The goals for this project were for the device to be compact, achieve cooling without relying on any external cooling medium (no cold water or ice cubes), and operate from a power bank (3A current limit) or other portable power source.

To achieve these goals I used a low power TEC1-12704 module and a 60mm fan that I power using a USB-PD trigger board to request 12V 3A from my power bank. I used a "San Ace 60" model fan but it ended up being overkill for this Peltier module so a more powerful one can be used instead. I cannot use a more powerful one because that would put me over the 3A limit of the power bank. In fact, this setup briefly draws around 3.2A - 3.5A at startup but it does not trigger the power bank's OCP.

The device does not have any electronics to control it so it works at 100% power all the time. Ideally it would at least have a way to control the Peltier module's duty cycle and a hot side temperature measurement to prevent the Peltier module from burning itself in case of a fan failure.

The portable AC uses a Peltier module (or thermoelectric heat pump or TEC) which is a solid state semiconductor based device that can achieve sub-ambient temperatures. It works by using electrical energy to move heat from one side of the plate to the other. As a result, one side of the device heats up while the other one cools down. As a bonus, the hot side achieves an efficiency of higher than 100% (if we take as input power the electricity supplied and as output only the heat energy of the hot side).

To keep the Peltier module from burning itself, and to utilize the heating and cooling produced from it, there are two 40mm heatsinks attached to wither side of the module. The fan draws in air and the housing splits it among the 2 heatsinks. After going through the heatsinks, the heated/cooled air reaches the separator that redirects the 2 air streams into opposing directions so you can choose which to use and which to discard.

The main (front) part of the housing has a cutout on top for the fan connector to pass through. Because I scaled up my front and back models by 2% and 2.5% respectively, The threaded inserts for the fan screws ended up misaligned so I was only able to screw in one of them. I downloaded and modified this fan cover from Thomas Weber. The holes at each side of the separator can perfectly fit a 40mm diameter vacuum cleaner hose to either redirect the useful air into the area you want to heat/cool or to expel the useless air to the atmosphere.

The separator contains a slot to route the Peltier module's to the top (or bottom) of the device.

All parts have been 3D printed with Prusament PC Blend to ensure reliable operation even at high temperatures.

I ran a test where I let the device run for 15 minutes and then measured the hot, cold, and input temperatures along with the case temperatures next to the heatsinks. While operating, the device drew roughly 2.7A at 12V (32.4W). During operation the fan produces 83dB of noise (measured at 10cm away).

Results:

• Input temperature: 20.2°C

• Cold output temperature:  18.9°C

• Hot output temperature: 30.4°C

• Case cold side: 17.5°C

• Case hot side: 42.0°C