Renewable energy technologies for rural development

most promising renewable energy technologies and new emerging renewable energy technologies
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Nataliebarry,New Zealand,Researcher
Published Date:13-07-2017
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a field guide to renewable energy technologies land art generator initiative Robert Ferry & Elizabeth Monoian other bio water wind solarABOUT THIS GUIDE The Land Art Generator Initiative provides a platform for innovative ways of thinking about what renewable energy generation looks like and how it relates to the overall fabric of our constructed and natural environments. It calls on interdisciplinary teams to conceive of large scale site-specific artworks that provide renewable electricity to the city at a utility-scale (equivalent to the demand of hundreds of homes). Once constructed, these public infrastructure artworks will offset thousands of tons of CO and 2 provide iconic amenities that will serve to educate and inspire the communities in which they are built. As a part of the Land Art Generator Initiative, we have put together this field guide of renewable energy generation technologies as a useful resource for all designers, homeowners, urban planners, students, artists, architects and landscape architects, engineers, and anyone else interested in a clean energy future. There is a lot more out there than what we see in the everyday. In fact, you will see in this guide that there are dozens of proven methods of harnessing the power of nature in sustainable ways. Some of the more interesting examples that may be applicable as a medium for public art installations are the organic thin films which are flexible and offer interesting hues and textures, piezoelectric generators that capture vibration energy, and concentrated photovoltaics, which allow for interesting play with light. But the possibilities are endless, and new designs that can be artistically integrated into residential and commercial projects are coming into the market all the time. It is our hope that this field guide will get you thinking creatively about ways to use technologies in innovative contexts—and that a clear understanding of the wealth of possibilities that are out there will help designers to conceive of the most creative net zero energy constructions. a field guide to renewable energy technologies land art generator initiative other bio water wind solarTHERMAL DIRECT NON-CONCENTRATING Solar thermal collectors can be mounted on the roof or the wall of a building, or in energy output CONVERSION = = 45%–75% another location that has EFFICIENCY energy input Depending on system type exposure to the sun. & operating temperature Solar combisystems: solar thermal is often used in combination with other energy-saving techniques such as ground source heat (geosolar systems), and solar thermal cooling (absorption refrigeration). One large installation can be used for “district heating” of multiple buildings. EVACUATED TUBE SYSTEM Photo provided by Lumen Solar, courtesy of Apricus Solar Hot Water. Solar thermal is any installation in which solar radiation is used to heat a medium such as water or air. Water can be for direct use in the domestic plumbing system of a building and for radiant floor heating (instead of relying on natural gas or grid source electricity that is most likely generated from fossil fuels to heat the water). These systems typically utilize either flat plate or evacuated tube collection systems. Solar heated water can serve as an energy storage mechanism to create thermal heat lag within occupied space such as with a trombe wall. Other systems that can help heat occupied space rely on air rather than water. The air is circulated through a cavity that is exposed to direct sunlight on the exterior of a building. A very simple example of thermal energy is a greenhouse where the entire building acts as the solar energy collection device. 1 a field guide to renewable energy technologies land art generator initiative solarTHERMAL SOLAR POND (SALTWATER) A defining characteristic of a highly saline body of water is that it naturally stratifies energy output CONVERSION = = 10% into three layers of salinity. EFFICIENCY energy input At the surface is a layer of low salinity and at the bottom is a layer of very high salinity. In between there is Rankine-cycle electrical generator an intermediate insulating layer that keeps a heat exchange convention cycle heat exchanger tubes liner from forming. When exposed to solar radiation, heat is trapped in the bottom of the salt water pond where temperatures salt gradient layer wind protection can reach nearly 100°C while lower salt and cooler water water at the surface is 30°C. high salt content hot brine SOLAR POND The heat that is trapped at the bottom of a saltwater pond can be harnessed to power an organic Rankine cycle turbine or a Stirling engine, both of which convert heat into electricity without steam (does not require temperatures in excess of H O boiling point). 