An exciting, encouraging new energy source is being developed in Hawaii. It is called Ocean Thermal Energy Conversion (OTEC) and may help Hawaii accomplish its goal of 100 percent renewable energy by 2045.
Seventy percent of the sunlight hitting earth is captured in the surface layers of the oceans in the form of heat. OTEC produces electricity using the temperature difference between warm ocean surface waters and much colder deep water. The energy can be extracted 24 hours a day 7 days a week in Hawaii and the power can be used any time without a need for an energy storage system.
The Makai plant was built for the study of heat exchangers with several lines on which versions of the exchangers could be swapped in and out for testing. The goal was to find high performance, low cost, and long lasting heat exchangers. Now it may start replacing conventional power plants.
In simple terms, warm sea water flows into a heat exchanger. A refrigerant with a low boiling point is used to boil the ammonia from the water and turn it into a really high pressure ammonia vapor. It propels through a pipe and spins a turbine. The rotational motion powers the plant through the turbine’s connection to a generator which is connected to the power grid.
After the vapor leaves the turbine, it is converted back to a liquid in the condenser filled with hundreds of small tubes. Cold sea water passes around the tubes, the ammonia senses the cold and is converted back into a liquid to continue the cycle.
With Hawaii’s temperature stable waters year round, the process provides a steady power stream. No inverter is needed, the fuel is free, and as the OTEC technology is perfected, the price of electricity will decrease.
The technology is not as risky as harnessing wave power and not dependent on the wind as in wind power. It can be ramped up and down to meet fluctuating demand or intermittent power surges from solar and wind farms. OTEC is a clean energy source, environmentally sustainable and can produce massive energy levels.
The current Makai OTEC plant, developed with the Hawaii Natural Energy Institute, University of Hawaii at Manoa, has a capacity of 105 kW. Makai has contracted to develop a 1 MW plant on the island of Kyushu in Japan. The company is also working with Lockheed Martin to plan a 100 MW installation in Hawaii or Guam which would operate offshore, power 100,000 Hawaiian homes, and the power could be sold for 20 cents per kWh.