[joak]

This boiling temperature conclusion makes the assumption that we continue using thermal power (steam engines, etc...), where waste heat is around 60%.

However photovoltaic and wind does not produce much waste heat. Arguably solar and wind cannot scale 1000x but then you could have non thermal fusion like Helion's https://www.helionenergy.com/technology/.

Btw, thermal power is already showing limits (rivers overheating in summers), we don't have to wait 400 years to see its failure.

[codethief]

> This boiling temperature conclusion makes the assumption that we continue using thermal power (steam engines, etc...), where waste heat is around 60%.

No, it doesn't. The waste heat, at the very end of the day, is always rather close to 100%. I.e. we use all that electric energy we generate to power computer, fridges, and many other machines, all of which – sooner or later – convert that electric energy to heat. (And, well, maybe a bit of chemical binding energy, depending on the application. But then, a few decades later, those products of our work will usually fall apart and/or are being burnt or torn down.)

> you could have non thermal fusion like Helion's

No, you can't. As the author says:

> this statement is independent of technology. Even if we don’t have a name for the energy source yet, as long as it obeys thermodynamics, we cook ourselves with perpetual energy increase.

Free free to have a look at his other article (the one he links in the paragraph above) for some more details -> https://dothemath.ucsd.edu/2011/07/galactic-scale-energy/

[XorNot]

100% of the heat we get from the sun is currently lost as waste heat, by one means or another. So you're not boiling the oceans by any reasonable projection of energy usage increase of solar energy.

(yes yes some of it is reflected back into space as non-IR light, but you can also lose IR-emissions back into space without heating the Earth as well).

[codethief]

Most of that incoming heat is reflected / radiated off actually. It doesn't "stay" on Earth.

https://en.m.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law

[XorNot]

That is literally what I said.

[codethief]

My apologies then, I understood your comment differently!

[midasuni]

Where does the energy go then? EM radiation leaving the planet?

[joak]

Chemical energy. Like the plants, they take sun energy and store it as chemical energy. We could do the same, take CO2 and water and make CH4 and oxygen (electrolysis + Sabatier reaction) and make plastic. Or take ore, aluminum oxide and iron oxide, and "unburn" them releasing again oxygen (we already do that) etc...

We mostly use energy to manufacture things.

Life takes energy and lowers the entropy of the planet. Why shouldn't humans able to do the same? Any technical reason?

[AstralStorm]

There are limits to doing this, which is why we find it really hard to, say, remove CO2 from the atmosphere.

The technical reason is called entropy. Diffuse heat is hard to concentrate and use, much like gas outside of a container.

[codethief]

> Life takes energy and lowers the entropy of the planet. Why shouldn't humans able to do the same? Any technical reason?

Reducing entropy necessarily produces waste energy + entropy elsewhere. So the technical reason this cannot be done at the planetary scale is called Second Law of Thermodynamics.

Yes, we could try to put all that excess entropy & heat into space but there are limits to that (Stefan-Boltzmann law, among other things).