1. 1. Solar EnergyGreen Energy For Green Renovation PDF generated using the open source mwlib toolkit. See http://code.pediapress.com/ for more information.PDF generated at: Wed, 16 May 2012 13:50:17 UTC
2. 2. ContentsArticles Sunlight1 Solar energy8 Solar thermal energy 24 Solar thermal collector41 Photovoltaics50 Photovoltaic system61 Active solar 72 Passive solar building design73 Daylighting86 Hybrid solar lighting92 Daylight saving time 93 Concentrated solar power112 Air mass (solar energy) 118 Thermal mass124 Thermal energy storage128 Solar water heating 131 Solar combisystem 151 Solar architecture154 Solar chimney 154 Solar air conditioning159 Solar water disinfection164 Solar desalination170 Solar Powered Desalination Unit 172 Solar cooker173 Solar pond184 Salt evaporation pond 186 Solar furnace 188 Solar power 190 Solar chemical199 Solar vehicle 200 Solar balloon 207 Solar sail211 Solar power by country226 Solar lamp236
3. 3. Solar tracker237 SolarEdge248 Solar inverter 251 Soil solarization256 Space-based solar power257 Sustainable energy 272 Community solar farm 285 Urban heat island288References Article Sources and Contributors 297 Image Sources, Licenses and Contributors 303Article Licenses License309
4. 4. Sunlight 1Sunlight "Sunshine" redirects here. For natural lighting of interior spaces by admitting sunlight, see Daylighting. For solar energy available from sunlight, see Insolation. For other uses, see Sunlight (disambiguation) and Sunshine (disambiguation).Sunlight, in the broad sense, is the total frequencyspectrum of electromagnetic radiation given off by theSun, particularly infrared, visible, and ultraviolet light.On Earth, sunlight is filtered through the Earthsatmosphere, and solar radiation is obvious as daylightwhen the Sun is above the horizon.When the direct solar radiation is not blocked by clouds,it is experienced as sunshine, a combination of brightlight and radiant heat. When it is blocked by the clouds orreflects off of other objects, it is experienced as diffusedlight.The World Meteorological Organization uses the term"sunshine duration" to mean the cumulative time duringwhich an area receives direct irradiance from the Sun ofat least 120 watts per square meter.[1]Sunlight may be recorded using a sunshine recorder,pyranometer or pyrheliometer. Sunlight takes about 8.3minutes to reach the Earth.On average, it takes energy between 10,000 and 170,000 Sunlight shining through clouds, giving rise to crepuscular rays.years to leave the suns interior and then be emitted fromthe surface as light.[2]Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux. Bright sunlight providesilluminance of approximately 100,000 lux or lumens per square meter at the Earths surface.Sunlight is a key factor in photosynthesis, a process vital for many living beings on Earth.CompositionThe spectrum of the Suns solar radiation is close to that of a blackbody with a temperature of about 5,800K.[3] The Sun emits EMradiation across most of the electromagnetic spectrum. Although theSun produces Gamma rays as a result of the nuclear fusion process,these super high energy photons are converted to lower energy photonsbefore they reach the Suns surface and are emitted out into space. As aresult, the Sun doesnt give off any gamma rays. The Sun does,however, emit X-rays, ultraviolet, visible light, infrared, and even radiowaves.[4] When ultraviolet radiation is not absorbed by the atmosphere Solar irradiance spectrum above atmosphere andor other protective coating, it can cause damage to the skin known as at surfacesunburn or trigger an adaptive change in human skin pigmentation.
5. 5. Sunlight 2The spectrum of electromagnetic radiation striking the Earths atmosphere spans a range of 100 nm to about 1 mm.This can be divided into five regions in increasing order of wavelengths:[5] Ultraviolet C or (UVC) range, which spans a range of 100 to 280nm. The term ultraviolet refers to the fact thatthe radiation is at higher frequency than violet light (and, hence also invisible to the human eye). Owing toabsorption by the atmosphere very little reaches the Earths surface (Lithosphere). This spectrum of radiation hasgermicidal properties, and is used in germicidal lamps. Ultraviolet B or (UVB) range spans 280 to 315nm. It is also greatly absorbed by the atmosphere, and along withUVC is responsible for the photochemical reaction leading to the production of the ozone layer. Ultraviolet A or (UVA) spans 315 to 400nm. It has been traditionally held as less damaging to the DNA, andhence used in tanning and PUVA therapy for psoriasis. Visible range or light spans 380 to 780nm. As the name suggests, it is this range that is visible to the naked eye. Infrared range that spans 700nm to 106 nm (1 mm). It is responsible for an important part of the electromagneticradiation that reaches the Earth. It is also divided into three types on the basis of wavelength: Infrared-A: 700nm to 1,400nm Infrared-B: 1,400nm to 3,000nm Infrared-C: 3,000nm to 1mmCalculationTo calculate the amount of sunlight reaching the ground, both the elliptical orbit of the Earth and the attenuation bythe Earths atmosphere have to be taken into account. The extraterrestrial solar illuminance (Eext), corrected for theelliptical orbit by using the day number of the year (dn), is given by[6]where dn=1 on January 1; dn=2 on January 2; dn=32 on February 1, etc. In this formula dn-3 is used, because inmodern times Earths perihelion, the closest approach to the Sun and therefore the maximum Eext occurs aroundJanuary 3 each year. The value of 0.033412 is determined knowing that the ratio between the perihelion (0.98328989AU) squared and the aphelion (1.01671033 AU) squared should be approximately 0.935338.The solar illuminance constant (Esc), is equal to 128103 lx. The direct normal illuminance (Edn), corrected for theattenuating effects of the atmosphere is given by:where c is the atmospheric extinction coefficient and m is the relative optical airmass.Solar constantThe solar constant, a measure of flux density, is the amount of incoming solar electromagnetic radiation per unitarea that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) (roughlythe mean distance from the Sun to the Earth). The "solar constant" includes all types of solar radiation, not just thevisible light. Its average value was thought to be approximately 1.366kW/m,[7] varying slightly with solar activity,but recent recalibrations of the relevant satellite observations indicate a value closer to 1.361kW/m is morerealistic.[8]
6. 6. Sunlight 3Total (TSI) and spectral solar irradiance (SSI) upon EarthTotal Solar Irradiance upon Earth (TSI) was earlier measured by satellite to be roughly 1.366 kilowatts per squaremeter (kW/m),[7][9][10] but most recently NASA cites TSI as "1361 W/m as compared to ~1366 W/m from earlierobservations [Kopp et al., 2005]", based on regular readings from NASAs Solar Radiation and ClimateExperiment(SORCE) satellite, active since 2003,[11] noting that this "discovery is critical in examining the energybudget of the planet Earth and isolating the climate change due to human activities." Furthermore the SpectralIrradiance Monitor (SIM) has found in the same period that spectral solar irradiance (SSI) at UV (ultraviolet)wavelength corresponds in a less clear, and probably more complicated fashion, with earths climate responses thanearlier assumed, fueling broad avenues of new research in "the connection of the Sun and stratosphere, troposphere,biosphere, ocean, and Earths climate".[11]Intensity in the Solar SystemDifferent bodies of the Solar System receive light of an intensity inversely proportional to the square of theirdistance from Sun. A rough table comparing the amount of solar radiation received by each planet in the SolarSystem follows (from data in [12]): Planet Perihelion - Solar radiation Aphelionmaximum and distance (AU) minimum (W/m)Mercury 0.3075 0.466714,446 6,272Venus 0.7184 0.72822,647 2,576Earth 0.9833 1.017 1,413 1,321Mars1.382 1.666715 492Jupiter 4.950 5.45855.8 45.9Saturn9.048 10.1216.7 13.4Uranus18.38 20.084.04 3.39Neptune 29.77 30.441.54 1.47The actual brightness of sunlight that would be observed at the surface depends also on the presence andcomposition of an atmosphere. For example Venus thick atmosphere reflects more than 60% of the solar light itreceives. The actual illumination of the surface is about 14,000 lux, comparable to that on Earth "in the daytime withovercast clouds".[13]Sunlight on Mars would be more or less like daylight on Earth wearing sunglasses, and as can be seen in the picturestaken by the rovers, there is enough diffuse sky radiation that shadows would not seem particularly dark. Thus itwould give perceptions and "feel" very much like Earth daylight.For comparison purposes, sunlight on Saturn is slightly brighter than Earth sunlight at the average sunset or sunrise(see daylight for comparison table). Even on Pluto the sunlight would still be bright enough to almost match theaverage living room. To see sunlight as dim as full moonlight on the Earth, a distance of about 500 AU (~69light-hours) is needed; there are only a handful of objects in the solar system known to orbit farther than such adistance, among them 90377 Sedna and (87269) 2000 OO67.
7. 7. Sunlight 4Surface illuminationThe spectrum of surface illumination depends upon solar elevation due to atmospheric effects, with the blue spectralcomponent from atmospheric scatter dominating during twilight before and after sunrise and sunset, respectively,and red dominating during sunrise and sunset. These effects are apparent in natural light photography where theprincipal source of illumination is sunlight as mediated by the atmosphere.According to Craig Bohren, "preferential absorption of sunlight by ozone over long horizon paths gives the zenithsky its blueness when the sun is near the horizon".[14]See diffuse sky radiation for more details.Climate effectsFurther information: Solar variation,Solar dimming,andInsolationOn Earth, solar radiation is obvious as daylight when the sun is above the horizon. This is during daytime, and alsoin summer near the poles at night, but not at all in winter near the poles. When the direct radiation is not blocked byclouds, it is experienced as sunshine, combining the perception of bright white light (sunlight in the strict sense) andwarming. The warming on the body, the ground and other objects depends on the absorption (electromagneticradiation) of the electromagnetic radiation in the form of heat.The amount of radiation intercepted by a planetary body varies inversely with the square of the distance between thestar and the planet. The Earths orbit and obliquity change with time (over thousands of years), sometimes forming anearly perfect circle, and at other times stretching out to an orbital eccentricity of 5% (currently 1.67%). The totalinsolation remains almost constant due to Keplers second law,where is the "areal velocity" invariant. That is, the integration over the orbital period (also invariant) is aconstant.If we assume the solar radiation poweras a constant over time and the solar irradiation given by theinverse-square law, we obtain also the average insolation as a constant.But the seasonal and latitudinal distribution and intensity of solar radiation received at the Earths surface alsovaries.[15] For example, at latitudes of 65 degrees the change in solar energy in summer & winter can vary by morethan 25% as a result of the Earths orbital variation. Because changes in winter and summer tend to offset, the changein the annual average insolation at any given location is near zero, but the redistribution of energy between summerand winter does strongly affect the intensity of seasonal cycles. Such changes associated with the redistribution ofsolar energy are considered a likely cause for the coming and going of recent ice ages (see: Milankovitch cycles).Past variations in solar irradianceSpace-based observations of solar irradiance started in 1978. These measurements show that the solar constant is notconstant. It varies with the 11-year sunspot solar cycle. When going further back in time, one has to rely onirradiance reconstructions, using sunspots for the past 400 years or cosmogenic radionuclides for going back 10,000years. Such reconstructions have been done [16][17][18][19]. These studies show that solar irradiance does vary withdistinct periodicities such as: 11 years (Schwabe), 88 years (Gleisberg cycle), 208 years (DeVries cycle) and 1,000years (Eddy cycle).
