter - Dr Gunnar Evenset A brief description of the specifications for cables installed recently was given. Concepts of static and dynamic cables were introduced. Reliability, maintenance and repair procedures were mentioned. Further developments were considered. Discussion The cable required by an offshore WEC was identified as a major component of the CAPEX. It was suggested that changes could be made at the design stage to reduce device power capture if cable costs were prohibitively high. Page D8 8. Controls Systems Issues Presenter - John Wilkins, ABB Tony Bundock, ABB A description of the typical control system and instrumentation hardware currently available was given. Discussion A researcher at Exeter University, Michael Belmont, is looking into prediction of incident waves. The typical measurements required by a hydraulic WEC are pressure, temperature, flow. It was generally agreed that instrument technology already existed for most measurement requirements in one industry or another. Communications, SCADA and remote reconfiguring are areas of interest. Telemetry (rather than cabling) is preferred. Hopefully, offshore wind will solve a lot of these issues first. 9. Power Quality and Grid Connection Issues Presenter - Nigel Scott, EConnect The components of the system between a wave energy device and the gird were identified. Cabling configurations for arrays were schematically discussed with respect to fault conditions. Key specifications for grid connection were identified. The Scottish grid was described. Discussion It was proposed that WECs need a stiff grid to supply power. An estimate of £0.5 billion was made for improvement costs. It was suggested that there was no incentive for grid companies to attach wave energy devices if they had to pay for the upgrades. The limit on generation imposed by the grid is set by the minimum demand in the summer - this is when wave devices generate least. A further problem is that all lines to WECs are invariably radials at the extremities of the grid. More favourable conditions exist outside the UK, particularly in Norway and Denmark. Perhaps a wave and wind schemes could be mated to produce a smoother supply. A study which produced a map of suitable connection points would be useful. Power delivery is limited by the E&I. The regulator must take action to make the grid more user friendly to the grid. Page D9 Appendix E Technology Workshop Questionnaire Results Page E1 Regulatory Environment & HSE Need For Further Main messages Development F u rth e r for N e e d Development Key Issues Further work is required on the planning and approvals process What Regulations will apply? 5 5 5 4 5 1 4 2 5 2 4 5 3 4 5 3.9 Will Energy Making Devices be treated the 5 5 5 2 2 2 4 2 5 2 2 5 3.4 same as Offshore Oil & Gas Installations? Planning Approvals/ Licensing Route? 5 5 5 5 5 4 5 5 4 5 4 5 5 4.8 Prototypes and Energy Making Devices - 3 5 5 3 1 2 1 5 4 4 3 5 3.4 Any Differences? Parallels? Offshore Wind, etc. 3 5 4 5 4 5 4 4 4.3 Potential For Technology Main messages Transfer T ra n s fe r for P o ten tial T e c h n o lo g y Key Issues Transfer of technology from the offshore wind industry on the planning Page E2 and approvals process is popular What Regulations will apply? 4 3 5 2 2 4 4 4 4 4 3 5 3.7 Will Energy Making Devices be treated the 3 3 2 4 3 4 2 5 3.3 same as Offshore Oil & Gas Installations? Planning Approvals/ Licensing Route? 