Solar power

Solar power is the conversion of energy from sunlight into electricity , Either Directly using photovoltaics (PV) Indirectly using Concentrated solar power , gold combination. Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of ​​sunlight into a small beam. Photovoltaic cells convert light into an electric current using the photovoltaic effect . [1]

Photovoltaics have been developed from a single source of electricity for small and medium-sized applications, from the calculator powered by an off-grid rooftop PV system. Commercial concentrated solar power plants were first developed in the 1980s. The 392 MW Ivanpah facility is the largest concentrating solar power plant in the world, located in the Mojave Desert of California .

As the cost of solar electricity has fallen, the number of grid-connected solar PV systems has grown into the millions and utility-scale solar power stations are being built. Solar PV is rapidly becoming an inexpensive, low-carbon technology to harness renewable energy from the Sun. The current largest photovoltaic power station in the world is the 850 MW Longyangxia Solar Dam Park, in Qinghai , China .

The international energy agency projected in 2014 that under its “high renewables” scenario, by 2050, solar photovoltaics and concentrated solar power would contribute to 16 and 11 percent, respectively, of the world’s largest electricity supply electricity. Most solar installations would be in China and India . [2] Currently, as of 2016, solar power provides just 1% of total worldwide electricity production, but is growing at 33% per annum.

Mainstream technologies

Many Industrialized nations-have significant installed solar power capacity into Their grids to supplement or alternative to Provide year conventional energy sources while year Increasing number of less Developed nations-have turned to solar to Reduce dependence is expensive imported fuels (see solar power by country ) . Long distance transmission allows remote renewable energy resources to displace fossil fuel consumption. Solar power plants use one of two technologies:

  • Photovoltaic (PV) systems use solar panels , Either one rooftops or in ground-mounted solar farms , converting sunlight into electric power Directly.
  • Concentrated solar power (CSP, Also Known As “Concentrated solar thermal”) plants use thermal solar energy to make steam, That Is thereafter converted into electricity by a turbine.

Photovoltaics

A solar cell , or photovoltaic cell (PV), is a device that converts light into an electric current using the photovoltaic effect . The first solar cell was constructed by Charles Fritts in the 1880s. [4] The German industrialist Ernst Werner von Siemens was among those who recognized the importance of this discovery. [5] In 1931, the German engineer Bruno Lange developed a photo cell using silver selenide in place of copper oxide , [6] while the prototype selenium cells converted less than 1% of incident light into electricity. Following the work of Russell Ohlin the 1940s, Gerald Pearson, Calvin Fuller and Daryl Chapin researchers created the silicon solar cell in 1954. [7] These early solar cells cost 286 USD / watt and reached efficiencies of 4.5-6%. [8]

Conventional PV systems

The array of a photovoltaic power system , or PV system, produces direct current (DC) power which fluctuates with the sunlight intensity. For practical use, this usually requires conversion to some desired voltages or alternating current (AC), through the use of inverters . [3] Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC, the desired frequency / phase. [3]

Many residential PV systems are connected to the grid where available, especially in developed countries with large markets. [9] In these grid-connected PV systems , the use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight.

Concentrated solar power

Concentrated solar power (CSP), also called “concentrated solar thermal”, uses lenses or mirrors and tracking systems to focus a large area of ​​sunlight into a small beam. Controlled to photovoltaics – which converts light directly into electricity – CSP uses the heat of the sun’s radiation to generate electricity from steam-driven turbines.

A wide range of concentrating technologies exists: among the best known are the parabolic trough , the compact linear Fresnel reflector , the Stirling dish and the solar power tower . Various techniques are used on the sun and focus light. In all of These systems a working fluid is heated by the Concentrated sunlight, and is used for power generation Then gold energy storage. [10]Thermal storage works up to 24-hour electricity generation. [11]

parabolic trough consists of a linear parabolic reflector that concentrates light on a storeroom along the reflector’s focal line. The receiver is one of the focal points of the linear parabolic mirror and is filled with a working fluid. The reflector is made to follow the day by tracking along a single axis. Parabolic trough systems provide the best [12] The SEGS plants in California and Acciona’s Nevada Solar One near Boulder City, Nevada are representatives of this technology. [13] [14]

Compact Linear Fresnel Reflectors are CSP-Plates that use many thin mirrors instead of parabolic mirrors to concentrate sunlight onto two tubes with working fluid. This is the advantage that can be used in other ways than other mirrors, and that it may be more important than other aspects of the environment. Concentrating linear fresnel reflectors can be used in large or larger compact plants. [15] [16]

The Stirling Solar Dish combines a parabolic concentrating dish with a Stirling engine which normally drives an electric generator. The advantages of Stirling solar over photovoltaic cells are higher efficiency of converting sunlight into electricity and longer lifetime. Parabolic dish systems give the highest efficiency among CSP technologies. [17] The 50 kilowatts Big Dish in Canberra , Australia is an example of this technology. [13]

solar power tower uses an array of tracking reflectors ( heliostats ) to concentrate light at a central receiver atop a tower. Power towers can achieve higher efficiency than linear tracking CSP schemes and better energy storage capability than dish stirling technologies. [13] The PS10 Solar Power Plant and PS20 solar power plant are examples of this technology.

Hybrid systems

A hybrid system combines (C) PV and CSP with one another or with other forms of diesel generation, wind and biogas . The combined form of generation can be used to reduce the energy consumption of natural resources. Hybrid systems are often found on islands.
CPV / CSP system
A novel solar CPV / CSP hybrid system has been proposed, combining concentrator photovoltaics with the non-PV technology of concentrated solar power, or also known as concentrated solar thermal. [18]
ISCC system
The Hassi R’Mel power station in Algeria, is an example of combining CSP with a gas turbine, where a 25-megawatt CSP- parabolic trough array supplements a much larger 130 MW combined cycle gas turbine plant . Another example is the Yazd power station in Iran.
PVT system
Hybrid PV / T), also known as photovoltaic thermal hybrid solar collectors . Such a system combines a solar (PV) module with a solar thermal collector in a complementary way.
CPVT system
A concentrated photovoltaic thermal hybrid (CPVT) system is similar to a PVT system. It uses concentrated photovoltaics (CPV) instead of conventional technology, and combines it with a solar thermal collector.
PV diesel system
It combines a photovoltaic system with a diesel generator . [19] Combinations with other renewables are possible and include wind turbines . [20]
PV- thermoelectric system
Thermoelectric, or “thermovoltaic” devices convert a temperature difference between dissimilar materials into an electric current. Solar cells use only the high frequency part of the radiation, while the low frequency heat energy is wasted. Several patents about the use of thermoelectric devices in tandem with solar cells have been filed. [21] The idea is to increase the efficiency of the combined solar / thermoelectric system.