2 Via the Organic Rankine Cycle (ORC), water is piped to an evaporator coil that heats a low-boiling-point fluid to pressurized vapor, driving a turbine. The vapor then passes to a condenser, where water from the top layer of the pond is used to cool the fluid back into liquid form after which it is then pumped back to the evaporator (with energy from a PV panel on-site). Because salt water is an excellent thermal heat sink, the solar pond produces electricity 24 hours per day regardless of weather conditions. Efficiency is greater in climates that receive higher average solar irradiance. 2 a field guide to renewable energy technologies land art generator initiative solarTHERMAL CONCENTRATED (CSP) PARABOLIC TROUGH As of 2010, CSP (concentrated solar power) plants in operation in energy output CONVERSION = = 25% the USA met the needs of EFFICIENCY energy input over 350,000 people and displaced the equivalent of 2.3 million barrels of oil annually. Utility-scale CSP typically requires large tracts of land, but “Micro CSP” systems can be designed for installation on building rooftops. SEGS POWER PLANT AT KRAMER JUNCTION IN THE MOJAVE DESERT Owned and operated by FPL Energy. Image via Desertec-UK. The concentrated parabolic trough design is one of the most common types of solar power systems in application for utility-scale electricity generation. It consists of a series of long, highly polished parabolic reflecting surfaces that focus sunlight onto an absorber tube running along the focal point of the parabola. A heat transfer fluid (typically an oil) runs through the tube and is heated to approximately 400°C to provide the thermal energy required to run a steam turbine. The parabolic shape of the reflector allows the troughs to be oriented on a north-south axis and track the sun in only one rotational axis from east to west each day. Highly polished metals are often used as the reflector material since parabolic curved mirrors can be complex to manufacture. 3 a field guide to renewable energy technologies land art generator initiative solarTHERMAL CONCENTRATED (CSP) LINEAR FRESNEL REFLECTOR (LFR OR CLFR) Fresnel geometry allows flat surfaces to act in a way that mimics convex or concave energy output CONVERSION = = 20% mirror or lens optics. EFFICIENCY energy input It was originally developed by French physicist Augustin-Jean Fresnel for use in lighthouses. In a Fresnel reflector, a parabolic mirror is simulated in a segmented or “Fresnel” arrangement of flat mirrors. KIMBERLINA POWER PLANT IN BAKERSFIELD, CALIFORNIA Image courtesy of AREVA Solar. Linear Fresnel Reflectors (LFR) use long, thin segments of flat mirrors to focus sunlight onto a fixed absorber located at a common focal point of the reflectors. Absorbers in LFR often contain multiple heat transfer tubes. Similar to the more common parabolic trough, this single-axis tracking concentrated reflector system heats up a transfer fluid which in turn heats water to run a steam turbine (in the case of LFR, temperatures in the transfer fluid can reach 750°C although 300°C is more common). One advantage of LFR is that the reflector mirrors are flat rather than parabolic in shape, which makes for a simpler mirror manufacturing process. Systems can be set up to focus sunlight onto a single absorber (LFR) or onto multiple absorbers which is referred to as a Compact Linear Fresnel Reflector (CLFR) system. CLFR design is obtained by alternating the angle of each reflector. This can lead to greater energy conversion efficiency of the overall system. 4 a field guide to renewable energy technologies land art generator initiative solarTHERMAL CONCENTRATED (CSP) DISH STIRLING The Stirling Engine is a type of external combustion engine of the reciprocating piston energy output CONVERSION = = 31.25% variety. It is named after EFFICIENCY energy input Robert Stirling, who in 1816 invented the closed-cycle air engine. The engine works on the principle that gas expands as its temperature increases. Expansion and contraction cycles will move a piston back and forth within a closed chamber. A magnetic piston moving through an electromagnetic field becomes a linear alternator, thus producing electric current. STIRLING ENERGY SYSTEMS At the Sandia National Laboratories in Albuquerque, New Mexico. Dish type collectors look sort of like television satellite receivers in their shape. They are parabolic, but unlike a linear parabola that concentrates along an axis, these are dish parabolas that concentrate light onto a single point. They can be one large dish, or an array of smaller reflectors as in the photo above. They must rotate on a dual-axis to track the sun’s position in the sky. At the single focal point is typically situated a Stirling Engine which converts heat into mechanical energy with high efficiency. The mechanical energy is then converted to electricity with a dynamo. This type of concentrated solar thermal electricity installation rivals the best efficiencies of concentrated photovoltaic systems per similar land area and relies on more simple mechanical technologies as opposed to semiconductors and microelectronics. Some CPV installations also utilize dish type collectors (refer to page 18). 