TERM PAPEROF

PHYSICS -102

SOLAR POWER

SUBMITTED TO: SUBMITTED BY: VISHAL THAKUR JASHANDEEP KAUR SECTION-B2001 ROLL NO-A12

REG NO-11002566

SOLAR POWER

Solar power is the generation of electricity from sunlight. This can be direct as with photovoltaic’s (PV), or indirect as with concentrating solar power (CSP), where the

sun's energy is focused to boil water which is then used to provide power. Solar power provided 0.02% of the total world energy consumption in 2008. The largest solar power plants, like the 354 MW SEGS, are concentrating solar thermal plants,

but recently multi-megawatt photovoltaic plants have been built. Completed in 2008, the 46 MW Moura photovoltaic power station in Portugal and the 40 MW

Waldpolenz Solar Park in Germany appear to be characteristic of the trend toward larger photovoltaic power stations. Larger ones are proposed, such as the 100 MW

Fort Peck Solar Farm, the 550 MW Topaz Solar Farm, and the 600 MW Rancho Cielo Solar Farm.

Terrestrial solar power is a predictably intermittent energy source, meaning that whilst solar power is not available at all times, we can predict with a very good degree of accuracy when it will and will not be available. Some technologies, such as solar

thermal concentrators have an element of thermal storage, such as molten salts. These store spare solar energy in the form of heat which can be made available overnight or

during periods that solar power is not available to produce electricity. Orbital solar power collection (as in solar power satellites) avoids this intermittent issue, but

requires satellite launching and beaming of the collected power to receiving antennas on Earth. The increased intensity of sunlight above the atmosphere also increases

generation efficiency.

HISTORY OF SOLAR CELLS

The term "photovoltaic" comes from the Greek meaning "light", and "voltaic", meaning electric, from the name of the Italian physicist Volta, after whom a unit of electro-motive force, the volt, is named. The term "photo-voltaic" has been in use in English since 1849.

The photovoltaic effect was first recognized in 1839 by French physicist A. E. Becquerel. However, it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only around 1% efficient. In 1888 Russian physicist Aleksandr Stoletov built the first photoelectric cell (based on the outer photoelectric effect discovered by Heinrich Hertz earlier in 1887). Albert Einstein explained the photoelectric effect in 1905 for which he received the Nobel prize in Physics in 1921. Russell Ohl patented the modern junction semiconductor solar cell in 1946, which was discovered while working on the series of advances that would lead to the transistor. The photovoltaic cell was developed in 1954 at Bell Laboratories. The highly efficient solar cell was first developed by Daryl Chapin, Calvin Souther Fuller and Gerald Pearson in 1954 using a diffused silicon p-n junction. In the past four decades, remarkable progress has been made, with Megawatt solar power generating plants having now been built.

APPLICATIONS

Solar power is the conversion of sunlight to electricity. Sunlight can be converted directly into electricity using photovoltaics (PV), or indirectly with concentrating

solar power (CSP), which normally focuses the sun's energy to boil water which is then used to provide power, and technologies such as the Stirling engine dishes which use a Stirling cycle engine to power a generator. Photovoltaics were initially used to power small and medium-sized applications, from the calculator powered by a single

solar cell to off-grid homes powered by a photovoltaic array.

The three types of photovoltaic panels are Monocrystalline, Polycrystalline and Amorphous, each has its advantages and disadvantages. The fact with photovoltaics is that it is difficult to create a commercially viable system because of the overall cost of

the system required to generate a useful amount of power.

Solar power plants can face high installation costs, although this has been decreasing due to the learning curve. Developing countries have started to build solar power

plants, replacing other sources of energy generation.

In 2008, Solar power supplied 0.02% of the world's total energy supply. Use has been doubling every two, or fewer, years. If it continued at that rate, solar power would

become the dominant energy source within a few decades.

Since solar radiation is intermittent, solar power generation is combined either with storage or other energy sources to provide continuous power, although for small

distributed producer/consumers, net metering makes this transparent to the consumer. On a larger scale, in Germany, a combined power plant has been demonstrated, using

a mix of wind, biomass, hydro-, and solar power generation, resulting in 100% renewable energy.

