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  1. 1. SOLAR THERMAL COLLECTOR CHAPTER-1 INTRODUCTION Solar Thermal Electricity (STE) is a renewable energy source, which, after a demonstration period of 25 years since the first plant installations, is now entering a commercial ramp-up phase. There are two main approaches to generate power from sun radiation. PV for instance, directly converts captured solar radiation intro electricity. STE technology is based on the principle that concentration of solar radiation – by using mirrors in a receiver developed for that purpose – enables heating- up fluids at high temperature, around 350-550 degrees with current technologies. The thermal energy can then be used to generate electricity through a proper cycle process and electrical generator system. Figure:-1 breaks down STE systems into their main functionalities. The adoption of the STE technology for power generation is driven by its unique value proposition: STE is a competitively priced, predictable, dispatchable, and reliable renewable energy source with a high share of local content. STE storage capabilities differentiate this technology from renewable sources like wind or PV. STE can store the heat produced when the sun is shining, to produce electricity when it is really needed. This allows a higher dispatchability of electricity production that is currently only available, at competitive costs, by conventional sources like coal or gas or other renewables with limited potential or high environmental impact such as hydro, biomass and geothermal. Furthermore, STE offers these advantages without conventional sources drawbacks like CO2 emissions and requirement of fossil fuels. The present document synthesizes the collective effort of the STE industry, to derive an industry roadmap. The study was initiated by the European Solar Thermal Electricity Association, ESTELA with the objective e to assess STE’s competitiveness and to create a common understanding within the industry about the current status of the technology. It is meant to provide the basis for a dialogue with stakeholders in the energy sector, in particular between politicians, utilities and the STE industry. Solar Thermal Electricity (STE) comprises various technologies that convert concentrated solar radiation into heat to produce electricity. Mirrors focus direct solar radiation onto special receivers, in which fluids are heated up beyond 400°C. This heat is converted into mechanical energy by means of a thermodynamic cycle and then into electricity by the alternator. EE/SGV/STE /1
  2. 2. After over 20 years of successful operations, STE is now entering a commercial ramp-up phase with several large scale projects ≥50MW around the world. Growth drivers for this energy source include increasing demand for Renewable Energy Sources (RES) complemented by its unique value proposition when compared with other energy sources: • Predictability and reliability of production • Dispatchability due to proven and highly cost efficient storage and potential plant integrated back up firing • Grid stability due to the inertial features of STE power blocks • Cost competitiveness against other renewable energy sources • Large scale deployment and energy on demand • Long-term supply security and independence from oil and gas prices • High share of local content The present industry roadmap initiated by the European Solar Thermal Electricity Association (ESTELA) is based in a collective effort to assess STE’s competitiveness and to create a common understanding within the industry about the current status and expected evolution of the technologies. Figure 2 provides a high level overview of the industry vision that supports this roadmap. The STE industry is committed to technological improvement initiatives, focused on increasing plant efficiency and reducing deployment and operating costs. By 2015, when most of these improvements are expected to be implemented in new plants, energy production boosts greater than 10% and cost decreases up to 20% are expected to be achieved. Furthermore, economies of scale resulting from plant’s size increase will also contribute to reduce plans’ CAPEX per MW installed up to 30%. STE deployment in locations with very high solar radiation, such as the MENA region, further contribute to the achievement of cost competitiveness of this technology by reducing costs of electricity up to 25%. All these factors can lead to electricity generation cost savings up to 30% by 2025 and up to 50% by 2025, reaching competitive levels with conventional sources (e.g. coal/gas). Additionally to the potential to substitute conventional sources, STE can complement renewable energy sources portfolio as a peak to mid load provider. To achieve the targets pursued by the industry it is essential that governments foster the deployment of STE technology by addressing the following key energy and environmental policy enablers: EE/SGV/STE /2
  3. 3. Our sun produces 400,000,000,000,000,000,000,000,000 watts of energy every second and the belief is that it will last for another 5 billion years. The United States reached peak oil production in 1970, and there is no telling when global oi l production will peak, but it is accepted that when it is gone the party is over. The sun, however, is the most reliable and abundant source of energy. It is important to understand that solar thermal technology is not the same as solar panel, or photovoltaic, technology. Solar thermal electric energy generation concentrates the light from the sun to create heat, and that heat is used to run a heat engine, which turns a generator to make electricity. The working fluid that is heated by the concentrated sunlight can be a liquid or a gas. Different working fluids include water, oil, salts, air, nitrogen, helium, etc. Different engine types include steam engines, gas turbines, Stiiling engines, etc. All of these engines can be quite efficient, often between 30% and 40%, and are capable of producing 10’s to 100’s of megawatts of power. Photovoltaic, or PV energy conversion, on the other hand, directly converts the sun’s light into electricity. This means that solar panels are only effective during daylight hours because storing electricity is not a particularly efficient process. Heat storage is a far easier and efficient method, which is what makes solar thermal so attractive for large-scale energy production. Heat can be stored during the day and then converted into electricity at night. Solar thermal plants that have storage capacities can drastically improve both the economics and the dispatchability of solar electricity. Solar thermal power currently leads the way as the most cost-effective solar technology on a large scale. It currently beats other PV systems, and it also can beat the cost of electricity from fossil fuels such as natural gas. In terms of low-cost and high negative environmental impact, nothing competes with coal. but major solar thermal industry players such as eSolar, Brightsource, or Abengoa, have already beaten the price of photovoltaic and natural gas, and they have plans to beat the price of coal in the near future. With an increasingly industrializing planet, the leaders in solar thermal technology have an ever-growing market. The issue is, and will always be, how to make solar thermal technology more economical. There are currently two methods for solar thermal collection. The first is line focus collection. The second is point focus collection. Line focus is less expensive, technically less difficult, but not as efficient as point focus. The basis for this technology is a parabola-shaped mirror, which rotates on a single axis throughout the day EE/SGV/STE /3