Development and deployment

See also: Solar power by solar cells , Solar power by country , and Solar power § Deployment around the world
Deployment of Solar Power
Capacity in MW by Technology
25,000
50,000
75,000
100,000
125,000
150,000
2007
2010
2013

Worldwide deployment of solar power by technology since 2006 [22]Solar PV  CSP – Solar Thermal

Solar Electricity Generation
year Energy ( TWh ) % of Total
2004 2.6 0.01%
2005 3.7 0.02%
2006 5.0 0.03%
2007 6.8 0.03%
2008 11.4 0.06%
2009 19.3 0.10%
2010 31.4 0.15%
2011 60.6 0.27%
2012 96.7 0.43%
2013 134.5 0.58%
2014 185.9 0.79%
2015 253.0 1.05%
Source : BP- Statistical Review of World Energy, 2016 [23] [24] [25]

Early days

The early development of solar technologies starting in the 1860s was driven by an expectation that coal would soon become scarce. Charles Fritts installed the world’s first rooftop photovoltaic solar array, using 1% -efficient selenium cells, a New York City roof in 1884. [26] However, the development of solar technologies is stagnating in the early 20th century. , economy, and utility of coal and petroleum . [27] In 1974 it was estimated that only six private homes in all of North America were fully heated by solar systems. [28] The 1973 oil embargo and 1979 energy crisiscaused by the reorganization of energy policies around the world, and renewed attention to developing solar technologies. [29] [30] Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the United States (SERI, now NREL ), Japan ( NEDO ), and Germany ( Fraunhofer-ISE ). [31] Between 1970 and 1983 installations of photovoltaic systems grew rapidly, but falling in the early 1980s moderated the growth of photovoltaics from 1984 to 1996.

Mid-1990s to early 2010s

In the mid-1990s, the development of both, residential and commercial rooftop solar energy and utility-scale photovoltaic power stations , global warming concerns , and the improving economic position of PV relative to other energy technologies. [32] In the early 2000s, the adoption of feed-in tariffs -a policy mechanism, which gives renewed priority to the grid and a fixed price for the generated electricity-lead to a high level of investment and security. of PV deployments in Europe.

Current status

Further information: Growth of photovoltaics

For Several years, worldwide growth of solar PV Was driven by European deployment , order HAS since-shifted to Asia, Especially China and Japan , and to a growing number of countries and regions all over the world, Including, but not limited to, Australia , Canada , Chile , India , Israel , Mexico , South Africa , South Korea , Thailand , and the United States .

Worldwide growth of photovoltaics HAS Averaged 40% per year from 2000 to 2013 [33] and total installed capacity atteint 303 GW at the end of 2016 with China HAVING the cumulative MOST plants (78 GW) [34] and Honduras HAVING The Highest theoretical percentage of annual electricity usage which could be generated by solar PV (12.5%). [34] [33] The largest manufacturers are located in China. [35] [36]

Concentrated solar power (CSP) also began to grow rapidly, increasing its capacity almost tenfold from 2004 to 2013, from a lower level of solar PV. [37] : 51 As of the end of 2013, cumulative worldwide CSP capacity- atteint 3,425 MW.

Forecasts

In 2010, the International Energy Agency predicted that global solar PV capacity could reach 3,000 GW or 11% of global electricity generation by 2050-enough to generate 4,500 TWh of electricity. [38] Four years later, in 2014, the agency projected that, under its “high renewables” scenario, solar power could supply 27% of global electricity generation by 2050 (16% from PV and 11% from CSP). [2] In 2015, analysts predicted that one million homes in the US will have solar power by the end of 2016. [39]

Photovoltaic power stations

Main article: List of photovoltaic power stations

The Desert Sunlight Solar Farm is a 550 MW power plant in Riverside County, California , that uses thin-film CdTe-modules made by First Solar . [40] As of November 2014, the 550 megawatt Topaz Solar Farm was the largest photovoltaic power plant in the world. This was surpassed by the 579 MW Solar Star complex. The current largest photovoltaic power station in the world is Longyangxia Dam Solar Park, in Gonghe County , Qinghai , China .

World’s largest photovoltaic power stations as of 2015
name Capacity
( MW )
leasing Year Completed
Info
Longyangxia Dam Solar Park 850 Qinghai , China 2013, 2015
Kamuthi Solar Power Project 648 Kamuthi, India 2015 [41]
Solar Star I and II 579 California, USA 2015 [42]
Topaz Solar Farm 550 California, USA 2014
Desert Sunlight Solar Farm 550 California, USA 2015
California Valley Solar Ranch 292 California, USA 2013
Agua Caliente Solar Project 290 Arizona, USA 2014
Mount Signal Solar 266 California, USA 2014 [43]
Antelope Valley Solar Ranch 266 California, USA pending
Charanka Solar Park 224 Gujarat , India 2012
Mesquite Solar project 207 Arizona, USA pending 
(planned 700 MW)
Huanghe Hydropower Golmud Solar Park 200 Qinghai, China 2011
Gonghe Industrial Park Phase I 200 Gonghe County , China 2013 [44]
Imperial Valley Solar Project 200 California, USA 2013
Note : rounded figures. List may change frequently. For more detailed information and up to date information see:
List of world’s largest photovoltaic power stations or corresponding article.

Concentrating solar power stations

Main article: List of Solar Thermal Power Stations

Commercial solar concentrating power (CSP) plants, also called “solar thermal power stations”, were first developed in the 1980s. The 377 MW Ivanpah Solar Power Facility , located in California’s Mojave Desert, is the world’s largest solar thermal power plant project. Other large CSP plants include the Solnova Solar Power Station (150 MW), the Andasol solar power station (150 MW), and the Extresol Solar Power Station (150 MW), all in Spain. The main advantage of CSP is the ability to efficiently add thermal storage, allowing the dispatching of electricity over a 24-hour period. As if on the whole day of the day, and many years ago CSP power plants use 3 to 5 hours of thermal storage. [45]

Largest operational solar thermal power stations
name Capacity
( MW )
leasing Notes
Ivanpah Solar Power Facility 392 Mojave Desert , California , USA Operational since February 2014. Located southwest ofLas Vegas .
Solar Energy Generating Systems 354 Mojave Desert , California , USA Commissioned between 1984 and 1991. Collection of 9 units.
Mojave Solar Project 280 Barstow, California , USA Completed December 2014
Solana Generating Station 280 Gila Bend, Arizona , USA Completed October 2013
Includes a 6h thermal energy storage
Genesis Solar Energy Project 250 Blythe, California , USA Completed April 2014
Solaben Solar Power Station [46] 200 Logrosán , Spain Completed 2012-2013 [47]
Noor I 160 Morocco Completed 2016
Solnova Solar Power Station 150 Seville , Spain Completed in 2010
Andasol solar power station 150 Granada , Spain Completed 2011. Includes a 7.5h thermal energy storage.
Extresol Solar Power Station 150 Torre de Miguel Sesmero , Spain Completed 2010-2012
Extresol 3 includes a 7.5h thermal energy storage
For a more detailed, sourced and complete list, see: List of solar thermal power stations #Operational or corresponding article.

