"Alternative energies are not just a pie-in-the-sky dream," says Paul Tracy and Nathan Slaughter from the StreetAuthority Market Advisor. "Denmark generates as much as 30% of its power from wind, Iceland uses geothermal energy, and producers are bringing down the cost of solar power."

"Overall, companies involved in alternative power technologies, such as wind, solar, geothermal, and biomass, are getting plenty of attention from investors these days." Here, the advisors profile what they consider to the most attractive companies in the alternative energy space.

Suntech Power Holdings Co. (NYSE: STP), "which manufactures and sells photovoltaic (PV) solar cells, has two primary advantages: a low manufacturing cost base and highly efficient cells.

"For starters, Suntech is based in China, where labor costs (even for skilled research staff) are far lower than in the Western world. The Chinese government also subsidizes such research, further helping companies like Suntech.

"In addition, the firm's cells boast some of the highest conversion rates on the market, allowing the company to offer smaller panels that can produce as much electricity as far larger ones from competitors.

"Suntech has been ramping up its manufacturing capacity rapidly in recent years to keep pace with strong demand. Analysts are forecasting robust earnings growth of 45% annually over the next five years.

"Zoltek Companies Inc. (NASDAQ: ZOLT) makes carbon fiber, a synthetic material that is both extraordinarily light and strong. Wind power represents Zoltek's largest and fastest growing market.

"Fiber blades because they're lighter and more efficient than metal or other materials. In fact, the company has been struggling to build out its manufacturing capacity quickly enough to meet demand. In the meantime, the firm has been signing key long-term supply arrangements with some of the world's largest wind power companies, like Gamesa of Spain and Vestas of Denmark.

"ZOLT shares are currently trading at 33 times next year's earnings -- a discount to the company's projected long-term growth rate of nearly +38%. As wind power continues to increase in popularity, ZOLT could extend its recent winning streak for years to come.

"Ormat Technologies Inc. (NYSE: ORA) is among the world's largest builders of geothermal power plants -- those using the Earth's own heat to produce clean, renewable power. The company's plants are installed in Hawaii, California, New Zealand, the Philippines, and Thailand, among other places.

"Geothermal power has been among the more successful and low-cost alternative energy sources in markets where sufficient geological heat is available. Ormat has a proven track record of building working geothermal plants all over the world, and that reputation gives the firm a key competitive advantage.

"The company's technology is field-tested and reliable, and its plants are backed up by several patents. That impressive track record makes it easier for the firm to win contracts to build new plants.

"Even better, Ormat actually owns a dozen of its own geothermal plants and has another half dozen under construction at this time. This should provide a steady stream of recurring revenues. With this in mind, Ormat is one of our favorite pure-play alternative energy stocks."

Each day, Steven Halpern's TheStockAdvisors.com features the latest investment commentary and favorite stocks of the nation's leading financial newsletter advisors.