5 a field guide to renewable energy technologies land art generator initiative solarTHERMAL CONCENTRATED (CSP) SOLAR POWER TOWER Solar power towers require a large amount of land in order to achieve sufficient operating energy output CONVERSION = = 25% temperature (500°C–1000°C) EFFICIENCY energy input in the central receiver. The overall efficiency of the system can rise as receiver temperature increases. Higher receiver temperature can allow for thermal storage, making it possible for this type of CSP power plant to generate consistent energy for baseload supply 24 hours a day (up to 17 hours of continuous electrical generation without solar feed). GEMASOLAR POWER PLANT IN SPAIN Owned by Torresol Energy (joint venture of SENER and MASDAR). Image courtesy of Torresol Energy. In this type of concentrated solar thermal power, an array of mirrors at the ground level tracks the sun’s location in the sky and focuses sunlight onto a single collector positioned high atop a central tower pylon structure. The temperatures reached at the collector can become extremely high and create efficiencies of scale. By using a high heat capacity material such as molten salt in the collector (which transfers heat to water to run a steam turbine) energy can be stored to produce electricity even after the sun has set. Another variation, the beam-down tower, was recently demonstrated by Masdar in Abu Dhabi. Beam-down design allows the entire heat transfer loop to be located at ground level, potentially increasing the overall efficiency of the system. Other design variations include a pit-power tower for a stadium mirror array (University of Queensland), and integrated applications on buildings such as those by Studied Impact Design (10MW Tower for Dubai). 6 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAICS ALL TYPES The photovoltaic effect, first recognized by A. E. Becquerel in 1839, is the ability of a energy output CONVERSION = = 3%–42.5% material (a semiconductor) EFFICIENCY energy input to produce direct current electricity when exposed to solar radiation. It is related to the photoelectric effect, which is the ejection of an electron from a material substance by electromagnetic radiation incident on its surface. However, in the photovoltaic effect, the electrons remain within the material, creating positive and negative bands which can be harnessed by an electrical circuit. MONOCRYSTALLINE SILICON PHOTOVOLTAIC ARRAY Image courtesy of Siemens AG, Munich/Berlin. Although the photovoltaic (PV) effect was demonstrated in various laboratory applications throughout the 19th century, it was not until 1954 that the first commercially viable application of the technology was demonstrated by Bell Laboratories. Throughout the PV section we will discuss conversion efficiency. A good rule of thumb is that one square meter surface area (at sea level and perpendicular to the sun on a clear day) will typically receive 1000 watts of solar radiation energy (insolation = 1000W irradiance/square meter). This measure will vary slightly according to latitude, time of day, and season. The conversion efficiency is how many of those 1000 watts can be converted to electrical energy. A 20% efficient solar panel will have a 200W(p) capacity. The (p) stands for peak, nameplate, or rated capacity, and the panel will not always reach this level of output during field operation. The ratio between the rated capacity and the real measured output is the “capacity factor.” Many environmental factors such as heat build-up, humidity, surface dust, and airborne particulates can contribute to a lower capacity factor in field applications. 7 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC CRYSTALLINE SILICON WAFER Silicon is the most common metalloid found in nature. It is typically found as silica energy output CONVERSION = = 18%–23% (SiO ) in sands rather than 2 EFFICIENCY energy input in its pure elemental form. Silicon makes up 27.7% of the earth’s crust by mass. Molten salt electrolysis can create pure silicon from silica with low energy input and without CO emissions. 2 More commonly, high temperature furnaces (1,900°C) create the condition in which silica is converted via reaction with carbon into pure silicon. SiO + 2 C - Si + 2 CO 2 POLYCRYSTALLINE SILICON SOLAR PANEL Photo by Scott Robinson. Silicon (Si) is a semiconductor material that displays the photovoltaic effect. It was the first material to be employed in solar cells and is still the most prevalent. It can be applied for use in either a crystalline (wafer) form, or in a non-crystalline (amorphous) form. There are two types of crystalline silicon (c-Si): monocrystalline and polycrystalline (aka multicrystalline). Monocrystalline is expensive to manufacture (because it requires cutting slices from cylindrical ingots of silicon crystals that are grown with the Czochralski process) but it is the most efficient crystalline silicon technology in terms of energy conversion. Polycrystalline is easier to manufacture and can be cut into square shaped slices, but has slightly lower efficiency (approximately -5%). It is comprised of small crystals or crystallites. 