Thursday, May 1, 2008

Passive Solar, Active Solar and Photovoltaics

There are three different ways to harness the sun's energy: passive solar, using architectural design and natural materials to absorb the sun's energy; active solar, utilizing the sun's heat by means of solar collectors; and a third way in which solar energy can be harnessed is through the use of photovoltaic systems.

Passive solar is the capturing and storing the suns' energy - light and heat - without the use of any mechanical devices. As the solar radiation strikes windows, walls, floors, and other objects within the room it is converted to heat. A good example of a passive solar energy system is a greenhouse.

Active solar uses devices to collect, store, and circulate heat produced from solar energy. Active solar energy technologies convert sunlight into heat by using a particular energy transfer fluid. This is most often water or air but can also be a variety of other substances.

Photovoltaic systems directly convert sunlight into electricity using a semiconductor material such as silicon. The electrical energy from PVs can be stored in batteries for use when there is no sun (during cloudy days or at night).