Solar Energy

How Solar Energy is Formed and Used (continued)

PV cells by themselves are small, at most about 4 inches across, and do not generate enough power for most applications. That’s why, in most photovoltaic systems, PV cells are grouped into larger panels or modules that collect sunlight and convert it into electricity. These panels can be small (like those found on solar-powered calculators) or huge, covering acres of land and providing power for whole buildings.  Most photovoltaic cell panels need a lot of space. Because the sun doesn’t deliver that much energy to any one place at any one time, a large surface area is required to collect the energy at a useful rate.

Solar thermal plants also use sunlight to generate power, but in a different way from PV systems. Solar thermal plants use the sun’s rays to heat liquid, which is then used to heat water and produce steam. This steam then powers a turbine to generate electricity. There are three main types of solar thermal power systems: solar dish, solar power tower, and parabolic trough.

Solar dishes are designed to always point at the sun, collecting concentrated energy and, with the help of a turbine and electric generator, turning that energy into electricity. Solar power towers use mirrors to concentrate the sun’s energy into a central receiver tower, which contains fluid that collects heat. A parabolic trough system uses a long reflector to focus the sun’s rays onto a receiver pipe. Fluid moving through the pipe is then heated and used to heat water, creating steam. This steam is then used in a turbine to generate electricity.

Solar energy is used for heating water for domestic use, heating buildings, drying agricultural products, and generating electrical energy. Solar panels are used in some homes to convert the sun’s rays into electricity. Although not sold commercially, solar-powered vehicles can be found at demonstrations and educational sites globally. Solar cars use PV cells to convert the sun’s energy directly into electrical energy.

See the US Energy Information Administration’s Energy Kids Solar Energy pages for more information.

Photosynthesis

Photosynthesis is solar power at work in nature! It is the process of converting carbon dioxide into organic compounds using energy from the sun’s rays. Photosynthesis is needed to make plants, bacteria and algae grow. It is vital for life on Earth—photosynthesis gives us the fruits, vegetables and grains we eat and also maintains the normal level of oxygen in our atmosphere.