Pumped Energy Storage System for the Randenigala Hydropower Plant in Sri Lanka
Duminda Nalin Habakkala Hewage
Master of Science Thesis KTH School of Industrial Engineering and Management Energy Technology TRITA-ITM-EX 2018:161 Division of Heat & Power SE-100 44 STOCKHOLM
Master of Science Thesis in Energy Technology
TRITA-ITM-EX 2018:161
Pumped Energy Storage System for the Randenigala Hydropower Plant in Sri Lanka
Duminda Nalin Habakkala Hewage
Approved Examiner Supervisors at KTH 2018-06-26 Miroslav Petrov - KTH/ITM/EGI Amir Vadiee, Miroslav Petrov Commissioner Local Supervisor Open University of Sri Lanka Dr. K.A.C. Udayakumar
Abstract The main focus of this thesis work is to perform a preliminary evaluation for the introduction of a pumped energy storage system to an existing hydropower plant located on the Randenigala water reservoir in Sri Lanka. The selected power plant is located in an area where farming is done extensively, therefore electrical power generation and release of water for downstream irrigation purposes is to be properly coordinated with relevant authorities. The solution to this situation is to introduce a wind powered pumped energy storage power plant to the Mahaweli hydro cascade for the purpose of saving peak power for around half an hour. A feasibility study was carried out on the utilization of wind energy and excess power to drive the motors of the pumped storage system.
Three versions with different numbers of pump motors and wind turbines have been considered to meet the half hour peak demand of the energy storage system. The optimum number of turbines and motor capacities and their number and brand have been selected with view of both energy and water management system.
Finally, the selected system case has been compared with the function of pumped hydro storage using excess power from the national electricity grid, in view of the expected expansion of new coal-fired power plants in Sri Lanka in the near future, where the existing hydropower will need to take the role of a system balancing factor.
The annual savings to the Ceylon Electricity Board using the optimum pumped hydro configuration were found to be Rs. 55 million per year (euro ~300’000 as of 2018).
SAMMANFATTNING Detta examensarbete fokuserar på den preliminära utvärderingen av en möjlig omvandling av det existerande vattenkraftverket vid fördämningen Randenigala i centrala Sri Lanka till en energilagringsanläggning genom att pumpa upp vatten från sjön nedströms och använda det till att lindra toppbelastningen i landets elenergisystem under de vardagliga kvällstopparna. En rak utvidgning av vattenkraften är omöjlig eftersom områdets vattenavrinning inte räcker till ny kraftkapacitet, samtidigt som nästan allt vatten används nedströms till storskalig bevattning av lantbruket som i sin tur styr mängden vatten som kan släppas ut från alla sjöarna i hela Mahaweli vattensystemet.
De föreslagna lösningarna inkluderar en vindkraftpark som kopplas direkt till pumpanläggningen; samt ett annat alternativ där överskottsel från den framtida expanderingen av nya kolkraftverk i Sri Lanka matas in så att vattenkraften får en fullvärdig balansrol i landets elkraftsystem. Storleken och anordningen av den föreslagna pumpanläggningen inklusive alla huvudsakliga komponenter och själva vindturbinerna med kopplingar emellan har beräknats och valts.
Flera möjliga anordningar för pumpanläggningen och kraftinmatningen har utvärderats och jämförts tekniskt och ekonomiskt, där en halvtimme av elsystemets toppbelastning på kvällen kan kapas och levereras av vattenkraften istället för de nuvarande diesel-eldade gasturbiner och kolvmotorer som används som toppkraftaggregat i landet. Den ekonomiska effekten beräknades till en årlig besparing på upp till 55 miljoner Rs (Sri Lankan rupee) för det mest optimala konfigurationen, som är lika med ca 3 miljoner svenska kronor om året (referensår 2018).
Table of Contents
Abstract 3
List of figures 5
List of tables 6
Nomenclature 7
Acknowledgement 8
1 Introduction 9
2 Problem Formulation and Objective 12
3 Methodology 13
4 Literature Review 15
4.1 Application of pumped hydro storage power plant 15
4.2 Wind Powered Pumped Storage System 18
4.3 Power Generation Expansion Planning of Sri Lanka 18
4.4 Power Station and Reservoirs of Mahaweli complex 22
4.5 Wind Data in Sri Lanka 23
5 Analysing and Calculation 25
5.1 Analysis Peak Saving Methods 25
5.2 Analysis and Selection of Centrifugal Pumps 27
5.3 Analysis of Wind Turbine data Characteristic 29
5.4 Different Options to Wind Turbine with the Pumped Storage Plant 34
5.5 Designing Water Flow Distribution System 39
5.6 Use Excess Power to Drive Water Pump 41
5.7 Economic Feasibility Analysis of Pump Storage System 44
6 Results and Discussion 49
7 Conclusion 55
4 List of Figures
Figure 1, Arrangement of Mahaweli Scheme River Basing 10
Figure 2, Geographical Area of Ransenigala & Rantambe Reservoir 11
Figure 3, Typical Arrangement of Pumped Storage with Wind Turbine 13
Figure 4, Pumped Storage System 16
Figure 5, Sea Water Pumped Storage System 16
Figure 6, Compositions of the Capacity Additions in Next 15 Years 20
Figure 7, Starts-up Duration of Plants 21
Figure 8, Power System Load Profile of Sri Lanka 25
Figure 9, Map of Central Province which is Ambewela and Randenigala Site 29
Figure 10, Monthly Wind Pattern in Ambewela Area 30
Figure 11, Randenigala Reservoir Area 31
Figure 12, Vertical Profile of Wind Profile by Web Based Software 31
Figure 13, Weibull Wind Speed Distribution for Randenigala Area 32
Figure 14, Result from power Calculator with 3MW Vestas V112 at Randenigala Site 33
Figure 15, Single Wind Turbine with Single Water Pump 35
Figure 16, Two Wind Turbines with Water Pump 36
Figure 17, Three Wind Turbines with Two Water Pumps 37
Figure 18, Change Load Profile over Years of Sri Lanka 41
Figure 19, Energy Mix over Next Years in Sri Lanka 42
Figure 20, Wind Speed & Rainfall Profile of Randenigala Area 43
Figure 21, Design Arrangement of Pumped Storage System 44
Figure 22, Cumulative Capacity by Plant type with Peak Power Variation 45
Figure 23, Normal Daily Load Curve of Sri Lanka Power System 50
5 List of Tables
Table 1, Required Capacity Plant Type 19
Table 2, Capacity Additions by Plant Type 20
Table 3, Wind Speed and Rainfall in Randenigala Area - Year 2013 24
Table 4, Matching Wind Turbines 33
Table 5, Summary of Wind Turbines Data 38
6 Nomenclature
Appellation Sign Unit
Acceleration due to gravity g m/s2
Head of pumped water H m
Pressure drop of Pipe Hf m
Length of a pipe L m
Efficiency η %
Efficiency of the pump ηpump %
Density of water ρ kg/m3
The hydraulic power needed to pump water Phdy kW
The power needed to pump water Ppump kW
The power at the shaft connected to the pump Pshaft kW
The average power which one wind turbine can produce Pave.turbine kW
Wind speed V m/s
Dynamic viscosity of the fluid µ kg/s m
Diameter of a pipe D m2
Velocity of water in pipe U m/s
Flow rate of a water Q m3/s
The area swept by the blades of a three bladed wind turbine A m2
Weibull Shape Factor, part of the Weibull equation k
Friction factor f
Reynolds number Re
Revelation per Minute RPM
Ceylon Electricity Board CEB
Long Term Generation Expansion Plan LTGEP
7 Acknowledgements
I take this opportunity to thank all colleagues who gave their helping hands for the success of this thesis. Without such cooperation I would not have achieved this goal.
Furthermore, my special thanks go to the project supervisors Mr. Miroslav Petrov and Dr. KAC Udayakumar who guided me from the beginning to the end for the successfully completion of this thesis.
Further, I would like to give my thanks to Eng. Ruchira Abeyweera who did the co- supervision and giving me various instructions while carrying out this project.
Let me take this opportunity to thank all staff in the transmission and generation planning branch of Ceylon Electricity Board, Department of Meteorology in climate change studies and Sustainable Energy Authority of Sri Lanka.
HHD Nalin
January, 2016
8 1. Introduction
One of the main problems of the load curve of the developing countries like Sri Lanka is that it has a poor load factor. The reason for this is that mainly the domestic consumers dominate the load curve. This means the country needs to generate electrical power which is utilized fully only for very few hours. As a result cost per unit of generation is high. One of the ways o solving this problem is “peak saving method” use of pump storage power plant is one of the options to solve this problem. The pump storage plant develop the power during the peak demand by release water from upper reservoir to the lower. During off peak time water is pump back to the upper reservoir by consuming power from the grid.
In Sri Lanka pumped storage plants do not exist at present. The present project is to investigate the possibility of utilizing one of the hydropower plants as pumped storage plant. What is new in this work is to use pumped storage system with energy produced by the wind turbines is use to drive the pump in the water from lower reservoir to upper reservoir.
The main source of electricity in Sri Lanka is based on hydro power generation. As at today the hydro power alone cannot meet the electricity demand of the country. It is required to find alternative technologies of electricity in Sri Lanka.
In this study, a power plant operated under the Mahaweli river project was selected. Water in the Mahaweli complex is meant for two purposes: irrigation and electricity generation. Today, the Mahaweli complex water utilization system gives maximum benefits to Sri Lanka, that is mainly with respect to irrigation and ecological system, socially & economically and electricity power generation.
The primary objective was Mahaweli complex to provide water for irrigation purposes. The use of water to produce electricity is the second priority. Mahaweli Authority and Ceylon Electricity Board jointly decide the water utilization of this reservoir’s in manner that both parties benefit ultimate giving the maximum benefit to Sri Lanka.
In considering Mahaweli scheme that is first reservoir Kotmale. It has three turbines and generation capacity of each unit 67MW. Output water release after power generation water
9 flow along the river to a small pond of Polgolla. Polgolla barrage water is divided to North Central Province for irrigation purposes. Remain water flow is carryout long tunnel to use to operate two 20MW drive the turbine in Ukuwela power station. Then releasing water use to operating two turbine units of Bowatenna power station. It is generation capacity 40MW and output water release to Anuradapura district for use to irrigation system.
