19346954 Photovoltaics


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19346954 Photovoltaics

  1. 1. PhotovoltaicsPhotovoltaic system tree in Styria, AustriaPhotovoltaic system (or PV) is the field of technology and research related to theapplication of solar cells for energy by converting solar energy (sunlight, including ultraviolet radiation) directly into electricity. Due to the growing demand for clean sources ofenergy, the manufacture of solar cells and photovoltaic arrays has expanded dramaticallyin recent years.[1][2][3]Photovoltaic production has been doubling every 2 years, increasing by an average of 48percent each year since 2002, making it the world’s fastest-growing energy technology.[4]At the end of 2008, the cumulative global PV installations reached 15,200 megawatts, a94% annual increase.[5][6] Roughly 90% of this generating capacity consists of grid-tiedelectrical systems. Such installations may be ground-mounted (and sometimes integratedwith farming and grazing) [7] or built into the roof or walls of a building, known asBuilding Integrated Photovoltaics or BIPV for short.[8]Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries includingAustralia, Germany, Israel,[9] Japan, and the United States.[1]
  2. 2. Contents[hide] • 1 Overview • 2 Current development • 3 Worldwide installed totals • 4 Applications o 4.1 Power stations o 4.2 In buildings o 4.3 In transport o 4.4 Standalone devices o 4.5 Rural electrification o 4.6 Solar roadways • 5 Performance o 5.1 Temperature o 5.2 Optimum Orientation of Solar Panels • 6 Economics o 6.1 Power costs o 6.2 Grid parity o 6.3 Financial incentives o 6.4 Investment • 7 Environmental impacts o 7.1 Greenhouse gases o 7.2 Cadmium o 7.3 Energy payback time and energy returned on energy invested • 8 Advantages • 9 Disadvantages • 10 Photovoltaics companies • 11 See also • 12 References • 13 External links o 13.1 Photovoltaic industry associations o 13.2 Photovoltaics research institutes o 13.3 Live data o 13.4 Others
  3. 3. [edit] OverviewPhotovoltaic cells produce electricity directly from sunlightPhotovoltaics are best known as a method for generating electric power by using solarcells to convert energy from the sun into electricity. The photovoltaic effect refers tophotons of light knocking electrons into a higher state of energy to create electricity. Theterm photovoltaic denotes the unbiased operating mode of a photodiode in which currentthrough the device is entirely due to the transduced light energy. Virtually all photovoltaicdevices are some type of photodiode.Solar cells produce direct current electricity from light, which can be used to powerequipment or to recharge a battery. The first practical application of photovoltaics was topower orbiting satellites and other spacecraft, but today the majority of photovoltaicmodules are used for grid connected power generation. In this case an inverter is requiredto convert the DC to AC. There is a smaller market for off grid power for remotedwellings, roadside emergency telephones, remote sensing, and cathodic protection ofpipelines.Average solar irradiance, watts per square metre. Note that this is for a horizontal surface,whereas solar panels are normally propped up at an angle and receive more energy perunit area. The small black dots show the area of solar panels needed to generate all of theworlds energy using 8% efficient photovoltaics.Cells require protection from the environment and are usually packaged tightly behind aglass sheet. When more power is required than a single cell can deliver, cells areelectrically connected together to form photovoltaic modules, or solar panels. A singlemodule is enough to power an emergency telephone, but for a house or a power plant themodules must be arranged in multiples as arrays. Although the selling price of modules isstill too high to compete with grid electricity in most places, significant financialincentives in Japan and then Germany, Italy and France triggered a huge growth indemand, followed quickly by production. In 2008, Spain installed 45% of allphotovoltaics, but a change in law limiting the Feed-in Tariff is expected to cause aprecipitous drop in installations there, from 2500 MW in 2008 to 375 MW in 2009.[10]Perhaps not unexpectedly, a significant market has emerged in off-grid locations forsolar-power-charged storage-battery based solutions. These often provide the onlyelectricity available.[11]The EPIA/Greenpeace Advanced Scenario shows that by the year 2030, PV systemscould be generating approximately 1,864 GW of electricity around the world. This meansthat, assuming a serious commitment is made to energy efficiency, enough solar power