Economics

cost

Adjusting for inflation, it costs $ 96 per watt for a solar module in the mid-1970s. Process improvements and a very large boost in production have been shown to be down to 68 cents per watt in February 2016, according to Bloomberg New Energy Finance. [49] Palo Alto California is a 3.7 cents per kilowatt hour. And in sunny Dubai large-scale solar generated electricity sold in 2016 for just 2.99 cents per kilowatt-hour – “competitive with any form of fossil-based electricity – and cheaper than most.” [50]

Photovoltaic systems use fuel and modules typically last 25 to 40 years. Thus, capital costs make up most of the cost of solar power. In the United States, solar panels are estimated to be 9 percent of the cost of photovoltaic electricity, and 17 percent of the cost of solar thermal electricity. [51] Governments have created various financial incentives to encourage the use of solar power, such as feed-in tariff programs . In addition, Renewable portfolio standards requires a power of attorney to generate certain percentage of renewable energy. In most states, RPS can be achieved by any combination of solar, wind, biomass,landfill gas , ocean, geothermal, municipal solid waste , hydroelectric, hydrogen, fuel cell technologies. [52]

Levelized cost of electricity

The PV industry is beginning to adopt the level of cost of electricity (LCOE) as the unit of cost. The electrical energy generated is sold in units of kilowatt hours (kWh). As a rule of thumb, and depending on the local insolation , 1 watt-peak of installed solar PV capacity is about 1 to 2 kWh of electricity per year. This corresponds to a capacity factor of around 10-20%. The product of the local cost of electricity and the insolation determines the break even point for solar power. The International Conference on Solar Photovoltaic Investments, organized by EPIA , has been estimated to pay off their investors in 8 to 12 years. [53]As a result, since 2006 it has-been economy for investors to install photovoltaics for free in return for a long-term power purchase agreements . Fifty percent of commercial systems in the United States were installed in 2007 and over 90% by 2009. [54]

Shi Zhengrong said, as of 2012, unsubsidized solar power is already competitive with fossil fuels in India, Hawaii, Italy and Spain. He said, “We are at a tipping point, and we are now starting to compete in the world. “Solar power will be able to compete against the power of the average power source in the world by 2015”. [55]

Current installation prices

In ict 2014 edition of the Technology Roadmap: Solar Photovoltaic Energy report, the International Energy Agency (IEA) published prices for residential, commercial and utility-scale PV systems for eight major markets as of 2013 (see table below) . [2] However, DOE’s SunShot Initiative has reported much lower US installation prices. In 2014, prices continued to decline. The SunShot Initiative modeled US system prices from $ 1.80 to $ 3.29 per watt. [56] Other sources identify similar prices ranges from $ 1.70 to $ 3.50 for different market segments in the US, [57]and in the highly penetrated German market, prices for residential and small commercial rooftop systems of up to 100 kW declined to $ 1.36 per watt (€ 1.24 / W) by the end of 2014. [58] In 2015, Deutsche Bank estimated costs for small residential rooftop systems in the US around $ 2.90 per watt. Costs for utility-scale systems in China and India were estimated to be as low as $ 1.00 per watt. [59]

Typical PV system prices in 2013 in selected countries (USD)
USD / W australia china la France germany italy Japan United Kingdom United States
 Residential 1.8 1.5 4.1 2.4 2.8 4.2 2.8 4.9 1
 Commercial 1.7 1.4 2.7 1.8 1.9 3.6 2.4 4.5 1
 Utility-scale 2.0 1.4 2.2 1.4 1.5 2.9 1.9 3.3 1
Source: IEA – Technology Roadmap: Solar Photovoltaic Energy report, September 2014 ‘ [2] : 15
1 U.S figures are lower in DOE’s Photovoltaic System Pricing Trends [56]

Grid parity

Main article: Grid parity

Grid parity, the point at qui the cost of photovoltaic electricity is equal to or Cheaper than the price of grid power , is more Easily Achieved in areas with abundant sun and high costs for electricity Such As in California and Japan . [60] In 2008, the levelized cost of electricity for solar PV was $ 0.25 / kWh or less in most of the OECD countries. By late 2011, the fully loaded cost was down to $ 0.15 / kWh for most of the OECD and to reach $ 0.10 / kWh in sunnier regions. These cost levels are driving three emerging trends: vertical integration of the supply chain, origination of power purchase agreements(PPAs) by solar power companies, grid operators and wind turbine manufacturers . [61] dead link ]

Grid parity atteint Was first in Spain in 2013, [62] 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. [63] [ not in quote given ] [64]

In 2007, General Electric’s Chief Engineer predicted grid parity without subsidies in sunny parts of the United States by around 2015; other companies Predicted year Earlier Date: [65] the cost of solar power will be below for more grid parity than half of residential customers and 10% of business customers in the OECD , as long as grid electricity prices dont Decrease through 2010. [ 61]

Productivity by location

See also: Solar irradiance

The productivity of solar power in a region depends on solar irradiance , which varies by day and is influenced by latitude and climate .

The locations with highest annual solar irradiance lie in the arid tropics and subtropics. Deserts lying in low latitudes usually have few clouds, and can receive sunshine for more than ten hours a day. [66] [67] These hot deserts form the Global Sun Belt circling the world. This belt consists of extensive swathes of land in Northern Africa , Southern Africa , Southwest Asia , Middle East , and Australia , as well as the much smaller deserts of North and South America . [68] Africa’s eastern Sahara Desert , also known as the Libyan Desert, has been observed in the sunniest place on Earth according to NASA. [69] [70]

Different measurements of solar irradiance (direct normal irradiance, global horizontal irradiance) are mapped below:

Self consumption

In cases of self-consumption of the solar energy, the payback time is calculated based on how much electricity is not purchased from the grid. For example, in Germany, with electricity prices of 0.25 € / kWh and insolation of 900 kWh / kW, one kWp will save € 225 per year, and with an installation cost of 1700 € / KWp the system cost will be returned in less than seven years. [71]However, in many cases, the patterns of generation and consumption do not coincide, and some of the energy is fed back into the grid. The electricity is sold, and at other times when energy is taken from the grid, electricity is bought. The relative costs and prices obtained affect the economics. In many markets, the price paid for electricity is significantly lower than the price of electricity, which incentivizes self consumption. [72] Moreover, separate self-consumption incentives have been used in Germany and Italy. [72] Grid interaction regulation has also included limitations of grid feed-in in some regions in Germany. [72] [73]By increasing self consumption, the grid feed-in can be limited without curtailment, which wastes electricity. [74]

A good match between generation and consumption is key for high self consumption, and should be considered when deciding where to install solar power and how to size the installation. The match can be improved with batteries or controllable electricity consumption. [74] However, batteries are expensive and profitable. [75] Hot water storage tanks with electric heating and heat pumps can provide low-cost storage for self-consumption of solar power. [74]Shiftable loads, such as dishwashers, tumble dryers and washing machines, may provide controllable consumption only for limited users. [74]

Energy pricing and incentives

Main article: PV financial incentives

The political purpose of incentive policies is to facilitate the development of small and medium-sized enterprises. parity. The policies are implemented to promote national energy independence and high tech job creation and reduction of CO 2 emissions. Three incentive mechanisms are often used in the context of a renewable energy savings scheme, the Solar Power Renewable Energy Certificates (SRECs) )

Rebates

With investment subsidies, the financial burden falls on the taxpayer, while with feed-in tariffs is distributed across the utilities’ customer bases. While the investment subsidy may be simpler to administer, the main argument in favor of feed-in tariffs is the encouragement of quality. Investment grants are paid out as a function of the nameplate capacity of the system and are independent of their actual power yield over time, thus rewarding the overstatement of power and tolerating poor durability and maintenance. Some electric companies offer rebates to Their customers, Such As Austin Energy in Texas , qui offers $ 2.50 / watt installed up to $ 15,000. [76]