8. 8. Sunlight 5Life on EarthThe existence of nearly all life on Earth is fueled by light from the sun.Most autotrophs, such as plants, use the energy of sunlight, combinedwith carbon dioxide and water, to produce simple sugarsa processknown as photosynthesis. These sugars are then used as buildingblocks and in other synthetic pathways which allow the organism togrow.Heterotrophs, such as animals, use light from the sun indirectly byconsuming the products of autotrophs, either by consuming autotrophs,by consuming their products or by consuming other heterotrophs. TheThis short film explores the vital connectionsugars and other molecular components produced by the autotrophs are between Earth and the Sun.then broken down, releasing stored solar energy, and giving theheterotroph the energy required for survival. This process is known as cellular respiration.In prehistory, humans began to further extend this process by putting plant and animal materials to other uses. Theyused animal skins for warmth, for example, or wooden weapons to hunt. These skills allowed humans to harvestmore of the sunlight than was possible through glycolysis alone, and human population began to grow.During the Neolithic Revolution, the domestication of plants and animals further increased human access to solarenergy. Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for futureharvests. Animals which had previously only provided humans with meat and tools once they were killed were nowused for labour throughout their lives, fueled by grasses inedible to humans.The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. These fossilfuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped withinthe earth for millions of years. Because the stored energy in these fossil fuels has accumulated over many millions ofyears, they have allowed modern humans to massively increase the production and consumption of primary energy.As the amount of fossil fuel is large but finite, this cannot continue indefinitely, and various theories exist as to whatwill follow this stage of human civilization (e.g. alternative fuels, Malthusian catastrophe, new urbanism, peak oil).Cultural aspectsThe effect of sunlight is relevant to painting, evidenced for instance inworks of Claude Monet on outdoor scenes and landscapes.Many people find direct sunlight to be too bright for comfort,especially when reading from white paper upon which the sun isdirectly shining. Indeed, looking directly at the sun can causelong-term vision damage. To compensate for the brightness of sunlight,many people wear sunglasses. Cars, many helmets and caps areequipped with visors to block the sun from direct vision when the sunis at a low angle. Sunshine is often blocked from entering buildingsthrough the use of walls, window blinds, awnings, shutters or curtains,or by nearby shade trees.In colder countries, many people prefer sunnier days and often avoidthe shade. In hotter countries the converse is true; during the midday Claude Monet: Le djeuner sur lherbehours many people prefer to stay inside to remain cool. If they do gooutside, they seek shade which may be provided by trees, parasols, andso on.
9. 9. Sunlight 6In Hinduism the sun is considered to be a god as it is the source of life and energy on earth.SunbathingSunbathing is a popular leisure activity in which a person sits or lies in direct sunshine. People often sunbathe incomfortable places where there is ample sunlight. Some common places for sunbathing include beaches, open airswimming pools, parks, gardens, and sidewalk cafs. Sunbathers typically wear limited amounts of clothing or somesimply go nude. For some, an alternative to sunbathing is the use of a sunbed that generates ultraviolet light and canbe used indoors regardless of outdoor weather conditions and amount of sunlight.For many people with pale or brownish skin, one purpose for sunbathing is to darken ones skin color (get a sun tan)as this is considered in some cultures to be beautiful, associated with outdoor activity, vacations/holidays, and health.Some people prefer naked sunbathing so that an "all-over" or "even" tan can be obtained, sometimes as part of aspecific lifestyle.For people suffering from psoriasis, sunbathing is an effective way of healing the symptoms.Skin tanning is achieved by an increase in the dark pigment inside skin cells called melanocytes and it is actually anautomatic response mechanism of the body to sufficient exposure to ultraviolet radiation from the sun or fromartificial sunlamps. Thus, the tan gradually disappears with time, when one is no longer exposed to these sources.Effects on human healthThe body produces vitamin D from sunlight (specifically from the UVB band of ultraviolet light), and excessiveseclusion from the sun can lead to deficiency unless adequate amounts are obtained through diet.Sunburn can have mild to severe inflammation effects on skin; this can be avoided by using a proper sunscreencream or lotion or by gradually building up melanocytes with increasing exposure. Another detrimental effect of UVexposure is accelerated skin aging (also called skin photodamage), which produces a difficult to treat cosmeticeffect. Some people are concerned that ozone depletion is increasing the incidence of such health hazards. A 10%decrease in ozone could cause a 25% increase in skin cancer.[20]A lack of sunlight, on the other hand, is considered one of the primary causes of seasonal affective disorder (SAD), aserious form of the "winter blues". SAD occurrence is more prevalent in locations further from the tropics, and mostof the treatments (other than prescription drugs) involve light therapy, replicating sunlight via lamps tuned to specific(visible, not ultra-violet) wavelengths of light or full-spectrum bulbs.A recent study indicates that more exposure to sunshine early in a persons life relates to less risk from multiplesclerosis (MS) later in life.[21]References[1] "Chapter 8 Measurement of sunshine duration" (http:/ / www. wmo. int/ pages/ prog/ www/ IMOP/ publications/ CIMO-Guide/ CIMOGuide 7th Edition, 2008/ Part I/ Chapter 8. pdf) (PDF). CIMO Guide. World Meteorological Organization. . Retrieved 2008-12-01.[2] "NASA: The 8-minute travel time to Earth by sunlight hides a thousand-year journey that actually began in the core" (http:/ / sunearthday.nasa. gov/ 2007/ locations/ ttt_sunlight. php). NASA, sunearthday.nasa.gov. . Retrieved 2012-02-12.[3] NASA Solar System Exploration - Sun: Facts & Figures (http:/ / solarsystem. nasa. gov/ planets/ profile. cfm?Display=Facts& Object=Sun)retrieved 27 April 2011 "Effective Temperature ... 5777K"[4] "The Multispectral Sun, from the National Earth Science Teachers Association" (http:/ / www. windows2universe. org/ sun/ spectrum/multispectral_sun_overview. html). Windows2universe.org. 2007-04-18. . Retrieved 2012-02-12.[5] Naylor, Mark; Kevin C. Farmer (1995). "Sun damage and prevention" (http:/ / www. telemedicine. org/ sundam/ sundam2. 4. 1. html).Electronic Textbook of Dermatology. The Internet Dermatology Society. . Retrieved 2008-06-02.[6] C. KANDILLI and K. ULGEN. "Solar Illumination and Estimating Daylight Availability of Global Solar Irradiance". Energy Sources.[7] "Satellite observations of total solar irradiance" (http:/ / acrim. com/ TSI Monitoring. htm). Acrim.com. . Retrieved 2012-02-12.[8] G. Kopp; J. Lean (2011). "A new, lower value of total solar irradiance: Evidence and climate significance". Geophys. Res. Lett.: L01706.Bibcode2011GeoRL..3801706K. doi:10.1029/2010GL045777.
