Multi-stage of TEC

The maximum temperature difference of a single-stage thermoelectric cooler with a standard can reach about 72℃. Some TEC can be stacked together by using mechanical method: the cold side surface of one TEC is installed on the hot side surface of another TEC, so the maximum temperature difference can reach 130℃. This stacking is called the cascade or multi-stage cooler layout. In general, multi-stage cooler has the shape of Pyramid, and a high level volume of TEC is smaller than the low level volume. However, regardless of the shape and the size, the low level TEC need to have a greater cooling capacity than the high level TEC do. Although currently, we have the ability to manufacture more than six or seven level multi-stage TEC, we generally use the two to fourlevel layouts. 

The key factors limiting the performance of multi-stage TEC relate to performance of temperature change of thermoelectric semiconductor materials. In most devices, using the performance of bismuth telluride alloy, optimal value appeases at 70℃, and under low temperature, the performance will decrease. Generally speaking, with the increase of multi-stage cooler series, the added value of temperature difference will be smaller and smaller.

The establishment of a multi-stage cooler model: comparing to single stage TEC, the establishment of multi-stage TEC is more complex. In the multi-stage coolers, the temperature between two adjacent levels is very important, if you don’t know the temperature, the multi-stage cooler stage will not be established. And with the series increasing, the process of thermal analysis will become more and more complicated.