3 5 5 4 5 4 4 4 3 5 4.2 Prototypes and Energy Making Devices - 3 2 3 5 4 4 1 3.1 Any Differences? Parallels? Offshore Wind, etc. 3 5 3 3 5 5 4 5 5 4 5 4.2 Page E3 Design Codes & Certification Need For Further Main messages Development F u rth e r for N e e d Development Key Issues Research is required to collect more wave data. Which Codes apply? DnV, HSE, API, BS? etc. 3 5 4 4 3 4 1 5 5 4 2 5 5 5 3.9 Certification and Underwriting Process? 3 5 5 4 4 4 2 4 4 5 2 5 5 5 4.1 Present Data Gaps; coastal wave environment 4 4 4 3 5 5 5 4 5 5 4 4 5 5 4.4 database, wave shapes, wave loading, etc. Potential For Technology Main messages Transfer T ra n s fe r for P o ten tial T e c h n o lo g y Key Issues Transfer of technology from certification of offshore structures will be useful. Which Codes apply? DnV, HSE, API, BS? etc. 3 4 4 4 4 1 4 5 5 5 3.9 Certification and Underwriting Process? 3 4 4 4 4 4 4 5 5 4 4.1 Present Data Gaps; coastal wave environment 3 4 5 5 2 5 4 4 2 3 5 4 3.8 database, wave shapes, wave loading, etc. Page E4 Construction Methods/Cost Estimation Need For Further Main messages Development F u rth e r for N e e d Development Key Issues Further work is required to be able to cost accurately. Life cycle costing requires further work. Installation methods require development. How do you estimate 2 5 4 4 5 4 3 2 4 5 5 4 5 5 4.1 accurately? Selecting the right Location 2 2 4 4 2 2 1 5 5 5 3.2 and Method of Construction? Offshore/ Civil Methods 2 3 4 3 2 2 3 4 3 5 5 3.3 Installation Methods 2 4 4 5 5 3 3 5 3 5 5 4 Manufacturing Methods 2 4 4 4 4 5 1 5 5 3 3.7 Prototype versus 2 2 5 4 4 4 1 5 5 5 5 3.8 Production Costs Life Cycle Costing 2 2 5 5 4 5 3 5 5 5 4 4.1 Page E5 Potential For Main messages Technology T ra n s fe r Transfer for P o ten tial T e c h n o lo g y Key Issues The construction and offshore industry can assist in selecting construction locations and methods. The offshore industry can assist in installation planning. How do you estimate 1 5 4 4 5 2 5 3 3 5 5 3.8 accurately? Selecting the right Location 1 5 4 4 4 4 5 4 5 5 5 4.1 and Method of Construction? Offshore/ Civil Methods 1 5 1 4 4 4 4 5 5 5 5 3.9 Installation Methods 2 5 2 4 5 3 5 5 5 5 3 4 Manufacturing Methods 2 5 1 4 5 2 2 4 5 3 2 3.2 Prototype versus 1 1 1 5 2 4 2 3 3 2.4 Production Costs Life Cycle Costing 1 5 2 4 5 2 5 5 2 4 4 3.5 Page E6 Installation Need For Further Main messages Development F u rth e r for N e e d Development Key Issues There is a need to develop installation programmes for devices and collect more data. Metocean Criteria 2 5 5 4 4 4 2 5 3 4 5 5 4 4 Floatout/ Towout 3 3 5 4 3 4 3 4 5 3 3 5 5 4 3.8 Installation Options; Self 2 4 5 4 4 4 4 5 3 5 5 5 4 4.2 installing, Marine Equipment Ease of Removal 2 5 4 4 3 3 5 3 3 5 5 5 3.9 Risk & Safety 3 3 5 3 2 4 4 2 5 2 3 5 5 5 3.6 Assessments Potential For Main messages Technology Transfer T ra n s fe r for P o ten tial T e c h n o lo g y Key Issues The offshore industry can assist Page E7 with floatout & installation. Metocean Criteria 2 5 5 4 3 4 5 3 4 5 4 3 3.9 Floatout/ Towout 3 5 3 5 4 4 4 4 3 5 4 5 5 5 5 4.3 Installation Options; Self 2 5 3 5 4 4 4 5 4 5 5 5 5 4.3 installing, Marine Equipment Ease of Removal 2 5 5 4 4 1 5 5 4 5 5 5 4.2 Risk & Safety 2 5 3 5 2 4 4 3 5 4 3 5 5 4 3.9 Assessments Page E8 Mooring Systems Need For Further Main messages Development F u rth e r fo r N e e d Development Key Issues Further work is required on the reliability of mooring systems. Conventional Options; Chain, Wire 3 2 4 2 3 4 5 1 2 4 5 3 2 3.1 & Anchor? Recent Developments; Taut 3 4 5 4 4 4 4 2 4 4 5 4 3.9 Moorings, Synthetic Fibre Ropes? Transfer