Ocean Thermal Energy Conversion offers a renewable future if proper planning, precautions are met

News Report
Travis Quezon
The land-based OTEC facility at Keahole Pointe on the Kona coast of Hawai'i.

The land-based OTEC facility at Keahole on the Kona coast of Hawai'i.

The increasing urgency to adapt to global warming has fueled the search for an economically viable source of renewable energy.

The state of Hawai'i currently relies on imported fossil fuel for 94 percent of its energy.

Today, Governor Linda Lingle announced plans to build a 10 megawatt Ocean Thermal Energy Conversion (OTEC) plant in Hawai'i to act as a pilot for further potential projects. The plant will be the product of an energy partnership between the Taiwan Industrial Technology Research Institute and the Lockheed Martin Corporation, the largest defense contractor in the world.

"As island economies in the Pacific, Taiwan and the State of Hawai'i share very similar challenges of over-dependence on imported petroleum for their energy needs," Governor Lingle said. "Taiwan and Hawai'i also share a common vision and plan to increase renewable and clean energy generation based on indigenous energy resources."

Taiwan's Bureau of Energy plans to increase its renewable energy resources to account for 12 percent of its energy by 2020. Taiwan currently generates less than one percent of its energy from indigenous renewables.

With OTEC, Taiwan and Hawai'i see potential in a source of energy that will have minimal impact on the environment.

OTEC is a process that uses the heat energy stored in the ocean to generate electricity by using the difference in temperature between the warmer top levels of water and the colder deep ocean water. OTEC plants use large diameter intake pipes, which are submerged over a mile down into the ocean, to bring cold water to the surface.

The U.S. Department of Energy says that OTEC may one day become cost-competitive with conventional power technologies, such as oil and coal.

In an analysis of OTEC's impact on the environment, Hawai'i scientist L.A. Vega said the process of generating energy through OTEC offers little risk:

"OTEC requires drawing seawater from the mixed layer and the deep ocean and returning it to the mixed layer, close to the thermocline, which could be accomplished with minimal environmental impact. The carbon dioxide out-gassing from the seawater used for the operation of an OC-OTEC plant is less than 1 percent of the approximately 700 grams per kWh amount released by fuel oil plants. The value is even lower in the case of a CC-OTEC plant."

However, a carefully planned location of a plant for optimum ocean temperature and precautions against biofouling (an accumulation of microorganisms, plants, and algae on OTEC structures) are necessary to minimize its environmental impact.

Water organisms that pass through the OTEC plant may also be exposed to biocides as well as temperature and pressure shock—which can be fatal.

Other risks involve an affect on commercial and recreational fishing. Fish will be attracted to the OTEC plant, potentially increasing fishing in the area but possibly leading to the loss of inshore fish eggs and younger fish due to impingement, entrainment and a discharge of biocides—ultimately leading to a shrinking fish population.

As the state ventures into new technologies, the Hawai'i community must also ensure that proper precautions are taken on the road to a new sustainable future.