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

nature.com

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

#161

Post by cyberax »

qnleigh wrote: post #157
cyberax wrote: post #108

Earlier quoted context omitted.

> 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!) The correct solution: put it into dry casks and do nothing right now. Store it simple underground storage facilities or on the grounds of active nuclear power plants. The casks are fine for the nex…

> use rockets to slowly launch the waste into space. We can already design a storage capsule that can survive re-entry. Do you have a source in mind for this claim? Even if a capsule could survive reentry, surely it wouldn't survive impact.

Yes. We're _already_ launching nuclear waste into space, in the form of RTGs with Pu-238. So there's been a lot of work towards making them passively safe, although the weight constraints for deep-space craft necessarily limit the amount of achievable safety.

> Even if a capsule could survive reentry, surely it wouldn't survive impact.

It'll be moving at a terminal velocity, and can be engineered to not fragment on impact.

For example, I remember reading about a proposal to alloy the nuclear waste elements with a carrier metal like iron or nickel, and then cover them in an ablative graphite shell.

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

#162

Post by incognito124 »

DriverDaily wrote: post #130
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)

Can we put energy in to speed it up? That way a day can be 24 hours exactly instead of 23 hours, 56 minutes, 4 seconds, etc...

I mean, solar day is 24h, it's the sidereal day that's 23.9344696h

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

#163

Post by maxerickson »

cyberax wrote: post #161
qnleigh wrote: post #157

Earlier quoted context omitted.

> use rockets to slowly launch the waste into space. We can already design a storage capsule that can survive re-entry. Do you have a source in mind for this claim? Even if a capsule could survive reentry, surely it wouldn't survive impact.

Yes. We're _already_ launching nuclear waste into space, in the form of RTGs with Pu-238. So there's been a lot of work towards making them passively safe, although the weight constraints for deep-space craft necessarily limit the amount of achievable safety. > Even if a capsule could survive reentry, surely it wouldn't survive impact. It'll be moving at a terminal velocity, and can be engineered to not fragment on i…

The Pu-238 in Rtgs is produced for the purpose, it isn't isolated from waste.

Of course it is more or less equivalent when it comes to handling.

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

#165

Post by sitharus »

qnleigh wrote: post #155
api wrote: post #84

Earlier quoted context omitted.

I was about 99.99999% sure that one was bogus because it was violating bedrock conservation laws. I'm not sure that this does. AFAIK there is no conservation law that says a spinning mass can't extract power from that. Still... it would have been hilarious of the EmDrive had worked. "Well, they've progressed! Last time we checked in on the third planet in this star system its inhabitants were still using warp drives…

Well conservation of energy says you can't extract energy out of nowhere. In the paper they claim that the extracted energy comes at the price of slowing down Earth's rotation. But then this seems to violate conservation of angular momentum... Maybe it depletes Earth's magnetic field instead?

Conservation of angular momentum doesn’t prohibit reducing angular momentum by extracting energy, in this case the angular momentum is converted to electricity.

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

#166

Post by pfdietz »

mr_mitm wrote: post #70
1970-01-01 wrote: post #67

A bad question, as it has been doing that literally (rotationally) since before life started. This power is busy generating the magnetosphere. We would not be enjoying our nice oxygen atmosphere and would be as dead as Mars if Earth's rotation wasn't also powering a dynamo.

It doesn't take any energy to maintain a static magnetic field though.

The currents that produce the magnetic field are flowing in liquid metal with nonzero resistivity.

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

#168

Post by codethief »

sitharus wrote: post #165
qnleigh wrote: post #155

Earlier quoted context omitted.

Well conservation of energy says you can't extract energy out of nowhere. In the paper they claim that the extracted energy comes at the price of slowing down Earth's rotation. But then this seems to violate conservation of angular momentum... Maybe it depletes Earth's magnetic field instead?

Conservation of angular momentum doesn’t prohibit reducing angular momentum by extracting energy, in this case the angular momentum is converted to electricity.

You can't just trade (angular) momentum for energy or vice versa, those are independent conservation laws.

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

#169

Post by abdullahkhalids »

pmontra wrote: post #54
EncomLab wrote: post #45

It's incredible the lengths humanity is willing to go to avoid adopting nuclear energy - despite the US navy driving mobile reactors millions of miles over the last 70 years.

Many countries would have to buy nuclear fuel from other countries much like they do for gas and oil. On the other side very few countries can build their own solar panels so it seems the same sort of problem. However if you accept to depend from potential hostile countries at least solar panels don't do much harm when they fail and it takes very little effort to install the equivalent amount of power of a nuclear po…

Most country that can invest a few hundred million can build their own solar panels that will be significantly cheaper than existing and future fossil fuel prices. It's just those panels will be 2x+ the price of those produced in China. So can't compete in the free market.

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

#170

Post by Jensson »

mr_mitm wrote: post #148
aeternum wrote: post #81

Earlier quoted context omitted.

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.

Tidal effects mostly transfers it to the moon, the sun has almost no tidal effects.
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