For more pictures of this project you can visit my galleries.
Several years ago, I was fascinated with peltier elements. I won’t bore you with an encyclopedic definition but in general terms they’re basically little heat pumps. You plug them in and one side gets super cold while the other gets super hot. If you reverse the voltage, you change which side gets cold. They can be as small as a fingernail or as large as well… only the government researchers know that really. The bottom line is that you have the power of a fridge in a very small package and with no moving parts.
Computer overclockers have found these very useful in making their PCs run faster. For me it started with buying one 156w unit, than a 172w, than a 226w, than two of those, and so on and so forth. I kept increasing my cooling capacity and in turn my computer went fast and faster. But it was never enough.
And more is better right?
In 2003 I reached the final iteration of my peltier cooling monstrousity. An 1100w dual water loop cooled behemoth I called “The Cube”. It consisted of a 226w peltier cooling the CPU directly, a 172w peltier cooling the GPU, and four 172w peltiers chilling the water. It was big, loud, and required a 20amp 110v circuit to run.
The heat output of this computers CPU and GPU was about 170 watts when overclocked. More than enough to make the inside of any case in to an Easy Bake oven. With decent air cooling the CPU may have been stable at around 60c degrees. With typical water cooling about 45c degrees. When using a big 226w peltier directly mounted you could expect 30c degrees. If you want to chill a CPU down below 0 celcius you need The Cube.
I don’t actually know what the final cooling power of this project was but according to the CPUs onboard diodes it was well below 0. Unfortunately that prevented me from knowing the true temperature. Also the thermal diode on a CPU may very well be highly inaccurate in that temperature range.
As I mentioned, this system had a 226w peltier mounted on the CPU. The CPU was operating at about 110w overclocked. The 226w peltier actually required 300w of power to run. This also meant that the hot side of the peltier was operating at with over 400w of heat energy. You can cool the hot side of the peltier with water cooling just like how a car’s engine works. The coolest you can hope water to be without major evaporation is room temperature. This is a downside to peltier cooling since how cold the cold side gets is directly proportionaly to how hot the hotside gets. These peltiers when dealing with CPUs are only reasonably capable of cooling the cold side about 20c colder than the hotside. If your water temperature is 40c, your peltier hotside is about 50c, and your CPU is going to be about 30c.
The bottom line here is that you want to make your water cold too. I had to build a water chiller capable of bringing the water temperatures down to under 10 degrees celsius. After actually doing some thermodynamic math with my target temperatures I discovered that I would need A LOT of power to do this. Four 172v peltiers later and the chiller was reborn.
And it worked. The water was able to stay under 10c degrees while extracting the heat from my CPU, GPU, and their respective direct mount peltier units. Something has to cool the chiller itself which alone generated 1,060 watts of heat energy. That’s a decent microwave oven worth. This is where the dual-loop comes in: a completely separate water cooling system designed to only cool the chiller. This would be known as the ‘hot’ loop where radiators were used to distribute the massive heat load to the air. The ‘cold’ loop used the chilled water to cool the direct mount peltiers.
Unfortunately this system proved to be highly inefficient. The amount of heat that was dumped in to the hot loop from the CPU, GPU, and six peltier elements was a stagering 1800 watts. The entire system itself plus computer parts drew over 2200 watts from the wall sockets once you factor in power supply inefficiency. That’s the upper limit of a US 20amp breaker. Forget the expense of electricity, that’s pretty much a guaranteed fire hazard!
I suppose that all of that 2200w ended up as heat energy in my 12×10 bedroom. I needed to run my 900 BTU air conditioner just to stand being in the same room in the thing and I left my windows open in winter just to keep myself cool.
The overclocking difference that you get at -10c degrees isn’t much greater than what you get at 30c degrees. The extreme expense of a project like this doesn’t justify the performance gains especially with Moore’s law making all of our gear obsolete in months anyway. Phase change cooling is more powerful than peltier cooling, produces less heat, and is much less expensive to run. Even it’s benefits to real world PC performance are really hard to measure. And it has been with this philosophy that I have proceeded for the 5 years since this project. I now build quiet and basic water cooling systems that maximize performance at the minimum of cost. If you’re going to bother for the most performance possible just dunk your CPU in liquid nitrogen. Why half-ass it with anything else?