In rainy seasons Polgolla pond over spill and water flow divert along the Mahaweli River to Victoria reservoir. Victoria power station has 3x70MW turbine unit at operation water use from Victoria reservoir. Then water release after operation at Victoria power station, water flow divert to Randenigala reservoir. It is largest reservoir in Mahaweli scheme. Randenigala power station capacity is 2x62MW and Radenigala power station output water release to Rantambe reservoir. The Rantambe reservoir is small pond and can be regulated. Rantambe pond water is use to operate 25MW capacity, two turbine at Rantambe power station. Output water from Rantambe power station is divert to Minipe annicut. This water is distribute to through right bank and left bank of Minipe canals to be use for irrigation system.
The water management system of the Mahaweli scheme is given in Appendix A. Cascade system of the Mahaweli scheme is given in figures 1 & 2 .
Source: CEB website Figure 1 – Arrangement of Mahaweli Scheme River Basin
10 Source: Google website
Figure 2 – Geographical Area of Randenigala & Rantambe Reservoir
Pumped storage power plant is storing energy at electricity demand of off peak time and energy release quickly at electricity demand of peak time. Country electricity demand changes throughout the day. Generally, peak demand of the system load curve occurs between 7:00pm and 8.30pm.
Therefore, the peak load is usually met by the hydro power plants. There can be instances in which the hydro power plants are not capable of meeting the total demand during peak periods. This is significant especially during the dry seasons in such instances to keep the power balance there can be load shading. The coal power electricity generation plant not suitable use to meet peak demand because it can’t be start up and pick up loads quickly. This plant most suitable use to base load operation.
The pumped storage power plant gives opportunity to produce electricity without releasing water to the downstream. This is important during the period when is not required for the irrigation purposes.
11 2. Problem Formulation and Objective
Aim; Introduce a wind powered pumped power plant to the Mahaweli scheme for the purpose of peak saving. If coal is used as base load then no excess power during off peak.
Objective; The main objective of this thesis was to do a feasibility analysis and design of a pumped storage system to be located at a Randenigala hydropower plant in Mahaweli complex area of Sri Lanka.
12 3. Methodology
Analysis of wind turbine parameters, water pump parameters and observe existing hydro plant data then applying different mathematical solution to propose the best system. The optimum pump storage system will be selected out of two options as of below:
Option - 1 To use pumped storage system which electrical energy produced by the wind turbines and produced energy use to drive the water pumps in the pumping station as shown in given below figure 3.
Figure 3 – Typical Arrangement of Pumped Storage with Wind Turbine
Option – 2 To use the excess grid power to pump the water in pumped storage power plants. In near future large capacity coal power plant will cover the base load and intermediate load in Sri Lanka. Hence, in the off-peak time, the associated coal power plant can provide energy for water pumping which will store water from lower reservoir at Rantambe to Randenigala upper reservoir.
For this purpose use the application software package of Microsoft Excel for create graph and calculation part, software package of Windenergie – Datender Schweiz.htm for selection of
13 wind turbine and software package of ITT industries or Goulds pump selection system for selection of centrifugal water pump.
Methodology graphically can be illustrated as,
14 4. Literature Review 4.1 Application of pumped hydro storage power plant
Pumped storage power plant is storing energy at electricity demand of off peak time and energy release quickly at electricity demand of peak time. This type of plant used by some power plants for load balancing. Method of energy storage system is water pumped from a lower level reservoir to higher level reservoir. It use low cost off peak electricity power for drive water pumps. So, during period of high electricity demand, upper reservoir storage water release through turbines and generation electricity. Low electricity demand time use excess power generation capacity to pump water in to higher level reservoir.
Globally, use reversible turbine for pure pump storage power plant which is water between reservoirs combined pump storage plant generate their own electricity power like conventional hydroelectric plant through natural water flow.
Evaporation losses of expose water surface and conversion losses is approximately 70% - 85% of electricity energy use to pump the water in to the elevated reservoir. This technique is currently most cost wise effective of storing large amount of electricity energy on operation basis. But capital cost and appropriate geography are critical decision factors.
Relatively low energy density of pump storage system is required either very large body of water and large variation in height. Example 1,000kilograms of water or one cubic meter of water at the top of 100meter tower has potential energy of about 272Wh.
Pump storage system is most be economical because it flattens out load variation on the electricity power grid. Thermal power plant such as coal power plant, combine cycle power plant and nuclear power plant and some of suitable renewable energy power plant can be provide base load electricity demand to continue operating at peak time. At the movement, in electricity system use for peaking time power plant that unit cost very high. But pumped storage power plant capital cost is high.
When considered energy management system, pump storage pant system help to load flow control in electricity network frequency and provide reserve power generation.
Load flow system of electricity generation and transmission system, thermal plant are much less able to response to sudden changes of electricity demand because causing frequency
15 and voltage instability. Considering of hydroelectric power plant and pump storage plant cab be quick respond with power system load changes within few seconds.
The working principle of pump storage plant is shown given below in figure 4 and currently operated Okinawa sea water pump storage power plant in shown given below in figure 5.
Source: Google website Figure 4 – Pumped Storage System
Source: Google website Figure 5 – Sea Water Pumped Storage System
16 Number of countries of the world utilizes pumped storage plants. One of the biggest stations is power station at Dinorwig UK with the capacity of 1,800MW. The plant can supply about 1,320MW in twelve seconds. A small pumped storage plant can also be useful and one of the smallest one is in Germany with a capacity of about 0.5MW.
Globally interest in building pump storage power plant is to reach the peak electricity demand become more popular. This will probably be more important in the future when countries need to balance and guarantee the reliability of electricity production because of increasing installation of unpredictable or irregular energy resources that wind power plant and solar power generation plant. Pump storage power stations supply high value electricity power during peak hours to the electricity grid.
Pumped storage stations use low price electricity when the grid power demand is low in pump the water from low level reservoir to high level reservoir. As in pump hydropower plant energy use to store the water during full time. Power is the excess only use this energy during power is required. These types of power plants can be considered under energy storage devices. This method of energy storage is in fact to store electricity as potential energy.
A pumped storage station is needed for a hydropower plants station where water shortage can occur or generation and consumption of not absolutely synchronous. In all electricity networks there is a surplus or lack of electricity. A pumped storage power station can control and guarantee a safe operation in the electricity grid.
In a classical pumped storage power station design the turbines and the pumps are separate units. This has many advantages like better efficiency of the pumps when operated at full capacity using low cost surplus power.
Several advantages can be achieved that wind power park combined with pump storage plant system. The majority of wind parks combined with pumped storage systems are both connected to the electricity grid and generated electricity use to water pump to high level reservoir.
17 Electricity generated by wind turbine and use to during low consumption time to pump water to high level reservoir. It is water release again when there is the need to produce energy at peak times in the electricity network. At high electricity demand time and wind power not available time can be use storage water in upper level reservoir is utilized. At locations where variable tariff is applied there is the possibility to achieve significant economic benefits by design on optimum turbine and centrifugal pump.
4.2 Wind Powered Pumped Storage System
Mechanism of wind turbine is convert kinetic energy of wind to mechanical energy then converts to electrical energy. Today, wind turbines have highest efficiency, and they are reliable. More reliable supply of electricity can be achieved by combining one or more wind turbines with pumped storage power station.
At locations selection is pump storage station in place where, wind strength is sufficient for a wind farm installation. The wind farms electricity generations is used for both the pumped and the electricity grid. Example of wind power pump storage system installation is Gran Canaria Island. The installation in wind power pump hydro storage system is increase reliability of the electricity produced and utilization of wind power energy is connected to national electricity grid. In that system is promote clean energy, green energy and renewable energy.
The wind turbines are installed to generate the power for the pumps in a pumped storage power station. One possibility of connection is a direct connection of shaft with the rotor of the motor. This is called a wind-pump. This technology is mostly used today to pump water from underground wells in rural areas for agricultures purpose and multi-bladed wind turbines are used in this method.
4.3 Power Generation Expansion Planning of Sri Lanka
According to the Ceylon Electricity Board, electricity power generation and transmission design plan estimate required capacity according to base case are given below table 1.
18 Hydro Thermal Thermal Year Addition Addition Retirements 2×90MW GT part Kerawalapitiya CCY 2009 - plant - 2×90 MW GT part 20×10MW Midium Diesel 2×135MW Kerawalapitiya CCY 2010 - kerawalapitiya CCY plant plant 150MW Upper 2×75MW Gas Turbine 5×17MW Gas turbine 2011 Kothmale 1× 35 MW Gas turbine Kalanitissa 20MW ACE pwer 2012 - 1×285MW Puttalam Coal (Stage 1) Matara 22.5MW Lakdanawi Plant 4×18MW, 1×285MW Puttalam Coal (Stage 2) Diesel Plant 2013 - 2×250MW Trinco Coal (Stage 1) 20Mw ACE Power
2014 - 1×285 MW Puttalam Coal (Stage 3) - 2015 - 2x250MW trinco coal stage – 2 and 60MW Colombo, 1x300MW coal steam at east coast 2 100MW Diesel , 100MW ACE
2016 - 1×300MW coal steam – east coast -2 -
2017 - 1×300MW coal steam – east coast -2 - 2018 - 1×300MW coal steam – east coast - 2 115 MW Gas Turbine 7 at KPS 49 MW Asia Power plant
2019 - 1×300MW Coal Steam (West Coast 2) - 2×10 MW Medium 2020 - 1×300MW Coal Steam (West Coast ) Diesel 2021 - 1×500MW Interconnection -
Source: CEB, LTGEP Report Table 1- Required Capacity Plant Type
19 In the planning process, base case plan is identified and the sensitivity of the base case parameters is evaluated subsequently. The required power capacity of additional, according to base case are given above table 1.
Power capacity additional by plant type are summarized for 5 year period show in table 2.
Capacity show in graphically below in figure 6.
Type of Plant 2007-2011 2012-2016 2017-2021 Total additional capacity MW MW MW MW % Hydro 150 - - 150 3.1
Combined 315 - - 315 6.6 Cycle
Coal - 2,455 1,200 3,655 76
Gas Turbines 185 - 185 3.9
Interconnection 500 500 10.4
Total 650 2,455 1,700 4,805 100
Source: CEB, LTGEP Report Table 2 Capacity Additions by Plant Type
Source: CEB, LTGEP Report Figure 6 – Compositions of the Capacity Additions in Next 15 Years
20 The majority of share from total new capacity (76%) is coal base power plants. Therefore, coal power plant will play an important role in the supply of archive to future electricity of country in Sri Lanka. At the movement, according to the CEB – LTGP, government is going to introduce the huge coal power in to the Sri Lankan power system after year 2011. After completion of coal power stations, studies to pumped storage power stations can play a key role in generation perspectives. Cheap coal plants will be use to drive centrifugal pump during off peak time and most of the used energy will be recovered during night peak hours.
