11. Solar and Photovoltaic

B. Solar Resource

Solar radiation is nearly constant outside the Earth's atmosphere, but the amount of solar energy, or insolation, reaching any point on the Earth varies with changing atmospheric conditions (such as clouds and dust) and the changing position of the Earth relative to the sun. Insolation is greatest in the West and Southwest regions of the United States. Average direct-beam solar radiation in parts of Nevada is more than twice that found through most of the eastern States or in the Northwest.(2) Nevertheless, almost all U.S. regions have useful solar resources that can be accessed for various applications (Figure 24).(3)

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