Big Isle project to test viability of using heat from ocean to generate electricity

A Kona-based technology firm is planning a project that will take an important step toward adopting ocean thermal energy conversion on a large scale.

Makai Ocean Engineering Inc. said Monday it will connect a small-scale OTEC system to the electrical grid in Kona on Hawaii island.

"It is the first time in history that a closed-cycle OTEC system is going to be connected to a U.S. electrical grid," said Duke Hartman, vice president of business development at the Hawaii island-based technology firm. The company plans to connect the 100-kilowatt demonstration plant in early 2015.

OTEC produces electricity from the ocean by using the temperature difference between deep cold and warm surface seawater.

The plant will help the company get closer to commercializing OTEC as a scalable source of renewable energy.

"We are looking to study the effect on the electrical grid at the Natural Energy Lab in Kona, and are looking for partners in that endeavor," Hartman said. "The primary goal of the project is to help scale up OTEC to a commercial size."

The vision is of multiple 100-megawatt offshore floating OTEC plants that will provide power for the state, Hartman said.

"OTEC starts to be cost-competitive at a large size, around 100 megawatts — capable of supplying power at rates even lower than our current electrical rates," he said.

Large-scale OTEC is a promising renewable energy source, said Hawaii island’s electric utility.

"OTEC is a clean energy technology that, if proven commercially, has great potential," said Kristen Oki­naka, spokes­woman for Hawaii Electric Light Co.

"We’re looking forward to the results of their project."

Makai’s OTEC system, based at the Natural Energy Laboratory of Hawaii Authority, received several major pieces of equipment for the demonstration plant Monday.

The pieces include two new heat exchangers and a 100-kilowatt turbine generator. The heat exchangers and turbine are in various stages of installation and testing.

Heat exchangers help extract heat from the ocean, which is converted to electricity by the OTEC cycle.

Understanding how the heat exchangers work will help Makai make OTEC more economical, with the exchangers making up roughly one-third of capital costs for an offshore plant. Reducing heat exchanger cost is a major goal of the project, Hartman said.

"Heat exchangers will be the single most expensive component in a commercial offshore OTEC plant, and so reducing the size and cost of OTEC heat exchangers is an important step toward making OTEC even more cost-competitive," he said.