Study will look at ammonia storage, disaster plans
A floating power station using the solar energy stored in Grand Cayman’s warm tropical waters could provide the first firm renewable energy supply capable of replacing diesel generators on the island, according to documents setting out the scope of an environmental study.
If successful, the Ocean Thermal Energy Conversion plant would be able to provide firm, reliable power to the national grid 24 hours a day, reducing reliance on fossil fuels.
The technology, unlike solar or wind, would not require diesel generators to be constantly spinning as a backup, according to the terms of reference for an Environmental Impact Assessment on the proposed project.
“Each megawatt of distributed OTEC power would displace and subsidize a portion of the power generated by fossil fuels, thereby lowering the need to import gasoline and diesel that are both economically and environmentally costly,” the document says.
“By contrast, non-firm intermittent power renewable technologies such as wind and solar photovoltaic do not eliminate the need to maintain fossil fueled spinning reserve capacity for those times when wind and solar energy sources are absent or reduced.”
The project, commissioned by OTEC International LLC, would be the world’s first commercial power plant using ocean thermal energy conversion.
The technology converts solar energy stored in tropical oceans to utility-scale power through a process that exploits the large temperature gradient between water on the surface and that found at depth.
The company initially aims to supply 6.25 megawatts of wholesale electric power, increasing production to 25 megawatts following a trial period.
Charles Farrington, managing director of the Cayman Islands Electricity Regulatory Authority and a member of the Environmental Assessment Board that is overseeing the study, said the project has the potential to be a significant one in Cayman’s energy future.
“It will obviously be an important development if they can bring it to commercial reality,” he said. “If it works and it goes through a period where it proves itself to be reliable, the expectation is that it would be classified as firm renewable power.”
The OTEC process involves using large amounts of warm surface water to boil ammonia, creating an “ideal gas” to power conventional turbines. Cold water, piped up from a target depth of 3,770 feet below the surface, is used to convert the ammonia vapor back to a liquid for recycling in a “closed loop system,” the document states.
The up-front cost of building the plant and associated infrastructure are likely to be extensive, though OTEC International has not revealed exactly how much it expects to spend on the project.
Mr. Farrington expects the initial impact on the cost of electricity to be limited. He said the prices would have to be competitive with current rates for a power purchase agreement with the Caribbean Utilities Company to be approved.
He said the long-term advantage of OTEC, despite the high up-front costs, would be that, unlike oil, the price would be stable and not subject to fluctuations in the international market.
The entire cost of the project, including the environmental impact assessment, is borne by the OTEC International, which is backed by Baltimore-based charitable organization the Abell Foundation.
Mr. Farrington said, “They are confident enough to invest that money and we are hoping they are not mistaken – it is essentially their risk.”
A meeting was held in North Side last week to allow residents’ input into the environmental study.
The power plant would be moored off the north coast of Grand Cayman and connected to the power grid through a buried cable running to a substation on shore, close to the Over the Edge restaurant.
Wendy Williams, an environmental assessment officer with the Department of Environment, said residents’ concerns would be considered in the environmental impact assessment if they were filed in writing with the department before Oct. 3.
Ms. Williams, who is also a member of the Environmental Assessment Board overseeing the study, said the ability of the platform to withstand hurricanes, as well as the safety procedures to ensure the ammonia used in the process is contained, would be part of the assessment.
“The Department of Environment is very keen to explore alternative sources of energy generation that don’t rely on fossil fuels. We are very interested [in OTEC] but we need to know the coasts and benefits to the country and that’s what the environmental impact assessment will discover.”
She said an environmental statement would be produced by weighing the positive and negative effects and allowing decision makers to take a balanced view.
Eileen O’Rourke, president of OTEC International and treasurer of the Abell Foundation, said the company has been working for more than a decade to bring the technology to Cayman and is happy to address any environmental concerns raised through the study.
“In particular, OTEC International recognizes its responsibility in any future decommissioning of its facilities and in implementing rigorous safety standards, including, but not limited to, addressing ammonia storage, in coordination with and under guidance to be provided by the Department of Environment.
“OTEC International looks forward to getting the required authorizations to build the project and providing another source of renewable energy to Cayman.”