The thermoelectric cooler is also known as TEC or Peltier Module creates a temperature differential on each side. One side gets hot and the other side gets cool. They use to either warm something up or cool something down; above all, you can use either side. You can also take advantage of a temperature differential to generate electricity.
A thermoelectric cooler (TEC) module is a semiconductor-based electronic component that functions as a small heat pump. By applying the DC power source to a TEC, heat will be transferred from one side of the module to the other. It creates a cold and hot side. They are widely useful in industrial areas, for example, computer CPUs, CCDs, portable refrigerators, medical instruments, and so on.