Net metering

In net energy metering the price of the electricity Produced est la même as the price Supplied to the consumer, and the consumer is billed on the différence entre generation and consumption. Net metering can usually be done with no changes to standard electricity meters , qui Accurately measure power in Both directions and automatically carry the difference, and Because It Allows homeowners and businesses to generate electricity at a different time from consumption, Effectively using the grid as a giant storage battery. With net metering, deficits are billed each month while surpluses are rolled over the following month. Best practices call for perpetual roll over of kWh credits. [77]Excess credits on termination of service are either lost, or paid for, or may be excessively high. In New Jersey, annual rates are paid as high as a customer’s service. [78]

Feed-in tariffs (FIT)

With feed-in tariffs , the financial burden falls upon the consumer. They reward the number of kilowatt-hours produced over a long period of time, but the rate is set by the authorities, it can result in perceived overpayment. The price paid per kilowatt hour under a feed-in tariff exceeds the price of grid electricity. Net metering refers to the case where the price paid by the utility is the same as the price charged.

The complexity of approvals in California, Spain and Italy has prevented comparable growth in Germany even though the return on investment is better. citation needed ] In some countries, additional incentives are offered for BIPVcompared to stand alone PV.

  • France + EUR 0.16 / kWh (compared to semi-integrated) gold + EUR 0.27 / kWh (compared to stand alone)
  • Italy + EUR 0.04-0.09 kWh
  • Germany + EUR 0.05 / kWh (facades only)

Solar Renewable Energy Credits (SRECs)

Alternatively, SRECsallow for a market price mechanism of the solar generated electricity subsity. In this mechanism, a renewable energy production or consumption target is set, and the utility (more technically the Load Serving Entity) is obliged to purchase renewable energy or face a fine (Alternative Compliance Payment or ACP). The producer is credited for an SREC for every 1,000 kWh of electricity produced. If the utility buys this SREC and withdraws it, they avoid paying the ACP. In principle, this system offers the best renewable energy, since they are eligible and can be installed in the most economic locations. Uncertainties about the future value of SRECs and SRECs to pre-sell and hedge their credits.

Financial incentives for photovoltaics differ across countries, including Australia , China , [79] Germany , [80] Israel , [81] Japan , and the United States and even across states within the US.

The Japanese government through ict Ministry of International Trade and Industry ran a successful program of subsidies from 1994 to 2003. By the end of 2004, Japan led the world 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 the German Renewable Energy Act , which resulted in explosive growth of PV facilities in Germany. At the outset the FIT was over 3x the retail price or 8x the industrial price. The principle behind the German system is a 20-year flat rate contract. The value of new contracts is set to decrease each year, in order to encourage the industry to lower costs to the end users. The program has been more successful than expected with over 1GW installed in 2006, and political pressure is mounting to decrease the future burden on consumers.

Subsequently, Spain , Italy , Greece -that enjoyed an early success with domestic solar-thermal facilities for hot water needs and Franceintroduced feed-in tariffs. None has decreased the FIT program in new contracts though, making the German incentive relatively less and less attractive compared to other countries. The French and Greek FIT offers a high premium (EUR 0.55 / kWh) for building integrated systems. California, Greece, France and Italy have 30-50% more insolation than Germany making them financially more attractive. The Greek domestic “solar roof” program (adopted in June 2009 for installations up to 10 kW) has a higher rate of return on the price of 10-15%.

In 2006 California approved the ‘ California Solar Initiative ‘, offering a choice of investment grants or FIT for small and medium systems and FIT for large systems. The small-system FIT of $ 0.39 per kWh (expires less than EU countries) expires in just 5 years, and the alternate “EPBB” residential investment incentive is modest, averaging perhaps 20% of cost. All California incentives are scheduled to decrease in the future depending on the amount of PV capacity installed.

At the end of 2006, the Ontario Power Authority (OPA, Canada) began its Standard Offer Program, a precursor to the Green Energy Act , and the first in North America for distributed renewable projects of less than 10 MW. The feed-in price guaranteed a fixed price of $ 0.42 CDN per kWh over a period of twenty years. Unlike net metering, all the electricity has been sold to the OPA at the given rate.

Grid integration

Construction of the Salt Tanks which provides efficient thermal energy storage [83] so that it can be provided after the sun goes down. [84] The 280 MW Solana Generating Station is designed to provide six hours of energy storage. This allows the plant to generate about 38 percent of its capacity over the course of a year. [85]

The overwhelming majority of electricity production is usually used today. HOWEVER Both solar power and wind power are variable renewable energy , meaning That All available output must be taken whenever will it est disponible by moving through transmission lines to Where It Can Be used now . Since solar energy is not available at night, Storing ict energy is Potentially significant outcome PARTICULARLY year in off-grid and for future 100% renewable energy scenarios to-have continuous electricity availability. [86]

Solar electricity is inherently variable and predictable by time of day, location, and seasons. In addition, solar is intermittent due to day / night cycles and unpredictable weather. How much of a special challenge? In a summer peak utility, solar is well matched to daytime cooling demand. In winter peak utilities, solar displaces other forms of generation, reducing their capacity factors .

In an electricity system without grid energy storage , generation from Stored fuels (coal, biomass, natural gas, nuclear) must be go up and down in reaction to the rise and fall of solar electricity (see load Following power plant ). While hydroelectric and natural gas plants can quickly follow solar intermittent to the weather, coal, biomass and nuclear plants usually take a toll. Depending On Circumstances local, beyond about 20-40% of total generation, grid-connected intermittent sources like solar tends to require investment In Some combination of grid interconnections , energy storage golddemand side management . Integrating large amounts of solar power with existing generation equipment. For example, in Germany, California, and Hawaii, the power of solar power has been raised . [87] [88]

Conventional hydroelectricity works very well in conjunction with solar power, water can be held back or released from a reservoir behind a dam as required. Where a suitable river is not available, pumped-storage hydroelectricity uses solar power to pump water to a high reservoir on sunny days then the energy is recovered by a hydroelectric plant to a low reservoir where the cycle can begin again. [89] However, this cycle can be expected to increase the costs of energy efficiency.

Concentrated solar power plants may use thermal storage , such as high temperature molten salts. These are an effective storage medium because they are low-cost, have a high specific heat capacity, and can deliver heat at temperatures compatible with conventional power systems. This method of energy storage is used, for example, by the Solar Two power station, allowing it to store 1.44 TJ in its 68 m³ storage tank, sufficient to provide full output for close to 39 hours, with an efficiency of about 99%. [90]

In stand alone PV systems batteries are traditionally used to store excess electricity. With grid-connected photovoltaic power system , excess electricity can be felt to the electrical grid . Net metering and feed-in tariff programs give these systems a credit for electricity they produce. This credit can not be effectively met with the grid, but with the grid instead of storing excess electricity. Credits are normally rolled over by monthly surplus. [91]When wind and solar are a small fraction of the grid power, other generation techniques can adjust their output appropriately, but these forms of variable power grow. Prices are rapidly declining, the most expensive batteries are used. Batteries used for grid-storage stabilizes the electrical grid by leveling out peaks usually for several minutes, and in rare cases for hours. In the future, they can charge a large share of the electricity grid, and they can charge them for electricity generation.

