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Even if the computer does perfectly-efficient computer things with every Joule, every single one of those Joules ends up as one Joule of waste heat. If you pul
by stouset 10mo ago
Even if the computer does perfectly-efficient computer things with every Joule, every single one of those Joules ends up as one Joule of waste heat.
If you pull 100W of power out of an electric socket, you are heating your environment at 100W of power completely independent of what you use that electricity for.
- robkop 10mo agoInteresting question - how much will end up as sound, or in the ever smaller tail of things like storing a bit in flash memory?
- phil21 10mo agoAlmost 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.
- Terr_ 10mo agoWell, at least until somebody devises a system that transports or projects it so that the heat ends up somewhere not-Earth. It'd still be heating the universe in general, of course, even in the form of sprays of neutrinos. That reminds me of a sci-fi book, Sundiver by David Brin, where a ship is exploring the sun by firing a "refrigerator laser" to somehow pump-away excess heat and balance on the thrust.
- mrDmrTmrJ 10mo agoAll sound will end up as heat.
- Workaccount2 10mo agoHeat 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".
- devsda 10mo agoDo thermophotovoltaic cells operate on different kind of heat? Is it impossible to convert heat into other forms of energy without "consuming" materials like in the case of steam, geothermal or even the ones that need a cold body to utilize thermoelectric effect.
- LiamPowell 10mo agoTPVs don't rely solely on the temperature of an object being high, they instead rely on two objects on either side having different temperatures. As heat moves[1] from one side to the other some of the energy from that movement is turned in to electricity. [1]: Technically the movement itself is heat, the objects don't contain heat, rather they contain internal energy, but the two get mixed up more often than not.
- supermatt 10mo agoThat movement is effectively “consuming” the differential.
- ajuc 10mo agoWhat thermal energy sources actually exploit is temperature difference, not heat. And in the end that difference averages out.
- thegrim000 10mo agoI read it as the inefficient part isn't the compute efficiency, the inefficient part is dumping all the resulting heat into the environment without capturing it and using it in some way to generate electricity or do work. On a related/side note, when there's talk about seti and dyson spheres, and detecting them via infrared waste heat, I also don't understand that. Such an alien civilization is seemingly capable of building massive space structures/projects, but then lets the waste heat just pour out into the universe in such insane quantities that we could see it tens/hundreds of light years away? What a waste. Why wouldn't they recover that heat and make use of it instead? And repeat the recovering until the final waste output is too small to bother recovering, at which point we would no longer be able to detect it.
- oasisaimlessly 10mo agoAll 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.
- thegrim000 10mo agoFor example, why couldn't you use the waste heat like a power plant? Use it to boil water, to turn turbines, to generate electricity, which gets sent and consumed elsewhere? Adding to the heat wherever the electricity is finally consumed. (Ignoring various losses along the way).
- stouset 10mo ago“Elsewhere” is still somewhere on the Dyson sphere. Or if you magically beam 100% of the captured energy somewhere else, now that place gets to deal with shedding the heat from however many 1e26W+ of power were consumed. God help the poor planet you aim that ray of death at.
- stouset 10mo ago> 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.
- spyder 10mo agoOnly true for our current computers and not true with reversible computing. With reversible computing you can use electricity to perform a calculation and then "push" that electricity back into a battery or a capacitor instead of dumping it to the environment. It's still a huge challenge, but there is a recent promising attempt: "British reversible computing startup Vaire has demonstrated an adiabatic reversible computing system with net energy recovery" https://www.eetimes.com/vaire-demos-energy-recovery-with-reversible-computing-test-chip/ https://www.eetimes.com/vaire-demos-energy-recovery-with-rev... https://vaire.co/ https://vaire.co/ Short introduction video to reversible computing: https://www.youtube.com/watch?v=rVmZTGeIwnc https://www.youtube.com/watch?v=rVmZTGeIwnc
- flave 10mo agoActually 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.
- tatjam 10mo agoThis kind of stuff could trigger the next revolution in computing, as the theoretical energy consumption of computing is pretty insignificant. Imagine if we could make computers with near-zero energy dissipation! A "solid 3D" computer would then become possible, and Moore's law may keep going until we exhaust the new dimension ;)
- tasuki 10mo ago> every single one of those Joules ends up as one Joule of waste heat. Yes it ends up as heat, but with some forethought, it could be used to eg heat people's homes rather than as waste.
- TheSpiceIsLife 10mo agoYou can say that about any waste heat. In really, it’s not convenient to move all waste heat to where it’s more needed.
- tremon 10mo agoIt's always more convenient to ignore externalities. That doesn't mean we should be okay with only bottom-of-the-barrel solutions.
- m4rtink 10mo agoModern industrial scale insulated hot water district heating systems can do dozens of kilometers with the water cooling down only by a degree Celsius.
- agumonkey 10mo agoThese 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.
- KellyCriterion 10mo agoThere was a startup in EU which explicitly sold heat from crypto mining to the local energy provider. IIRC it was also here on hacker news some time ago.
- agumonkey 10mo agoQarnot maybe
- usrnm 10mo agoIf I turn my fan on and 100% of the electricity is converted to heat, where does the kinetic energy of moving fan blades come from? Even the Trump administration cannot just repeal the law of conservation of energy.
- jo909 10mo agoWhile 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
- usrnm 10mo agoMost of that energy gets transfered to the air that's being moved by the blades, and who knows what that air does eventually. And we're not even talking about the plant growing light that might be sitting in my room near my house plants literally creating new life from electricity.
- stouset 10mo ago> who knows what that air does eventually We do know what that air does eventually. Given no further inputs of energy, it swirls around generating friction, raising its temperature (heat!) as the currents slow down to nearly nothing.
- numb7rs 10mo agoEven 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.
- anthonj 10mo agoThis violates energy conservation principles. Some power will be "wasted" into heat, some other will be used for some other work.
- stouset 10mo agoIf 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.
- anthonj 10mo agoIf you launch a rocket at escape velocity the momentum and potential energy you create never dissipates. Certain chemical reaction endotermic reaction require energy to start. This energy is absorbed to generate molecular bond. Also in the generation and absorption of high energy radiation there are non-thermal processes that can transfer energy. Even something like bending a metal bar is not 100% a thermal process.
- csomar 10mo agoTheoretically, if your computation is energy efficient, you won't need any electricity at all since the real computation costs zero energy.
- majoe 10mo agoThat'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 https://en.wikipedia.org/wiki/Landauer%27s_principle