World's Newest Form of Marine Renewable Energy Launched in Hawaii

It's called Ocean Thermal Energy Conversion, or OTEC, and the world's largest plant was dedicated in Hawaii on August 21. It produces renewable energy by using the temperature difference between the ocean's deep cold water and warm surface water.

2 minute read

August 31, 2015, 9:00 AM PDT

By Irvin Dawid


Emission-free energy is now being produced in Hawaii by Makai Ocean Engineering, thanks to funding by the Office of Naval Research through the Hawaii Natural Energy Institute," states Makai's news release. The $5 million, 105-kilowatt demonstration plant on the Big Island "only generates enough electricity to power 120 homes," writes Cole Mellino for EcoWatch. "But to date, it’s the largest such plant in the world."

Corrosion Facility

Credit: Makei Ocean Engineering

The company estimates that all of Hawaii’s electricity needs could be met by about 12 commercial-scale OTEC plants. They already have plans to construct a 1-megawatt facility in Japan.

“Anywhere tropical with deep water is ideal, especially if they import their fuel,” says Duke Hartman, vice president of business development at Makai.

While technically classified as a type "marine renewable energy," it's actually a form of solar energy, captured by the ocean and converted to electricity. "That’s beautiful because we can extract that energy 24/7 and use that power any time we want it, totally eliminating the need for an energy storage system,” states Hartman.

"Heat exchangers are really the key component to OTEC," states Hartman in this five-minute YouTube video as he point to the three pipes, standing on top of the plant.


Credit: Makei Ocean Engineering

"OTEC is a technology that the Navy has a significant interest for generating power at Naval bases around the world," states the naval research paper, "Understanding Predictability of the Ocean" [PDF]. "By using an [sic] Rankine engine cycle with fluorine gas cooled by deep ocean water and warmed by surface waters, turbines are used to generate electrical power that is sent back to shore."  [The video explains it in more detail.].

"The breakthrough marks the first true closed-cycle OTEC plant to be connected to a U.S. electrical grid, and represents a major achievement for Hawaii, the United States, and marine renewable energy," according to the news release.

The biggest challenge remains will be funding. "We need a visionary investor to get us past the expensive pilot project into the large-scale commercial projects," states Hartman.

Wednesday, August 26, 2015 in EcoWatch

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Wastewater pouring out from a pipe.

Alabama: Trump Terminates Settlements for Black Communities Harmed By Raw Sewage

Trump deemed the landmark civil rights agreement “illegal DEI and environmental justice policy.”

April 13, 2025 - Inside Climate News

High-rise apartment buildings in Waikiki, Hawaii with steep green mountains in background.

Study: Maui’s Plan to Convert Vacation Rentals to Long-Term Housing Could Cause Nearly $1 Billion Economic Loss

The plan would reduce visitor accommodation by 25% resulting in 1,900 jobs lost.

April 6, 2025 - Honolulu Civil Beat

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

7 hours ago - Diana Ionescu

Streetcar and bus stopped at station on Market Street in San Francisco with Ferry Building visible in background.

Waymo Gets Permission to Map SF’s Market Street

If allowed to operate on the traffic-restricted street, Waymo’s autonomous taxis would have a leg up over ride-hailing competitors — and counter the city’s efforts to grow bike and pedestrian on the thoroughfare.

4 hours ago - San Francisco Examiner

Parklet with wooden benches and flower boxes on street in Ireland.

Parklet Symposium Highlights the Success of Shared Spaces

Parklets got a boost during the Covid-19 pandemic, when the concept was translated to outdoor dining programs that offered restaurants a lifeline during the shutdown.

5 hours ago - Streetsblog San Francisco

Bronze statue of homeless man (Jesus) with head down and arm outstretched in front of St. Matthew Cathedral in Washington D.C.

Federal Homelessness Agency Places Entire Staff on Leave

The U.S. Interagency Council on Homelessness is the only federal agency dedicated to preventing and ending homelessness.

6 hours ago - The New York Times