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Using PC waste heat to generate power? (Stirling engine project)

wisex

Hello everyone, 

As energy prices have started soaring here in Florida, we've been trying to find ways to reduce our power usage. Right now the gaming PC I have really just achieves in warming up whatever room I'm in when I'm putting heavy loads on it, be it gaming or video editing... What if it was possible to harvest some of that heat to turn it into kinetic energy that can be harvested to make electricity? The Stirling engine is an old tech that uses the temperature differential between (usually) two plates to push a piston that rotates a fly wheel, the rotation of that fly wheel can be connected to a small generator that can probably be used to charge something like portable batteries and such? For the best efficiency the case would have to be entirely sealed and heat generating components would probably need passive style coolers on it so that any air current inside the case doesn't affect the operation of the stirling engine... I don't mind my PC running hot but would the power dissipation from the stirling engines be enough to have any noticeable power offset (perhaps with reduced AC useage as well)? Would it just be like having a PC with no case fans and passive heat sink coolers? How much power do you reckon would be possible to create with one sterling engine alone(or multiple?)? perhaps having the PC in a separate room to avoid the noise of the sterling engines would also be the best option? Ideally my plan would be to get a few of these engines to charge up a nice battery bank that I can probably charge my portable electronics with... I would share the engines that I'm looking at as a consideration but I wanna get everyones feedback and criticism of this project... also I don't know what the rules are regarding posting links for buying things?... So would this be a possibility?

 

One like this (the first video) would probably be the best one to mount on top of the case, these can be found for about $40 on amazon, but some similar models with already included generators can be found for about $20 on aliexpress...

 

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The problem with heat is that it radiates In all directions. I assume that for this to work, you would need to water cool all your components so that you capture most of the heat. The problem you'll have next is how quickly you can transfer the heat from the water to that device. Radiators are able to disipate the heat quickly since through all the fins (or however they're called ), they create a very big surface area.

 

To be honest, I think you'll be better buying some solar panels. Anyway I might be completely wrong so if you do it, please keep us posted. 

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Interesting idea but sounds wildly unrealistic for the amount of power you *might* be able to generate. 

 

Like I said - sounds neat, but for the amount of power you may be able to generate it'd be quite a lot of effort imo. 

 

That being said I'd be interested in looking at the power you *could* generate. If you listed the links for the Stirling engines you mentioned I'd definitely be down to investigate myself when I should be doing homework instead 

 

 

Someone told Luke and Linus at CES 2017 to "Unban the legend known as Jerakl" and that's about all I've got going for me. (It didn't work)

 

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Wouldn't it be easier to wire up all hot components with thermoelectric generators (TG) (in other words peltier generators) while the thermal efficiency is abysmal (3-8%) it will probably not be worse than the total system efficiency of trying to harness the waste heat from a computer with a stirling engine* and much simpler with no moving parts.

 

 

*say the stirling engine has a thermal efficiency of 20% (I'm being generous here, but for the record cited highest thermal efficiency for a stirling engine I could find is around 38%) you also need to take in to account how much of the waste heat you actually manage to get to the actual stirling engine and generation losses I would imagen that you end up at a system efficiency (compared to all available waste heat) of around a TG but with a much more complex system.  

 

 

EDIT:// BTW this is a great video suggestion @AlexTheGreatish, I remember LTT making a peltier cooled computer. Why not try and see how much power you can generate with a TG computer using waste heat. 

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Hi,

 

Great, or crazy minds think alike..... This is a project I have been wanting to do for some time, but not yet gotten round to. 

 

I was discussing with a friend about this and he think's that you wouldn't be able to generate the power needed with the engine. At the time of discussing with him I was suggesting driving a gearbox which would drive the fans, however you might be able to power a small generator with it. 

 

Considering some of these things can be powered with a tea light it might be possible. 

 

There are a lot of variables to explore, such as how do you capture the heat, what do you want the engine to do, how will you mount it, cost is a big thing too.

 

I do intend to sit down and do some of the maths one day... 

