Leaving computers on 24/7 - effect?

[Mise]

The initial discussion was about computers and these are usually at your desk or somewhere else where you frequently are and where you want it warm. And because of all the fans the transfer of heat out of a computer case is on a timescale of minutes, which is quite fast for temperature changes. So for the short term a computer is pretty efficient at generating heat where you want it.

Well, yeah, I mostly agree with this. I said earlier that you generally sit near a computer, and it's generally on the floor. But most people have gone further, to say that it doesn't matter if it's near you or directing heat at you, or anything like that. The mere fact that it converts electricity to heat at 100% efficiency means it's just as useful as anything else. What I've been saying is that there are other things to consider, too, other than that fact.

For example, if your computer is in your bedroom, and you're leaving it on while you're watching TV, in the belief that it will not be a net increase to your energy bills, that doesn't seem like a good idea, because by the time you get back to your bedroom, ready for bed, you might not want the heating on anyway. Conversely, if you are on your computer in the bedroom, and you go make some toast in the kitchen, the heat generated by the toaster isn't useful if you then go straight back to the bedroom. Yeah, sure, it'll eventually get to the bedroom, bathroom, living room, and everywhere else in the house. But maybe that'll only happen after 8 hours, when you're in bed and don't need the extra heat anyway. If you were to leave your toaster on (assuming it doesn't melt), it might just make the inside of the toaster hotter and hotter (and then the kitchen hotter and hotter, and then the ... until it reaches your bedroom 8 hours later), without really benefiting you at all. Alternatively, if it had a fan on it, the heat might get to the bedroom a lot sooner, and be a little more useful -- in which case the fan has done some useful work.

And in the long term it doesn't matter: If you want to keep a certain temperature at a certain point, it is thermodynamically inevitable that the whole room is heated (unless your insulation is so bad that you heat the city instead of your room). For that case it doesn't matter matter much how, where and how fast the heat is generated, what really counts are the efficiencies. Electric equipment is very efficient in converting energy to heat. It's only the generation of electricity that is so inefficent compared to other heating sources.

That's the thing, I can think of situations where it does matter in the "long term", because of bad radiator placement (it's not just bad insulation that can mean your heat goes directly to the city instead of your room), or because it takes so long to get heat from A to B that "time during which heating is needed" is actually not "long term" anymore, meaning that a lot of heat is wasted because it's being generated (or available at person-level) when (or where) no-one wants it.

Now, maybe I'm making too much of that -- as I say, I have no idea of the numbers involved, and I'm happy to accept that it might not be a huge issue. But just cos something converts electricity to heat at 100% efficiency doesn't mean that all of the heat it puts out is actually useful. Maybe the example above is irrelevant, because we're not talking about heating two different rooms, but about a single room. But then that's not a question of principle, it's a question of scale; the existence of a plastic case or walls or a corridor etc between the heating element of a toaster and the bedroom just means that it takes longer for the heat to go somewhere useful; you can achieve the same effect by just making the single room a lot bigger and/or the heating elements a lot smaller.

I'm waffling so I'll stop now.

 

[uppi]

I guess this all depends on how good your temperature control it, how good your feedback loops are and so on.

With no control at all (not even a human feedback loop that turns on the heat if he is cold and shuts it off if it's too hot), then all extra, short term heat producing appliances waste the heat, as it won't affect the main heat sources at all.

But with perfect control all produced heat (minus the loss to the outside) could be effectively used. For the example the heating system might notice, that there the toaster is running and creating heat. If it knows that this heat takes 8 hours to get to the bedroom, it could calculate that the bedroom radiator can be tuned down a bit in 7:45 hours so that the set point of 20°C can be maintained.

Of the course the first system is stupid and the second is utopian and the truth is somewhere in the middle. So the heat from electric appliances is not totally wasted, but there will be some inefficiencies.

But if your heating system is not electric or just if it's summer and you don't want to heat, the whole argument becomes pointless anyway.

 

[Tecibbar]

leaving computer on can turn into a heated discussion

 

[Mise]

That was terrible

 

[Disgustipated]

Doesn't the monitor sustain damaged from prolonged use?

monitors only last so long before they go out...

but I would hope you guys would save energy by having the monitor cut out after 5 minutes. Shame on you guys for wasting. I hate it at work they leave them on and have a screen saver cut on after 5 minutes, but they don't have the monitor power saver on. So the monitor is still on showing the screen saver. I don't like such waste.

 

[Genocidicbunny]

monitors only last so long before they go out...

but I would hope you guys would save energy by having the monitor cut out after 5 minutes. Shame on you guys for wasting. I hate it at work they leave them on and have a screen saver cut on after 5 minutes, but they don't have the monitor power saver on. So the monitor is still on showing the screen saver. I don't like such waste.

Just an fyi, standby, while using less power, still uses some. Its between 5 and 20 watts for monitors.

I have my desktop and monitors going to separate power strips. When I leave, I just shut off the power strip for the monitors (and speakers) which means no power sipping.