Ten Eco-Friendly Companies

Their path to the solar-power business took some surprising turns. The duo was developing telecom equipment when the industry collapsed in 2001. They liquidated the company, but Pearce spent $1.5 million of his own money to buy some of the company's assets at auction. They included a machine that put magnetic memory strips onto credit cards. Hollars, a physicist, converted it to make thin-film solar cells.

The copper-alloy technology, called CIGS, has been tested in corporate and government labs for years. But Miasole's quick mastery made the company a hot property. Earlier this year the venture-capital firm that backed Google, Kleiner, Perkins, Caufield & Byers, led a $16 million investment round. Miasole's panels will be less than 50-microns thin--four times thinner than a photovoltaic. Conventional cells are slightly more efficient, but Pearce counsels patience. "They have a 50-year head start," he says.

--Brad Stone

3 Harnessing Hydrogen

Hydrogenics: Building markets for fuel-cell tech. A big bonus: byproducts can quench a thirst.

Pierre Rivard compares critics of hydrogen power to those who could never fathom color television, portable phones or the Internet. "They just lack vision," says Rivard, cofounder of Hydrogenics, an Ontario-based company. "People couldn't have imagined the advances we have made years ago."