  4. 4. would be produced globally in twenty-five years’ time to satisfy the electricity needs ofalmost 14% of the world’s population.[12][edit] Current developmentMap of solar electricity potential in EuropeThe most important issue with solar panels is capital cost (installation and materials).Newer alternatives to standard crystalline silicon modules including casting wafersinstead of sawing,[13] thin film (CdTe[14] CIGS,[15] amorphous Si,[16] microcrystalline Si),concentrator modules, Sliver cells, and continuous printing processes. Due to economiesof scale solar panels get less costly as people use and buy more — as manufacturersincrease production to meet demand, the cost and price is expected to drop in the years tocome. By early 2006, the average cost per installed watt for a residential sized systemwas about USD 7.50 to USD 9.50, including panels, inverters, mounts, and electricalitems.[17]In 2006 investors began offering free solar panel installation in return for a 25 yearcontract, or Power Purchase Agreement, to purchase electricity at a fixed price, normallyset at or below current electric rates.[18][19] It is expected that by 2009 over 90% ofcommercial photovoltaics installed in the United States will be installed using a powerpurchase agreement.[20] An innovative financing arrangement is being tested in Berkeley,California, which adds an amount to the property assessment to allow the city to pay forthe installed panels up front, which the homeowner pays for over a 20 year period at arate equal to the annual electric bill savings, thus allowing free installation for thehomeowner at no cost to the city.[21]The current market leader in solar panel efficiency (measured by energy conversion ratio)is SunPower, a San Jose based company. Sunpowers cells have a conversion ratio of23.4%, well above the market average of 12-18%. However, advances past this efficiencymark are being pursued in academia and R&D labs with efficiencies of 42% achieved atthe University of Delaware in conjunction with DuPont.[22]
  5. 5. [edit] Worldwide installed totals This section may stray from the topic of the article into the topic of another article, Deployment of solar power to energy grids. Please help improve this section or discuss this issue on the talk page.See also: Deployment of solar power to energy grids and History of photovoltaics Wikinews has related news: • PV Taiwan 2007 starts with photovoltaic solutions and applications • PV Taiwan 2007: ITRI Taiwan awards winners of Jinyi Award and shows the solutions on photovoltaic industryWorld solar photovoltaic (PV) installations were 2.826 gigawatts peak (GWp) in 2007,and 5.95 gigawatts in 2008, a 110% increase.[23][24] The three leading countries (Germany,Japan and the US) represent nearly 89% of the total worldwide PV installed capacity.Germany was the fastest growing major PV market in the world from 2006 to 2007. By2008, 5.337 GWp of PV was installed, or 35% of the world total.[6] The German PVindustry generates over 10,000 jobs in production, distribution and installation. By theend of 2006, nearly 88% of all solar PV installations in the EU were in grid-tiedapplications in Germany.[1] Photovoltaic power capacity is measured as maximum poweroutput under standardized test conditions (STC) in "Wp" (Watts peak).[25] The actualpower output at a particular point in time may be less than or greater than thisstandardized, or "rated," value, depending on geographical location, time of day, weatherconditions, and other factors.[26] Solar photovoltaic array capacity factors are typicallyunder 25%, which is lower than many other industrial sources of electricity.[27] Thereforethe 2008 installed base peak output would have provided an average output of 3.04 GW(assuming 20% × 15,200 MWp). This represented 0.15 percent of global demand at thetime.[28] Produced, Installed & Total Photovoltaic Peak Power Capacity (MWp) as of the end of 2007 Feed-in off on Installed off on Total Wp/capita Module kW·h/kWp·yrCountry or Region Tariff grid grid 2007 grid grid 2007 Total Price Insolation Report Nat. Int. EU¢/kW·h Δ Δ Σ Σ €/WpGermany[29][30] 35 1,100 1,135 35 3,827 3,862 46.8 4.0–5.3 1,000–1,300[31] 51.8–56.8Japan[30][32] 1.562 208.8 210.4 90.15 1,829 1,919 15 2.96 1,200–1,600 Ended(2005) 1.2–United States[30][33] 55 151.5 206.5 325 505.5 830.5 2.8 2.98 900–2,150[31] 31.04(CA)Spain ?[30] 22 490 512 29.8 625.2 655 15.1 3.0–4.5 1,600–2,200 18.38–44.04Italy[30][34] 0.3 69.9 70.2 13.1 107.1 120.2 2.1 3.2–3.6 1,400–2,200 36.0–49.0 0–Australia[30][35] 5.91 6.28 12.19 66.45 16.04 82.49 4.1 4.5–5.4 1,450–2,902[36] 26.4(SA08)South Korea[30][37] 0 42.87 42.87 5.943 71.66 77.60 1.6 3.50– 1,500–1,600 56.5–59.3
