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Click on any topic below for more information:-What are Photovoltaics? -What is Solar Thermal Energy?
-Are there grants or other financial resources available? (top) Estimated Roof Area Needed in Square Feet
* Although the efficiency (percentage of sunlight converted to electrical energy) varies with different types of PV Modules available today, higher-efficiency modules typically cost more. So, a less efficient system is not necessarily less cost-effective. - The Vermont Renewable Energy Resource Center. (top) PhotovoltaicsFrom Wikipedia, the free encyclopedia  Photovoltaic cells produce electricity directly from sunlight Photovoltaics, or PV for short, is a technology that converts light directly into electricity. Photovoltaics is also the field of study relating to this technology and there are many research institutes devoted to work on photovoltaics.[1][2] Due to the growing need for solar energy, the manufacture of solar cells and solar photovoltaic array has expanded dramatically in recent years.[3][4][5] Photovoltaic production has been doubling every two years, increasing by an average of 48 percent each year since 2002, making it the world’s fastest-growing energy technology. At the end of 2007, according to preliminary data, cumulative global production was 12,400 megawatts.[6] Roughly 90% of this generating capacity consists of grid-tied electrical systems. Such installations may be ground-mounted (and sometimes integrated with farming and grazing)[7] or built into the roof or walls of a building, known as Building Integrated Photovoltaic or BIPV for short.[8] Financial incentives, such as preferential feed-in tariffs for solar-generated electricity and net metering, have supported solar PV installations in many countries including Germany, Japan, and the United States.[9] Overview
Photovoltaics is best known as a method for generating solar power by using solar cells packaged in photovoltaic modules, often electrically connected in multiples as solar photovoltaic arrays to convert energy from the sun into electricity. To explain the photovoltaic solar panel more simply, photons from sunlight knock electrons into a higher state of energy, creating electricity. Photovoltaics can refer to the field of study relating to this technology, and the term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Virtually all photovoltaic devices are some type of photodiode. Solar cells produce direct current electricity from light, which can be used to power equipment or to recharge a battery. The first practical application of photovoltaics was to power orbiting satellites and other spacecraft and pocket calculators, but today the majority of photovoltaic modules are used for grid connected power generation. In this case an inverter is required to convert the DC to AC. There is a smaller market for off grid power for remote dwellings, roadside emergency telephones, remote sensing, and cathodic protection of pipelines. Cells require protection from the environment and are packaged usually behind a glass sheet. When more power is required than a single cell can deliver, cells are electrically connected together to form photovoltaic modules, or solar panels. A single module is enough to power an emergency telephone, but for a house or a power plant the modules must be arranged in arrays. Although the selling price of modules is still too high to compete with grid electricity in most places, significant financial incentives in Japan and then Germany triggered a huge growth in demand, followed quickly by production. (top) Current developmentThe most important issue with solar panels is capital cost (installation and materials). Newer alternatives to standard crystalline silicon modules including casting wafers instead of sawing,[10] thin film (CdTe[11] CIGS,[12] amorphous Si,[13] microcrystalline Si), concentrator modules, 'Sliver' cells, and continuous printing processes. Due to economies of scale solar panels get less costly as people use and buy more — as manufacturers increase production to meet demand, the cost and price is expected to drop in the years to come. As of early 2006, the average cost per installed watt for a residential sized system was about USD 6.50 to USD 7.50, including panels, inverters, mounts, and electrical items.[14] In 2006 investors began offering free solar panel installation in return for a 25 year contract to purchase electricity at a fixed price, normally set at or below current electric rates.[15][16] (top) Worldwide installed photovoltaic totalsWorld solar photovoltaic (PV) market installations reached a record high of 2,826 Megawatts peak (MWp) in 2007.[17] The three leading countries (Germany, Japan and the USA) represent nearly 89% of the total worldwide PV installed capacity. On Wed 01 Aug 2007, word was published of construction of a production facility in China, which is projected to be one of the largest wafer factories in the world, with an annual capacity of around 1,500MW.[18] Germany was the fastest growing major PV market in the world during 2006 and 2007. In 2007, over 1.3 GWp of PV was installed. The German PV industry generates over 10,000 jobs in production, distribution and installation. By the end of 2006, nearly 88% of all solar PV installations in the EU were in grid-tied applications in Germany. The balance is off-grid (or stand alone) systems.[19] Photovoltaic power capacity is measured as maximum power output under standardized test conditions (STC) in "Wp" (Watts peak).[20] The actual power output at a particular point in time may be less than or greater than this standardized, or "rated," value, depending on geographical location, time of day, weather conditions, and other factors.[21] Solar photovoltaic array capacity factors are typically under 25%, which is lower than many other industrial sources of electricity.[22] Therefore the 2007 installed base peak output would have provided an average output of 1.7 GW (assuming 20% × 8,688 MWp). This represented 0.0894 percent of global demand at the time.[23] (top)