  4. 4. tracking the sun. Point focus technique requires a series of mirrors surrounding a central tower, also known as a power tower. The mirrors focus the sun’s rays onto a point on the tower, which then transfers the heat into more usable energy. FIG:-1.1 Basic diagram of solar thermal collector FIG:-1.2 the nine steps of STE EE/SGV/STE /4
  5. 5. CHAPTER-2 Low temperature collectors Glazed Solar Collectors are designed primarily for space heating and they re circulate building air through a solar air panel where the air is heated and then directed back into the building. These solar space heating systems require at least two penetrations into the building and only perform when the air in the solar collector is warmer than the building room temperature. Most glazed collectors are used in the residential sector. Unglazed Solar Collectors are primarily used to pre-heat make-up ventilation air in commercial, industrial and institutional buildings with a high ventilation load. They turn building walls or sections of walls into low cost, high performance, unglazed solar collectors. Also called, "transpired solar panels", they employ a painted perforated metal solar heat absorber that also serves as the exterior wall surface of the building. Heat conducts from the absorber surface to the thermal boundary layer of air 1 mm thick on the outside of the absorber and to air that passes behind the absorber. The boundary layer of air is drawn into a nearby perforation before the heat can escape by convection to the outside air. The heated air is then drawn from behind the absorber plate into the building's ventilation system. A Trombe wall is a passive solar heating and ventilation system consisting of an air channel sandwiched between a window and a sun-facing thermal mass. During the ventilation cycle, sunlight stores heat in the thermal mass and warms the air channel causing circulation through vents at the top and bottom of the wall. During the heating cycle the Trombe wall radiates stored heat. Solar roof ponds are unique solar heating and cooling systems developed by Harold Hay in the 1960s. A basic system consists of a roof-mounted water bladder with a movable insulating cover. This system can control heat exchange between interior and exterior environments by covering and uncovering the bladder between night and day. When heating is a concern the bladder is uncovered during the day allowing sunlight to warm the water bladder and store heat for evening use. When cooling is a concern the covered bladder draws heat from the building's interior during the day and is uncovered at night to radiate heat to the cooler atmosphere. The Skytherm house in Atascadero, California uses a prototype roof pond for heating and cooling. EE/SGV/STE /5
  6. 6. Solar space heating with solar air heat collectors is more popular in the USA and Canada than heating with solar liquid collectors since most buildings already have a ventilation system for heating and cooling. The two main types of solar air panels are glazed and unglazed. Of the 21,000,000 square feet (2,000,000 m2) of solar thermal collectors produced in the United States in 2007, 16,000,000 square feet (1,500,000 m2) were of the low-temperature variety. Lowtemperature collectors are generally installed to heat swimming pools, although they can also be used for space heating. Collectors can use air or water as the medium to transfer the heat to their destination. Heat storage in low-temperature solar thermal systems Inter seasonal storage: Solar heat (or heat from other sources) can be effectively stored between opposing season s aquifers, underground geological strata, large specially constructed pits, and large tanks that are insulated and covered with earth. Short-term storage: Thermal mass materials store solar energy during the day and release this energy during cooler periods. Common thermal mass materials include stone, concrete, and water. The proportion and placement of thermal mass should consider several factors such as climate, day lighting, and shading conditions. When properly incorporated, thermal mass can passively maintain comfortable temperatures while reducing energy consumption. Low temperature collectors are flat plates collectors and evacuated tube collectors generally use to heat swimming pools .the temperature range of low thermal collectors 5 to 30 degree . Low-temperature collectors are flat plates generally used to heat swimming pools. FIG:- 2.1 Unglazed, "transpired" air collector EE/SGV/STE /6
  7. 7. FIG : - 2.2 Flat plate collectors Solar heat-driven ventilation A solar chimney (or thermal chimney) is a passive solar ventilation system composed of a hollow thermal mass connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing an updraft that pulls air through the building. These systems have been in use since Roman times and remain common in the Middle East. EE/SGV/STE /7
  8. 8. CHAPTER:-3 Medium temperature collectors These collectors could be used to produce approximately 50% and more of the hot water needed for residential and commercial use in the United States. In the United States, a typical system costs $4000– $6000 retail ($1400 to $2200 wholesale for the materials) and 30% of the system qualifies for a federal tax credit + additional state credit exists in about half of the states. Labor for a simple open loop system in southern climates can take 3–5 hours for the installation and 4–6 hours in Northern areas. Northern system require more collector area and more complex plumbing to protect the collector from freezing. With this incentive, the payback time for a typical household is four to nine years, depending on the state. Similar subsidies exist in parts of Europe. A crew of one solar plumber and two assistants with minimal training can install a system per day. Thermosiphon installation have negligible maintenance costs (costs rise if antifreeze and mains power are used for circulation) and in the US reduces a households' operating costs by $6 per person per month. Solar water heating can reduce CO 2 emissions of a family of four by 1 ton/year (if replacing natural gas) or 3 ton/year (if replacing electricity). Medium-temperature installations can use any of several designs: common designs are pressurized glycol, drain back, batch systems and newer low pressure freeze tolerant systems using polymer pipes containing water with photovoltaic pumping. European and International standards are being reviewed to accommodate innovations in design and operation of medium temperature collectors. Operational innovations include "permanently wetted collector" operation. This innovation reduces or even eliminates the occurrence of no-flow high temperature stresses called stagnation which would otherwise reduce the life expectancy of collectors. Medium-temperature collectors are also used flat plates collectors but are used for heating water for cooking. the temperature range of medium thermal collectors 30 degree to 100 degree . Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use. Medium-temperature installations can use any of several designs: common designs are pressurized glycol, drain back, batch systems and newer low pressure freeze tolerant systems using polymer pipes containing water with photovoltaic pumping. European and International standards are being reviewed to accommodate innovations in design and operation of medium temperature collectors. EE/SGV/STE /8
