Kona’s Keahole Point to Demo Ocean Thermal Energy

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Activities at Keahole Point in Kona have come full circle.

A Maryland company is proposing to build a demonstration project at the Natural Energy Laboratory of Hawai`i Authority at Keahole Point, which is located several miles north of Kailua-Kona.

The project will generate electricity using the temperature difference of seawater taken from different depths. The process is known as OTEC, which stands for Ocean Thermal Energy Conversion.

NELHA is ideal for the project because it features a set of massive pipes that draw 40-degree seawater from as deep as 3,000 feet off Keahole Point and water of nearly twice that temperature from near the surface.

It’s not a coincidence.

Originally known as the Natural Energy Laboratory of Hawaii when it was established in the early 1970s, the park was designed to research the use of the cold-warm energy differential to generate electricity.


In fact, most local residents at the time referred to the park simply as “OTEC.”

In 1979, “Mini-OTEC” was launched: a converted US Navy barge moored a little more than a mile offshore that generated 50 kilowatts of electricity.

These days, NELHA hosts a variety of tenants that make use of the ocean water. That includes the growing of algae, lobsters and abalone, and several companies selling desalinated seawater.

Now OTEC International LLC (OTI) is proposing to lease land at NELHA to build a land-based electrical generating facility.

According to a draft environmental assessment, the proposed facility would generate an estimated 1 megawatt of electricity, some of which will be used to power the facility.


Since the facility will not be connected to Hawaii Electric Light Co.’s electrical grid, the remainder will be fed into a “load bank” where it will be dissipated through the creation of heat. That will help demonstrate the plant’s “stability and reliability,” the EA said.

The study said if there is an outage of the HELCO grid, however, OTEC power could be used to power the pumps that draw in seawater.

The OTEC process uses warm surface water to boil ammonia which is run through a turbine to generate electricity. The colder water cools the ammonia in a closed-loop system and the ammonia is then re-used.

“Over the term of the lease, OTI will introduce and test technology enhancements to optimize the power cycle and to explore the full range of commercial opportunities,” the draft EA said.

Additional research could be associated with the OTEC plant in the future, the EA said, including work on a system that would extract carbon dioxide from seawater to generate hydrogen gas to be used as fuel.


According to the environmental study, OTEC International anticipates it will take two years to build the plant which should be operable for at least 25 years. If it is successful, a commercial version would be built on Oahu.

Although the EA does not specify the size of a commercial plant, it notes that the demonstration plant will need a crew of four to operate, while a commercial-sized version would require 100 workers.

The plant is anticipated to cost more than $10 million in labor and materials.

The NELHA anticipates that a “finding of no significant impact” will be issued for the project.

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