We think that radioactive heat generation could be 20-30 TW. Remember: 1 TW = 1000 GW, or 1,000,000 MW. For context, the *world* current has about 8.5 TW of electricity. 4/X - ThreadSky

petemassie.bsky.social • 79 days ago

We think that radioactive heat generation could be 20-30 TW.

Remember: 1 TW = 1000 GW, or 1,000,000 MW.

For context, the *world* current has about 8.5 TW of electricity. 4/X

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laughlax.bsky.social•79 days ago

Huh, put that way it actually makes the amount of radioactive heat created seem kind of small to me. Or usage seem large?

Not that we'd ever replace all of the world's electricity generation with geothermal, of course... But it makes me very thankful that we have other clean sources available too.

petemassie.bsky.social•79 days ago

This is an interesting point, and something I'm digging in to.

20-30TW is a flow of heat generation, but this =/= stock of available thermal energy.

Agree we need all the available clean energy sources and will share some figures on the stock of heat soon

dvschroeder.bsky.social•79 days ago

The average heat flux is obviously far too small to be useful.

Geothermal power inevitably depends on some combination of mining stored energy and/or finding hot spots where the flux is much greater than average.

I don't have good intuition for how far either approach can scale up.

laughlax.bsky.social•79 days ago

Idk the source of the gen capacity table you snipped above, but as it's nameplate capacity there's definitely slack in that 8.5 TW number (esp. in that 3.3 TW of renewables). For apples to apples, I'd look for actual electricity generated and compare against 20-30 TW x 8760 hr.

laughlax.bsky.social•79 days ago

All of this also leaves out non-electric energy use, but that's a whole can of worms itself since replacement electric technology can often use less primary energy than the non-electric counterparts (e.g. EV vs ICEV, or heat pump vs furnace).

petemassie.bsky.social•79 days ago

Absolutely - capacity data is from the US EIA.

It's a poor proxy for generation, but something quick that's in the same units.

Totally agree on the primary energy issue. What we really have today is a waste system, with useful energy as a byproduct.

wiilp.bsky.social•79 days ago

Agree with the viewpoint, but remembering that geothermal electricity also has low conversion efficiency, often less than 20%. (Carnot strikes again!)

So you gather 5 W of geo heat, make 1 W of electricity and 4 W of rejected heat.

This might not matter! Or can use geothermal for heating instead.

wilson-energy.bsky.social•79 days ago

So basically, geothermal is a much safer form of nuclear energy? #EnergySky

petemassie.bsky.social•79 days ago

I've always thought of geothermal and nuclear energy as cousins - challenging to make an apples to apples comparison between natural radioactive decay and artificially designed fission.

Except for that one time the Earth spawned a natural nuclear reactor:

https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

petemassie.bsky.social•79 days ago

Of course, individual projects still need to manage local conditions.

But we don’t have to worry about freezing the Earth.

The Earth generates massive amounts of new heat every day and will for millions of years. 5/5

🔌💡

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