Peltier are solid state heat pumps shaped like a thin sandwich. Power is input (usually 12vdc) and one side
gets cold while the other side gets warm. One module can usually create about 25 degrees F of temperature
difference between the two sides. The effect is limited by the amount of "waste heat" the module generates
simply by being powered on. As the hot side heats up, it raises the temperature on the cool side to maintain
the temperature difference. So this heat, in addition to the heat drawn from the cool side, must be radiated
away on the hot side, to keep it running efficiently. A typical 12v peltier draws 2 amps, producing 24 watts
of waste heat.
The obvious idea to stack two on top of each other to double the temperature difference is often impractical,
as adding a second module doubles the amount of waste heat being generated and considerably raise the temp of
the hot side of the output module
A typical peltier module is about 4x4 cm, and about 3mm thick. The faces are made of aluminum oxide, and are
smooth and hard. Use of heat sink compound (simular to what's used on a computer CPU) is suggested when a
heat sink is being connected, to increase the efficiency of thermal transfer. A smaller heat sink can also be used
on the cold side to improve cooling. If the cool side is in a humid environment it may create condensation,
which must be managed. (ice is also possible inder optimal conditions) Although hard, the faces are also very
brittle, and will crack if subject to impact or focused stress.
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