CRI听力:Blue Energy

Have you ever heard of blue energy? Dutch scientists are developing a project that, if successful, could create sustainable energy from the difference in salinity between fresh and salt water. Our reporter Huangrui has more.



At the port of Rotterdam, fresh and salt water flow together. It has inspired scientists at Wetsus, the Dutch Centre for Sustainable Water Technology, to develop an innovative sustainable energy project. But that's not a new thing: in 1950, scientists Sidney Loeb and Srinivasa Sourirajan from California University found the way to extract drinking water from sea water.

About 15 years later, when Loeb was working at the University of the Negev in Israel, he realized that this process, which is called reverse electrodialysis, can also produce electric power. Loeb created a simulator in order to prove the concept and patented the idea in 1973. He was hoping that such a system could harvest power in locations where fresh water meets sea water. After revisiting the concept, the scientists at Wetsus have developed this breakthrough idea and called it the Blue Energy concept.(www.hXen.com)

To test the theory, they've created a simulator with three components: tanks with salt and fresh water, each connected with tubes to a special unit of membranes, and finally a glass tank of water enriched with electrons to start up the chemical process in the membranes. The simulator proves that when sweet and salt water join, the concentration will diffuse until the salinity is equal in the total fluid. When a selective membrane is placed between sweet and salt water, this diffusion can be controlled and potential energy gained.

Joos Veerman is the head of the Wetsus research team. He recognizes that his team is facing the same problem that Loeb was 30 years ago: how to find suitable and cost-effective membranes.

"We have to optimize everything. For example we have to optimize the space in between the membranes. Between the membranes the water streams and we have 'spacers' in between. And the conditions are that, on one hand, these 'spacers' have to be very thin so that the electrical resistance is as little as possible, on the other side we have to see to it that they are very open so that the water can pass through the membranes."

Wetsus' feasibility studies have come to the conclusion that river deltas, with the availability of sweet and salt water, make for the most suitable locations for Blue Energy. The optimal location would be the 20-mile-long causeway of Afsluitdijk.

The Afsluitdijk was constructed in part to dam off the Zuiderzee inlet of the North Sea, turning it into the massive freshwater lake of the IJsselmeer. The lake is periodically discharged since it is continually being fed by rivers and streams, which makes it an ideal location for the saltwater power plant.

The principle is clear. The system works well in the lab, but the question is whether it will work in reality.

If it does, Wetsus estimates that the Blue Energy technology could produce 3000 milliwatts in the Netherlands, covering almost one-third of the total Dutch annual energy consumption.

For China Drive, I'm Huang Rui.