Image: www.solfocus.com
This article was originally seen in the Fall/Winter 2007 issue of Green Living Magazine. View the original article (pdf).
In theory, solar power is ideal. It’s clean, producing no air pollution or green house gases. It doesn’t require flooding huge areas or disrupting river ecosystems, as hydro power often does. And it’s plentiful: in just one hour, enough sunlight falls on the earth to supply the energy needs of everyone on the planet for an entire year.
But it has always been something of a black sheep in the clean-energy family. It can be expensive: a full set of panels for your home can cost tens of thousands of dollars and it isn’t considered very efficient. With typical solar panels, only about 15 percent of the energy that falls on them is converted into electricity (wind turbines average more than 20 percent efficiency, and coal-powered plants 30 percent or more). So while wind farms are sprouting up all over Europe, biofuels are on the rise and hydro is a Canadian staple, affordable solar power has seemed relatively inaccessible. But that’s changing. Engineers are creating new technologies that are not only cheaper but also more efficient than traditional flat panels, bringing us closer to the solar Holy Grail: producing electricity for the same price as fossil fuels.
Cutting the silicon costs
One of the biggest obstacles to solar power has always been cost. Silicon, used as a semiconductor to create electricity, is expensive and the global shortage of polysilicon -- the kind used in most solar panels -- isn’t making it any cheaper. So scientists are thinking of clever ways to do more with less of it. One way to get more bang for your buck is to stack solar cells on top of each other, creating what’s called a triple-junction cell. By layering three semiconductors, each capturing a different kind of light (blue, green or red), you can produce more electricity over the same area.
Michigan-based united Solar Ovonic has products we can buy for our homes and/businesses that use triple-junction technology and only a small amount of silicon. Moreover, the solar cells can be mounted onto stainless-steel foil (as opposed to glass) and are virtually unbreakable. It manufactures solar roof shingles, solar battery-chargers that come in sheets that can be neatly folded up, and peel-and-stick laminates that can be stuck onto a metal roof of, say, a shed or warehouse. They are understandably popular. Last year, united sold enough units to power more than 15,000 homes.
Another simple and elegant method is to focus sunlight with lenses and mirrors. Solfocus, a California-based company, has combined mirrors with triple-junction techniques. The curved mirrors in its solar panels concentrate the sunlight by 500 times. And by focusing the already concentrated sunlight onto triple-junction cells that don’t use silicon, Solfocus reduces the amount of semiconductor needed by a factor of a thousand to produce the same amount of electricity. The company is working on its first commercial installation in Spain, and expects to have finished products for the commercial market by late this year.
Prism Solar Technologies, based in New York State, has come up with a colourful way to focus sunlight: holograms. Its solar panels use a form of gelatin sandwiched between panes of glass to create a holographic effect. They aren’t just pretty-- they require 20 to 70 percent less silicon than a conventional panel. “We’ve basically displaced much of the expensive component and replaced it with an inexpensive gelatin material -- essentially a high-tech Jell-O --and it’s a great way to concentrate sunlight in low light conditions, such as late afternoon,” says Prism Solar CEO Rick Lewandowski. Canadians should be able to buy these rainbow-coloured panels to install on the roofs of our homes by 2008.
Keep reading more about solar power in Part two: Solar energy is the hot power source.
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