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Can Earth's rotation generate power? Physicists divided over controversial claim

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Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#141

Post by kadoban »

bmm6o wrote: post #114
kadoban wrote: post #111

Earlier quoted context omitted.

Are the tides caused by Earth's rotation? My understanding is they're not. I know they're a bit of an inter-related system, but I thought if anything tides mess with rotation (eventually causing tidal lock), not so much the other way around. How big are the solar tides? Never really considered that tbh. Looked it up, they're about half the size of the Lunar ones? Wild.

The short answer is that there would still be tides without rotation, but with a period based on the lunar cycle. We have daily tidal effects, the moon can't do that by itself.

Ah I see, that makes sense. Thanks.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#142

Post by fsckboy »

sroussey wrote: post #86

The Earths rotation already generates power for us: wind. It’s why the jet stream only goes one direction.

a substantial amount of wind is also caused by (differential) solar heating: that's why wind doesn't only go in one direction

if you've ever spent time at the seashore, the wind comes in off the sea during the day (because of rising thermals on the land side) and blows back offshore at night (because the land cools and the sea is now warmer) that time in between the air is dead-still, and that's when the swarms of gnats can find you.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#143

Post by DonHopkins »

SecretDreams wrote: post #55
deepfriedchokes wrote: post #51

Earlier quoted context omitted.

The Navy isn’t constrained by economics. Nuclear doesn’t make sense economically compared to things like solar and batteries.

> things like solar and batteries. Magnets too - let's just go magnets everywhere. Reality is solar isn't viable everywhere. And it's not optimal to put it in places where you use the sun to grow food. We should follow a holistic approach. * Wind where it's windy. * Solar where it's sunny - ideally on buildings/away from farms. * Hydro where possible. * Nuclear where it makes sense, i.e. stable geography, low occuren…

Back when all my precious data was on floppy disk and hard drives, I HATED magnets. Now I am more ambivalent.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#144

Post by mike_hearn »

Certhas wrote: post #132
SecretDreams wrote: post #55

Earlier quoted context omitted.

> things like solar and batteries. Magnets too - let's just go magnets everywhere. Reality is solar isn't viable everywhere. And it's not optimal to put it in places where you use the sun to grow food. We should follow a holistic approach. * Wind where it's windy. * Solar where it's sunny - ideally on buildings/away from farms. * Hydro where possible. * Nuclear where it makes sense, i.e. stable geography, low occuren…

What do you base all these claims on? Plenty of papers show Solar + wind + storage is viable practically everywhere. Also there is a ton of research on planning energy systems and what technology mixes make sense. This stuff has to be economical. Energy costs are measured in percentage of GDP. Simply liking nuclear doesn't make it viable. Especially in a world with PV meaning you can't sell energy during the day. The…

The (subsidized, market dumped) price of cells may be low at the moment, but the price of storage, land and artificial inertia isn't.

You can absolutely sell non-PV power during the day. Big power consumers sign contracts for predictable and reliable supply.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#145

Post by mschuster91 »

Ylpertnodi wrote: post #87
grepfru_it wrote: post #63

Earlier quoted context omitted.

Solve the waste problem and you solve nuclear. Waste is still the giant elephant in the room and a lot of people have a fifth grade solution to the problem (we will bury it under ground! We will fly it to the sun! We will resuse it until it is no longer radioactive!) I used to have a neighbor who worked for the DOE, all of the viable solutions are blocked by people who don’t want it in their backyard. Can’t really mo…

>Waste is still the giant elephant in the room and a lot of people have a fifth grade solution to the problem (we will bury it under ground! We will fly it to the sun! We will resuse it until it is no longer radioactive!) Could the waste be 'sent' into space? Bonus points for sending a certain human with it. Serious question, though.

> Could the waste be 'sent' into space? Bonus points for sending a certain human with it. Serious question, though.

