Concentrated Solar Power (CSP)

Transcription

1 Higher Institute for Applied Science and Technology Electronic and Mechanical Systems Department Fourth Year Concentrated Solar Power (CSP) Submitted by Ahmad Alalewi Supervisors Scientific Supervisor: Eng. Mahjoub DAHAIR Language Supervisor Mr. Fahmi ALAMAREEN Organizer Supervisor Dr. Adel ALKAFRI 10/3/2014

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3 For My Mother and Father

4 Acknowledgments I am grateful to the department of Electronic and Mechanical Systems, HIAST Damascus for giving me the opportunity to conduct this paper, which is an integral part of the curriculum in Control Systems Engineering. I would like to take this opportunity to express heartfelt gratitude for my scientific supervisor Eng. Mahjoub DAHAIR, who provided me with valuable inputs at various stages of this paper execution. I would also like to acknowledge the support of every individual who assisted me in making this paper a success, and I would like to thank Dr. Adel ALKAFRI, the organizer supervisor, for his guidance, support and direction without which, paper and presentation would not have taken shape. I am also thankful to the language supervisor Mr. Fahmi ALAMAREEN, for helping me. In addition, I wish to thank Dr. Mohamed DIB for his notes and the work that did it to review this paper.

5 Table of Contents Acknowledgments... iv List of Figures... vi List of Tables... vii List of abbreviations... viii List of equations... viii Abstract... 1 Introduction Definition The importance of CSP CSP plant site selection Components of a CSP Power Plant Solar Field Mirrors or reflectors the Receiver Pump system for the HTF Collector balance of system Thermal Energy Storage System The two-tank direct system Two-tank indirect system Single-tank thermocline system Power Block Power Cycles Fossil-Fired (Hybrid) Backup Wet and Dry Cooling Technology and Energy Yield Parabolic trough collectors State of the technology Case Study Solar tower (or power tower or central receiver) State of the technology Case Study Linear Fresnel State of the technology v

6 5.3.2 Case Study Dish State of the technology Summary and comparison of the CSP technologies Annual energy yield Capacity factor Land requirement Water requirement Applications of CSP Electricity transmission Cost of CSP CSP in Syria Introduction Syria thermally Conclusion Works Cited List of Figures Figure 1: Potential sites for CSP with respect to solar irradiation levels. Source: Solar Millennium AGPale yellow Suitable. Bright yellow Good. Orange Outstanding Figure 2 : Scheme for the components of CSP... 5 Figure 3 : one type of Solar Field. Source: 5 Figure 4: Types of reflectors from left to right 1-flat reflector 2-parabolic 3-dish. Source: 6 Figure 5: Receivers from left to right 1- long pipe 2-top of tower 3- concentrating point... 6 Figure 6: Andasol thermal storage tanks. Source: Solar Millennium AG... 9 Figure 7: A single-tank thermocline thermal... 9 Figure 8: Physical layout of the four main devices used in the Rankine cycle Figure 9: Number (left) and capacity in MW (right) of CSP plants of each technology in operation as in 2011, Source: SolarPaces, NREL, CSP plant developer and owner websites Figure 10: Operation of a parabolic trough. Source: RENAC Figure 11: Aerial view of Andasol 1. Source: Solar Millennium AG Figure 12: A parabolic trough Andasol Figure 13: Simplified scheme of parabolic trough plant with molten salt storage tanks. Source: 14 Figure 14: Operation of a solar tower. Source: 15 Figure 15: PS20 plant under construction with PS10 in the background. Source: Abengoa Solar vi

7 Figure 16: Operation of a Linear Fresnel collector. Source: Novatec Solar Figure 17: Linear Fresnel collector array, 1.4MW PE1 plant in Murcia, Spain. Source: Novatec Solar Figure 18: Operation of a dish collector. The dish tracks the sun throughout the day. Source: RENAC Figure 19: Dish, Ben Gurion National Solar Energy Center. Source: RENACP Figure 20: Investment cost breakdown for a 50MW parabolic trough CSP plant with 7 hours storage. Source: CSP Technology Roadmap 2010, International Energy Agency ( 25 Figure 21: Projected evolution of the levelised electricity cost from CSP plants to 2050, in USD/MWh, under two different direct normal irradiance (DNI) levels in kwh/m2year. Source: Technology Roadmap, Concentrating Solar Power, International Energy Agency, Figure 22: Syria thermally List of Tables Table 1: Raw materials, sub-components and components of heat transfer fluids which carry thermal energy from the collector to the storage unit 7 Table 2: Materials, sub-components and components required to make Solar Collector Assembly (SCA) 8 Table 3: Raw materials, components and sub components in thermal storage system 8 Table 4: Raw materials, sub-components and components of power block and cooling system 12 Table 5: Project information for Andasol 1. Source: Solar Paces, NREL, CSP plant developer and owner websites 15 Table 6: Project information for PS10. Source: SolarPaces, NREL, CSP plant developer and owner websites 16 Table 7: Project information for PE1. Source: SolarPaces, NREL, CSP plant developer and owner websites 19 Table 8: Annual solar-to-electric efficiencies of the four main CSP technologies. 22 Table 9: Capacity factors for the four main CSP technologies. Information on Linear Fresnel from Project Proposal for a CLFR Solar Thermal Plant in the Hunter Valley 22 Table 10: Land use efficiencies for the four main CSP technologies. 23 Table 11: Water requirements for the four main CSP technologies. 24 Table 12: Investment costs for three of the earliest completed CSP installations. Source: SolarPaces, NREL, CSP plant developer and owner websites. 25 vii