Notes: While National Report(s) may be cited as source(s) within an International Report, any contradictions in data are resolved by using only the most recent report's data. Exchange rates represent the 2007 annual average of daily rates[35] Applications of PV
(top) PV power stations
The Table below provides details of some of the largest photovoltaic plants in the world. As shown, Germany has a 10 MW photovoltaic system in Pocking, and a 12 MW plant in Arnstein, with a 40 MW power station planned for Muldentalkreis. Portugal has an 11 MW plant in Serpa and a 62 MW power station is planned for Moura. A 20 MW power plant is also planned for Beneixama, Spain. The photovoltaic power station proposed for Australia will use heliostat concentrator technology and will not come into service until 2010. It is expected to have a capacity of 154 MW when it is completed in 2013.[40]
PV in buildings
Building-integrated photovoltaics (BIPV) are increasingly incorporated into new domestic and industrial buildings as a principal or ancillary source of electrical power,[56] and are one of the fastest growing segments of the photovoltaic industry.[57] Typically, an array is incorporated into the roof or walls of a building, and roof tiles with integrated PV cells can now be purchased. Arrays can also be retrofitted into existing buildings; in this case they are usually fitted on top of the existing roof structure. Alternatively, an array can be located separately from the building but connected by cable to supply power for the building. Where a building is at a considerable distance from the public electricity supply (or grid) - in remote or mountainous areas – PV may be the preferred possibility for generating electricity, or PV may be used together with wind, diesel generators and/or hydroelectric power. In such off-grid circumstances batteries are usually used to store the electric power. (top) PV in transport
PV has traditionally been used for auxiliary power in space. PV is rarely used to provide motive power in transport applications, but is being used increasingly to provide auxiliary power in boats and cars. Recent advances in solar cell technology, however, have shown the cell's ability to administer significant hydrogen production, making it one of the top prospects for alternative energy for automobiles. (top) PV in standalone devices
PV has been used for many years to power calculators and novelty devices. Improvements in integrated circuits and low power LCD displays make it possible to power a calculator for several years between battery changes, making solar calculators less common. In contrast, solar powered remote fixed devices have seen increasing use recently, due to increasing cost of labour for connection of mains electricity or a regular maintenance programme. In particular, parking meters,[58] emergency telephones,[59] and temporary traffic signs. (top) Economics of PV See also: Renewable energy commercialization
Power costsThe PV industry is beginning to adopt levelized cost of energy (LCOE) as the unit of cost. The results of a sample calculation can be found on pp. 52, 53 of the 2007 DOE report describing the plans for solar power 2007-2011 [1]. For a 10 MW plant in Phoenix, AZ, the LCOE is estimated at $0.15 to 0.22/kWh. The table below is a pure mathematical calculation. It illustrates the calculated total cost in US cents per kilowatt-hour of electricity generated by a photovoltaic system as function of the investment cost and the efficiency, assuming some accounting parameters such as cost of capital and depreciation period. The row headings on the left show the total cost, per peak kilowatt (kWp), of a photovoltaic installation. The column headings across the top refer to the annual energy output in kilowatt-hours expected from each installed peak kilowatt. This varies by geographic region because the average insolation depends on the average cloudiness and the thickness of atmosphere traversed by the sunlight. It also depends on the path of the sun relative to the panel and the horizon. Panels can be mounted at an angle based on latitude, which can add to total energy output.[60] Solar tracking can also be utilized to access even more perpendicular sunlight, thereby raising the total energy output. The calculated values in the table reflect the total cost in cents per kilowatt-hour produced. They assume a 10% total capital cost (for instance 4% interest rate, 1% operating and maintenance cost, and depreciation of the capital outlay over 20 years).
