The Motion of the Ocean

What is electricity? Sure, there are plenty of ways to define this force in terms of charge or current or the interaction of particles, but unless you’ve got a solid background in physics, it’s hard to really get a handle on exactly what that means.

So here’s an interesting way to think of electricity: it’s a way to harness, store, transport and use the energy originally created by something in motion. That’s what generators do -- they turn kinetic energy into electricity. Everything starts with motion.

This is easy to see with hydroelectric power, which uses the motion of water flowing through a dam to turn a rotor; when the rotor spins inside a magnetic field, electricity is produced. But most people don’t realize that the same concept is at work in other power plants. Coal, wind and portable generators all work the same way. A lot of people don’t understand that nuclear plants are just fancy steam engines; they think it uses some kind of advanced super-scientific principle to get juice flowing directly out atoms, but in fact it uses a controlled fission reaction to release heat, which boils water. The resulting steam is used to drive a rotating turbine, which produces electricity.

So where can we find a nearly limitless source of motion? The ocean, of course. In the past week, I’ve seen two great ideas for transforming the kinetic energy of the tides and waves into electricity.

The first uses power buoys, tethered to the ocean floor. Inside the buoy, a coil of metal is attached to the tether, so it cannot rise or fall with the waves. This is surrounded by a sheath of magnets that is not tied down, and does move up and down around the coil with the tides. This motion creates electricity.

The government has approved at least four proposals to test the concept, all in Oregon.

The second idea is even more out there. It uses something called a “dielectric elastomer,” which is a fancy way of saying a high-tech, stretchy piece of plastic. Scientists know that some elastomers contract when power runs through them. Well, it turns out the process can work in reverse. Stretch out an elastomer, and it will kick out electricity.

Researchers are trying to turn this concept into a commercial power reality, using waves and tides to stretch out the elastomer. Just tie one end to the sea floor and the other to a floating buoy, and the waves will move them around all day long.

Neither idea is close to reality; one of the problems is that wind and salt water don’t mix well with power generators. Another, like offshore wind farms, is NIMBY politics. Still, this is such an elegant idea that I can’t help but hope that somebody will make it work.