# What are the limits of Peltier cells?

I am doing a project for the university.

The project consists of a temperature controller in a glass chamber. The objective is a controllable temperature in a range of 0 - 100 degrees Celsius. The chamber volume is about 5 liters.

For the heating operation, I am going to use a typical heat resistor.

For the cooling operation, I am going to use a Peltier device. I have my reasons for not use this in the heating operation (I will be using a buck converter with fixed polarity.)

My question is about the following case:

• I heat the chamber to 100 degrees, once in the permanent regiment, it is possible to turn on the Peltier device to cool the chamber to 0 degrees (for example).
• What happens with the typical charts in the datasheets of the Peltier device, the dT is negative?
• Is an operation like this possible?
• Can somebody give me an abstract of the behavior of the Peltier cell in this situation?

The Peltier will produce a reverse voltage of maybe a couple of volts max, so your converter has to be happy with that situation.

100°C is close to the maximum temperature of cheaper Peltier units. Attempting to cool from that temperature means that the hot side will have to get much hotter than 100°C, especially so given the miserable efficiency of TEC coolers, so the device may be damaged. Maybe you can find a device which is rated and characterized for that type of operation but the heat loss through the TEC's high thermal conductance is so large you can just let the heat flow from the chamber to your heatsink/fan without power (and generating a decreasing voltage) until it gets closer to room temperature.

• Spehro, thanks for the answer. Okay... then i have to select a peltier cell that supports very high temperatures (170 degrees example) ? Or you recommend the free evolution of the system to the ambient temperature and the consecutive on of the cooling system? Oct 17, 2021 at 0:29
• Maybe both would be good. Oct 17, 2021 at 10:41

I heat the chamber to 100 degrees, once in the permanent regiment, it is possible to turn on the Peltier device to cool the chamber to 0 degrees (for example).

Yes. Indeed, the chamber will cool towards ambient temperature all on its own, even without using the Peltier cooler. The Peltier cooler will then be able to cool below ambient. Whether it can cool down to 0 C we can't answer because we don't know the amount of insulation around the chamber, the power of the Peltier cooler, and whether there are sources of heat inside the chamber.

What happens with the typical charts in the datasheets of the Peltier device, the dT is negative?

Sorry, this question is unclear. Please clarify.

Is an operation like this possible?

Sure.

Can somebody give me an abstract of the behavior of the Peltier cell in this situation?

As current flows through it, it pumps heat from one side to the other.

• Thanks Andrea, mi question is related with the following situation: turn on the cooling peltier system with a 100 degrees temperature inside the chamber. In this case, my cold side is at high temperature than my hot side (outside the chamber). In this case, we have a dT < 0 and the datasheets of al the peltier cells that i see doesnt include this range. Oct 17, 2021 at 0:25
• " turn on the cooling peltier system with a 100 degrees temperature inside the chamber". Don't. Doing so is wasteful, as it generates more heat outside the chamber, and may overheat the "cold" side of the cooler. Instead, wait for the temperature to drop to reasonable levels first, on its own, through convection. Heck, open a vent to speed-up cooling down to room temperature. Only when the chamber drops to close to ambient temperature, turn on the Peltier cooler. Oct 17, 2021 at 17:17