(top) Grid parityGrid parity, the point at which photovoltaic electricity is equal to or cheaper than grid power, is achieved first in areas with abundant sun and high costs for electricity such as in California and Japan.[61] Grid parity has been reached in Hawaii and other islands that otherwise use diesel fuel to produce electricity. George W. Bush has set 2015 as the date for grid parity in the USA.[62][63] General Electric's Chief Engineer predicts grid parity without subsidies in sunny parts of the United States by around 2015. Other companies predict an earlier date.[64] In Italy, PV power has been cheaper than retail grid electricity since 2006. One kWh in Italy costs 21.08 €-cents.[65] Italy has an average of 1,600 kWh/m² sun power per year (Sicily has even more, at 1,800 kWh/m²). Financial incentives
The political purpose of incentive policies for PV is to grow the industry even where the cost of PV is significantly above grid parity, to allow it to achieve the economies of scale necessary to reach grid parity. The policies are implemented to promote national energy independence, high tech job creation and reduction of CO2 emissions. Three incentive mechanisms are used (often in combination):
With investment subsidies, the financial burden falls upon the taxpayer, while with feed-in tariffs the extra cost is distributed across the utilities' customer bases. While the investment subsidy may be simpler to administer, the main argument in favour of feed-in tariffs is the encouragement of quality. Investment subsidies are paid out as a function of the nameplate capacity of the installed system and are independent of its actual power yield over time, thus rewarding the overstatement of power and tolerating poor durability and maintenance. Some electric companies offer rebates to their customers, such as Austin Energy in Texas, which offers $4.50/watt installed up to $13,500.[66] With feed-in tariffs, the financial burden falls upon the consumer. They reward the number of kilowatt-hours produced over a long period of time, but because the rate is set by the authorities, it may result in perceived overpayment. The price paid per kilowatt-hour under a feed-in tariff exceeds the price of grid electricity. Net metering" refers to the case where the price paid by the utility is the same as the price charged. Where price setting by supply and demand is preferred, RECs can be used. In this mechanism, a renewable energy production or consumption target is set, and the consumer or producer is obliged to purchase renewable energy from whoever provides it the most competitively. The producer is paid via an REC. In principle this system delivers the cheapest renewable energy, since the lowest bidder will win. However uncertainties about the future value of energy produced are a brake on investment in capacity, and the higher risk increases the cost of capital borrowed. The Japanese government through its Ministry of International Trade and Industry ran a successful programme of subsidies from 1994 to 2003. By the end of 2004, Japan led the world in installed PV capacity with over 1.1 GW.[67] In 2004, the German government introduced the first large-scale feed-in tariff system, under a law known as the 'EEG' (Erneuerbare Energien Gesetz) which resulted in explosive growth of PV installations in Germany. At the outset the FIT was over 3x the retail price or 8x the industrial price. The principle behind the German system is a 20 year flat rate contract. The value of new contracts is programmed to decrease each year, in order to encourage the industry to pass on lower costs to the end users. The programme has been more successful than expected with over 1GW installed in 2006, and political pressure is mounting to decrease the tariff to lessen the future burden on consumers. Subsequently Spain, Italy, Greece and France introduced feed-in tariffs. None have replicated the programmed decrease of FIT in new contracts though, making the German incentive relatively less and less attractive compared to other countries. The French FIT offers a uniquely high premium (EUR 0.55/kWh) for building integrated systems. California, Greece, France and Italy have 30-50% more insolation than Germany making them financially more attractive. In 2006 California approved the 'California Solar Initiative', offering a choice of investment subsidies or FIT for small and medium systems and a FIT for large systems. The small-system FIT of $0.39 per kWh (far less than EU countries) expires in just 5 years, and the alternate "EPBB" residential investment incentive is modest, averaging perhaps 20% of cost. All California incentives are scheduled to decrease in the future depending as a function of the amount of PV capacity installed. At the end of 2006, the Ontario Power Authority (Canada) began its Standard Offer Program, the first in North America for small renewable projects (10MW or less). This guarantees a fixed price of $0.42 CDN per kWh over a period of twenty years. Unlike net metering, all the electricity produced is sold to the OPA at the SOP rate. The generator then purchases any needed electricity at the current prevailing rate (e.g., $0.055 per kWh). The difference should cover all the costs of installation and operation over the life of the contract. The price per kilowatt hour or per peak kilowatt of the FIT or investment subsidies is only one of three factors that stimulate the installation of PV. The other two factors are insolation (the more sunshine, the less capital is needed for a given power output) and administrative ease of obtaining permits and contracts. Unfortunately the complexity of approvals in California, Spain and Italy has prevented comparable growth to Germany even though the return on investment is better. In some countries, additional incentives are offered for BIPV compared to stand alone PV.