Although not permitted under the US National Electric Code, it is technically possible to have a ” plug and play ” PV microinverter. A recent review article found that careful design system would enable such systems, but not all safety requirements. [92] There are Several companies selling plug and play solar systems available on the web, there is a purpose That concern if people install Their Own it will Reduce The Enormous employment advantage over solar HAS fossil fuels . [93]

Common battery technologies used in today’s PV systems include, the lead-acid battery-regulated battery – a modified version of the lead-acid battery , nickel-cadmium and lithium-ionbatteries. Lead-acid batteries are currently the predominant technology used in small-scale, residential PV systems, due to their high reliability, low self-discharge and maintenance costs, despite shorter lifetime and lower energy density. HOWEVER, lithium-ion batteries-have the potential to replace lead-acid batteries in the near future, As They are intensively being white Developed and lower prices are expected due to economies of scale provided by wide production facilities Such As theGigafactory 1 . In addition, the lithium-ion batteries of plug-in electric cars May serve as a future storage devices in a vehicle-to-grid system. Since most vehicles are parked at an average of 95 percent of the time, their batteries could be used to generate electricity. Other rechargeable batteries used for distributed PV systems include, sodium-sulfur and vanadium redox batteries, two prominent types of a molten salt and a flow battery, respectively. [94] [95] [96]

The combination of wind and solar PV has the advantage that the two sources are at different times of the day and year. The power generation of such solar hybrid power systems is therefore more constant and fluctuates than each of the two component subsystems. [20] Solar power is seasonal, particularly in northern / southern climates, from the equator, suggesting a need for a long-term storage of hydroelectricity. [97] The Institute for Solar Energy Supply Technology of the University of Kassel pilot-tested a combined power plant linking solar, wind, biogas andhydrostorage to provide load-following power from renewable sources. [98]

Research is also undertaken in this field of artificial photosynthesis . It involves the use of nanotechnology to store solar electromagnetic energy in chemical bonds, by splitting water to produce hydrogen fuel or carbon dioxide to make biopolymers such as methanol . Many large national and regional research projects are being developed, and are currently being developed. [99]Senior researchers in the field of public policy for a Global Project on Artificial Photosynthesis to address critical energy security and environmental sustainability issues. [100]

Environmental impacts

Part of the Senftenberg Solarpark , a solar photovoltaic power plant located on the open-pit mining areas close to the city of Senftenberg , in Eastern Germany. The 78 MW Phase 1 of the plant was completed within three months.

Unlike fossil fuel based technologies, solar power does not lead to any harmful emissions during operation, but the production of the panels leads to some amount of pollution.

Greenhouse gases

The life-cycle greenhouse-gas emissions of solar energy are in the range of 22 to 46 gram (g) per kilowatt-hour (kWh). With this potential being decreased to 15 g / kWh in the future. [101]For comparison (of weighted averages), a combined cycle gas-fired power plant emits some 400-599 g / kWh, [102] an oil-fired power plant 893 g / kWh, [102] has coal-fired power plant 915-994 g / kWh [103] or with carbon capture and storage some 200 g / kWh, and a geothermal high-temp. power plant 91-122 g / kWh. [102]The life cycle emission intensity of hydro , wind and nuclear power are as follows, and discussed in the article Life-cycle greenhouse-gas emissions of energy sources . Similar to all energy sources were their total life cycle emissions primarily in the construction and transportation phases, the switch to low carbon powerin the manufacturing and transportation of solar devices. BP Solar owns two factories built by Solarex (one in Maryland, the other in Virginia) in which all of the energy used to manufacture solar panels is produced by solar panels. A 1-kilowatt system eliminates the burning of approximately 170 pounds of coal, 300 pounds of carbon dioxide from being released into the atmosphere, and saves up to 105 gallons of water consumption. [104]

The US National Renewable Energy Laboratory ( NREL ), in harmonizing the disparate estimates of life-cycle GHG emissions for solar PV, is the most critical parameter of the solar insolation of the site: GHG emissions factors for solar PV are inversely proportional to insolation . [105] For a site with insolation of 1700 kWh / m2 / year, typical of southern Europe, estimated emissions of 45 gCO 2 e / kWh. Using the same assumptions, at Phoenix, USA, with insolation of 2400 kWh / m2 / year, the GHG emissions factor would be reduced to 32 g of CO 2 e / kWh. [106]

The New Zealand Parliamentary Commissioner for the Environment found that the solar PV would have little impact on the country’s greenhouse gas emissions. The country already generated 80 percent of its electricity from renewable sources of energy (formerly hydroelectricity and geothermal) and national electricity usage peaks -fueled power plants. [107]

Energy payback

The energy payback time (EPBT) of a power generating system is the time required to generate the energy consumption of the system. Due to improving production technologies the payback time has been decreasing constantly since the introduction of PV systems in the energy market. [108] In 2000 the energy payback time of PV systems was estimated to be 8 to 11 years [109] and in this year it was estimated to be 1.5 to 3.5 years for silicon silicon PV systems [101] and 1-1.5 years for thin film technologies (S. Europe). [101]These figures fell to 0.75-3.5 years in 2013, with an average of about 2 years for crystalline silicon PV and CIS systems. [110]

Another economic measure, étroitement related to the energy payback time, is the energy returned on energy Invested (EROEI) or energy return on investment (EROI), [111] qui is the ratio of electricity generated divided by the energy required to build and Maintain the equipment. (This is not the same as the economic return on investment (ROI), which varies according to local energy prices, subsidies and metering techniques.) With expected lifetimes of 30 years, [112] the EROEI of PV systems are in the range of 10 to 30, thereby generating enough energy on their reproductive life (6-31 reproductions)balance of system (BOS), and the geographic location of the system. [113]

Other issues

One issue that has been raised is the use of cadmium (Cd), a toxic heavy metal that has the tendency to accumulate in ecological food chains . It is used as a semiconductor component in CdS cells and as a buffer for some CIGS cells in the form of CdS . [114] The amount of cadmium used in thin-film PV modules is relatively small (5-10 g / m²) and with proper recycling and emission control techniques in place the cadmium emissions from module production can be almost zero. Current PV technologies lead to cadmium emissions of 0.3-0.9 microgram/ kWh over the whole life cycle. [101] Most of These broadcasts Arise through the use of coal power for the manufacturing of the modules, and coal and lignite combustion leads to much Higher Emissions of cadmium. Life-cycle cadmium emissions from coal is 3.1 microgram / kWh, lignite 6.2, and natural gas 0.2 microgram / kWh.

