The global marine and hydrokinetic industry consists of energy extraction technologies that utilize the motion of waves, the currents of tides, oceans, and rivers, and the thermal gradients present in equatorial oceans. The Department of Energy (DOE) believes that marine and hydrokinetic energy technologies have significant potential to contribute to the nation’s future supply of clean, cost-effective, renewable energy.
In its March 2007 Assessment of Waterpower Potential and Development Needs, the Electric Power Research Institute (EPRI) conservatively indicated that marine and hydrokinetic power (exclusive of ocean thermal energy resources) could provide an additional 23,000 megawatts (MW) of capacity by 2025 and nearly 100,000 MW by 2050.
In a more recent 2009 study appearing in HydroReview, collaborating authors from the University of Washington, the Virginia Tech Advanced Research Institute, and EPRI refined earlier estimates to conclude that resources could conservatively yield a total of 51,000 MW of extractable energy.
This estimate is the equivalent of 34 conventional coal-fired power plants. The Department is currently developing predictive cost and performance models to assess the near- and mid-term economic potential for developing these resources.
According to recent industry studies, potential ocean thermal energy conversion (OTEC) resources may be even larger. However, it is necessary to note that preliminary estimates of extractable U.S. resources are just estimates of technical potential that do not equate to economically recoverable energy. There still remains an industry need for detailed, comprehensive resource assessments and validation of the costs for recovering this energy, which the Department is currently supporting through its programs.
The marine and hydrokinetic energy industry is still at a relatively early stage of development with less than a half dozen small commercial projects installed worldwide and only one operating in the U.S, a river hydrokinetic project in Hastings, Minnesota. Much of the work being funded through the Department is, therefore, focused on evaluating the size, location and specific characteristics of the Nation’s off-shore ocean and river energy resources, establishing baseline cost, performance and reliability data for a variety of devices, and assessing the environmental impacts associated with various technologies.
Marine and hydrokinetic energy (which uses currents, tides, waves and marine thermal gradients, as well as river flows on land) is still scarcely deployed compared to other renewable sources: there are less than 10 operating commercial plants in the world, of which only one in the United States (with hydrokinetic turbines on the Mississippi). However, the US potential is very significant, both at sea, and in internal freshwater flows.
Over the past two years the DOE’s Office of Energy Efficiency and Renewable Energy has allocated a substantial portion of its budget to marine energy projects: $ 5.8 million for wave power, $ 4.5 million for tidal energy, $ 1.9 million for energy from ocean currents and $ 6.2 million for energy from ocean thermal gradients.
Wave energy can be harvested from offshore, near shore, and shore-based environments through a number of engineering approaches. While there is currently no international consensus on nomenclature for wave energy devices, the Department is working with the Intergovernmental Panel on Climate Change and the International Electrotechnical Commission on standards to better define terminology. Major technology types are listed below.