More than a dozen people, including various legislators, took part in a dedication ceremony held for a new 40-foot-tall heat exchanger test facility Friday at the Natural Energy Laboratory of Hawaii Authority. The $5.8 million research project is funded by the federal Office of Naval Research and Naval Facilities Engineering Command through the University of Hawaii’s Hawaii Natural Energy Institute.
“We need to make ocean thermal energy conversion economically viable. We need to make it cheaper to purchase power (produced by ocean thermal energy conversion) than it is (to purchase power produced by) oil,” said Michael Eldred, a mechanical engineer and project manager with Makai Ocean Engineering Inc. “The key to doing that is by making the heat exchanger cheaper, last longer and more efficient.”
To do that, the ocean engineering company has designed and constructed a heat exchanger test facility and lab at the Natural Energy Laboratory of Hawaii Authority in Kona. There, research will be conducted using different aluminum alloys to develop a lower-cost heat exchanger, which is used in the conversion process to transfer heat from one fluid to another, in an effort to draw investors, commercial interest and, possibly, large-scale power production, he said.
Various aluminum alloys will be tested for their resistance to seawater corrosion to determine whether an alloy, rather than the currently used titanium heat exchanger, could be used. If an aluminum alloy can replace titanium, the price of a heat exchanger could be up to four times less, Eldred said.
“The ability to reduce the cost of the heat exchanger and demonstrate they perform (at the same level) is critical to people making a business decision that will allow us to move forward,” said Richard Rocheleau, director of the Hawaii Natural Energy Institute, a sponsor of the project. “The fuel is free, it’s water and it’s out there, but it’s a very large capital investment and the risks and costs need to be removed in order to move forward.”
The research project also marks the return of ocean energy thermal conversion at NELHA, which last took place in 1998, said Jan War, NELHA operations manager. The last project ended with the closure of a 210-kilowatt research ocean thermal energy conversion plant.
Once the current research is complete, the company hopes to take the project to the next level by installing a turbine to test power production on a small-scale level, Eldred said. Funding is currently being sought for that venture.
From there, Eldred said, the creation of offshore ocean thermal energy conversion plants capable of producing 100 megawatts could be built at a cost of $1 billion apiece. If 10 of the plants, which would look similar to an oil rig and be located about four miles offshore, were in operation, all of Hawaii’s power needs could be met, he added.
“Just 10 could power all of Hawaii and we would have no other need for power,” he said. “Hawaii is a perfect location for this. It’s one of the best places for ocean thermal energy conversion because it’s all right here.”
Ocean thermal energy conversion is a process used to produce electricity by using the temperature difference between deep, cold ocean water and warm tropical surface water, Eldred said.
Electricity is produced in a closed cycle by warm seawater passing through an evaporator that vaporizes the working fluid, which in the current research project is ammonia. The vapor then passes through a turbine, which turns a generator to make electricity, before going through a condenser that uses cold seawater to return the vapor to a liquid before being reused, Eldred said.
