hks85

First off, i know the question is vague, but please do your best.

inefficiency = heat right?

so if i had a computer (aside from any light via a monitor or and fans moving air) then how would the energy being used translate to heat? if my computer uses 100watts, how can we relate that to heat? how would the efficiency change that thermal output if at all?

IE:

computer 1 = 50% efficiency with the total power draw of 100w

computer 2 = 100% efficiency with the total power draw of 100w

would they each dump the same amount of heat?

u238

The only computer component you give efficiency ratings are power supplies. They are rated for efficiency based on how much of the power they consume becomes heat (the rest becomes available for use). For the rest of your computer, all of the electrical energy becomes heat. A computer does no work, therefore all electrical energy consumed must become heat. A computer is 0% efficient.

Edit: you are correct when you say "aside from fans moving air" as fans do mechanical work on air, so only a portion of the energy they consume becomes heat. I would still consider a computer 0% efficient as work done on air by fans is negligible compared to total power draw.

0rion

if a computer were 100% efficient, then NO heat would be lost at all. No heat would be generated. All the electrical current it received would be used to make the computer function. As we know, Electrical current creates heat, and as you say, inefficiencies in design and whatnot generate heat.

Im no expert, but a computer chip uses a lot of energy, and is nowhere near 100% efficient, therefor throws off quite a bit of heat, which is why we have massive heatsinks, watercooling, etc to remove that heat before it builds up and damages components.

When saying a computer uses X watts, remember that watts = volts * amps. Your computer is converting alternating current (AC) to DC voltage which is only 85-90% efficient at the best of times (PSU creates heat out of the rest of it) and then components use some voltage at a certain amperage, and the rest gets turned to heat.

Your example was a bit off though... if it were a computer system say at 2.4ghz, a 100% efficient computer might use say 200 watts. If it were only 50% efficient it would need 400 watts to keep stable the same computer at 2.4ghz, but it would convert that extra 200 watts to heat due to its inefficiencies.

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hks85

exactly what i was thinking.... so, during the winter months, the most productive way to heat your house would be with computers right?

bomfunk

Well of course they wouldn't... at the supposed 100% efficiency the computer wouldn't be producing any heat at all. At 50%, roughly half of the electricity will be converted to thermal energy.

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u238

That would depend on energy prices. Resistive heating, which is what your computer is accomplishing, is generally the most expensive way to heat homes. Oil, gas, coal and wood are usually more economical.

grishkathefool

well, and some light too...

here is a post that has some bearing on your question.

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