Actually pretty cool - I was about to comment “nice perpetual motion machine” but looked into a bit more and it’s much more interesting than that (well, a real perpetual motion machine would be interesting but…)

Thanks for posting. Pretty cool.

> but then lets the waste heat just pour out

There is no other alternative! If I build a perfect Dyson sphere and capture the energy output of a star, all of that energy will become heat. The average surface temperature of my Dyson sphere will be (IIRC) the ratio of the surface area of the sphere to that of the contained star, multiplied by the star's effective surface temperature.

"Recovering heat and making use of it" requires a heat differential. You need a cold side and a hot side to use energy. Using that energy causes the cold side to heat and the hot side to cool, until they reach equilibrium. The further the difference, the more usable work you can do. The closer the two sides are, the less work you can do.

Someone else here said it best: waste heat is the graveyard of energy. Once you have used energy, it will become high-entropy, low-grade, diffuse heat which is difficult-to-impossible to extract further work from.

All energy inevitably changes into heat eventually, and in the steady state, power in = power out.

There is no way to get rid of heat. It has to go somewhere; otherwise, the temperature of the system will increase without bound.

These days it's not rare to have data center heated buildings. I guess crypto bros are just not thinking about this. But technically if could be done there too.

You can say that about any waste heat.

In really, it’s not convenient to move all waste heat to where it’s more needed.

Heat is the graveyard of energy. Everything that uses energy, or is energy, is actually just energy on it's way to the graveyard.

The energy of the universe is a pool of water a top a cliff. Water running off this cliff is used to do stuff (work), and the pool at the bottom is heat.

The "heat death of the universe" is referring to this water fall running dry, and all the energy being in this useless pool of "heat".

Almost none. A long time ago a friend and I did the math for sound, photons (status LEDs), etc and it was a rounding error of 1% or something silly like that.

And that’s ignoring that sound and photon emissions typically hit a wall or other physical surface and get converted back to heat.

It all ends up as heat in the end, just depends on where that heat is dumped and if you need to cool it or not. Most watts end up being even more than the theoretical heat per watt due to said cooling needs.

There is literally no way around the fact that every watt you burn for compute ends up as a watt of waste heat. The only factor you can control is how many units of compute you can achieve with that same watt.

All sound will end up as heat.

If I use energy to move a block one foot over, I have performed useful work. But 100% of the energy used to perform that work is either already heat or shortly will be.

Even if most of the energy goes into kinetic energy of the air, that air will lose momentum via turbulence and friction with the surrounding air, which will end up as... heat.

While spinning, the blades store a miniscule amount of kinetic energy.

After removing power even that small amount ends up as heat through friction ( both in the bearing but mostly in the air turbulence). And the blades end up in the same zero energy state: sitting still.

So it is correct that a 100% "end up" as heat

That's not correct. For ordinary computers there is Landauer's principle, which gives a theoretical lower limit for the energy needed for computation [0].

I say "ordinary computers" because other comments mentioned "reversible computers" for which this limit doesn't apply.

According to the linked wikipedia page, this theoretical limit is around a billion times smaller than current computers use for an operation, so you may call me pedantic.

[0]: https://en.wikipedia.org/wiki/Landauer%27s_principle

it's called the first law of thermodynamics

The minimum amount of energy needed to compute decreased asymptotically to 0 as the temperature of space goes to 0. This is the reason a common sci-fi trope where advanced civilizations hibernate for extremely long times so that they can do more computation with available energy.

Good luck with collecting that heat from air.