At the moment, country electricity load curve is not flat curve that should be excess power due to coal power plants. Country electricity power demand has change throughout the day. Example, use day to day electricity demand for TV, Kitchen, lighting and other purpose on case on sudden peak in demand. Currently, power station do not generate more electrical power in immediately. Therefor there will be power load shedding around the country and all sort of other trouble will occurs. Now, main problem in our country is most of electricity power generation by fossil fuel power plant. That take half an hour or crank themselves up to full power and also generally at high peak of load curve is worked out between 7.30pm and 8.30pm.
So, there is possible to install pump storage power plant due to availability of the excess capacity than base load in Sri Lanka power system after year 2015 using excess coal power. The daily load curve in Sri Lanka has two peaks. Day time peak at around 11.00am due to industrial demand and night time peak at 7.30pm – 8.30pm caused mainly by using household. Therefore, according to the electricity supply of Sri Lanka the way of supplying electricity on night peak time based on thermal power plant. Available power sources in Sri Lanka and it is starts up duration are summarized in graphically shown in figure 7.
3 - 5 Hydro minutes
Oil 3 hours
1 hours G as C / C 4 hours
C oal 5 days
Nuclear
0 1 2 3 4 5
Source: CEB system control Figure 7 – Starts-up Duration of Plants
21 4.4 Power Station and Reservoirs of Mahaweli complex
Mahaweli scheme have been six major hydropower station and total electricity capacity is 660MWs. Therefore, contribute around 13% electricity energy to Sri Lanka annually. So, major hydropower station under Mahaweli scheme are Kothmale, Victoria, Randenigala, Rantambe, Ukuwela, Bowatenna and Nilambe. Total area of covering in Mahaweli basin is 1,268sqkm. Capacity of each hydropower plant are Kothmale-67x3MW, Victoria -70x3MW, Randenigala-61x2MW, Rantambe -24.5x2MW, Ukuwela-20x2MW. Bowatenna-40x1MW and Nilambe-1.66x2MW.
Largest reservoirs in Sri Lanka are located in the Mahaweli River forming a cascade. Most upstream reservoir is the Kothmale Reservoir. Downstream of this Polgolla diversion is located. The Victoria reservoir is the next reservoir in the cascade and downstream of this, Randenigala reservoir is located. A run-of-river generation Rantambe dam is the next and last dam of the cascade.
Randenigala reservoir is the largest reservoir in Sri Lanka holding more than 860mcm. The reservoir is centrally important to the country because of its storage for irrigation water, space for flood control and power generation. The irrigation area extends to the Eastern plains of the country. Just below the Randenigala dam a run of the river power plant called Rantambe is situated. About 4km downstream of this Minipe diversion weir is located. This diversion takes water to irrigate both left bank and right bank of the river. Further down the river is the Mahiyangana Township which is the largest inland town in the Eastern part of the country. The town is the social, economic and agricultural hub coordinating and providing for all needs of the agriculture community of the irrigated lands.
Rantambe Reservoir is the last reservoir in Mahaweli cascade system. It has a low capacity of less than 11.2mcm. Regulating the discharge is done by upstream Randenigala reservoir and this dam serves as run-of-the river type power generation after picking up the discharge from Uma-Oya River. The reservoir is centrally important to the country because of its power generation and its location upstream of the Mahiyangana city that attracts pilgrims. About 4km downstream of this dam, Minipe diversion weir is located. This diversion takes water to irrigate both left bank and right bank of the river. The irrigation area extends to the Eastern plains of the country. Further down the river is the Mahiyangana Township which is the
22 largest inland town in the eastern part of Sri Lanka. The town is the social, economic and agricultural hub coordinating and providing for all needs of the agriculture community of the irrigated lands.
4.5 Wind Data in Sri Lanka
CEB revealed that wind power is most promising one option from country available renewable source for electric power generation. In CEB pre electrification unit curried out resource asses management unit study of solar power and wind potential in year 1992. This study has cover overall wind potential of 8MWper sqkm in open land area. Wind power has overall potential in approximately 200MW in south eastern quarter of country.
CEB has been commission in pilot scale 3MW wind power plant located in southeast of the country at Hambantota area in year 1999. That plant yearly operated at capacity factor of 10.1% while in year 2010 capacity factor was 11.4%.
Also, through energy resource assessment unit of CEB has been studied in Puttalam area and Central region area carried out by year 2002. It has produce encouraging result on wind power energy potential in both areas.
By National Renewable Energy Laboratory of Sri Lanka has wind mapping study in year 2004. That is conform Sri Lanka has many area estimated have good wind resources. Most of resource tend to be locate in North western coastal region from Kalpitiya area to Mannar Island in Jaffna peninsula and central highlands areas. Also, NREL in Sri Lanka has estimate suggest that nearly 5,000sqkm of wind power resource potential. It is recommended additional study to assess practical resource by accounting for the transmission grid accessibility.
Renewable energy resource development unit of Sri Lanka Sustainable Energy Authority is identified district wise distribution of gross availability of different type renewable energy resources in year 2012.
I study of wind energy resource assessment perform a feasibility study of potential wind speed for an Abewela location.
23 The given wind data base has been based on the average value from several years and given per 10minut basis over the whole year. The required wind capacity is given in below table 3.
Wind Speed Rainfall Month Maximum wind speed Average wind speed Average (m/s) (m/s) rainfall Jan 9.87 3.94 117.9 Feb 11.25 4.09 167.6 Mar 9.09 3.74 30.0 Apr 7.68 3.03 127.9 May 18.19 8.42 1.5 Jun 23.05 14.69 0.0 Jul 23.54 11.31 38.5 Aug 22.55 12.33 4.9 Sep 25.51 9.04 31.7 Oct 24.09 7.92 263.8 Nov 17.71 4.41 193.0 Dec 18.68 4.35 569.3 Mean 17.60 7.27 128.84
Source: Weather Department of Sri Lanka Table 3 - Wind Speed and Rainfall in Randenigala Area - Year 2013
24 5. Analyzing and Calculation
5.1 Analysis Peak Saving Methods
Both industrial and commercial load in Sri Lanka still is low and electricity consume by domestic is greater. Therefore, country electricity power system load profile has poor load factor. It is not stable and flat curve. The reason for this is that mainly the domestic consumers dominate the evening peak and industrial and commercial load effected day time in the system load as shown in figure 8.
Source: CEB system control Figure 8 - Power System Load Profile of Sri Lanka [1]
According to electricity power system load profile is electricity power demand variation throughout the day. Sri Lanka is developing country. Therefore a requirement of electrical power usage in industrial sector is lower than the domestics sector. In generally cat high peak of load curve is worked out between 6.00pm and 8.30pm. This period huge number of domestic people use electrical power to domestic appliances. That case of a system demand is suddenly peak up and the power stations does not more electric power generate in immediately. Therefore, sometimes electric power load shedding is applied around the country in order to prevent blackout when demand exceeds generation.
25 Electricity generation by fossil fuel power plant like that gas turbine power plant and diesel power plant which take a short time (minutes) to crank themselves up to full power.
This project is not targeting full peak power saving but rather peak power saving of around half hour or until the thermal power stations catch up. According to appendix B, if consider evening time in between 6.30pm to 7.00pm of peak power saving for around half an hour and selected 100MW on system load side, then calculate required average energy of between times 6.30pm to 7.00pm.
According to the above analysis to required time of peak demand saving power time ½ hours. This short period time required energy to manage the time of peak demand as given below. From system load details of figure 4 and Appendix B,
Required peak power saving energy = 100/2=50MWh =50,000kWh
From Randenigala hydro power plant load details of Appendix C,
Power plant capacity of one unit = 62MW Full loading power of one unit for ½ hours = 62x0.5 = 31MWh = 31,000Wh = Spinning reserve loading plant capacity 82% Power output of spinning reserve load = 31x0.82 = 25MWh = 25,000kWh Both unit power output of 82% load = 25x2 = 50,000kWh
Required peak power saving energy = Energy releasing for half an hour of unit-1&2
According to the above analysis to required water management for ½ hour time is given below, From Randenigala hydro power plant water released data of Appendix C,
Capacity of output water in one unit at full load = 90m3/s = 324,000m3/h Capacity of output water in two unit at full load = 648,000m3/h Output water capacity of both units at ½ hours = 324,000m3/h Output water capacity of two units at 82% load = 265,680m3/h
26 From water pump capacity data of Appendix D,
Maximum output water capacity of one pump = 1.83m3/s Output water capacity of one pump at 24hours full load = 1.83m3/s = 158,112m3/h Both pump output capacity at 24hours full load = 316,224m3/h
Pumping water capacity at 24 hours >Required water for peak power saving at ½ hour
5.2 Analysis and Selection of Centrifugal Pumps
Centrifugal pumps are most popular type of pumps due to durability, versatility and simplicity. Pump efficiency is measured by how much of the power input to the shaft is converted to useful water pumping by the pump. It is therefore not fixed for a centrifugal pump because it is a function of the discharge and therefore also the operating head and the frequency.
The pump will be connected with a shaft to gearbox and motor. One of many producers of pumps is the Goulds pumps corporation. The Goulds model 3175 centrifugal pump is shown in Appendix D. The ideal power used to pump water by a pump in watts often called hydraulic power is as follows;
Phyd = ρ x g x H x Q (3.1)
3 In equation 3.1 [7], Phyd – hydraulic power, ρ – density of fluid (water – 1,000kg/m ), g – gravitational constant (9.81m/s2), H – head of pump water (m) and Q – flow rate (m3/s).
In the market have Goulds pump, can pump maximum 1.83m3/s of water up to the height of 40m. This information is given in the total head and capacity graph and the Goulds software in Appendix D. This pump was selected, because all necessary information about the pump was available. The graph shows that a 20x24-28H Goulds pump at the height of 40m, can pump about 29,000GPM. This is equal to 1.83m3/s. The power calculated to operate the
27 pump with a flow rate of 1.83m3/s and the head equal to 40m is now calculated with equation 3.1;
Phyd = 1000x9.81x40x1.83 = 718kW
To pump 1.83m3/s of water up to a height of 40m and a minimum power of 718kW is needed. Because the pump is not an ideal machine and have loses. The pump power is divided by the pumps efficiency and the shaft power is as follows;
P shaft= Ppump/ η pump (3.2)
In equation 3.2 [7] Pshaft is the power at the shaft where it connects to the pump, Ppump is the power required to pump water and ηpump is the efficiency of the pump.
