The Sun produces radiant energy by consuming hydrogen in nuclear fusion reactions. Solar energy is the solar radiation that reaches the earth. It is completely free and totally inexhaustible. Solar energy supports all life on Earth: it makes plants grow, which can be burned as "biomass" fuel or, if left to rot in swamps and compressed underground for millions of years, in the form of coal and oil. Heat from the sun causes temperature differences between areas, producing winds, which can also ultimately power wind-turbines. This vast, clean energy resource represents a viable alternative to the fossil fuels.
How it Works
Solar energy is transmitted to the earth in portions of energy (photons), which interact with the earth's atmosphere and surface in about 8 minutes and 20 seconds. Solar energy is then captured and used for heating water for domestic use, space heating of buildings and power generation.
Solar energy technologies convert the sun’s light into usable electricity or heat. Solar energy systems can be divided into two major categories: electric and thermal. Solar Electrical (photovoltaic) cells produce electricity directly, while solar thermal systems produce heat for buildings, industrial processes or domestic hot water. Solar energy systems have no fuel costs, and very low operating and maintenance costs. Solar radiation conditions are tracked by the weather station located near the array. The station usually contains a pyranometer to measure the amount of solar energy reaching the array, a thermometer to measure the temperature and an anemometer to measure wind speed.
Electrical (Photovoltaic) Cells
Photovoltaics (PVs) convert sunlight directly into electricity, using
semi-conductors made from silicon or other materials. PVs generate
power on a much smaller scale than traditional utility power plants,
so they can often provide high-value electricity exactly where and
when it is needed. PVs are often the best choice for supplying power
for remote, "off-grid" sites or in situations where the transmission
or distribution system would otherwise need to be upgraded in order
to meet peak demands.
There are three basic types of solar cells:
- monocrystalline cells, sliced from a single large crystal of silicon
- polycrystalline cells, manufactured assembling a multiple crystals, and
- amorphous solar cell, made by depositing a thin film of silicon onto a sheet of another material such as steel
Direct-use thermal systems usually use solar energy directly as a source of heat. The most common systems use sunlight to heat water for houses or swimming pools, or use collector systems or passive solar architecture to heat living and working spaces. These systems can replace electric or fuel-based heating systems, reducing the overall energy costs even further. Thermal systems can also produce electricity by operating heat engines or by boiling steam to spin electric turbines.
Solar power is an extremely clean way to generate electricity. There is no air emissions associated with the operation of solar modules or direct application technologies. Residential-scale passive construction, photovoltaic, solar water heating, and other direct applications reduce land use impacts from typical utility generation, transmission and distribution.