The Future of Renewable Energy
(for the full version visit: http://www.entrepreneur.com/slideshow/199728.html)

If you think it's all about solar and wind, think again.

The companies: Energy Solutions International and Green Revolution

The innovation: Kinetic energy adapters for gym equipment

What it does: Technically, nothing. It just sits there while you pedal furiously and go nowhere. But it does allow you to convert all that sweat and energy into, well, energy, as resistance from stationary bikes is converted into electricity and sent back to the gym's power grid.

How it makes money: "By being able to build a better mousetrap," says Chris Maddern of Energy Solutions International. "What you have to do is really be able to stay at the forefront of technology so that less energy is being wasted when it's transferred from the generating source to the consuming source. As you move on, your product has to become more and more efficient."

Where it's going: Maddern says his firm and Green Revolution are working on an initiative to create completely self-sustaining gyms where members could go online to keep track of how much energy they've produced and the resulting carbon offset.

Courtesy of Entrepreneur.com