The pump manufacturers information and calculated from the Goulds software shown in Appendix D. States that the pump power at 890RPM is 990kW and the efficiency is 73%. The efficiency of the pump can also e calculated with the equation 3.2;
η pump = useful work output/power input
η pump = 718kW/990kW = 0.73 or 73%
The calculated pump efficiency is 0.73 or 73%.
Total hydraulic power required to drive the pump when pumping 1.83m3/s of water up to a height of 40m and pump efficiency is 73%. Shaft power can be calculated with equation 3.2;
P shaft= Ppump/ η pump = (1000x9.81x40x1.83)/0.73 = 984kW
Analysis and selection of most suitable water pump depend on the according to electricity system daily load profile, Randenigala dam and Rantabe reservoir water level data and available market hydraulic pump data. Therefore In this thesis can be selected and uses Goulds centrifugal pump type 3175XL water pump is total power at the shaft needed to pump 1.83m3/s of water up to height of 40m with pumps is about 1,000kW.
28 5.3 Analysis of Wind Turbine data Characteristic
Central Province was selected as the candidate area because of Randenigala dam site region and the good wind potential and the measured availability wind data by wind energy resource assessment in central regions of Sri Lanka which was conducted by sustainable energy authority.
According to the Sustainable Energy Authority of Sri Lanka, collected and available wind data has only Abewela area. Wind data in Randenigala has almost same in Abewela data due to geographically small distance and same province as shown in figure 9.
Source: Google website Figure 9 – Map of Central Province which is Ambewela and Randenigala Site
Monitoring and available wind data has locations in the Central Province which is given by the Ambewela area. So, the detailed is considered for analysis Ambewela area.
Available site wind data of Ambewela area and location in the elevation is about 1,800 above MSL. According to study of wind data overall wind flow in generally monsoon climate tine in Sri Lanka. That is characterized by south west monsoon period – May to September and north east monsoon period – December to February. Mean monthly wind speed pattern in Ambewela area as shown in figure 10 and Appendix G. Therefore, annual average wind flow speed in Ambewela area is 7.27m/s. it is measuring height is 40m.
29 Figure 10 – Monthly Wind Pattern in Ambewela Area [6]
According to the wind turbine characteristics parameters with site characteristics such as wind speed, frequency of wind patent, wind flow direction, site conditions, air temperature and rainfall pattern... etc.
Used wind turbine parameter analysis by ‘the Swiss wind power data website’. The web site is mandate by federal department of the environment, transport, energy and communications Swiss federal office of energy in Switzerland. Above software consists of calculators to obtain by wind flow profile, Weibull distribution condition, air density and wind power of turbine.
The wind profile calculator estimate for vertical wind speed profile. So, increase of wind speed with height above ground level, and ground level wind is strongly affected by obstacles and surface roughness. The high above ground level in uniform air layers of the geotropic wind as approximate 5km above ground level. The wind is no longer influenced by surface between two extremes wind speed changes with height.
Randenigala Reservoir have 2,330sqkm of catchment area, 861MCM of gross storage capacity, 558MCM of live storage capacity and 1,350Ha surface at retention level. It is largest surface reservoir as shown in figure 11.
30 Source: Google website Figure 11 – Randenigala Reservoir Area
According to the Randenigala reservoir data, it is largest surface reservoir. Therefore in this site practically has a very high wind speed in around the year. Can install the wind turbines in the catchment area on top of the mountains.
Therefore, it is called vertical wind shear. So, suitable roughness length for the Randenigala reservoir area is 0.0002 and wind turbine location is on the water surface of Randenigala reservoir. When the height above ground level, wind speed and roughness length are define the software calculate wind speed at different elevations. The output result obtained for the Randenigala reservoir area given below figure 12 and Appendix E.
Figure 12 – Vertical Profile of Wind Profile by Web Based Software [3]
According to wind turbine design requirement is variation of wind speed to be visualized accurately in order to optimize the design of turbine. The evaluation of field data on wind speeds gives the probable wind energy availability at the site. For this purpose can be use
31 web base software tool to approx. wind speed distribution with Weibull function. So, obtain Weibull parameters may subsequently use in power calculator to estimate the power electricity power production by wind turbine. The result obtained by Randenigala site is given in figure 13 and Appendix E.
Figure 13 – Weibull Wind Speed Distribution for Randenigala Area [3]
The following parameters of the Welibull distribution were used for web based software power calculations. • Mean wind speed (V) = 7.2m/s • Scale factor of Weibull = 7.87 • Shape factor of Weibull (k) = 1.48
The Swiss wind power data website power calculator has been run different type of more than 45 wind turbines. It is possible to estimate the energy output, plant factor and fill power capacity for site for different turbine types.
Also, it can be produce power production distribution curve, wind speed distribution curve and load profile of each wind turbine when it is subjected site parameters. That turbine availability of 100% was assumed witch are no losses due to down time, park effects and power transformer losses. The best optimum result of wind turbine obtained for the Randenigala site is given in figure 14 and Appendix E.
32 Figure 14 – Result from power Calculator with 3MW Vestas V112 at Randenigala Site [3]
In Table 4 from Appendix E, shows the selected best wind turbine from more than the 45 different wind turbines. Table 4 ; Best wind turbines from 45 different wind turbines of Swiss power calculator Wind Turbine Max_ Power Capacity Power Average power Model Capacity Factor Production (kW) (kW) (%) (kWh/year) D8/80Dewind 2,000 26.6 4,660,452 532 G87 Gamesa 2,000 29.1 5,103,301 583 90 Vensys 2,000 27.4 6,009,348 686 100 Vensys 2,500 29.5 6,459,581 737 V80 Vestas 2,000 27 4,726,102 540 V90 Vestas 3,000 24.5 6,439,750 735 V112 Vestas 3,000 31.1 8,190,553 935 V 112 Vestas 3,075 30.5 8,219,227 938
Table 4 - MatchingWind Turbines
33 5.4 Different Options to Wind Turbine with the Pumped Storage Plant
Currently modern wind turbine is based on aerodynamic lifting. The blades interact with the wind and use both the drag force and lifting forces (Perpendicular). The lifting force are mainly driving turbine power rotor because it is multiple of drag force. Lifting force of air flow are intercepted by rotor blade and causes necessary driving torque for the wind turbine.
Modern horizontal axis wind turbines like Vestas V112 consist of tower, rotor, blades and nacelle located on top of tower. Nacelle contain the gearbox and generator. In large wind turbines, wind vane, anemometer and controller, control the yaw drive to point the rotor into or out of the wind. The pitch controls the blades capture maximum power from wind.
As shown in power profile at Appendix E, for the wind speed interval 7m/s to 10m/s, an average of 1,000kW are produced at 7.27m/s. The column, Mean wind speed used, shows average wind speed where the mean wind power was collected from the power curve for the Vestas112. Produced energy kWh/y is the energy produced at each interval. From output energy of the Vestas112 wind turbine is 8,190,553kWh/y, converted to average power of the year;
Pave.turbine= power production / hours per year
Pave.turbine= 8,190,553kWh / 8,760 = 935kW
Calculated power usage at the shaft for the Goulde pump from equation 3.2 was 984kW. One Vestas112 wind turbine could be used to drive one pump up to a 40m height if no power was lost in the gearbox and motor. The power lost by friction of the shafts is not included in these calculations because the efficiency of the gearbox is estimated.
Therefore power loses in the turbine, motor, gearbox and a generator and pump to calculate in this purpose. The wind turbine and pump selection case studies wise as follows,
Case Studies-1
In feasibility studies one wind turbine has an installed a gearbox, a motor and a generator and is producing electricity power as shown in Figure 14 and power production information from
34 Table 4 is used. As shown in Figure 15, a 112m rotor diameter, 9,852m2 swept area per turbine and 119m hub height wind turbine has an installed a gearbox, a motor and a generator and is producing electricity. The expected efficiency of the wind turbine generator is about 95% [7]. The efficiency in the motor is estimated to be 90% [7]. The gearbox is expected to have 95% efficiency and the estimated centrifugal pump efficiency is 73% (see calculation in chapter 5.3).
The bus bar power 935x0.95=888kW, motor output power is 888x0.90=799kW, gearbox out put power is 799x0.95=759kW and centrifugal pump out put power is 759x0.73=554kW. The calculated pump out put power with the electricity motor is about 554kW.
Figure 15 –A Single Wind Turbine with Single Water Pump
The water flow rate can be calculated with formula 3.1, Q = 554/ (1000x9.81x40) =1.41m3/s<1.83m3/s (Equ-3.1 design flow rate) (3.3)
3 In equation 3.3 [7], water flow rate is Q=1.4m /s when water pump output power is Ppump =544kW, the density of the water ρ=1,000kg/m3, the gravitational constant g=9.81m/s2 and head of the water pumped H=40m. If one wind turbine producing electricity as calculated above has 554kW power to pump when the efficiency of a generator, a motor, a shaft and a pump are take into account. In equation 3.1, calculated water flow rates 1.41m3/s and design water flow rate is 1.83m3/s. Therefore the calculated water flow rate for one electrical motor connected to a centrifugal pump if 554kW is unusable for pumping as shown in figure 15 with the head at a 40m height.
35 Case Studies -2
If considered to feasibility studies two wind turbines, one turbine has a 112m rotor diameter, 9,852m2 swept area per turbine and 119m hub height with average power producing each wind turbine 935kW as shown in figure 16. Power production information from table 4 is used. Each wind turbine generators expected have 95% efficiency [7] and bus bar power is 935x0.95x2=1,776kW. The efficiency in the motor is 90% [7] and motor output power is 1,776x0.90=1,598kW.
The gearbox is having 95% and it is power is 1,598x0.95=1,518kW. The centrifugal pump efficiency is 73% and it is output power is 1,598x0.73=1,108kW. The power calculated at the shaft to the pump with the electricity motor is about 1,108kW. Two wind turbine with installed a motor, gearbox and water pump total output power is 1,108kW.
Figure 16- Two Wind Turbines with Water Pump
In Case Studies - 2, pump output power is 1,108kW when the efficiency of a generator motor, shaft and pump are taken into account. Also, calculated water flow rate is 1,108x1000/ (1000x9.81x40)=2.82m3/s and design water rate one water pump is 1.83m3/s. Therefore the calculated water flow rate for one electrical motor connected to a centrifugal pump if 1,108kW is usable for pumping as figure 16 with the head at a 40m height.
36 But analysis to saving peak few hours for generate electrical power is required water to flow is 1.83x2=3.66m3/s for one day cycle. Therefore cannot achieve to water flow is 3.66m3/s which is one unit as shown in figure 16. Also, two units are technically usable but economically unusable.
