When Green Energy is Blue Energy: Power From the Sea
While there are many engineering issues remaining—How best to anchor the units? What size, type, and number of turbines is optimal for power generation? How to protect sea life from the spinning turbine blades?—in many ways, ocean current turbines are the most conventional type of ocean power technology. They’re simply underwater windmills, or hydroelectric turbines without the comfort of a channel.
Riding the Wave: Wave Energy
Ocean current turbines may be very conceptually simple, but some of the most fully developed ocean power technologies are based on tapping the enormous power inherent in ocean waves. And just as there are many different types of ocean waves, there are many different types of generation technology designed to capture their power, but they all share a fundamental three-part process, in which:
- waves move something, either directly or through air that is itself “pumped” by waves
- sometimes that something is the whole device, floating on the water and riding the waves; other times, it’s a part of a larger installation fixed to the sea floor or shore
- that movement generates power
Beyond these basics, wave devices can differ greatly.
An oscillating water column (OWC) doesn’t tap the power of the waves directly—instead, it taps the power of air moved by ocean waves. A cylinder is anchored on the seabed near shore; as waves roll past it, the water level in the cylinder alternately rises and falls. As it rises, it increases the air pressure within the cylinder (the air is “squeezed” by the water); as it falls, a partial vacuum is created, depressurizing the air. This in turn causes the air within the chamber to blow, moving one way on pressurization, the other on depressurization. The moving air turns a special turbine, one that is designed to spin the same way no matter which way the “wind” blows. This turbine then generates electricity.
Waves power the turbine in an oscillating water column. (image: rise.org.au)
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