Solar photovoltaic (PV) systems convert solar energy directly into electrical energy. Basic conversion device used is known as a solar photovoltaic cell or a solar cell. A solar cell is basically an electrical current source, driven by a flux of radiation. Solar cells were first produced in 1954 and were rapidly developed to provide power for space satellites based on semiconductor electronics technology. Its terrestrial applications were considered seriously only after oil crisis of 1973 when a real need of alternative energy sources was felt globally for the first time. Efficient power utilization depends not only on efficient generation in the cell, but also on the dynamic load matching in the external circuit.

Solar cell is the most expensive component in a solar PV system (about 60 per cent of the total system cost) though its cost is falling slowly. Commercial photocells may have efficiencies in the range of 10–20 per cent and can approximately produce an electrical energy of about 1 kWh per sq. m per day in ordinary sunshine. Typically, it produces a potential difference of about 0.5 V and a current density of about 200 A per sq. m. of cell area in full solar radiation of 1 kW per sq-m. A typical commercial cell of 100 sq-cm area–thus produces a current of 2A. It has a life span more than about 20 years.

Major uses of photovoltaics have been in space satellites, remote radio communication booster stations and marine warning lights. These are also increasingly being used for lighting, water pumping and medical refrigeration in remote areas especially in developing countries. Solar powered vehicles and battery charging are some of the recent interesting applications of solar PV power. Major advantages of solar PV systems over conventional power systems are:

• It converts solar energy directly into electrical energy without going through thermal-mechanical link. It has no moving parts.
• Solar PV systems are reliable, modular, durable and generally maintenance free.
• These systems are quiet, compatible with almost all environments, respond instantaneously to solar radiation and have an expected life span of 20 years or more.
• It can be located at the place of use and hence no or minimum distribution network is required, as it is universally available.

It also suffers from some disadvantages such as:

• At present the costs of solar cells are high, making them economically uncompetitive with other conventional power sources.
• The efficiency of solar cells is low. As solar radiation density is also low, large area of solar cell modules are required to generate sufficient useful power.

As solar energy is intermittent, some kind of electrical energy storage is required, to ensure the availability of power in absence of sun. This makes the whole system more expensive.