Case Studies - 3
If considered to feasibility as three wind turbines, one turbine has a 112m rotor diameter, 9,852m2 swept area per turbine and 119m hub height producing electricity as shown in figure 14 and power production information from table 4 is used. As shown in figure 16, wind turbine has operation in parallel with bus bar an installed two separate gearbox, two separate motor and three generator is producing electricity power is 2,664kW on bus bar. The each wind turbine generator is expected have 95% efficiency [7]. The efficiency in the each motor is 90% [7]. The each gearbox is having 95% efficiency and calculated centrifugal pump efficiency is 73% (sec calculations in chapter 3.4). The power calculated at the shaft to the pump with the electricity motor is about 720kW.
Figure 17- Three Wind Turbines with Two Water Pumps
37 In case studies - 3, this combination of one gearbox, one motor, one centrifugal pump, shaft and steel pipes is called one unit. For one unit has calculated flow rate for one shaft driven pump if 720kW is usable for pumping water to a 40m height is 1.83m3/s. Therefore most suitable to uses two units for saving peak few hours for generate electrical power is required water to flow is 3.66m3/s for one day cycle as shown in figure 17. Also, two pump units are technically feasible and economically usable.
In Table 5, shows the summary of all case most suitable and selected wind turbines are Veatas V112.
Table 2; Analysis and selection of wind turbine with pump Parallel operation of 1 wind turbine with 1 pump No. Type of Capacity WT Ave. WT BB power Motor power GB power Pump power 1 Pump uses Cal. Pump Wind Turbine (MW) power (kW) @95% (kW) @90% (kW) @95% (kW) @73% (kW) power (kW) power (kW) 1 D8/80 - Dewlnd 2 532 505 455 432 315 991 718 2 G87 - Gamesa 2 583 553 498 473 345 991 718 3 V80 - Vestas 2 540 513 461 438 320 991 718 4 90 - Vensys 2.5 686 652 587 557 407 991 718 5 100 - Vensys 2.5 737 701 630 599 437 991 718 6 90 - Vestas 3 735 698 629 597 436 991 718 7 112 - Vestas 3 935 888 799 759 554 991 718 8 112 - Vestas 3.075 938 891 802 762 556 991 718
Parallel operation of 2 wind turbine with 1 pump No. Type of Capacity WT Ave. WT BB power Motor power GB power Pump power 1 Pump uses Cal. Pump Wind Turbine (MW) power (kW) @95% (kW) @90% (kW) @95% (kW) @73% (kW) power (kW) power (kW) 1 D8/80 - Dewlnd 2 1064 1011 910 864 631 991 718 2 G87 - Gamesa 2 1165 1107 996 946 691 991 718 3 V80 - Vestas 2 1079 1025 923 876 640 991 718 4 90 - Vensys 2.5 1372 1303 1173 1114 814 991 718 5 100 - Vensys 2.5 1475 1401 1261 1198 874 991 718 6 90 - Vestas 3 1470 1397 1257 1194 872 991 718 7 112 - Vestas 3 1870 1776 1599 1519 1109 991 718 8 112 - Vestas 3.075 1877 1783 1604 1524 1113 991 718
Parallel operation of 3 wind turbine with 2 pump No. Type of Capacity WT Ave. WT BB power Motor power GB power Pump power 2 Pump uses Cal. Pump Wind Turbine (MW) power (kW) @95% (kW) @90% (kW) @95% (kW) @73% (kW) power (kW) power (kW) 1 D8/80 - Dewlnd 2 1596 1516 1365 1296 946 1982 1436 2 G87 - Gamesa 2 1748 1660 1494 1420 1036 1982 1436 3 V80 - Vestas 2 1619 1538 1384 1315 960 1982 1436 4 90 - Vensys 2.5 2058 1955 1760 1672 1220 1982 1436 5 100 - Vensys 2.5 2212 2102 1891 1797 1312 1982 1436 6 90 - Vestas 3 2205 2095 1886 1791 1308 1982 1436 7 112 - Vestas 3 2805 2665 2398 2278 1663 1982 1436 8 112 - Vestas 3.075 2815 2674 2407 2286 1669 1982 1436
Table 5 - Summary of Wind Turbines Data
38 5.5 Designing Water Flow Distribution System
When designing a water distribution system to determination the sizing of pipes, duct and the pressure drop in the system. Calculate diameter of pipe, Reynolds number Re, friction factor f and pressure drop Hf are calculate with equations 3.4, 3.5 and 3.6 and then simplified in equation 3.7.
Re = 4*ρ*Q/ (π*μ*D) (3.4)
In equation 3.4, Re is the Reynolds number, ρ is the density of the water (water is 1,000kg/m3), Q is the volume of the flow rate (m3/s), π is equal to 3.1415, µ is the dynamic viscosity of the water (1.5x10-3kg/s m) and D – diameter of pipe (m). To calculation friction factor f which depend by Reynold number Re of pipe flow, equation 3.5.
f = 0.316(Re)-1/4 (3.5)
In equation 3.5, f – friction factor and Re – Reynold number from equation 3.4. The water flow is laminar if the Reynolds number is lower than 2,000 in pipes, but if it is higher than 3,000, it is turbulent. To calculate a pressure drop, the equation 3.6 uses the friction factor f and is, 2 2 5 Hf = 8fLQ / (π gD ) (3.6)
In equation 3.6, Hf is the pressure drop, f – friction factor (equation 3.8), L - length of pipe (m), Q - volume of flow rate (m3/s) and π is equal to 3.1415, g – gravitational constant (9.81m/s2) and D - diameter of pipe (m). By simplifying equation 3.6, using Q=1.83m3/s and L=40m, the diameter of the pipe calculated with equation 3.7;
1/4.75 D = (0.099/Hf) (3.7)
In equation 3.7, D is the diameter of the pipe in meter and Hf is the pressure drop. The pressure drop in equation 3.7 now is calculated with equation 3.8.
Hf = ηxP/Q (3.8)
39 In equation 3.8, Hf - pressure drop in a pipe. η – Efficiency (73%), P mean input horse power at the shaft (1,109kW/0.746=1,486HP) and Q is the volume of the flow rate (1.83m3/s =1,830l/s). The pressure drop in a pipe calculated with equation 3.8.
Hf = 0.73x1486/1830 = 0.593
The pressure drop is about 0.593. The diameter of the pipe calculated with equation 3.7.
D = (0.099/0.593)1/4.75 = 0.686m
The calculated diameter of the pipe is 0.686m. In the calculations, steel pipes that are about 0.686m in diameter are use because of higher pressure capacity. The velocity of the water in the pipe can be calculated with equation 3.9;
V = 4Q/(π*D2) (3.9) V = 4*1.83/(π*0.6862) = 4.95m/s
In equation 3.9, V is the velocity of the water in the pipe (m/s), Q is the volume of the flow rate (m3/s), π is equal to 3.1415 and D is the diameter of the pipe (m). With a flow rate about 1.83m3/s and a pipe diameter of about 0.686m, the velocity of the water is about 4.95m/s.
According to the appendix C; Randenigala dam is given in statistics maximum head = 90m. Also According to the appendix H; Randenigala plant has actual plant factor = 21.88%. So, the actual head of Randenigala is very low. Also, energy production of Randenigala plant = 250GWhr and in CEB expected energy is 380GWhr.
Under my project scope, I have considered evening time in between 6.30pm to 7.00pm of peak power saving for around half an hour and selected 100MW on system load side. For that the pumping time is whole day.
Therefore, pump doesn’t have to pump up to the maximum head in Randenigala dam. According to the analysis of above data, pump efficiency and most economical pump available in market is 1,000kW, 40m height at flow rate 1.83m3/s.
40 5.6 Use Excess Power to Drive Water Pump
The objective in this section is how to utilize excess power which is produced during low electricity demand in the future and to apply the excess power to drive the water pumps.
The method is again to store energy through water pumping from lower level reservoir to upper level reservoir. Low cost off peak electric power is used to drive water pumps. During high electricity demand, storage water is released through existing hydro turbines.
Although, loses of pump process make the plant a net consumer of energy in overall, it provides revenue by selling more electricity during period of peak demand when electricity price is highest. At that time low electricity demand use excess generation capacity to drive water pump and water pump into the upper reservoir.
According to the CEB Long Team Generation Expansion Plan 2013 - 2032, the government is going to introduce for power generation system, the huge coal power plant in Sri Lanka at near future. Since, country power electricity load curve still is not flat. Curve there should be excess power due to coal power plants. Daily load profile scenario over the years in in Sri Lanka as shown in figure 18 and Appendix B.
Source: CEB LTGEP2013-2023 Figure 18- Change Load Profile over Years of Sri Lanka
41 There is a possibility to install the water pumps due available of excess coal power capacity than base load of power generation system in Sri Lanka in near future. According to the CEB – LTGEP report in duration year 2013 to 2032, energy mix over next years in Sri Lanka as figure 19 and Appendix F.
Source: CEB LTGEP2013-2023 Figure 19 – Energy Mix over Next Years in Sri Lanka
At that time coal power will be taking over the base load. Hence, off peak time, the associated coal power plants provide energy for drive water pump and pumping water from Rantambe reservoir to Randenigala upper reservoir. Hence, shown in figure 21 is most suitable for use to pumped storage system which electric energy produce by wind turbine use to drive pump in pumping station and also, to use the excess power to pump the water in pumped storage power plants in the off peak time.
Rainfall system of Sri Lanka has multiple origin type such as monsoonal, convectional and expressional. Annually rainfall system share above season and mean annual rainfall change from under 900mm in driest part – southeastern and northwestern to over 5,000mm in wettest part – western slopes of central highlands.
Country climate is dominate in topographical fractures and southwest and northeast monsoons regional scale with wind regimes. In past experience of climate change has 12 months period characteristic data. According to past data, climate scenario can be divide by 4
42 seasons as first one is inter monsoon season – March to April, second one is southwest monsoon season – May to September, third one is inter monsoon season – October to November and finally northeast monsoon season – December to February.
Figure 20 – Wind Speed & Rainfall Profile of Randenigala Area
Southwest-monsoon Season (May-September) has amount of rainfall during season change above 100mm to over 3,000mm is island. Amount of rainfall is rapidly decrease from maximum region to ward higher elevation in Randenigala area in Central Province as shown in figure 20 and Appendix G. but average wind speed from month of May to September very high. Therefore this situation is considered for typical arrangement of pumped storage system.
Final typical design arrangement is concerning use pumped storage system with electricity energy produce by wind turbines and use to drive pump in pumping station system and to use the excess power to pumps the water in pumped storage power plants. Also, consider southwest - monsoon season (May - September) rainfall profile of design arrangement.
