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Electricity generation

Electricity can be generated from the sun in several ways. Photovoltaics (PV) has been mainly developed for small and medium-sized applications, from the calculator powered by a single solar cell to the PV power plant. For large-scale generation, concentrating solar thermal power plants have been more common but new multi-megawatt PV plants have been built recently. Other solar electrical generation technologies are still at the experimental stage.

Photovoltaics

A solar cell

A solar cell or photovoltaic cell is a device that converts light into electricity using the photoelectric effect. The first working solar cells were constructed by Charles Fritts in 1883. These prototype cells were made of selenium and achieved efficiencies around one percent. Following the fundamental work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created a solar cell made of silicon in 1954.

residential building with solar panels on one side (Bern, Switzerland).

In 1958, photovoltaic modules were used successfully as a power source for the Vanguard I satellite. This example was followed by many other Soviet and American satellites, so that by the late 1960s PV had become the established source of power for satellites. It played an essential part in the success of early commercial satellites such as Telstar and Syncom.
For terrestrial applications the cost of PV was the main limiting factor. It remained above $100 per watt throughout the 1960s. However, work by Elliot Berman during the early 1970s lowered the cost to $20 per watt and this price reduction made PV generation competitive in a range of applications, especially in remote areas without connection to a power grid. Uses included cathodic protection of pipelines and power for off-shore oil rigs, railroad crossings and lighthouses.

The International Space Station in 2001 showing solar panels.

The 1973 oil and 1979 energy crises provided a further impetus to PV development. A search for alternatives to oil resulted in incentive programs such as the Federal Photovoltaic Utilization Program in the USA and the Sunshine Program in Japan. Research facilities were established such as the Solar Energy Research Institute (now NREL) in the USA, the New Energy and Industrial Technology Development Organization (NEDO) in Japan, and the Fraunhofer Institute for Solar Energy Systems ISE in Germany.

A solar sculpture in front of Zwickau University of Applied Sciences pays tribute to this energy technology.When oil prices began to fall in the early 1980s the growth of PV was slowed. In the context of historically-low oil prices from 1986-1999, funding for PV research was relatively low and the issue was not high in public consciousness.Nevertheless, the output of PV-generated electricity grew by 10 to 20 percent per year throughout the 1980s and 1990s. By 1999, the worldwide capacity of PV had reached 1000 MW.

Total of installed PV is around 6,000 MWp (Mega-watt-peak) as of the end of 2006. It is projected to reach more than 9,000 MWp by the end of 2007.

With many jurisdictions now giving tax and rebate incentives, PV installations can pay for themselves in five to ten years in many places. "Grid-connected" systems - those systems that use an inverter to connect to the utility grid instead of relying on batteries - now make up the largest part of the market. While the deployment of PV power depends largely upon local conditions and requirements, most countries are taking an interest in developing PV as one of their options for renewable energy supply.