8 List of abbreviations CSP HTF HCE LOC SCA TES SEGS ORC LFR CLFR DSG ISCC SES Concentrated Solar Power Heat Transfer Fluid Heat Collection Element Local Controller Solar Collector Assembly Thermal Energy Storage Solar Electric Generating System Organic Rankine cycles Linear Fresnel Reflectors Compact Linear Fresnel Reflectors Direct Steam Generation Integrated Solar Combined Cycle Stirling Energy Systems List of equations Equation 1:The amount of electrical energy Equation 2: the annual capacity factor Equation 3: the land use efficiencies viii

9 Abstract Power is the most important thing for the world. All of us need power (like electricity or fuel). Our dream is to produce clean power which does not cost a lot. In this paper, we present the sun as a useful source to produce clean power. You will find that CSP is the way that produces power in a reasonable cost. What is it? And what are the main blocks? This paper will answer all these questions by explaining the main concept of this system and its functioning method without going into technical details. After reading this paper, the reader will have good knowledge about CSP, about the most possible configurations, and the feasibility of implementing CSP system in Syria. 1

10 Introduction Over the past years, power was - and still is - the main concern of humanity. From the very beginning of this world, humans tried to convert power in this universe from one type to another. We can consider the discovery of fire as the historic transition. Fire is the transition that used the chemical energy stored in the burned material to generate new power, for example, to heat food. The problem started when human s population increased. The planet started facing pollution and global warming, mainly because of burning fossil fuels. Fossil fuels are considered to be a good example of non-renewable energy source. Non-renewable energy sources are available on earth in limited quantities and will eventually be depleted. Coal, gas and oil are non-renewable because they need specific conditions and millions of years to be produced. So, we can find the importance of using new sources that can be replenished in a short period of time. Firstly, we generally define CSP system, then we talk about its importance and what the best countries for this technology are. After that, we move to name the main components in this system. At the end, we find information about some technologies and applications in addition to the cost of CSP, in the conclusion we summarize all the preceding concepts. 2

11 1- Definition Concentrated Solar Power, CSP for short, is a system that is based on concentrating the solar radiation onto a small area to get high temperatures, typically, in the range of This thermal energy is converted to electricity via steam or gas turbines. 2- The importance of CSP CSP technology is recently becoming globally interesting as one of the means to meet increasing demands using solar energy. Huge amount of money have been invested internationally in developing this technology. Since 2005, systems are being installed commercially. However, the various technologies in use have not yet been optimized, either technically or economically and much experience is still needed to be gathered before CSP could be considered a reliable, low-cost source of electricity. Some primary findings from the CSP Markets Report 2010 published by CSP Today are: [1] By 2015 CSP will be worth up to 70$ billion in the US alone. There are 921 MW of CSP plants installed worldwide, 93% of which are parabolic trough systems (see Section 5.1). Alternative uses of CSP such as hybridization with existing power plants and desalination are emerging across new CSP markets. 3- CSP plant site selection The most suitable sites for CSP with respect to solar irradiation are the world s deserts. The best solar resource in the world is in the deserts of South Africa and Chile where annual direct solar irradiation reaches 3000kWh/m 2 per year. Southern Spain and the North African coast have kWh/m 2 per year. South West US and Upper Egypt have kWh/m 2 per year. France, Italy and Portugal have even lower levels. The global technical potential of CSP has been estimated at almost 3,000,000TWh/year which means 166 times higher than the current world energy consumption of 18,000TWh/year. [2] Other important factors in CSP site selection are: 1. Geographical factors - Availability of flat, unpopulated land that is not environmentally sensitive or already being used. - Availability of large amounts of water for cooling. This is discussed in more detail in Section Distance to the electricity grid. - Road access. - Potential climate risks. 3

12 Figure 1: Potential sites for CSP with respect to solar irradiation levels. Source: Solar Millennium AGPale yellow Suitable. Bright yellow Good. Orange Outstanding. 2. Political and economic factors - Political stability of region. - Cost of land leasing. - Existence of government incentive schemes. - Investment freedom. - Existence of a power purchase agreement. 4- Components of a CSP Power Plant In figure 2 we can see scheme for the components of a CSP power plant. This scheme consists of three main stages: 1. Solar Field; where we can concentrating the solar radiation onto the receiver. 2. Thermal Energy Storage System; where we can storing the thermal energy. 3. Power Block; where we can convert the thermal energy to electricity. We will explain each stage in more details through the next sections. 4

13 4-1- Solar Field Figure 2 : Scheme for the components of CSP The solar field is the main part in a CSP system. It consists of many reflectors, which reflect and collect the sun radiation in a specific area called heat collection element. This produces high temperature which in turn moves through a heat transfer fluid (HTF). The HTF is warmed by the sunlight to more than 400 C, and then flows to the power block or the thermal energy storage system, depending on the mode of operation. Figure 3 : one type of Solar Field. Source: 5