10. 10. Sunlight7[9] Willson, R. C., and A. V. Mordvinov (2003), Secular total solar irradiance trend during solar cycles 2123, Geophys. Res. Lett., 30(5), 1199,doi:10.1029/2002GL016038 ACR (http:/ / www. acrim. com/ Reference Files/ Secular total solar irradiance trend during solar cycles 2123.pdf)[10] "Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present" (http:/ / www. pmodwrc. ch/ pmod.php?topic=tsi/ composite/ SolarConstant). . Retrieved 2005-10-05.[11] "NASA Goddard Space Flight Center: Solar Radiation" (http:/ / atmospheres. gsfc. nasa. gov/ climate/ index. php?section=136).Atmospheres.gsfc.nasa.gov. 2012-02-08. . Retrieved 2012-02-12.[12] http:/ / starhop. com/ library/ pdf/ studyguide/ high/ SolInt-19. pdf[13] "The Unveiling of Venus: Hot and Stifling". Science News 109 (25): 388. 1976-06-19. JSTOR3960800. "100 watts per square meter ...14,000 lux ... corresponds to ... daytime with overcast clouds"[14] Craig F. Bohren. "Atmospheric Optics" (http:/ / homepages. wmich. edu/ ~korista/ atmospheric_optics. pdf). .[15] "Graph of variation of seasonal and latitudinal distribution of solar radiation" (http:/ / www. museum. state. il. us/ exhibits/ ice_ages/insolation_graph. html). Museum.state.il.us. 2007-08-30. . Retrieved 2012-02-12.[16] Wang et al. (2005). The Astrophysical Journal, Volume 625, issue 1, pages 522-538, dx.doi.org/10.1086/429689 (http:/ / dx. doi. org/ 10.1086/ 429689).[17] Steinhilber et al. (2009), Geophysical Research Letters, Volume 36, L19704, http:/ / dx. doi. org/ 10. 1051/ 0004-6361/ 200811446[18] Vieira et al. (2011), Astronomy&Astrophysics, Volume 531, A6, http:/ / dx. doi. org/ 10. 1051/ 0004-6361/ 201015843[19] Steinhilber et al.(2012), Proceedings of the National Academy of Sciences, Early Edition http:/ / dx. doi. org/ 10. 1073/ pnas. 1118965109[20] Ozone Hole Consequences (http:/ / www. theozonehole. com/ consequences. htm) retrieved 30 October 2008[21] "NEUROLOGY 2007;69:381-388" (http:/ / www. neurology. org/ cgi/ content/ abstract/ 69/ 4/ 381?etoc). Neurology.org. 2007-07-24. .Retrieved 2012-02-12.Further reading Hartmann, Thom (1998). The Last Hours of Ancient Sunlight. London: Hodder and Stoughton. ISBN0-340-82243-0.External links Solar radiation - Encyclopedia of Earth (http://www.eoearth.org/article/Solar_radiation) Total Solar Irradiance (TSI) Daily mean data (http://www.ngdc.noaa.gov/stp/solar/solarirrad.html) at thewebsite of the National Geophysical Data Center Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present (http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant) by World Radiation Center,Physikalisch-Meteorologisches Observatorium Davos (pmod wrc) A Comparison of Methods for Providing Solar Radiation Data to Crop Models and Decision Support Systems(http://www.macaulay.ac.uk/LADSS/papers.html?2002), Rivington et al. Evaluation of three model estimations of solar radiation at 24 UK stations (http://www.macaulay.ac.uk/LADSS/papers.html?2005), Rivington et al. High resolution spectrum of solar radiation (http://bass2000.obspm.fr/solar_spect.php) from Observatoire deParis Measuring Solar Radiation (http://avc.comm.nsdlib.org/cgi-bin/wiki_grade_interface.pl?Measuring_Solar_Radiation) : A lesson plan from the National Science Digital Library. Websurf astronomical information (http://websurf.nao.rl.ac.uk/surfbin/first.cgi): Online tools for calculatingRising and setting times of Sun, Moon or planet, Azimuth of Sun, Moon or planet at rising and setting, Altitudeand azimuth of Sun, Moon or planet for a given date or range of dates, and more. An Excel workbook (http://www.ecy.wa.gov/programs/eap/models/solrad.zip) with a solar position andsolar radiation time-series calculator; by Greg Pelletier (http://www.ecy.wa.gov/programs/eap/models.html) DOE information (http://rredc.nrel.gov/solar/spectra/am1.5/) about the ASTM standard solar spectrum forPV evaluation. ASTM Standard (http://www.astm.org/Standards/G173.htm) for solar spectrum at ground level in the US(latitude ~ 37 degrees).
11. 11. Sunlight8 Detailed spectrum of the sun (http://apod.nasa.gov/apod/ap100627.html) at Astronomy Picture of the Day(http://apod.nasa.gov/apod/archivepix.html).Solar energySolar energy, radiant light and heat fromthe sun, has been harnessed by humans sinceancient times using a range of ever-evolvingtechnologies. Solar energy technologiesinclude solar heating, solar photovoltaics,solar thermal electricity and solararchitecture, which can make considerablecontributions to solving some of the mosturgent problems the world now faces.[1]Solar technologies are broadly characterizedas either passive solar or active solardepending on the way they capture, convertand distribute solar energy. Active solartechniques include the use of photovoltaic Nellis Solar Power Plant in the United States, one of the largest photovoltaic powerpanels and solar thermal collectors to plants in North America.harness the energy. Passive solar techniquesinclude orienting a building to the Sun,selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturallycirculate air.In 2011, the International Energy Agency said that "the development of affordable, inexhaustible and clean solarenergy technologies will have huge longer-term benefits. It will increase countries energy security through relianceon an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution,lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages areglobal. Hence the additional costs of the incentives for early deployment should be considered learning investments;they must be wisely spent and need to be widely shared".[1]Energy from the SunThe Earth receives 174petawatts (PW) of incoming solar radiation(insolation) at the upper atmosphere.[2] Approximately 30% is reflectedback to space while the rest is absorbed by clouds, oceans and landmasses. The spectrum of solar light at the Earths surface is mostlyspread across the visible and near-infrared ranges with a small part inthe near-ultraviolet.[3]Earths land surface, oceans and atmosphere absorb solar radiation, andthis raises their temperature. Warm air containing evaporated waterfrom the oceans rises, causing atmospheric circulation or convection.About half the incoming solar energy reaches theWhen the air reaches a high altitude, where the temperature is low, Earths surface.
12. 12. Solar energy9water vapor condenses into clouds, which rain onto the Earths surface, completing the water cycle. The latent heat ofwater condensation amplifies convection, producing atmospheric phenomena such as wind, cyclones andanti-cyclones.[4] Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of14C.[5] By photosynthesis green plants convert solar energy into chemical energy, which produces food, wood andthe biomass from which fossil fuels are derived.[6]Yearly Solar fluxes & Human Energy ConsumptionSolar[7] 3,850,000EJWind [8] 2,250EJBiomass[9] 3,000EJPrimary energy use (2005)[10] 487EJElectricity (2005)[11] 56.7EJThe total solar energy absorbed by Earths atmosphere, oceans and land masses is approximately 3,850,000exajoules(EJ) per year.[7] In 2002, this was more energy in one hour than the world used in one year.[12][13] Photosynthesiscaptures approximately 3,000EJ per year in biomass.[9] The amount of solar energy reaching the surface of theplanet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earthsnon-renewable resources of coal, oil, natural gas, and mined uranium combined.[14]Solar energy can be harnessed in different levels around the world. Depending on a geographical location the closerto the equator the more "potential" solar energy is available.[15]Applications of solar technologySolar energy refers primarily to the use of solar radiation for practicalends. However, all renewable energies, other than geothermal andtidal, derive their energy from the sun.Solar technologies are broadly characterized as either passive or activedepending on the way they capture, convert and distribute sunlight.Active solar techniques use photovoltaic panels, pumps, and fans toconvert sunlight into useful outputs. Passive solar techniques includeselecting materials with favorable thermal properties, designing spacesthat naturally circulate air, and referencing the position of a building toAverage insolation showing land area (smallblack dots) required to replace the world primarythe Sun. Active solar technologies increase the supply of energy andenergy supply with solar electricity. 18 TW isare considered supply side technologies, while passive solar 568 Exajoule (EJ) per year. Insolation for mosttechnologies reduce the need for alternate resources and are generallypeople is from 150 to 300 W/m2 or 3.5 to 7.0considered demand side technologies.[16]kWh/m2/day.
13. 13. Solar energy10Architecture and urban planningSunlight has influenced building design since the beginning ofarchitectural history.[18] Advanced solar architecture and urbanplanning methods were first employed by the Greeks and Chinese, whooriented their buildings toward the south to provide light andwarmth.[19]The common features of passive solar architecture are orientationrelative to the Sun, compact proportion (a low surface area to volumeratio), selective shading (overhangs) and thermal mass.[18] When theseDarmstadt University of Technology in Germanyfeatures are tailored to the local climate and environment they canwon the 2007 Solar Decathlon in Washington,produce well-lit spaces that stay in a comfortable temperature range.D.C. with this passive house designed specifically[17]Socrates Megaron House is a classic example of passive solarfor the humid and hot subtropical climate.design.[18] The most recent approaches to solar design use computermodeling tying together solar lighting, heating and ventilation systems in an integrated solar design package.[20]Active solar equipment such as pumps, fans and switchable windows can complement passive design and improvesystem performance.Urban heat islands (UHI) are metropolitan areas with higher temperatures than that of the surrounding environment.The higher temperatures are a result of increased absorption of the Solar light by urban materials such as asphalt andconcrete, which have lower albedos and higher heat capacities than those in the natural environment. Astraightforward method of counteracting the UHI effect is to paint buildings and roads white and plant trees. Usingthese methods, a hypothetical "cool communities" program in Los Angeles has projected that urban temperaturescould be reduced by approximately 3C at an estimated cost of US$1billion, giving estimated total annual benefitsof US$530million from reduced air-conditioning costs and healthcare savings.[21]Agriculture and horticultureAgriculture and horticulture seek to optimize the capture of solarenergy in order to optimize the productivity of plants. Techniques suchas timed planting cycles, tailored row orientation, staggered heightsbetween rows and the mixing of plant varieties can improve cropyields.[22][23] While sunlight is generally considered a plentifulGreenhouses like these in the Westlandmunicipality of the Netherlands grow vegetables,resource, the exceptions highlight the importance of solar energy to fruits and flowers.agriculture. During the short growing seasons of the Little Ice Age,French and English farmers employed fruit walls to maximize thecollection of solar energy. These walls acted as thermal masses and accelerated ripening by keeping plants warm.Early fruit walls were built perpendicular to the ground and facing south, but over time, sloping walls weredeveloped to make better use of sunlight. In 1699, Nicolas Fatio de Duillier even suggested using a trackingmechanism which could pivot to follow the Sun.[24] Applications of solar energy in agriculture aside from growingcrops include pumping water, drying crops, brooding chicks and drying chicken manure.[25][26] More recently thetechnology has been embraced by vinters, who use the energy generated by solar panels to power grape presses.[27]Greenhouses convert solar light to heat, enabling year-round production and the growth (in enclosed environments)of specialty crops and other plants not naturally suited to the local climate. Primitive greenhouses were first usedduring Roman times to produce cucumbers year-round for the Roman emperor Tiberius.[28] The first moderngreenhouses were built in Europe in the 16th century to keep exotic plants brought back from explorationsabroad.[29] Greenhouses remain an important part of horticulture today, and plastic transparent materials have alsobeen used to similar effect in polytunnels and row covers.
