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From the article: > It is estimated that about 70 percent of the energy generated worldwide ends up as waste heat. This has me a bit confused and I’m curious

• tsimionescu 2y ago
  No, lots of energy goes into moving large things around. Energy that goes into doing work (as in the physical quantity work) doesn't become heat.
  • thanksgiving 2y ago
    I thought the question was limited to a "solid state"[0] computer processor. There is no "useful work" moving large things on a computer processor. In this context, 100% of the energy consumed by a computer processor is heat, right? At least I think that is the working assumption when we build CPU cooling. If a processor consumes 15W of electrically power, we better have some way to move this 15W of heat away from the processor, right? I have another question, for a light bulb, is this still the case? I guess for a candle or an incandescent light bulb, the question is moot but as we have more and more efficient lights like the "cool" LED lights, if the light source consumes 15W of electricity, do we need 15W of cooling? [0] not a technical term
    • ainoobler 2y ago
      You are correct. All the electron motion in a CPU turns to waste heat or electromagnetic radiation which eventually becomes waste heat.
    • tsimionescu 2y ago
      I don't think the question was in the context of computers or even electronics in general, as the original claim cited ("70 percent of the world's power production ends up as waste heat") was certainly not restricted to computing. In the context of CPUs, yes, the heat produced is equal to the input power. However this is not at all true for light bulbs, for motors, for battery chargers, etc. A light bulb in particular transforms some of the electrical energy into heat, but some of it into emitted light. Even in incandescent bulbs, some the electricity gets turned into heat, raising the temperature of the filament, but past some point, the temperature no longer increases and all the extra energy gets converted into light. That is, if you were to submerge an incandescent light bulb in a large quantity of water and leave it on for 10 minutes, you'd get cooler water than if you submerged just the filament (ignoring the possible shortcircuits): if the temperature of the filament is kept below the point where it emits light, than all the electrocity goes into heat; but if it starts emitting light, then some of the energy escapes and doesn't heat the water.
      • ainoobler 2y ago
        The electromagnetic radiation still turns to waste heat.
        • tsimionescu 2y ago
          Not necessarily, it can also turn to motion or to electricity or to chemical processes or to other things. For example, if you're using the light bulbs to light plants, it gets turned to sugar, not to heat.
          • thanksgiving 2y ago
            I googled LED light efficiency what percentage of electricity becomes heat and looks like only about 20% of the input is wasted as heat? So a 15W LED light would only need 3W of cooling? It feels even more ridiculous when we put the numbers like this... There is no excuse for LED lights to not have adequate cooling or for them to fail because of overheating... > This means that about 80 percent of the electrical energy is converted to light, while 20 percent is lost and converted into other forms of energy such as heat.
            • sharpshadow 2y ago
              Light bulbs are build to break and be replaced, as far as I understand we could have eternal light bulbs but that’s not in the interest of light bulb makers. That same logic might still apply for modern light solutions like LEDs. I have a more expensive LED bar which is build on top of aluminium to disperse the heat. Did you have heard about the Dubai Lamp? It’s basically a very efficient longlife LED which they only sell in UAE.
              • daveguy 2y ago
                The Dubai Lamp is produced by Phillips, and is about 3x more efficient than typical LED bulbs -- normally 9w for 60w equivalent vs 3w. Their rated life is 25,000 hours, which is 2.5x longer than a typical 10,000 hour led. They are damn impressive, but not "forever". https://www.mea.lighting.philips.com/consumer/dubai-lamp https://www.mea.lighting.philips.com/consumer/dubai-lamp
• MathMonkeyMan 2y ago
  Eventually, yes, but I don't think that's what they meant. The universe is far from thermal equilibrium :) If you push a stone up a hill, then some of the calories you burned went into the gravitational potential energy of the stone, and some up it was lost as heat. If you compute the SHA hash of some string, then some of of the energy from the power supply went into switching the voltages in transistors, and some of it was lost as heat.
  • zamfi 2y ago
    Hmm, these aren't quite the same though, are they? I was under the impression that ultimately none of that voltage change ends up as anything other than heat. (Despite voltage being "electric potential", that's only really meaningful in e.g., capacitors and batteries, not in circuits that keep switching.)
    • MathMonkeyMan 2y ago
      They differ in the sense that it's easy to imagine how you can reclaim the energy in the stone -- let it roll back down the hill. It's harder to imagine how you can reclaim the energy of the computation. Overwriting a bit requires a little energy even in principle, and then you can't get it back. Maybe this is what the commenter I was replying to meant by "all energy generated ends up as heat." Even still, I'm tempted to make the distinction between the energy that is needed to perform the computation and the energy that is lost e.g. to Joule heating.
  • HPsquared 2y ago
    And life itself is never at equilibrium. It's all about gradients, kinetics and transfer processes.