14 In other words, the main parts of the Solar Field are: Mirrors or reflectors Linear receiver or heat collection element Pump system for the HTF Collector balance of system Mirrors or reflectors There are many types of mirrors and reflectors. They can be classified to: Flat mirrors Parabolic-shaped mirrors parabolic dishes-shaped mirrors Figure 4: Types of reflectors from left to right 1-flat reflector 2-parabolic 3-dish. Source: Reflectors are made of various materials. For example, glass, aluminum (reflective films laminated onto aluminum sheets) etc. you need to consider in choosing the materials to the specular energy reflectance, the expected useful life, excessive corrosion and UV degradation. In addition to materials, control of direction of these mirrors need to be considered. [3] the Receiver After the sun rays are reflected by the mirrors, we need to collect them. Linear receiver or heat collection element HCE is one of the primary reasons for the high efficiency of the CSP system. The receiver heats a special heat transfer fluid as it circulates through the receiver. It is made up of stainless steel, special solar-selective absorber surface surrounded by an anti-reflective glass tube. The shape and material of the receiver depend on the way of concentrating solar power. An HCE may be a long pipe, a small area on top of a tower or a specific point. We will discuss where each type is used in section 5. Figure 5: Receivers from left to right 1- long pipe 2-top of tower 3- concentrating point 6

15 Pump system for the HTF After reflecting and concentrating sun rays in a specific place called HCE, storing and transferring heat energy is needed in order to generate electricity. Heat Transfer Fluid HTF and pumps are used. Special technical applications are important for CSP, because it is a big challenge to manufacture pumps that are able to handle hot fluids, such as the heat transfer medium, of about 500. In the next table, we illustrate the materials, components and sub-components that are used in manufacturing HTF. Final Components Heat Transfer System Components Receiver Receiver interconnect HTF Oils HTF Piping System Sub-Components Photo Selective Coating Glass Tube Ball Joints hose Salts,Water,Oi ls Piping Materials Chemical coatings Polymers Steel Aluminum Rubber Steel Table 1: Raw materials, sub-components and components of heat transfer fluids which carry thermal energy from the collector to the storage unit Collector balance of system Many other essential components make up the balance of system in the solar field, including: Pylons and foundations - The pylons support the collector structure. They allow the collector to rotate and track the sun. Drive - Each solar collector assembly includes one drive. The drive positions the collector to track the sun during the day. It can be either a standard motor and gear box configuration or can use a hydraulic drive system. Controls - Each solar collector assembly has its own local controller (LOC) that controls the tracking of the collector. It communicates with a supervisory computer in the power plant control building to know when to start tracking the sun or when to stop tracking at the end of the day. Collector-interconnect It is used for connecting the receiver to header piping and between two adjacent collectors. Earlier insulated flexible hoses were used but now new ball joint assembly is developed to replace the flex hose. Materials, sub-components and components required to make Solar Collector Assembly (SCA) are illustrated in table 2: 7

16 Final Components SCA Components Parabolic Trough Reflecting Surface Tracking System Sub-Components Truss Torque Tube/Box Parabolic Mirror Reflecting Film Hydraulic Cylinders Gears Electronics Materials Aluminum Steel Silica/Sand Chemical coatings Polymers Steel Table 2: Materials, sub-components and components required to make Solar Collector Assembly (SCA) 4-2- Thermal Energy Storage System The big question is what happens during night time. How the power plant will generate electricity. Surely, we need to store thermal energy. Energy storage is essential in order to make CSP truly competitive with fossil fuel based electricity generators. CSP electricity should meet demand at night as well as at peak times. A considerable value can be added to a CSP installation if it includes a storage utility. The storage utility should meet the demand for few hours. State-of-the-art in energy storage using liquid molten salt is currently the most cost-efficient storage option and is becoming increasingly predictable and commercially reliable. The most commonly used molten salt mixture consists of 60% sodium nitrate, 40% potassium nitrate. The availability of efficient and low-cost thermal storage is important for the long-term cost reduction of CSP technology, and significantly increases potential market opportunities. Several thermal energy storage (TES) technologies have been tested and implemented. These include: The two-tank direct system Two-tank indirect system Single-tank thermocline system Final Components Thermal Storage Components Molten Salt Storage Tanks Heat Exchangers Sub-Components Salts Oils Metal Structures Hydraulic Cylinders Gears Electronics Materials Steel Steel Table 3: Raw materials, components and sub components in thermal storage system The two-tank direct system This system was used in early CSP power plants. The generated energy is stored in the same fluid used to collect energy. The fluid is stored in two tanks one at high temperature and the other at low temperature. Fluid from the low-temperature tank flows through the solar collector or receiver, 8

17 where solar energy heats it to a high temperature. The liquid flows to the high-temperature tank for storage. Mineral oil is used as the heat-transfer and storage fluid Two-tank indirect system Two-tank indirect systems function in the same way as two-tank direct systems, but different fluids are used for heat-transfer and storage. Organic oil is used as the heat-transfer fluid, and molten salt is used as the storage fluid. The indirect system requires an extra heat exchanger, which adds cost to the system. In figure 6, we see Andasol thermal storage which is based on tow-tank indirect system configuration. The two tanks contain 28,500 tonnes of molten salts providing 1100MWh or 7.5hours of storage Single-tank thermocline system Figure 6: Andasol thermal storage tanks. Source: Solar Millennium AG Single-tank thermocline systems store thermal energy in a solid medium, most commonly silica sand, located in a single tank. At any time during operation, a portion of the medium is at high temperature, and a portion is at low temperature. The hot- and coldtemperature regions are separated by a temperature gradient or thermocline. High-temperature heat-transfer fluid flows into the top of the thermocline and exits the bottom at low temperature. This process moves the thermocline downward and adds thermal energy to the system for storage. Reversing the flow moves the thermocline upward and removes thermal energy from the system to generate steam and electricity. Using a solid storage medium, and using only one tank, reduces the cost of this system relative to two-tank systems. The only entirely proven and commercially employed technology is the two-tank molten salt system. Figure 7: A single-tank thermocline thermal 4-3- Power Block In this section, we talk about using thermal energy to generate electricity. Simply, hot HTF is transported to the power block, where it is used to boil water to generate steam for use in a conventional steam generator to produce electricity. 9

