There are a number of ways to harness the energy of oceans, from simple tidal generators to more complex tidal barrages. Some researchers are even imitating Nature to come up with new designs.
All derive their power from the kinetic energy of moving water, just as wind turbines derive theirs from moving air. Ocean energy is more efficient than wind or solar power simply because of the higher density of water, and the regularity of ocean waves, provides more power in a consistently reliable fashion than either wind or sun. Because water weighs more, it generates more kinetic energy, allowing tidal generators to be smaller and less obtrusive than wind turbines even at the same power rating.
Where a tidal generator might consist of a single turbine, a barrage is usually composed of many turbines placed along a natural or artificial barrier, like islands or a dam (or a breakwater), where the differential pressure on the “downside” of the barrier provides the greatest hydrokinetic energy.
If you’re interested in learning more, check out the tidal generators on the Rance River in France, in Canada’s Bay of Fundy (scheduled to begin producing power next year), and Kislaya Guba, in Russia.
Location is the most important factor in tidal turbines, or turbine arrays, and they are best located where water is constricted. Tidal barrages rely on the differential between high and low tides, cost a lot and have numerous environmental impacts. Deepwater installations of newer technologies based on biomimicry – while initially more complicated – face the fewest hazards from shipping, but near-shore installations are easier to service and connect to power grids.
Not all systems resemble turbines, and the newest kids on the block look more like deep-sea snakes, water-filled windsocks or fish tails. Physicists Francis Farley and Rod Rainey of Atkins Global (trading on the London Stock Exchange, ATK) have invented a long, flexible tube they call the Anaconda. Filled with seawater, the device could produce more energy than a turbine and would be cheaper to maintain because it doesn’t rust, rot or get damaged by its own resistance to water like a metal structure does.
The Anaconda, placed in depths between 130 and 320 feet, is compressed by the passage of the waves around it. When this bulge reaches the end of the sealed tube, it powers a turbine. Full-sized versions will be about 20 feet across, 600 feet long, and can potentially produce enough energy to power about 2,000 homes. Fine-tuning this energy snake to deliver maximum power involves determining the best ratios of width to length, the tube’s flexibility, and the thickness of the membrane.
Even more conceptually complicated are the technologies coming out of Australia’s BioPower Systems, a private company which reportedly harnesses the power of oceans using the above-mentioned biomimicry. By imitating the motions of fish and underwater plants, BioPower has developed two novel power systems. The bioWAVE pilot project, on King Island in Tasmania, looks like three hyper-inflated seaweed pods, which apparently lie down like well-trained dogs when ocean waves get boisterous. The bioSTREAM pilot, a Thunniform model based on shark fins and now being tested off Flinders Island (Tasmania), operates on resistance and can “go with the flow": to prevent being damaged by extreme oscillations in tides such as might occur during a storm.
With more than half the people in the world living within 125 miles of an ocean – a figure rising exponentially since the early 70s – harnessing the power of oceans makes a great deal of sense, both economically and aesthetically. Unlike oceangoing wind projects like Cape Wind – which has drawn the wrath of such notables as the Kennedy family – most ocean-centric power projects are virtually invisible, do not harm birds or bats, and provide constant, reliable power where both wind and solar energy do not.
The effects of tidal power on fish and ocean-going mammals are still being investigated, but pilot projects indicate that careful placement can mitigate the inherent dangers. In fact, at this point, overfishing is more of a threat to marine populations than proposed tidal generation. If projects are initiated, they may also necessitate creating ocean preserves, or ship-free corridors, to protect equipment. These no-trespassing zones will also, albeit unintentionally, protect fish stocks and marine mammals.
So far, the U.S. has not established a hydrokinetic testing facility like the UK’s testing grounds off the Orkney Islands in Scotland. The Makah Bay facility, off the coast of Washington, has been approved by FERC (the Federal Energy Regulatory Commission) but faces opposition from environmental activists, a lack of financing and political indifference. H.R. 2313, proposed in 2007 and costing American families a mere $2 per year, died a quiet death in the House. A substitute and poorly funded measure was tacked on to H.R. 6, which passed in December of 2007 (110-140). Expect it to achieve next to nothing in terms of ocean energy.
Continental reserves of oil and gas will only prolong the life of this country for a decade, if that. The United States Congress needs to step up to the plate for alternative energy sources, and hydrokinetic power looks to be one of the most esthetic, enduring and reliable sources of energy available.
Disclosure: I don’t own Atkins Global stock.