  9. 9. Solar drying Solar thermal energy can be useful for drying wood for construction and wood fuels such as wood chips for combustion. Solar is also used for food products such as fruits, grains, and fish. Crop drying by solar means is environmentally friendly as well as cost effective while improving the quality. The less money it takes to make a product, the less it can be sold for, pleasing both the buyers and the sellers. Technologies in solar drying include ultra low cost pumped transpired plate air collectors based on black fabrics. Solar thermal energy is helpful in the process of drying products such as wood chips and other forms of biomass by raising the temperature while allowing air to pass through and get rid of the moisture. Cooking Solar cookers use sunlight for cooking, drying and pasteurization. Solar cooking offsets fuel costs, reduces demand for fuel or firewood, and improves air quality by reducing or removing a source of smoke. The simplest type of solar cooker is the box cooker first built by Horace de Saussure in 1767. A basic box cooker consists of an insulated container with a transparent lid. These cookers can be used effectively with partially overcast skies and will typically reach temperatures of 50–100 °C. Concentrating solar cookers use reflectors to concentrate solar energy onto a cooking container. The most common reflector geometries are flat plate, disc and parabolic trough type. These designs cook faster and at higher temperatures (up to 350 °C) but require direct light to function properly. The Solar Kitchen in Auroville, India uses a unique concentrating technology known as the solar bowl. Contrary to conventional tracking reflector/fixed receiver systems, the solar bowl uses a fixed spherical reflector with a receiver which tracks the focus of light as the Sun moves across the sky. The solar bowl's receiver reaches temperature of 150 °C that is used to produce steam that helps cook 2,000 daily meals. Many other solar kitchens in India use another unique concentrating technology known as the Scheffler reflector. This technology was first developed by Wolfgang Scheffler in 1986. A Scheffler reflector is a parabolic dish that uses single axis tracking to follow the Sun's daily course. These reflectors have a flexible reflective surface that is able to change its curvature to adjust to seasonal variations in the incident angle of sunlight. Scheffler reflectors have the advantage of having a fixed focal point which improves the ease of cooking and are able to reach temperatures of 450650 °C. Built in 1999 by the Brahma Kumaris, the world's largest Scheffler reflector system in Abu EE/SGV/STE /9
  10. 10. Road, Rajasthan India is capable of cooking up to 35,000 meals a day. By early 2008, over 2000 large cookers of the Scheffler design had been built worldwide. Distillation Solar stills can be used to make drinking water in areas where clean water is not common. Solar distillation is necessary in these situations to provide people with purified water. Solar energy heats up the water in the still. The water then evaporates and condenses on the bottom of the covering glass. Medium-temperature collectors are also used flat plates collectors but are used for heating water for cooking the temperature range of medium thermal collectors 30 degree to 100 degree . Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use. FIG: - 3 Evacuated tube collectors EE/SGV/STE /10
  11. 11. CHAPTER:-4 High temperature collectors Where temperatures below about 95 °C are sufficient, as for space heating, flat-plate collectors of the non concentrating type are generally used. Because of the relatively high heat losses through the glazing, flat plate collectors will not reach temperatures much above 200 °C even when the heat transfer fluid is stagnant. Such temperatures are too low for efficient conversion to electricity. The efficiency of heat engines increases with the temperature of the heat source. To achieve this in solar thermal energy plants, solar radiation is concentrated by mirrors or lenses to obtain higher temperatures – a technique called Concentrated Solar Power (CSP). The practical effect of high efficiencies is to reduce the plant's collector size and total land use per unit power generated, reducing the environmental impacts of a power plant as well as its expense. As the temperature increases, different forms of conversion become practical. Up to 600 °C, steam turbines, standard technology, have an efficiency up to 41%. Above 600 °C, gas turbines can be more efficient. Higher temperatures are problematic because different materials and techniques are needed. One proposal for very high temperatures is to use liquid fluoride salts operating between 700 °C to 800 °C, using multi-stage turbine systems to achieve 50% or more thermal efficiencies. The higher operating temperatures permit the plant to use higher-temperature dry heat exchangers for its thermal exhaust, reducing the plant's water use – critical in the deserts where large solar plants are practical. High temperatures also make heat storage more efficient, because more watt-hours are stored per unit of fluid. Since the CSP plant generates heat first of all, it can store the heat before conversion to electricity. With current technology, storage of heat is much cheaper and more efficient than storage of electricity. In this way, the CSP plant can produce electricity day and night. If the CSP site has predictable solar radiation, then the CSP plant becomes a reliable power plant. Reliability can further be improved by installing a back-up combustion system. The back-up system can use most of the CSP plant, which decreases the cost of the back-up system CSP facilities utilize high electrical conductivity materials, such as copper, in field power cables, grounding networks, and motors for tracking and pumping fluids, as well as in the main generator and high voltage transformers. (See: Copper in concentrating solar thermal power facilities.) EE/SGV/STE /11
  12. 12. With reliability, unused desert, no pollution, and no fuel costs, the obstacles for large deployment for CSP are cost, aesthetics, land use and similar factors for the necessary connecting high tension lines. Although only a small % of the desert is necessary to meet global electricity demand, still a large area must be covered with mirrors or lenses to obtain a significant amount of energy. An important way to decrease cost is the use of a simple design. FIG:-4.1 Concentrated solar power plant using parabolic trough design. System designs During the day the sun has different positions. For low concentration systems (and low temperatures) tracking can be avoided (or limited to a few positions per year) if nonimaging optics are used. For higher concentrations, however, if the mirrors or lenses do not move, then the focus of the mirrors or lenses changes (but also in these cases nonimaging optics provides the widest acceptance angles for a given concentration). Therefore it seems unavoidable that there needs to be a tracking system that follows the position of the sun (for solar photovoltaic a solar tracker is only optional). The tracking system increases the cost and complexity. With this in mind, different designs can be distinguished in how they concentrate the light and track the position of the sun. EE/SGV/STE /12