THEORY

The solar cell works in three steps:1. Photons in sunlight hit the solar panel and are absorbed by semiconducting

materials, such as silicon.2. Electrons (negatively charged) are knocked loose from their atoms, allowing

them to flow through the material to produce electricity. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction.

3. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity.

WORKING OF SOLAR POWER

CONCENTRATING SOLAR POWER

Solar troughs are the most widely deployed. A legend claims that Archimedes used polished shields to concentrate sunlight on the invading Roman fleet and repel them from Syracuse. Augustin Mouchot used a parabolic trough to produce steam for the

first solar steam engine in 1866.

Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used

as a heat source for a conventional power plant. A wide range of concentrating technologies exists; the most developed are the parabolic trough, the concentrating

linear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun and focus light. In all of these systems a working fluid is

heated by the concentrated sunlight, and is then used for power generation or energy storage.

A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line. The receiver is a tube positioned right above the middle of the parabolic mirror and is filled with a working fluid. The

reflector is made to follow the Sun during the daylight hours by tracking along a single axis. Parabolic trough systems provide the best land-use factor of any solar technology. The SEGS plants in California and Acciona's Nevada Solar One near Boulder City, Nevada are representatives of this technology. The Suntrof-Mulk

parabolic trough, developed by Melvin Prueitt, uses a technique inspired by Archimedes' principle to rotate the mirrors.

Concentrating Linear Fresnel Reflectors are CSP-plants which use many thin mirror strips instead of parabolic mirrors to concentrate sunlight onto two tubes with working

fluid. This has the advantage that flat mirrors can be used which are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of

space, allowing more of the available sunlight to be used. Concentrating linear fresnel reflectors can be used in either large or more compact plants.

A Stirling solar dish, or dish engine system, consists of a stand-alone parabolic reflector that concentrates light onto a receiver positioned at the reflector's focal point.

The reflector tracks the Sun along two axes. Paraboloidal coordinates ("parabolic") dish systems give the highest efficiency among CSP technologies. The 500 m2 ANU "Big Dish" in Canberra, Australia is an example of this technology. The Stirling solar

dish combines a parabolic concentrating dish with a Stirling heat 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. A solar power tower uses an array of tracking reflectors (heliostats) to

concentrate light on a central receiver atop a tower. Power towers are more cost effective, offer higher efficiency and better energy storage capability among CSP

technologies. The Solar Two in Barstow, California and the Planta Solar 10 in Sanlucar la Mayor, Spain are representatives of this technology.

A solar bowl is a spherical dish mirror that is fixed in place. The receiver follows the line focus created by the dish (as opposed to a point focus with tracking parabolic

mirrors).

PHOTOVOLTAICS

A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photoelectric effect. This is based on the discovery by Alexandre-Edmond Becquerel who noticed that some materials release electrons when hit with rays of photons from light, which produces an electrical current. The first solar cell

was constructed by Charles Fritts in the 1880s. Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discovery.

Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954. These early solar cells

cost 286 USD/watt and reached efficiencies of 4.5–6%. As of late 2009, the highest efficiency PV cells were produced commercially by Boeing/SpectroLab at about 41%. Other, similar, multi-layer cells are close. These are very expensive however, and are used only for the most exacting applications. Thin film PV cells have been developed

which are made in bulk and are far less expensive and much less fragile, but are at most around 20% efficient. The most recent development (from Caltech, March 2010) is the experimental demonstration of a new design which is an 85% efficient photon

absorber in plain sunlight and 95% efficient absorber at certain wavelengths. Unfortunately, 100% absorption should not be confused with 100% electrical

efficiency as single junction materials are bound by the so-called Shockley-Queisser limit.

There are many competing technologies, including at least fourteen types of photovoltaic cells, such as thin film, monocrystalline silicon, polycrystalline silicon, and amorphous cells, as well as multiple types of concentrating solar power. It is too

early to know which technology will become dominant.

