Venture capitalists are pouring hundreds of millions of dollars into [Silicon] Valley solar startups pursuing technological breakthroughs to make sun power as cheap as fossil fuel. Three of the largest tech IPOs of 2005 were for solar companies. The world's largest chip-equipment maker will begin producing machines to manufacture solar wafers, laying the groundwork for an industrial infrastructure that should lower the cost of producing solar cells. Solar energy has just the sort of oversize potential that the titans of tech saw in computing: a free and practically inexhaustible power source. California is also committing $3.2 billion to fund a drive to install solar panels on a million rooftops by 2018, and a November ballot initiative ... would tax Big Oil to provide $4 billion in funding for alternative-energy research, programs, and startups. Perhaps no startup has benefited more from the solar gold rush than Nanosolar. The Palo Alto company ... has racked up more than $100 million in funding so far. Nanosolar is pursuing a technology that produces solar cells on a film that's a 100th the thickness of conventional silicon wafers. Its ultimate goal: integrating thin-film cells directly into building materials. A skyscraper's glass windows, for instance, could be embedded with thin-film cells, giving them energy-producing capabilities. Nanosolar plans to build a manufacturing facility next year ... that will eventually produce 430 megawatts' worth of solar cells per year. That would nearly triple the nation's manufacturing capacity and make Nanosolar one of the world's largest solar producers. Thanks to aggressive government subsidies, Germany and Japan are currently the global leaders in solar production.