The future, according to MiaSole, a Cali-fornian start-up, is unrolling at one centimetre a second in a bland-looking building in Silicon Valley. Despite the location, and the fact that most other solar cells are made from silicon, MiaSole's cells are not. Ribbons of steel a metre wide and half a hair's width thick spool through vacuum chambers in which they are sputtered with copper, indium, gallium and selenium-collectively known as cigs. Out of the end comes a new type of solar cell which promises to be both efficient and cheap. MiaSole's current cells turn 10.5% of the light that hits them into electricity.
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