Science Forums 2

[Boerseun]

Harvesting power from the Moon is easy.

Build a large, shallow dam close to a spot at the coast where the tidal difference is pretty high.
Let high tide fill your dam, and at low tide let the water empty again through an array of turbines.
Because the drop won't be far enough to really make it worthwhile in terms of output, you need a heck of a big dam with a helluva lot of turbines.

But that, in effect, will be tapping energy from the Moon.

Maybe there's some desert somewhere that's useless for anything else that can be converted into a huge tidal reservoir, but the energy input in emptying the hundreds of square miles of sand required for your dam will probably nullify the output from your dam, which'll have only a few meters' drop, usable only for a couple o' hours every day.

Bad idea.

A much better idea will be to have cheap, erosion-resistant (say, carbon-fibre or fibreglass) turbines dropped in the sea.

Imagine:

They're lighter than water, so they wanna float. If not, attach the necessary floats. Then you add an anchor (say, a cheap block of concrete) to it, strung to a cable so that you can set the required height off the seafloor, and have a generator attached to two counter-rotating turbines (so as torque isn't an issue) with a vertical and horisontal stabiliser (like a plane's tailplane) so that they'll always be facing the stream. Obviously, your turbines should be pretty big, 'cause they'll turn only as fast as the stream is moving. But you have a step-up gearbox at your generator, so the generator will be turning at a fair clip.

And then, you dump hundreds of these suckers into the sea where there's a strong stream. I'm talking Agulhas current, the Gulf Stream, places where the global streams are bottlenecked, like Cape Horn, south of Cape Agulhas, between North and South Islands in New Zealand, Hokkaido in Japan - there's plenty places.

Then you waterproof a couple of sturdy cables, connect them all together, and run the current to the nearest land where you've got distribution centers, etc. The technology developed with undersea intercontinental phone cables suggest that this won't be too much of a hassle.

There's more than enough torque in seawater travelling at a few kilometers per hour to make that gennie spin at thousands of RPM with a proper gearbox included. And this can be done so cheap that in my mind, it really makes for a strong contender in the future energy game. If the output of an individual generator is relatively small, so what? Go with the economy of scale! Chuck in thousands more! They're cheap!

You need to buy ZERO land for this, there's ZERO polluting, it's out of sight, ceramic bearings can be utilized so that there'll be minimal failure and minimal maintenance, it's predictable - at a wind farm, you're stuffed when the wind stops. At a solar collection plant, you're stuffed when the sun sets. Using this, you have energy 24/7, which is actually just solar energy, but with much higher, more usable torque than what wind gives you. And those streams I mentioned runs 24/7, come rain, sleet or snow... At night, during the day, winter, summer, they just keep on chuggin'.

The input making the world's oceans churn, is the sun. The same input for wind. But wind is flaky, weak energy density, and windfarms spoils the scenery, apart from using up acres of land.

This, to me, makes sense. Much more so than nuclear-, coal- oil- or gas-fired power plants. Or many of the proposed alternatives, for that matter.