18 The power block is the part where the thermal energy from the collector field is converted into electrical energy. The power block uses the same technology as conventional fossil fuel power stations. Existing CSP plants all use steam turbine technology to generate electricity. A steam turbine can operate in a temperature range of minimum 100 (the boiling point of water) and maximum around 655 (the practical limit for the steel alloy turbine materials). The turbine efficiency is greater at higher temperatures. The fixed upper efficiency is 35-42%. Modern fossil fuel steam turbine plants operate at around 600, and therefore we can achieve the maximum possible efficiency of 42%. CSP power plant technologies include: Power cycles - Steam Rankine - Organic Rankine - Combined Fossil-fired (hybrid) backup Wet and dry cooling Power Cycles There are a number of different power cycles that can be used for CSP power plants. There are also a number of options for how to integrate solar energy into the power cycle. Steam Rankine: most new projects of the solar electric generating system (SEGS) plants are designed to use steam Rankine power cycles. The power cycle uses a solar steam generator in place of the conventional boiler fired by natural gas, coal, or waste heat from nuclear fission. Power cycle consists of the following components: A surface condenser Multiple low-pressure and high-pressure feed water heaters Deaerator (a device that is used for the removal of oxygen and other dissolved gases from the feedwater to steam-generating boilers) Wet cooling towers. Figure 8: Physical layout of the four main devices used in the Rankine cycle There are four processes in the Rankine cycle. These states are identified by numbers (in brown) in the above figure 8. Process 1-2: The working fluid is pumped from low to high pressure. As the fluid is a liquid at this stage the pump requires little input energy. 10

19 Process 2-3: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapor. The input energy required can be easily calculated using enthalpy-entropy chart. Process 3-4: The dry saturated vapor expands through a turbine, generating power. This decreases the temperature and pressure of the vapor, and some condensation may occur. The output in this process can be easily calculated using the Enthalpy-entropy chart. Process 4-1: The wet vapor then enters a condenser where it is condensed at a constant pressure to become a saturated liquid. In an ideal Rankine cycle the pump and turbine would be isentropic, i.e., the pump and turbine would generate no entropy and hence maximize the network output. Processes 1-2 and 3-4 would be represented by vertical lines on the figure8 and more closely resemble that of the Carnot cycle. The Rankine cycle shown here prevents the vapor ending up in the superheat region after the expansion in the turbine, which reduces the energy removed by the condensers. Organic Rankine cycles (ORCs): use an organic fluid such as butane or pentane instead of water, like a steam Rankine cycle. Combined Cycle Power Plants: Some plants now integrate solar fields with an alternate energy source such as gas turbines to ensure more constant production and sometimes even 24-hours steady operation Fossil-Fired (Hybrid) Backup Most existing parabolic trough power plants have hybrid backup capability. Because parabolic trough power plants use conventional power cycle technologies. Fossil-fired boilers or heaters usually can be integrated to enable power plant operation at full-rated output during periods of low solar radiation, such as on overcast days and at night Wet and Dry Cooling The process of generating electricity from a CSP plant requires a large amount of cooling. This cooling process can either use water for evaporative (wet) cooling, or air for dry cooling. The aircooling condenser used in dry cooling eliminates 90% of the water requirement. The downside is that the performance of the air-cooling condenser drops significantly on hot days, forcing the plant to operate at reduced capacity and efficiency. The capital cost of dry cooling has previously been placed at 2.5 times that of wet cooling but the operational cost is lower because the water treatment and discharge of waste water cost is lower. The capital cost of dry cooling is unlikely to come down significantly because the majority of the cost is in materials a MW CSP plant cooling tower can occupy as much land as a football field. Hybrid wet and dry-cooling options are now being developed where wet-cooling contributes for only a few hundred hours per year on the hottest days 1. Historically, parabolic trough power plants have used wet cooling towers. But now they can be designed to use dry cooling technology for reducing water consumption. Utilization of dry cooling usually only requires a modest increase in electricity cost. 1 See CSP cooling options: Workarounds for water scarcity, Executive Viewpoint interview from CSP Today. 11

20 Final Components Power Block Components Heat Exchangers Steam Generator Steam Network Turbine Generator Cooling Towers Sub-Components Salts Oils Piping Structures Blading Power Electronics Towers Materials Steel Composites Water Table 4: Raw materials, sub-components and components of power block and cooling system 5- Technology and Energy Yield The four main CSP technologies being developed are parabolic trough, solar tower (or power tower), Linear Fresnel reflector, and parabolic dish. The majority of existing installations are parabolic trough. Figure 9 shows the number of existing commercial installations for each technology and the respective total capacity in megawatts MW. We can see the existing installations of parabolic trough has respective total capacity higher than the rest of technologies, because the efficient of parabolic trough is proven commercially. Figure 9: Number (left) and capacity in MW (right) of CSP plants of each technology in operation as in 2011, Source: SolarPaces, NREL, CSP plant developer and owner websites 12