In a life-cycle analysis it has been noted that electricity produced by photovoltaic panels was used instead of the modules instead of electricity from combustion coal, cadmium emissions from coal power usage in the manufacturing process could be entirely eliminated. [115]

In the case of crystalline silicon modules, the solder material, contains about 36 percent of lead (Pb). Moreover, the paste used for screen printing contains a trace of Pb and sometimes Cd as well. It is estimated that about 1,000 metric tons of Pb have been used for 100 gigawatts of c-Si solar modules. However, there is no fundamental need for lead in the solder alloy. [114]

Some media sources have reported that concentrated solar power plants have injured or killed large numbers of birds due to intense heat from the concentrated sunrays. [116] [117] This adverse effect does not apply to PV solar power plants, and some of the claims have been overstated or exaggerated. [118]

A 2014-published life-cycle analysis of land use for various sources of electricity that the wide-scale implementation of solar and wind-downs reduce pollution-related environmental impacts. The study found that the land-use footprint, given in square meter-years per megawatt-hour (m 2 y / MWh), was lowest for wind, natural gas and rooftop PV, with 0.26, 0.49 and 0.59, respectively, and followed by utility-scale solar PV with 7.9. For CSP, the footprint was 9 and 14, using parabolic troughs and solar towers, respectively. The largest footprint had coal-fired power plants with 18 m 2 a / MWh. [119]

Emerging technologies

Concentrator photovoltaics

CPV modules on dual axis solar trackers in Golmud, China
Concentrator photovoltaics (CPV) systems employs photovoltaic surfaces for the purpose of electrical power production . Contrary to conventional photovoltaic systems, it uses lensesand curved mirrors to focus sunlight onto small, highly efficient, multi-junction solar cells . Solar concentrators of all types can be used, and these are often mounted on a solar tracker in order to keep track of the sky. [120] Luminescent solar concentrators(when combined with PV-solar cell) can also be regarded as a CPV system. Concentrated photovoltaics can be used to improve the efficiency of PV-solar panels drastically. [121]
In addition, most solar panels on spacecraft are also made of high efficient multi-junction photovoltaic cells to derive electricity from sunlight when operating in the Solar System .

Floatovoltaics

Floatovoltaics are an emerging form of PV systems that float on the surface of irrigation canals, water reservoirs, quarry lakes, and tailing ponds. Several systems exist in France, India, Japan, Korea, the United Kingdom and the United States. [122] [123] [124] [125] These systems reduce the need for valuable land, save water that would otherwise be lost through evaporation, and show a higher efficiency of solar energy conversion , cooler temperature than they would be on land. [126] Although not floating, other dual-use facilities with solar power include fisheries . [127]

Productivity by location

See also: Solar irradiance

The productivity of solar power in a region depends on solar irradiance , which varies by day and is influenced by latitude and climate .

The locations with highest annual solar irradiance lie in the arid tropics and subtropics. Deserts lying in low latitudes usually have few clouds, and can receive sunshine for more than ten hours a day. [66] [67] These hot deserts form the Global Sun Belt circling the world. This belt consists of extensive swathes of land in Northern Africa , Southern Africa , Southwest Asia , Middle East , and Australia , as well as the much smaller deserts of North and South America . [68] Africa’s eastern Sahara Desert , also known as the Libyan Desert, has been observed in the sunniest place on Earth according to NASA. [69] [70]

Different measurements of solar irradiance (direct normal irradiance, global horizontal irradiance) are mapped below:

Self consumption

In cases of self-consumption of the solar energy, the payback time is calculated based on how much electricity is not purchased from the grid. For example, in Germany, with electricity prices of 0.25 € / kWh and insolation of 900 kWh / kW, one kWp will save € 225 per year, and with an installation cost of 1700 € / KWp the system cost will be returned in less than seven years. [71]However, in many cases, the patterns of generation and consumption do not coincide, and some of the energy is fed back into the grid. The electricity is sold, and at other times when energy is taken from the grid, electricity is bought. The relative costs and prices obtained affect the economics. In many markets, the price paid for electricity is significantly lower than the price of electricity, which incentivizes self consumption. [72] Moreover, separate self-consumption incentives have been used in Germany and Italy. [72] Grid interaction regulation has also included limitations of grid feed-in in some regions in Germany. [72] [73]By increasing self consumption, the grid feed-in can be limited without curtailment, which wastes electricity. [74]

A good match between generation and consumption is key for high self consumption, and should be considered when deciding where to install solar power and how to size the installation. The match can be improved with batteries or controllable electricity consumption. [74] However, batteries are expensive and profitable. [75] Hot water storage tanks with electric heating and heat pumps can provide low-cost storage for self-consumption of solar power. [74]Shiftable loads, such as dishwashers, tumble dryers and washing machines, may provide controllable consumption only for limited users. [74]

Energy pricing and incentives

Main article: PV financial incentives

The political purpose of incentive policies is to facilitate the development of small and medium-sized enterprises. parity. The policies are implemented to promote national energy independence and high tech job creation and reduction of CO 2 emissions. Three incentive mechanisms are often used in the context of a renewable energy savings scheme, the Solar Power Renewable Energy Certificates (SRECs) )

Rebates

With investment subsidies, the financial burden falls on the taxpayer, while with feed-in tariffs is distributed across the utilities’ customer bases. While the investment subsidy may be simpler to administer, the main argument in favor of feed-in tariffs is the encouragement of quality. Investment grants are paid out as a function of the nameplate capacity of the system and are independent of their actual power yield over time, thus rewarding the overstatement of power and tolerating poor durability and maintenance. Some electric companies offer rebates to Their customers, Such As Austin Energy in Texas , qui offers $ 2.50 / watt installed up to $ 15,000. [76]

Net metering

In net energy metering the price of the electricity Produced est la même as the price Supplied to the consumer, and the consumer is billed on the différence entre generation and consumption. Net metering can usually be done with no changes to standard electricity meters , qui Accurately measure power in Both directions and automatically carry the difference, and Because It Allows homeowners and businesses to generate electricity at a different time from consumption, Effectively using the grid as a giant storage battery. With net metering, deficits are billed each month while surpluses are rolled over the following month. Best practices call for perpetual roll over of kWh credits. [77]Excess credits on termination of service are either lost, or paid for, or may be excessively high. In New Jersey, annual rates are paid as high as a customer’s service. [78]

Feed-in tariffs (FIT)

With feed-in tariffs , the financial burden falls upon the consumer. They reward the number of kilowatt-hours produced over a long period of time, but the rate is set by the authorities, it can result in perceived overpayment. The price paid per kilowatt hour under a feed-in tariff exceeds the price of grid electricity. Net metering refers to the case where the price paid by the utility is the same as the price charged.

The complexity of approvals in California, Spain and Italy has prevented comparable growth in Germany even though the return on investment is better. citation needed ] In some countries, additional incentives are offered for BIPVcompared to stand alone PV.

  • France + EUR 0.16 / kWh (compared to semi-integrated) gold + EUR 0.27 / kWh (compared to stand alone)
  • Italy + EUR 0.04-0.09 kWh
  • Germany + EUR 0.05 / kWh (facades only)

Solar Renewable Energy Credits (SRECs)

Alternatively, SRECsallow for a market price mechanism of the solar generated electricity subsity. In this mechanism, a renewable energy production or consumption target is set, and the utility (more technically the Load Serving Entity) is obliged to purchase renewable energy or face a fine (Alternative Compliance Payment or ACP). The producer is credited for an SREC for every 1,000 kWh of electricity produced. If the utility buys this SREC and withdraws it, they avoid paying the ACP. In principle, this system offers the best renewable energy, since they are eligible and can be installed in the most economic locations. Uncertainties about the future value of SRECs and SRECs to pre-sell and hedge their credits.

