Oceans cover more than 70% of the Earth's surface and hold 97% of the world's water.
The ocean surface absorbs thermal energy from the sun, which drive winds that power waves. The gravitational pull of the moon primarily drives the tides. New technologies are in development that promise to harness the incredible thermal and mechanical energy generation potential of the oceans. In addition to off-shore wind energy, the three most well-developed technologies are tidal power, wave power and ocean thermal energy conversion.
Renewable ocean energy is an emerging sector in the renewable energy industry. While ocean energy itself has been researched and tested for many years, new advances in technology - coupled with greater evidence of climate change and high global prices for conventional carbon-based fuels like oil and natural gas - have generated significant new interest in ocean energy resources in the United States, Canada, the European Union, Australia and New Zealand.
The Federal Government recently initiated the development of regulations to allow the leasing, permitting and development of ocean renewable energy facilities in Federal waters. Several coastal states, as well, are assessing the technical, political, practical and environmental implications of ocean energy technologies and how this new use can be accommodated, or not, in the coastal zone.
H.R. 1690, introduced by Congresswoman Capps in the 111th Congress, amends the Coastal Zone Management Act to establish a new grant program encouraging coastal states to voluntarily complete renewable energy surveys of coastal state waters and federal waters adjacent to a state's coastal zone. These surveys would then be used to identify areas suitable or unsuitable for development of renewable energy projects. The overall goal is to encourage states, in consultation with the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) to plan appropriate location of renewable energy projects and eliminate future state consistency certification conflicts between state and federal governments.
Ocean Tidal Power
Worldwide, two high and two low tides rush over our coasts every day (over a 24 hour period). To harness these energies into electricity, the difference between high and low tides must be at least five meters, or more than 16 feet. There are only about 40 sites on the Earth with tidal ranges of this magnitude. Conditions are good for tidal power generation in both the Pacific Northwest and the Atlantic Northeast regions of the United States. Careful consideration of the sensitive estuarine and coastal habitats must be considered in employing these technologies. The recently developed tidal turbines may provide the most environmentally friendly of the tidal power technologies because these systems don't block migratory pathways.
Ocean Wave Power
There is tremendous energy in ocean waves. Renewable energy analysts believe there is enough economically recoverable energy in the ocean waves worldwide to produce an estimated 140 to 750 terrawatt-hours per year (one terawatt is a trillion watts). Wave-power rich areas of the world include the western coasts of Scotland, northern Canada, southern Africa, Australia, and the northeastern and northwestern coasts of the United States. In the Pacific Northwest alone, it's feasible that wave energy could produce 40–70 kilowatts (kW) per meter (3.3 feet) of western coastline. The West Coast of the United States is more than a 1,000 miles long.
Wave and tidal power require a high initial investment in infrastructure, but these costs are coming down. Plus, once built, they have low operation and maintenance costs because the fuel they use—seawater—is free.
Ocean Thermal Energy Conversion
An emerging process, ocean thermal energy conversion (OTEC), uses the heat energy stored in the Earth's oceans to generate electricity. The ocean has layers of water with different temperatures and OTEC systems use this thermal gradient to drive a power-producing cycle. When temperatures between the warm surface water and the cold deep water differ by about 20°C (36°F), an OTEC system can produce a significant amount of power with the potential to help us produce billions of watts of electric power. This potential is estimated to be about 1013 watts of baseload power generation, according to some experts (Solar Energy Research Institute. (November 1989).
The 60 million square kilometers (23 million square miles) of tropical ocean surface absorb, on an average day, an amount of solar radiation equal in heat content to about 250 billion barrels of oil. If less than one-tenth of one percent of this stored solar energy could be converted into electric power, it would supply more than 20 times the total amount of electricity consumed in the United States on any given day.
U.S. Maps (pg.3):
Department of Energy (90 Meters)
Department of Energy - MA Focused map (50 meters)