21 5.1 Parabolic trough collectors Figure 10: Operation of a parabolic trough. Source: RENAC Solar radiation is reflected from the trough onto an evacuated tube receiver extending along of the trough. Inside the receiver, there is a heat transfer fluid which transfers the heat to water via a heat exchanger to produce superheated steam which drives a conventional steam turbine to generate electricity. For lower temperature applications less than 200 the heat transfer fluid is often a mix of demineralized water with ethylene-glycol. For higher temperature applications of synthetic oils or molten salts are used. The troughs track the sun as it moves across the sky (see figure 10 above) State of the technology Parabolic trough plants with a combined capacity of more than 850MW have been installed. Existing plants range in size from 14-80MW, and are located mainly in Spain and the US. Advantages: Parabolic trough systems are the most mature, and thus commercially viable, of the CSP technologies. The net plant efficiency of 15% has been commercially proven. Investment and operating costs have been commercially proven. Systems are modular. Systems have a good land-use factor. Systems have lower materials demand. Hybrid concept has been proven. Storage capability. Disadvantages: High thermal losses in the parabolic trough array. An ideal heat transfer medium for use in parabolic trough arrays has not yet been found. This can cause problems because the pipe running through the array. 13

22 5.1.2 Case Study Figure 11: Aerial view of Andasol 1. Source: Solar Millennium AG Figure 12: A parabolic trough Andasol 1 Andasol 1 & 2 parabolic trough plants, located near Granada in Andalucia, Spain, were developed by the ACS-Cobra Group. Andasol 1 has been in operation since 2008 and Andasol 2 since Both have an electricity generation capacity of 50MW. The heat transfer fluid used in the parabolic trough array is a mixture of biphenyl and diphenyl oxide. This is currently the most common heat transfer fluid used in parabolic trough arrays. Its operating temperature range is Below 12 it freezes and above 400 both the biphenyl and diphenyl oxide begin to break down. These reactions produce hydrogen which passes into the evacuated glass tube disrupting the vacuum and thus reducing its effectiveness at keeping the heat in. Therefore the plant temperature must stay below 400 at all times. This temperature limitation restricts the efficiency of converting heat into electricity. A plant able to run at, say, 500 would be more efficient. The plants also include thermal storage (see figure 13) in the form of two large tanks with a capacity of 28,500 tones containing molten salt (a mixture of 60% sodium nitrate and 40% potassium nitrate). The molten salt can operate in the temperature range These tanks can provide 1100MWh or 7.5hours of storage so that electricity continue to be generated during night time. Figure 13: Simplified scheme of parabolic trough plant with molten salt storage tanks. Source: Project name Andasol 1 Location Granada, Spain Capacity 50 MW Land area 200 ha 14

23 Electricity generation (predicted) Solar array maximum temperature 393 Thermal storage capacity Thermal storage material Type of cooling Heat transfer fluid Investment cost Specific investment costs MWh/year 7.5 hours molten salts wet cooling tower biphenyl-diphenyl oxide 300 Million 0.27 /kwh Table 5: Project information for Andasol 1. Source: Solar Paces, NREL, CSP plant developer and owner websites 5.2 Solar tower (or power tower or central receiver) In figure 14, we can see the solar radiation is reflected from heliostats (large steel reflectors) onto a receiver (heat exchanger) at the top of the solar tower. The heat transfer medium in the receiver may be water/steam, molten salts or air. The heat transfer medium transfers the heat to the rest of the plant, usually to a water store where high temperature steam is produced to drive a steam generator. Pressurized gas or air at around 1000 can also be used directly to drive very efficient gas turbines in modern gas and steam combined cycles. Figure 14: Operation of a solar tower. Source: State of the technology Solar towers are past the proof-of-concept stage of development and, although they are less mature than parabolic trough technology, they are on the verge of commercialization. Operating experience was gained in the 1980s and 1990s with the Solar One and Solar Two 10MW facilities in California. Both of these have since been decommissioned. The most current experience is from several new solar tower pilot projects at the Plataforma Solar de Almeria in Spain. These are all steam receiver systems. A number of molten salt towers are under development by Solucar, BrightSource and esolar. Molten salt towers offer the potential for very low-cost storage so that solar electricity can meet peak demands and have a high capacity factor (ca. 70%). 15

24 Advantages: Good mid-term prospects for high efficiencies due to the potential for achieving higher temperatures of over Better suited for dry cooling than parabolic troughs. Can be installed on hilly sites. Disadvantages: Performance, and investment and operating costs have not yet been commercially proven Case Study The world s first solar tower plant, PS10, with a generating capacity of 11MW (able to supply around 10,000 households) was completed by Abengoa Solar in Seville, Spain in Project name PS10 Location Seville, Spain Capacity 11 MW Land area 55 ha Electricity generation (predicted) MWh/year Solar array maximum temperature Thermal storage capacity 0 hours Type of cooling wet cooling tower Heat transfer fluid Water Table 6: Project information for PS10. Source: SolarPaces, NREL, CSP plant developer and owner websites The PS20, with twice the capacity of PS10, has been in operation since Figure 15: PS20 plant under construction with PS10 in the background. Source: Abengoa Solar 16