  6. 6. 3.84 [30][38]France 0.993 30.31 31.30 22.55 52.68 75.23 1.2 3.2–5.1 1,100–2,000 30.0–55.0Netherlands[30][39] 0.582 1.023 1.605 5.3 48 53.3 3.3 3.3–4.5 1,000–1,200 1.21–9.7 3.18–Switzerland[30][40] 0.2 6.3 6.5 3.6 32.6 36.2 4.9 1,200–2,000 9.53–50.8 3.30Austria ?[30] 0.055 2.061 2.116 3.224 24.48 27.70 3.4 3.6–4.3 1,200–2,000 >0Canada[30][41] 3.888 1.403 5.291 22.86 2.911 25.78 0.8 3.76 900–1,750 0–29.48(ON) 5.44–Mexico ?[30] 0.869 0.15 1.019 20.45 0.3 20.75 0.2 1,700–2,600 None 6.42United 3.67– 0– 0.16 3.65 3.81 1.47 16.62 18.09 0.3 900–1,300Kingdom[30][42] 5.72 11.74(exprt)Portugal ?[43] 0.2 14.25 14.45 2.841 15.03 17.87 1.7 1,600–2,200Norway[30][44] 0.32 0.004 0.324 7.86 0.132 7.992 1.7 11.2 800–950 None 3.24–Sweden[30][45] 0.271 1.121 1.392 4.566 1.676 6.242 0.7 900–1,050 None 7.02 5.36–Denmark[30][46] 0.05 0.125 0.175 0.385 2.69 3.075 0.6 900–1,100 None 8.04 Israel[30][47] 0.5 0 0.5 1.794 0.025 1.819 0.3 4.3 2,200–2,400 13.13–16.40 World(Total of countries 127.9 2,130 2,258 662.3 7,178 7,841 2.5–11.2 800–2,902 0–59.3listed) off on off on Module Feed-inCountry or Region Installed Total Wp/capita kW·h/kWp·yr grid grid grid grid Price Tariff Report Nat. Int. 2007 2007 Total Insolation Δ Δ Σ Σ €/Wp EU¢/kW·hNotes: Off grid refers to photovoltaics which are not grid connected. On grid means connected to the localelectricity grid. Δ means the amount installed during the previous year. Σ means the total amount installed.Wp/capita refers to the ratio of total installed capacity divided by total population, or total installed Wp perperson. Module price is average installed price, in Euros. kW·h/kWp·yr indicates the range of insolation tobe expected. While National Report(s) may be cited as source(s) within an International Report, anycontradictions in data are resolved by using only the most recent reports data. Exchange rates represent the2006 annual average of daily rates (OECD Main Economic Indicators June 2007).Module Price: Lowest:2.5 EUR/Wp[30] (2.83 USD/Wp[48]) in Germany 2003. Uncited insolation data is frommaps dating 1991-1995.PV Power (2007-June)[43][49] IEA PVPS website.[edit] ApplicationsMain article: Photovoltaic system[edit] Power stationsMain article: List of photovoltaic power stations
  7. 7. Solar array at Nellis Air Force Base. These panels track the sun in one axis.As of April 2009, the largest photovoltaic (PV) power plants in the world are theOlmedilla Photovoltaic Park (Spain, 60 MW), the Puertollano Photovoltaic Park (Spain,50 MW), the Moura photovoltaic power station (Portugal, 46 MW), and the WaldpolenzSolar Park (Germany, 40 MW).[50]The 14 MW Nellis Solar Power Plant is the largest solar photovoltaic system in NorthAmerica,[51] and is located within Nellis Air Force Base in Clark County, Nevada, on thenortheast side of Las Vegas. The Nellis solar energy system will generate in excess of25 million kilowatt-hours of electricity annually and supply more than 25 percent of thepower used at the base.[52] Worlds largest photovoltaic (PV) power plants (30 MW or larger)[50] DC Name of PV power Peak GW·h Capacity Country Notes plant Power /year factor (MW)Olmedilla Completed September Spain 60 85 0.16Photovoltaic Park 2008Puertollano Spain 50 2008Photovoltaic ParkMoura photovoltaic Completed December Portugal 46 93 0.16power station [53] 2008 550,000 First Solar thin-Waldpolenz Solar film CdTe modules. Germany 40 40 0.11Park[54][55] Completed December 2008Arnedo Solar Plant Spain 34 Completed October 2008Merida/Don Alvaro Completed September Spain 30Solar Park 2008Planta Solar LaMagascona & La Spain 30MagasquilaPlanta Solar Ose de Spain 30la Vega
  8. 8. Topaz Solar Farm is a proposed 550 MW solar photovoltaic power plant which is to bebuilt northwest of California Valley in the US at a cost of over $1 billion.[56] Built on9.5 square miles (25 km2) of ranchland,[57] the project would utilize thin-film PV panelsdesigned and manufactured by OptiSolar in Hayward and Sacramento. The project woulddeliver approximately 1,100 gigawatt-hours (GW·h) annually of renewable energy. Theproject is expected to begin construction in 2010,[57] begin power delivery in 2011, and befully operational by 2013.[58]High Plains Ranch is a proposed 250 MW solar photovoltaic power plant which is to bebuilt by SunPower in the Carrizo Plain, northwest of California Valley.[58][edit] In buildingsMain article: Building-integrated photovoltaicsPhotovoltaic solar panels on a house roof.Building-integrated photovoltaics (BIPV) are increasingly incorporated into newdomestic and industrial buildings as a principal or ancillary source of electrical power,[59]and are one of the fastest growing segments of the photovoltaic industry.[60] Typically, anarray is incorporated into the roof or walls of a building, and roof tiles with integrated PVcells can now be purchased. Arrays can also be retrofitted into existing buildings; in thiscase they are usually fitted on top of the existing roof structure. Alternatively, an arraycan be located separately from the building but connected by cable to supply power forthe building.Where a building is at a considerable distance from the public electricity supply (or grid)- in remote or mountainous areas – PV may be the preferred possibility for generatingelectricity, or PV may be used together with wind, diesel generators and/or hydroelectricpower. In such off-grid circumstances batteries are usually used to store the electricpower.In locations near the grid, however, feeding the grid using PV panels is more practical,and leads to optimum use of the investment in the photovoltaic system. This requires bothregulatory and commercial preparation, including net-metering and feed-in agreements.To provide for possible power failure, some grid tied systems are set up to allow local use