14. 14. Solar energy 11Solar lightingThe history of lighting is dominated by the use of natural light. TheRomans recognized a right to light as early as the 6th century andEnglish law echoed these judgments with the Prescription Act of1832.[30][31] In the 20th century artificial lighting became the mainsource of interior illumination but daylighting techniques and hybridsolar lighting solutions are ways to reduce energy consumption.Daylighting systems collect and distribute sunlight to provide interiorillumination. This passive technology directly offsets energy use byreplacing artificial lighting, and indirectly offsets non-solar energy use Daylighting features such as this oculus at the topby reducing the need for air-conditioning.[32] Although difficult to of the Pantheon, in Rome, Italy have been in usequantify, the use of natural lighting also offers physiological and since antiquity.[32]psychological benefits compared to artificial lighting.Daylightingdesign implies careful selection of window types, sizes and orientation; exterior shading devices may be consideredas well. Individual features include sawtooth roofs, clerestory windows, light shelves, skylights and light tubes. Theymay be incorporated into existing structures, but are most effective when integrated into a solar design package thataccounts for factors such as glare, heat flux and time-of-use. When daylighting features are properly implementedthey can reduce lighting-related energy requirements by 25%.[33]Hybrid solar lighting is an active solar method of providing interior illumination. HSL systems collect sunlight usingfocusing mirrors that track the Sun and use optical fibers to transmit it inside the building to supplementconventional lighting. In single-story applications these systems are able to transmit 50% of the direct sunlightreceived.[34]Solar lights that charge during the day and light up at dusk are a common sight along walkways.[35] Solar-chargedlanterns have become popular in developing countries where they provide a safer and cheaper alternative to kerosenelamps.[36]Although daylight saving time is promoted as a way to use sunlight to save energy, recent research has been limitedand reports contradictory results: several studies report savings, but just as many suggest no effect or even a net loss,particularly when gasoline consumption is taken into account. Electricity use is greatly affected by geography,climate and economics, making it hard to generalize from single studies.[37]
15. 15. Solar energy 12Solar thermalSolar thermal technologies can be used for water heating, space heating, space cooling and process heatgeneration.[38]Water heatingSolar hot water systems use sunlight to heat water. In low geographicallatitudes (below 40degrees) from 60 to 70% of the domestic hot wateruse with temperatures up to 60C can be provided by solar heatingsystems.[39] The most common types of solar water heaters areevacuated tube collectors (44%) and glazed flat plate collectors (34%)generally used for domestic hot water; and unglazed plastic collectors(21%) used mainly to heat swimming pools.[40]As of 2007, the total installed capacity of solar hot water systems isapproximately 154GW.[41] China is the world leader in theirdeployment with 70GW installed as of 2006 and a long term goal of210GW by 2020.[42] Israel and Cyprus are the per capita leaders in theuse of solar hot water systems with over 90% of homes using them.[43] Solar water heaters facing the Sun to maximizeIn the United States, Canada and Australia heating swimming pools isgain.the dominant application of solar hot water with an installed capacityof 18GW as of 2005.[16]Heating, cooling and ventilationIn the United States, heating, ventilation and air conditioning (HVAC)systems account for 30% (4.65EJ) of the energy used in commercialbuildings and nearly 50% (10.1EJ) of the energy used in residentialbuildings.[33][44] Solar heating, cooling and ventilation technologiescan be used to offset a portion of this energy.Thermal mass is any material that can be used to store heatheat fromthe Sun in the case of solar energy. Common thermal mass materialsinclude stone, cement and water. Historically they have been used inarid climates or warm temperate regions to keep buildings cool by Solar House #1 of Massachusetts Institute ofabsorbing solar energy during the day and radiating stored heat to theTechnology in the United States, built in 1939,cooler atmosphere at night. However they can be used in cold used seasonal thermal storage for year-roundtemperate areas to maintain warmth as well. The size and placement ofheating.thermal mass depend on several factors such as climate, daylightingand shading conditions. When properly incorporated, thermal mass maintains space temperatures in a comfortablerange and reduces the need for auxiliary heating and cooling equipment.[45]A solar chimney (or thermal chimney, in this context) is a passive solar ventilation system composed of a verticalshaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing anupdraft that pulls air through the building. Performance can be improved by using glazing and thermal massmaterials[46] in a way that mimics greenhouses.Deciduous trees and plants have been promoted as a means of controlling solar heating and cooling. When plantedon the southern side of a building, their leaves provide shade during the summer, while the bare limbs allow light topass during the winter.[47] Since bare, leafless trees shade 1/3 to 1/2 of incident solar radiation, there is a balancebetween the benefits of summer shading and the corresponding loss of winter heating.[48] In climates with significant
16. 16. Solar energy13heating loads, deciduous trees should not be planted on the southern side of a building because they will interferewith winter solar availability. They can, however, be used on the east and west sides to provide a degree of summershading without appreciably affecting winter solar gain.[49]Water treatmentSolar distillation can be used to make saline or brackish water potable.The first recorded instance of this was by 16th century Arabalchemists.[50] A large-scale solar distillation project was firstconstructed in 1872 in the Chilean mining town of Las Salinas.[51] Theplant, which had solar collection area of 4,700m2, could produce up to22,700L per day and operated for 40years.[51] Individual still designsinclude single-slope, double-slope (or greenhouse type), vertical,conical, inverted absorber, multi-wick, and multiple effect.[50] Thesestills can operate in passive, active, or hybrid modes. Double-slope Solar water disinfection in Indonesiastills are the most economical for decentralized domestic purposes,while active multiple effect units are more suitable for large-scaleapplications.[50]Solar water disinfection (SODIS) involves exposing water-filled plasticpolyethylene terephthalate (PET) bottles to sunlight for severalhours.[52] Exposure times vary depending on weather and climate froma minimum of six hours to two days during fully overcastconditions.[53] It is recommended by the World Health Organization asa viable method for household water treatment and safe storage.[54]Over two million people in developing countries use this method fortheir daily drinking water.[53]Small scale solar powered sewerage treatment plant.Solar energy may be used in a water stabilisation pond to treat wastewater without chemicals or electricity. A further environmentaladvantage is that algae grow in such ponds and consume carbon dioxide in photosynthesis, although algae mayproduce toxic chemicals that make the water unusable.[55][56]CookingSolar cookers use sunlight for cooking, drying and pasteurization. Theycan be grouped into three broad categories: box cookers, panel cookersand reflector cookers.[57] The simplest solar cooker is the box cookerfirst built by Horace de Saussure in 1767.[58] A basic box cookerconsists of an insulated container with a transparent lid. It can be usedeffectively with partially overcast skies and will typically reachtemperatures of 90150C.[59] Panel cookers use a reflective panel todirect sunlight onto an insulated container and reach temperatures The Solar Bowl in Auroville, India, concentratescomparable to box cookers. Reflector cookers use various sunlight on a movable receiver to produce steamconcentrating geometries (dish, trough, Fresnel mirrors) to focus light for cooking.on a cooking container. These cookers reach temperatures of 315Cand above but require direct light to function properly and must be repositioned to track the Sun.[60]The solar bowl is a concentrating technology employed by the Solar Kitchen in Auroville, Pondicherry, India, wherea stationary spherical reflector focuses light along a line perpendicular to the spheres interior surface, and a
17. 17. Solar energy 14computer control system moves the receiver to intersect this line. Steam is produced in the receiver at temperaturesreaching 150C and then used for process heat in the kitchen.[61]A reflector developed by Wolfgang Scheffler in 1986 is used in many solar kitchens. Scheffler reflectors are flexibleparabolic dishes that combine aspects of trough and power tower concentrators. Polar tracking is used to follow theSuns daily course and the curvature of the reflector is adjusted for seasonal variations in the incident angle ofsunlight. These reflectors can reach temperatures of 450650C and have a fixed focal point, which simplifiescooking.[62] The worlds largest Scheffler reflector system in Abu Road, Rajasthan, India is capable of cooking up to35,000 meals a day.[63] As of 2008, over 2,000 large Scheffler cookers had been built worldwide.[64]Process heatSolar concentrating technologies such as parabolic dish, trough and Scheffler reflectors can provide process heat forcommercial and industrial applications. The first commercial system was the Solar Total Energy Project (STEP) inShenandoah, Georgia, USA where a field of 114 parabolic dishes provided 50% of the process heating, airconditioning and electrical requirements for a clothing factory. This grid-connected cogeneration system provided400kW of electricity plus thermal energy in the form of 401kW steam and 468kW chilled water, and had a onehour peak load thermal storage.[65]Evaporation ponds are shallow pools that concentrate dissolved solids through evaporation. The use of evaporationponds to obtain salt from sea water is one of the oldest applications of solar energy. Modern uses includeconcentrating brine solutions used in leach mining and removing dissolved solids from waste streams.[66]Clothes lines, clotheshorses, and clothes racks dry clothes through evaporation by wind and sunlight withoutconsuming electricity or gas. In some states of the United States legislation protects the "right to dry" clothes.[67]Unglazed transpired collectors (UTC) are perforated sun-facing walls used for preheating ventilation air. UTCs canraise the incoming air temperature up to 22C and deliver outlet temperatures of 4560C.[68] The short paybackperiod of transpired collectors (3 to 12years) makes them a more cost-effective alternative than glazed collectionsystems.[68] As of 2003, over 80 systems with a combined collector area of 35,000m2 had been installed worldwide,including an 860m2 collector in Costa Rica used for drying coffee beans and a 1,300m2 collector in Coimbatore,India used for drying marigolds.[26]Solar powerSolar power is the conversion of sunlight into electricity, either directlyusing photovoltaics (PV), or indirectly using concentrated solar power(CSP). CSP systems use lenses or mirrors and tracking systems tofocus a large area of sunlight into a small beam. PV converts light intoelectric current using the photoelectric effect.Commercial CSP plants were first developed in the 1980s, and the 354MW SEGS CSP installation is the largest solar power plant in theworld and is located in the Mojave Desert of California. Other largeThe PS10 concentrates sunlight from a field ofCSP plants include the Solnova Solar Power Station (150 MW) and theheliostats on a central tower.Andasol solar power station (100 MW), both in Spain. The 214 MWCharanka Solar Park in India, is the worlds largest photovoltaic plant.