In above mention figure 17 of Case Studies - 3 is small modification with combination of one gearbox, one mortar, one centrifugal pump, shaft and steel pipes is called one unit and two pump units are technically feasible and economically usable. Also to required power
43 transformer, circuit’s breakers and power bus bar to connected national electricity network for use excess power. Export power wind turbine can be used to national electricity network due to during southwest –monsoon season or pump system maintenance time. Therefore most suitable to uses two units for saving peak demand few hours for generate electrical power is required water to flow is 3.66m3/s for one cycle as shown in figure 21.
Figure 21 – Design Arrangement of Pumped Storage System
5.7 Economic Feasibility Analysis of Pump Storage System
Assuming, not for calculation evaporation loses from exposed water surface, losses of electrical transformer energy and zero maintenance and no expenses for installation or repairs. Also, check of economic feasibility in generally. From Appendix F, according to the CEB LTGEP – year 2013 to 2032 required capacity additions cumulative capacity by plant type with require peak power energy shown in figure 22.
44 Source: CEB LTGEP2013-2023
Figure 22- Cumulative Capacity by Plant type with Peak Power Variation
In this bar chart clearly seen that peak loading capacity is depend on the thermal power plants for the near future. Also, at the movement use to cover of peak loading power fuel type is auto diesel fuel. According to the data of the Ceylon Electricity Board there are existing peak loading plants such as diesel engine power plant and gas turbine plant available at Kalanitissa power station which is open cycle 105MW gas turbine is installed in 1997. Fuel type of auto diesel is used in the gas turbines. The fuel is delivered from the local Ceylon Petroleum Corporation refinery by pipelines.
Gas turbine power generation cost
From Appendix I, existing 105MW Kalanitissa gas turbine power plant generation unit cost is around 32.00 Rs./kWh. Therefore at that time peak loading energy cost is 32.00 Rs./kWh.
From system load of figure 8 and Appendix B, This thesis required peak loading energy per day = 50,000kWh Gas turbine power generation cost = 32.00 Rs./kWh Cost of peak loading energy for ½ hours per day = 32.00x50, 000 Rs.1, 600,000.00
45 Randenigala hydro power generation cost
From Appendix I, existing Randenigala hydro power plant generation unit cost is around 1.61 Rs./kWh. Therefore above plant all day energy generation cost is 1.61 Rs./kWh. From system load details of figure 5 and Appendix B,
Required peak power saving energy = 50,000kWh
From Randenigla hydro power plant details and Appendix C, Power plant capacity of one unit = 63MW Full loading power of one unit for ½ hours = 31,000kWh Spinning reserve loading plant capacity = 82% Power output of 82% loading = 25,000kWh Both unit power output of 82% loading = 50,000kWh Randenigala hydro power generation cost = 1.61 Rs./kWh
Total cost of generation for ½ hours per day = 1.61x50,000 = Rs. 80,500.00
Wind turbine power generation cost
In this thesis did not calculate wind turbine cost in deeply due to this project duration is six month. But Sri Lanka has wind turbine life cycle cost. According to data of Appendix I, existing wind power generation unit cost was considered analyze the cost calculation.
From Appendix I, in year - 2013 existing wind power generation unit cost in Sri Lanka around 11.96 Rs./kWh.
There no of wind turbines average capacity = 935x3 = 2,805kW Wind turbines average energy production per day = 2,805x24 = 67,320kWh Wind power generation cost = 11.96 Rs./kWh Total cost of wind power generation per day = 11.96x67, 320 Rs. 805,147.00
46 Coal power generation cost
From Appendix I and CEB LTGEP year 2013 to 2032, at the movement base load or intermediate load energy cost in about 10.20 Rs./kWh in Sri Lanka. Also, in near future larger coal power plant will come into the base load or intermediate load in Sri Lanka, see Appendix F. Hence, in the off peak time, associated coal power plants provide energy for pump water from lower level Rantambe lower reservoir to upper level Randenigal.
Two no of water pump power capacity = 2,665kWh Required water pump energy consumption per day = 2,665x24 = 63,960kWh Total cost of water pump operating per day = 10.20x63, 960 Rs. 652,392.00
Option I;
In above chapter 3, concerning profitability of use a pumped storage system with electric energy product by wind turbine and use to drive pumps in pumping station.
Cost of Gas turbine peak loading energy for ½ hours per day = Rs. 1,600,000.00 Cost of Randenigala hydro power energy for ½ hours per day = Rs. 80,500.00 Cost of wind power energy per day = Rs. 805,147.00
Hence, peak power energy saving profit per day = Rs.1, 600,000-(80,500+805,147) Rs. 714,353.00
Peak power energy saving profit per year = Rs. 714,353.00x365 Rs. 260,738,845.00
Design is go through in option 1, Rs. 261 million per year is profitable of use this pumped storage system.
47 Option 2;
In above chapter 3, concerning profitability of use the excess power to pump the water in pumped storage plants.
Cost of Gas turbine peak loading energy for ½ hours per day = Rs. 1,600,000.00 Cost of Gas turbine peak loading energy for ½ hours per day = Rs. 80,500.00 Cost of use excess power for water pump operating per day = Rs.652, 392.00
Hence, peak power energy saving profit per day = Rs.1, 600,000-(80,500+652,392) Rs. 867,108.00
Peak power energy saving profit per day = Rs. 867,108.00x365 Rs. 316,494,420.00
Design is go through in option 2, Rs. 316 million per year is profitable of use this pumped storage system.
Hence, Rs.55 million per year is profitable design option 2 than design option 1.
48 6. Results and Discussion
At this time and in future of the world, wind power energy will be important for electricity power distribution. Future improvements in modern wind turbines has been cost reduction, more electric power generation and fast growth global market. It will large wind power and new system application.
Governments of Sri Lanka are more concerned about environments factors today and future also, many rural areas like that Central Province are priceless from the tourist point of view and some are seen as very good agricultural areas. Mahaweli scheme has two objective. That are provide watwer to irrigation and agriculture of primary one. Electrical power generation is second one. For this purpose, CEB and Mahaweli authority of Sri Lanka - MASL jointly decide water utilization of Mahaweli reservoir base. Both parties deliver maximum benefit to the country.
Largest reservoir in this complex is Randenigala, water is used to operate 2x62MW capacity turbine units and output water release to Rantambe pond. Rantambe pond can be regulated. Rantambe power station is operate 2x25MW capacity turbine unit and output water discharge to Minipe anicut. This water distribute to right bank and left nank Minipe canals to use downstream agriculture and irrigation purpose. But Rantambe power station cannot operate in regulated mode because water is used for downstream irrigation purposes. Therefore actual plant factor of Rantambe power station is 28% and Randenigala power station is 21.88%. Running plant factors for Rantambe power station 75-77% and for Randenigala power station 72% are shown in Appendix H.
The water management system of Rantambe reservoir is difficult due to Rantambe reservoir overflow dependent of Randenigala power generation and Uma-Oya river flow rate shown in Appendix A.
One of the ways of solving above problem is “peak saving methods” and Pumped storage power system is one of the options that Rantambe reservoir water can be utilized.
49 The purpose of pumped storage power plant is storing energy at electricity cost cheaper time and water release it quickly at peak hours. Demand for electrical changes throughout the day. In generally Sri Lankan electrical power at high peak of load curve is worked out between around 6.00pm 8.30pm as show in figure 23.
Source: CEB System Control
Figure 23- Normal Daily Load Curve of Sri Lanka Power System
According to the merit order generation method, generations are startup and run in minimum unit cost to maximum cost respectively. In Sri Lanka normally base load is supplied by hydro power, Intermediate load is supplied by part from hydro and low cost thermal, peak load is supplied by high cost thermal. Sometimes this order becomes different due to reasons like low water capacity of reservoirs etc. But basically this is correct.
In duration of 6.00pm and 8.30pm peak time power stations do not generate more power immediately. Therefore, manage the peak power to need power cuts around the country it can be all sort other trouble occur. Problem of in this situation is our country electricity power generated by fossil fuel plant also, as high cost thermal. Therefore this thesis is profitability assessment “peak time high cost thermal power generations saving” and Rantambe reservoir water utilized. This purpose pumped storage power plant can be use above situation.
50 The aim of this project is to peak power generations sheaving with pumped hydro power plant. Main objective this thesis use an economically analysis & design for a pumped storage system located at a Randenigala hydropower plant in Mahaweli complex area of Sri Lanka. The profitability analysis of a pumped storage system answered in two options:
Option – 1
In this case a wind pumped storage system uses wind turbines to produce electricity to drive the pumps. This is most common in wind pumped storage systems today.
In this system is few hours in peak time electricity produced with a Randenigala hydro turbine from the pumped water. In concerned above option had been selected 3MW Vestas V112 wind turbine case studies wise;
In case studies – 1, if one wind turbine has 112m rotor diameter, 9,852m2 swept area per turbine and 119m hub height producing electricity as calculated is 554kW power to pump when expected efficiency of the wind generator is about 95%. The efficiency in the motor is estimated centrifugal to be 90%. The gearbox is expected to have 95% efficiency and the estimated centrifugal pump efficiency is 73%. Calculated water flow rates 1.41m3/s but design water flow rate is 1.83m3/s. Therefore the calculated water flow rate for one electrical motor connected to a centrifugal pump if 554kW is unusable for pumping as shown in figure 15 with the head at a 40m height.
In case studies – 2, if considered two wind turbines, one turbine has 112m rotor diameter, 9,852m2 swept area per turbine and 119m hub height and total producing electricity is 1,108kW power to pump when the efficiency of each wind turbine generator are expected have 95% efficiency. The efficiency in the motor is 90%. The gearbox is having 95% efficiency and calculated centrifugal pump efficiency is 73%. Also, calculated water flow rate for 2.82m3/s and design water flow rate is 1.83m3/s. Therefore the calculated water flow rate for one electrical motor connected to a centrifugal pump if 1,108kW is usable for pumping as shown in figure 16 with the head at a 40m height. But analysis to power saving peak few hours for generate electrical power is required water to flow is 3.66m3/s for one day cycle.
51 Therefore cannot achieve to water flow is 3.66m3/s which is one unit as shown in figure 15. Also, two units are technically usable but economically unusable.