  9. 9. disconnected from the grid. Most photovoltaics are grid connected. In the event the gridfails, the local system must not feed the grid to prevent the possible creation of dangerousislanding.The power output of photovoltaic systems for installation in buildings is usuallydescribed in kilowatt-peak units (kWp).[edit] In transportMain article: Photovoltaics in transportPV has traditionally been used for auxiliary power in space. PV is rarely used to providemotive power in transport applications, but is being used increasingly to provide auxiliarypower in boats and cars. Recent advances in solar race cars, however, have produced carsthat with little changes could be used for transportation.[61][edit] Standalone devicesSolar parking meter.Until a decade or so ago, PV was used frequently to power calculators and noveltydevices. Improvements in integrated circuits and low power LCD displays make itpossible to power such devices for several years between battery changes, making PV useless common. In contrast, solar powered remote fixed devices have seen increasing userecently in locations where significant connection cost makes grid power prohibitivelyexpensive. Such applications include parking meters,[62] emergency telephones,[63]temporary traffic signs, and remote guard posts & signals.[edit] Rural electrificationDeveloping countries where many villages are often more than five kilometers away fromgrid power have begun using photovoltaics. In remote locations in India a rural lightingprogram has been providing solar powered LED lighting to replace kerosene lamps. Thesolar powered lamps were sold at about the cost of a few months supply of
  10. 10. kerosene.[64][65] Cuba is working to provide solar power for areas that are off grid.[66] Theseare areas where the social costs and benefits offer an excellent case for going solar thoughthe lack of profitability could relegate such endeavors to humanitarian goals.[edit] Solar roadwaysMain article: Solar roadwayA 45 mi (72 km) section of roadway in Idaho is being used to test the possibility ofinstalling solar panels into the road surface, as roads are generally unobstructed to the sunand represent about the percentage of land area needed to replace other energy sourceswith solar power.[67][edit] Performance[edit] TemperatureGenerally, temperatures above room temperature reduce the performance ofphotovoltaics.[68][edit] Optimum Orientation of Solar PanelsFor best performance, PV systems aim to maximize the time they face the sun. Solartrackers aim to achieve this by moving PV panels to follow the sun. The increase can beby as much as 20% in winter and by as much as 50% in summer. Static mounted systemscan be optimized by analysis of the Sun path. Panels are often set to latitude tilt, an angleequal to the latitude, but performance can be improved by adjusting the angle for summerand winter.[edit] Economics This section may stray from the topic of the article into the topic of another article, Renewable energy commercialization. Please help improve this section or discuss this issue on the talk page. This section may contain original research or unverified claims. Please improve the article by adding references. See the talk page for details. (September 2007)See also: Renewable energy commercialization
  11. 11. US average daily solar energy insolation received by a latitude tilt photovoltaic cell. In photovoltaics, the solar value added chain is the set of steps from sand or raw silicon to the completed solar module and photovoltaic system completion and installation[69]. [edit] Power costs The PV industry is beginning to adopt levelized cost of energy (LCOE) as the unit of cost. For a 10 MW plant in Phoenix, AZ, the LCOE is estimated at $0.15 to 0.22/kWh in 2005.