Solar technologies use energy from the sun to generate electricity and/or provide heat and light. The conversion process can be thermal or photovoltaic. Thermal technologies provide power by concentrating the sun's heat to power generators, in a system called concentrating solar power (CSP). The three types of CSP technologies include parabolic trough systems, solar dish systems, and power tower systems. These systems use reflective materials to concentrate the sun’s heat to drive a generator that produces electricity. The main advantages of CSP systems are their relatively low cost and ability to store solar power in order to provide electricity during periods of peak demand.

CSP capacity in the United States today is about 375 MW. An additional 64 MW CSP plant is currently under construction in Nevada. With continued technological improvements, these systems may someday offer the possibility of providing commercially viable solar power on a large scale.

CSP: This solar dish system is an electric generator that "burns" sunlight instead of gas or coal to produce electricity. The dish, a concentrator, is the primary solar component of the system, collecting the energy coming directly from the sun. A thermal receiver absorbs the concentrated beam of solar energy, converts it to heat, and transfers the heat to the generator.
(Source: Sandia National Laboratories)

Photovoltaics (PVs) are devices or banks of devices that use semiconductor materials to convert sunlight directly to electricity. Sunlight received by photovoltaic technologies changes the location of the electrons in silicon material to create a voltage potential, creating a positive and negative charge similar to a battery. Photovoltaic products come in a variety of shapes and sizes and can be used in many situations, from individual home or business roofs to large grid-connected systems. These technologies have very little impact on the environment and do not produce harmful greenhouse gas emissions. In addition, they need very little maintenance to function properly. However, recent reports suggest that growing demand for silicon in the PV industry, combined with the demand in the computer industry, is driving up prices.

Photovoltaic: When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current -- that is, electricity. This electricity can then be used to power a load, such as a light or a tool.
(Source: NASA)

Finally, some technologies use solar energy to create heat or light directly. In solar heating, solar collectors absorb the sun’s energy to provide low-temperature water heating or space heating in residential or commercial buildings. Examples of these technologies include solar pool heating in condominium complexes or hotels and solar water heating to reduce the need for conventional hot-water heaters. Solar lighting technologies focus the sun’s light into a fiber-optic system to illuminate building interiors.

Sources:

• U.S. Department of Energy’s Energy Efficiency and Renewable Energy Program (EERE)
• EERE Concentrating Solar Power
• EERE Photovoltaics
• Energy Information Agency Solar Thermal Energy Page
• Energy Information Agency Solar Photovoltaic Energy Page
• NASA Photovoltaic Information Page
• Sandia National Laboratory CSP Information Page