The earliest significant application of solar cells was as a back-up power source to the Vanguard I satellite in 1958, which allowed it to continue transmitting for over a year

after its chemical battery was exhausted. The successful operation of solar cells on this mission was duplicated in many other Soviet and American satellites, and by the

late 1960s, PV had become the established source of power for them. After the successful application of solar panels on the Vanguard satellite it still was not until the

energy crisis, in the 1970s, that photovoltaic solar panels gained use outside of back up power suppliers on spacecraft. Photovoltaics went on to play an essential part in

the success of early commercial satellites such as Telstar, and they remain vital to the telecommunications infrastructure today.

Building-integrated photovoltaics (BIPV), shown here on the roof of the "Friedenskirche" in Tübingen, Germany, cover the roofs of an increasing number of homes.The high cost of solar cells limited terrestrial uses throughout the 1960s. This

changed in the early 1970s when prices reached levels that made PV generation competitive in remote areas without grid access. Early terrestrial uses included powering telecommunication stations, offshore oil rigs, navigational buoys and

railroad crossings. These off-grid applications accounted for over half of worldwide installed capacity until 2004.

The 1973 oil crisis stimulated a rapid rise in the production of PV during the 1970s and early 1980s. Economies of scale which resulted from increasing production along

with improvements in system performance brought the price of PV down from 100 USD/watt in 1971 to 7 USD/watt in 1985. Steadily falling oil prices during the early

1980s led to a reduction in funding for photovoltaic R&D and a discontinuation of the tax credits associated with the Energy Tax Act of 1978. These factors moderated

growth to approximately 15% per year from 1984 through 1996.

Since the mid-1990s, leadership in the PV sector has shifted from the US to Japan and Europe. Between 1992 and 1994 Japan increased R&D funding, established net

metering guidelines, and introduced a subsidy program to encourage the installation of residential PV systems. As a result, PV installations in the country climbed from

31.2 MW in 1994 to 318 MW in 1999, and worldwide production growth increased to 30% in the late 1990s.

Germany became the leading PV market worldwide since revising its feed-in tariffs as part of the Renewable Energy Sources Act. Installed PV capacity in Germany has risen from 100 MW in 2000 to approximately 4,150 MW at the end of 2007. After

2007, Spain became the largest PV market after adopting a similar feed-in tariff structure in 2004, installing almost half of the photovoltaics (45%) in the world, in

2008, while France, Italy, South Korea and the U.S. have seen rapid growth recently due to various incentive programs and local market conditions. The power output of domestic photovoltaic devices is usually described in kilowatt-peak (kWp) units, as

most are from 1 to 10 kW.

Concentrating photovoltaics (CPV) are another new method of electricity generation from the Sun. CPV systems employ sunlight concentrated onto photovoltaic surfaces

for the purpose of electrical power production. Solar concentrators of all varieties may be used, which are often mounted on a solar tracker in order to keep the focal point

upon the cell as the sun moves across the sky. Tracking can increase flat panel photovoltaic output by 20% in winter, and by 50% in summer.

EXPERIMENTAL SOLAR POWER

A solar updraft tower (also known as a solar chimney or solar tower) consists of a large greenhouse that funnels into a central tower. As sunlight shines on the

greenhouse, the air inside is heated, and expands. The expanding air flows toward the central tower, where a turbine converts the air flow into electricity. A 50 kW

prototype was constructed in Ciudad Real, Spain and operated for eight years before decommissioning in 1989.

Thermoelectric, or "thermovoltaic" devices convert a temperature difference between dissimilar materials into an electric current. First proposed as a method to store solar

energy by solar pioneer Mouchout in the 1800s, thermoelectrics remerged in the Soviet Union during the 1930s. Under the direction of Soviet scientist Abram Ioffe a

concentrating system was used to thermoelectrically generate power for a 1 hp engine.

Thermogenerators were later used in the US space program as an energy conversion technology for powering deep space missions such as Cassini, Galileo and Viking.

Research in this area is focused on raising the efficiency of these devices from 7–8% to 15–20%.

