Peltier-based water-chilling experiment

Jstic,

I hadn't thought of the power supply problem, I had always just assumed that I would need to have a separte PSU for the pelts, and it would have to be one of those fangles that they normally try to sell with them.

I have a mini one here, and I'm sure I could run two pelts and the pump off of it. The pump I plan on buying only uses 22W & 155V.

Nope, just measured it. I'll have to buy one of those little mini-ATX PSU's.

Yeah, the PSU is one of the biggest issues with pelts. I got lucky and bought an Antec 510D PSU refurbished from Newegg. For $49 I have 40 amps on the 5V rail and 30 amps on 12V. I run 4 pelts off of it and it has been going strong for 7 months.

Sounds like your pump is a regular 110V type that will plug into the wall.

The main thing with the PSU is to check the amperage rating before you buy it. Rule of electricity: don't exceed 80% of your PSU's rated amperage.

The thing with peltiers is that they consume vastly lower amounts of power at lower voltages, and indeed it is far more efficient (apart from buying them) to hook up multiple peltiers in parallel at lower voltages, than to run a single peltier at full voltage.

For example, take the Drift-0.8 peltier from Kryotherm, which is a 172W peltier that draws 11.3A at 24.6V at maximum.

Cooling it with a decent water-cooling setup gives the following results:

12.0V/6.1A => 81W Cooling power, 73W power draw, 154W heat emitted

15.0V/7.6A => 90W Cooling power, 114W power draw, 204W heat emitted

18.0V/9.1A => 95W Cooling power, 164W power draw, 260W heat emitted

21.0V/10.6A => 97W Cooling power, 222W power draw, 320W heat emitted

24.0V/12.11A => 95W Cooling power, 290W power draw, 384W heat emitted

Now at 12V we've still got about 80% of the cooling power of the TEC running at optimal voltage (21V), but are only sucking down 30% of the power to do it.

We can run 3 peltier at 12V and still be drawing down less power than a single peltier at 21V.

The same 3-peltier setup will provide 242W of cooling power, while only sucking down 220W (about the same level of power as the single peltier at "optimal" 21V), and only emit 461W of heat.

Running multiple high-power peltiers at about half voltage is a substantially more efficient way to use peltiers to their best potential.

Does anyone know of a website that has a good selection of peltiers (size/watts/price) that won't completely drain my wallet? Instead of running two square pelts, I might try to run 3 rectangular pelts.... The configuration is limited somewhat by my space, but I might be able to make something work if I didn't have to choose from 50mmx50mm squares.

Go here. Pricing and selection are the best I have seen. They have just about every size and type pelt you could want.

Only drawback is $100 minimum . I've dealt with them many times and have always gotten excellent service.

Cathar makes some excellent points in his post above. Very worthwhile reading. More is not always better.

Ordering $100 worth of pelts won't be too much of an issue, because I had originally planned running two small rads, and they totaled over $100. It makes sense to max out $100 on a pelt budget, to me at least.

Okay, but here's the question. I'm looking at all of these pelts and am unsure which one would work best? Would a lower watt pelt running at higher voltages work better than a high watt pelt running at lower voltages for an air-cooled setup? I am looking for a 30x30mm, and it's looking like I'll run 6 pelts all together.

I'd like to run something flexible enough that I can get the water a few degrees below ambient, but also have the flexibility to run the pelts higher and get the water even cooler. Some day I might get crazy and insulate everything.

Just to help me fish, where would I go to find out this information so I could do voltage-> cold side/hot side temps conversions myself?

Thanks for all the great help and suggestions, this is really starting to come together now.

OMG!!!!!!
/me looks for his snuff can.....