25 PS20 has twice the PS10 output (20MW), with 1,255 two-axis sun tracking heliostats driving 120m² mirrors. These mirrors concentrate solar radiation onto the receiver on top of a 165m tower. The tower follows the same technology as that of PS10 for electricity generation. PS20 represents second generation technology with important improvements to receiver and other critical elements. Features include control and operational systems enhancements, improved thermal energy storage system and a higher efficiency receiver. The plant has been designed by Abengoa Solar and Abener Energia was the contractor Linear Fresnel Linear Fresnel Reflectors (LFRs) approximate the shape of parabolic troughs with long rows of flat or slightly curved mirrors which reflect the solar radiation onto downward-facing linear, fixed receivers. A more recent design known as Compact Linear Fresnel Reflectors (CLFRs) has two parallel receivers for each row of mirrors and thus uses less land than parabolic troughs to produce a given amount of electricity. LFR systems heat water running through the receivers directly to generate steam at around 270 (Direct Steam Generation DSG), thereby eliminating the need for synthetic heat transfer fluids and heat exchangers. This, along with the lower manufacturing and installation cost of the mirrors make LFR systems less expensive than parabolic trough systems State of the technology LFR plants are in operation to date. The Australian company, Ausra, bought by the French multinational nuclear power company, Areva, built a Linear Fresnel power plant in 2005 New South Wales, Australia to contribute 1 MW to the adjacent coal-fired power plant. Ausra completed the expansion of this plant to 1 MW in This is an example of a so-called Integrated Solar Combined Cycle (ISCC) plant a hybrid between solar and coal. Ausra have built a second Linear Fresnel power plant at Kimberlina, California. It generates steam to drive a turbine to generate up to5 MW. The Novatec BioSol installation is described in the case study. Advantages: Figure 16: Operation of a Linear Fresnel collector. Source: Novatec Solar Materials are readily available. Lower manufacturing and installation costs than for parabolic trough systems. 3 Less land area required to produce a given amount of electricity than for parabolic troughs. Systems use water as the heat transfer medium so can generate steam directly and thus have lower transmission losses between collector array and steam turbine Studies by DLR indicate LFR cost 50-60% less than parabolic trough collectors per m2 (from CSP Today Article, Hovering in the wings: Linear Fresnel Technology, ). 17

26 Hybrid operation (in combination with a conventional power coal or gas power plant) is possible. Disadvantages: Performance, and investment and operating costs have not yet been commercially proven. Not straightforward to combine LFR systems with thermal storage Case Study The PE1 1.4MW LFR power plant started exporting electricity to the local grid in March 2009 and as such became the first commercial LFR plant in operation. The plant was developed by Novatec BioSol and Prointec and is located in Murcia, Spain. Lower costs in the LFR array (as compared to, for example, a parabolic trough array) allowed for higher investment in the more expensive dry cooling system. This means that water consumption is much lower than for a comparable parabolic trough plant and gives LFR plants an advantage in terms of permitting and environmental aspects. Figure 17: Linear Fresnel collector array, 1.4MW PE1 plant in Murcia, Spain. Source: Novatec Solar Project name Location Capacity Land area Electricity generation (predicted) PE1 Murcia, Spain 1.4 MW 7 ha 2000 MWh/year 18

27 5.4 Dish Solar array maximum temperature Thermal storage capacity Type of cooling Heat transfer fluid hours dry cooling Water Table 7: Project information for PE1. Source: SolarPaces, NREL, CSP plant developer and owner websites Figure 18: Operation of a dish collector. The dish tracks the sun throughout the day. Source: RENAC The dish reflector concentrates solar radiation onto a receiver at the focal point of the dish. The heat transfer medium (fluid or gas) in the receiver is heated to around 750 and drives a small piston, Stirling engine or micro turbine attached to the receiver to generate electricity directly at the dish. The dish tracks the sun throughout the day. Dish sizes typically range from 5-25kW. The high solar concentration and operating temperatures have allowed dish systems to achieve solar-toelectricity conversion efficiencies of up to 30%. Along with the high potential efficiency, another major advantage of dish systems is that they do not require a cooling system State of the technology There is still much development work required for dish systems, therefore the current energy cost is around twice that of parabolic trough systems. The two main goals of the development work are to reduce costs through mass production and to demonstrate long term reliability 4. Dish systems have traditionally been aimed at remote off-grid applications but the industry is becoming increasingly interested in the larger, grid-connected market. 4 From CSP Technology Roadmap 2010, International Energy Agency ( 19

