from: redorbit.com


Turning Pacific Ocean Water into Potable Water

Japanese technology may help Pacific islands meet fresh water demand

KYOTO, Japan (AFP) -- A number of Pacific island nations are eyeing new Japanese technology that can both desalinate sea water for drinking and produce electricity by exploiting the difference in temperatures between the surface of the sea and the depths of the ocean.

The Republic of Palau in western Pacific is working with Saga University in southern Japan to construct a system that can produce enough drinking water to meet the needs of its 20,000 residents, while producing electricity, said Palauan President Tommy Remengesau, Jr.

The concept was highlighted this week at one of the 350 sessions at the Third World Water Forum under way here that has attracted 10,000 participants from around the globe, along with ministers and state heads from more than 150 countries.

The university is preparing to build an experimental power plant off the coast of Palau that brings up cold sea water from deep sea to an evaporator chamber near the ocean surface.

As the water is heated up by the surrounding warm surface water it releases ammonia gas that drives the system's power generator, said Yasuyuki Ikegami, deputy director of the Institute of Ocean Energy at Saga University.

Meanwhile, the heated water would be transferred to a separate low-pressure chamber where it boils at a lower temperature, producing steam, which would be condensed and collected as fresh water for human consumption, leaving salt crystals behind.

One experimental system, which only produces power and no water, is scheduled to be launched off the coast of India this month, Ikegami added.

"It works well especially in the western Pacific, where the temperature difference between the ocean's surface and deep seawater is as much as 24 degrees C (Celsius, 43 degrees Fahrenheit)," Ikegami said.

"It is environmentally sound."

With some financial assistance from the Japanese government, the university was hoping to build the experimental plant in Palau for an estimated 900 million yen (7.5 million dollars), said Haruo Uehara, president of Saga University, although he declined to disclose details of the financing as it is still being negotiated.

Palau was hoping to see the plant built next year, Remengesau added.

"It is a big help for us. When there is rain, we have no problem. But we are hit by the drying effects of El Nino. When there is no rain, where can we get drinking water?" the Palauan president said.

The fresh water produced by the system costs less than one dollar per one cubic meter, once the system is up and running, Uehara said.

"It is no more costly than regular tap water in other countries, including Japan," Uehara said.

The system, while more expensive than ordinary generators, has raised hopes among leaders of other Pacific islands, which are too small to build many dams to catch water and are trying to cut back on their consumption of oil to run power generators.

Allan Marat, deputy prime minister of Papua New Guinea, said Pacific island nations had fallen victim to global warming, adding that he too was interested in the university's system.

"We are in the middle of the largest body of water (on earth). Yet, we are faced with lack of safe potable water," said Robert Woonton, prime minister of the Cook Islands.

He said he wanted to consider setting up Saga University's system in his country.

Other countries in arid zones have also shown interest, including Saudi Arabia, which was sending a delegation to the university, said Uehara.

"We believe this can solve many problems in island countries and other countries with special needs," Uehara said.