  13. 13. Parabolic trough designs Parabolic trough power plants use a curved, mirrored trough which reflects the direct solar radiation onto a glass tube containing a fluid (also called a receiver, absorber or collector) running the length of the trough, positioned at the focal point of the reflectors. The trough is parabolic along one axis and linear in the orthogonal axis. For change of the daily position of the sun perpendicular to the receiver, the trough tilts east to west so that the direct radiation remains focused on the receiver. However, seasonal changes in the in angle of sunlight parallel to the trough does not require adjustment of the mirrors, since the light is simply concentrated elsewhere on the receiver. Thus the trough design does not require tracking on a second axis. The receiver may be enclosed in a glass vacuum chamber. The vacuum significantly reduces convective heat loss. A fluid (also called heat transfer fluid) passes through the receiver and becomes very hot. Common fluids are synthetic oil, molten salt and pressurized steam. The fluid containing the heat is transported to a heat engine where about a third of the heat is converted to electricity. Full-scale parabolic trough systems consist of many such troughs laid out in parallel over a large area of land. Since 1985 a solar thermal system using this principle has been in full operation in California in the United States. It is called the Solar Energy Generating Systems (SEGS) system. Other CSP designs lack this kind of long experience and therefore it can currently be said that the parabolic trough design is the most thoroughly proven CSP technology. The SEGS is a collection of nine plants with a total capacity of 350 MW. It is currently the largest operational solar system (both thermal and non-thermal). A newer plant is Nevada Solar One plant with a capacity of 64 MW. The 150 MW Andasol solar power stations are in Spain with each site having a capacity of 50 MW. Note however, that those plants have heat storage which requires a larger field of solar collectors relative to the size of the steam turbine-generator to store heat and send heat to the steam turbine at the same time. Heat storage enables better utilization of the steam turbine. With day and some nighttime operation of the steam-turbine Andasol 1 at 50 MW peak capacity produces more energy than Nevada Solar One at 64 MW peak capacity, due to the former plant's thermal energy storage system and larger solar field. The 280MW Solana Generating Station came online in Arizona in 2013 with 6 hours of power storage. Hassi R'Mel integrated solar combined cycle power station in Algeria and Martin Next Generation Solar Energy Center both use parabolic troughs in a combined cycle with natural gas. EE/SGV/STE /13
  14. 14. FIG:-4.2 Sketch of a parabolic trough design. A change of position of the sun parallel to the receiver does not require adjustment of the mirrors Power tower designs Power towers (also known as 'central tower' power plants or 'heliostat' power plants) capture and focus the sun's thermal energy with thousands of tracking mirrors (called heliostats) in roughly a two square mile field. A tower resides in the center of the heliostat field. The heliostats focus concentrated sunlight on a receiver which sits on top of the tower. Within the receiver the concentrated sunlight heats molten salt to over 1,000 °F(538 °C). The heated molten salt then flows into a thermal storage tank where it is stored, maintaining 98% thermal efficiency, and eventually pumped to a steam generator. The steam drives a standard turbine to generate electricity. This process, also known as the "Rankine cycle" is similar to a standard coal-fired power plant, except it is fueled by clean and free solar energy. The advantage of this design above the parabolic trough design is the higher temperature. Thermal energy at higher temperatures can be converted to electricity more efficiently and can be more cheaply stored for later use. Furthermore, there is less need to flatten the ground area. In principle a power tower can be built on the side of a hill. Mirrors can be flat and plumbing is concentrated in the tower. The disadvantage is that each mirror must have its own dual-axis control, while in the parabolic trough design single axis tracking can be shared for a large array of mirrors. A cost/performance comparison between power tower and parabolic trough concentrators was made by the NREL which estimated that by 2020 electricity could be produced from power towers for 5.47 EE/SGV/STE /14
  15. 15. ¢/kWh and for 6.21 ¢/kWh from parabolic troughs. The capacity factor for power towers was estimated to be 72.9% and 56.2% for parabolic troughs. There is some hope that the development of cheap, durable, mass producible heliostat power plant components could bring this cost down. The first solar power tower was the 10 MW Solar One in 1981, later redeveloped into Solar Two. The French 2MW Themis was completed in 1983 and the Soviet 5MW SES5 was built in 1985. All of these early project are out of commission. Solar thermal power did not progress from these experimental plants until the mid-2000s. The first commercial tower power plant was PS10 in Spain with a capacity of 11 MW, completed in 2007. Since then a number of plants have been proposed, several have been built on a number of countries (Spain, Germany, U.S., Turkey, China, India) but several proposed plants were cancelled as PV solar prices plummeted. A solar power tower is expected to come online in South Africa in 2014. Solar Power Facility in California will generate 392 MW of electricity from three towers making it the largest solar power tower plant when it comes online in late 2013. FIG:-4.3 Flat mirrors focus the light on the top of the tower. The white surfaces below the receiver are used for calibrating the mirror positions. EE/SGV/STE /15
  16. 16. Dish designs CSP-Stirling is known to have the highest efficiency of all solar technologies around 30% compared to solar PV approximately 15%,and is predicted to be able to produce the cheapest energy among all renewable energy sources in high scale production and hot areas, semi deserts etc. A dish Stirling system uses a large, reflective, parabolic dish (similar in shape to satellite television dish). It focuses all the sunlight that strikes the dish up onto a single point above the dish, where a receiver captures the heat and transforms it into a useful form. Typically the dish is coupled with a Stirling engine in a Dish-Stirling System, but also sometimes a steam engine is used. These create rotational kinetic energy that can be converted to electricity using an electric generator. The advantage of a dish system is that it can achieve much higher temperatures due to the higher concentration of light (as in tower designs). Higher temperatures lead to better conversion to electricity and the dish system is very efficient on this point. However, there are also some disadvantages. Heat to electricity conversion requires moving parts and that results in maintenance. In general, a centralized approach for this conversion is better than the decentralized concept in the dish design. Second, the (heavy) engine is part of the moving structure, which requires a rigid frame and strong tracking system. Furthermore, parabolic mirrors are used instead of flat mirrors and tracking must be dual-axis. In 2005 Southern California Edison announced an agreement to purchase solar powered Stirling engines from Stirling Energy Systems over a twenty-year period and in quantities (20,000 units) sufficient to generate 500 megawatts of electricity. In January 2010, Stirling Energy Systems and Tessera Solar commissioned the first demonstration 1.5-megawatt power plant ("Maricopa Solar") using Stirling technology in Peoria, Arizona. At the beginning of 2011 Stirling Energy's development arm, Tessera Solar, sold off its two large projects, the 709 MW Imperial project and the 850 MW Calico project to AES Solar and K.Road, respectively, and in the fall of 2011 Stirling Energy Systems applied for Chapter 7 bankruptcy due to competition from low cost photovoltaics. In 2012 the Maricopa plant was bought and dismantled by United Sun Systems. Higher temperatures lead to better conversion to electricity and the dish system is very efficient on this point. However, there are also some disadvantages. Heat to electricity conversion requires moving parts and that results in maintenance. EE/SGV/STE /16
