U.S. Department of Energy - Energy Efficiency and Renewable Energy

Water Power Program

New Reports and Maps Show Riverine Hydrokinetic & OTEC Potential

January 16, 2013

The Energy Department recently released two nationwide resource assessments showing the potential ocean thermal and river hydrokinetic resources available to contribute to the United States’ total annual electricity production. These reports represent the most rigorous analysis undertaken to date to accurately define the magnitude and location of U.S. and global ocean thermal and continental U.S. river hydrokinetic resources.

The two reports – “Assessment and Mapping of the Riverine Hydrokinetic Resource in the Continental United States” and “Ocean Thermal Extractable Energy Visualization” – calculate the energy available from ocean thermal gradients off U.S. coasts and from U.S. rivers that can be used for future production. Both reports are available from the Water Power Program’s resource assessment and characterization webpage.

The riverine hydrokinetic resource report, authored by the Electric Power Research Institute (EPRI), assesses the recoverable riverine (or “run-of-river”) hydrokinetic energy resource in the contiguous 48 states and Alaska, excluding all tidal waters. Riverine hydrokinetic energy is captured when the natural flow of a river or stream powers a turbine that is set at a lower elevation. Unlike traditional dam systems that are used for hydropower, riverine hydrokinetic generators use very limited water storage, making them dependent on the seasonal river flow.

The report estimates that the potential for riverine hydrokinetic generation for the continental United States is 120 terawatt-hours per year (TWh/yr), with 80% located in four hydrologic regions: the lower Mississippi (48%), Alaska (17%), the Pacific Northwest (9%), and the Ohio River (6%).

The ocean thermal energy resource assessment analyzes the potential for the conversion process where the temperature differential – or thermal gradient – between the colder waters below and the warmer surface level is used to run a heat engine which generates electricity. Within U.S. waters off the nation’s coasts plus Puerto Rico, there is an estimated 576 TWh/yr of energy available of ocean thermal resource potential which is concentrated in the following regions:

  • 143 TWh/yr located off Hawaii
  • 53 TWh/yr in the Gulf of Mexico
  • 342 TWh/yr off the East Coast
  • 38 TWh/yr off of Puerto Rico and the Virgin Islands.

Broadening the area under consideration to all U.S. exclusive economic zone (EEZ) waters, the cumulative thermal energy potential is 4600 TWh/yr.

The ocean thermal energy resource assessment report was prepared by Lockheed Martin with support from working partners at the National Renewable Energy Laboratory (NREL), Florida Atlantic University, and University of Hawaii. The riverine hydrokinetic resource assessment report was prepared by the Electric Power Research Institute (EPRI) with support from the National Renewable Energy Laboratory (NREL), University of Alaska Anchorage, and University of Alaska Fairbanks. Both reports describe the methods used to produce geospatial data on technically available ocean thermal and river hydrokinetic resources. NREL is incorporating these data into interactive web mapping applications (NREL MHK Atlas and River Atlas).

In addition to the ocean thermal and river hydrokinetic resource assessments, DOE released its U.S. wave and tidal resource assessments in 2012 and will release an assessment of the ocean current resource in 2013. DOE’s assessments show that the maximum of theoretical electric generation that could be produced from waves, tidal and riverine currents, and ocean thermal resources in U.S. water is 2,116 TWh/yr. For comparison, the United States uses about 4,000 TWh of electricity each year. The nation’s enormous marine and hydrokinetic energy potential represents major opportunities for new water power development in the United States. To support the development of technologies that can tap into these vast water power resources, the Water Power Program at the Energy Department is undertaking detailed technical and economic assessment for a wide range of water power technologies in order to more accurately predict the opportunities and costs of developing and deploying these innovative technologies.

The Energy Department invests in clean energy technologies that strengthen the economy, protect the environment, and reduce dependence on foreign oil. DOE’s Water Power Program is paving the way for industry and government to make sound investment and policy decisions about the deployment of renewable water power technologies by quantifying the nation’s theoretically available water power resources.