Japan tested a giant turbine that generates electricity using deep ocean current

Re:Japan tested a giant turbine that generates electricity u... by jameshart on Saturday June 04, 2022 @06:55PM (#31625924)

Tidal flows are a pretty massive energy reservoir - basically you’ve got all the potential and kinetic energy of the moon’s orbit to draw from. That’s (according to my crude Wolfram Alpha based research) about 3e28J of kinetic energy plus 7e28J of potential energy, for a total of 10^29 Joules. Technically a non renewable resource, but you would be hard pressed to make a dent in that energy budget with any kind of human scale extraction project.

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Re:Japan tested a giant turbine that generates electricity u... by hinoki on Saturday June 04, 2022 @08:05PM (#31626505)

I think it’s the rotational inertia of the earth, not the kinetic energy of the moon. Since the earth is spinning faster than the moon orbits, the tides actually are pulled ahead of the bulge the moon creates, transferring energy from the earth to the moon.

Eventually the earth will be tidally locked to the moon (just like the moon is to the earth), and the moon will be in a higher orbit.

I guess the turbines will speed this up? As they’ll keep the bulge farther ahead of the moon.

EDIT: Wikipedia link https://en.m.wikipedia.org/wiki/Tidal_acceleration

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Re:Japan tested a giant turbine that generates electricity u... by jameshart on Saturday June 04, 2022 @09:21PM (#31626971)

That's true - for some reason I was thinking of tides as following the moon's orbit, when of course they're caused by the earth spinning underneath the moon (tides occcur daily, not monthly. Always check your working against reality, kids).

Weirdly, the resulting pool of energy is pretty much the same size - wikipedia quotes the rotational kinetic energy of the Earth as being 2.138E29J.

So we're still talking about an insane amount of energy.

If you use 17.7TW as the total power consumption of all of humanity, if we were to somehow derive ALL of our energy needs from tidal generation, it would take 358 million years to deplete the rotational energy of the earth.

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Re:Japan tested a giant turbine that generates electricity u... by usrusr on Sunday June 05, 2022 @04:51AM (#31629162)

Would the turbines make the rotation decay faster, or would they just put some of the energy of rotation decay that happens anyways on a slightly different path towards heat?

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Re:Japan tested a giant turbine that generates electricity u... by narag on Saturday June 04, 2022 @07:59PM (#31626451)

Technically a non renewable resource...

How's that? Can we consume it? What would be the reaction? Moon altering its orbit?

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Re:Japan tested a giant turbine that generates electricity u... by andkenneth on Saturday June 04, 2022 @08:04PM (#31626503)

Yes this technically degrades the moons orbit. Do it long enough and hard enough and the moon will hit the earth. Shouldn't be of any concern though, because the kinetic energy the moons movement is carrying is insanely high.

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Re:Japan tested a giant turbine that generates electricity u... by stjohnswarts on Sunday June 05, 2022 @04:54PM (#31634753)

This doesn't degrade the moon's orbit lol. The energy is there regardless of whether we are using it or not, it will go somewhere, this is just making "useful" work out of it (if anything humans do to the environment, other than going extinct, is really value added for the environment)

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Re:Japan tested a giant turbine that generates electricity u... by lazugod on Saturday June 04, 2022 @11:26PM (#31627731)

Huh. Would Ice 9 also make the moon crash?

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