Solar energy

We still use solar power in the same two forms today, thermal and photovoltaic. The first concentrates sunlight, converts it into heat, and applies it to a steam generator or engine to warm buildings, heat water, generate electricity. Electricity is generated when the heated fluid drives turbines or other machinery. The second form of solar power produces electricity directly without moving parts. Today's photovoltaic system is composed of cells made of silicon, the second most abundant element in the earth's crust. Power is produced when sunlight strikes the semiconductor material and creates an electric current. The smallest unit of the system is a cell. Cells wired together form a module, and modules wired together form a panel. A group of panels is called an array, and several arrays form an array field.

There are several advantages of photovoltaic solar power that make it one of the most promising renewable energy sources in the world. It is non-polluting, has no moving parts that could break down, requires little maintenance and no supervision, and has a life of 20-30 years with low running costs. It is especially unique because no large-scale installation is required. Remote areas can easily produce their own supply of electricity by constructing small or large systems. As communities grow, more solar energy capacity can be added, allowing power generation to keep in step with growing needs without having to overbuild generation capacity as is often the case with conventional large scale power systems.

Solar energy is most sought today in developing countries. India is becoming one of the world's main producers of PV modules, with plans to power 100,000 villages and install solar-powered telephones in its 500,000 villages. By 2000, Mexico plans to have electrified 60,000 villages with solar power. Probably the most outstanding example of a country's commitment to solar power is in Israel. In 1992, over half of all households (700,000) heated their water with solar energy systems. And there are 50,000 new installations every year.

An average home has enough roof area to produce solar electricity to supply all of its power needs. With an inverter, which converts direct current (DC) power from the solar cells to alternating current (AC), a solar home can look and operate very much like a home that is connected to a power line.

Household energy supply is but one use of solar power. Roadside call boxes and lighted highway signs rely on the sun's energy. Navigational systems such as marine buoys and other unmanned installations in harsh remote areas are also ideal applications for solar power. Rural habitation includes "cabins, homes, villages, clinics, schools, farms, as well as individually powered lights and small appliances." Consumer/indoor uses of PV cells include watches and calculators; PV modules power computers and radios.