A new technology, developed by the Idaho National Laboratory, uses nanoantennas to harvest solar power. Nanoantennas use the infrared radiation of the sun to convert

energy. During the day the Earth's atmosphere lets some of the infrared radiation to pass through it and absorbs the rest. At night the earth emits it.

DEVELOPMENT

Nellis Solar Power Plant, 14 MW power plant installed 2007 in Nevada- America is the largest photovoltaic power plant in North America

Beginning with the surge in coal use which accompanied the Industrial Revolution, energy consumption has steadily transitioned from wood and biomass to fossil fuels. The early development of solar technologies starting in the 1860s was driven by an

expectation that coal would soon become scarce. However development of solar technologies stagnated in the early 20th century in the face of the increasing

availability, economy, and utility of coal and petroleum.

1950-1970In 1965 Ormat Industries established to commercialise the Organic Rankine Cycle

turbine concept.

The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar

technologies. 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 US (SERI, now NREL), Japan (NEDO), and Germany (Fraunhofer Institute for Solar Energy

Systems ISE).

1970-2000Between 1970 and 1983 photovoltaic installations grew rapidly, but falling oil prices

in the early 1980s moderated the growth of PV from 1984 to 1996.

2000-Present

Photovoltaic production growth has averaged 40% per year since 2000 and installed capacity reached 10.6 GW at the end of 2007 and 14.73 GW in 2008.

Since 2006 it has been economical for investors to install photovoltaics for free in return for a long term power purchase agreement. 50% of commercial systems were installed in this manner in 2007 and it is expected that 90% will by 2009. Nellis Air

Force Base is receiving photoelectric power for about 2.2 ¢/kWh and grid power for 9 ¢/kWh.

Commercial concentrating solar thermal power (CSP) plants were first developed in the 1980s. CSP plants such as SEGS project in the United States have a levelized

energy cost (LEC) of 12–14 ¢/kWh. The 11 MW PS10 power tower in Spain, completed in late 2005, is Europe's first commercial CSP system, and a total capacity

of 300 MW is expected to be installed in the same area by 2013.

In August 2009, First Solar announced plans to build a 2 GW photovoltaic system in Ordos City, Inner Mongolia, China in four phases consisting of 30 MW in 2010, 970 MW in 2014, and another 1000 MW by 2019. As of June 9, 2009, there is a new solar thermal power station being built in the Banaskantha district in North Gujarat. Once

completed, it will be the world's largest.

Solar installations in recent years have also begun to expand into residential areas, with governments offering incentive programs to make "green" energy a more

economically viable option. In Ontario, Canada, the Green Energy Act passed in 2009 created a feed-in-tariff program that pays up to 80.2¢/kWh to solar PV energy

producers, guaranteed for 20 years. The amount scales up based on the size of the project, with projects under 10KW receiving the highest rate. (People participating in

a previous Ontario program called RESOP (Renewable Energy Standard Offer Program), introduced in 2006, and paying a maximum of 42¢/kWh, were allowed to

transfer the balance of their contracts to the new FIT program. The program is designed to help promote the government's green agenda and lower the strain often

placed on the energy grid at peak hours. In March, 2009 the proposed FIT was increased to 80¢/kWh for small, roof-top systems (≤10 kW).

Financial incentives supporting installation of solar power generation are aimed at increasing demand for solar photovoltaics such that they can become competitive with

conventional methods of energy production. Another innovative way to increase demand is to harness the green purchasing power of academic institutions

(universities and colleges). This has been shown to be potentially influential in catalyzing a positive spiral-effect in renewables globally.

ENERGY STORAGE METHODS

Solar energy is not available at night, making energy storage an important issue in order to provide the continuous availability of energy. Both wind power and solar

power are intermittent energy sources, meaning that all available output must be taken

when it is available and either stored for when it can be used, or transported, over transmission lines, to where it can be used. Wind power and solar power can be

complementary, in locations that experience more wind in the winter and more sun in the summer, but on days with no sun and no wind the difference needs to be made up

in some manner.

