Below -40°C with stacked Peltier thermoelectric coolers

In this video I show you what temperatures you can reach by sandwiching two Peltier elements together. The layers are the following: [Aluminium water cooling block][TEC12715][TEC12706][Air]. So, the cold side of the TEC12706 is exposed to air, the hot side of it is connected to the cold side of the TEC12715 and the hot side of the TEC12715 is connected to the aluminium water cooling block. All components are glued together with thermal grease. The exposed surface is measured by an infrared thermometer.

Please note that this is a very inefficient way of cooling! You can use it to cool down small volumes slowly, but it will never be as efficient as a compressor-based refrigerator. However, if you can afford low efficiency, and you need something which is noise and vibration free, then this is your way of cooling. For example, Peltier-based cooling is very often used when you want to cool some semiconductor-based detector (Silicon-drift detector). But, you can also make a small cooler for your drinks or just play around and watch the ice forming on the surface.

ATTENTION: As one of the viewers pointed it out, the currents are suspiciously high. I checked it, and the thing is that the built in power meter of the power supply, tends to overestimate the current by approximately 2 A at higher currents. The error is not linear, so it is difficult to say where it is starting to deviate from the real current. I will make a video later with properly measured values. 2020/03/01