Financial incentives for photovoltaics differ across countries, including Australia , China , [79] Germany , [80] Israel , [81] Japan , and the United States and even across states within the US.

The Japanese government through ict Ministry of International Trade and Industry ran a successful program of subsidies from 1994 to 2003. By the end of 2004, Japan led the world 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 the German Renewable Energy Act , which resulted in explosive growth of PV facilities in Germany. At the outset the FIT was over 3x the retail price or 8x the industrial price. The principle behind the German system is a 20-year flat rate contract. The value of new contracts is set to decrease each year, in order to encourage the industry to lower costs to the end users. The program has been more successful than expected with over 1GW installed in 2006, and political pressure is mounting to decrease the future burden on consumers.

Subsequently, Spain , Italy , Greece -that enjoyed an early success with domestic solar-thermal facilities for hot water needs and Franceintroduced feed-in tariffs. None has decreased the FIT program in new contracts though, making the German incentive relatively less and less attractive compared to other countries. The French and Greek FIT offers a high premium (EUR 0.55 / kWh) for building integrated systems. California, Greece, France and Italy have 30-50% more insolation than Germany making them financially more attractive. The Greek domestic “solar roof” program (adopted in June 2009 for installations up to 10 kW) has a higher rate of return on the price of 10-15%.

In 2006 California approved the ‘ California Solar Initiative ‘, offering a choice of investment grants or FIT for small and medium systems and FIT for large systems. The small-system FIT of $ 0.39 per kWh (expires less than EU countries) expires in just 5 years, and the alternate “EPBB” residential investment incentive is modest, averaging perhaps 20% of cost. All California incentives are scheduled to decrease in the future depending on the amount of PV capacity installed.

At the end of 2006, the Ontario Power Authority (OPA, Canada) began its Standard Offer Program, a precursor to the Green Energy Act , and the first in North America for distributed renewable projects of less than 10 MW. The feed-in price guaranteed a fixed price of $ 0.42 CDN per kWh over a period of twenty years. Unlike net metering, all the electricity has been sold to the OPA at the given rate.

Grid integration

Construction of the Salt Tanks which provides efficient thermal energy storage [83] so that it can be provided after the sun goes down. [84] The 280 MW Solana Generating Station is designed to provide six hours of energy storage. This allows the plant to generate about 38 percent of its capacity over the course of a year. [85]

The overwhelming majority of electricity production is usually used today. HOWEVER Both solar power and wind power are variable renewable energy , meaning That All available output must be taken whenever will it est disponible by moving through transmission lines to Where It Can Be used now . Since solar energy is not available at night, Storing ict energy is Potentially significant outcome PARTICULARLY year in off-grid and for future 100% renewable energy scenarios to-have continuous electricity availability. [86]

Solar electricity is inherently variable and predictable by time of day, location, and seasons. In addition, solar is intermittent due to day / night cycles and unpredictable weather. How much of a special challenge? In a summer peak utility, solar is well matched to daytime cooling demand. In winter peak utilities, solar displaces other forms of generation, reducing their capacity factors .

In an electricity system without grid energy storage , generation from Stored fuels (coal, biomass, natural gas, nuclear) must be go up and down in reaction to the rise and fall of solar electricity (see load Following power plant ). While hydroelectric and natural gas plants can quickly follow solar intermittent to the weather, coal, biomass and nuclear plants usually take a toll. Depending On Circumstances local, beyond about 20-40% of total generation, grid-connected intermittent sources like solar tends to require investment In Some combination of grid interconnections , energy storage golddemand side management . Integrating large amounts of solar power with existing generation equipment. For example, in Germany, California, and Hawaii, the power of solar power has been raised . [87] [88]

Conventional hydroelectricity works very well in conjunction with solar power, water can be held back or released from a reservoir behind a dam as required. Where a suitable river is not available, pumped-storage hydroelectricity uses solar power to pump water to a high reservoir on sunny days then the energy is recovered by a hydroelectric plant to a low reservoir where the cycle can begin again. [89] However, this cycle can be expected to increase the costs of energy efficiency.

Concentrated solar power plants may use thermal storage , such as high temperature molten salts. These are an effective storage medium because they are low-cost, have a high specific heat capacity, and can deliver heat at temperatures compatible with conventional power systems. This method of energy storage is used, for example, by the Solar Two power station, allowing it to store 1.44 TJ in its 68 m³ storage tank, sufficient to provide full output for close to 39 hours, with an efficiency of about 99%. [90]

In stand alone PV systems batteries are traditionally used to store excess electricity. With grid-connected photovoltaic power system , excess electricity can be felt to the electrical grid . Net metering and feed-in tariff programs give these systems a credit for electricity they produce. This credit can not be effectively met with the grid, but with the grid instead of storing excess electricity. Credits are normally rolled over by monthly surplus. [91]When wind and solar are a small fraction of the grid power, other generation techniques can adjust their output appropriately, but these forms of variable power grow. Prices are rapidly declining, the most expensive batteries are used. Batteries used for grid-storage stabilizes the electrical grid by leveling out peaks usually for several minutes, and in rare cases for hours. In the future, they can charge a large share of the electricity grid, and they can charge them for electricity generation.

Although not permitted under the US National Electric Code, it is technically possible to have a ” plug and play ” PV microinverter. A recent review article found that careful design system would enable such systems, but not all safety requirements. [92] There are Several companies selling plug and play solar systems available on the web, there is a purpose That concern if people install Their Own it will Reduce The Enormous employment advantage over solar HAS fossil fuels . [93]

Common battery technologies used in today’s PV systems include, the lead-acid battery-regulated battery – a modified version of the lead-acid battery , nickel-cadmium and lithium-ionbatteries. Lead-acid batteries are currently the predominant technology used in small-scale, residential PV systems, due to their high reliability, low self-discharge and maintenance costs, despite shorter lifetime and lower energy density. HOWEVER, lithium-ion batteries-have the potential to replace lead-acid batteries in the near future, As They are intensively being white Developed and lower prices are expected due to economies of scale provided by wide production facilities Such As theGigafactory 1 . In addition, the lithium-ion batteries of plug-in electric cars May serve as a future storage devices in a vehicle-to-grid system. Since most vehicles are parked at an average of 95 percent of the time, their batteries could be used to generate electricity. Other rechargeable batteries used for distributed PV systems include, sodium-sulfur and vanadium redox batteries, two prominent types of a molten salt and a flow battery, respectively. [94] [95] [96]

The combination of wind and solar PV has the advantage that the two sources are at different times of the day and year. The power generation of such solar hybrid power systems is therefore more constant and fluctuates than each of the two component subsystems. [20] Solar power is seasonal, particularly in northern / southern climates, from the equator, suggesting a need for a long-term storage of hydroelectricity. [97] The Institute for Solar Energy Supply Technology of the University of Kassel pilot-tested a combined power plant linking solar, wind, biogas andhydrostorage to provide load-following power from renewable sources. [98]

Research is also undertaken in this field of artificial photosynthesis . It involves the use of nanotechnology to store solar electromagnetic energy in chemical bonds, by splitting water to produce hydrogen fuel or carbon dioxide to make biopolymers such as methanol . Many large national and regional research projects are being developed, and are currently being developed. [99]Senior researchers in the field of public policy for a Global Project on Artificial Photosynthesis to address critical energy security and environmental sustainability issues. [100]

Environmental impacts

Part of the Senftenberg Solarpark , a solar photovoltaic power plant located on the open-pit mining areas close to the city of Senftenberg , in Eastern Germany. The 78 MW Phase 1 of the plant was completed within three months.