This energy park in Geesthacht, Germany, includes solar panels and pumped-storage hydroelectricity

The Solar Two used this method of energy storage, allowing it to store enough heat in its 68 m³ storage tank to provide full output of 10 MWe for about 40 minutes, with an efficiency of about 99%. Salts 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, have the potential to eliminate the

intermittency of solar power, by storing spare solar power in the form of heat; and using this heat overnight or during periods that solar power is not available to produce electricity. This technology has the potential to make solar power dispatchable, as the

heat source can be used to generate electricity at will. Solar power installations are normally supplemented by storage or another energy source, for example with wind

power and hydropower.

Off-grid PV systems have traditionally used rechargeable batteries to store excess electricity. With grid-tied systems, excess electricity can be sent to the transmission

grid. Net metering programs give these systems a credit for the electricity they deliver to the grid. This credit offsets electricity provided from the grid when the system

cannot meet demand, effectively using the grid as a storage mechanism. Credits are normally rolled over month to month and any remaining surplus settled annually.

Pumped-storage hydroelectricity stores energy in the form of water pumped when surplus electricity is available, from a lower elevation reservoir to a higher elevation one. The energy is recovered when demand is high by releasing the water: the pump

becomes a turbine, and the motor a hydroelectric power generator.

Combining power sources in a power plant may also address storage issues. The Institute for Solar Energy Supply Technology of the University of Kassel pilot-tested a combined power plant linking solar, wind, biogas and hydrostorage to provide load-

following power around the clock, entirely from renewable sources.

ENERGY PAYBACK TIME

The energy payback time of a power generating system is the time required to generate as much energy as was consumed during production of the system. In 2000 the energy payback time of PV systems was estimated as 8 to 11 years and in 2006 this was estimated to be 1.5 to 3.5 years for crystalline silicon PV systems and 1-1.5

years for thin film technologies (S. Europe).

Another economic measure, closely related to the energy payback time, is the energy returned on energy invested (EROEI) or energy return on investment (EROI), which

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 available and metering techniques.) With lifetimes of at least 30 years, the EROEI of PV systems are in the range of 10 to 30, thus generating enough energy over their lifetimes to reproduce themselves many times (6-31 reproductions) depending on what type of material,

balance of system (BOS), and the geographic location of the system.

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.

The calculated total cost per kilowatt-hour of electricity generated by a photovoltaic system is a function of the investment cost, cost of capital and depreciation period.

The annual energy output in kilowatt-hours expected from each installed peak kilowatt 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, 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).

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. 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. A prototype ready for commercialization achieved a concentration of

solar energy that was more than 1,000 times greater than standard flat panels.

GRID PARITY

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.

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.

General Electric's Chief Engineer predicts grid parity without subsidies in sunny parts of the United States by around 2015. Other companies predict an earlier date: 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.

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.

1.vertical integration of the supply chain;2.origination of power purchase agreements (PPAs) by solar power companies;

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 of Concentrating Solar Power (CSP) by the US Department of Energy that total over $14 million. The goal of the DOE R&D program, working in collaboration with partners

such as Abengoa Solar, is to develop CSP technologies that are competitive with conventional energy sources (grid parity) by 2015. Concentrating photovoltaics

(CPV) could reach grid parity in 2011.

Due to the growing demand for photovoltaic electricity, more companies enter into this market and lower cost of the photovoltaic electricity would be expected.

NET METERING

Net metering is particularly important because it can be done with no changes to standard electricity meters , which accurately measure power in both directions and

automatically report 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. As more photovoltaics are used ultimately additional transmission and storage will need to be provided, normally in the form of pumped

hydro-storage. Normally with net metering, deficits are billed each month while surpluses are rolled over to the following month and paid annually.

ENVIRONMENTAL IMPACT

The siting of solar power plants is an issue. Placement in environmentally sensitive locations can be an issue, as can the noise they produce. 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.

Location

The location of solar power plants is an issue as more plants were built or planned. Locating a solar power plant in a pristine location such as the Mohave Desert raised

objections. More acceptable to environmentalists is use of farmland taken out of production due to salinization or lack of water, or other contaminated locations such as reclaimed landfills or mines. Noise, such as that caused by hundreds of sterling

engines, is another issue.

