OTEC pilot plant to be built in Okinawa Prefecture

This month, Japanese engineering companies IHI Plant Construction Corporation, Xenesys Incorporated and Yokogawa Electric Corporation announced their collaboration in building a 50kW OTEC demonstration plant in the waters of Kumejima Island, located in the very south of Japan and part of the Okinawa Islands. The OTEC plant will be integrated in the Okinawa Prefecture Deep Seawater Research Center, which is the largest of four deep seawater pumping systems in Japan. The companies aim to have the OTEC plant up and running in March 2013.

Kumejima Island deep seawater research station
Kumejima Island deep seawater research station

Regarding the roles in this project: Xenesys will design and manufacture the power generation unit and the heat exchangers; Yokogawa will design, manufacture and do the engineering of the monitoring and control system for the generation unit and the electronics for the interconnected power schemes; and IHI will develop and construct the entire facility.

Okinawa Research Center is active in deep seawater utilization for over 10 years. The center established several deep seawater projects, including local area cooling services, water desalination, aquaculture and agriculture. Next year the OTEC demonstration plant will be added and connected to the deep seawater infrastructure. The OTEC plant will be used for practical testing and optimization of the output. It is an important step in the commercialization following the 30kW demonstration unit at Saga University in Saga, Japan.

The current capacity of the Okinawa Research Center is about 13,000 tons of seawater per day, pumped up from a depth of 612 meter where the water is between 6 and 8°C. The temperature of the surface seawater is around 26°C annual average, providing stable production possibilities.

Kumejima Island
Kumejima Island

Regarding future scale-ups, Xenesys estimated that it is possible to increase the intake of

deep seawater to 100,000 tons per day and install 1.25MW OTEC power capacity. This would supply 10,600 MWh of electricity per year, which accounts for 10% of Kumejima’s total annual consumption.The island of Kumejima, which entered into a Sister City Relationship with the county of Hawaii last year, aims to become a self-sustaining community and model for other small islands in the Okinawa Prefecture.

For more information about Deep Seawater development in Japan, please visit:

Presentation by Chihiro Tominaga about the Hawaii-Okinawa partnership: http://www.usjapancouncil.org/images/uploads/HAWAII-OKINAWA_Okinawa_Gov_-_Tominaga.pdf

Overview the Deep Seawater “Kumejima model” by Xenesys: http://www.xenesys.com/english/common/pdf/kumejima.pdf

Paper about the application of Deep Seawater in Japan: http://www.lib.noaa.gov/retiredsites/japan/aquaculture/proceedings/report28/Nakasone.pdf

The website of Okinawa Island about their deep seawater utilization: http://www.okinawab2b.jp/misc6.html