Friday, May 9, 2008

Idea: Wave power without moving parts

When I was an undergraduate in applied physics, I had this idea about using the conductive and dielectric properties of sea water to convert wave motion directly into electricity. I recently googled the topic and came up naught. (May be because it's a bad idea?)

Any way, the idea comes from 2 observations about capacitors.
  1. It takes work to slip out a dielectric slab sandwiched between charged capacitor plates.
  2. It takes work to increase the distance between charged capacitor plates.
Now if we can set up a large scale capacitor with the ground plate placed horizontally underwater, close to sea wave troughs and the "positive" plate well above wave crests, and a suitable timing mechanism to apply and draw voltage to and from the capacitor as the wave enters and leaves the contraption, then some of the wave power can be converted to electricity.

You don't actually need capacitor plates: a mesh of conductive wires should suffice. The power generated by such a contraption is proportional to the area of sea surface covered. But because of its simple design (all the smarts and expensive parts can be centralized), it should scale well.

Numbers? I'll try to add a back-of-envelop calculation, later..

Addendum: 3-20-2010

I'm beginning to think this might not work as decribed. Even if it did, from a practical standpoint, the wires would soon be covered with debris, barnacles or other insulating stuff. A better approach might be to create a giant, barely floating, sealed "waterbed" filled with a suitable dielectric liquid. Two wire meshes spanning the top and bottom walls of the bed from the inside would be used to create the effect of an array of capacitor plates. A component of the [gravity] wave hitting the side of this bed would continue to propagate through this bed, creating a moving bulge through it as it passes. As before, an adaptive control mechanism would time a voltage increase across the cascading, virtual capacitor plates ahead of the approaching bulge and draw power as the wave leaves the region.
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