Solar power has been the Next Big Thing for as long as most people have been alive. Way back in the 1970s, the idea of using clean, abundant, free sunlight to break the grip of Big Oil first led homeowners to bolt solar panels onto their roofs and wait gleefully for their meters to start running backward, and they've been at it ever since. Unfortunately, almost without exception, those early solar arrays ended up serving only the social consciences of their owners. Sunshine may have been free, but solar power was anything but. Until very recently, solar panels were so inefficient that they cost more than they saved, which is why, despite all that free sunlight, they currently adorn only a relative handful of U.S. homes.

But during solar's long gestation period, researchers were making steady progress. Each year, the ability to turn sunlight into energy improved. And now, at last, solar is ready for prime time. How ready? Well, with a little help from improved energy storage technology, solar power will soon be able to literally replace the entire fossil fuel infrastructure in the world's sunnier climes. It is, in short, going to be huge beyond words.

Solar power comes in two versions:

1. Photovoltaics, which includes both the familiar rooftop solar panel and its more exotic thin-film descendents. Click to learn more about Photovoltaics.

2. Solar thermal, one of those old-is-new-again ideas that suddenly looks like a viable alternative to coal-burning power plants. Click to learn more about Solar Thermal.