  17. 17. A dish Stirling system uses a large, reflective, parabolic dish (similar in shape to satellite television dish). It focuses all the sunlight that strikes the dish up onto a single point above the dish, where a receiver captures the heat and transforms it into a useful form. Typically the dish is coupled with a Stirling engine in a Dish-Stirling System, but also sometimes a steam engine is used. These create rotational kinetic energy that can be converted to electricity using an electric generator. . A dish Stirling system uses a large, reflective, parabolic dish (similar in shape to satellite television dish). FIG:-4.4 A parabolic solar dish concentrating the sun's rays on the heating element of a Stirling engine. The entire unit acts as a solar tracker. EE/SGV/STE /17
  18. 18. Fresnel reflectors A linear Fresnel reflector power plant uses a series of long, narrow, shallow-curvature (or even flat) mirrors to focus light onto one or more linear receivers positioned above the mirrors. On top of the receiver a small parabolic mirror can be attached for further focusing the light. These systems aim to offer lower overall costs by sharing a receiver between several mirrors (as compared with trough and dish concepts), while still using the simple line-focus geometry with one axis for tracking. This is similar to the trough design (and different from central towers and dishes with dual-axis). The receiver is stationary and so fluid couplings are not required (as in troughs and dishes). The mirrors also do not need to support the receiver, so they are structurally simpler. When suitable aiming strategies are used (mirrors aimed at different receivers at different times of day), this can allow a denser packing of mirrors on available land area. Recent prototypes of these types of systems have been built in Australia and by Solarmundo in Belgium. The Solarmundo research and development project, with its pilot plant at Liège, was closed down after successful proof of concept of the Linear Fresnel technology. Subsequently, Solar Power Group GmbH (SPG), based in Munich, Germany, was founded by some Solarmundo team members. A Fresnel-based prototype with direct steam generation was built by SPG in conjunction with the German Aerospace Center (DLR). Based on the Australian prototype, a 177 MW plant had been proposed near San Luis Obispo in California and would be built by Ausra. But Ausra sold its planned California solar farm to First Solar. First Solar (a manufacturer of thin-film photovoltaic solar cells) will not build the Carrizo project, and the deal has resulted in the cancellation of Ausra’s contract to provide 177 megawatts to P.G.& E.Small capacity plants are an enormous economical challenge with conventional parabolic trough and drive design – few companies build such small projects. There are plans for SHP Europe, former Ausra subsidiary, to build a 6.5 MW combined cycle plant in Portugal. The German company SK Energy GmbH has plans to build several small 1-3 MW plants in Southern Europe (esp. in Spain) using Fresnel mirror and steam drive technology (Press Release). In May 2008, the German Solar Power Group GmbH and the Spanish Laer S.L. agreed the joint execution of a solar thermal power plant in central Spain. This will be the first commercial solar thermal power plant in Spain based on the Fresnel collector technology of the Solar Power Group. The EE/SGV/STE /18
  19. 19. planned size of the power plant will be 10 MW a solar thermal collector field with a fossil co-firing unit as backup system. The start of constructions is planned for 2009. The project is located in Gotarrendura, a small renewable energy pioneering village, about 100 km northwest of Madrid, Spain. A Multi-Tower Solar Array (MTSA) concept, that uses a point-focus Fresnel reflector idea, has also been developed, but has not yet been prototyped. Since March 2009, the Fresnel solar power plant Puerto Errado 1 (PE 1) of the German company Novatec Solar is in commercial operation in southern Spain . The solar thermal power plant is based on linear Fresnel collector technology and has an electrical capacity of 1.4 MW. Beside a conventional power block, PE 1 comprises a solar boiler with mirror surface of around 18,000m². The steam is generated by concentrating direct solar irradiation onto a linear receiver which is 7.40m above the ground. An absorber tube is positioned in the focal line of the mirror field in which water is evaporated directly into saturated steam at 270 °C and at a pressure of 55 bar by the concentrated solar energy. Since September 2011, due to a new receiver design developed by Novatec Solar, superheated steam with temperatures above 500°C can be generated. The 30 MW solar thermal power plant Puerto Errado 2 (PE2) is a scale up of PE 1 and also based on the Fresnel collector technology developed by the German company Novatec Solar. It comprises a mirror surface of 302,000m² and is in operation since August 2012. The plant is located in the region of Murcia. Five Swiss utilities (EBL, IWB, Ekz, ewz, ewb) are the owners of the world's largest Fresnel CSP power station. These systems aim to offer lower overall costs by sharing a receiver between several mirrors (as compared with trough and dish concepts), while still using the simple line-focus geometry with one axis for tracking. This is similar to the trough design (and different from central towers and dishes with dual-axis). The receiver is stationary and so fluid couplings are not required (as in troughs and dishes). The mirrors also do not need to support the receiver, so they are structurally simpler. When suitable aiming strategies are used (mirrors aimed at different receivers at different times of day), this can allow a denser packing of mirrors on available land area. the German Solar Power Group GmbH and the Spanish Laer S.L. agreed the joint execution of a solar thermal power plant in central Spain. This will be the first commercial solar thermal power plant in Spain based on the Fresnel collector technology of the Solar Power Group. The planned size of the power plant will be 10 MW a solar thermal collector field with a fossil co-firing unit as backup system. The start of constructions is planned for 2009. The project is located in Gotarrendura, a small renewable energy pioneering village, about 100 km northwest of Madrid, Spain. EE/SGV/STE /19
  20. 20. FIG:-4.5 linear Fresnel reflector Linear Fresnel reflector technologies: Rival single axis tracking technologies include the relatively new linear Fresnel reflector (LFR) and compact-LFR (CLFR) technologies. The LFR differs from that of the parabolic trough in that the absorber is fixed in space above the mirror field. Also, the reflector is composed of many low row segments, which focus collectively on an elevated long tower receiver running parallel to the reflector rotational axis. This system offers a lower cost solution as the absorber row is shared among several rows of mirrors. However, one fundamental difficulty with the LFR technology is the avoidance of shading of incoming solar radiation and blocking of reflected solar radiation by adjacent reflectors. Blocking and shading can be reduced by using absorber towers elevated higher or by increasing the absorber size, which allows increased spacing between reflectors remote from the absorber. Both these solutions increase costs, as larger ground usage is required. EE/SGV/STE /20
