Offshore Renewable Energy

Offshore Renewable Energy refers to the generation of electricity from ocean-based resources. These include wind turbines located offshore in the oceans and Great Lakes and marine based energy sources including waves, tides, and salinity and thermal properties. Marine based projects are considered “offshore” if they employ ocean resources. For instance, a tidal generator located at a river’s mouth is considered offshore since it uses the flow of the ocean tides.

Map: Offshore Renewable Energy Projects

Over 80% of the United States population lives in coastal states, which comprise 80% of the national electricity demand (U.S. Department of Energy). The coastal states are the most densely populated areas with the highest average property values. In 2013, coastal counties in the U.S. had a housing and population density of over double that of the U.S. as a whole (see our Population and Housing section). 2015 data collected by Trulia reveals that the average price of real estate in coastal states is over $90,000 more than that of inland states. In light of the highly competitive nature of coastal land resources among other factors, many, especially the energy sector, are now looking toward the sea for industrial development. (McCauly et al. 2015).

Offshore renewable energy has been proposed as an important addition to the U.S.’s energy portfolio in order to increase energy security, and reduce carbon emissions. However, offshore renewable energy is in its infancy, and still faces many challenges such as lack of competitive costs, a developing supply chain, and unknown impacts and repercussions for the surrounding marine ecosystems (International Energy Agency 2013; TETHYS).

Conditions for Feasibility of Each Energy Type

Resource Water depth Latitude Avg. Speed Other Best Locations
Offshore Wind Grounded: 0-80 meters
Floating: 0-? meters
7 meter/sec wind speed at 90 meters above sea level
  • Northern California
  • Southern Oregon
  • Northeast (NY-ME)
Wave 40 meters 30° - 60° Off west coast of continents
  • Pacific Northwest
  • Alaska
OTEC > 1,000 meters 0° - 35°
  • Surface water: > 25° C
  • 20° difference in temperature surface water and extracted water
  • Hawaii
  • Puerto Rico
Current Shallow water (0 — 30 meters) Fast current speeds Located at place of high marine flow*
  • Florida (Gulf Stream current)
Tidal Range
  • Located at ocean inlet
  • Tidal height range at inlet > 7 meters
  • Maine
  • Washington state
  • Alaska
Tidal Stream 1.5 — 2 meter/sec water speed Located at place of high marine flow*

*Places of high marine current flow tend to be: narrow straits, between islands, around headlands, or entrances to lochs, bays, and harbors
**Table information sourced from IRENA, NREL, and Ocean Energy Council

Each offshore renewable energy source has varied availability and potential capacity for development in the U.S., based on where the ideal conditions align. The mapping of these conditions are critical in determining where the U.S. employs these renewable energies. For example, ocean thermal, though it can generate a large amount of power, is only feasible in places that hold the warm, tropical surface water that thermal conversion requires (International Renewable Energy Agency). In contrast, wave energy is best farther away from the equator where waves are the fastest, largest, and most consistent. If wave energy develops in the U.S., it would likely occur in the Pacific Northwest or Alaska (IRENA). The Northeast region holds most promise for offshore wind—this is where water depth is both shallow (i.e. turbine installment and maintenance is cheaper) and wind speeds are large (National Resources Defense Council).

Currently, there are few commercial offshore renewable energy operations in the U.S.. However, a number of developing technologies in marine hydrokinetic and offshore wind powers have drawn increasing interest. Because of this and the importance of new energy sources, NOEP has compiled a database of available infomation related to offshore renewable energy projects in the U.S.. Currently, the database contains all known offshore projects and any data regarding their locations, project types, stage of development, projected capacities, installation costs, expected employment, and more. Eventually, NOEP will also include international project data to track the more advanced progress of these emerging industries abroad.

updated 20-May-2015