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Comment by glogla | Hacker News Reader

That's pretty solid space heater.

Does all the energy get converted to heat? What about “useful work”?

The law of Conservation of Energy says all that input electrical energy going into the system has to be accounted for in the form of some other energy.

Now the only thing moving will be the fans and the hard disks, which means only a very little of that input energy will be converted to kinetic energy.

The system will not be storing energy, meaning none of the input energy is being converted to potential energy.

Now some energy will be lost in the form of noise and light emitted from the leds and monitors etc.

So that only leaves the radiated energy (i.e. the heat) produced by the system.

I would think that heat component would make up the largest portion of that energy pie.

Even the kinetic energy (fan motors, HDD motors) eventually becomes heat. E.g., the moving air from fans dissipates its energy in turbulence in the room's air, and in a closed system (airtight room), the resistance to airflow (resulting in heat) must equal the pressure differential created by the fans, unless the air builds up unbounded speed. Likewise, torque to keep the HDD platters spinning will be exactly equal to frictional losses once the disks are spun up, so all power into the spindle motors becomes heat.

Even noise that leaves the system either becomes heat as the pressure waves dissipate through the atmosphere, or else do work on eardrums (mechanical energy) which eventually becomes heat as the inner ear resists the motion of the ear bones :-)

Very inefficient though. But solid!

Is it inefficient? Some of the energy will be converted to light, but all the rest should be converted to heat? If you need constant heating and use electricity for heating, wouldn't a mainframe be as efficient as any other heating?

It would. Unless you could replace the electric heating with a heatpump though - then you would get more heat out of each kW you put in. But replacing an old-fashioned electric wall heater with a 1700 W mainframe would be totally equivalent. So no, a 1700 W computer isn't more 'inefficient' than a wall heater of the same wattage. The light is neglible and it too ends up as heat anyway.

Heh, exactly. Even the light will quickly be turned into heat once it hits something. Sure some might escape through a window, but that's going to be vanishingly small amount of the total energy.

Actually it's 100% efficient in terms of converting electricity into heat. Anything that consumes electricity is near 100% efficient at generating heat. If you tried really hard you could build a very efficient laser and send heat outside the room, so not 100% would end up in the room. Even then the majority of heat will be dissipated in the room.

It’s 100% efficient, but you can do better than the 100% without breaking thermodynamic Laws with a heat pump.

Right, but it was being compared to a space heater, not a heat pump.

Not to mention heat pumps require somewhere to pump to/from, you can't just put one in your basement, plug it into the wall, and heat up the basement. Also heat pumps work best with mild differences, like say 40F inside and 60F inside if you want to heat.

Heat pumps reduce to space heater efficiency if it's sub-zero Fahrenheit outside I believe.

Sub Zero F is seriously cold! But for most climates there is some advantage. 40F is pretty cold. Take somewhere not particularly hot like London - most of the year it will be warmer than that.

Although in the UK most people use gas to heat their homes, because its cheaper. I worked out once that gas and heat pumps cost the same in the end for the amount of energy. Although what I love about heat pumps is how quick they get a place warm compared to radiators.

Granted heat pumps need installation, or you can probably run a tube out the window with one of those adapters.

It's a silly hypothetical discussion, because for the price of this mainframe you could get a heat pump and a set of solar panels and a battery storage, and have some money left over for some Hawaiian shirts to wear once you've heated the place up.

For financial efficiency (environment be damned) a set of crypto miners would be better than either the mainframe or the heat pump.

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