  21. 21. The CLFR offers an alternate solution to the LFR problem. The classic LFR has only one linear absorber on a single linear tower. This prohibits any option of the direction of orientation of a given reflector. Since this technology would be introduced in a large field, one can assume that there will be many linear absorbers in the system. Therefore, if the linear absorbers are close enough, individual reflectors will have the option of directing reflected solar radiation to at least two absorbers. This additional factor gives potential for more densely packed arrays, since patterns of alternative reflector inclination can be set up such that closely packed reflectors can be positioned without shading and blocking. advancement of this technology. Features that enhance the cost effectiveness of this system compared to that of the parabolic trough technology include minimized structural costs, minimized parasitic pumping losses, and low maintenance. CLFR power plants offer reduced costs in all elements of the solar array.[47] These reduced costs encourage the Minimized structural costs are attributed to the use of flat or elastically curved glass reflectors instead of costly sagged glass reflectors are mounted close to the ground. Also, the heat transfer loop is separated from the reflector field, avoiding the cost of flexible high pressure lines required in trough systems. Minimized parasitic pumping losses are due to the use of water for the heat transfer fluid with passive direct boiling. The use of glass-evacuated tubes ensures low radiative losses and is inexpensive. Studies of existing CLFR plants have been shown to deliver tracked beam to electricity efficiency of 19% on an annual basis as a preheater. Fresnel lenses: Prototypes of Fresnel lens concentrators have been produced for the collection of thermal energy by International Automated Systems. No full-scale thermal systems using Fresnel lenses are known to be in operation, although products incorporating Fresnel lenses in conjunction with photovoltaic cells are already available. The advantage of this design is that lenses are cheaper than mirrors. Furthermore, if a material is chosen that has some flexibility, then a less rigid frame is required to withstand wind load. A new concept of a lightweight, 'non-disruptive' solar concentrator technology using asymmetric Fresnel lenses that occupies minimal ground surface area and allows for large amounts of concentrated solar energy per concentrator is seen in the 'Desert Blooms' project, though a prototype has yet to be made. EE/SGV/STE /21
  22. 22. MicroCSP: "MicroCSP" references solar thermal technologies in which concentrating solar power (CSP) collectors are based on the designs used in traditional Concentrating Solar Power systems found in the Mojave Desert but are smaller in collector size, lighter and operate at lower thermal temperatures usually below 315 °C (600 °F). These systems are designed for modular field or rooftop installation where they are easy to protect from high winds, snow and humid deployments. Solar manufacturer Sopogy completed construction on a 1 MW CSP plant at the Natural Energy Laboratory of Hawaii. MicroCSP is used for community-sized power plants (1 MW to 50 MW), for industrial, agricultural and manufacturing 'process heat' applications, and when large amounts of hot water are needed, such as resort swimming pools, water parks, large laundry facilities, sterilization, distillation and other such uses. Enclosed parabolic trough: The enclosed parabolic trough solar thermal system encapsulates the components within a greenhouselike glasshouse. The glasshouse protects the components from the elements that can negatively impact system reliability and efficiency. Lightweight curved solar-reflecting mirrors are suspended from the ceiling of the glasshouse by wires. A single-axis tracking system positions the mirrors to retrieve the optimal amount of sunlight. The mirrors concentrate the sunlight and focus it on a network of stationary steel pipes, also suspended from the glasshouse structure. Water is pumped through the pipes and boiled to generate steam when intense sun radiation is applied. The steam is available for process heat. Sheltering the mirrors from the wind allows them to achieve higher temperature rates and prevents dust from building up on the mirrors as a result from exposure to humidity. The advantage of this design is that lenses are cheaper than mirrors. Furthermore, if a material is chosen that has some flexibility, then a less rigid frame is required to withstand wind load. A new concept of a lightweight, 'non-disruptive' solar concentrator technology using asymmetric Fresnel lenses that occupies minimal ground surface area and allows for large amounts of concentrated solar energy per concentrator is seen in the 'Desert Blooms' [50]project, though a prototype has yet to be made. EE/SGV/STE /22
  23. 23. CHAPTER-5 Future scope of solar thermal energy we know that sun is a good source of energy so that in the future we will all most depends on sun’s energy by using solar thermal energy. The STE industry is committed technological Improvements and focused on increasing plant Efficiency and reducing operating cost. All these factors can lead to electricity generation cost saving up to 30%by 2015 and up to 50% by 2025 and saving conventional cost like coal /gas and all other fuels by increasing size of plant. Solar Thermal Electricity (STE) comprises various technologies that convert concentrated solar radiation into heat to produce electricity. Mirrors focus direct solar radiation onto special receivers, in which fluids are heated up beyond 400°C. This heat is converted into mechanical energy by means of a thermodynamic cycle and then into electricity by the alternator. After over 20 years of successful operations, STE is now entering a commercial ramp-up phase with several large scale projects ≥50MW around the world. Growth drivers for this energy source include increasing demand for Renewable Energy Sources (RES) complemented by its unique value proposition when compared with other energy sources: • Predictability and reliability of production • Dispatchability due to proven and highly cost effi cient storage and potential plant integrated back up firing The present industry roadmap initiated by the European Solar Thermal Electricity Association (ESTELA) is based in a collective effort to assess STE’s competitiveness and to create a common understanding within the industry about the current status and expected evolution of the technologies. provides a high level overview of the industry vision that supports this roadmap. The STE industry is committed to technological improvement initiatives, focused on increasing plant efficiency and reducing deployment and operating costs. By 2015, when most of these improvements are expected to be implemented in new plants, energy production boosts greater than 10% and cost decreases to 20% are expected to be achieved. Furthermore, economies of scale resulting from plant’s size increase will also contribute to reduce plants’ CAPEX per MW installed up to 30%. STE deployment in locations with very high solar radiation, such as the MENA region, further contribute to the achievement of cost competitiveness of EE/SGV/STE /23