18. 18. Solar energy 15Concentrated solar powerConcentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area ofsunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. Awide range of concentrating technologies exists; the most developed are the parabolic trough, the concentratinglinear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun andfocus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for powergeneration or energy storage.[69]PhotovoltaicsA solar cell, or photovoltaic cell (PV), is a device that converts lightinto electric current using the photoelectric effect. The first solar cellwas constructed by Charles Fritts in the 1880s.[70] In 1931 a Germanengineer, Dr Bruno Lange, developed a photo cell using silver selenidein place of copper oxide.[71] Although the prototype selenium cellsconverted less than 1% of incident light into electricity, both ErnstWerner von Siemens and James Clerk Maxwell recognized theimportance of this discovery.[72] Following the work of Russell Ohl inthe 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin80 MW Okhotnykovo Solar Park in Ukraine.created the silicon solar cell in 1954.[73] These early solar cells cost286USD/watt and reached efficiencies of 4.56%.[74]Solar chemicalSolar chemical processes use solar energy to drive chemical reactions.These processes offset energy that would otherwise come from a fossilfuel source and can also convert solar energy into storable andtransportable fuels. Solar induced chemical reactions can be dividedinto thermochemical or photochemical.[75] A variety of fuels can beproduced by artificial photosynthesis.[76] The multielectron catalyticNREL compilation of best research solar cellchemistry involved in making carbon-based fuels (such as methanol)efficiencies from 1976 to 2010from reduction of carbon dioxide is challenging; a feasible alternativeis hydrogen production from protons, though use of water as the source of electrons (as plants do) requires masteringthe multielectron oxidation of two water molecules to molecular oxygen.[77] Some have envisaged working solar fuelplants in coastal metropolitan areas by 2050- the splitting of sea water providing hydrogen to be run through adjacentfuel-cell electric power plants and the pure water by-product going directly into the municipal water system.[78]Hydrogen production technologies been a significant area of solar chemical research since the 1970s. Aside fromelectrolysis driven by photovoltaic or photochemical cells, several thermochemical processes have also beenexplored. One such route uses concentrators to split water into oxygen and hydrogen at high temperatures(2300-2600C).[79] Another approach uses the heat from solar concentrators to drive the steam reformation ofnatural gas thereby increasing the overall hydrogen yield compared to conventional reforming methods.[80]Thermochemical cycles characterized by the decomposition and regeneration of reactants present another avenue forhydrogen production. The Solzinc process under development at the Weizmann Institute uses a 1MW solar furnaceto decompose zinc oxide (ZnO) at temperatures above 1200C. This initial reaction produces pure zinc, which cansubsequently be reacted with water to produce hydrogen.[81]Sandias Sunshine to Petrol (S2P) technology uses the high temperatures generated by concentrating sunlight alongwith a zirconia/ferrite catalyst to break down atmospheric carbon dioxide into oxygen and carbon monoxide (CO).
19. 19. Solar energy 16The carbon monoxide can then be used to synthesize conventional fuels such as methanol, gasoline and jet fuel.[82]A photogalvanic device is a type of battery in which the cell solution (or equivalent) forms energy-rich chemicalintermediates when illuminated. These energy-rich intermediates can potentially be stored and subsequently reactedat the electrodes to produce an electric potential. The ferric-thionine chemical cell is an example of thistechnology.[83]Photoelectrochemical cells or PECs consist of a semiconductor, typically titanium dioxide or related titanates,immersed in an electrolyte. When the semiconductor is illuminated an electrical potential develops. There are twotypes of photoelectrochemical cells: photoelectric cells that convert light into electricity and photochemical cells thatuse light to drive chemical reactions such as electrolysis.[84]A combination thermal/photochemical cell has also been proposed. The Stanford PETE process uses solar thermalenergy to raise the temperature of a thermionic metal to about 800C to increase the rate of production of electricity toelectrolyse atmospheric CO2 down to carbon or carbon monoxide which can then be used for fuel production, andthe waste heat can be used as well.[85]Solar vehiclesDevelopment of a solar powered car has been an engineering goalsince the 1980s. The World Solar Challenge is a biannualsolar-powered car race, where teams from universities and enterprisescompete over 3021 kilometres (unknown operator: ustrongmi)across central Australia from Darwin to Adelaide. In 1987, when it wasfounded, the winners average speed was 67 kilometres per hour(unknown operator: ustrongmph) and by 2007 the winnersaverage speed had improved to 90.87 kilometres per hour (unknownoperator: ustrongmph).[86] The North American Solar Challengeand the planned South African Solar Challenge are comparablecompetitions that reflect an international interest in the engineering andAustralia hosts the World Solar Challenge wheredevelopment of solar powered vehicles.[87][88]solar cars like the Nuna3 race through a 3021km(unknown operator: ustrongmi) course fromSome vehicles use solar panels for auxiliary power, such as for air Darwin to Adelaide.conditioning, to keep the interior cool, thus reducing fuelconsumption.[89][90]In 1975, the first practical solar boat was constructed in England.[91] By 1995, passenger boats incorporating PVpanels began appearing and are now used extensively.[92] In 1996, Kenichi Horie made the first solar poweredcrossing of the Pacific Ocean, and the sun21 catamaran made the first solar powered crossing of the Atlantic Oceanin the winter of 20062007.[93] There are plans to circumnavigate the globe in 2010.[94]In 1974, the unmanned AstroFlight Sunrise plane made the first solarflight. On 29 April 1979, the Solar Riser made the first flight in a solarpowered, fully controlled, man carrying flying machine, reaching analtitude of 40 feet (unknown operator: ustrongm). In 1980, theGossamer Penguin made the first piloted flights powered solely byphotovoltaics. This was quickly followed by the Solar Challengerwhich crossed the English Channel in July 1981. In 1990 Eric ScottRaymond in 21 hops flew from California to North Carolina usingHelios UAV in solar powered flight.solar power.[95] Developments then turned back to unmanned aerial
20. 20. Solar energy 17vehicles (UAV) with the Pathfinder (1997) and subsequent designs, culminating in the Helios which set the altituderecord for a non-rocket-propelled aircraft at 29524 metres (unknown operator: ustrong ft) in 2001.[96] TheZephyr, developed by BAE Systems, is the latest in a line of record-breaking solar aircraft, making a 54-hour flightin 2007, and month-long flights are envisioned by 2010.[97]A solar balloon is a black balloon that is filled with ordinary air. As sunlight shines on the balloon, the air inside isheated and expands causing an upward buoyancy force, much like an artificially heated hot air balloon. Some solarballoons are large enough for human flight, but usage is generally limited to the toy market as the surface-area topayload-weight ratio is relatively high.[98]Solar sails are a proposed form of spacecraft propulsion using large membrane mirrors to exploit radiation pressurefrom the Sun. Unlike rockets, solar sails require no fuel. Although the thrust is small compared to rockets, itcontinues as long as the Sun shines onto the deployed sail and in the vacuum of space significant speeds caneventually be achieved.[99]The High-altitude airship (HAA) is an unmanned, long-duration, lighter-than-air vehicle using helium gas for lift,and thin film solar cells for power. The United States Department of Defense Missile Defense Agency has contractedLockheed Martin to construct it to enhance the Ballistic Missile Defense System (BMDS).[100] Airships have someadvantages for solar-powered flight: they do not require power to remain aloft, and an airships envelope presents alarge area to the Sun.Energy storage methodsSolar energy is not available at night, and energy storage is animportant issue because modern energy systems usually assumecontinuous availability of energy.[101]Thermal mass systems can store solar energy in the form of heat atdomestically useful temperatures for daily or seasonal durations.Thermal storage systems generally use readily available materials with Solar Twos thermal storage system generatedhigh specific heat capacities such as water, earth and stone. electricity during cloudy weather and at night.Well-designed systems can lower peak demand, shift time-of-use tooff-peak hours and reduce overall heating and coolingrequirements.[102][103]Phase change materials such as paraffin wax and Glaubers salt are another thermal storage media. These materialsare inexpensive, readily available, and can deliver domestically useful temperatures (approximately 64C). The"Dover House" (in Dover, Massachusetts) was the first to use a Glaubers salt heating system, in 1948.[104]Solar energy can be stored at high temperatures using molten salts. Salts are an effective storage medium becausethey are low-cost, have a high specific heat capacity and can deliver heat at temperatures compatible withconventional power systems. The Solar Two used this method of energy storage, allowing it to store 1.44TJ in its68m3 storage tank with an annual storage efficiency of about 99%.[105]Off-grid PV systems have traditionally used rechargeable batteries to store excess electricity. With grid-tied systems,excess electricity can be sent to the transmission grid, while standard grid electricity can be used to meet shortfalls.Net metering programs give household systems a credit for any electricity they deliver to the grid. This is oftenlegally handled by rolling back the meter whenever the home produces more electricity than it consumes. If the netelectricity use is below zero, the utility is required to pay for the extra at the same rate as they charge consumers.[106]Other legal approaches involve the use of two meters, to measure electricity consumed vs. electricity produced. Thisis less common due to the increased installation cost of the second meter.Pumped-storage hydroelectricity stores energy in the form of water pumped when energy is available from a lowerelevation reservoir to a higher elevation one. The energy is recovered when demand is high by releasing the water to