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  • 2 weeks later...
On 10/4/2022 at 2:57 AM, Jerakl said:

Interesting idea but sounds wildly unrealistic for the amount of power you *might* be able to generate. 

 

Like I said - sounds neat, but for the amount of power you may be able to generate it'd be quite a lot of effort imo. 

 

That being said I'd be interested in looking at the power you *could* generate. If you listed the links for the Stirling engines you mentioned I'd definitely be down to investigate myself when I should be doing homework instead 

 

 

Thats true, from what I've seen online a sterling engine is better for heat sources that don't variate so much, then again I would probably use this to trickle charge a battery to charge my phone with, more of a personal experiement than anything

 

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3 minutes ago, wisex said:

Thats true, from what I've seen online a sterling engine is better for heat sources that don't variate so much, then again I would probably use this to trickle charge a battery to charge my phone with, more of a personal experiement than anything

 

This is a realistic view of this. Do something useful with the waste heat, but don't expect much.

"Don't fall down the hole!" ~James, 2022

 

"If you have a monitor, look at that monitor with your eyeballs." ~ Jake, 2022

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On 10/4/2022 at 10:47 AM, Spindel said:

Wouldn't it be easier to wire up all hot components with thermoelectric generators (TG) (in other words peltier generators) while the thermal efficiency is abysmal (3-8%) it will probably not be worse than the total system efficiency of trying to harness the waste heat from a computer with a stirling engine* and much simpler with no moving parts.

 

 

*say the stirling engine has a thermal efficiency of 20% (I'm being generous here, but for the record cited highest thermal efficiency for a stirling engine I could find is around 38%) you also need to take in to account how much of the waste heat you actually manage to get to the actual stirling engine and generation losses I would imagen that you end up at a system efficiency (compared to all available waste heat) of around a TG but with a much more complex system.  

 

 

EDIT:// BTW this is a great video suggestion @AlexTheGreatish, I remember LTT making a peltier cooled computer. Why not try and see how much power you can generate with a TG computer using waste heat. 

Funny that I just see your message because I've been looking into that today. My second plan was to see if I could water cool the CPU and GPU but instead of having the blocks connected to radiators I could have a water resivoir that has a bunch of thermo electric generators with radiators sticking into the warm/hot water in an attempt to remove as much heat from the water as possible in the attempt to to create as much charge as possible while also being able to effectively cool the components. From what I've seen online one 40x40mm generator can create about 1V at abuot 300 mA when theres about a 20 degree C delta between the cool and hot ends...So assuming you keep your house at the usual 25 degrees celcius you can totally trickle charge a 6v battery that runs to a small inverter that can charge a phone and stuff, just make sure you have a bunch of them connected in series to up the voltage... and if they make a video if I could get a shoutout that would be really cool lol

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The only thing I think you should keep in mind, @wisex, is that the water in a WC loop might not get that hot, unless you were gaming or had a lot of load on various components.

"Don't fall down the hole!" ~James, 2022

 

"If you have a monitor, look at that monitor with your eyeballs." ~ Jake, 2022

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3 minutes ago, Sarra said:

The only thing I think you should keep in mind, @wisex, is that the water in a WC loop might not get that hot, unless you were gaming or had a lot of load on various components.

Yea thats a good point, apparently my PC idles around 40-50C when I'm going about my daily tasks, and according to some of the specs I'm seeing it wouldn't generate all too much really.... when I'm gaming then yes there can be a lot more generation as well... the water cooling is probaby just an alternative to the original plan which was just sealing off the PC case which would just warm up the metal case too, at least with the water loops I'd be able to concentrate the heat a lot better to have it dissipated where I want it

 

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9 minutes ago, wisex said:

Yea thats a good point, apparently my PC idles around 40-50C when I'm going about my daily tasks, and according to some of the specs I'm seeing it wouldn't generate all too much really.... when I'm gaming then yes there can be a lot more generation as well... the water cooling is probaby just an alternative to the original plan which was just sealing off the PC case which would just warm up the metal case too, at least with the water loops I'd be able to concentrate the heat a lot better to have it dissipated where I want it

 

40-50c on air cooling?