  24. 24. this technology by reducing costs of electricity up to 25%. All these factors can lead to electricity generation cost savings up to 30% by 2015 and up to 50% by 2025, reaching competitive levels with conventional sources (e.g. coal/gas). Additionally to the potential to substitute conventional sources, STE can complement renewable energy sources portfolio as a peak to mid load provider. To achieve the targets pursued by the industry it is essential that governments foster the deployment of STE technology by addressing the following key energy and environmental policy. Solar power deals with the use of solar radiation for practical purposes. It has been employed in order to decrease the carbon footprints from our environment. It is the basic motor of all forms of energy generation methods. It is free and clean to use. This form of energy is available in abundance in our environment. The fossil fuels are also mere frozen solar power. Solar energy has remained a necessary ingredient for decades now. It's demand for usage still prevails. It is mainly used for the domestic purposes these days. Solar power systems operate by converting the solar energy into the electrical energy. Usage of this power helps tremendously in reducing the power bills and also largely helps our environment. Using this form of power for domestic purposes has many advantages. The people who use it know it better. All of the people who use only solar power operated electric appliances do not wish to switch to other power systems. For generating the solar power at our houses, we first need to install the solar panels on the roofs of the buildings, The solar panels are placed where their is ample amount on sunlight falling on them. Solar panels trap the heat energy and generate electricity. This form of power can be used to rum many home electric appliances. A traditional boiler can be used for heating the water when their is no sunlight. The photovoltaic cells also play an integral role in our lives. They are basically the panels that you can attach it onto your roofs. With the sunlight falls onto them, the electricity is generated. Their are many sizes of solar panels available in the market today. The size is proportional to the amount of electricity to be generated. You must be watchful of the strength of your roof before installing the solar panels. For the generation of solar power at your homes, place the solar panels to the south. The solar water heaters are primarily used to heat up the water for the domestic purposes. They are of two types: direct solar water heaters and indirect solar water heaters. To set up the solar panels, you just need to have little knowledge about plumbing and electrical wiring. These solar water heaters reduce the electricity bills and expenses. Solar panels create pollution-free environment. Solar power is the most flourishing form of eco-friendly energy. It contains no moving parts and generates no noise. It does not release any harmful radiations into the environment. This form of energy does not affect the EE/SGV/STE /24
  25. 25. human life as well as the animal life. It converts light form into electricity very silently. There is a particular disadvantage of this form of energy i,e its output variability, When their is no direct sunlight, these panels fail to work until their is adequate sunlight. As the technology has advanced, we now have started making use of electric vehicles too. Such vehicles have started becoming readily available and are operated using battery technology as well as solar energy. Their costs are now dropping and such vehicles are becoming readily available to the masses. Electric vehicles have a wonderful future for sure as they do not pollute the environment. They are also cheap in their usage. EE/SGV/STE /25
  26. 26. CHAPTER:-6 Advantage and disadvantage of STE Solar energy is becoming increasingly popular as the world takes notice of the burgeoning carbon emission problems that come with burning fossil fuels. But why all the fuss? Nay-sayers have become less and less vocal as solar energy’s popularity has grown increasingly unhindered. Below I will discuss the advantages and disadvantages of solar energy. Advantages of Solar Energy:No green house gases: The first and foremost advantage of solar energy is that, beyond panel production, it does not emit any green house gases. Solar energy is produced by conducting the sun’s radiation – a process void of any smoke, gas, or other chemical by-product. This is the main driving force behind all green energy technology, as nations attempt to meet climate change obligations in curbing emissions. Italy’s Montalto di Castro solar park is a good example of solar’s contribution to curbing emissions. It avoids 20,000 tonnes per year of carbon emissions compared to fossil fuel energy production. Ongoing Free Energy: Another advantage of using solar energy is that beyond initial installation and maintenance, solar energy is free.Solar doesn’t require expensive and ongoing raw materials like oil or coal, and requires significantly lower operational labor than conventional power production. Raw materials don’t have to be constantly extracted, refined, and transported to the power plant.Life expectancy ranges between manufacturers, but many panels produced today carry a 25-30 year warranty – with a life expectancy of up to 40 years. Decentralization of power: Solar energy offers decentralization in most (sunny) locations, meaning self-reliant societies.Oil, coal, and gas used to produce conventional electricity is often transported cross-country or internationally. This transportation has a myriad of additional costs, including monetary costs, pollution costs of transport, and roading wear and tear costs, all of which is avoided with solar.Of course, decentralization has its limits as some locations get more sunlight than others. EE/SGV/STE /26
  27. 27. Going off the grid with solar: Solar energy can be produced on or off the grid. On grid means a house remains connected to the state electricity grid. Off grid has no connection to the electricity grid, so the house, business or whatever being powered is relying solely on solar or solar-hybrid. The ability to produce electricity off the grid is a major advantage of solar energy for people who live in isolated and rural areas. Power prices and the cost of installing power lines are often exorbitantly high in these places and many have frequent power-cuts. Many city-dwellers are also choosing to go off the grid with their alternate energy as part of a self-reliant lifestyle. Fig-6.1Solar Barn Solar jobs A particularly relevant and advantageous feature of solar energy production is that it creates jobs. The EIAA states that Europe’s solar industry has created 100,000 jobs so far. Solar jobs come in many forms, from manufacturing, installing, monitoring and maintaining solar panels, to research and design, development, cultural integration, and policy jobs. EE/SGV/STE /27