Environmental impactsUnlike fossil fuel based technologies, solar power does not lead to any harmful emissions during operation, but the production of the panels leads to some amount of pollution. This is often referred to as the energy input to output ratio. In some analysis, if the energy input to produce it is higher than the output it produces it can be considered environmentally more harmful than beneficial. Also, placement of photovoltaics affects the environment. If they are located where photosynthesizing plants would normally grow, they simply substitute one potentially renewable resource (biomass) for another. It should be noted, however, that the biomass cycle converts solar radiation energy to electrical energy with significantly less efficiency than photovoltaic cells alone. And if they are placed on the sides of buildings (such as in Manchester) or fences, or rooftops (as long as plants would not normally be placed there), or in the desert they are purely additive to the renewable power base. Greenhouse gasesLife cycle greenhouse gas emissions are now in the range of 25-32 g/kWh and this could decrease to 15 g/kWh in the future.[68] For comparison, a combined cycle gas-fired power plant emits some 400 g/kWh and a coal-fired power plant 915 g/kWh and with carbon capture and storage some 200 g/kWh. Nuclear power emits 25 g/kWh on average; only wind power is better with a mere 11 g/kWh. Using renewable energy sources in manufacturing and transportation would drop photovoltaic emissions to zero. CadmiumOne issue that has often raised concerns is the use of cadmium in Cadmium telluride (CdTe) modules (CdTe is only used in a few types of PV panels). Cadmium in its metallic form is a toxic substance that has the tendency to accumulate in ecological food chains. The amount of cadmium used in thin-film PV modules is relatively small (5-10 g/m²) and with proper emission control techniques in place the cadmium emissions from module production can be almost zero. Current PV technologies lead to cadmium emissions of 0.3-0.9 microgram/kWh over the whole life-cycle.[68] Most of these emissions actually arise through the use of coal power for the manufacturing of the modules, and coal and lignite combustion leads to much higher emissions of cadmium. Life-cycle cadmium emissions from coal is 3.1 microgram/kWh, lignite 6.2, and natural gas 0.2 microgram/kWh. Note that if electricity produced by photovoltaic panels were used to manufacture the modules instead of electricity from burning coal, cadmium emissions from coal power usage in the manufacturing process could be entirely eliminated. Energy Payback Time and Energy Returned on Energy InvestedThe energy payback time is the time required to produce an amount of energy as great as what was consumed during production. The energy payback time is determined from a life cycle analysis of energy. Another key indicator of environmental performance, tightly related to the energy payback time, is the ratio of electricity generated divided by the energy required to build and maintain the equipment. This ratio is called the energy returned on energy invested (EROEI). Of course, little is gained if it takes as much energy to produce the modules as they produce in their lifetimes. This should not be confused with the economic return on investment, which varies according to local energy prices, subsidies available and metering techniques. Life-cycle analyses of the energy intensity of typical solar photovoltaic technologies in year 2000 find that the typical energy payback is around 7 years. Mounting and installation of the system adds a further 1 to 4 years, depending upon whether it is on a roof or in an open field. This gives a total energy payback time for a PV system of 8 to 11 years.[69] Another empirical study at Simens Solar factory finds that energy payback at 1700 kWh/m2/yr is 3-4 years for finished product including glass and aluminium for frames [70] Future PV panels that use thin films of crystalline silicon or other materials will have greatly reduced energy payback times. Such panels will be required if cost targets for large-scale production are to be met. The expected energy payback time will be in the vicinity of two years. Thin film technologies now have energy pay-back times in the range of 1-1.5 years (S.Europe).[68] With lifetimes of such systems of at least 30 years, the EROEI is in the range of 10 to 30. They thus generate enough energy over their lifetimes to reproduce themselves many times (6-31 reproductions, the EROEI is a bit lower) depending on what type of material, balance of system (or BOS), and the geographic location of the system.[71] Advantages
Disadvantages
Photovoltaics companies
Major photovoltaics companies include BP Solar, Isofoton, Kyocera, Q-Cells, Sanyo, Sharp Solar, SolarWorld, SunPower, Suntech, and Yingli Green Energy.[80][81][82] BP has been involved in solar power since 1973 and its subsidiary, BP Solar, is now one of the world's largest solar power companies with production facilities in the United States, Spain, India and Australia, employing a workforce of over 2,000 people worldwide.[83] BP Solar is a major worldwide manufacturer and installer of photovoltaic solar cells for electricity.[84] The company has begun constructing two new solar photovoltaic (PV) solar cell manufacturing plants, one at its European headquarters in Tres Cantos, Madrid, and the second at its joint venture facility, Tata BP Solar, in Bangalore, India.[85] Isofoton is a Spanish company that designs and manufactures high-efficiency monocrystalline silicon cells and panels, as well as concentrated photovoltaics (CPV). Isofoton is present in over 60 countries, having subsidiaries in America, Africa, Asia, and Europe. Kyocera Corporation has announced a plan to increase its solar cell production to 500 MW per year in 2010. 500 MW is about three times the current output of 180 MW, and the company will reinforce production bases in Japan, the US, Europe and China, investing a total of about ¥30 billion through FY2010. Through this production enhancement, Kyocera looks to meet increasing demand across the world for solar cells.