> 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 if someone has more insight. Doesn’t all energy generated end up as heat somewhere? Like every watt going into a bitcoin mining rig gets released as heat. I’m unsure how you’d determine what percentage of that is 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.
Im not sure if all such processes amount to 30% of world energy consumption though.
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.
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.)
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.
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
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
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.
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.
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.
They are damn impressive, but not "forever".
One small exception may be microntollers that use PWM to emit a signal through an antenna, or to drive a motor. I think in that case some of the energy becomes radio waves (which may never be absorbed entirely so they may not become heat) or motion in the motor.
A lot of it comes down to whether a process is reversible or not. I've taken multiple courses on thermodynamics and still only understand it a little.
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?)