Solar energy is a renewable energy source – it comes from the sun. It can be utilized by different solar technologies to capture the sun’s direct and diffused light. Direct sunlight can be used for solar thermal applications (heat radiation) and direct and diffused unlight can be used by photovoltaic technologies (PV) to create electricity.
There are three major solar technologies:
1. Photovoltaic (PV) panels that convert sunlight (direct sunlight and diffused sunlight) directly into electricity. Solar cells are also known as photovoltaic (PV) cells, photovoltaic meaning literally "light-electricity". Solar photovoltaic panels contain rows of solar cells (semiconductor devices made of crystalline silicon) electrically connected together and encapsulated in a weatherproof packaging. Multiple solar panels connected together are referred to as an "array". A solar PV system consists of the solar panels, a mounting system (roof or ground), and an inverter to convert DC electrical current to AC for household or commercial consumption. The higher the efficiency of the solar panel, the more power that can be generated per solar panel. This technology has residential, commercial and industrial applications.
2. Solar Hot Water Heating, sometimes called solar domestic hot water systems, uses direct sunlight to heat either water or a heat-transfer fluid, such as a water-glycol antifreeze mixture, in collectors generally mounted on a roof. The major applications of solar thermal energy at present are heating swimming pools, heating water for domestic or commercial use, and space heating for buildings. For these purposes, the general practice is to use flat-plate solar energy or evacuated tube collectors with a fixed orientation.
3. Concentrated Solar Power that uses mirrors to focus direct sunlight onto photovoltaic cells or panels to create electricity (concentrating photovoltaics – CPV), and solar thermal technologies (concentrating solar thermal - CST) that use direct sunlight and mirrors to provide high temperature heat for steam generators in a conventional power plant. Both technologies have a utility-scale or industrial-scale applications.
The Department of Energy’s Office of Energy Efficiency and Renewables has an excellent web site on its Solar Energy Technologies Programs that may be of interest to learn more about federal programs for these technologies.