Using peltiers to cool coolant to generate electricity?

nuhash · 9 Jan 2012 at 21:28

I was looking into peltiers and read that they could be used as generators and I was thinking if used a cpu waterblock, a peltier and then some kind of cpu air cooler and sandwiched together:
waterblock
-----------
peltier
-----------
air cooler

would it not be possible to generate a current from the heated water and then power a fan which cools the air cooler and so keeps the temperature gradient high enough?

the only problem i can see is that the water may not be hot enough and the heatsink on the opposite side may not be cold enough so only a small current will be generated

panyan · 9 Jan 2012 at 21:38

its nice to talk theoretical, but i think the practical limitations is what will hold this back

nuhash · 9 Jan 2012 at 21:45

yeah, it seem most peltiers will only transfer about 5% of heat into electricity

Cleeecooo · 9 Jan 2012 at 22:16

panyan said:
its nice to talk theoretical, but i think the practical limitations is what will hold this back

samcat · 10 Jan 2012 at 09:34

http://www.fluesystems.com/shop/Ecofan.html?gclid=CL-Gr7eTxa0CFQUOfAodHyAl_w

We use one of thse on the log burner, the big difference in temperature provides enough power to spin the fan which in turn pushes the heat around the room better.

Bubo · 10 Jan 2012 at 10:41

If Brian Cox were around I'm sure he say something about entropy or second law a thermodynamics or something along those lines

At this time of year you're better off just letting the waste heat warm your room up.

Roverno · 10 Jan 2012 at 11:44

Warming up the room is definitely a more effective use of the 'waste' energy

panyan · 10 Jan 2012 at 12:33

just for your interest:

i dont actually think that you would need to power a fan to cool the heatsink,

the peltier will absort a lot of that heat, thus cooling the cpu rather effectively, it will then convert that energy into ~5% electricity so it MAY be possible to get away with a much quieter system - think of it almost like watercooling but the heat is used to generate a little electricity

im thinking of the next generation of PSU's that has a little plate on the end of a wire that gets sandwiched between the cpu and the heatsink and it reduces your electricity bill by taking the heat from your CPU

i GUESS that the more heat the CPU is putting out, the more electricity is generated so we could have super massive overclocks and save a lot on the electricity bill

its nice to think out of the box sometimes

nuhash · 11 Jan 2012 at 21:40

panyan said:
i GUESS that the more heat the CPU is putting out, the more electricity is generated so we could have super massive overclocks and save a lot on the electricity bill

well a 600w PSU will only use about 6p every 2 hours (depends on tariffs etc.), the wattage on a cpu is about 120W (correct if i am wrong), if 5% is reused to power then 20W is recovered per hour which is like 0.12p so the savings wont even be noticed unless you run your pc 24/7

to save 1kw per hour (1unit of electricity) you would either need to move 20kW of heat through the peltier (not possible unless you have quad crossfire and a motherboard two 8 core cpus which are oced, at this stage if you cant afford the electricity then this is maybe a bit stupid) or you could develop a 100% efficient peltier and all would be great!

Also, this is in favour of entropy as by transferring the heat through the peltier energy is spread across more particles so there are more ways of rearranging the quanta of energy, and while i am on this, the second law of thermodynamics dictates that energy cannot be made or destroyed but transferred or transformed, which this obeys