 

The coolant temp can be very different from your component temps.

"Don't fall down the hole!" ~James, 2022

 

"If you have a monitor, look at that monitor with your eyeballs." ~ Jake, 2022

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I thought Stirling engines only work because they don't make much work because they're very low resistance....it's been a while though since I had a physics class.   Work...power...etc.

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2 hours ago, Sarra said:

40-50c on air cooling?

 

The coolant temp can be very different from your component temps.

Yea on air cooling, I really just have stock materials really 😕

 

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1 hour ago, AnonymousGuy said:

I thought Stirling engines only work because they don't make much work because they're very low resistance....it's been a while though since I had a physics class.   Work...power...etc.

It doesn't take a lot of energy to get them going, but the greater the temperature delta the more torque they can usually have, they'll reach a certain speed but they can definitely power individual loads and what not I think... at least I've seen people run arduinos off one without a voltage regulator and stuff

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5 hours ago, wisex said:

Yea on air cooling, I really just have stock materials really 😕

 

Your water temp might be just a degree or two over ambient at idle. There might not be enough heat load to power even a small stirling engine.

"Don't fall down the hole!" ~James, 2022

 

"If you have a monitor, look at that monitor with your eyeballs." ~ Jake, 2022

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Look up Carnot. You will find that theoretical efficiency depends on the absolute (based on 0 Kelvin) temperatures of the hot medium, and the cold medium you reject heat to. 

 

A gas engine, coal power plant or jet engine all work with very high temperatures for that reason. 

 

You can do your own math.. but even if you ignore friction or not capturing all heat, you may have 0.1 % theoretical efficiency at PC  temps. So it likely won't move at all.

 

Also look up Perpetuum Mobile 

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To further @Sarra's point about water tempurature.  You typically find in closed loops that they start to fail at around a 60c coolant temp.

 With all the Trolls, Try Hards, Noobs and Weirdos around here you'd think i'd find SOMEWHERE to fit in!

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17 hours ago, SimplyChunk said:

To further @Sarra's point about water tempurature.  You typically find in closed loops that they start to fail at around a 60c coolant temp.

Failure of the tubing is actually something I didn't really consider... although 60C would be about a 35 degree temperature differential which would hopefully have these things running pretty well... but you're right that theres definitely more to consider

 

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17 hours ago, Lurking said:

Look up Carnot. You will find that theoretical efficiency depends on the absolute (based on 0 Kelvin) temperatures of the hot medium, and the cold medium you reject heat to. 

 

A gas engine, coal power plant or jet engine all work with very high temperatures for that reason. 

 

You can do your own math.. but even if you ignore friction or not capturing all heat, you may have 0.1 % theoretical efficiency at PC  temps. So it likely won't move at all.

 

Also look up Perpetuum Mobile 

Stirling engines tend to have a 40% efficiency in which ICE's generalls have about a 25-30% efficiency? in terms of capturing the heat and all.... in a theoritcal sense we would want to seal the PC so as to ensure that the most heat is sent thorugh the stirling engine while ignoring the heat radiating from the metal case itself

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On 10/19/2022 at 10:26 PM, wisex said:

Stirling engines tend to have a 40% efficiency in which ICE's generalls have about a 25-30% efficiency? in terms of capturing the heat and all.... in a theoritcal sense we would want to seal the PC so as to ensure that the most heat is sent thorugh the stirling engine while ignoring the heat radiating from the metal case itself

I like to see the real World Stirling engine with 40% efficiency. Especially one operating at PC temperatures.

 

You probably can make a Sterling toy run with 95C CPU temperature, but it won't provide extra work besides overcoming friction. But at case temperature that toy won't even crank over.

 

https://en.m.wikipedia.org/wiki/Stirling_engine

 

https://www.amazon.com/Thermodynamics-Sanford-Klein/dp/0521195705

 

 

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