28 Europe In the European EuroDish project, Schlaich Bergermann und Partner have extensively developed and tested several 10-kW systems, based on a structural dish and the Solo 161 kinematic Stirling engine at the Plataforma Solar de Almería (where the PS10 and PS20 solar towers are also located). Follow-up activities based on the EuroDish design are being pursued by a European Consortium of SBP, Inabensa, CIEMAT, DLR and others. EuroDish prototype demonstration units are currently being operated in Spain, France, Germany, Italy and India 5. Spanish company, Renovali, together with the US-based Stirling engine manufacturer, Infinia, have unveiled their 1MW dish plant in Albacete, Spain 6. USA In the USA, Stirling Energy Systems (SES is developing their 25-kW SunCatcher dish/stirling system for utility-scale markets. Six of these are currently being operated as a mini power plant at Sandia National Laboratories National Solar Thermal Test Facility in Albuquerque, NM, USA. Tessera Solar have built a 1.5MW reference plant, the Maricopa Solar Project, in Arizona, USA using the SES SunCatcher dish that has been operational since Tessera plans for a number of larger dish plants at Calico Solar Project and Imperial Valley Project in California, and the Western Ranch Project in Texas have all recently been put on hold due to financial and land ownership difficulties. Advantages: Parabolic dish systems have very high conversion efficiencies of over 30%. No water requirements for cooling. Systems are particularly well-suited to decentralized power supply and remote, standalone power applications. The system is modular. Parabolic dishes are not restricted to flat terrains. Most effectively integrate thermal storage in large plant. Easily manufactured and mass-produced from existing parts. Disadvantages: No large-scale commercial plants exist, so, performance, investment and operating costs have not yet been commercially proven. Mass production cost targets have not yet been proven. Lower dispatch ability potential for grid integration. Hybrid receivers have not yet been developed. 5 From SolarPaces Part 3: Task 1: Solar Thermal Electric Systems

29 : CS Figure 19: Dish, Ben Gurion National Solar Energy Center. Source: RENACP 5.5 Summary and comparison of the CSP technologies Important parameters for comparing the four CSP technologies are: annual energy yield capacity factor land requirement water requirement These are discussed below Annual energy yield The amount of electrical energy that can be generated by a CSP plant can be estimated from the approximation: Equation 1:The amount of electrical energy E annual DNI A ; Where annual annual E annual is the annual electrical energy generated by the plant in MWh/a; annual is the annual solar to electric efficiency; DNI annual is the annual Direct Normal Irradiation in MWh/ m 2 a ; A is the area of the collectors in the collector field in m 2. 21

30 The annual solar to electric efficiency is the ratio of total annual solar energy falling onto the collector array to total annual electricity generated. The efficiencies of the different technologies are given in below. Technology Annual solar to electric efficiency Parabolic trough 15% Solar tower 17-35% Linear Fernsel reflector 8-11% Dish 25-30% Table 8: Annual solar-to-electric efficiencies of the four main CSP technologies. annual is different for each of the CSP technologies. Therefore, the annual energy As we see, yield from each of the technologies will also be different. Example: What is site is 2.1MWh/ m 2 a, and A is 500,000 m 2? E annual for a parabolic trough plant where annual is 15%, DNI annual for the E annual= = MWh/a Capacity factor The capacity factor of a power plant is the ratio of the actual energy generated in a given period to the energy that could potentially be generated if the plant operated at full output continuously, e.g. the annual capacity factor would be calculated as: Equation 2: the annual capacity factor AnnualCF actual energy generated (MWh) 365days 24hours nominal power output(mw) The annual capacity factors that existing CSP plants are achieving are given in table 10 below. All the technologies have the potential to achieve much higher capacity factors if they include thermal storage. The presence of thermal storage allows the solar energy from the collector field to be used more effectively and also allows the plant to generate electricity during the night. This can potentially boost the capacity factor up to around 75%. Technology Capacity factor Parabolic trough without storage 25% Parabolic trough with storage greater than 40% Solar tower around 25% Linear Fresnel reflector around 17% Dish 50% Table 9: Capacity factors for the four main CSP technologies. Information on Linear Fresnel from Project Proposal for a CLFR Solar Thermal Plant in the Hunter Valley 7 7 Project Proposal for a Compact Linear Fresnel Reflector Solar Thermal Plant in the Hunter 22

31 5.5.3 Land requirement The collector field takes up the vast majority of the land required for a CSP plant. In all technologies the collectors are arranged in a particular way so as to maximize solar gain all day long and all year round. A certain amount of spacing is required between collectors to avoid (or minimize) the shading of one collector by another. The land use efficiency can be expressed either as the ratio of collector area to total plant area, or as the ratio of total plant area to electrical power output. See table 8 below for the land use efficiencies of the four main CSP technologies. Equation 3: the land use efficiencies 2 collector area, m Land use efficiency 2 totalplant area, m Or Land use efficiency, ha/mw totalplant area, ha output power,mw Technology Land use efficiency (collector area/total plant area, 2 m / 2 m Parabolic trough Solar tower Linear Fresnel reflector Dish ) Land use efficiency (total plant area/output power, ha/mw) Table 10: Land use efficiencies for the four main CSP technologies. For example, parabolic trough CSP plants have a land use efficiency of around For a hypothetical plant with 100m 2 of collector area, Totalplant area, m 2 2 collector area, m land use efficiency m ha (Total plant area is often given in hectares (ha) where 1 ha = For the same hypothetical plant, Output power,mw Water requirement 2 totalplant area, m land use efficiency m MW 9. 9kW 3.9 CSP plants require large amounts of water for cooling (see Section 4-3-3). The lower the efficiency of the power block the greater the water requirement for cooling because there is more heat loss. Table 13 shows the water requirement for the different technologies. We can see that a typical modern fossil fuel power plant requires much less water for cooling than the CSP 2.) Valley, by D. R. Mills, G. L. Morrison, P. Le Lièvre 23

