Computers for heat

Hello smart forum users who are good at pointing out flaws in my hairbrained ideas.

This sure seems like low hanging fruit, now that its cold again the electric furnace is cycling on and off at 11kw of just pure sacrifice to the gods of entropy, precious electricity to low grade heat. I don’t think I can tell if heat comes from ceramic or silicon. You see where this is going?

compared to heating element, even the oldest computer wins in computations/watt. finally a use for the closet of otherwise garbage bound computers
with the right application, you may even be able to earn money*

Looks ugly
Built in cooling system loud and not designed for heat radiation for human comfort. But maybe putting radiant fins or a fancy water circulating system could help here.

*it sucks that cryptocurrency is the most plug and play example for this, but really I think anything else would be cooler, especially something like an emergent market for micro scale distributed data centers.

Is it you want general home heating? Or heat generation in specific spots?

I certainly could be wrong, but there’s probably nothing more efficient than directly turning electricity into heat, is there? At least when it comes to electric furnace VS computers. Or are you just wanting a general amount of heat being generated constantly, and then supplement as needed by the electric furnace?

Quite. I do it for my office, and to a lesser extent the house. I’ve been “heating on BOINC” for about 5 years now in the winter, though I’ll bring an actual electric heater online (or propane heater… whatever) in the cold if it’s particularly sunny out.

1kW in = 1kW thermal out, and, yes, you may as well do something useful with the power. I have a heat pump and backup coils, and do my best to keep the coils off.

Correct, though eventually you fall off the back of the “gets work done in the required timeframe” window. And/or lack hardware support for instruction sets required (go old enough, many compute projects won’t run due to a lack of the required SSE/etc).

Also, noise. A lot of them tend rather loud.

Don’t waste the money on water cooling ancient hardware. Just get a modern fan and heatsink combo if you need, and let them run. You can also pair multiple systems on a single PSU, though sleep/wake can get weird in that situation.

Crypto mining certainly is an easy way to make your heating “pay for itself.” If the waste heat is a bonus, and you’d be running the energy through a resistor instead, even older, less efficient miners are still worth running. If you can score some AntMiner S9s or so, you can pull the power back on them and run them fairly efficiently, on top of the heat generated. They’re just loud at full tilt.

If the metric being used for efficiency is “heat put into an interior space per unit electrical energy,” heat pumps are quite a bit more efficient than computers/resistors, as they’re moving heat - they’ll be 200-500% efficient by that metric.

The right answer here is to put a mini split in, and heat that way, but if you’re stuck with an electric furnace, yes, do something useful with the power on the way to heat.

Right, but I was comparing electric furnace vs computer heating. Excluding heat losses from the duct work/etc of course.

Good point, Although the cost of that is anywhere from ~$2000 if i were a DIY god and decent deal hunter, to like $20k installed and warrantied by a company. Compared to $0 for the few Core 2 Duo and Pentium 4 old desktops that are here.
There seems to be more warmth per watt if you’re closer to the heat source. PC as an under desk foot warmer?

In that case, yes, I’d treat them as equal.

The DIY kits lately tend to have sealed lines, such that you can hook stuff up and they’re self purging - you don’t need the vacuum pumps you used to need. They’re apparently pretty nice.

The problem is that things like Core 2 Duos and Pentium 4s are too old to really do much useful work. I don’t think most modern BOINC stuff will run on them, so… what are you going to be actually doing with them? On the other hand, if you want a 350W Xeon, I’ve got one laying around. Find a PSU for it (needs a dual 8 pin CPU connector PSU), and it’s yours if you want! :slight_smile: I’ve not been running it in my office because it’s a lot more power hungry than the other stuff I’ve got, quite a bit slower, and doesn’t sleep worth a damn.

Certainly! Duct your desk with some curtains too, and you can get it nice and warm under there - just don’t let it heat up too much or you’ll cook the computer-heater. But I definitely had hot air under my desk from a computer for a while, and it was nice.

Or just get some 3090s and mine… whatever it is GPUs mine these days.

If you’re interested in energy conservation, look at the Rheem heat pump hot water heaters. They are designed to be hooked up to ducts (though meant to lead to the outdoors) but if you live in a warm climate, you could certainly plumb that cold air into the house.

If you had servers, you could also couple them with the water heater, but I’m honestly not sure how much the temperature cycling will affect the hardware lifespan, since it’ll very intermittent.

I’ve also seen “heat reclamation” units that get plumbed inline with heat pumps so you can extract the heat being rejected to the outdoors (assumes you’re using them in cooling mode).

The real problem is that space heating is horrifically expensive energy wise. I have a 1950’s era house in the south bay area (silicon valley, CA) with added attic insulation (deep enough to cover the rafters) and double pane windows everywhere. I estimate we use about 170-200 therms a year (burned through our original 1950’s furnace!) to warm the house, and I usually keep things quite cool (and put on thermals and a sweater instead), so it’s not like I’m setting the thermostat to 80F. Gas rates over the last year have been $1.38 (summer) - $2.42 (January) per therm. If we used the exact same BTUs * efficiency boost of a heat pump, but paid our (city utility) rates of $0.11-0.12/kwh, we’d still end up spending more dollars per year.

In winter we use about 4x more fuel (water heater, furnace, stove top), than electricity if you convert therms to kwh (100% eff). Summer (i.e. no furnace) is still 2x natural gas therms vs electric kwh. Note also that our electricity use is roughly double what houses in our area use, due to the server+networks (roughly 150W continuous), (electric 24/7) hottub, and fish pond (pump).

So as a practical matter, focus on your heating efficiency if you want to save $.

I’m planning to get one of those installed… at some point. But we’re still heating degree day dominated, so venting it to the house (which is what I’d be doing) may or may not be as much of a win as I hope. Especially if I’m heating with compute, I’d put a kWh thermal into the house, which would… then get sucked over into the water tank. Vs just putting a kWh thermal directly into the tank. I suppose in this situation, I’ve at least had a chance to do something useful with that kWh first.

If I heat more with the heat pump, it’s probably better, but… I’ll see.

The real value of it would be lowering peak power draw, and being able to schedule it to run more during the middle of the day when we’ve got solar online and potentially a warmer house. The water heater, in the winter, tends to run early in the morning when I take a shower, and it’s coldest outside. Letting it just stay a bit cooler until the sun comes up would help some… I think. I don’t have a good enough energy flow model of the house (mentally or computationally) to really reason through all of it, but it should save at least some energy compared to a resistive type heater, which is what I have now.

Without a good place to store an awful lot of heat to be reclaimed by the water heater, I’m not sure how that would work. You’d need some sort of dense heat storage mesh or something - vent the servers through it to collect heat, then let the water heater intake pull from it. It sounds like the sort of thing that would be “Spend hundreds to save tens,” at best.

The combined units are definitely a win, but they’re quite expensive, and quite complex - and if something fails, you lose both hot water and HVAC.

As far as house heating goes, though, some of the air source thermal collectors look pretty promising. If it’s sunny, they should put out more than enough heat to keep a house warm, they just have the problem of being rather ugly. I’ve also thought about a solar thermal collector for water and then a hot water loop into the heating system (stick a radiator on top, effectively), but this crosses into an awful lot of “I ought to pull permits for this type of work” and “… that’s weird, who said you could do that?” potential problems. I’m really not sure it’s worth the hassle.

Now, for heating the hot tub I want eventually - yeah, I’ll do some thermal collectors for that! Just need a place they’re not exceedingly ugly or likely to get broken.