Today, many are smaller and more efficient, but they can still be expensive and impractical. Many of the purest plays in alternative energy do have considerable investment problems. Consider Vestas Wind Systems, one of the world's largest windmill makers. Vestas is a Danish company, and its stock isn't traded here. At Fidelity Brokerage, for example, you'll have to call a customer representative to buy 100 shares for you.
Fuel cells are another part of the alternative energy equation.
These convert fuel to energy without combustion and are cleaner and more efficient than generators that burn fuel. Several companies make fuel cells. Not the technology. But Plug Power and Proton are both very thinly traded, which means very small purchases or sales can affect their prices dramatically. Plug Power, for example, trades about 539,000 shares a day, which isn't much by Wall Street standards.