8 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC THIN FILM SILICON The efficiencies that are gained in the manufacturing process of thin film energy output CONVERSION = = 12% photovoltaics often times EFFICIENCY energy input more than offset the reduced conversion efficiency of the panels when figured over the life-cycle of the system. PHOTOVOLTAIC INSTALLATION REAL GOODS SOLAR LIVING CENTER IN HOPLAND, CALIFORNIA Photo by Cris Benton. Amorphous silicon (a-Si) is less expensive to produce than either mono or poly-crystalline silicon. It is non-crystalline, meaning that the atomic structure is more randomized. While it operates at a lower efficiency than crystalline structures (about half the efficiency of monocrystalline Si), it can be placed in much thinner applications which can lead to a lower cost per watt capacity of the solar cell design. Other types of thin film silicon are protocrystalline and nanocrystalline (aka microcrystalline). Some variations that combine layers of different types of thin film silicon have been referred to as micromorph (a combination of the terms MICROcrystalline and aMORPHous). 9 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC THIN FILM NON-SILICON The levelized cost of energy for non-silicon systems when compared to silicon-based PV energy output CONVERSION = = 16%–20% depends greatly on the global EFFICIENCY energy input market cost of silicon at the time of manufacture. Silicon is more abundant in nature than CIGS or CdTe raw materials. However, during periods of high global demand, silicon can sometimes cost more as a raw material. Each semi-conductor material captures light energy most efficiently across a limited wavelength spectrum. SEMPRA GENERATION’S CDTE COPPER MOUNTAIN SOLAR FACILITY Image courtesy of Sempra U.S. Gas & Power, LLC. As an alternative to silicon (Si), other semiconductor materials can be used for thin film solar cells. They have been proven to have greater efficiency than thin film amorphous silicon. Copper-Indium Gallium Selenide (CIGS) has a conversion efficiency of about 20%. It can be manufactured to be very thin due to its high absorption coefficient. Cadmium Telluride (CdTe) has a conversion efficiency of about 16% and potentially offers cost advantages over CIGS. The company Nanosolar has developed a method of printing CIGS onto thin foil substrates with nanoparticle inks and roll-to-roll manufacturing, which allows for flexible thin film panels while reducing production costs. Image courtesy of Nanosolar. 10 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC MULTIJUNCTION Also called “tandem cells,” these specialized type of solar cells have been limited to use energy output CONVERSION = = 25%–45% in aerospace, CPV, or other EFFICIENCY energy input unique applications due to their complexity and expense. Multijunction cells are capable of achieving high conversion efficiencies because they are able to capture electrons within multiple wavelengths of light. Single junction cells are limited to the energy within a partial spectrum, the remaining light either reflecting off or being lost to heat energy. MULTIJUNCTION CELL Multijunction cells take advantage of multiple materials, each of which best capture a particular light wavelength (color spectrum) for solar-to- electricity conversion. This can lead to very high conversion efficiencies, even above 40%. The technology was first developed for use in space explorations such as the Mars rover missions, and is still used for space applications. Because of the manufacturing expense, terrestrial commercial application has been generally limited to CPV systems (refer to page 18). Different techniques use different substrate materials and can be either two-junction or three-junction. Some substrate materials that are used are: Gallium arsenide, Germanium, and Indium phosphide. Because the thin film is deposited (epitaxially) onto a monocrystalline substrate, the applied layers take on the lattice structure of the substrate crystal while maintaining thin film properties. 11 a field guide to renewable energy technologies land art generator initiative solarPHOTOELECTROCHEMICAL CELL (PEC) One of the technical obstacles to greater proliferation of PEC-type energy output CONVERSION = = 10% electrolysis for hydrogen EFFICIENCY energy input generation is the corrosive effect of the electrolyte solution on the semiconductor anode. PROOF-OF-CONCEPT BY PROFESSOR MICHAEL STRANO ET AL. Image courtesy of MIT. Photo by Patrick Gillooly. These are solar cells that transform solar energy directly into electrical energy. Instead of using a solid-state semiconductor as the light absorbing material, PECs use a electrolyte material (typically a fluid). A circuit is created via a semiconducting anode and a metal cathode which are both in contact with the electrolyte. One type of PEC is the DSSC (dye-sensitized solar cell). More about DSSC can be found on page 13. Other types of PEC can be used to harness solar energy directly for purposes of electrolysis to create hydrogen—a stored fuel. In this system, water acts as the electrolyte solution. Hydrogen and oxygen form around the anode when exposed to sunlight. The resulting hydrogen can be stored and used to generate electricity in fuel cells. An example of this technology in action is the work by Rose Street Labs Energy (RSLE) scientists in Phoenix, Arizona. 