Vol. 7 | No. 1 | Spring 2008
Wave Power Generation
As the need for global warming solutions becomes more urgent, engineers and entrepreneurs are looking for new ways to expand our use of clean, domestic renewable energy. One of Earth’s most promising resources in this regard is also one of its largest: the ocean. The Electric Power Research Institute (EPRI), an independent nonprofit and leader in wave power research, estimates that this resource could credibly supply the United States with as much as 260 billion kilowatt-hours of electricity per year—as much as that generated by all conventional U.S. hydropower facilities combined.
Ideal locations for wave power projects are those that receive the full force of the waves before the waves hit the ocean floor and lose energy, are close enough to shore so transmission cables will not be prohibitively expensive, and are deep enough that the generating equipment will not crash against the seabed during storms. Seafloor maps show that the best U.S. locations according to these criteria are the Pacific Northwest, the Northeast, and Hawaii.
Different Ways to Catch a Wave
Wave power technologies currently being developed and tested worldwide generally fall into four categories.
Point absorbers are buoy-like cylinders that bob on the ocean’s surface. The motion of the waves moves a piston inside the cylinder, which creates hydraulic pressure that drives a turbine.
Overtopping devices generate electricity in the same way as a traditional hydropower dam: by collecting water in a reservoir and then releasing it through Wave Power Generation turbines. Resembling a letter C floating on the ocean’s surface, the overtopping device consists of a concrete ramp and two steel wave-reflecting arms, which direct a maximal amount of seawater up the ramp and into a holding tank. The water then flows down through turbines as it is released from the holding tank back into the ocean.
Attenuators, or “heave-surge” devices, are long, segmented structures (resembling a snake) that float parallel to the direction of the waves. The motion of the waves causes the joints between segments to flex, driving internal hydraulic pumps that, in turn, power a turbine.
Oscillating water columns consist of partially submerged, nearly vertical tubes with openings at the top and bottom. As waves enter the underwater opening at the tube’s base, they compress the air inside the tube, forcing it up through a turbine at the top. As the waves retreat, air is sucked back into the tube’s upper opening and down through the turbine, generating more electricity.
|
Underwater Unknowns
Wave power developers must attempt to understand the effects this technology will have on marine habitats.
However, scientists are also studying potentially harmful effects. Placing a foreign object in the ocean and securing it to the seabed could, for example, disrupt and erode sediment, affecting fish and other organisms that thrive on or near the seafloor. Wave power equipment could also alter aquatic and avian species’ movements and migrations, and cause collisions with structures or entanglement in underwater cables. These problems can be minimized through greater experience with prototypes. Other concerns that have been raised, such as sound pollution, chemical and paint toxicity, and electromagnetic fields, can all be addressed based on our experiences with ships and oil-drilling platforms. |
What the Future Holds
As with any new technology, wave power will likely encounter several obstacles on the path toward large-scale deployment. One of these is cost. According to EPRI projections, the first 100-megawatt wave power project to be deployed will generate electricity at a cost of about nine cents per kilowatt-hour, compared with estimates from consulting firm Black & Veatch of four to seven cents for new wind power projects and six to eight cents for new coal-fired power plants (assuming these plants will not face a financial penalty for global warming pollution). As technical expertise and economies of scale improve, however, wave power’s costs will decrease and become more competitive. Considering that 40 percent of a commercial wave power project’s annual expenditures may go toward operating and maintaining the equipment, reducing these costs will be critical to making wave-generated electricity cheaper than other technologies.
Constructive policies can play a role as well. Financial incentives such as tax credits and grants, for example, can speed the technology’s transition from research and development to commercialization. And eliminating overlapping jurisdictions among state and federal agencies, which often complicate and delay offshore renewable energy projects, would streamline the permitting process and allow companies to test and refine their designs more quickly.
The Federal Energy Regulatory Commission (FERC), the lead agency that approves electricity-generating projects, recently streamlined and shortened the licensing process for wave power demonstration projects, making it easier for companies to attract investors. FERC granted its first license under these new regulations in December for four 250-kilowatt point absorbers off the coast of Washington State. This is a promising first step in bringing wave power into the mix of clean energy resources we can tap in the coming decades to meet U.S. electricity needs and reduce the risks of climate change. ■
Emily Robinson is a UCS press secretary. John Rogers is a senior energy analyst in the Clean Energy Program.