Unlike fossil fuel based technologies, solar power does not lead to any harmful emissions during operation, but the production of the panels leads to some amount of pollution.

Greenhouse gases

The life-cycle greenhouse-gas emissions of solar energy are in the range of 22 to 46 gram (g) per kilowatt-hour (kWh). With this potential being decreased to 15 g / kWh in the future. [101]For comparison (of weighted averages), a combined cycle gas-fired power plant emits some 400-599 g / kWh, [102] an oil-fired power plant 893 g / kWh, [102] has coal-fired power plant 915-994 g / kWh [103] or with carbon capture and storage some 200 g / kWh, and a geothermal high-temp. power plant 91-122 g / kWh. [102]The life cycle emission intensity of hydro , wind and nuclear power are as follows, and discussed in the article Life-cycle greenhouse-gas emissions of energy sources . Similar to all energy sources were their total life cycle emissions primarily in the construction and transportation phases, the switch to low carbon powerin the manufacturing and transportation of solar devices. BP Solar owns two factories built by Solarex (one in Maryland, the other in Virginia) in which all of the energy used to manufacture solar panels is produced by solar panels. A 1-kilowatt system eliminates the burning of approximately 170 pounds of coal, 300 pounds of carbon dioxide from being released into the atmosphere, and saves up to 105 gallons of water consumption. [104]

The US National Renewable Energy Laboratory ( NREL ), in harmonizing the disparate estimates of life-cycle GHG emissions for solar PV, is the most critical parameter of the solar insolation of the site: GHG emissions factors for solar PV are inversely proportional to insolation . [105] For a site with insolation of 1700 kWh / m2 / year, typical of southern Europe, estimated emissions of 45 gCO 2 e / kWh. Using the same assumptions, at Phoenix, USA, with insolation of 2400 kWh / m2 / year, the GHG emissions factor would be reduced to 32 g of CO 2 e / kWh. [106]

The New Zealand Parliamentary Commissioner for the Environment found that the solar PV would have little impact on the country’s greenhouse gas emissions. The country already generated 80 percent of its electricity from renewable sources of energy (formerly hydroelectricity and geothermal) and national electricity usage peaks -fueled power plants. [107]

Energy payback

The energy payback time (EPBT) of a power generating system is the time required to generate the energy consumption of the system. Due to improving production technologies the payback time has been decreasing constantly since the introduction of PV systems in the energy market. [108] In 2000 the energy payback time of PV systems was estimated to be 8 to 11 years [109] and in this year it was estimated to be 1.5 to 3.5 years for silicon silicon PV systems [101] and 1-1.5 years for thin film technologies (S. Europe). [101]These figures fell to 0.75-3.5 years in 2013, with an average of about 2 years for crystalline silicon PV and CIS systems. [110]

Another economic measure, étroitement related to the energy payback time, is the energy returned on energy Invested (EROEI) or energy return on investment (EROI), [111] qui is the ratio of electricity generated divided by the energy required to build and Maintain the equipment. (This is not the same as the economic return on investment (ROI), which varies according to local energy prices, subsidies and metering techniques.) With expected lifetimes of 30 years, [112] the EROEI of PV systems are in the range of 10 to 30, thereby generating enough energy on their reproductive life (6-31 reproductions)balance of system (BOS), and the geographic location of the system. [113]

Other issues

One issue that has been raised is the use of cadmium (Cd), a toxic heavy metal that has the tendency to accumulate in ecological food chains . It is used as a semiconductor component in CdS cells and as a buffer for some CIGS cells in the form of CdS . [114] The amount of cadmium used in thin-film PV modules is relatively small (5-10 g / m²) and with proper recycling and emission control techniques in place the cadmium emissions from module production can be almost zero. Current PV technologies lead to cadmium emissions of 0.3-0.9 microgram/ kWh over the whole life cycle. [101] Most of These broadcasts Arise through the use of coal power for the manufacturing of the modules, and coal and lignite combustion leads to much Higher Emissions of cadmium. Life-cycle cadmium emissions from coal is 3.1 microgram / kWh, lignite 6.2, and natural gas 0.2 microgram / kWh.

In a life-cycle analysis it has been noted that electricity produced by photovoltaic panels was used instead of the modules instead of electricity from combustion coal, cadmium emissions from coal power usage in the manufacturing process could be entirely eliminated. [115]

In the case of crystalline silicon modules, the solder material, contains about 36 percent of lead (Pb). Moreover, the paste used for screen printing contains a trace of Pb and sometimes Cd as well. It is estimated that about 1,000 metric tons of Pb have been used for 100 gigawatts of c-Si solar modules. However, there is no fundamental need for lead in the solder alloy. [114]

Some media sources have reported that concentrated solar power plants have injured or killed large numbers of birds due to intense heat from the concentrated sunrays. [116] [117] This adverse effect does not apply to PV solar power plants, and some of the claims have been overstated or exaggerated. [118]

A 2014-published life-cycle analysis of land use for various sources of electricity that the wide-scale implementation of solar and wind-downs reduce pollution-related environmental impacts. The study found that the land-use footprint, given in square meter-years per megawatt-hour (m 2 y / MWh), was lowest for wind, natural gas and rooftop PV, with 0.26, 0.49 and 0.59, respectively, and followed by utility-scale solar PV with 7.9. For CSP, the footprint was 9 and 14, using parabolic troughs and solar towers, respectively. The largest footprint had coal-fired power plants with 18 m 2 a / MWh. [119]

Emerging technologies

Concentrator photovoltaics

CPV modules on dual axis solar trackers in Golmud, China
Concentrator photovoltaics (CPV) systems employs photovoltaic surfaces for the purpose of electrical power production . Contrary to conventional photovoltaic systems, it uses lensesand curved mirrors to focus sunlight onto small, highly efficient, multi-junction solar cells . Solar concentrators of all types can be used, and these are often mounted on a solar tracker in order to keep track of the sky. [120] Luminescent solar concentrators(when combined with PV-solar cell) can also be regarded as a CPV system. Concentrated photovoltaics can be used to improve the efficiency of PV-solar panels drastically. [121]
In addition, most solar panels on spacecraft are also made of high efficient multi-junction photovoltaic cells to derive electricity from sunlight when operating in the Solar System .

Floatovoltaics

Floatovoltaics are an emerging form of PV systems that float on the surface of irrigation canals, water reservoirs, quarry lakes, and tailing ponds. Several systems exist in France, India, Japan, Korea, the United Kingdom and the United States. [122] [123] [124] [125] These systems reduce the need for valuable land, save water that would otherwise be lost through evaporation, and show a higher efficiency of solar energy conversion , cooler temperature than they would be on land. [126] Although not floating, other dual-use facilities with solar power include fisheries . [127]

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