Fruity ideas for the summer: Tent A/C.

If you're having to pay for a studio, an RV to go to festivals generally won't be on the ledger, and there's that godawful time between like 9 and 11 AM where you would LIKE to be sleeping, but the polyester has teamed up with the sun in an unholy alliance to torture you for whatever colorful excursions you had the night before.

Enter the tent A/C. What was going to be a microprocessor-controlled cooling unit turned out becoming an analog PWM driven dual fan peltier and CPU radiator with probably the lowest thermal transmission coefficient in the industry, along with thermal migration going straight through the peltier element. So in came water cooling CPU heatsink blocks and high-performance peltier elements from the German company Peltron.

The big issue with peltier cooling is how to dissipate the heat on the other side, as the cooling efficiency is a direct result of the element's absolute temperature, and the better you can cool the hot side, the colder the cool one gets.

All of this is then supposed to be solar powered, right?

2 elements of 25Wp each delivered around 1.25A continuous in actual practice, vs. the 3.3A or so peak load current, so it's gonna have to be around 100Wp total on your solar array in full sun for this to actually fly. Now we have 3 sets of 2x 25Wp offering a theoretical continuous of 3.75A in regular light and up to 9A or so in full sunlight.

In most general applications you'll be more prone to make 2 water tanks, one warm and one cold, for the shower and cooling drinks and just spend les heures du matin hanging halfway extended out of your tent with a hopefully dark enough sleeping bag over your head, and a light-proof opening provided for the air intake of les misérables. Don't worry, it WILL be 2PM, and the others will have discovered some kind of wrap and cocktail down there to wake you up with.

In either case, a good buffer battery is a good idea, probably a pretty essential one, as you'll be drawing >5A continuous on full blast.

The PWM does the fans and pumps, and the DC-DC converter sets the voltage point and current limit for the Peltier. An additional µC with digital readout measures core temperatures, voltage and current while two 140mm Mag-Lev fans keep the air flowing.

Another cool thing would be a 2-way valve for the hot water containment, so that heated water could be pumped straight into the shower tower utilizing an external line.

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