With current energy prices rising every year and stores of natural energy quickly depleting, alternative sources of power are beginning to take center stage. Solar energy is one of the most abundant sources of heat and electricity on the planet and scientists are beginning to develop methods for harnessing it to power our homes and workplaces.
There are two classifications for solar power that denote exactly how the solar energy is used: direct and indirect. Photovoltaic cells are a direct form of energy, since the solar energy is directly converted into energy; a black bottomed pool that collects solar energy to heat it would also be considered direct. An indirect method require one or more intermediary steps in order to convert sunlight into power. Plant photosynthesis is indirect because it creates possible fuel sources (carbon, biofuel, etc.) instead of energy itself.
There are two main ways of tapping the sun for energy, solar thermal power and photovoltaic electricity. Solar thermal energy gathers heat energy from the sun to operate turbines that generate electricity. Photovoltaic electricity is generated using specialized silicon cells that interact with sunlight to create an electric current.
Solar thermal power is the process through which the sun's heat energy is collected and used to create electrical current. Solar thermal energy collectors resemble satellite arrays, with a dish covered that concentrates the sun's heat on a small point. Once collected, this thermal energy boils water, and in turn, that steam is used to to turn turbines that create the electricity. This process is an indirect method of creating solar energy and, unfortunately, can only be used when the sun is shining.
Photovoltaic energy is a direct form of solar energy that converts the sun's rays directly into electricity. Photovoltaic cells, little chips made of silicon that absorb the sun's energy, are made of two layers of specially treated silicon. When light hits the bottom layer, photons knock electrons loose creating an imbalance in charges between the top and bottom. Electrons flow freely through the connector when the two layers are connected, creating an electric current. Small photovoltaic cells are inexpensive to build and maintain, and you can see them at work on any old, sunlight-powered calculator.