"All the world's energy could be achieved by solar many thousands of times over"Photovoltaics enables sunlight to be transformed directly into electrical power. Certain materials naturally release electrons when they are exposed to light, and these electrons can then be harnessed to produce an electric current.
Photovoltaic cells, also called solar cells, are made from the same semiconductor materials used in computer chips. All solar cells have at least two layers with a positive and negative charge. The electric field across the junction between the two layers causes electricity to flow when the semiconductor absorbs photons of light and releases electrons.
Electrical contacts attached to the front and back of the cell enable it to become part of an electrical circuit. Over 98 per cent of solar cells are made with silicon. These cells are quite brittle, so several cells are wired together and enclosed in a rugged, protective casing called a module or panel. A group of these modules is called an array.
Photovoltaic modules produce DC (Direct Current) electricity which can be converted to AC (Alternating Current). The amount of power produced is measured in watts (W), kilowatts (kW - thousands of watts) and megawatts (MW - millions of watts). The maximum power output of a photovoltaic array is typically expressed as kilowatts of peak capacity power (kWp) and power output over time is measured in kilowatt hours (kWh).
On earth, the amount of solar energy available to generate photovoltaic power is about 10,000 times greater than total world energy use today.1 Photovoltaics were first developed in the 1950s for space exploration, and terrestrial systems development begun in the early 1970s following the oil crisis.
Photovoltaics have a number of critical advantages:-
At the end of 1996, there was 600MW of solar photovoltaics installed around the world. In 1995, all the world’s solar photovoltaics generated 800 million kilowatt hours of electricity. The systems installed since 1988 are enough to generate electricity for 150,000 homes in the US.2
In 1995, the annual world-wide photovoltaics market was worth around $1.2 billion. The industry has grown 300 per cent since 1985. The scale of future progress of solar photovoltaics will be driven by:
Against the background of climate change and corporate responsibility of the oil industry, the first point is of crucial significance. Photovoltaics investments are dwarfed by a continuing focus on the exploitation of further oil reserves. Consequently, their relative influence has declined over the years. As industry analysts Strategies Unlimited note,"Of the 15 petroleum companies that have been involved in photovoltaic development or commercial ventures over the last several years, one remains in the US, three in Europe and two in Japan. Later industry participants appear to come largely from the electronic component and materials sector" 3 They also go on to say that "The point is that parental decisions on investment play a fundamental role in shaping the future of PV business direction. Corporate parent and government decisions can lead to rapid scale-up, limited market impact through lack of increased investment, or departures from the industry." 4
Production of photovoltaic modules has more than doubled in seven years. European production declined (-6.5 per cent) as US (+14.7 per cent) and Japanese (+29.3 per cent) markets increased. The European PV industry "continues to be adversely affected by cuts in Common Market expenditures for PV and R&D programs".7
One sign of how rapid progress can be achieved is that today a single building can increase the global market sales by over 1 per cent. The German company Pilkington will install 1MWp - 9,500m2 - the world’s largest solar electric roof on the Academy of Further Education of the Ministry of Interior of Northrhine-Westfalia in Herne, Germany this year. It will deliver up to 900,000 kWh of photovoltaic electricity.
1997 is being viewed as a turning point in the fortunes of solar photovoltaics as global demand is "poised to soar"8 Growth is projected at 15-30 per cent per annum. Conventional business-as-usual market forecasts to 2010 estimate 830MWp annual photovoltaic sales (including only 60MWp for on-grid central stations) resulting in world-wide sales of $8-10 billion.
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