[70] The table below is a pure mathematical calculation. It illustrates the calculated total cost in US cents per kilowatt-hour of electricity generated by a photovoltaic system as function of the investment cost and the efficiency, assuming some accounting parameters such as cost of capital and depreciation period. The row headings on the left show the total cost, per peak kilowatt (kWp), of a photovoltaic installation. The column headings across the top refer to the annual energy output in kilowatt-hours expected from each installed peak kilowatt. This varies by geographic region because the average insolation depends on the average cloudiness and the thickness of atmosphere traversed by the sunlight. It also depends on the path of the sun relative to the panel and the horizon. Panels can be mounted at an angle based on latitude,[71] or solar tracking can be utilized to access even more perpendicular sunlight, thereby raising the total energy output. The calculated values in the table reflect the total cost in cents per kilowatt-hour produced. They assume a 10% total capital cost (for instance 4% interest rate, 1% operating and maintenance cost, and depreciation of the capital outlay over 20 years). Table showing average cost in cents/kWh over 20 years for solar power panels InsolationCost 2400 2200 2000 1800 1600 1400 1200 1000 800 kWh/kWp•y kWh/kWp•y kWh/kWp•y kWh/kWp•y kWh/kWp•y kWh/kWp•y kWh/kWp•y kWh/kWp•y kWh/kWp•y 200$/kW 0.8 0.9 1.0 1.1 1.3 1.4 1.7 2.0 2.5 p 600 2.5 2.7 3.0 3.3 3.8 4.3 5.0 6.0 7.5$/kW
  12. 12. p1000$/kW 4.2 4.5 5.0 5.6 6.3 7.1 8.3 10.0 12.5 p1400$/kW 5.8 6.4 7.0 7.8 8.8 10.0 11.7 14.0 17.5 p1800$/kW 7.5 8.2 9.0 10.0 11.3 12.9 15.0 18.0 22.5 p2200$/kW 9.2 10.0 11.0 12.2 13.8 15.7 18.3 22.0 27.5 p2600$/kW 10.8 11.8 13.0 14.4 16.3 18.6 21.7 26.0 32.5 p3000$/kW 12.5 13.6 15.0 16.7 18.8 21.4 25.0 30.0 37.5 p3400$/kW 14.2 15.5 17.0 18.9 21.3 24.3 28.3 34.0 42.5 p3800$/kW 15.8 17.3 19.0 21.1 23.8 27.1 31.7 38.0 47.5 p4200$/kW 17.5 19.1 21.0 23.3 26.3 30.0 35.0 42.0 52.5 p
  13. 13. 4600$/kW 19.2 20.9 23.0 25.6 28.8 32.9 38.3 46.0 57.5 p5000$/kW 20.8 22.7 25.0 27.8 31.3 35.7 41.7 50.0 62.5 p Physicists have claimed that recent technological developments bring the cost of solar energy more in parity with that of fossil fuels. In 2007, David Faiman, the director of the Ben-Gurion National Solar Energy Center of Israel, announced that the Center had entered into a project with Zenith Solar to create a home solar energy system that uses a 10 square meter reflector dish.[72] In testing, the concentrated solar technology proved to be up to five times more cost effective than standard flat photovoltaic silicon panels, which would make it almost the same cost as oil and natural gas.[73] A prototype ready for commercialization achieved a concentration of solar energy that was more than 1,000 times greater than standard flat panels.[74] [edit] Grid parity Further information: Low-cost solar cell and Solar America Initiative Grid parity, the point at which photovoltaic electricity is equal to or cheaper than grid power, is achieved first in areas with abundant sun and high costs for electricity such as in California and Japan.[75] Grid parity has been reached in Hawaii and other islands that otherwise use fossil fuel (diesel fuel) to produce electricity, and most of the US is expected to reach grid parity by 2015.[76][77] General Electrics Chief Engineer predicts grid parity without subsidies in sunny parts of the United States by around 2015. Other companies predict an earlier date:[78] the cost of solar power will be below grid parity for more than half of residential customers and 10% of commercial customers in the OECD, as long as grid electricity prices do not decrease through 2010.[79] The fully-loaded cost (cost not price) of solar electricity is $0.25/kWh or less in most of the OECD countries. By late 2011, the fully-loaded cost is likely to fall below $0.15/kWh for most of the OECD and reach $0.10/kWh in sunnier regions. These cost levels are driving three emerging trends:[79] 1. vertical integration of the supply chain; 2. origination of power purchase agreements (PPAs) by solar power companies;
  14. 14. 3. unexpected risk for traditional power generation companies, grid operators and wind turbine manufacturers.Abengoa Solar has announced the award of two R&D projects in the field ofConcentrating Solar Power (CSP) by the US Department of Energy that total over $14million. The goal of the DOE R&D program, working in collaboration with partners suchas Abengoa Solar, is to develop CSP technologies that are competitive with conventionalenergy sources (grid parity) by 2015.[80] Concentrating photovoltaics (CPV) could reachgrid parity in 2011.[edit] Financial incentivesMain article: PV financial incentivesHow do we become number one in the world in terms of solar power generation? Inorder to achieve this, we must put an end to the following vicious cycle: costs are highbecause of lack of demand, and demand remains stagnant due to high costs. Above allelse, I think a strong political will to create demand through policies, is necessary. -Japanese Prime Minister Taro AsoThe political purpose of incentive policies for PV is to facilitate an initial small-scaledeployment to begin to grow the industry, even where the cost of PV is significantlyabove grid parity, to allow the industry to achieve the economies of scale necessary toreach grid parity. The policies are implemented to promote national energy independence,high tech job creation and reduction of CO2 emissions.Three incentive mechanisms are used (often in combination): • investment