Greenhouse gases

Life cycle greenhouse gas emissions are now in the range of 25-32 g/kWh and this could decrease to 15 g/kWh in the future. For comparison (of weighted averages), a

combined cycle gas-fired power plant emits some 400-599 g/kWh, an oil-fired power plant 893 g/kWh, a coal-fired power plant 915-994 g/kWh or with carbon capture and

storage some 200 g/kWh, and a geothermal high-temp. power plant 91-122 g/kWh. Only wind and geothermal low-temp. are better, emitting 11 g/kWh and 0-1 g/kWh on

average. Including the energy needed to mine uranium and the energy-intensity of power plant construction and decommissioning, some place nuclear power plants' life-cycle greenhouse gas emissions below 40 g/kWh, but others give much higher figures.

Using renewable energy sources in manufacturing and transportation would further drop carbon emissions. 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 monthly.

Cadmium

One issue that has often raised concerns is the use of cadmium in cadmium telluride solar cells (CdTe is only used in a few types of PV panels). Cadmium in its metallic

form is a toxic substance that has the tendency to accumulate in ecological food chains. The amount of cadmium used in thin-film PV modules is relatively small (5-

10 g/m²) and with proper emission control techniques in place the cadmium emissions from module production can be almost zero. Current PV technologies lead to

cadmium emissions of 0.3-0.9 microgram/kWh over the whole life-cycle. Most of these emissions actually arise through the use of coal power for the manufacturing of

the modules, and coal and lignite combustion leads to much higher emissions of cadmium. Life-cycle cadmium emissions from coal is 3.1 microgram/kWh, lignite

6.2, and natural gas 0.2 microgram/kWh.

Note that if electricity produced by photovoltaic panels were used to manufacture the modules instead of electricity from burning coal, cadmium emissions from coal power

usage in the manufacturing process could be entirely eliminated.

SOLAR POWER USAGE

Grid-connected solar photovoltaics had an installed capacity of nearly 21,000 MW at the end of 2009, compared to 600 MW of concentrating solar thermal and 149,000

MW of Solar heating. Germany and Japan have been leading in terms of cumulative PV capacity, China in solar heating. In recent years many countries (notably in

Western Europe) have begun to enact financial incentives encouraging solar power.

Germany

Germany is one of the world's top photovoltaics (PV) installers, with a solar PV capacity in 2009 of 8,877 megawatts (MW), and 6,200 GWh of electricity generated

in 2009. Solar power now meets about 1.1 percent of Germany's electricity demand, a share that some market analysts expect could reach 25 percent by 2050.

India

India is both densely populated and has high solar insolation, providing an ideal combination for solar power. In solar energy sector, some large projects have been

proposed, and a 35,000 km² area of the Thar Desert has been set aside for solar power projects, sufficient to generate 700 to 2,100 gigawatts.

In July 2009, India unveiled a $19 billion plan, to produce 20 GW of solar power by 2020. Under the plan, solar-powered equipment and applications would be mandatory in all government buildings including hospitals and hotels. On November 18, 2009, it

was reported that India was ready to launch its National Solar Mission under the

National Action Plan on Climate Change, with plans to generate 1,000 MW of power by 2013.

Iran

The average solar radiation for the whole of Iran is about 19.23 Mega joules per square meter, and it is even higher in the central part of Iran. The variation of

radiation varies in the south-east part to 5.4 kWh/m in central region from 2.8 kWh/m. The calculations show that the amount of useful solar radiation hours in Iran exceeds

2800 hours per year.

For this reason, the first Photovoltaic (PV) site, with capacity of 5 kW DC was established in the central region of Iran in Doorbid village Yazd in 1993. Following this, in 1998, the second photovoltaic site with 27 kW AC capacity was installed in Hosseinian and Moalleman villages in Semnan, 450 Km inland from Tehran. The capacity of these power plants has recently increased to 10 kW AC and 92 kW AC

respectively. The power plant installed at Doorbid, works independently from the grid system, while the one installed at Hosseinian and Moalleman, is connected to grid. It

is worth mentioning that all equipment of these sites is made in Iran.

