Wave Tank III - The Limpet Gen.
At one end of the tank we have a handle that can be moved up and down to create water waves. At the other end of the tank is a chamber that is only open at the bottom so that the water can freely enter. A passing wave changes the height of the water which in turn compresses the air trapped within the chamber. A rubber sheet covering a hole in the top of the chamber moves in and out in accordance to the pressure change. Attached to this rubber sheet is a device called a piezoelectric transducer that converts this movement into electricity. This little demonstration will just about light a single LED so to make it clearer we have amplified the power to light many LEDs. Commercial systems using similar principles (oscillating water column – OWC) are in operation on the Isle of Islay, Scotland.
This equipment is currently traveling around southern England as part of the "who is going to keep the light on?" SEPnet exhibition for GCSE students. If you go to the events you might like to think about the following:
Things to do: use the handle to create waves but please be gentle so that you don't damage the equipment. You might find that the largest / fastest movement of the handle does not always create the most electricity. Are the quick (short) waves or the slow (long) waves best? Can you see how the waves move the parts of the apparatus that generate electricity? Can you think of anything that might improve the efficiency? What are the limitations of harnessing wave power using this method?
For details of the electrical generators used in these designs please see: 6 gens
SEPnet web site
THE CREATIVE SCIENCE CENTRE
CSC talks and workshops
Dr Jonathan Hare, The University of Sussex
Brighton, East Sussex. BN1 9QJ.
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