subsidies: the authorities refund part of the cost of installation of the system, • Feed-in Tariffs (FIT)/Net metering: the electricity utility buys PV electricity from the producer under a multiyear contract at a guaranteed rate. • Renewable Energy Certificates ("RECs")With investment subsidies, the financial burden falls upon the taxpayer, while with feed-in tariffs the extra cost is distributed across the utilities customer bases. While theinvestment subsidy may be simpler to administer, the main argument in favour of feed-intariffs is the encouragement of quality. Investment subsidies are paid out as a function ofthe nameplate capacity of the installed system and are independent of its actual poweryield over time, thus rewarding the overstatement of power and tolerating poor durabilityand maintenance. Some electric companies offer rebates to their customers, such asAustin Energy in Texas, which offers $4.50/watt installed up to $13,500.[81]With feed-in tariffs, the financial burden falls upon the consumer. They reward thenumber of kilowatt-hours produced over a long period of time, but because the rate is setby the authorities, it may result in perceived overpayment. The price paid per kilowatt-
  15. 15. hour under a feed-in tariff exceeds the price of grid electricity. Net metering refers to thecase where the price paid by the utility is the same as the price charged. Net metering isparticularly important because it can be done with no changes to standard electricitymeters, which accurately measure power in both directions and automatically report thedifference, and because it allows homeowners and businesses to generate electricity at adifferent time from consumption, effectively using the grid as a giant storage battery. Asmore photovoltaics are used ultimately storage will need to be provided, normally in theform of pumped hydro-storage. Normally with net metering deficits are billed eachmonth, while surpluses are rolled over to the following month and paid annually.Where price setting by supply and demand is preferred, RECs can be used. In thismechanism, a renewable energy production or consumption target is set, and theconsumer or producer is obliged to purchase renewable energy from whoever provides itthe most competitively. The producer is paid via an REC. In principle this system deliversthe cheapest renewable energy, since the lowest bidder will win. However, uncertaintiesabout the future value of energy produced are a brake on investment in capacity, and thehigher risk increases the cost of capital borrowed.The Japanese government through its Ministry of International Trade and Industry ran asuccessful programme of subsidies from 1994 to 2003. By the end of 2004, Japan led theworld in installed PV capacity with over 1.1 GW.[82]In 2004, the German government introduced the first large-scale feed-in tariff system,under a law known as the EEG (Erneuerbare Energien Gesetz) which resulted inexplosive growth of PV installations in Germany. At the outset the FIT was over 3x theretail price or 8x the industrial price. The principle behind the German system is a 20 yearflat rate contract. The value of new contracts is programmed to decrease each year, inorder to encourage the industry to pass on lower costs to the end users. The programmehas been more successful than expected with over 1GW installed in 2006, and politicalpressure is mounting to decrease the tariff to lessen the future burden on consumers.Subsequently Spain, Italy, Greece (who enjoyed an early success with domestic solar-thermal installations for hot water needs) and France introduced feed-in tariffs. Nonehave replicated the programmed decrease of FIT in new contracts though, making theGerman incentive relatively less and less attractive compared to other countries. TheFrench and Greek FIT offer a high premium (EUR 0.55/kWh) for building integratedsystems. California, Greece, France and Italy have 30-50% more insolation thanGermany making them financially more attractive. The Greek domestic "solar roof"programme (adopted in June 2009 for installations up to 10 kW) has internal rates ofreturn of 10-15% at current commercial installation costs, which, furthermore, is tax free.In 2006 California approved the California Solar Initiative, offering a choice ofinvestment subsidies or FIT for small and medium systems and a FIT for large systems.The small-system FIT of $0.39 per kWh (far less than EU countries) expires in just 5years, and the alternate "EPBB" residential investment incentive is modest, averaging