Iran took its first step toward the large scale realization of that potential recently(2009) with the inauguration of its first solar energy plant. The plant was constructed with domestic materials and labour in Shiraz, the Fars province. This

solar thermal plant joins some 4,075 small scale solar thermal installations throughout Iran–3,781 residential solar water heaters and 294 public baths heated with solar thermal energy. Iran makes less use of photovoltaic energy, but the Ministry of

Energy News Agency mentions a 40 house solar village supplied with photovoltaic energy.

Israel

Solar water heaters on a rooftop in JerusalemAs of the early 1990s, all new residential buildings were required by the government to install solar water-heating systems, and Israel's National Infrastructure Ministry estimates that solar panels for water-heating satisfy 4% of the country's total energy demand. Israel and Cyprus are the per-capita

leaders in the use of solar hot water systems with over 90% of homes using them.

Israeli research has advanced solar technology to a degree that it is almost cost-competitive with fossil fuels. Its abundant sun made the country a natural location for

the promising technology. The high annual incident solar irradiance in the Negev Desert has spurred an advanced solar research and development industry, with

Harry Tabor and David Faiman of the National Solar Energy Center two of its more prominent members. At the end of 2008 a feed-in tariff scheme was approved, which

resulted in the building of residential and commercial solar energy power station projects.

United States

Solar power in the United States accounted for less than 0.1% of the county's electricity generation in 2006. Renewable resources (solar, wind, geothermal, hydroelectric, biomass, and waste) provided nearly 12 percent of the nation's

electricity supply in 2003. The DoE has established the goal of generating 10-15% of the nation's energy from solar sources by 2030.

LIFESPAN

Most commercially available solar cells are capable of producing electricity for at least twenty years without a significant decrease in efficiency. The typical warranty given by panel manufacturers is for a period of 25 – 30 years, wherein the output shall not fall below 85% of the rated capacity

SOLAR CHARGED VEHICLE

Solar-charged vehicles are vehicles that use off-board renewable electricity that can be generated in the driver's facilities.

They combine renewable energy with all-electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) in a different manner than mere solar vehicles. The latter

are powered by electricity generated by (flexible) solar panels located directly on the vehicles themselves. Solar-charged vehicles are indirectly powered by renewable

electricity, that is, by electricity generated by solar panels or wind turbines located elsewhere offboard of the vehicle, often on a rooftop of a carport, home or business,

or grid-connected indeed anywhere.

In any case, the same vehicle can use offboard renewable electricity and onboard solar panels, these last ones to extend the all-electric range or provide power to the air

conditioning.

In contrast to lightweight vehicles that participate in events such as the World Solar Challenge, solar-charged vehicles can carry more batteries and offer seating and be

used like internal combustion engine powered vehicles: cars , motorcycles, bicycles or boats.

The number of solar-charged vehicles is currently small. However, interest in solar-charged vehicles is fast growing. For example, New York City recently saw its first

solar-charged plug-in station unveiled. Solar-charged plug-in stations are also appearing in other places such as Hawaii and Japan. and Australia, where a solar-

charged bus is being used by the City of Adelaide. Some celebrities in the U.S. have also solar-charged their electric vehicles. Electric bicycles are easy to use as solar-charged vehicles because only a rather small panel area is needed (that can be in a

solar jacket). Some manufacturers of these vehicles sell their customers solar electricity along with the bicycles.

HISTORY

Historically, solar-charged vehicles evolved soon after the first solar racing vehicles of the Tour de Sol in 1985. The organisers introduced racing classes allowing road-side charging with panels carried by support vehicles, and later with electricity from the grid, provided that the team could prove ownership of enough grid-feeding solar

panels anywhere in the world. The production and consumption of solar energy became separated both in place and in time. The rooftop solar panels could work at their full capacity whereas on-board panels have nothing to do once the vehicles'

batteries are fully charged.

