SOLAR TECHNOLOGY

Photovoltaic system (or PV) is the field of technology and research related to the application of solar cells for energy by converting solar energy (sunlight, including ultra violet radiation) directly into electricity. Due to the growing demand for clean sources of energy, the manufacture of solar cells and photovoltaic arrays has expanded dramatically in recent years.

Photovoltaic production has been doubling every 2 years, increasing by an average of 48 percent each year since 2002, making it the world’s fastest-growing energy technology. At the end of 2008, the cumulative global PV installations reached 15,200 megawatts, a 94% annual increase. Roughly 90% of this generating capacity consists of grid-tied electrical systems. Such installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building, known as Building Integrated Photovoltaics or BIPV for short.

Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries including Australia, Germany, Israel,[9] Japan, and the United States.

Solar thermal energy (STE) is a technology for harnessing solar energy for thermal energy (heat). Solar thermal collectors are defined are of three types.

• Low temperature collectors : are flat plates generally used to heat swimming pools.
• Medium-temperature collectors : are also usually flat plates but are used for creating hot water for residential and commercial use.
• High temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production.

STE is different from photovoltaics, which convert solar energy directly into electricity.

The solar power tower (also known as 'Central Tower' power plants or power towers) is a type of solar furnace using a tower to receive the focused sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target). Early designs used these focused rays to heat water, and used the resulting steam to power a turbine. However, designs using liquid sodium in place of water have been demonstrated; this is a metal with high heat capacity, which can be used to store the energy before using it to boil water to drive turbines. These designs allow power to be generated when the sun is not shining.