Harnessing the Ocean as a Renewable Energy Source

In today's growing mix of alternative energy sources, the ocean holds special promise in providing our world with clean, abundant renewable energy.

According to the National Renewable Energy Laboratory , 60 million square kilometers (23 million square miles) of tropical seas absorb 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.

Clearly, our seas represent an incredible renewable energy resource. But will we ever be able to extract enough energy from the ocean to replace our dependence on finite fossil fuels?

In April 2005, the Ocean Renewable Energy Coalition (OREC) in Washington, D.C. was founded by corporate communications expert Sean O'Neill and attorney Carolyn Elefant to "promote and advance commercialization of marine renewables in the United States. Our organization embraces a wide range of renewable technologies, including wave, tidal, current, offshore wind, ocean thermal, marine biomass and all other technologies that utilize renewable resources from oceans, tidal areas and other unimpounded water bodies to produce electricity, desalinized water, hydrogen, mariculture and other by products."

OREC's mission statement sums up the myriad of complex, yet promising ways we can harness clean, renewable energy derived from our oceans. Three of the most researched areas of renewable ocean energy production cited by OREC include tidal stream, wave power, and ocean thermal.

Tidal stream energy is derived from turbines placed on the ocean floor that catch ocean currents, much like a windmill catches the wind. Wave power involves the laying of offshore buoys and other wave-capturing devices that generate electricity as they rise and fall with the waves. And last but not least, ocean thermal energy is produced by exploiting the ocean's thermal gradient (the difference in temperature in ocean layers) to drive an electricity-producing cycle.

But like all alternative forms of energy, these three increasingly popular ocean renewables have their technical challenges.

With tidal stream power, saltwater corrosion becomes a problem as does the possibility of aquatic life being sucked into the turbine. Wave power can prove inconsistent; corrosion, storm damage, inefficiency, and high cost of generation are further impediments. Ocean thermal energy has great potential; but extraction is challenged by inefficiency and high costs associated with pipes, pumps, and pumping materials. And with all three of these ocean renewables, rising sea levels, choppy waters, and intense storms caused by global warming may also pose a difficult challenge.

Renewable energy derived from our oceans holds much promise if we can overcome these key technical issues while at the same time recognizing and working around the long-term effects of climate change.