In case studies – 3, one turbine has 112m rotor diameter, 9,852m2 swept area per turbine and 119m hub height with three wind turbines has operation in parallel with bus bar an installed two separate gearbox and two separate motor is producing electricity power is 2,664kW on bus bar. This combination one gearbox, one mortar, one centrifugal pump and shaft are called one unit. The each wind turbine generator is expected have 95% efficiency. The efficiency in the each motor is 90%. The each gearbox is having 95% efficiency and calculated centrifugal pump efficiency is 73%. For one unit has calculated flow rate for one shaft driven pump if 720kW is usable for pumping water to a 40m height is 1.83m3/s. Therefore most suitable to uses two units for saving power for peak few hours for generate electrical power is required water to flow is 3.66m3/s. for one day cycle as shown in figure 17. Also, two pump units are technically feasible and economically usable.
In this project, consider night time in between 6.30pm to 7.00pm if peak saving for around half an hour and selected 100MW in system load side. Then calculate required average peak power saving energy of between times 6.30pm to 7.00pm is 50,000kWh.
This project duration is six month, therefore project scopes is limited and not considered wind turbine costs and pumped storage costs. Only considered existing life cycle cost of gas turbine plant, coal power plant, Randenigala hydro power plant and wind power plant. Therefore, assumptions, Wind turbine capital cost in covered under unit cost, calculated based on life cycle cost. Pump storage cost is neglected as comparing the option 1 and 2 where both will have the same cost. Pump and wind turbine construction, installation and commissioning cost are neglected due to above two reasons.
If above cost considered, very difficult to calculation due to market price of manufacturing and fuel, CIF values, and Tax etc., are change time to time. Therefore, the unit cost is was taken from the actual data for existing wind, hydro, coal & gas power plant in the country. It
52 was assumed that this will cover the operational variations of the system. Sensitivity analysis was not carried out as the actual unit cost data was used.
At the movement peak time high cost thermal power generation of Sri Lanka is exiting gas turbine power plant generation unit cost is around 32.00 Rs./kWh. Therefore cost of peak loading energy for ½ hours is around Rs.1, 600,000/=. Existing Randenigala hydro power plant generation unit cost is around 1.61Rs./kWh and required ½ hours generation cost is around Rs.80,500/=. In year - 2013, exiting wind power generation unit cost in Sri Lanka around 11.96 Rs./kWh.
Therefore, this unit cost concerned for calculation and total cost of 3MW Vestas V112 three wind turbine power generation all day Rs. 805,147/=. Therefore peak power energy saving profit per year Rs. 260,738,845/= According to above cost analysis and design is go through in option - 1, Rs. 261 million per year is profitable of use this pumped storage system.
Option – 2
In this case to use the excess electricity power from grid network to drive water pumps the water in pumped storage power plants. In near future, huge coal power plant will come into the base load or intermediate load in Sri Lanka. Hence, in the off peak time, the associated coal power plants provide energy for pump water lower level Rantambe to upper level Randenigala reservoir.
At the movement, off peak time associated base load or intermediate load with low cost thermal energy cost is about 10.20 Rs./kWh in Sri Lanka. Hence, total cost of water pump operating per day Rs. 652,392/=. Also, existing cost of peak loading energy for ½ hours is around Rs. 1,600,000/=. Existing Randenigala hydro power plant required ½ hours generation cost is around Rs. 80,500/=. So, Peak power energy saving profit per year Rs. 316,494,420/=. According to above cost analysis and design is go through in option 2, Rs. 316 million per year is profitable of this pumped storage system. Hence, Rs.55million per year is profitable to design option – 2 than design option – 1. The profitable assessment calculations show that it is profitable to build to build wind pump storage system for electricity production at existing hydropower plants.
53 Wind pump storage system should be installed more security. Hence, rainfall data observed fluctuation in Randenigala area in Central Province as shown in figure 20. But average wind speed from month of May to September very high. Therefore this situation is considered for typical arrangement of pumped storage system. Final typical design arrangement is concerning use pumped storage system with electric energy production by wind turbine and use to drive pump in pumping station system and to use the excess power to pump the water in pumped storage power plants. Also, export power from wind turbine can be used to connect national electricity network due to during southwest - monsoon season or pump system maintenance time.
In design system is combination of one gearbox, one motor, one centrifugal pump and shaft is called one unit and two pump units are technically feasible, economically usable and environmental friendly. Also to required power for transformer, circuit’s breakers and power bus bar to connected national electricity network for use excess power. Therefore most suitable to uses two units for saving peak few hours for generate electrical power is required water to flow is 3.66m3/s for one day cycle as figure 21.
According to the methodology only option 1 and option 2 is considered. In our country only 900MW coal power plant is available which is operated for the base load & day load which is not sufficient to run through the day. The cost comparison was made on coal, unit cost is Rs. 10.20. It is required to import coal in our country, and not environmentally friendly, but the wind was selected as it is sustainable & environmental friendly and government preference. Therefore, this thesis was not considered as a redundancies.
This thesis, selected by best wind turbines from table - 4 as Appendix E, Vestas V112 - 3MW and average output power 935kW. Also, in case study wise analysis most suitable wind plant and finally, analysis and selected maximum power is 3MW wind plants. So, wind turbines work at full capacity. This project is not expected to cover full peak, but keep peak power saving for around half an hour. According to appendix B, if consider night time in between 6.30pm to 7.00pm of peak power saving is around 100MW on system load. If the wind power is not available the system will run on grid power and if access power is generated by wind turbine, they are feed back to the grid as per figure 21.
54 7. Conclusion
The main reasons for profitable use of a wind pumped storage system for peak time electricity production in Sri Lanka are the high price of powerful thermal plant and the low electricity sale price.
The next step is to design a wind pumped storage system described in this thesis where one gearbox, one motor, one centrifugal pump and shaft is called one unit and two pump units required. Other accesses are power transformer, circuit’s breakers and power bus bar to connected national electricity network for possibility use excess power. Therefore most suitable to uses two units for high thermal generation cost saving in peak few hours for required water to flow is 3.66m3/s for one day cycle. Also, most important is to get a reliable price for a motor with a gearbox and a generator because with the installation cost of the equipment part in the profitability assessment. Other very important factors are the sale price for the electricity & average wind speed.
If design go through in option - 1, peak power energy saving profit per year Rs. 261 million per year is profitable of uses this pumped storage system. If design is go through in option – 2, peak power energy saving profit per year Rs. 316million per year is profitable of uses this pumped storage system. Hence, Rs. 55million per year is peak power energy saving profitable to design option – 2 than design option - 1 wind pumped storage systems.
So, conclusion is typical design arrangement for use pumped storage system with mainly electric energy product by wind turbine then use to drive water pump in pumping station system and possible tine use the excess power to drive water pump pumped storage power plants. Also, export power from wind turbine can be use to connect national electricity network due to during southwest - monsoon season or pump system maintenance time.
Producing energy with wind turbines is categorized renewable and a minimum impact on the environment has nearly non CO2 emission. Renewable energy like wind power plant is most suitable for connect to national grid in Sri Lanka. Therefore this pumped storage system is essential most reliable, technically feasible, economically usable and environmental friendly power generation system for our peak load operation.
55 References
[1] CEB, The web site is mandate by Ceylon Electricity Board - CEB, Sri Lanka. http://www.ceb.lk
[2] CEB, The web site is mandate by Ceylon Electricity Board, Department of Generation in Mahawali Complex, Sri Lanka. http://www.mahawelicomplex.lk/default.aspx
[3] ‘Swiss wind power data website’, this web site is mandate by federal department of environment, transport, energy and communication Swiss federal office of energy, Switzerland. http://wind-data.ch/index.php
[4] Kothari, D.P., Singal, K.C., Rakesh Ranjan, Book of Renewable Energy Sources and Emerging Technologies.
[5] CEB, Book of “LTGEP - Long Term Generation Expansion Plan 2013-2032” Prepared by CEB, Sri Lanka.
[6] SEASL, The web site is mandate by Sustainable Energy Authority of Sri Lanka. http://www.energy.gov.lk/
[7] Nesbitt, B. (2006). Hand book of “Pumps and Pumping”. Elsevier Science.
[8] P. Samaraweera, Book of Mahaweli Water Management to Maximize Benefit, Prepared by Mshaweli Authority of Sri Lanka.
[9] ‘ITT industrial goulds pump’ for pump selection system – PSS for selection of water pump available from http://www.gouldspumps.com
[10] Godfrey Boyle, Book of renewable energy power for Sustainable future, second edition of Oxford University.
[11] Bachelor of Technology degree programs text book in “Power System Planning” of the Open University of Sri Lanka.
[12] Christine Schoppe, ‘wind & pumped – hydro power storage’, department of operation research & financial engineering, Princeton university, June 2010.
56 [13] MTAP Wickramarathna, ‘planning of pump storage plant in Sri Lanka’, SLEMA journal, Vol 14, no.2, September 2011.
[14] CEB, “Ceylon Electricity Board Annual Report of 2013” Prepared by Ceylon Electricity Board, Sri Lanka.
[15] John S. Anagnostopoulos, Dimitris E Papantonis, ‘pumping station design for pumped storage wind hydro power plant’ school of mechanical engineering, National technical university of Athens, Heroon polytechniou9, 15780 Zografou, Athens, Greece.
[16] C Buenoa, JA Cartab, ‘wind powered pumped hydro storage system, a means of increasing penetation of renewable energy in Canary Islands’, department of mechanical engineering, university of Las Palmas de gran Canaria, Canaria Islands, Spain.
[17] JP Deane, BPO Gallacho, EJ Mckeogh, ‘Techno economic review of existing and new pumped hydro energy storage plant’, sustainable energy research group, department of civil and environmental engineering, university college cork, Cork, Ireland.
[18] M Kapsali, JK Kaldellis, ‘Combining hydro and variable wind power generation by means of pumped storage under economically viable terms’, Lab of soft energy applications and environmental protection, TEI of Piraeus, Athens, Greece.
57 Appendix A – System of Water Management in Mahaweli Authority of SL
Source; Mahaweli Authority of SL
58 Appendix B – Daily Load Profile of Sri Lanka
CEB - national system control generate daily load profile which record annual peak in every years. That is seen shape and load profile scenario last ten years. This system peak demand occur only short duration from 1900 hour to 2200 hour in daily. Also, it recorded maximum system peak load is 2,163MWin year 2011, while in year 2012 peak demand is 2,146.40MW.
