The Economist.com: "Powering up" - Improved devices may make better use of sunlight

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"Powering up" - Improved devices may make better use of sunlight

MOST of the power generated by mankind originates from the sun. It was sunlight that nurtured the early life that became today's oil, gas and coal. It is the solar heating of the Earth's atmosphere and oceans that fuels wave power, wind farms and hydroelectric schemes. But using the sun's energy directly to generate power is rare. Solar cells account for less than 1% of the world's electricity production. Recent technological improvements, however, may boost this figure. The root of the problem is that most commercial solar cells are made from silicon, and silicon is expensive. Cells can be made from other, cheaper materials, but these are not as efficient as those made from silicon.

Kwanghee Lee of Pusan National University, in South Korea, and Alan Heeger of the University of California, Santa Barbara, work on solar cells made of electrically conductive plastics. They found that by adding titanium oxide to such a cell and then baking it in an oven, they could increase the efficiency with which it converted solar energy into electricity.A second approach, taken by Michael Grätzel of the Swiss Federal Institute of Technology, is to copy nature. Plants absorb solar energy during photosynthesis. They use it to split water into hydrogen ions, electrons and oxygen. The electrons released by this reaction are taken up by carrier molecules and then passed along a chain of such molecules before being used to power the chemical reactions that ultimately make sugar.The third technique, being developed by Prashant Kamat of the University of Notre Dame, Indiana, and his colleagues, uses that fashionable scientific tool, the carbon nanotube. This is a cylinder composed solely of carbon atoms, and one of its properties is good electrical conductivity. In effect, nanotubes act as wires a few billionths of a metre in diameter.

" When the price comes down to produce energy from sunlight because efficient cells are made from cheap materials, the energy supply and demand picture could change quickly. The rest of the world would then be able to join the poor of Africa and the rich of Europe and America, and generate inexpensive solar power for itself."