Truly 'Alternative' Energy Stocks That Could Shine

Among the problems, he says, is that corn is a pretty inefficient way of making ethanol. And there are a lot of logistics involved in getting it from where the corn grows to where the fuel is needed. "A lot of people rushing into the ethanol 'space' haven't thought it through," he says.

Solar power has a different problem. Eventually, it's going to be one of our major energy sources, Robinson predicts. "But it's not yet economic, and I think a lot of the valuations in this space have been inflated. You need to be careful there."

The really big problem right now, he argues, is that the essential ingredient for solar paneling is silicon. And there is a worldwide shortage of silicon. That means some of these companies can't get access to the silicon they need to grow the business. The rest will have to pay up for it. And that will make their products even less economical.

So where is Robinson putting his investors' money? His biggest tip is geothermal energy. It doesn't sound sexy, but it has three big advantages. First, it already makes economic sense, even if oil falls to $40 a barrel. Second, there are some great plays right here in the U.S. And third, hardly anyone is talking about it on Wall Street, so those stocks look pretty cheap.