Many of those solar-charging their vehicles in the U.S. are members of a plug-in electric vehicle (PEV) movement which grew out of the opposition to the confiscation

and subsequent destruction of EVs such as the General Motors EV1 and the Toyota RAV4 EV by large automakers in the early 2000s.

This movement received a considerable boost with the release of the now cult-classic documentary Who Killed the Electric Car?, produced by Chris Paine. Paine is

currently working on a follow-up to this documentary called Revenge of the Electric Car.

Numbers of solar-charged vehicles

It’s unclear how many solar-charged vehicles there are currently in the United States, or the world. Generally, the solar + EV/PHEV synergy – often simply referred to as

EV/PV, EV+PV or PVEV-- has so far been the province of a relatively few people, in part because mainstream EVs have not been widely available to consumers. However, it is possible that the comparatively low number of solar-charged vehicles will soon increase as a combination of small automotive start-ups such as Tesla Motors and Coda Automotive and major automakers such as Nissan, GM, Mitsubishi and Ford

begin rolling EVs and PHEVs off their assembly lines in large numbers and conversion of combustion vehicles to plug-ins. In fact, Tesla Motors recently

delivered its 1,000th Tesla Roadster.

Some Roadster owners have publicized their solar-charged driving experiences with the Tesla Roadster online. Plug In America has also published a list of selected

current EV owners on its web site, and many of these use solar energy to fully, or partially, charge the batteries of their EVs. The Sierra Club has also profiled three

solar-charged drivers on its web pages.

Celebrity solar-charged drivers

Perhaps the most famous of those currently driving a solar-charged vehicle is Ed Begley Jr. Begley powers many of his annual miles in a Toyota RAV4 EV with solar-

generated electricity. Begley currently has a reality show about green living called Living With Ed on Planet Green with his wife, actress Rachelle Carson. Former

Baywatch star and environmental activist Alexandra Paul, has also solar-charged her Toyota RAV4 EV for about a year while living in Malibu, Calif.

SOLAR CHARGED BUSES

Automobiles are not the only solar-charged vehicles. For example, the City of Adelaide, Australia purchased an electric bus -- which it named Tindo -- whose

batteries are 100-percent solar-charged by a solar-installation on the Adelaide Central Bus Station. The solar PV system generates nearly 70,000 kilowatt hours of

renewable electricity each year and is the city’s largest grid-connected PV system.

Solar-charged vehicles and air pollution

Solar-charged vehicles have the potential to substantially reduce air pollution. For example, Environment Texas has published an analysis of more than 40 research

reports on the environmental impact of electric cars. Entitled 'Plug-In Cars: Powering America Toward a Cleaner Future', the report concludes that an electric vehicle fleet

powered by renewable electricity, such as solar and wind, could virtually eliminate air pollution in the U.S. More specifically, the report points to a 2003 study by the

University of California, Berkeley Center for Entrepreneurship & Technology which concluded that if half of the light vehicles in the United States were electric vehicles powered by completely clean renewable electricity in 2030, total U.S. fleet emissions

would be reduced by 62 percent.

SOLAR LAMP

A solar lamp is a portable light fixture composed of a LED lamp, a photovoltaic solar panel, and one or more rechargeable batteries.

A garden solar lamp

Solar panel on top the lamp recharges the battery.Outdoor lamps are used for lawn and garden decorations. Indoor solar lamps are also used for general illumination (i.e.

for garages and the solar panel is deattached of the LED lamp).

Solar lights are used for decoration, and come in a wide variety of designs. They are sometimes holiday-themed and may come in animal shapes. They are frequently used

to mark, for example, footpaths or the areas around swimming pools.

Solar lamps recharge during the day. At dusk, they turn on (usually automatically, although some of them includes a switch for on, off and automatic) and remain

illuminated overnight, depending on how much sunlight they receive during the day. Discharging time is generally 8 to 10 hours.

Some solar lights do not provide as much light (watts) as a line-powered lighting system, but they are easily installed and maintained, and provide a cheaper alternative

to wired lamps.