Photoelectric, light electric, or solar electric. Principal was discovered by the French physicist Edmund Becquerel in 1839; interestingly one of his relatives discovered the principal of atomic energy some years later. So PV predates nuclear power! It was not until scientists at Bell Labs in 1954 were working on silicon rectifiers (diodes) that the real potential of PV started to become clear. The space race of the late 50's forward gave PV's a niche that they have filled ever since. Because space has unlimited sunlight and PV's are autonomous power sources and are lightweight they have powered all satellites, from the tiny Vanguard to the very large Skylab. Unfortunately the government spent very little on research and development to make better and cheaper PV's, though it spent billions to develop nuclear power.

In 1955 Western Electric began to sell commercial licenses for silicon PV technologies; early successful products included PV-powered dollar bill changers and devices that decoded computer punch cards and tape. Bell System's demonstration of the type P rural carrier system began in Americus, Georgia. Hoffman Electronics's Semiconductor Division announced a commercial PV product at 2% efficiency; priced at $25/cell and at 14 mW each, the cost of energy was $1500/W.

In 1959 Hoffman Electronics achieved 10% efficient, commercially available PV cells and demonstrated the use of a grid contact to significantly reduce series resistance. Explorer-6 was launched with a PV array of 9600 cells, each only 1 cm x 2 cm.

In 1963 Japan installed a 242W PV array on a lighthouse, the world's largest array at that time.

In 1977 The Solar Energy Research Institute (SERI), later to become the National Renewable Energy Laboratory (NREL), opened in Golden, Colorado. Total PV manufacturing production exceeded 500 kW.

In 1982 Worldwide PV production exceeded 9.3 MW. Solarex dedicated its 'PV Breeder' production facility in Frederick, Maryland, with its roof-integrated 200-kW array. ARCO Solar's Hisperia, California, 1-MW PV plant went on line with modules on 108 dual-axis trackers.

In 1985 solar cell conversion efficiency of over 20% achieved.

In 2001 experimental PV-powered airplane Helios reached 30 km altitude.

In 2004 covering a total of 62 acres (equivalent to 56 football fields) and using 57,600 solar panels the 10MW project in Germany’s Bavaria Solarpark is the largest photovoltaic project in the world.

PV cell is a device that converts sunlight directly into electricity. When illuminated, the PV cell produces a voltage between front and back. This voltage is developed across a junction that is built into the cell structure. This voltage can be used to produce a current, just like from a battery, but the amount of current is limited by the amount of light falling on the cell and it’s efficiency.

Solar photovoltaic (PV) panels have no moving parts, are easy to install, require little maintenance, contain no fluids, consume no fuels, produce no pollution, and have a long life span. The main areas of environmental concern are in cell and module (modules are groups of cells connected together) production and disposal. Cell and module manufacturing require the use of a variety of hazardous chemicals. (The computer chip and circuit board industries use many of the same chemicals.) Most PV cells produced today are made mostly of non-toxic silicon. However, there are cells made of compounds containing toxic elements such as cadmium. The amount of cadmium in this type of PV cell or module is very small. The cadmium is also encapsulated in the PV module, so that unless the module is broken, there is no health risk. Cadmium is a by-product of the zinc mining industry, and it usually ends up in slagheaps or in NiCd batteries, many of which eventually end up in landfills. PV modules seal the cadmium for the life of the module (20-30 years), at which time the cadmium can be recycled. Recycling or proper disposal of these cells/modules is necessary to reduce potential environmental problems.

Producing the materials in PV cells/modules (silicon, aluminum, glass, and encapsulants) is very energy intensive. Estimates of the energy payback (the number of years it takes for the amount of energy a PV module is capable of producing to equal the amount of energy it takes to produce the module) range from six months to 10 years. The location where a PV module/array is installed largely determines the payback period: the more sun the system receives and converts to electricity, the quicker the energy payback. Technical advances in the efficiency of cell/module manufacturing and cell power conversion, as well as in the processes to produce the cell/module materials, will reduce the payback period. One solar cell manufacturer supplies some of the energy for its facility from an array of PV modules.

Environmental benefits

Reduces local air pollution
Use of solar electric systems decreases the amount of local air pollution. With a decrease in the amount of kerosene used for lighting, there is a corresponding reduction in the amount of local pollution produced. Solar rural electrification also decreases the amount of electricity needed from small diesel generators.

Offsets greenhouse gases
Photovoltaic systems produce electric power with no carbon dioxide (CO2) emissions. Carbon emission offset is calculated at approximately 6 tons of CO2 over the twenty-year life of one PV system.

Conserves energy
Solar electricity for the Third World is an effective energy conservation program because it conserves costly conventional power for urban areas, town market centers, and industrial and commercial uses, leaving decentralized PV-generated power to provide the lighting and basic electrical needs of the majority of the developing world's rural populations.

Reduces need for dry-cell battery disposal
Small dry-cell batteries for flashlights and radios are used throughout the un-electrified world. Most of these batteries are disposable lead-acid cells which are not recycled. Lead from disposed dry-cells leaches into the ground, contaminating the soil and water. Solar rural electrification dramatically decreases the need for disposable dry-cell batteries.