  16. 16. perhaps 20% of cost. All California incentives are scheduled to decrease in the futuredepending as a function of the amount of PV capacity installed.At the end of 2006, the Ontario Power Authority (Canada) began its Standard OfferProgram, the first in North America for small renewable projects (10MW or less). Thisguarantees a fixed price of $0.42 CDN per kWh over a period of twenty years. Unlike netmetering, all the electricity produced is sold to the OPA at the SOP rate. The generatorthen purchases any needed electricity at the current prevailing rate (e.g., $0.055 perkWh). The difference should cover all the costs of installation and operation over the lifeof the contract.The price per kilowatt hour or per peak kilowatt of the FIT or investment subsidies isonly one of three factors that stimulate the installation of PV. The other two factors areinsolation (the more sunshine, the less capital is needed for a given power output) andadministrative ease of obtaining permits and contracts.Unfortunately the complexity of approvals in California, Spain and Italy has preventedcomparable growth to Germany even though the return on investment is better.In some countries, additional incentives are offered for BIPV compared to stand alonePV. • France + EUR 0.25/kWh (EUR 0.30 + 0.25 = 0.55/kWh total) • Italy + EUR 0.04-0.09 kWh • Germany + EUR 0.05/kWh (facades only)[edit] InvestmentThere is an International Conference on Solar Photovoltaic Investments organized byEPIA.[83][edit] Environmental impacts This section may stray from the topic of the article into the topic of another article, Solar power. Please help improve this section or discuss this issue on the talk page.Unlike fossil fuel based technologies, solar power does not lead to any harmful emissionsduring operation, but the production of the panels leads to some amount of pollution. Thisis often referred to as the energy input to output ratio. In some analysis, if the energyinput to produce it is higher than the output it produces it can be consideredenvironmentally more harmful than beneficial. Also, placement of photovoltaics affectsthe environment. If they are located where photosynthesizing plants would normallygrow, they simply substitute one potentially renewable resource (biomass) for another. Itshould be noted, however, that the biomass cycle converts solar radiation energy tochemical energy ( with significantly less efficiency than photovoltaic cells alone). And if
  17. 17. they are placed on the sides of buildings (such as in Manchester) or fences, or rooftops(as long as plants would not normally be placed there), or in the desert they are purelyadditive to the renewable power base.[citations needed][edit] Greenhouse gasesLife cycle greenhouse gas emissions are now in the range of 25-32 g/kWh and this coulddecrease to 15 g/kWh in the future.[84] For comparison, a combined cycle gas-fired powerplant emits some 400 g/kWh and a coal-fired power plant 915 g/kWh and with carboncapture and storage some 200 g/kWh. Only nuclear power and wind are better, emitting6-25 g/kWh and 11 g/kWh on average. Using renewable energy sources in manufacturingand transportation would further drop carbon emissions. BP Solar owns two factoriesbuilt by Solarex (one in Maryland, the other in Virginia) in which all of the energy usedto manufacture solar panels is produced by solar panels.[edit] CadmiumOne issue that has often raised concerns is the use of cadmium in cadmium telluride solarcells (CdTe is only used in a few types of PV panels). Cadmium in its metallic form is atoxic substance that has the tendency to accumulate in ecological food chains. Theamount of cadmium used in thin-film PV modules is relatively small (5-10 g/m²) andwith proper emission control techniques in place the cadmium emissions from moduleproduction can be almost zero. Current PV technologies lead to cadmium emissions of0.3-0.9 microgram/kWh over the whole life-cycle.[84] Most of these emissions actuallyarise through the use of coal power for the manufacturing of the modules, and coal andlignite combustion leads to much higher emissions of cadmium. Life-cycle cadmiumemissions from coal is 3.1 microgram/kWh, lignite 6.2, and natural gas 0.2microgram/kWh.Note that if electricity produced by photovoltaic panels were used to manufacture themodules instead of electricity from burning coal, cadmium emissions from coal powerusage in the manufacturing process could be entirely eliminated.[edit] Energy payback time and energy returned on energy investedThe energy payback time is the time required to produce an amount of energy as great aswhat was consumed during production. The energy payback time is determined from alife cycle analysis of energy.Another key indicator of environmental performance, tightly related to the energypayback time, is the ratio of electricity generated divided by the energy required to buildand maintain the equipment. This ratio is called the energy returned on energy invested(EROEI). Of course, little is gained if it takes as much energy to produce the modules asthey produce in their lifetimes. This should not be confused with the economic return oninvestment, which varies according to local energy prices, subsidies available andmetering techniques.
