A small power plant that can convert the temperature difference between deep ocean and surface ocean waters into electricity was unveiled in Hawaii last week, the first of its kind to be connected to the grid.
Even though ocean thermal energy conversion (OTEC) has been researched for decades, it has not yet been demonstrated to be a reliable, cheap source of renewable energy. The new plant in Hawaii will elucidate whether the technology should be developed further and where it should be distributed.
The plant was funded by both the Natural Energy Laboratory of Hawaii Authority and the Office of Naval Research.
This alternative technology could be an excellent choice for Hawaii, since the island chain relies on expensive imported fossil fuels to provide electricity. The state plans to generate 100% of its electricity with renewables by 2045, so it would be very advantageous for the state if they could capitalize on their unrivaled access to ocean water.
The plant works using the temperature difference between surface and deep water. The system takes in surface ocean waters, which are warmer, to evaporate ammonia to create steam. The steam makes a turbine spin, making electricity. Cold water from deeper in the water then cools the ammonia down and turns it back into a liquid. The plant in Hawaii is a closed-loop system, meaning that the ammonia is recycled and gets evaporated and condensed over and over again. In open systems, evaporated water spins the turbine.
It remains to be seen whether OTEC will be viable on a commercial scale. However, one advantage OTEC may have over more popular renewables like solar and wind is that OTEC constantly creates electricity, since it does not rely on the weather.
The plant, designed and implemented by Makai Ocean Engineering, can only currently power 120 homes a year, but “this plant provides a much-needed test bed to commercialize ocean thermal energy conversion technology and bolster innovation”, explains the Hawaiian governor, David Ige, in a statement.