21. 21. Solar energy 18run through a hydroelectric power generator.[107]Development, deployment and economicsBeginning with the surge in coal use which accompanied the Industrial Revolution, energy consumption has steadilytransitioned from wood and biomass to fossil fuels. The early development of solar technologies starting in the 1860swas driven by an expectation that coal would soon become scarce. However development of solar technologiesstagnated in the early 20thcentury in the face of the increasing availability, economy, and utility of coal andpetroleum.[108]The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world andbrought renewed attention to developing solar technologies.[109][110] Deployment strategies focused on incentiveprograms such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Otherefforts included the formation of research facilities in the US (SERI, now NREL), Japan (NEDO), and Germany(Fraunhofer Institute for Solar Energy Systems ISE).[111]Commercial solar water heaters began appearing in the United States in the 1890s.[112] These systems saw increasinguse until the 1920s but were gradually replaced by cheaper and more reliable heating fuels.[113] As withphotovoltaics, solar water heating attracted renewed attention as a result of the oil crises in the 1970s but interestsubsided in the 1980s due to falling petroleum prices. Development in the solar water heating sector progressedsteadily throughout the 1990s and growth rates have averaged 20% per year since 1999.[41] Although generallyunderestimated, solar water heating and cooling is by far the most widely deployed solar technology with anestimated capacity of 154GW as of 2007.[41]The International Energy Agency has said that solar energy can make considerable contributions to solving some ofthe most urgent problems the world now faces:[1]The development of affordable, inexhaustible and clean solar energy technologies will have hugelonger-term benefits. It will increase countries energy security through reliance on an indigenous,inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lowerthe costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. Theseadvantages are global. Hence the additional costs of the incentives for early deployment should beconsidered learning investments; they must be wisely spent and need to be widely shared.[1]In 2011, the International Energy Agency said that solar energy technologies such as photovoltaic panels, solar waterheaters and power stations built with mirrors could provide a third of the worlds energy by 2060 if politicianscommit to limiting climate change. The energy from the sun could play a key role in de-carbonizing the globaleconomy alongside improvements in energy efficiency and imposing costs on greenhouse gas emitters. "The strengthof solar is the incredible variety and flexibility of applications, from small scale to big scale".[114]
22. 22. Solar energy19ISO StandardsThe International Organization for Standardization has established a number of standards relating to solar energyequipment. For example, ISO 9050 relates to glass in building while ISO 10217 relates to the materials used in solarwater heaters.Notes[1] "Solar Energy Perspectives: Executive Summary" (http:/ / www. webcitation. org/ 63fIHKr1S) (PDF). International Energy Agency. 2011.Archived from the original (http:/ / www. iea. org/ Textbase/ npsum/ solar2011SUM. pdf) on 2011-12-03. .[2] Smil (1991), p. 240[3] "Natural Forcing of the Climate System" (http:/ / www. grida. no/ climate/ ipcc_tar/ wg1/ 041. htm#121). Intergovernmental Panel on ClimateChange. . Retrieved 2007-09-29.[4] "Radiation Budget" (http:/ / marine. rutgers. edu/ mrs/ education/ class/ yuri/ erb. html). NASA Langley Research Center. 2006-10-17. .Retrieved 2007-09-29.[5] Somerville, Richard. "Historical Overview of Climate Change Science" (http:/ / www. ipcc. ch/ pdf/ assessment-report/ ar4/ wg1/ar4-wg1-chapter1. pdf) (PDF). Intergovernmental Panel on Climate Change. . Retrieved 2007-09-29.[6] Vermass, Wim. "An Introduction to Photosynthesis and Its Applications" (http:/ / photoscience. la. asu. edu/ photosyn/ education/ photointro.html). Arizona State University. . Retrieved 2007-09-29.[7] Smil (2006), p. 12[8] Archer, Cristina; Jacobson, Mark. "Evaluation of Global Wind Power" (http:/ / www. stanford. edu/ group/ efmh/ winds/ global_winds. html).Stanford. . Retrieved 2008-06-03.[9] "Energy conversion by photosynthetic organisms" (http:/ / www. fao. org/ docrep/ w7241e/ w7241e06. htm#TopOfPage). Food andAgriculture Organization of the United Nations. . Retrieved 2008-05-25.[10] "World Consumption of Primary Energy by Energy Type and Selected Country Groups, 1980-2004" (http:/ / www. eia. doe. gov/ pub/international/ iealf/ table18. xls). Energy Information Administration. . Retrieved 2008-05-17.[11] "World Total Net Electricity Consumption, 1980-2005" (http:/ / www. eia. doe. gov/ iea/ elec. html). Energy Information Administration. .Retrieved 2008-05-25.[12] Solar energy: A new day dawning? (http:/ / www. nature. com/ nature/ journal/ v443/ n7107/ full/ 443019a. html) retrieved 7 August 2008[13] Powering the Planet: Chemical challenges in solar energy utilization (http:/ / web. mit. edu/ mitpep/ pdf/ DGN_Powering_Planet. pdf)retrieved 7 August 2008[14] Exergy (available energy) Flow Charts (http:/ / gcep. stanford. edu/ research/ exergycharts. html) 2.7 YJ solar energy each year for twobillion years vs. 1.4 YJ non-renewable resources available once.[15] http:/ / www. solarenergybyzip. com[16] Philibert, Cdric (2005). "The Present and Future use of Solar Thermal Energy as a Primary Source of Energy" (http:/ / www. webcitation.org/ 63rZo6Rn2). IEA. Archived from the original (http:/ / philibert. cedric. free. fr/ Downloads/ solarthermal. pdf) on 2011-12-12. .[17] "Darmstadt University of Technology solar decathlon home design" (http:/ / web. archive. org/ web/ 20071018035727/ http:/ / www.solardecathlon. de/ index. php/ our-house/ the-design). Darmstadt University of Technology. Archived from the original (http:/ / www.solardecathlon. de/ index. php/ our-house/ the-design) on October 18, 2007. . Retrieved 2008-04-25.[18] Schittich (2003), p. 14[19] Butti and Perlin (1981), p. 4, 159[20] Balcomb(1992)[21] Rosenfeld, Arthur; Romm, Joseph; Akbari, Hashem; Lloyd, Alan. "Painting the Town White -- and Green" (http:/ / web. archive. org/ web/20070714173907/ http:/ / eetd. lbl. gov/ HeatIsland/ PUBS/ PAINTING/ ). Heat Island Group. Archived from the original (http:/ / eetd. lbl.gov/ HeatIsland/ PUBS/ PAINTING/ ) on 2007-07-14. . Retrieved 2007-09-29.[22] Jeffrey C. Silvertooth. "Row Spacing, Plant Population, and Yield Relationships" (http:/ / ag. arizona. edu/ crop/ cotton/ comments/april1999cc. html). University of Arizona. . Retrieved 2008-06-24.[23] Kaul (2005), p. 169174[24] Butti and Perlin (1981), p. 4246[25] Bnard (1981), p. 347[26] Leon (2006), p. 62[27] "A Powerhouse Winery" (http:/ / www. novusvinum. com/ news/ latest_news. html#gonzales). News Update. Novus Vinum. 2008-10-27. .Retrieved 2008-11-05.[28] Butti and Perlin (1981), p. 19[29] Butti and Perlin (1981), p. 41[30] "Prescription Act (1872 Chapter 71 2 and 3 Will 4)" (http:/ / www. opsi. gov. uk/ RevisedStatutes/ Acts/ ukpga/ 1832/cukpga_18320071_en_1). Office of the Public Sector Information. . Retrieved 2008-05-18.
23. 23. Solar energy20[31] Noyes, WM (1860-03-31). "The Law of Light" (http:/ / query. nytimes. com/ mem/ archive-free/ pdf?_r=1&res=9503E1D81E30EE34BC4950DFB566838B679FDE& oref=slogin) (PDF). The New York Times. . Retrieved 2008-05-18.[32] Tzempelikos (2007), p. 369[33] Apte, J. et al.. "Future Advanced Windows for Zero-Energy Homes" (http:/ / windows. lbl. gov/ adv_Sys/ ASHRAE Final DynamicWindows. pdf) (PDF). American Society of Heating, Refrigerating and Air-Conditioning Engineers. . Retrieved 2008-04-09.[34] Muhs, Jeff. "Design and Analysis of Hybrid Solar Lighting and Full-Spectrum Solar Energy Systems" (http:/ / web. archive. org/ web/20070926033214/ http:/ / www. ornl. gov/ sci/ solar/ pdfs/ Muhs_ASME_Paper. pdf) (PDF). Oak Ridge National Laboratory. Archived fromthe original (http:/ / www. ornl. gov/ sci/ solar/ pdfs/ Muhs_ASME_Paper. pdf) on 2007-09-26. . Retrieved 2007-09-29.[35] Shienkopf, Ken (17 March 2001). "Solar Yard Lights Are Well Worth the Price" (http:/ / news. google. com/newspapers?id=jZ8sAAAAIBAJ& sjid=hv0DAAAAIBAJ& pg=4166,5310044& dq=solar+ lights+ that+ charge+ during+ the+ day& hl=en).Lakeland Ledger. . Retrieved 3 July 2011.[36] Ashden Awards case study on solar-powered lanterns in India (http:/ / www. ashdenawards. org/ winners/ nest)[37] Myriam B.C. Aries; Guy R. Newsham (2008). "Effect of daylight saving time on lighting energy use: a literature review". Energy Policy 36(6): 18581866. doi:10.1016/j.enpol.2007.05.021.[38] "Solar Energy Technologies and Applications" (http:/ / www. canren. gc. ca/ tech_appl/ index. asp?CaId=5& PgId=121). CanadianRenewable Energy Network. . Retrieved 2007-10-22.[39] "Renewables for Heating and Cooling" (http:/ / www. iea. org/ textbase/ nppdf/ free/ 2007/ Renewable_Heating_Cooling. pdf) (PDF).International Energy Agency. . Retrieved 2008-05-26.[40] Weiss, Werner; Bergmann, Irene; Faninger, Gerhard. "Solar Heat Worldwide (Markets and Contributions to the Energy Supply 2005)"(http:/ / www. iea-shc. org/ publications/ statistics/ IEA-SHC_Solar_Heat_Worldwide-2007. pdf) (PDF). International Energy Agency. .Retrieved 2008-05-30.[41] Weiss, Werner; Bergmann, Irene; Faninger, Gerhard. "Solar Heat Worldwide - Markets and Contribution to the Energy Supply 2006" (http:// www. iea-shc. org/ publications/ statistics/ IEA-SHC_Solar_Heat_Worldwide-2008. pdf) (PDF). International Energy Agency. . Retrieved2008-06-09.[42] "Renewables 2007 Global Status Report" (http:/ / www. ren21. net/ pdf/ RE2007_Global_Status_Report. pdf) (PDF). Worldwatch Institute. .Retrieved 2008-04-30.[43] Del Chiaro, Bernadette; Telleen-Lawton, Timothy. "Solar Water Heating (How California Can Reduce Its Dependence on Natural Gas)"(http:/ / www. environmentcalifornia. org/ uploads/ at/ 56/ at563bKwmfrtJI6fKl9U_w/ Solar-Water-Heating. pdf) (PDF). EnvironmentCalifornia Research and Policy Center. . Retrieved 2007-09-29.[44] "Energy Consumption Characteristics of Commercial Building HVAC Systems Volume III: Energy Savings Potential" (http:/ / www.doas-radiant. psu. edu/ DOE_report. pdf) (PDF). United States Department of Energy. pp.22. . Retrieved 2008-06-24.[45] Mazria(1979), p. 2935[46] Bright, David (18 February 1977). "Passive solar heating simpler for the average owner." (http:/ / news. google. com/newspapers?id=beAzAAAAIBAJ& sjid=UDgHAAAAIBAJ& pg=1418,1115815& dq=improved+ by+ using+ glazing+ and+ thermal+mass& hl=en). Bangor Daily News. . Retrieved 3 July 2011.[47] Mazria(1979), p. 255[48] Balcomb(1992), p. 56[49] Balcomb(1992), p. 57[50] Tiwari (2003), p. 368371[51] Daniels (1964), p. 6[52] "SODIS solar water disinfection" (http:/ / www. sodis. ch). EAWAG (The Swiss Federal Institute for Environmental Science andTechnology). . Retrieved 2008-05-02.[53] "Household Water Treatment Options in Developing Countries: Solar Disinfection (SODIS)" (http:/ / web. archive. org/ web/20080529090729/ http:/ / www. ehproject. org/ PDF/ ehkm/ cdc-options_sodis. pdf) (PDF). Centers for Disease Control and Prevention.Archived from the original (http:/ / www. ehproject. org/ PDF/ ehkm/ cdc-options_sodis. pdf) on 2008-05-29. . Retrieved 2008-05-13.[54] "Household Water Treatment and Safe Storage" (http:/ / www. who. int/ household_water/ en/ ). World Health Organization. . Retrieved2008-05-02.[55] Shilton AN, Powell N, Mara DD, Craggs R (2008). "Solar-powered aeration and disinfection, anaerobic co-digestion, biological CO(2)scrubbing and biofuel production: the energy and carbon management opportunities of waste stabilisation ponds". Water Sci. Technol. 58 (1):253258. doi:10.2166/wst.2008.666. PMID18653962.[56] Tadesse I, Isoaho SA, Green FB, Puhakka JA (2003). "Removal of organics and nutrients from tannery effluent by advanced integratedWastewater Pond Systems technology". Water Sci. Technol. 48 (2): 30714. PMID14510225.[57] Anderson and Palkovic (1994), p. xi[58] Butti and Perlin (1981), p. 5459[59] Anderson and Palkovic (1994), p. xii[60] Anderson and Palkovic (1994), p. xiii[61] "The Solar Bowl" (http:/ / www. auroville. org/ research/ ren_energy/ solar_bowl. htm). Auroville Universal Township. . Retrieved2008-04-25.
