How a current creates a temperature difference
The tile works through the thermoelectric effect: when electric current passes through certain materials, it carries heat along with it. Inside a typical thermoelectric module, small semiconductor elements are arranged so that current moves through them in sequence. At one set of junctions, charge carriers absorb thermal energy; at the other, they release it. The result is a temperature difference across the module, not cold produced from nothing.
Reverse the current, and the direction of heat transfer reverses too. The same tile can therefore warm or cool a surface, depending on how it is wired. That makes it useful where a compact, precisely controlled temperature change matters more than moving a large volume of air.
Why the hot side matters
Cooling depends on removing heat from the hot face. It must shed both the heat drawn from the object being cooled and the electrical energy supplied to the tile. If that heat builds up, the hot face gets hotter, the temperature difference shrinks, and the cold face becomes less effective. A metal heat sink, often paired with a fan, gives the heat a larger surface from which to escape.
This is the key design tradeoff: the tile has no moving parts and can switch quickly between heating and cooling, but it still needs a route for heat to leave. In a small cooler, the hot-side heat sink is not an accessory—it is what allows the cold side to stay cold.