Source: CEB LTGEP2013-2023
Source: CEB system control
59 Appendix C - Background of Randenigala and Rantambe Reservoir Data
C.1 Explanations for Randenigala power house, reservoir & dam
Source: CEB website
Reservoir data; Catchment area – 2,330sqkm Gross storage capacity – 816MCM and live storage capacity – 558MCM
Main dam site data; Dam length – 485m & dam height – 94m Crest elevation – 239mMSL & crest width – 10m & Maximum base width - 303m
Spill way data; Maximum capacity - 8,100m3/s Number of gate – 3 & type of gate – Taintor High of gate – 15.26m & with of gate – 16.7m Length of chute spillway – 232m
Generation & turbine data; Number of turbine & generates – 2 & type of turbine – Francis Volumetric flow rate in full capacity – 2x90m3/s Setting of turbine – 148.5mMSL Installed capacity – 2x63MW Annual energy generation firm – 428GWh (one million units) & secondary – 100GWh
60 C.2 Explanations for Rantambe power house, reservoir & dam
Source: CEB website
Reservoir data; Catchment area – 3,118sqkm Gross storage capacity – 21MCM Live storage capacity – 4.4MCM Surface at retention level – 152mMSL
Main dam site data; Dam length – 420m Dam height – 20m Crest elevation – 41.5m & crest length - 50m
Spill way data; Maximum capacity – 10,235m3/s Number of gate – 1 & type of gate – Taintor High of gate – 16.21m & with of gate – 16m
Tunnel bottom & Irrigation outlet data; Number of turbine & generates – 2 & type of turbine – Francis Volumetric flow rate in full capacity – 2x90m3/s Setting of turbine – 148.5mMSL Installed capacity – 2x24.5MW Annual energy generation firm – 180GWh (one million units) & secondary – 73GWh
61 Appendix D - Background of Water Pump
To select of the Goulds 3172 pump the software Pump Selection System – PSS from Goulds Pumps was used (ITT, 2009).
62
When pressed “Search Using Selection Criteria“, the software searched for a pump which matched the criteria. One pump was found, Goulds 3175 20x24-28H.
Source: http://www.gouldspumps.com
The Goulds pump of type 3175, size 20x24-28H and speed 890 RPM has efficiency of 73%. The pump uses 991 kW when pumping water up to a height of 40m, at a flow rate 1.83m3/s.
63 Appendix E - Background of Electricity Generation from Wind Power
E.1 Wind energy extraction
The air kinetic energy of unit mass of air fluid given below,
2 Ek = m v
Power per unit mass air flow would be,
2 P = Ek = v
= ρ V = ρ Av
Total available power in air flow is,
3 P = ρ Av
Where; P – Air flow power (W) ρ – Density of air (kg/m3) V – Velocity of air (m/s) A – Area of flow (m2)
64 E.2 Wind profile
Ground level wind speed is strongly broken because obstacle and surface roughness. But height above ground level is wind speed approximate 5km above ground not turbulent. It level wind no longer influenced by surface between these two extremes wind speed change with height. It is mean called vertical wind shear. In flat terrain with neutrally stratified atmosphere at logarithmic wind profile which good estimation for vertical wind shear as given below formula,
Where;
V1 – reference wind speed @ h1 height with ground level
V2 – wind speed @ h2 height with ground level
Z0 – roughness length as refer below table
Roughens with class & length
Roughness Roughness Type of Land cover class length Z0 (m)
0 0.0002 Water surfaces. Ex. seas and Lakes 0.5 0.0024 Open terrain with smooth surface. Ex. concrete, airport runways, mown grass etc. 1 0.03 Open agricultural land without fences and hedges; maybe some far apart buildings and very 1.5 0.055 Agricultural land with a few buildings and 8 m high hedges separated by more than 1 km 2 0.1 Agricultural land with a few buildings and 8 m high hedges separated by approx. 500 m 2.5 0.2 Agricultural land with many trees, bushes and plants, or 8 m high hedges separated by approx. 3 0.4 Towns, villages, agricultural land with many or high hedges, forests and very rough and uneven 3.5 0.6 Large towns with high buildings 4 1.6 Large cities with high buildings and skyscrapers
Source: http://wind-data.ch/index.php
65 Source: http://wind-datas.ch/index.php
E.3 Explanations for the wind energy potential
The estimate wind energy potential is based on below methods, 1. Wind data of specific sit use frequency distribution 2. Type of wind energy generation 3. Weibull factors of wind data
Wind data base; Annually energy generation, specific site base and other factors use calculate characteristics if wind energy generation.
Power law index α;
66 V1, V2 – wind speed at level H1& H2respectively
Wind power density Pd;
Based on wind energy generator;
Machine capacity factor; define as the ratio of average power output of a turbine during a month or a year to the rated power output. Utilization factor of capacity; define as ratio of actual energy generated by theoretical energy generated.
Based on weibull factor;
Wind speed is naturally varies with constantly. For predict wind turbine production which know exactly how often wind blow and strong. Normally wind measure with anemometer. Also, mean wind speed record with every 10minutes. This data can be sorted in to 1m/s wind speed classes in each. Energy contain in certain site of wind can be expressed by it frequency distribution. Weibull distribution is often good approximately for wind speed distribution witch can be calculate by below formula,
A – Weibull scale perimeter (m/s) it can be measure with characteristic of wind speed of distribution. Also, A is proportional to mean wind speed. k – Weibull parameter which specified shape of Weibull distribution with take on value between 1 and 3. So, small value of k signified very variable wind while wind are characteristic by large k. this project is estimate of wind energy potential is based on Weibull distribution method for use to power calculator. This project result as given below,
67 Source: http://wind-data.ch/index.php
E.4 Explanations for stranded power curves of wind turbine
Ideal and optimum wind power profile (output curve) for standard wind turbine as given below,
Wind speed at cut-in; It is mean wind speed witch wind turbine start to operate. Wind speed at rated; It is mean wind speed which wind turbine attain to give maximum output.
68 Wind speed at cut out; It is mean wind speed which turbine design to shut down. It is prevent damage from high winds.
E.5 Explanations for suitable power curves of wind turbine
Source: http://wind-data.ch/index.php
In this project, different turbine types and estimate of power production by done power calculator. Also, assumed turbine availability – 100% witch no losses due to down time, transformer losses and park effects.
1 capacity factor – ratio between annual production & maximum technical possible production of wind turbine. It should be note, wind turbine is not principle design for optimal capacity factor. But generate electricity as possible at certain wind speed. It capacity factor is 30% to 40% for very high coastal area.
2 full load hour represent capacity factor and it theoretical number of house of wind turbine have run at full load. It order to product annual yield. It has equivalent to the capacity factor. * Number of hour in year = 8,760hours.
3 Operating hour mean expected number of hours in year by wind turbine production electricity. It is yearly total 8,760hours.
69 E.6 Power curves of an international turbine manufacturer
Source: http://wind-data.ch/index.php
70 Appendix F - Background of Power System Capacity Distribution
F.1 Comparison of energy production in 2011, 2012 and 2013
Source: http://www.mahawelicomplex.lk/default.aspx
F.2 Energy production of Mahaweli complex from 1998 to 2011
71 F.3 Energy production of Randenigala & Rantabe power station from 1998 to 2011
72
Source: http://www.mahawelicomplex.lk/default.aspx
F.4 Energy mix – over next 20 years in Sri Lanka
Source: CEB LTGEP2013-2023
73 F.5 Fuel requirement over next 20 years in Sri Lanka
Source: CEB LTGEP2013-2023
According to above graph, in near future coal power will be taking of the base load or intermediate load of Sri Lanka electricity power system.
F.6 Peak load capacity over next 20 years in Sri Lanka
Source: CEB LTGEP2013-2023
74 Appendix G - Background of Rainfall and Wind Speed
G.1 Wind speeds data analysis in Abewela area
Max Average Month (m/s) (m/s) January 9.87 3.94 February 11.25 4.09 March 9.09 3.74 April 7.68 3.03 May 18.19 8.42 June 23.05 14.69 July 23.54 11.31 August 22.55 12.33 September 25.51 9.04 October 24.09 7.92 November 17.71 4.41 December 18.68 4.35 Mean 17.60 7.27
Source: Sustainable Energy Authority of Sri Lanka
75 G.2 Wind speed and rainfall data analysis
Wind Speed Rainfall Year Max_wind speed Aver._wind speed Aver._rainfall 2013 (m/s) (m/s) (mm) January 9.87 3.94 117.9 February 11.25 4.09 167.6 March 9.09 3.74 30.0 April 7.68 3.03 127.9 May 18.19 8.42 1.5 June 23.05 14.69 0.0 July 23.54 11.31 38.5 August 22.55 12.33 4.9 September 25.51 9.04 31.7 October 24.09 7.92 263.8 November 17.71 4.41 193.0 December 18.68 4.35 569.3
Source: Sustainable Energy Authority of Sri Lanka
76 Appendix H - Background of Existing Power Plants
H.1 Plant factor
Capacity factor or plant factor is the mean ratio of actual energy output over total period of operation output, if it had operated at full load (name plate capacity) the entire time.
Plant factor depend on type of power plant. It can be calculate as below formula,
Plant factor = Actual energy production during normal period Potential energy production during period
H.2 Plant factor – actual
Calculated plant factor – actual are all grid connected power plant in Sri Lanka, during year 2013 listed as below,
CEB Hydro
CEB & IPP Thermal
Source: CEB LTGEP 2013-2032
77 H.3 Plant Factor - Running
Generation unit running plant factor mean ratio of actual energy output of generation unit over period of time to it is potential output. It is shows the extent to which generation unit has been operated, when they are running out of it normal capacity. Therefore, calculated running plant factor of CEB own generation units in year 2013 as listed below,
Source: CEB – LTGEP 2013-2032
78 Appendix I - Background on Electricity Generation Cost of Power Plants
I.1 Hydro power generation unit cost station wise - Year 2013
Source: CEB website, http://www.mahawelicomplex.lk/default.aspx
According to the above table and graph in year of 2013 is Randenigala hydro power station generation unit cost is 1.61 Rs. /kWh.
79 I.2 Wind power generation unit cost - Year 2013
Cost tariff estimation from 1996 to 2013 in Sri Lanka
Source: CEB website, http://www.ceb.lk
According to the above table and consider in year - 2013 is wind power generation unit cost in Sri Lanka around 11.96 Rs. /kWh.
80 I.3 Thermal power generation unit cost - Year 2013
Specific cost of selected power plant – Sri Lanka as shows below,
Specific cost – thermal power plants [USCts/kWh] or [LKR/kWh]
Source: CEB LTGEP 2013-2032
According to the above table thermal power plant generation unit cost as follows,
According to the Appendix H, actual plant factor of 300MW Puttalam coal power plant is 60.68% with it is generation unit cost is around 10.20 Rs. /kWh.
According to the Appendix H, actual plant factor of 105MW Kalanitissa gas turbine power plants is 47.90% with it is generation unit cost is around 32.00 Rs. /kWh.
81