Scientists hoping to create clean energy along Portuguese coast

December 17th, 2008 - 5:14 pm ICT by ANI  

Washington, December 17 (ANI): Researchers at the Massachusetts Institute of Technology (MIT) have joined forces with Portuguese scientists to create a pilot-scale device that will capture significantly more energy in ocean waves than existing systems.
The researchers say that their objective is to use such a device to power an electricity-generating turbine.
Chiang Mei, the Ford Professor of Engineering in the Department of Civil and Environmental Engineering, has developed numerical simulations that can predict wave forces on a given device and the motion of the device that will result.
He says that the simulations guide design decisions that will maximize energy capture, and provide data to experts looking for efficient ways to convert the captured mechanical energy to electrical energy.
Given that Portugal is a country with a good deal of expertise in wave energy research and development, he has joined collaborated with researchers at Technical University of Lisbon.
The researchers want to design a pilot-scale version of a facility called an oscillating water column (OWC) situated on or near the shore, which consists of a subsurface opening.
The level of water inside the chamber goes up and down as waves come in and out, and the moving surface of the water forces air trapped above it to flow into and out of an opening that leads to an electricity-generating turbine.
The turbine has been created in such a manner that its blades always rotate in the same direction, despite the changing direction of the air stream as the waves come in and out.
The Portuguese plan to integrate the OWC plant into the head of a new breakwater at the mouth of the Douro River in Porto, a large city in northern Portugal. The installation of three OWCs is expected to generate 750 kilowatts, roughly enough to power 750 homes.
Mei says that the challenge before his team is to design a device that resonates, and thus operates efficiently at a broad spectrum of wave frequencies.
He has revealed that an unexpected finding from the MIT analysis provides a means of achieving that effect. The key is the compressibility of the air inside the OWC chamber, he adds.
The researcher says that the compressibility cannot be changed, but its impact on the elevation of the water can be simply by changing the size of the OWC chamber.
The simulations he and his colleagues have created show that using a large chamber causes resonance to occur at a wider range of wavelengths, so more of the energy in a given wave can be captured.
“We found that we could optimize the efficiency of the OWC by making use of the compressibility of air something that is not intuitively obvious. It’’s very exciting,” Mei says.
Mei and his colleagues are presently working in collaboration with other graduate students on wave power absorbers on coastlines of different geometries, and on how to extract wave power from an array of many absorbers.
The researcher, though very enthusiastic about wave energy, thinks that it is unlikely to be commercially viable for a long time.
He, however, still insists that more attention should be given to this renewable source of energy.
“Given the future of conventional energy sources, we need lots of research on all kinds of alternative energy. Right now, wind energy and solar energy are in the spotlight because they”ve been developed for a longer time. With wave energy, the potential is large, but the engineering science is relatively young. We need to do more research,” he says. (ANI)

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