  18. 18. Life-cycle analyses show that the energy intensity of typical solar photovoltaictechnologies is rapidly evolving. In 2000 the energy payback time was estimated as 8 to11 years[85], but more recent studies suggest that technological progress has reduced thisto 1.5 to 3.5 years for crystalline silicon PV systems [84].Thin film technologies now have energy pay-back times in the range of 1-1.5 years(S.Europe).[84] With lifetimes of such systems of at least 30 years, the EROEI is in therange of 10 to 30. They thus generate enough energy over their lifetimes to reproducethemselves many times (6-31 reproductions, the EROEI is a bit lower) depending onwhat type of material, balance of system (or BOS), and the geographic location of thesystem.[86][edit] AdvantagesThe 89 petawatts of sunlight reaching the Earths surface is plentiful - almost 6,000 timesmore than the 15 terawatts of average electrical power consumed by humans.[87]Additionally, solar electric generation has the highest power density (global mean of 170W/m²) among renewable energies.[87]Solar power is pollution-free during use. Production end-wastes and emissions aremanageable using existing pollution controls. End-of-use recycling technologies areunder development.[88]PV installations can operate for many years with little maintenance or intervention aftertheir initial set-up, so after the initial capital cost of building any solar power plant,operating costs are extremely low compared to existing power technologies.Solar electric generation is economically superior where grid connection or fuel transportis difficult, costly or impossible. Long-standing examples include satellites, islandcommunities, remote locations and ocean vessels.When grid-connected, solar electric generation replaces some or all of the highest-costelectricity used during times of peak demand (in most climatic regions). This can reducegrid loading, and can eliminate the need for local battery power to provide for use intimes of darkness. These features are enabled by net metering. Time-of-use net meteringcan be highly favorable, but requires newer electronic metering, which may still beimpractical for some users.Grid-connected solar electricity can be used locally thus reducingtransmission/distribution losses (transmission losses in the US were approximately 7.2%in 1995).[89]Compared to fossil and nuclear energy sources, very little research money has beeninvested in the development of solar cells, so there is considerable room forimprovement. Nevertheless, experimental high efficiency solar cells already have
  19. 19. efficiencies of over 40% and efficiencies are rapidly rising while mass-production costsare rapidly falling.[90][edit] DisadvantagesA major drawback is the area of land required for solar power generation. The 550MWCalifornia plant that is planned requires 9.5 square miles. Many areas of the world couldnot find this amount of unused land for this type of project.[citation needed] At the same time,photovoltaics take up no land at all when installed on existing rooftops or on land nototherwise used, such as decommissioned coal pits or in deserts.Depending on the cost of the installation and local electric rates the payback can be 14–20 years.[citation needed] While the modules are often warranted for upwards of 20 years, aninvestment in a home-mounted system is mostly lost if you move. The city of Berkeleyhas come up with an innovative financing method to remove this limitation, by adding atax assessment that is transferred with the home to pay for the solar panels.[91]Solar electricity is seen to be expensive. Once a PV system is installed it will produceelectricity for no further cost until the inverter needs replacing (about 12 years[citation needed]).Current utility rates have increased every year for the past 20 years[citation needed] and with theincreasing pressure on carbon reduction the rate will increase more aggressively[citationneeded] . This increase will (in the long run) easily offset the increased cost at installation butthe timetable for payback is too long for most.Solar electricity is not available at night and is less available in cloudy weather conditionsfrom conventional silicon based-technologies. Therefore, a storage or complementarypower system is required. However, the use of germanium in amorphous silicon-germanium thin-film solar cells provides residual power generating capacity at night dueto background infrared radiation.[citation needed] Fortunately, most power consumption isduring the day, so solar does not need to be stored at all as long to the extent that it offsetspeak and "shoulder" consumption.[citation needed]Apart from their own efficiency figures, PV systems work within the limited powerdensity of their locations insolation. Average daily insolation (output of a flat platecollector at latitude tilt) in the contiguous US is 3-7 kilowatt·h/m²[92][93][94][95] and onaverage lower in Europe.Solar cells produce DC which must be converted to AC (using a grid tie inverter) whenused in current existing distribution grids. This incurs an energy loss of 4-12%.[96][edit] Photovoltaics companiesMain article: List of photovoltaics companies[edit] See also
  20. 20. Energy portal Environment portalSustainable development portal • Active solar • American Solar Energy Society • Carbon nanotubes in photovoltaics • Clean Energy Bank • Concentrator photovoltaics • Deployment of solar power to energy grids • Distributed Energy Resources • Distributed generation • Electranet • Green technology • Grid-tied electrical system • High efficiency solar cells • History of photovoltaics • Infrared • Islanding • Investment fund • Maximum power point tracker • Microgeneration • Microgeneration Certification Scheme • Photoelectrochemical cell • Photovoltaic and renewable energy engineering in Australia • Photovoltaics in transport • Renewable energy • Renewable energy in the European Union • Solar vehicle • Solar thermal energy • Solar Today • Solar energy • Solar cell • Solar panel • Solar air conditioning • Thin-film solar cell • World Council for Renewable Energy