of Technology; FPSOs, 3 4 5 3 3 4 4 5 3 3.8 Tanker Offloading, Dynamic Positioning Quick Release/ Re-attachment 4 4 5 4 2 3 5 3 3 1 5 3 4 3.5 Reliability, Maintainability 4 4 5 4 4 4 5 5 3 5 5 4 3 4.2 Deployment/ Retrieval 3 4 5 4 2 4 5 5 2 4 4 5 4 3.9 Page E9 Potential For Main messages Technology Transfer T ra n s fe r for P o ten tial T e c h n o lo g y Key Issues Generally, there are lots of opportunities to transfer offshore mooring systems for FPSO, CALM etc. Conventional Options; Chain, Wire 3 5 2 5 5 4 4 5 5 5 5 4 4 4.3 & Anchor? Recent Developments; Taut 3 5 4 5 4 3 4 5 5 5 4 5 5 5 4 4.4 Moorings, Synthetic Fibre Ropes? Transfer of Technology; FPSOs, 3 5 4 5 4 4 4 5 5 4 5 5 5 3 4.4 Tanker Offloading, Dynamic Positioning Quick Release/ Re-attachment 4 5 4 5 5 3 4 5 5 5 4 3 5 5 3 4.3 Reliability, Maintainability 4 5 2 5 5 4 4 5 5 5 4 3 5 5 3 4.3 Deployment/ Retrieval 3 5 3 5 5 3 4 5 5 5 4 4 5 5 3 4.3 Page E10 Offshore Operations & Maintenance | Need For Further Main messages Development 5 F u rth e r 5 for D D > D N e e d ] Key Issues Further work is required nto minimising operational costs and reducing maintenance. How to Keep Operational 4 5 2 5 4 4 4 5 3 5 5 5 5 5 5 4. Costs Down? 4 How to achieve Zero/ Low 4 5 4 5 4 5 4 4 4 4 5 5 5 5 5 4. Maintenance Strategy? 5 Repair Strategy; Return to 3 4 5 4 4 4 4 2 5 4 5 3 5 4 shore/Replace? Page E11 Potential For Main messages 3 > 05 Technology c £3 Transfer h £ e3 ) i;5 ) Key Issues The potential to transfer echnology is not as high here as elsewhere. How to Keep Operational 4 4 5 3 5 4 3 2 4 3 5 3 2 3 5 3. Costs Down? 7 How to achieve Zero/ Low 4 5 5 3 5 4 3 2 4 3 5 3 2 3 5 3. Maintenance Strategy? 7 Repair Strategy; Return to 3 5 3 4 2 3 1 3 3 3 3 shore/Replace? Page E12 Materials Need For Further Main messages Development F u rth e r for N e e d Development Key Issues Life cycle analysis R&D is the most popular but the scores here are relatively low. Corrosion Strategy 4 3 5 4 4 1 2 2 3 5 4 2 5 1 1 3.1 Balance between low cost and 3 5 4 4 2 3 2 3 5 4 4 5 1 3 3.4 high performance materials? Life Cycle Analysis 3 5 5 4 4 2 2 5 4 5 1 4 3.7 Potential For Main messages Technology Transfer T e c h n o lo g y for P o ten tial T ra n s fe r Key Issues There is lots of potential for technology transfer here. Corrosion Strategy 4 5 3 5 5 4 5 4 5 4 3 5 5 5 4.4 Page E13 Balance between low cost and 3 3 5 5 2 4 4 5 4 4 5 5 4 high performance materials? Life Cycle Analysis 3 5 5 5 3 4 5 4 5 5 5 4.5 Page E14 Hydraulic Systems Need For Main messages Further F u rth e r Development fo r N e e d Key Issues R&D is required on extreme environmental events and long term survival Fluid Types? 4 4 4 4 2 3 3 1 5 3 5 5 3. 6 Long Term Performance, 4 5 3 5 4 3 2 3 4 5 5 4 5 5 4. Reliability & Maintainability 1 Hydraulic Fluid 3 5 3 4 2 3 2 2 4 3 5 4 3. Containment against 3 Spillage Hydraulic Motors & 4 4 2 5 3 3 2 3 5 5 3 2 5 5 3. Rectification 6 Remote Hydraulic Power 4 1 3 4 1 1 3 1 1 2 2 5 2. Transmission 3 Response to Extreme 4 5 3 4 4 4 5 5 5 3 5 5 4. Environmental Events? 3 Page E15 Potential For Main messages Technology for Transfer P o ten tial T e c h n o lo g y Key Issues T here is little s ope for technology transfer here e cept perhaps in the question of fuel type. Fluid Types? 4 5 4 5 2 4 4 5 4 4 2 2 3. 8 Long Term Performance, 3 5 4 5 5 3 4 2 1 4 3 5 3 3. Reliability & Maintainability 6 Hydraulic Fluid 3 5 3 3 4 2 4 4 3 5 3 3. Containment against 5 Spillage Hydraulic Motors & 3 5 2 5 3 3 4 2 1 4 3 3 3. Rectification 2 Remote Hydraulic Power 3 3 4 1 1 1 1 3 1 2 2 Transmission Response to Extreme 3 5 2 3 1 5 2 1 2 2. Environmental Events? 