12 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC THIN FILM DYE-SENSITIZED (DSSC) Because of the existence of liquid electrolyte within the DSSC cells, the temperature energy output CONVERSION = = 9%–11% must be maintained within EFFICIENCY energy input certain bounds. The liquid also acts as a solvent over time. This, and the volatility of the dyes under UV light, mean that details of the material housing assembly are critical. Research is underway to replace the liquid with a solid material. DSSC MODULE Techniques for creating dye-sensitized solar cells (DSSC) are simple and the materials are very low cost, but the conversion efficiency is also below that of solid-state semiconductor technologies (DSSC is the most efficient of the “third generation” thin films). This technique was invented in 1991 by Michael Grätzel and Brian O’Regan at EPFL. The DSSC solar cell is alternatively known as the Grätzel cell. They have the characteristic of being semi-transparent, flexible, and are very durable. They also function comparatively better than other PV technologies in low light levels and indirect light. Because they are relatively inexpensive to produce they have one of the lowest price/ performance ratios, and despite their lower conversion efficiency are therefore competitive with conventional energy in terms of levelized cost (price per KWh over the lifetime of the installation). The Dye Solar Cell (DSC) modules (tiles) used in the window systems installed at Seoul City’s Human Resource Development Centre, were produced and supplied by Dyesol Limited’s Korean joint venture partner, Timo Technology, using Dyesol DSC materials. 13 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC THIN FILM ORGANIC PHOTOVOLTAIC CELL (OPVC) OR POLYMER SOLAR CELL Organic thin film has some advantages over silicon or other semi-conductor type energy output CONVERSION = = 5%–10% solar cells. EFFICIENCY energy input Its organic and plastic nature means that it can be easily fabricated into flexible shapes and adhered to fabrics. It functions well under low light conditions and at non- perpendicular angles to the sun such as vertical walls. Its translucency means that it can also be applied to windows and other light transmitting surfaces. ORGANIC PHOTOVOLTAIC PLASTIC SHEET Similar to that produced by Heliatek, Solarmer, Eight19, and Disasolar. OPVC (or OPV) uses organic polymers to absorb sunlight and transmit electrical charges. Organic PV can be manufactured in solutions that can be painted or rolled onto proper substrate materials. They can be produced at a very low cost in comparison to other PV technologies because they can take advantage of roll-to-roll production techniques in which the organic photovoltaic system is “printed” onto a continuous sheet of substrate material. Current OPVC technology has a conversion efficiency of up to 10%. Its low cost of production, its flexibility, and its good performance in lower level and indirect light make it an attractive option for some applications. Examples of small-scale uses for OPVC can be seen sewn into fabric such as in backpacks, laptop cases, tents, and jackets. The energy generated by a backpack utlizing this technology, for example, is sufficient to charge portable electronic devices and to provide power to one or two lights. OPV is finding interesting applications in developing countries. A great example is the IndiGo 2.5KW system by Eight19 that is being provided to off-grid communities, financed via mobile phone SMS credit codes. Larger-scale applications, such as building integrated OPV in façade systems are also being implemented. 14 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC 3D CELLS One application of 3D photovoltaics is the research that is being done at Georgia energy output CONVERSION = = 26%–50% Tech. They are coating EFFICIENCY energy input optical fibre cable with dye- sensitized solar cells in an STILL IN THE RESEARCH STAGE OF DEVELOPMENT effort to increase the amount of light transmission to photovoltaic material over any given surface area exposed to the sun. A project at CalTech also shows promise with a flexible array of light-absorbing silicon microwires and light- reflecting metal nanoparticles embedded in a polymer. 