[86][87] Nanosolar has been named Innovator of the Year for 2007 by Popular Science Magazine, in connection with its PowerSheet flexible solar film. Nanosolar manufactures PowerSheet by printing a solar-activated ink onto metal sheets in a low-cost, continuous process. Nanosolar is building a plant in San Jose, CA and one near Berlin, Germany. It promises to deliver solar film that will be low enough in cost to be at cost parity with power from the electrical grid. (add this company later) Q-Cells is the world's second largest cell manufacturer, based in Thalheim, Germany.[88] Renewable Energy Corporation (REC) is based in Norway, and was established in 1996. Over a relatively short period, REC has become the world's largest producer of polysilicon and wafers for PV applications. REC is involved in all steps of the value chain, from production of solar grade silicon to wafer, cell and module production. The company has customers all over the globe and seven production plants in three different countries. It operates on three different continents and has approximately 1,100 employees.[89] Sanyo Electric produced $213 million worth of solar cells at its plant in Hungary in 2006, and expects to triple its production capacity to 720,000 units in 2008.[90] Schott is one of the world largest producers of solar photovoltaic technologies. SCHOTT employs over 900 people and has worldwide production capacity of over 130 MW. Sharp Solar is the world's largest photovoltaic module and cell manufacturer, which manufactures in Japan, and near Wrexham, UK. Sharp Solar produces both single and multi-crystalline solar cells which are used for many applications, from satellites to lighthouses, and industrial applications to residential use. Sharp began researching solar cells in 1959 with mass production first beginning in 1963. Production capacity amounted to 324 MW in 2004.[91][92] SolarWorld is headquartered in Bonn, Germany, and purchased Shell Solar's crystalline silicon activities in 2006. SunPower Corporation designs and manufactures high-efficiency silicon solar cells and solar panels based on an all-back-contact "All-Black" design. They install them through their subsidiary PowerLight. Recent projects include the Nellis Solar Power Plant, the largest PV installation in North America. Suntech Power is based in Wuxi, China, where construction of a 1 GW module plant has begun. Year-end production capacity for 2007 is expected to be 480 MW.[93] Yingli Green Energy is currently one of the largest manufacturers of PV products in China, with an annual production capacity of 200 megawatts of polysilicon ingots and wafers, cells and PV modules, as of July 2007. Yingli Green Energy sells PV modules under its own brand name, Yingli Solar, to PV system integrators and distributors located in various markets around the world, including Germany, Spain, China and the United States. Photovoltaic Industry Associations
Photovoltaics research institutesThere are many research institutions and departments at universities around the world who are active in photovoltaics research. Countries which are particularly active include Germany, Spain, Japan, Australia, China, and the USA. Some universities and institutes which have a photovoltaics research department.
See also
ReferencesExternal links Publicly funded free data sources
Trade Press and commercial databases
Others
For more about PV on Wikipedia, Click here. (top) Solar thermal energy (From Wikipedia, the free encyclopedia)Solar thermal energy is a technology for harnessing solar energy for heat. Solar thermal collectors are characterized by the US Energy Information Agency as low, medium, or high temperature collectors. Low temperature collectors are flat plates generally used to heat swimming pools. Medium-temperature collectors are also usually flat plates but are used for creating hot water for residential and commercial use. High temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production. This is different from solar photovoltaics, which convert solar energy directly into electricity. Low-temperature collectorsOf the 21,000,000 square feet (2,000,000 m²) of solar thermal collectors produced in the United States in 2006, 16,000,000 square feet (1,500,000 m²) were of the low-temperature variety.[1] Low-temperature 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 its destination. Heating, cooling and ventilation
MIT's Solar House #1 built in 1939 utilized seasonal thermal storage for year round heating.
In the United States, heating, ventilation, and air conditioning (HVAC) systems account for over 25 percent (4.75 EJ) of the energy used in commercial buildings and nearly half (10.1 EJ) of the energy used in residential buildings.[2][3] Solar heating, cooling, and ventilation technologies can be used to offset a portion of this energy. Thermal mass materials store solar energy during the day and release this energy during cooler periods. Common thermal mass materials include stone, cement, and water. The proportion and placement of thermal mass should consider several factors such as climate, daylighting, and shading conditions. When properly incorporated, thermal mass can passively maintain comfortable temperatures while reducing energy consumption. 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. 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.[4] Solar roof ponds are a unique solar heating and cooling technology 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.[5] Active solar cooling can be achieved via absorption refrigeration cycles, desiccant cycles, and solar mechanical processes. In 1878, Auguste Mouchout pioneered solar cooling by making ice using a solar steam engine attached to a refrigeration device.[6] Thermal mass, smart windows and shading methods can also be used to provide cooling. The leaves of deciduous trees provide natural shade during the summer while the bare limbs allow light and warmth into a building during the winter. The water content of trees will also help moderate local temperatures. (top) Process heatEvaporation ponds are shallow ponds that concentrate dissolved solids through evaporation. The use of evaporation ponds to obtain salt from sea water is one of the oldest applications of solar energy. Modern uses include concentrating brine solutions used in leach mining and removing dissolved solids from waste streams. Altogether, evaporation ponds represent one of the largest commercial applications of solar energy in use today.