Ocean-based power a step closer to reality

In a small but significant development, with implications for the Cayman Islands, Hawaii has opened the world’s largest operational Ocean Thermal Energy Conversion plant. 

The Pacific island state flipped the switch last month on a 100-kilowatt facility, capable of providing power to 120 homes. 

Essentially a research project, the state-funded Makai Ocean Engineering plant is just a fraction of the size of a similar development being proposed in the Cayman Islands. 

OTEC International LLC hopes to begin construction on a floating power plant off the coast of North Side in Grand Cayman next year. 

The company is in the midst of the environmental impact assessment process on a planned project that, if approved, would provide an initial 6.25 megawatts of electricity to Cayman’s national grid. 

A power purchase agreement between the energy firm and the Caribbean Utilities Company is expected to go to the Electricity Regulatory Authority in the coming months. 

Ultimately, OTEC International believes its plant could be scaled up to provide 25 megawatts – around a quarter of Cayman’s electricity needs. 

Derek Dyson of OTEC International said the Cayman project would be the first commercial application of the technology, which uses the extreme temperature difference between sea surface and deep waters to create electricity. He said he hopes the necessary approvals will be accomplished by the end of the first quarter of 2016. 

He said the Hawaii project provides further proof that the process can be a sustainable, renewable power source. 

“The Hawaii project should give people even more confidence that this is technology that works,” he said. 

Gérard C. Nihous, an OTEC expert at the University of Hawaii, told Scientific American magazine that the value of the Makai project is not its size, but its ability to demonstrate the process. He said despite some engineering challenges, the technology behind OTEC was proven and the barriers to its development were largely economic. 

Mr. Dyson said OTEC International is confident that its plant is financially viable. 

“We have patents which are really around driving down the cost of the technology. We are making it as efficient as possible so we can be competitive with other alternative generation resources,” he said. 

OTEC International President Eileen O’Rourke said the project has the backing of the Baltimore-based Abell Foundation, which has a philosophy of patient investment in innovative technologies, allowing them to take more time to yield returns than would normally be possible. 

She believes the opening of an OTEC plant in Cayman will be a “major milestone” for the technology and for renewable energy generally. 

The OTEC process involves using large amounts of warm surface water to boil ammonia, creating gas to power conventional turbines. Cold water, piped up from almost 4,000 feet below the surface, is used to convert the ammonia vapor back to a liquid for recycling in a “closed loop system.” 

One key advantage that OTEC has over other renewables, such as solar and wind, is it would provide “firm power generation,” meaning it could run 24 hours a day, seven days a week, and therefore would not require diesel generators to be constantly spinning as a backup, according to the terms of reference for the ongoing environmental impact assessment.

***Editor’s Note: This story was edited at 10:05 p.m., Thursday, Sept. 10.***

The Makai OTEC plant opened in Hawaii last month.
The Makai OTEC plant opened in Hawaii last month.


  1. OTEC is the renewable energy source that CUC were promoting back in 2007 as an alternative to solar and wind power although they never revealed how it was planned to pay for it.
    One of the big disadvantages not spelt out here is the fact that OTEC needs to generate a lot of energy to produce energy. According to the Japanese, a 16MW installation will only produce 10MW for actual sale. This is because the installation requires huge amounts of water that have to be pumped through the system and those pumps have to be powered.
    It is also complete nonsense to suggest that this might be some kind of stand-alone operation with no backup because it is a mechanical process and they break down. A floating power plant will also be subject to weather-related shut downs.
    But I think the most disturbing aspect of this story is the suggestion that OTEC is proven technology. It may be a lot of things but proven is not one of them. Right now there are no viable OTEC plants operating in the world on anywhere near the scale of the one proposed for Grand Cayman. Put in perspective the one in Hawaii featured here is just about big enough to power a complex of condos.
    If you have an economy the size of the Hawaiian Islands OTEC is probably worth looking at but for a community the size of the Cayman Islands this is something that needs to left well alone until there is solid evidence that it works. In the meantime using solar and wind energy is not only a risk-free option relying on proven technology but is a heck of a lot cheaper.

  2. I cannot believe this idea is still being contemplated. Does any one asking the right questions?
    A) why Cayman? Answer, no other countries would allow for this power generator to operate so close to their shores.
    B) how much water flow will it requires. Answer, the total amount found in the north sound on a weekly basis. All of it from 1 mile from the shore.
    C) how will react our marine life? Answer, imaging a little plankton being ask to travel from a depth of 4,000 ft deep to 0 feet, or from sea level to 4.000 ft deep,and, from a temperature of 40f to 80t, or, 80f to 40f, then pass through pump impellers. That would be a head spinning ride. What are the chances for this plankton to come out alive?
    D) will it be fare to say that if the same amount of deep water at 40f could save twice as much energy that it would produce if used otherwise like providing cooling instead.