Solar power isn't just for your pocket calculators anymore. The sun is increasingly looking like a legitimate source of clean power, and harnessing its energy is becoming an ever-bigger business.

"Sure," you may be saying, "you're in San Francisco, of course you love solar." And while it's true that I'm currently a Californian, and we Golden Staters seem to dig solar, it's also true that we're not alone. Colorado, Hawaii, New Jersey, New Mexico, Nevada, and Pennsylvania are among the other states putting solar programs of one form or another on the books. Other countries, such as Germany and Japan, have made even greater moves in bringing solar power to the forefront.

Really renew
In the rush to find alternative energy sources, critics have questioned whether some of the alternatives have dark sides of their own. Ethanol, for example, is an extremely clean-burning fuel source; in the U.S., it's made primarily from the distillation of corn. Though the use of ethanol fuel itself causes very little pollution, many have objected to the amount of land that needed to produce significant amounts of ethanol, and the increased demand for corn it creates, raising prices for those who rely on corn as a food source.

Current solar technology, which uses photovoltaic (PV) cells primarily made from silicon to collect and convert the sun's energy, isn't without its own blemishes. The production of solar panels does have environmental costs, but once the panels are produced, they have a very long useful life of pollution-free energy generation.

Using green to make green
The business of making solar panels isn't new, though many of the companies benefiting from the recent interest in solar are. Two of the world's largest suppliers of PV cells are Japan-based Sharp and Kyocera (NYSE:KYO), both of which have plenty of experience in the solar game. In Germany, China, and the U.S., though, firms that were hardly an idea five years ago are now selling hundreds of millions of dollars' worth of PV cells.

Some companies, such as U.S. based Evergreen Solar (NASDAQ:ESLR), have yet to reach profitability as they try to stay on the cutting edge of technology. Many others, though, including China's Suntech Power (NYSE:STP) -- a Rule Breakers pick -- and Trina Solar (NYSE:TSL), as well as Germany's Q-Cells and SolarWorld, have done consistently profitable business in current-technology PV cells.

So this Valentine's Day, I'm skipping the pink candy hearts and heading straight for the green ones. I'm hoping that 10 years from now, a sunny day will also be an electrifying one.

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Fool contributor Matt Koppenheffer sees competition heating up in the PV market, but he still owns shares of Suntech Power. He does not own shares of any of the other companies mentioned. The Fool's disclosure policy always has a sunny outlook.