6 Page E16 Pneumatic Systems Need For Further M ain messages Development F u rth e r for N e e d Development Key Issues Perhaps more work is required on reliability but there is little enthusiasm here. Wells Turbine Development? 3 5 1 3 3 2 4 3 2 2 2.8 Other Pneumatic Systems; 3 5 1 3 3 3 4 4 2 2 3 Impulse Turbine Development? Reliability and Maintainability? 4 5 4 3 3 4 1 4 3 3 3.4 Wind Turbine Transfer of 2 3 3 4 5 1 3 Technology Potential For Main messages Technology Transfer T e c h n o lo g y fo r P o ten tial T ra n s fe r Page E17 Key Issues Not really any potential for technology transfer here. Wells Turbine Development? 1 1 2 1 1 1 1 1 1 1.1 Other Pneumatic Systems; 1 1 2 1 2 1 1 1.3 Impulse Turbine Development? Reliability and Maintainability? 3 1 1 1 4 3 3 2.3 Wind Turbine Transfer of 1 1 2 1 1 3 3 2 1.8 Technology Page E18 Subsea Cables & Connectors Need For Further Main messages Development F u rth e r for N e e d Development Key Issues Little R&D is required other than in reducing costs. Transfer of Technology; 5 5 3 4 4 4 4 4 1 2 1 3.4 Subsea Oil and Gas, Wind Power Industries? How to Install at Low Cost? 4 5 5 4 5 4 1 4 3 5 5 5 3 5 5 4.2 Balance between High 4 5 5 2 5 2 1 2 2 3 3 5 3.3 Reliability and Low Cost? Use with Flexible Mooring 4 4 5 4 5 3 5 3 2 4 1 5 3 3 5 3.7 Systems? Reliability and 4 4 5 2 5 4 3 4 2 2 5 3 5 3.7 Maintainability Limitations for Cable Laying 4 5 5 3 2 2 3 2 2 5 1 3.1 Page E19 Potential For Main messages Technology T ra n s fe r Transfer for P o ten tial T e c h n o lo g y Key Issues There is lots of potential for technology transfer here in all areas. Transfer of Technology; 5 5 3 5 4 4 4 4 5 5 5 5 4.5 Subsea Oil and Gas, Wind Power Industries? How to Install at Low Cost? 5 2 5 4 4 3 4 5 5 3 5 5 4.2 Balance between High 5 2 5 5 3 3 4 5 5 5 4.2 Reliability and Low Cost? Use with Flexible Mooring 5 5 5 5 3 3 4 5 5 5 5 5 4.6 Systems? Reliability and 5 5 2 5 5 3 3 2 5 5 5 4.1 Maintainability Limitations for Cable Laying 5 5 4 3 1 5 5 5 5 4.2 Page E20 Controls Systems Need For Main messages Further for Development N e e d F u rth e r Development Key Issues R&D is required for optimisation of power take of and survival. Measurement & 5 5 5 5 3 2 2 5 5 2 3 3 3.8 control to optimise power take-off? Measurement & 5 5 4 5 3 2 2 5 3 5 4 3.9 control in extreme sea-states - equipment protection? System modelling, 5 2 5 4 2 1 2 5 3 5 4 3.5 simulation & advanced control Remote 5 5 3 5 3 1 1 2 3 4 2 5 4 3.3 control/monitoring - SCADA/comms? Suitable ‘packaging’ 5 2 5 4 1 4 2 5 5 2 1 2 3.2 for the environment? Technology Transfer; 5 5 5 3 1 2 2 3 2 1 2.9 robust packaging, high reliability, subsea technology, comms? Control of Power 5 4 5 3 1 3 2 3 5 3 5 4 3.6 Page E21 Generation Potential For Main messages Technology for Transfer P o ten tial T e c h n o lo g y T ra n s fe r Key Issues There is potential for technology transfer of remote control & packaging. Measurement & 2 5 1 5 4 1 4 1 4 5 1 4 3.1 control to optimise power take-off? Measurement & 2 5 5 4 1 4 1 1 5 1 4 3 control in extreme sea-states - equipment protection? System modelling, 2 5 2 5 4 1 4 2 5 1 4 3.2 simulation & advanced control Remote 4 5 3 5 4 5 4 5 5 5 4 5 4.5 control/monitoring - SCADA/comms? Suitable ‘packaging’ 5 5 2 5 4 5 4 5 5 5 5 4 4.5 for the environment? Technology Transfer; 5 5 5 2 5 4 5 4 5 5 5 5 4.6 robust packaging, high reliability, subsea technology, comms? Control of Power 3 5 2 4 5 4 5 4 5 1 4 3.8 Generation Page E22 Power Quality & Grid Connection Need For Further Main messages Development F u rth e r for N e e d Development Key Issues Lots of R&D is required here; energy storage, grid geography and approvals route. Mismatch of Demand & 5 5 4 4 4 2 4 5 4 5 5 4.3 Supply? Location of Grid 5 5 4 4 4 1 5 5 4 5 4.2 Connections? Power Quality? 