3D SOLAR CELL These solar cells can utilize any of the various PV material designs. The initial focus by the company 3D Solar has been on integrating conventional silicon-based PV as the photovoltaic material. The technological innovation lies in the initial capture of light at the surface of the solar panel. Whereas a standard panel solar cell will typically reflect 20%–30% of the light that strikes its surface, a 3D cell relies on a geometric structure that can recapture the reflected light onto adjacent PV surfaces, thus increasing the efficiency of the entire system over the same surface area of installation. Use of multijunction technology in combination with 3D solar cell geometry has the potential to see applications in CPV systems with an energy conversion efficiency of 50% or greater. Plasmonic solar cells (PSC) use nanoparticles on the surface of a solar cell to scatter and trap more light within the cell. 15 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC INFRARED AND UV Because infrared and ultraviolet light is outside of the spectrum of human sight, energy output CONVERSION = = UP TO 90% these type of photovoltaic EFFICIENCY energy input panels could function very well as window surfaces, STILL IN THE RESEARCH STAGE OF DEVELOPMENT while still letting in the entire visible spectrum and reducing internal building heat gain at the same time. This technology is still mostly in the research stage and is not yet commercially available. 2μm NANOANTENNA STRUCTURE CAPTURES IR SPECTRUM RADIATION Image courtesy of Idaho National Laboratory. Experimental research is ongoing to develop methods of converting infrared and UV light into electrical power. Since infrared solar radiation energy is radiated back from the earth during the night, a system to capture it could potentially provide energy 24 hours a day. A team of researchers at Idaho National Laboratory, the University of Missouri, and the University of Colorado are working to develop nanoantennas (nantenna) that can collect both solar heat energy and industrial waste heat energy. The flexible film would be able to convert up to 90% of available light across multiple spectrums. Since UV and infrared light is beyond the visible spectrum, solar panels that focus on these spectrums can let visible light through while still harnessing solar energy. Japan’s National Institute of Advanced Industrial Science and Technology has shown proof of concept applications of this type of technology. 16 a field guide to renewable energy technologies land art generator initiative solarTHERMOPHOTOVOLTAIC (TPV) Potential exists with TPV to see significant increases in the overall efficiency of solar energy output CONVERSION = = Greater than 50% power systems by converting EFFICIENCY energy input PV + TPV (theoretical) residual heat energy that is otherwise wasted. Image courtesy of IMEC. TPV converts heat energy directly into electricity via photons. A TPV system consists of a thermal emitter and a photovoltaic diode. For the most efficient operation, the temperature of the thermal emitter should be about 1000°C above the temperature of the photovoltaic diode cell, but some amount of energy could be created from smaller differences in temperature. TPV employs photovoltaic technology but does not necessarily rely on the sun as the emitter of the photon energy. 17 a field guide to renewable energy technologies land art generator initiative solarPHOTOVOLTAIC CONCENTRATED PV (CPV) LOW (LCPV) = 2–100 SUNS HIGH (HCPV) = 300–1000 SUNS Some CPV systems employ parabolic troughs that direct sunlight onto a linear solar cell. energy output CONVERSION = = UP TO 42% EFFICIENCY energy input Another design is the Total Spectrum Collector which separates light with a prism into different spectrums best suited to different solar cell types. Still another variation is the mylar balloon design developed by Cool Earth in which a CPV solar cell at the upper side of a clear hemisphere receives concentrated sunlight from the lower hemisphere which is highly reflective on the inside surface. CONCENTRATED PV Image courtesy of SolFocus, Inc. CPV employs photovoltaic cells, but rather than rely on the standard intensity of naturally occurring solar radiation energy, the CPV system concentrates the sunlight and directs a magnified beam onto a smaller area solar cell specifically designed to handle the greater energy and heat. Because the solar cell can be much smaller, the amount of semiconductor material required is far less for the same watt capacity output when compared to non-concentrated PV systems. This can greatly reduce the construction cost per watt capacity of the overall system. Because of the increased heat on the solar cell, CPV installations often require the integration of heat sinks or other cooling apparatus. The magnification of the sunlight can be accomplished by a number of methods, the most common of which is a Fresnel lens. Other designs, such as that of SolFocus and Cool Earth, utilize reflectors. Nearly all CPV systems must track the sun’s movement across the sky in order to function properly. CPV can reach the greatest installed efficiencies of existing PV installations for utility-scale applications. 18 a field guide to renewable energy technologies land art generator initiative solar

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