Solar Power

The sun produces a nearly constant flow of energy. Solar radiation provides a huge amount of energy to the earth. The total amount of energy that is irradiated from the sun to the earth's surface equals approximately 10,000 times the annual global energy consumption. There are two main types of technologies to "harvest" the sun's energy: concentrated solar power and photovoltaics.

Concentrated Solar Power ("CSP"): the sun's rays have to fall on a relatively large area for enough heat to be collected for conversion to electricity; a concentrating collector is used to focus the rays on to a much smaller area, usually sun-tracking mirrors. The final steps of generating electricity using CSP systems are similar to conventional electricity generation: steam or hot gas is produced by the concentrated solar radiation, and then used to rotate turbines. CSP technologies have been constructed in various sizes, from small multi-kW systems, to large power stations of several MW. These power stations have provided the cheapest electricity to be generated using solar power. Commercial CSP project developments are pursued with varying progress in more than a dozen sunbelt countries, including Australia, Brazil, Egypt, Greece, India, Iran, Israel, Italy, Jordan, Mexico, Morocco, South Africa, Spain and the US. There are currently only 360 MW of installed CSP capacity world-wide, but since this technology is competitive when fossil fuel prices are high, it is expected that capacity will reach 1,000 MW before 2006.

Photovoltaics ("PV"): solar energy can also be converted into electricity by means of a photovoltaic cell. "Photo" refers to light and "voltaic" to voltage. The term describes a solid-state electronic cell that produces direct current electrical energy from the radiant energy of the sun. Photovoltaics make use of diffuse solar radiation as well as direct sunlight, therefore making the technology suitable also for temperate climates. The greater the available solar resource, the greater the electricity generation potential. Photovoltaic cells are made of semi-conducting material, most commonly silicon, coated with special additives. The electricity generated may be used for lighting and appliances, stored in batteries, or in a one-person automobile.

One criticism of early PV modules was that they consumed more energy during their production than they generated during their lifetime, but this is no longer true. Typically, energy payback is realised within three to four years. A new technology, known as thin film cells, offers potential for cost reductions, thanks to reduced material and labour costs.

Japan (650 MW, or 5W/capita), Germany (280 MW, or 3.4 W/capita) and the US (215 MW, or 0.75 W/capita) are the world leaders in photovoltaics. World-wide capacity has recently been growing at rates between 20 and 40% per year, and has now reached more than 1,300 MW, with Japan and Germany accounting for most of the growth. In all cases, growth continues to be driven by government or utility supported programmes. Indeed, at today's prices for photovoltaic electricity compared to electricity produced by traditional fossil fuels, installing a grid-connected photovoltaic system (even with a significant subsidy) will not provide a commercial return, and this is not likely to change in the short-term. Nevertheless, in places where the electricity grid is not available, stand-alone (off-grid) photovoltaic power systems are cost competitive.