• ainoobler 2y ago
  Fundamentally, yes. All motion does end up adding entropy to the environment. This is especially egregious for fossil fuels which are literally combusted/oxidized to move chunks of metal on wheels carrying different kinds of cargo. Electric vehicles change the dynamics somewhat but the motion of magnets still ends up contributing entropy to the environment at a somewhat reduced rate than fossil fuel vehicles.
  • tsimionescu 2y ago
    Heat and entropy are different concepts. Also, motion can reduce entropy locally, even if globally it always increases. For example, when a puddle freezes, the puddle's entropy goes way down. The entire Earth's entropy can also go down, as long as the entropy of the universe increases.
    • ainoobler 2y ago
      How are heat and entropy different?
      • tsimionescu 2y ago
        Heat is energy that causes something to raise in temperature, and is measured in Joules. Entropy is a harder to pin down concept, related to the internal state of a system, and is measured in Joules/kelvin. In certain processes, the change in entropy is equal to the change in heat divided by the temperature of the system.
        • ainoobler 2y ago
          Sounds like it's the same thing.
          • tsimionescu 2y ago
            It is not. Two bodies can have different entropy even if they are emitting the same amount of heat.
• neltnerb 2y ago
  To answer the question as literally as possible, if you reuse heat from a process in order to raise the temperature of something that needs heating, you are reducing waste heat. Here's an example, unrelated honestly to the article but just your question -- you have a pan of water on the stove, and you are continually pumping room temperature water into it. You are also continually pumping heated water out of it. This is analogous to a lot of chemical reactors but to keep it simple. If instead you run the hot water being pumped out next to the water being pumped in, the heat can be moved from the hot side to the cold side. That means less energy is needed to heat up the water coming in, because it is preheated. So, in practice, you do indeed release less heat energy because less is required to keep that kettle hot. The hot water being removed gets cooled down some too, for better and worse (often this is good, who wants hot chemicals right?). This has nothing to do with the article though, which is talking about using a neural network trained to help speed up predictions of phonon dispersion relations, which is great but maybe a little unclear. A phonon is sort of a quanta of heat if you like, so knowing how they travel in a material certainly is important and objectively cool, but the 70% thing does feel like a bit of a non-sequitur. To be honest I suspect the first sentence and second are not as related as they are implied to be, the first is simply true and the second is also true but is hardly the reason the overall industrial base of humanity is only 30% efficient. Some stuff just can't be 100% efficient, like a Carnot engine. I'm shocked it hits 30% considering thermal power stations are a major thing [1]. But I also doubt materials limits make a thermal power station less efficient by much, there's just a limit on a thermal engine. [1] To be clear, there is no citation in the press release to explain the source of this claim. Maybe it is only including after electricity generation, or maybe it only applies to industrial facilities, or maybe they're doing some weighted average of the efficiency of different electronics. I am assuming the 70% includes generation losses.
  • aYsY4dDQ2NrcNzA 2y ago
    https://en.wikipedia.org/wiki/Countercurrent_exchange https://en.wikipedia.org/wiki/Countercurrent_exchange
  • Buttons840 2y ago
    This is why I only experiment with machine learning in the winter.
• semi-extrinsic 2y ago
  No, some of our energy generated gets converted into potential energy and stays that way. For instance in cement production when limestone is calcinated to produce calcium oxide, or when iron ores are reduced to pig iron. Im not sure if all such processes amount to 30% of world energy consumption though.
  • HPsquared 2y ago
    Or aluminium production.
• inkyoto 2y ago
  No, not all of it ends up as heat. Energy conversion efficiency[0] describes how much of energy type A is converted into energy type B to perform a useful activity, with the remainder being lost as wasted heat. For instance, internal combustion engines convert chemical energy into kinetic energy with up to 50% efficiency, with the rest being dissipated and requiring a radiator in the vehicle to remove the excess [wasted] heat. Which is why your car engine becomes very hot after driving the car for a little while. The same principle applies to other systems. [0] https://en.m.wikipedia.org/wiki/Energy_conversion_efficiency https://en.m.wikipedia.org/wiki/Energy_conversion_efficiency
• adrianN 2y ago
  I guess some of the energy is turned into chemicals, eg nitrogen fertilizer.
• IncRnd 2y ago
  When you drive a car, not all of the energy from the gasoline turns into heat. Some energy ends up as kinetic energy that makes the car move.
  • MaxikCZ 2y ago
    And then the car slows down, as friction between the car and its enviroment (or inside the car itself) turns that momentum back into heat..
• icandoit 2y ago
  Imagine your computer has a knob for "release heat" and that setting it to zero on warm days did not reduce the amount of computation done. Maybe heat is desirable in some contexts, but in most it is an undesirable waste product that takes too much space to eliminate. (Heat pipes, fans, and AC are what percent of data center costs?)