[7] Unglazed transpired collectors (UTC) are perforated sun-facing walls used for preheating ventilation air. UTCs can raise the incoming air temperature up to 22 °C and deliver outlet temperatures of 45-60 °C. The short payback period of transpired collectors (3 to 12 years) make them a more cost-effective alternative to glazed collection systems. As of 2003, over 80 systems with a combined collector area of 35,000 m² had been installed worldwide. Representatives include an 860 m² collector in Costa Rica used for drying coffee beans and a 1300 m² collector in Coimbatore, India used for drying marigolds.[8][9] A food processing facility in Modesto, California uses parabolic troughs to produce steam used in the manufacturing process. The 5,000 m² collector area is expected to provide 4.3 GJ per year.[10] (top) Medium-temperature collectorsThese collectors could be used to produce approximately 50% of the hot water needed for residential and commercial use in the United States.[11] In the United States, a typical system costs $5000-$6000 and 50% of the system qualifies for a tax credit. With this incentive, the payback time for a typical household is nine years. A crew of one plumber and two assistants with minimal training can install two systems per week. The typical installation has negligible maintenance costs and reduces a households' operating costs by $6 per person per month. Solar water heating can reduce CO2 emissions by 1 ton/year (if replacing natural gas for hot water heating) or 3 ton/year (if replacing electric hot water heating).[12] Medium-temperature installations can use any of several designs: common designs are pressurized glycol, drain back, and batch systems. (top) 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.[13][14] Concentrating solar cookers use reflectors to concentrate light on 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 are used to produce steam that helps cook 2,000 daily meals.[15] Many other solar kitchen 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 450-650 °C.[16] Built in 1999, the world's largest Scheffler reflector system in Abu Road, Rajasthan India is capable of cooking up to 35,000 meals a day.[17] By early 2008, over 2000 large cookers of the Scheffler design had been built worldwide. (top) Disinfection and desalination
Solar water disinfection, also known as SODIS, is a simple method of disinfecting water using only sunlight and plastic PET bottles.[18] SODIS is a cheap and effective method for decentralized water treatment, usually applied at the household level and is recommended by the World Health Organization as a viable method for household water treatment and safe storage.[19] SODIS has over two million users in developing countries such as Brazil, Cameroon and Uzbekistan. A solar still uses solar energy to distill water. The main types are cone shaped, boxlike, and pit. The box shaped types are most sophisticated of these and the pit types the least sophisticated. In cone solar stills, impure water is inserted into the container, where it is evaporated by sunlight coming through clear plastic. Free of solids in suspension or solution, the water vapor condenses on top and drips down to the side, where it is collected and removed. (top) High-temperature collectors
Where temperatures below about 95°C are sufficient, as for space heating, flat-plate collectors of the nonconcentrating type are generally used. The fluid-filled pipes can reach temperatures of 150 to 220 degrees Celsius when the fluid is not circulating. This temperature is 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 this, 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 above 1100°C, using multi-stage turbine systems to achieve 60% thermal efficiencies. [20] 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 kilo 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 system that uses fossil energy. The back-up system can reuse most of the CSP plant, which decreases the cost of the back-up system. With reliability, unused desert, no pollution and no fuel costs, the only obstacle for large deployment for CSP is cost. Although only a small percentage 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. (top) System designsDuring the day the sun has different positions. If the mirrors or lenses do not move, then the focus of the mirrors or lenses changes. Therefore it seems unavoidable that there needs to be a tracking system that follows the position of the sun (for solar photovoltaics a solar tracker is only optional). The tracking system increases the cost. With this in mind, different designs can be distinguished in how they concentrate the light and track the position of the sun. (top) Parabolic trough designs
 Sketch of a parabolic trough design. A change of position of the sun parallel to the receiver does not require adjustment of the mirrors.
Parabolic trough power plants use a curved trough which reflects the direct solar radiation onto a receiver (also called absorber or collector) running along above the trough. The trough is parabolic in one direction and just straight in the other direction. For change of position of the sun orthogonal to the receiver, the whole trough tilts so that direct radiation remains focused on the receiver. However, a change of position of the sun parallel to the trough, does not require adjustment of the mirrors, since the light is just concentrated on another part of the receiver. So, the trough design avoids a second axis for tracking. A substance (also called heat transfer fluid) passes through the receiver and becomes hot. Used substances are synthetic oil, molten salt and pressurized steam. The receiver can be in a vacuum chamber of glass. The light will shine through the glass and vacuum, but the vacuum will significantly reduce convective loss of the collected heat. The substance with 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 is in full operation in California in the United States. It is called the SEGS system.[21] Other CSP designs lack this kind of long experience and therefore it can currently be said that the parabolic trough design is the only proven CSP technology. The Solar Energy Generating System (SEGS) is a collection of nine plants with a total capacity of 350MW. 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 64MW. Under construction are Andasol 1 and Andasol 2 in Spain with each site having a capacity of 50MW. Note however, that those plants have heat storage which requires a smaller (but better utilized) generator. With day and night operation Andasol 1 produces more energy than Nevada Solar One. 553MW new capacity is proposed in Mojava Solar Park, California.[22] Furthermore, 59MW hybrid plant with heat storage is proposed near Barstow, California [23]. Near Kuraymat in Egypt, some 40MW steam is used as input for a gas powered plant. [24][25] Finally, 25MW steam input for a gas power plant in Hassi R'mel, Algeria. [26] (top) Power tower designs
