When most people think of renewable energy, they think of hydro, or solar, or wind, or (increasingly) biomass. A few people think of geothermal. But that’s pretty much the list of renewables.

The most forgotten form of renewable energy, and one which I think holds more long-term promise than any other, is ocean-based energy.

The amount of energy that can be found in the ocean — thermal gradients, waves, tides, currents — is enormous, many times the amount required by the human species. As long as we have a sun and a moon (and when we don’t, we’ll have much bigger worries), then the ocean will contain a gargantuan amount of energy. And, it’s always there, day or night, almost completely predictable, unlike many other forms of renewables.

Of course, the challenge is to harness this energy in an economically viable fashion, and without causing adverse effects on marine life, aesthetics, shipping traffic, and so on. Scientists and engineers have been working on various technical approaches to capturing ocean energy for over two decades, and a lot of work remains to reach commercial viability. But, I believe that at least one of these technical approaches will eventually pay off in the next decade or so, and a big payoff it will be.

Believe it or not, unlike the masses and even energy industry experts, the Energy Policy Act of 2005 didn’t forget ocean energy technologies, including provisions for mandatory purchase requirements from ocean energy sources.

How did legislators manage to include ocean energy when everyone else had been overlooking it? Amazingly, it seems to have been because the companies in the ocean energy field — almost all early-stage privately-held companies, no big firms that you might have heard of — came together of their own volition to form the Ocean Renewable Energy Coalition. Web site Bully for them.

Let’s keep our eyes on ocean energy. I’m looking for much bigger things from the ocean in the future. It won’t remain forgotten for long.