Solar energy

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At the equator, the Sun provides approximately 1000 watts per square meter on Earth's surface.
At the equator, the Sun provides approximately 1000 watts per square meter on Earth's surface.

Solar energy has been used in many traditional technologies for centuries and has come into widespread use where other power supplies are absent, such as in remote locations and in space. Solar power is the technology to get usable energy from the light of the Sun.

Solar energy is currently used in a number of applications:

Contents

[edit] Energy from the Sun

Theoretical annual mean insolation, at the top of Earth's atmosphere (top) and at the surface on a horizontal square meter.
Theoretical annual mean insolation, at the top of Earth's atmosphere (top) and at the surface on a horizontal square meter.
Map of global solar energy resources. The colours show the average available solar energy on the surface during 1991 to 1993. For comparison, the dark disks represent the land area required to supply the primary energy demand in the year 2010 using currently available technology (i.e. with a conversion efficiency of 8%).
Map of global solar energy resources. The colours show the average available solar energy on the surface during 1991 to 1993. For comparison, the dark disks represent the land area required to supply the primary energy demand in the year 2010 using currently available technology (i.e. with a conversion efficiency of 8%).


After passing through the Earth's atmosphere, most of the sun's energy is in the form of visible and Infrared radiations. Plants use solar energy to create chemical energy through photosynthesis. Humans regularly use this energy burning wood or fossil fuels, or when simply eating the plants.

Solar radiation reaches the Earth's upper atmosphere at a rate of 1366 watts per square meter (W/m2).[1] The first map shows how the solar energy varies in different latitudes.

The second map shows the average global irradiance calculated from satellite data collected from 1991 to 1993. For example, in North America the average insolation at ground level over an entire year (including nights and periods of cloudy weather) lies between 125 and 375 W/m² (3 to 9 kWh/m²/day).[2] This represents the available power, and not the delivered power. At present, photovoltaic panels typically convert about 15% of incident sunlight into electricity; therefore, a solar panel in the contiguous United States on average delivers 19 to 56 W/m² or 0.45 - 1.35 (kW·h/m²)/day.[3]




The dark disks in the third map on the right are an example of the land areas that, if covered with 8% efficient solar panels, would produce slightly more energy in the form of electricity than the total world primary energy supply in 2003.[4] While average insolation and power offer insight into solar power's potential on a regional scale, locally relevant conditions are of primary importance to the potential of a specific site.


A recent concern is global dimming, an effect of pollution that is allowing less sunlight to reach the Earth's surface. It is linked with pollution particles and global warming, and it is mostly of concern for issues of global climate change, but is also of concern to proponents of solar power because of the existing and potential future decreases in available solar energy. The order of magnitude is about 4% less solar energy available at sea level over the timeframe of 1961–90, mostly from increased reflection from clouds back into outer space.[5]

[edit] Types of technologies

Many technologies have been developed to make use of solar radiation. Some of these technologies make direct use of the solar energy (e.g. to provide light, heat, etc.), while others produce electricity.

[edit] See also

Renewable energy

[edit] References

  1. Solar Spectra: Standard Air Mass Zero. NREL Renewable Resource Data Center (2006-10-17). Retrieved on 2006-10-17.
  2. NREL: Dynamic Maps, GIS Data, and Analysis Tools - Solar Maps
  3. us_pv_annual_may2004.jpg. National Renewable Energy Laboratory, US. Retrieved on 2006-09-04.
  4. International Energy Agency - Homepage
  5. Liepert, B. G. (2002-05-02). Observed Reductions in Surface Solar Radiation in the United States and Worldwide from 1961 to 1990. GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 10, 1421. Retrieved on 2006-09-04.

[edit] External links