A new sort of solar panel is less fussy about where the sun shines from
SOLAR power should be a cheap and simple way of making electricity, but like any technology the practicalities tend to get in the way. Even if the sun does come out the panels may not face in the right direction. Then there is the cost, which can exceed $40,000 for a household system—more than half of which is accounted for by installation. This week, however, a Californian company launched a new type of solar panel that tries to overcome these problems.
Standard solar panels are assembled from arrays of photovoltaic cells made from silicon, like computer chips. These cells absorb photons in light and transfer their energy to electrons, which form an electrical circuit.
Solyndra, based in Fremont, is taking a different approach. It is one of a number of firms, including First Solar, Nanosolar and Global Solar, using different materials to produce the photovoltaic effect and building them in extremely thin layers, almost like printing on paper. As these films use less material they are cheaper to produce, not least because they can be deposited on bases like metal, glass and plastic.
The most effective material for thin-film photovoltaics so far is copper indium gallium selenide (known as CIGS). Although it is not quite as efficient at converting sunlight into electricity as silicon is, its low cost and flexibility provide other advantages.
Solyndra's approach is to coat glass tubes with CIGS and encase them in another glass tube with sealed ends. They look a bit like fluorescent-lighting tubes. Forty of these tubes are then assembled into a single panel. Using tubes instead of flat panels makes it possible to capture sunlight, including diffuse light, from any direction—even if it is reflected up from a roof. And whereas traditional solar panels have to be tilted and carefully positioned so as not to shade nearby panels, tubular ones can be laid flat over the entire roof. Being lightweight and open they are also less prone to being blown away. This makes them easier and faster to fit. The cost of installation, reckons the company, should be about half that of conventional panels.
Solyndra is chasing the market for commercial rooftops: factories, warehouses and supermarkets. Chris Gronet, the company's chief executive, says that with some 30 billion square feet of large flat roofs in the United States alone, tubular solar cells could generate 150 gigawatts of electricity. That would be enough to power almost 16m homes.
This article appeared in the Science & technology section of the print edition under the headline "Tubular sunshine"
From the October 11th 2008 edition
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