24. 24. Solar energy21[62] "Scheffler-Reflector" (http:/ / www. solare-bruecke. org/ English/ scheffler_e-Dateien/ scheffler_e. htm). Solare Bruecke. . Retrieved2008-04-25.[63] "Solar Steam Cooking System" (http:/ / web. archive. org/ web/ 20071111132802/ http:/ / gadhia-solar. com/ products/ steam. htm). GadhiaSolar. Archived from the original (http:/ / gadhia-solar. com/ products/ steam. htm) on November 11, 2007. . Retrieved 2008-04-25.[64] "Scheffler Reflector" (http:/ / www. solare-bruecke. org/ infoartikel/ info_vorstand. htm#english). Solare Bruecke. . Retrieved 2008-07-03.[65] Stine, W B and Harrigan, R W. "Shenandoah Solar Total Energy Project" (http:/ / www. powerfromthesun. net/ chapter16/ Chapter16Text.htm). John Wiley. . Retrieved 2008-07-20.[66] Bartlett (1998), p.393394[67] Thomson-Philbrook, Julia. "Right to Dry Legislation in New England and Other States" (http:/ / www. cga. ct. gov/ 2008/ rpt/ 2008-R-0042.htm). Connecticut General Assembly. . Retrieved 2008-05-27.[68] "Solar Buildings (Transpired Air Collectors - Ventilation Preheating)" (http:/ / www. nrel. gov/ docs/ fy06osti/ 29913. pdf) (PDF). NationalRenewable Energy Laboratory. . Retrieved 2007-09-29.[69] Martin and Goswami (2005), p. 45[70] Perlin (1999), p. 147[71] "Magic Plates, Tap Sun For Power", June 1931, Popular Science (http:/ / books. google. com/ books?id=9CcDAAAAMBAJ& pg=PA41&dq=Popular+ Science+ 1931+ plane#v=onepage& q=Popular Science 1931 plane& f=true). . Retrieved 2011-04-19.[72] Perlin (1999), p. 1820[73] Perlin (1999), p. 29[74] Perlin (1999), p. 2930, 38[75] Bolton (1977), p. 1[76] Wasielewski MR. Photoinduced electron transfer in supramolecular systems for artificial photosynthesis. Chem. Rev. 1992; 92: 435-461.[77] Hammarstrom L and Hammes-Schiffer S. Artificial Photosynthesis and Solar Fuels. Accounts of Chemical Research 2009; 42 (12):1859-1860.[78] Gray HB. Powering the planet with solar fuel. Nature Chemistry 2009; 1: 7.[79] Agrafiotis (2005), p. 409[80] Zedtwitz (2006), p. 1333[81] "Solar Energy Project at the Weizmann Institute Promises to Advance the use of Hydrogen Fuel" (http:/ / wis-wander. weizmann. ac. il/ site/en/ weizman. asp?pi=371& doc_id=4210). Weizmann Institute of Science. . Retrieved 2008-06-25.[82] "Sandias Sunshine to Petrol project seeks fuel from thin air" (http:/ / www. sandia. gov/ news/ resources/ releases/ 2007/ sunshine. html).Sandia Corporation. . Retrieved 2008-05-02.[83] Bolton (1977), p. 16, 119[84] Bolton (1977), p. 11[85] http:/ / spacefellowship. com/ news/ art21587/ solar-power-could-soon-compete-with-oil. html[86] "The WORLD Solar Challenge - The Background" (http:/ / web. archive. org/ web/ 20080719140545/ http:/ / www. anzses. org/ files/ The+WORLD+ Solar+ Challenge. pdf) (PDF). Australian and New Zealand Solar Energy Society. Archived from the original (http:/ / www.anzses. org/ files/ The WORLD Solar Challenge. pdf) on July 19, 2008. . Retrieved 2008-08-05.[87] "North American Solar Challenge" (http:/ / americansolarchallenge. org/ ). New Resources Group. . Retrieved 2008-07-03.[88] "South African Solar Challenge" (http:/ / web. archive. org/ web/ 20080612165911/ http:/ / www. solarchallenge. org. za/ Default.aspx?AspxAutoDetectCookieSupport=1). Advanced Energy Foundation. Archived from the original (http:/ / www. solarchallenge. org. za/Default. aspx?AspxAutoDetectCookieSupport=1) on June 12, 2008. . Retrieved 2008-07-03.[89] Vehicle auxiliary power applications for solar cells (http:/ / ieeexplore. ieee. org/ Xplore/ login. jsp?url=/ iel3/ 1205/ 3985/ 00152037.pdf?arnumber=152037) 1991 Retrieved 11 October 2008[90] systaic AG: Demand for Car Solar Roofs Skyrockets (http:/ / www. systaic. com/ press/ press-release/systaic-ag-demand-for-car-solar-roofs-skyrockets. html) 26 June 2008 Retrieved 11 October 2008[91] Electrical Review Vol 201 No 7 12 August 1977[92] Schmidt, Theodor. "Solar Ships for the new Millennium" (http:/ / www. umwelteinsatz. ch/ IBS/ solship2. html). TO Engineering. .Retrieved 2007-09-30.[93] "The sun21 completes the first transatlantic crossing with a solar powered boat" (http:/ / www. transatlantic21. org/ ). Transatlantic 21. .Retrieved 2007-09-30.[94] "PlanetSolar, the first solar-powered round-the-world voyage" (http:/ / www. planetsolar. org/ objectifs. en. shtml). PlanetSolar. . Retrieved2008-08-19.[95] Sunseeker Seeks New Records (http:/ / www. evworld. com/ article. cfm?storyid=709)[96] "Solar-Power Research and Dryden" (http:/ / www. nasa. gov/ centers/ dryden/ news/ FactSheets/ FS-054-DFRC. html). NASA. . Retrieved2008-04-30.[97] "The NASA ERAST HALE UAV Program" (http:/ / web. archive. org/ web/ 20080210021300/ http:/ / www. vectorsite. net/ twuav_15.html). Greg Goebel. Archived from the original (http:/ / www. vectorsite. net/ twuav_15. html#m7) on 2008-02-10. . Retrieved 2008-04-30.[98] "Phenomena which affect a solar balloon" (http:/ / pagesperso-orange. fr/ ballonsolaire/ en-theorie1. htm). pagesperso-orange.fr. . Retrieved2008-08-19.