Power towers (also known as 'central tower' power plants or 'heliostat' power plants) use an array of flat, moveable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the receiver). 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 a hillside. 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 one axis can be shared for a large array of mirrors. A working tower power plant is PS10 in Spain with a capacity of 11MW. The 15MW Solar Tres plant with heat storage is under construction in Spain. In South Africa, a 100MW solar power plant is planned with 4000 to 5000 heliostat mirrors, each having an area of 140 m².[27] A 10MW power plant in Cloncurry Australia (with purified graphite as heat storage located on the tower directly by the receiver). [28] The company BrightSourceEnergy [29] has announced plans to build 500MW's worth of solar power plants, in 3 installations, in California with the Power Tower technology of Luz II. [30] Out of commission are the 10MW Solar One (later redeveloped and made into Solar Two) and the 2MW Themis plants. 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 ₡/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.[31] There is some hope that the development of cheap, durable, mass produceable heliostat power plant components could bring this cost down. [32] (top) Dish designs
A dish 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 to 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 [33]. 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 leads 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 dencentralized 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. [34] Stirling Energy Systems announced another agreement with San Diego Gas & Electric to provide between 300 and 900 megawatts of electricity.[35] However, as of October 2007 it was unclear whether any progress had been made toward the construction of the 1 MW test plant, which was supposed to come online some time in 2007. [36] [37] (top) 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 (CLFR[38]) and Belgium (SolarMundo). Furthermore a Fresnel-based prototype with direct steam generation was built by Solar Power Group in conjunction with the German Aerospace Center (DLR[39]). Based on the Australian prototype, a 177MW plant is proposed near San Luis Obispo in California and will be built by Ausra[40]. Plants with smaller capacities being an enormous economical challenge for plants with conventional parabolic trough and drive design, only few companies intend to build such small projects. Plans were revealed for former Ausra subsidiary SHP Europe building a 6.5 MW project in Portugal as a combined cycle plant. The German company SK Energy[41]]) has published its intention to build various small 1-3 MW plants in Southern Europe, esp. in Spain on the basis of their own Fresnel mirror and steam drive technology (Press Release[42]). A Multi-Tower Solar Array (MTSA) concept, that uses a point-focus Fresnel reflector idea, has also been developed,[43] but has not yet been prototyped. (top) Fresnel lensesPrototypes 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[44]. 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. (top) MicroCSP"MicroCSP" [45] 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 [46] but are smaller in collector size, lighter and operate at lower thermal temperatures usually below 600 degrees F. These systems are designed for modular field or rooftop installation where they are easy to protect from high winds, snow and humid deployments [47]. Solar manufacturer Sopogy is currently constructing a 1MW plant at the Natural Energy Laboratory of Hawaii [48] (top) Heat storageHeat storage allows a solar thermal plant to produce electricity at night and on overcast days. This allows the use of solar power for baseload generation as well as peak power generation, with the potential of displacing both coal and natural gas fired power plants. Additionally, the utilization of the generator is higher which reduces cost. Heat is transferred to a thermal storage medium in an insulated reservoir during the day, and withdrawn for power generation at night. Thermal storage media include pressurized steam, concrete, a variety of phase change materials, and molten salts such as sodium and potassium nitrate.[49][50] The PS10 solar power tower stores heat in tanks as pressurized steam at 50 bar and 285C. The steam condenses and flashes back to steam, when pressure is lowered. Storage is for one hour. It is suggested that longer storage is possible, but that has not been proven yet in an existing power plant. [51] The proposed power plant in Cloncurry Australia will store heat in purified graphite. The plant has a power tower design. The graphite is located on top of the tower. Heat from the heliostats goes directly to the storage. Heat for energy production is drawn from the graphite. This simplifies the design. [52] The Solar Tres power plant in Spain is expected to be the first commercial solar thermal power plant to utilize molten salt for heat storage and nighttime generation.[53] (top) Conversion rates from solar energy to electrical energyOf all of these technologies the solar dish/stirling engine has the highest energy efficiency. A single solar dish-Stirling engine installed at Sandia National Laboratories National Solar Thermal Test Facility produces as much as 25 kW of electricity, with a conversion efficiency of 30%.[54] Solar parabolic trough plants have been built with efficiencies of about 20%. Fresnel reflectors have an efficiency that is slightly lower (but this is compensated by the denser packing). The gross conversion efficiencies (taking into account that the solar dishes or troughs occupy only a fraction of the total area of the power plant) are determined by net generating capacity over the solar energy that falls on the total area of the solar plant. The 500-megawatt (MW) SCE/SES plant would extract about 2.75% of the radiation (1 kW/m²; see Solar power for a discussion) that falls on its 4,500 acres (18.2 km²).