Are all electronical devices equally efficient at heat production?

[Jeff7]

Actually this reminds me, I read somewhere that electricity is one of the most efficient ways of producing heat. The reason why in reality it's not (compared to gas) is that said heat also gets generated along the electricity's travel path. Ex: each time it hits a step up or step down transformer, the wiring itself, etc. So guess it does make sense that all used power is turned into equivalent wattage of heat, just that this heat is not at the appliance itself but spread from the power plant to the appliance.

And there are efficiency losses elsewhere.

Electric heat:
1) Burn fuel.
2) Heat water to boiling.
3) Moving steam turns a turbine.
4) Turbine turns a generator.
5) Electricity is transmitted to you.
6) Electricity heats your room.

vs

Combustive heat:
1) Burn fuel.
2) Heat air in a furnace.
3) Blow heated air into your room.


If you burn the fuel in your house, you pretty much produce the heat right where you want it.

 

[Rubycon]

And there are efficiency losses elsewhere.




If you burn the fuel in your house, you pretty much produce the heat right where you want it.

You can burn a couch and will put out about a million watts!

 

[Eli]

Electrical resistance heaters are 100% efficient. Every watt that goes through them turns into heat. Even the losses on parts of the heater that aren't the heating element (resistance in the wires, etc) is turned into heat.

If said electric heater has a fan, some of the energy goes to moving the air. 😉 But yes, for all intents and purposes electric (resistance) heaters are 100% efficient.

Basically, if there is work other than producing heat being done, then there will be a difference.

Example: A 100W light bulb doesn't give off exactly 100W of heat, because some of the energy is turned to photons. According to Wiki, a 100W bulb has a luminous efficiency of 2.6%. So that means "only" 97.4% is converted into heat.

 

[PieIsAwesome]

Um, wrong. The actual processing parts of the computer basically solve logic. It just routes a signal through different gates, no real work is done like you're describing. The only output current or lack of current (basically 1s and 0s). There's no magical work going on. The actual power consumption is from the resistance to the flow of the electricity as it's routed through the different gates. All the power consumption from resistance to the flow of electricity is converted directly into heat.

Well, I guess I don't know how a computer works then. I was going by the analogy of an engine receiving heat Q_in and outputting heat Q_out + Work, which of course means that Q_out < Q_in, versus a heater where no work is done so Q_in = Q_out.

But I guess even work done would eventually be converted to heat and will raise the temperature of the room if all the conversion to heat occurs in the room.

 

[TecHNooB]

There's always work being done. Electrons are our slaves. They be working you know!

 

[dighn]

You can burn a couch and will put out about a million watts!

time to stock up on couches :awe:

 

[Colt45]

Example: A 100W light bulb doesn't give off exactly 100W of heat, because some of the energy is turned to photons. According to Wiki, a 100W bulb has a luminous efficiency of 2.6%. So that means "only" 97.4% is converted into heat.

And when the photons get absorbed by the walls in the room, they turn to heat. So it does put out 100W of heat, but only 98W of it directly... right?

 

[Hacp]

And when the photons get absorbed by the walls in the room, they turn to heat. So it does put out 100W of heat, but only 98W of it directly... right?

What makes you think that? The energy might be used in reactions to change the chemistry of the paint on the walls for example.

Edit: Also, if a 100W lightbult produced 98W of heat directly, it would be a very inefficient lightbulb.

 

[Colt45]

incandescents are ridiculously inefficient.

 

[OverVolt]

The fan gives off some energy in the form of sound. Not so tough now eh Mr. 100% is converted to heat.

 

[Leros]

The fan gives off some energy in the form of sound. Not so tough now eh Mr. 100% is converted to heat.

And sound is just vibrations in the air which turn into heat. All energy eventually becomes heat.

 

[zeruty]

And there are efficiency losses elsewhere.

Electric heat:
1) Burn fuel.
2) Heat water to boiling.
3) Moving steam turns a turbine.
4) Turbine turns a generator.
5) Electricity is transmitted to you.
6) Electricity heats your room.

vs

Combustive heat:
1) Burn fuel.
2) Heat air in a furnace.
3) Blow heated air into your room.


If you burn the fuel in your house, you pretty much produce the heat right where you want it.

Oil heat, wood heat, or propane heat requires the fuel to be transported to the site. This causes inefficiency in the form of added cost due to the transportation.

Natural gas seems like it would be the most efficient method. I don't know how the gas is propelled through the pipes though. Electric pump?? Natural pressure?

 

[zeruty]

And sound is just vibrations in the air which turn into heat. All energy eventually becomes heat.

What about radiation emitted from the computer? I don't mean radioactive-mutate your future children radiation, but RF interference, etc. I imagine some of this will travel straight through your walls and escape outdoors?

 

[Leros]

What about radiation emitted from the computer? I don't mean radioactive-mutate your future children radiation, but RF interference, etc. I imagine some of this will travel straight through your walls and escape outdoors?

RF is just a wave, the kind of wave as sound but at a higher frequency. Some will be absorbed by your walls and heat them up.

 

[zeruty]

RF is just a wave, the kind of wave as sound but at a higher frequency. Some will be absorbed by your walls and heat them up.

Well, as radios work indoors better than sound travels through walls, I assume some of the RF makes it through the walls. Thus making a computer less than 100% efficient at creating heat.

Even 99.999% is less than 100% 😛
(i dont mean 99.999... repeating, you mathematical heathens ^_^)

 

[Hacp]

RF is just a wave, the kind of wave as sound but at a higher frequency. Some will be absorbed by your walls and heat them up.

You're an idiot.

 

[alphatarget1]

I would think a PC with a 300W PSU wouldn't be producing 300W at all times, unless you're running a lot of computations. Same thing when the CPU gets hotter when you make it do more work, like Prime95.

 

[Howard]

You're an idiot.

So he's wrong on the former, right on the latter. So?

 

[Hacp]

So he's wrong on the former, right on the latter. So?

No, I just like calling random people idiots lol.

 

[silverpig]

If said electric heater has a fan, some of the energy goes to moving the air. 😉 But yes, for all intents and purposes electric (resistance) heaters are 100% efficient.

Basically, if there is work other than producing heat being done, then there will be a difference.

Example: A 100W light bulb doesn't give off exactly 100W of heat, because some of the energy is turned to photons. According to Wiki, a 100W bulb has a luminous efficiency of 2.6%. So that means "only" 97.4% is converted into heat.

Actually that's not quite right. A 100W light bulb converts 100% of its energy into heat. 2.6% of this heat is radiated away as visible light. An incandescent light works by heating something up until it glows. Heat is the first product, light is the second.