32 technologies. This is because it operates at a higher efficiency. Dish technology does not require water for cooling because the electricity is generated directly at the dish and the waste heat is simply dissipated to the surrounding air. Technology Water cooling (Liters/MWh) Fossil fuel power plant 800 Parabolic trough 3000 Solar tower 2000 Linear Fresnel reflector 3000 Dish 80* *This water is consumption for cleaning. No water is required for cooling. Table 11: Water requirements for the four main CSP technologies. 6- Applications of CSP The main application for CSP is electricity generation. There is however scope for, and interest in, further applications such as: Solar gas for example generating hydrogen gas. Process heat for example for sterilization, heating, absorption cooling. Desalination large-scale desalination of sea water requires huge amounts of energy and can cause severe damage to local marine life. It should only be considered after all possible water conservation measures have been taken. However, advanced CSP systems can potentially operate cleaner desalination plants with very low environmental impacts Electricity transmission The building of a new grid, or significant strengthening of the existing grid, is a major cost for CSP schemes, not only in the physical installation but also in acquiring planning rights and all other associated permissions. For longer distance transmission, Desertec 9 have proposed a supergrid connecting the MENA countries to Europe. This would be via ultra-high voltage direct current cables, similar to those currently being installed in China for the transmission of electricity from the large hydroelectric schemes in the west of the country to the densely populated east coast. Desertec suggests, amidst some skepticism, that this supergrid could be operational by 2020.SP 8 More information can be found in the 2007 Aqua-CSP Report, Concentrating Solar Power for Seawater Desalination by the German Aerospace Centre (DLR), commissioned by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety. 9 The DESERTEC Foundation was established on 20 January 2009 as a non-profit foundation with the aim of promoting the implementation of the global DESERTEC Concept "Clean Power from Deserts" all over the world. For more information, see 24

33 8- Cost of CSP The economic feasibility of a CSP project is determined by both the available solar resource at the site and the power sale conditions in that country. If the local power purchase price does not cover the production cost then incentives or soft loans can cover the cost gap between the power cost and the available tariff. Environmental market mechanisms like renewable energy certificates could be an additional source of income, in particular in developing countries. The investment cost breakdown for a 50MW parabolic trough plant with 7 hours of storage is shown in figure 20 below. Figure 20: Investment cost breakdown for a 50MW parabolic trough CSP plant with 7 hours storage. Source: CSP Technology Roadmap 2010, International Energy Agency ( From figure 20 we see, for example, that the parabolic trough array accounts for 30% of the investment cost while the thermal storage system is 9%. Investment costs for a number of recent projects are summarized in table 14. Project name: Nevada Solar One Andasol 1 PS10 Developer: Acciona Solar Millennium/ACS Abengoa Year of completion: Location: Nevada, US Andalucia, Spain Seville, Spain Technology: parabolic trough parabolic trough solar tower Storage: no storage 7h salt storage 30min steam storage Power ( MW ): e 2 Area ( m ): Total cost (Million): Specific cost (Million/MW): Further information: de 25 om Table 12: Investment costs for three of the earliest completed CSP installations. Source: SolarPaces, NREL, CSP plant developer and owner websites.

34 From figure 21 we see that the specific cost of a parabolic trough plant is currently lower than a solar tower plant. When storage is included in the plant then the specific cost rises significantly. For all the technologies there is major cost reduction potential in engineering and planning costs, and in thermal generation and storage system costs, as well as 15-22% cost reduction potential in operation and maintenance costs 10. The current cost per kwh of electricity from CSP is It is predicted that this will come down to /kWhe in the medium to long term and the long term target beyond 2020 is a cost of 0.04/kWhe. See for the projected evolution of the levelised electricity cost from CSP plants to Figure 21: Projected evolution of the levelised electricity cost from CSP plants to 2050, in USD/MWh, under two different direct normal irradiance (DNI) levels in kwh/m2year. Source: Technology Roadmap, Concentrating Solar Power, International Energy Agency, CSP in Syria 9-1- Introduction We have a shortage with energy in Syria, and we have suitable area to implement projects for producing electricity using CSP. At the Higher Institute for Applied Science and Technology (HIAST), many projects for producing clean energy have been implemented. The last project in 2013 was generating electricity based on solar radiation and wind power by Eng. Mohammad Alshiekh Syria thermally In figure 22 we can see thermal map of Syria. We have convenient area on Al-Badiah in the east of Syria. Syria, like other Mediterranean countries, is rich in solar irradiation. The average solar irradiation on a horizontal surface is about 5 KWh/m 2 per day. This is a relatively high value especially when compared with the average irradiation in Germany which is about half that amount. The sun shines about hours per year and the cloudy days are about 40 days per year. The important point is that all the Syrian regions have high irradiation and the number of sunny days is relatively high. These indicators lead to a promising outlook for solar energy exploitation in Syria. [3] 10 Estela CSP cost roadmap 2010, A T Kearney 26

35 The following map illustrates the mean irradiation level in Syria: Figure 22: Syria thermally 10- Conclusion For the time being, CSP is the only method that could be used in our modern life to produce electricity depending on the sun. There are many projects with high power generating capability and high efficiency. These projects are implemented commercially. The most technology that is implemented commercially is parabolic trough. The potential technology that offers more efficiency is the technology of solar tower. The solar filed is the takes the major part of the cost of a CSP system. CSP systems technology is considered to be the technology of tomorrow, as it can provide a clean and cheap energy source for the world. 27