[55] For the 50 MW AndaSol Power Plant [56] that is being built in Spain (total area of 1,300×1,500 m = 1.95 km²) gross conversion efficiency comes out at 2.6% Furthermore, efficiency does not directly relate to cost: on calculating total cost, both efficiency and the cost of construction and maintenance should be taken into account. (top) Levelized costSince a solar power plant does not use any fuel, the cost consists mostly of capital cost with minor operational and maintenance cost. If the lifetime of the plant and the interest rate is known, then the cost per kWh can be calculated. This is called the levelized cost. The first step in the calculation is to determine the investment for the production of 1 kWh in a year. Example, the fact sheet of the Andasol 1 project shows a total investment of 310 million euros for a production of 179 GWh a year. Since 179 GWh is 179 million kWh, the investment per kWh a year production is 310 / 179 = 1.73 euro. Another example is Cloncurry solar power station in Australia. It produces 30 million kWh a year for an investment of 31 million Australian dollars. So, this price is 1.03 Australian dollar for the production of 1 kWh in a year. This is significantly cheaper than Andasol 1, which can partially be explained by the higher radiation in Cloncurry over Spain. The investment per kwh cost for one year should not be confused with the cost per kwh over the complete lifetime of such a plant. In most cases the capacity is specified for a power plant (for instance Andasol 1 has a capacity of 50MW). This number is not suitable for comparison, because the capacity factor can differ. If a solar power plant has heat storage, then it can also produce output after sunset, but that will not change the capacity factor, it simply displaces the output. The average capacity factor for a solar power plant, which is a function of tracking, shading and location, is about 20%, meaning that a 50MW capacity power plant will typically provide a yearly output of 50 MW x 24 hrs x 365 days x 20% = 87,600 MWh/year, or 87.6 GWh/yr. Although the investment for one kWh year production is suitable for comparing the price of different solar power plants, it doesn't give the price per kWh yet. The way of financing has a great influence on the final price. If the technology is proven, an interest rate of 7% [57] should be possible. However, for a new technology investors want a much higher rate to compensate for the higher risk. This has a significant negative effect on the price per kWh. Independent of the way of financing, there is always a linear relation between the investment per kWh production in a year and the price for 1 kWh (before adding operational and maintenance cost). In other words, if by enhancements of the technology the investments drop by 20%, then the price per kWh also drops by 20%. If a way of financing is assumed where the money is borrowed and repaid every year, in such way that the debt and interest decreases, then the following formula can be used to calculate the division factor: (1 - (1 + interest / 100) ^ -lifetime) / (interest / 100). For a lifetime of 25 years and an interest rate of 7%, the division number is 11.65. For example, the investment of Andasol 1 was 1.73 euro, divided by 11.65 results in a price of 0.15 euro per kWh. If one cent operation and maintenance cost is added, then the levelized cost is 0.16 euro. Other ways of financing, different way of debt repayment, different lifetime expectation, different interest rate, may lead to a significantly different number. If the cost per kWh may follow the inflation, then the inflation rate can be added to the interest rate. If an investor puts his money on the bank for 7%, then he is not compensated for inflation. However, if the cost per kWh is raised with inflation, then he is compensated and he can add 2% (a normal inflation rate) to his return. The Andasol 1 plant has a guaranteed feed-in tariff of 0.21 euro for 25 years. If this number is fixed, it should be realized that after 25 years with 2% inflation, 0.21 euro will have a value comparable with 0.13 euro now. Finally, there is some gap between the first investment and the first production of electricity. This increases the investment with the interest over the period that the plant is not active yet. The modular solar dish (but also solar photovoltaic and wind power) have the advantage that electricity production starts after first construction. Given the fact that solar thermal power is reliable, can deliver peak load and does not cause pollution, a price of 10[58] dollarcent starts to become competitive. Although a price of 6 dollarcent has been claimed [59] With some operational cost a simple target is 1 dollar (or lower) investment for 1 kWh production in a year. (top)
Grants
Current Funding Opportunities from NYSDERATechnical questions should be directed to the appropriate project managers. The main NYSERDA phone number is toll-free 1-866-NYSERDA or local (518) 862-1090; extensions and e-mail addresses for the project managers are listed below. Sign up to receive their e-mail updates for new Funding Opportunities
For more of these resources along with a lot of details about Private Resources, click here (grants start on pg. 26). From the New York State Energy Research and Development Authority: (top)
Can I install the system myself? How much will a system cost? I'm planning on building a new house, when is the best time to install a system on my roof? All Eligible PV Installers in or near NY**NABCEP-certified NABCEP-Certified Eligible Installers: The NABCEP PV installer certification is a voluntary certification that provides a set of national standards by which PV installers with skills and experience can distinguish themselves. These installers also meet the requirements to participate in NYSERDA's Solar Electric Incentive Program.
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On This Page:Grants/ NYSDERA funding options
About Photovoltaics:
About Solar Thermal Energy:
Related Wikipedia Entries:2.1 Architecture and urban planning 2.2 Agriculture and horticulture 3 Thermal and electrical storage 4 Development, deployment and economics (top)
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Howard Hall Farm in the 1700s Athens, NY |
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