Cheap solar energy a step closer

Posted: 1 January 2008

Author: Jeremy Hamand

A Californian company has perfected a technique for mass-producing photovoltaic (PV) solar energy cells on very thin metal sheet. New thin-film technologies have helped to boost the production of PV cells worldwide by 50 per cent in 2007.

The company, Nanosolar, produces its PowerSheet solar cells with printing-press-style machines which set down a layer of solar-absorbing nano-ink onto metal sheets as thin as aluminum foil, so the panels can be made for about a tenth of what current panels cost and at a rate of several hundred feet per minute.

Nanosolar Powersheet
Nanosolar Powersheet
Nanosolar Powersheet
With backing from Google's founders and $20 million from the US Department of Energy, Nanosolar's first commercial cells rolled off a production line in California in December, heralding what British scientists called "a revolution" in generating electricity.

Jeremy Leggett, chief executive of Britain's leading solar energy company, Solar Century, said that it would be "breathtaking" if the technology proved as efficient as projected by the company. "This is a revolution. But people are going to be amazed at other developments taking place in solar technologies. We will be thrilled if this technology is as efficient as the company says. It will not change the direction of solar power in itself. Spectacular improvements are also being made in other parts of the industry," he said.

Cost has always been one of solar's biggest problems. Traditional solar cells require silicon, and silicon is an expensive commodity (exacerbated currently by a global silicon shortage). What's more, says Peter Harrop, chairman of electronics consulting firm IDTechEx, "it has to be put on glass, so it's heavy, dangerous, expensive to ship and expensive to install because it has to be mounted." And up to 70 per cent of the silicon gets wasted in the manufacturing process. That means even the cheapest solar panels cost about $3 per watt of energy they go on to produce. To compete with coal, that figure has to shrink to just $1 per watt.

Nanosolar's cells use no silicon, and the company's manufacturing process allows it to create cells that are as efficient as most commercial cells for as little as 30 US cents a watt. The process is technically described as Copper indium gallium selenide (CIGS) photovoltaic technology, and its successful manufacture could revolutionise the economics of solar energy.

PV graph
PV graph
Nanosolar CEO Martin Roscheisen claims that once full production starts early in 2008, it will create 430 megawatts' worth of solar cells a year - more than the combined total of every other solar plant in the US. The first 100,000 cells will be shipped to Europe, where a consortium will be building a 1.4-megawatt solar power plant located on a former landfill owned by one of the largest waste management companies in Eastern Germany.

Figures released by the Earth Policy Institute in Washington showed that production of photovoltaics jumped to 3,800 megawatts worldwide in 2007, up an estimated 50 per cent over 2006. At the end of the year, according to preliminary data, cumulative global production stood at 12,400 megawatts, enough to power 2.4 million US homes. Growing by an impressive average of 48 per cent each year since 2002, PV production has been doubling every two years, making it the world's fastest-growing energy source.

The Nanosolar PowerSheet was named Top Innovation of 2007 by Popular Science magazine. To read how the new technology works, go here.