5 5 5 3 4 2 4 5 3 5 4 4 Generator Type & Control 5 3 5 3 5 2 2 4 4 5 4 3.8 Energy Storage 5 5 5 5 5 4 3 5 5 5 4 4.6 Requirements Grid or Isolated 5 2 2 3 4 2 4 4 4 3.3 Communities? Fault Condition 4 5 4 4 2 3 5 3 5 3 3.8 Management? Technology Transfer - 4 5 1 4 3 4 2 1 3 Wind Market? Planning Approvals 3 3 5 5 3 5 4 5 4 4 4 4.1 Route? Page E23 Potential For Main messages Technology T ra n s fe r Transfer for P o ten tial T e c h n o lo g y Key Issues There is not much potential for technology transfer, other than from the wind industry. Mismatch of Demand & 2 1 2 4 2 2 1 2 Supply? Location of Grid 2 1 1 1 5 3 1 2 Connections? Power Quality? 2 5 1 1 4 4 1 2.6 Generator Type & Control 3 5 3 2 4 2 3.2 Energy Storage 2 5 3 2 2 4 1 2.7 Requirements Grid or Isolated 3 1 3 3 1 2.2 Communities? Fault Condition 2 5 3 4 4 1 4 3.3 Management? Technology Transfer - 3 5 4 2 5 5 5 4 4.1 Wind Market? Planning Approvals 2 4 2 5 5 5 3.8 Route? Page E24 Appendix F Bibliography Page F1 FI. LITERATURE BIBLIOGRAPHY “European Wave Energy Symposium ”, pub. NEL, Jul’93 “The offshore wave energy converter project OWEC-1 ”, Danish Wave Power APS, Dec’95. “An Overview of WaveEnergy Technologies ”, T. Thorpe, AEAT-3615, May’98. “Power fi-om the waves”, David Ross, pub, OUP, ’95 “Renewable Energy World- review issue 2000-2001 ”, pub. James and James, Aug’00 “A Review of Wave Energy”, T. Thorpe, ETSU Report R-72, Dec ‘92 “Wave energy converters, generic technical evaluation study”, Commission of the European Community, Aug’93 “Wave Energy -The Department of Energy’s R&D Programme 1974-1983 ”, ETSU, Mar’95 “Wave Power-Moving towards commercial viability”, pub. IMechE and DTI, Nov’99 F2. INTERNET BIBLIOGRAPHY F2.1 At Shore www. europa. eu.int/en / comm/dg 17/atl as/html/wave . html www.caddet-re.org http://www.capital-technology.com/waves.html www.isr.gov.au/resources/netenergy/aen/aen7/7waves.html acre. murdoch edu. au/ago/ocean/wave . html www.mech.ed.ac.uk/research/wavepower www.niot.emet.in/ml www.takenaka.co.jp/takenaka_e/techno/64_wvpow www. uni -leipzig. de/~grw/literatur? www.daedalus.gr/DAEI/PRODUCTS/RET/General/OW C / OW Cindustry.htm www.sovereign-publications.com/wavegen.htm www.wavegen.co.uk www. i si andstudi es. org/i slander/issue 1 /osprey. htm http://technology.open.ac.uk//eeru/natta/renew96(4).html Page F2 F2.2 Near Shore www.seapower.se www.eeca.org.nz/content/EW_news/50dec/50waves.html F2.3 Offshore www.plymouth.ac.uk/plymouth/publications/prel/20000703-1.htm www.owec.com http://mhouser.tripod.com/index.html www.jamstec.go.jp/jamstec/MTD/Whale/ www.oceanpd.com F2.4 Academic www.coventry.ac.uk/publicat/postgrad/schools/eng www.pubs.asce.org/journals/augey.html http://www.twics.com/~nsftokyo/ssr98-24.html www.newenergy.org.cn www.ul.ie/~elc/CompJoule.htm http://phys.ntnu.no/glos/grupper/stralbol/bolgegrp-e.html www.civil.soton.ac.uk/hydraulics www.hawaii.gov/dbedt/ert/bib/bib_wave.html www.mech.ed.ac.uk/research/wavepower F2.5 General www.waveenergy.dk www.artemisip.com www.forscotland.com/tracklab/waves971110URL.html www.dti.gov.uk/NewReview/nr43/html/review2.html www.energy.ca.gov/development/oceanenergy Page F3