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Kumejima Model – an island move toward self-sufficiency

Kume Island, Japan — This island in Okinawa, Japan’s southernmost prefecture, is one-fifth the size of Palau’s largest island, Babeldaob. In spite of its small scale, Kumejima, as it’s known in Japanese, is making a name for itself — not only for its white sandy beaches and balmy weather, but because of its remarkable strides toward creating a self-sufficient island community.

The centerpiece is a unique business project dubbed the “Kumejima Model,” which began with the installation of a deep sea water pipeline in 2003.

Ocean Thermal Energy Conversion demonstration at Kumeijima Island, Okinawa Prefecture, Japan

Thirteen tons of water with a temperature ranging from 8°C to 10°C is pumped daily from a depth of 612 meters (2,007 ft) for several purposes, such as cooling, energy generation, aquaculture and the production of drinking water, salts and cosmetics. The deep sea water facility includes a research station and a deep water tower, from where the water is further distributed.

Some of the ways the water is used include growing spinach year-round, sea grape farming, onshore oyster cultivation, and a shrimp hatchery to provide juveniles for the local shrimp aquaculture. More activities are under research and development. A total value 2.48 billion yen (US$22 million) is generated by deep sea water-related industries.

Kumejima’s economy has diversified by taking advantage of the pipeline. The most famous example is the world-renowned ocean thermal energy conversion (OTEC) technology used to generate electricity. A demonstration facility, which came online in 2013, generates 100 kilowatts of electricity. The only other community with similar technology is in Kona, Hawaii.

OTEC is a renewable method of generating electricity by utilizing the temperature difference between surface and deep sea water. Warm surface water is used to evaporate a low-boiling point liquid – a refrigerant – to create steam, which drives a turbine that generates electricity.

The cost of installing OTEC is sky-high in the initial stages, but officials on Kumejima are taking the long view.

“The 100 kw OTEC was built at a cost of 250 million yen (US$2.2 million),” said Shin Okamura, of the secretariat of the Global Ocean Resource and Energy Association Institute. “But in the long run, the cost savings will pay for itself,” Okamura told a group of Pacific-Caribbean journalists visiting Kumejima.

The project to harness chilled water from the deep sea and its derivative products is inspiring not only from the standpoint of engineering or business. It has also become a major tourist attraction all its own – and a showcase for the island’s green economy.

Kumejima, which received over 120,000 tourists last year, actively promotes its OTEC demonstration center and the other deep sea water facilities in its brochures. Ever since OTEC began operations in 2013, thousands of visitors, including researchers and government officials, have visited to learn more about clean energy and the deep sea water. Palau President Tommy E. Remengesau Jr. has also visited the island to see firsthand the OTEC technology at work.

The Kumejima Model, though a work in progress, doesn’t just generate deep sea water-based products for its economy. Through its goal to be an environmentally friendly community, Kumejima has created a story — a niche product — which is now bringing in tourist dollars into the island economy.

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