25. 25. Solar energy 22[99] "Solar Sails Could Send Spacecraft Sailing Through Space" (http:/ / www. nasa. gov/ vision/ universe/ roboticexplorers/ solar_sails. html).National Aeronautics and Space Administration. . Retrieved 2007-11-26.[100] "High Altitude Airship" (http:/ / web. archive. org/ web/ 20080630010557/ http:/ / www. lockheedmartin. com/ products/HighAltitudeAirship/ index. html). Lockheed Martin. Archived from the original (http:/ / www. lockheedmartin. com/ products/HighAltitudeAirship/ index. html) on 2008-06-30. . Retrieved 2008-08-04.[101] Carr (1976), p. 85[102] Balcomb(1992), p. 6[103] "Request for Participation Summer 2005 Demand Shifting with Thermal Mass" (http:/ / www. drrc. lbl. gov/ pubs/ RFP_071405. pdf)(PDF). Demand Response Research Center. . Retrieved 2007-11-26.[104] Butti and Perlin (1981), p. 212214[105] "Advantages of Using Molten Salt" (http:/ / www. sandia. gov/ Renewable_Energy/ solarthermal/ NSTTF/ salt. htm). Sandia NationalLaboratory. . Retrieved 2007-09-29.[106] "PV Systems and Net Metering" (http:/ / web. archive. org/ web/ 20080704062311/ http:/ / www1. eere. energy. gov/ solar/ net_metering.html). Department of Energy. Archived from the original (http:/ / www1. eere. energy. gov/ solar/ net_metering. html) on 2008-07-04. .Retrieved 2008-07-31.[107] "Pumped Hydro Storage" (http:/ / web. archive. org/ web/ 20080621052054/ http:/ / www. electricitystorage. org/ tech/technologies_technologies_pumpedhydro. htm). Electricity Storage Association. Archived from the original (http:/ / www. electricitystorage.org/ tech/ technologies_technologies_pumpedhydro. htm) on 2008-06-21. . Retrieved 2008-07-31.[108] Butti and Perlin (1981), p. 63, 77, 101[109] Butti and Perlin (1981), p. 249[110] Yergin (1991), p. 634, 653-673[111] "Chronicle of Fraunhofer-Gesellschaft" (http:/ / www. fraunhofer. de/ EN/ company/ profile/ chronicle/ 1972-1982. jsp). Fraunhofer-Gesellschaft. . Retrieved 2007-11-04.[112] Butti and Perlin (1981), p. 117[113] Butti and Perlin (1981), p. 139[114] "IEA Says Solar May Provide a Third of Global Energy by 2060" (http:/ / www. businessweek. com/ news/ 2011-12-01/ iea-says-solar-may-provide-a-third-of-global-energy-by-2060. html). Bloomberg Businessweek. December 1, 2011. .References Agrafiotis, C.; Roeb, M.; Konstandopoulos, A.G.; Nalbandian, L.; Zaspalis, V.T.; Sattler, C.; Stobbe, P.; Steele,A.M. (2005). "Solar water splitting for hydrogen production with monolithic reactors". Solar Energy 79 (4):409421. doi:10.1016/j.solener.2005.02.026. Anderson, Lorraine; Palkovic, Rick (1994). Cooking with Sunshine (The Complete Guide to Solar Cuisine with150 Easy Sun-Cooked Recipes). Marlowe & Company. ISBN1-56924-300-X. Balcomb, J. Douglas (1992). Passive Solar Buildings. Massachusetts Institute of Technology.ISBN0-262-02341-5. Bnard, C.; Gobin, D.; Gutierrez, M. (1981). "Experimental Results of a Latent-Heat Solar-Roof, Used forBreeding Chickens". Solar Energy 26 (4): 347359. doi:10.1016/0038-092X(81)90181-X. Bolton, James (1977). Solar Power and Fuels. Academic Press, Inc.. ISBN0-12-112350-2. Bradford, Travis (2006). Solar Revolution: The Economic Transformation of the Global Energy Industry. MITPress. ISBN0-262-02604-X. Butti, Ken; Perlin, John (1981). A Golden Thread (2500 Years of Solar Architecture and Technology). VanNostrand Reinhold. ISBN0-442-24005-8. Carr, Donald E. (1976). Energy & the Earth Machine. W. W. Norton & Company. ISBN0-393-06407-7. Daniels, Farrington (1964). Direct Use of the Suns Energy. Ballantine Books. ISBN0-345-25938-6. Halacy, Daniel (1973). The Coming Age of Solar Energy. Harper and Row. ISBN0-380-00233-7. Hunt, V. Daniel (1979). Energy Dictionary. Van Nostrand Reinhold Company. ISBN0-442-27395-9. Karan, Kaul; Greer, Edith; Kasperbauer, Michael; Mahl, Catherine (2001). "Row Orientation Affects Fruit Yieldin Field-Grown Okra". Journal of Sustainable Agriculture 17 (2/3): 169174. doi:10.1300/J064v17n02_14. Leon, M.; Kumar, S. (2007). "Mathematical modeling and thermal performance analysis of unglazed transpiredsolar collectors". Solar Energy 81 (1): 6275. doi:10.1016/j.solener.2006.06.017.
26. 26. Solar energy23 Lieth, Helmut; Whittaker, Robert (1975). Primary Productivity of the Biosphere. Springer-Verlag1.ISBN0-387-07083-4. Martin, Christopher L.; Goswami, D. Yogi (2005). Solar Energy Pocket Reference. International Solar EnergySociety. ISBN0-9771282-0-2. Mazria, Edward (1979). The Passive Solar Energy Book. Rondale Press. ISBN0-87857-238-4. Meier, Anton; Bonaldi, Enrico; Cella, Gian Mario; Lipinski, Wojciech; Wuillemin, Daniel (2005). "Solarchemical reactor technology for industrial production of lime". Solar Energy 80 (10): 13551362.doi:10.1016/j.solener.2005.05.017. Mills, David (2004). "Advances in solar thermal electricity technology". Solar Energy 76 (1-3): 1931.doi:10.1016/S0038-092X(03)00102-6. Mller, Reto; Steinfeld, A. (2007). "Band-approximated radiative heat transfer analysis of a solar chemical reactorfor the thermal dissociation of zinc oxide". Solar Energy 81 (10): 12851294. doi:10.1016/j.solener.2006.12.006. Perlin, John (1999). From Space to Earth (The Story of Solar Electricity). Harvard University Press.ISBN0-674-01013-2. Bartlett, Robert (1998). Solution Mining: Leaching and Fluid Recovery of Materials. Routledge.ISBN90-5699-633-9. Scheer, Hermann (2002). The Solar Economy (Renewable Energy for a Sustainable Global Future) (http://www.hermannscheer.de/en/index.php?option=com_content&task=view&id=33&Itemid=7). Earthscan PublicationsLtd. ISBN1-84407-075-1. Schittich, Christian (2003). Solar Architecture (Strategies Visions Concepts). Architektur-Dokumentation GmbH& Co. KG. ISBN3-7643-0747-1. Smil, Vaclav (1991). General Energetics: Energy in the Biosphere and Civilization. Wiley. pp.369.ISBN0-471-62905-7. Smil, Vaclav (2003). Energy at the Crossroads: Global Perspectives and Uncertainties. MIT Press. pp.443.ISBN0-262-19492-9. Smil, Vaclav (2006-05-17) (PDF). Energy at the Crossroads (http://www.oecd.org/dataoecd/52/25/36760950.pdf). Organisation for Economic Co-operation and Development. ISBN0-262-19492-9. Retrieved2007-09-29. Tabor, H. Z.; Doron, B. (1990). "The Beith HaArava 5 MW(e) Solar Pond Power Plant (SPPP)--ProgressReport". Solar Energy 45 (4): 247253. doi:10.1016/0038-092X(90)90093-R. Tiwari, G. N.; Singh, H. N.; Tripathi, R. (2003). "Present status of solar distillation". Solar Energy 75 (5):367373. doi:10.1016/j.solener.2003.07.005. Tritt, T.; Bttner, H.; Chen, L. (2008). "Thermoelectrics: Direct Solar Thermal Energy Conversion" (http://www.mrs.org/s_mrs/bin.asp?CID=12527&DID=208641). MRS Bulletin 33 (4): 355372. Tzempelikos, Athanassios; Athienitis, Andreas K. (2007). "The impact of shading design and control on buildingcooling and lighting demand". Solar Energy 81 (3): 369382. doi:10.1016/j.solener.2006.06.015. Vecchia, A.; Formisano, W.; Rosselli, V; Ruggi, D. (1981). "Possibilities for the Application of Solar Energy inthe European Community Agriculture". Solar Energy 26 (6): 479489. doi:10.1016/0038-092X(81)90158-4. Yergin, Daniel (1991). The Prize: The Epic Quest for Oil, Money, and Power. Simon & Schuster. pp.885.ISBN0-671-79932-0. Zedtwitz, P.v.; Petrasch, J.; Trommer, D.; Steinfeld, A. (2006). "Hydrogen production via the solar thermaldecarbonization of fossil fuels". Solar Energy 80 (10): 13331337. doi:10.1016/j.solener.2005.06.007.
27. 27. Solar energy24External links "How do Photovoltaics Work?" (http://science.nasa.gov/headlines/y2002/solarcells.htm). NASA. Solar Energy Back in the Day (http://www.life.com/image/first/in-gallery/43861/solar-energy-back-in-the-day) - slideshow by Life magazine Compendium of Solar Cooker Designs (http://solarcooking.wikia.com/wiki/Compendium_of_solar_cooker_designs) U.S. Solar Farm Map (1 MW or Higher) (http://www.solarpowerworldonline.com/u-s-solar-farm-map/)Solar thermal energySolar thermal energy (STE) is a technology forharnessing solar energy for thermal energy (heat). Solarthermal collectors are classified by the United StatesEnergy Information Administration as low-, medium-, orhigh-temperature collectors. Low-temperature collectorsare flat plates generally used to heat swimming pools.Medium-temperature collectors are also usually flat platesbut are used for heating water or air for residential andcommercial use. High-temperature collectors concentratesunlight using mirrors or lenses and are generally used forelectric power production. STE is different from andmuch more efficient than[1][2][3] photovoltaics, which Solar thermal system for water heating in Santorini, Greece.converts solar energy directly into electricity. Whileexisting generation facilities provide only 600 megawatts of solar thermal power worldwide in October 2009, [4]plants for an additional 400 megawatts are under construction and development is underway for concentrated solarpower projects totalling 14,000 megawatts.[5]Low-temperature collectorsOf the 21000000 square feet (unknown operator: ustrong m2) of solar thermal collectors produced in the UnitedStates in 2007, 16000000 square feet (unknown operator: ustrong m2) were of the low-temperature variety.[6]Low-temperature collectors are generally installed to heat swimming pools, although they can also be used for spaceheating. Collectors can use air or water as the medium to transfer the heat to their destination.Heating, cooling, and ventilation