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The ABCs you should know about SOLAR energy

Solar radiation is a general term for the electromagnetic radiation emitted by the sun. Solar thermal energy captures the radiation and converts it into heat to produce energy. Concentrated Solar Power utilizes the high temperature heat to generate electricity.
Photovoltaic systems in contrast convert the radiation into electricity directly. The sunĄŻs waves hit a photovoltaic cell and excite the electrons within layers of the cell. The excited electrons jump back and forth, creating electricity. This electricity is captured by wires running through the PV cells and sends the electricity into your home.


Unlimited Solar Resources

  • In one hour, enough sunlight(1000 Wh per m2 = 1 kWh/m2) falls on the earth to power the world for an entire year
  • If 1% of the Sahara Desert were covered in solar thermal systems, enough energy would be produced to power the entire world
  • Solar radiation along with secondary solar resources such as wind and wave power, hydroelectricity and biomass account for 99.97% of the available renewable energy on Earth.
  • 53,727 mile2 of land in the American southeast that has no primary use today has the potential of 6,877,055 MW from solar power., (excluding land with slope > 1%, <5 contiguous km2, and sensitive lands) and assuming 5 acres per MW.

Types of Solar Radiation

  • Diffuse Solar Radiation is the sunlight that is absorbed, scattered and reflected by all kinds of particles in the air(such as water vapor and clouds).
  • Direct Solar Radiation is the solar radiation that reaches the Earth's surface without being diffused.
  • Direct-Normal Radiation refers to the portion of sunlight that comes directly from the Sun and strikes a surface at a 90-degree angle.
  • The sum of the diffuse and direct solar radiation is called global solar radiation.

Measurement

  • Insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter (W/m2) or kilowatt-hours per square meter per day (kWĄ¤h/(m2Ą¤day)) (or hours/day). Direct estimates of solar energy may also be expressed as watts per square meter (W/m2).
  • In photovoltaics it is commonly measured as kWh/kWp?y (kilowatt hours per year per kilowatt peak rating).
  • Radiation data for solar water heating and space heating systems are usually represented in British thermal units per square foot (Btu/ft2).

Some History of the Concentration Use of Solar Energy--Reclaim the Sun!


archimedes_mirror.jpgAncient Greeks and Romans saw great benefit in what we now refer to as passive solar designĄŞthe use of architecture to make use of the sunĄŻs capacity to light and heat indoor spaces. Romans advanced the art by covering south facing building openings with glass or mica to hold in the heat of the winter sun. Through calculated use of the sunĄŻs energy, Greeks and Romans offset the need to burn wood that was often in short supply.

 

 

 

Bibliography

*the page is contributed by Molly Baker Mercer '12,Hampshire College and Alaxandra Sterling 09ĄŻ Hampshire College


Kennedy; C.E. Advances in Concentrating Solar Power Collectors: Mirrors and Solar Selective Coatings National Renewable Energy Laboratory NREL/PR-550-43695, Oct 2007
Copyright Yiting Wang 2008