Ocean (Wave and Tidal) Hydrokinetic
The ocean is a potential goldmine for renewable energy generation, as long as investment into ocean power technologies continues. A 2003 report by the European Thematic Network on Wave Energy estimates that there will be between 150 – 750 terawatt-hours (1 TWh = 1,000,000 MWh) of economically recoverable wave energy available worldwide once current technologies are refined and mature, and increases in efficiency could triple that amount in the future. An Electric Power Research Institute report estimates that there are 2,100 TW of total wave energy off the coasts of the U.S., with over 50% of that potential in Alaska. Additionally, total energy from tidal friction is estimated at 2.5 TWs, or the equivalent of 2,500 one-thousand MW nuclear power plants. Development of ocean energy generation technologies are still in the demonstration stage, but have great potential to become a leading source of renewable energy in the near future.
Tidal energy is a concentrated form of the gravitational energy exerted by the moon and, to a lesser extent, the sun. This energy is converted into electricity in two ways: by dams that force water through turbines at high and low tidal stages, and by underwater turbines activated by tidal flows. Most commercial tidal power facilities, including the 240 MW Rance tidal power plant in La Rance, France, use dams to channel tidal flows into narrow passages, thus extracting more energy. However, numerous “in-stream” tidal generators that work like underwater wind turbines are in the development or demonstration stages. The first commercial tidal facility using this technology opened off the coast of Ireland in 2008. The same underwater turbine technology was first applied to small (less than 100 kW) electricity generators in 2008 to test the usefulness of the turbines in river currents. The 5 kW prototype installed at the Yukon River town of Ruby, Alaska successfully generated enough electricity to power two homes for the summer. Similar projects are currently under consideration in Eagle and Nenana. Tidal energy is preferable to river currents or even wind because it can be reliably predicted centuries in advance.
Alaska has one of the strongest wave resources in the world, with parts of the Aleutian Islands coast averaging more than 50 kW per meter of wave front. The challenge is lack of energy demand near the resource. Much of Alaska’s wave energy is dissipated on remote, undeveloped shorelines. Other substantial wave energy areas include the southern side of the Alaska Peninsula and coastlines of Kodiak and Southeast Alaska. The best prospect for wave energy development in Alaska may be Yakutat, where studies for a 750 kW pilot project will soon be underway