Solar Power Technologies
There are three basic ways in which solar energy is converted into forms which are useful. Two of them, photovoltaics (PV) and concentrating solar power (CSP), can be used for the generation of electricity. The third, low-temperature solar collection, simply absorbs the heat energy of the sun and uses that directly for heating purposes.
Photovoltaic cells use a phenomenon called the photoelectric effect to convert solar radiation (visible light and infrared radiation for the most part) into electricity, which can then be used directly or fed into the electric grid. This is a versatile means of using solar energy, since the electricity can be used immediately for any purpose, large or small. However PV is also, presently, the most expensive way to harness the sun's energy and, thus, provides at this time the least amount to the aggregate use of solar power.
Concentrating Solar Power
Concentrating solar power is currently the most economically successful method for gathering solar energy and converting it to electricity. It involves the use of highly efficient, reflective materials to concentrate solar radiation, focus that radiation on an absorbing medium such as an oil, transfer the resulting heat from that medium to a steam system, which drives a generator to produce electricity. CSP technologies that have been successfully used include dish/engine systems, parabolic troughs, and central power towers. The most economically feasible and most promising of these are currently the parabolic troughs, but all are undergoing extensive development and their relative efficiencies and importance could easily change over time.
Low-temperature Solar Collectors
The last method for making use of solar energy, low-temperature solar collectors, simply absorbs sunlight, converts it to heat and uses that heat directly for hot water or space heating in residential, commercial, and industrial facilities. Many of the familiar solar panels mounted on or near homes, offices or other buildings where the collected solar heat energy will be immediately used are of this type.