  28. 28. The book Natural Capitalism offers a good perspective on the employment potential of green design and a prudent approach to using resources. The book proposes that while green technology and associated employment can be expensive, much greater money can be saved when combined with proven “whole-system” efficiency strategies (e.g passive lighting and airflow). With solar energy currently contributing only an estimated 4% of the world’s electricity, and an economic-model where raw materials don’t have to be indefinitely purchased and transported, it’s reasonable so assume solar jobs are sustainable if the solar industry can survive the recession. Solar’s avoidance of politics and price volatility One of the biggest advantages of solar energy is the ability to avoid the politics and price volatility that is increasingly characterizing fossil fuel markets. The sun is an unlimited commodity that can be sourced from many locations, meaning solar is less vulnerable to the price manipulations and politics that have more than doubled the price of many fossil fuels in the past decade. While the price of fossil fuels have increased, the per watt price of solar energy production has more than halved in the past decade – and is set to become even cheaper in the near future as better technology and economies of scale take effect. Furthermore, the ever-abundant nature of the sun’s energy would hint at a democratic and competitive energy market – where wars aren’t fought over oil fields and high-demand raw materials aren’t controlled by monopolies. Of course, a new form of politics has emerged with regard to government incentives and the adoption of solar, however these politics are arguably minor compared to the fossil fuel status quo. Saving eco-systems and livelihoods Because solar doesn’t rely on constantly mining raw materials, it doesn’t result in the destruction of forests and eco-systems that occurs with many fossil fuel operations. Destruction can come in many forms, from destruction through accepted extraction methods, to more irresponsible practices in vulnerable areas, to accidents. EE/SGV/STE /28
  29. 29. Major examples include Canada’s tar sands mining which involves the systematic destruction of the Boreal Forest (which accounts for 25% of the world’s intact forest land), and creates large toxic byproduct ponds. The Niger Delta is an example where excessive and irresponsible oil extraction practices have poisoned fishing deltas previously used by villagers as the main source of food and employment, creating extremely desperate poverty and essentially decimating villages. DISADVATAGES Solar doesn’t work at night The biggest disadvantage of solar energy is that it’s not constant. To produce solar electricity there must be sunlight. So energy must be stored or sourced elsewhere at night. Beyond daily fluctuations, solar production decreases over winter months when there are less sunlight hours and sun radiation is less intense. Solar Inefficiency A very common criticism is that solar energy production is relatively inefficient. Currently, widespread solar panel efficiency – how much of the sun’s energy a solar panel can convert into electrical energy – is at around 22%. This means that a fairly vast amount of surface area is required to produce adequate electricity. However, efficiency has developed dramatically over the last five years, and solar panel efficiency should continue to rise steadily over the next five years. For the moment though, low efficiency is a relevant disadvantage of solar. Solar inefficiency is an interesting argument, as efficiency is relative. One could ask “inefficient compared to what?” And “What determines efficiency?” Solar panels currently only have a radiation efficiency of up to 22%, however they don’t create the carbon by-product that coal produces and doesn’t require constant extraction, refinement, and transportation – all of which surely carry weight on efficiency scales. EE/SGV/STE /29
  30. 30. Storing Solar Solar electricity storage technology has not reached its potential yet. While there are many solar drip feed batteries available, these are currently costly and bulky, and more appropriate to small scale home solar panels than large solar farms. Solar panels are bulky Solar panels are bulky. This is particularly true of the higher-efficiency, traditional silicon crystalline wafer solar modules. These are the large solar panels that are covered in glass. New technology thin-film solar modules are much less bulky, and have recently been developed as applications such as solar roof tiles and “amorphous” flexible solar modules. The downfall is that thinfilm is currently less efficient than crystalline wafer solar. EE/SGV/STE /30
  31. 31. CHAPTER-7 APPLICATION Low Temperature (> 30C) Swimming pool heating Ventilation air preheating •Medium Temperature (30C –100C) Domestic water and space heating Commercial cafeterias, laundries, hotels Industrial process heating •High Temperature (> 100C) Industrial process heating Electricity generation EE/SGV/STE /31
  32. 32. CHAPTER-8 CONCLUSION Low medium and high temperature collectors and solar thermal technology for production of Electricity and water heating and various purpose is ready for the industry. Various types of single and dual purpose plants and Industry Have been analyzed and tested in the solar thermal fields. Solar Thermal Electricity (STE) is a renewable energy source, which, after a demonstration period of 25 years since the first plant installations, is now entering a commercial ramp-up phase. There are two main approaches to generate power from sun radiation. PV for instance, directly converts captured solar radiation intro electricity. STE technology is based on the principle that concentration of solar radiation – by using mirrors in a receiver developed for that purpose – enables heating- up fluids at high temperature, around 350-550 degrees with current technologies. The thermal energy can then be used to generate electricity through a proper cycle process and electrical generator system. breaks down STE systems into their main functionalities. The adoption of the STE technology for power generation is driven by its unique value proposition: STE is a competitively priced, predictable, dispatchable, and reliable renewable energy source with a high share of local content. STE storage capabilities differentiate this technology from renewable sources like wind or PV. STE can store the heat produced when the sun is shining, to produce electricity when it is really needed. This allows a higher dispatchability of electricity production that is currently only available, at competitive costs, by conventional sources like coal or gas or other renewables with limited potential or high environmental impact such as hydro, biomass and geothermal. Furthermore, STE offers these advantages without conventional sources drawbacks like CO2 emissions and requirement of fossil fuels. The present document synthesizes the collective effort of the STE industry, to derive an industry roadmap. The study was initiated by the European Solar Thermal Electricity Association, ESTELA with the objective e to assess STE’s competitiveness and to create a common understanding within the industry about the current status of the technology. It is meant to provide the basis for a dialogue with stakeholders in the energy sector, in particular between politicians, utilities and the STE industry. EE/SGV/STE /32
  33. 33. REFERENCES 1. www.estelasolar.eu/.../2010-06%20-%20Solar%20Thermal%20ElectriciTY 2. http://aloisiuskolleg.www.de/schule/fachbereiche/comenius/charles/solar.html. 3. solarthermalworld.org/.../solar-heat- - - - 4. social.csptoday.com/.../spanish-update-solar-thermal-energy-currently-v 5. www.solarexpo.com 6. ^ "Solar Thermal vs. Photovoltaic (PV) – Which Should You Choose?". Greenrednecks.com. 1999-02-22. Retrieved 2013-08-20. EE/SGV/STE /33

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