Solar power involves using solar cells to convert sunlight into electricity, using sunlight hitting solar thermal panels to convert sunlight to heat water or air, using sunlight hitting a parabolic mirror to heat water (producing steam), or using sunlight entering windows for passive solar heating of a building. It would be advantageous to place solar panels in the regions of highest solar radiation.[26] In the Phoenix, Arizona area, for example, the average annual solar radiation is 5.7 kW·h/(m²·day),[27] or 2.1 MW·h/(m²·yr). Electricity demand in the continental U.S. is 3.7×1012kW·h per year. Thus, at 20% efficiency, an area of approximately 3500 square miles (3% of Arizona's land area) would need to be covered with solar panels to replace all current electricity production in the US with solar power. The average solar radiation in the United States is 4.8 kW·h/(m²·day),[28] but reaches 8–9 kWh/m²/day in parts of the Southwest.
At the end of 2009, cumulative global photovoltaic (PV) installations surpassed 21 GW[6][7][8] andPV power stations are popular in Germany and Spain.[9] Solar thermal power stations operate in the USA and Spain, and the largest of these is the 354 megawatt (MW) SEGS power plant in theMojave Desert.[10]
China is increasing worldwide silicon wafer capacity for photovoltaics to 2,000 metric tons by July 2008, and over 6,000 metric tons by the end of 2010.[29] Significant international investment capital is flowing into China to support this opportunity. China is building large subsidized off-the-grid solar-powered cities in Huangbaiyu and Dongtan Eco City. Much of the design was done by Americans such as William McDonough.[30]
Reference: Wikipedia
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