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) systems. This was double the 435 MW installed in 2009 around the U.S.[16] According to a 2011 survey conducted by independent polling firm Kelton Research, nine out of 10 Americans support the use and development of solar technology. Eight out of 10 respondents indicated that "the federal government should support solar manufacturing in the U.S. and should give federal subsidies for solar energy".[17] According to the Energy Information Administration, in 2010, subsidies to the solar power industry amounted to 8.2% ($968 million) of all federal subsidies for electricity generation.[18] Solar Energy Industries Association and GTM Research found that the amount of new solar electric capacity increased in 2012 by 76 percent from 2011, raising the United States’ market share of the world’s installations above 10 percent, up from roughly 5 to 7 percent in the last seven years. [19]

Hydrogen fuel does not occur naturally on Earth and thus is not an energy source, but is an energy carrier. Currently it is most frequently made from methane or other fossil fuels. However, it can be produced from a wide range of sources (such as wind, solar, or nuclear) that are intermittent, too diffuse or too cumbersome to directly propel vehicles. Integrated wind-to-hydrogen plants, using electrolysis of water, are exploring technologies to deliver costs low enough, and quantities great enough, to compete with traditional energy sources.[1]

While methods of hydrogen production that do not use fossil fuel would be more sustainable

Marine Current Turbines is about to field test a submerged 300 kW tidal turbine off Devon in the United Kingdom

The manufacturers of all these devices expect to deliver energy at a cost of 10-14 US cents per kWh, falling to below 6 US cents as experience grows and technologies mature

Solar energy is by far the Earth's most available energy source. Solar power is capable of providing many times the total current energy demand. But it is an intermittent energy source, meaning that it is not available at all times.

Photons Carry Solar Energy Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. Special treatment of the material surface during manufacturing makes the front surface of the cell more receptive to free electrons, so the electrons naturally migrate to the surface.

Weather Affects Photovoltaics The performance of a photovoltaic array is dependent upon sunlight. Climate conditions (such as clouds or fog) have a significant effect on the amount of solar energy received by a photovoltaic array and, in turn, its performance.

History of the Photovoltaic Cell The first practical photovoltaic (PV) cell was developed in 1954 by Bell Telephone researchers examining the sensitivity of a properly prepared silicon wafer to sunlight. Beginning in the late 1950s, PV cells were used to power U.S. space satellites. PV cells were next widely used for small consumer electronics like calculators and watches and to provide electricity in remote or "off-grid" locations were there were no electric power lines. Technology advances and government financial incentives have helped to greatly expand PV use since the mid-1990s.

Using solar energy produces no air or water pollution and no greenhouse gases, but does have some indirect impacts on the environment.