When Green Energy is Blue Energy: Power From the Sea
Carnegie Corporation’s CETO takes a different approach to tapping wave power. It belongs to the category called heaving and pitching devices. Sited underwater—which keeps the units out-of-sight, out-of-mind for coastal dwellers, as well as protecting them from the violence of surface waves and storms—CETO consists of any number (the more, the more power) of buoys that move up and down and back and forth as waves pass over them.
As the CETO buoys move, the mechanical action is used to pump seawater ashore. The high-pressure stream of water can be directed at a turbine to spin the blades and generate electricity. Or it can be sent to a reverse osmosis desalination plant, which removes salt by driving water, at pressure, through special membranes which “filter” the salt. CETO can therefore be used to create power or fresh drinking water or both, in any ratio desired.
Carnegie has already deployed CETO units in Western Australia, proving the viability of the CETO concept. In addition to creating electricity and drinkable water—as if that wasn’t enough—Carnegie claims that CETO will function like an artificial reef, providing shelter and a home for marine life. Instead of disrupting the local ecology, it’s hoped that CETO installation will help it.
Other heaving and pitching devices include wave-riding devices. These are devices where the machine or generator itself rides the waves and turns the mechanical energy of its own motion into electrical energy. For example, Checkmate Sea Energy has developed the Anaconda. The Anaconda is aptly named—it resembles a giant rubber snake.
The Anaconda is a buoyant flexible tube. It will have some fluid (such as water) inside. As the Anaconda rides up and down on the waves, the motion pushes a “bulge” of fluid through the tube, to a turbine in the tail. The moving pulse of pressure turns the turbine blades, generating electricity.
Three advantages of the Anaconda are (1) like other wave installations, it’s scalable—want more power? add more Anacondas; (2) because it’s mostly rubber, it’s very resilient and, if damaged, cheap to repair; and (3) like other wave riders, since it moves with the waves rather than opposing them, it’s less likely to be damaged in the first place.