Would you want a RUD of nuclear waste in the atmosphere? That's the key thing with sending stuff to space, we are nowhere near close enough in terms of reliability and cost to what would be needed to send the stuff away.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#146

Post by fsckboy »

golol wrote: post #133
ziofill wrote: post #25

Wouldn't this eventually slow down Earth's rotation? The rotational kinetic energy of our planet is 1/5 M * R^2 * w^2 with (approximately) M = 6e34 kg, R = 6.3e6m, w = 7.4e-5 rad/s, which gives approximately 5e36 joules. Yearly we need roughly 3e16 Wh. Yeah ok there's plenty. Woah! (also, I may be off by some orders of magnitude)

Where does the angular momentum go?

it's the angular momentum that gets transferred to the earth's spin, and all the other numbers, energy, power, are simply how the books are balanced. GP should have asked the question in terms of momentum in the first place.

with energy, you need to consider friction, losses, thermodynamics 3rd law, but with momentum it's pure.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#147

Post by ForHackernews »

MathMonkeyMan wrote: post #43
ziofill wrote: post #25

Wouldn't this eventually slow down Earth's rotation? The rotational kinetic energy of our planet is 1/5 M * R^2 * w^2 with (approximately) M = 6e34 kg, R = 6.3e6m, w = 7.4e-5 rad/s, which gives approximately 5e36 joules. Yearly we need roughly 3e16 Wh. Yeah ok there's plenty. Woah! (also, I may be off by some orders of magnitude)

This is addressed in the last paragraph of the article: > Even if it works, the method will not generate energy from thin air. It would tap Earth’s kinetic energy and, in doing so, cause the planet’s spinning to slow over time — although only slightly. If the technique provided all of Earth’s electricity needs, which was around 11 trillion watts in 2022, this would slow the planet’s spin by 7 milliseconds over the ne…

It's kind of insane how much energy is involved in big masses of rock flying around in space.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#148

Post by mr_mitm »

aeternum wrote: post #81
MathMonkeyMan wrote: post #43

Earlier quoted context omitted.

This is addressed in the last paragraph of the article: > Even if it works, the method will not generate energy from thin air. It would tap Earth’s kinetic energy and, in doing so, cause the planet’s spinning to slow over time — although only slightly. If the technique provided all of Earth’s electricity needs, which was around 11 trillion watts in 2022, this would slow the planet’s spin by 7 milliseconds over the ne…

Isn't friction from the atmosphere already slowing the planet's spin? Many weather effects like hurricanes ultimately derive their energy from a combination of the earth's rotation and thermal/uneven heating effects so I don't see why this is contentions. Like most things, nature is already doing it and has been for millions of years.

No, that's not possible due to conservation of angular momentum. Only tidal effects can transfer some of it to the sun.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#149

Post by bell-cot »

Ylpertnodi wrote: post #87
grepfru_it wrote: post #63

Earlier quoted context omitted.

Solve the waste problem and you solve nuclear. Waste is still the giant elephant in the room and a lot of people have a fifth grade solution to the problem (we will bury it under ground! We will fly it to the sun! We will resuse it until it is no longer radioactive!) I used to have a neighbor who worked for the DOE, all of the viable solutions are blocked by people who don’t want it in their backyard. Can’t really mo…

>Waste is still the giant elephant in the room and a lot of people have a fifth grade solution to the problem (we will bury it under ground! We will fly it to the sun! We will resuse it until it is no longer radioactive!) Could the waste be 'sent' into space? Bonus points for sending a certain human with it. Serious question, though.

By "space" do you mean low earth orbit - where the stuff will reenter the atmosphere within (say) a century? Or geosync orbit - where it'll stay up there forever-ish...but ain't actually gone? Or actually gone, like (say) Mars?

IIR, the current rock-bottom (Falcon 9) launch prices are something like $1,000/lbs. to low earth orbit, $2,500/lbs. to geosync, and $6,500/lbs. to Venus.

A quick Google says the US has about 88,000 tons of radioactive waste. So - 88,000 tons = 176,000,000 lbs. = $176,000,000,000 just to put it in low earth orbit. And something like 4,600 Falcon 9 launches. (Some fraction of which would doubtless go badly wrong, spreading radioactive stuff all over the landscape.)

In short - it's a cool-sounding idea. But neither the numbers nor the politics are remotely near viable.

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