Thermoelectric heat pump

Thermoelectric heat pumps use the thermoelectric effect, specifically the Peltier effect, to heat or cool materials by applying an electrical current across them. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current. Such an instrument is also called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC) and occasionally a thermoelectric battery. It can be used either for heating or for cooling, although in practice the main application is cooling since heating can be achieved with simpler devices (with Joule heating).

Thermoelectric temperature control heats or cools materials by applying an electrical current across them. A typical Peltier cell absorbs heat on one side and produces heat on the other. Because of this, Peltier cells can be used for temperature control. However, the use of this effect for air conditioning on a large scale (for homes or commercial buildings) is rare due to its low efficiency and high cost relative to other options.

This technology is far less commonly applied to refrigeration than vapor-compression refrigeration is. The primary advantages of a Peltier cooler compared to a vapor-compression refrigerator are its lack of moving parts or circulating liquid, very long life, invulnerability to leaks, small size, and flexible shape. Its main disadvantages are high cost for a given cooling capacity and poor power efficiency (a low coefficient of performance or COP). Many researchers and companies are trying to develop Peltier coolers that are cheap and efficient.

Thermoelectric coolers operate by the Peltier effect (one of three phenomena that make up the thermoelectric effect). A thermoelectric module is made from three components: the conductors, the legs, and the substrate. Many of these modules are connected electrically in series, but thermally in parallel. When a DC electric current flows through the device, it brings heat from one side to the other, so that one side gets colder while the other gets hotter.

The hot side is attached to a heat sink to limit its temperature increase, while the cold side goes below the ambient temperature. In special applications, multiple coolers can be cascaded or staged together for lower temperature, but overall efficiency (COP) drops significantly. The maximum COP of any refrigeration cycle is ultimately limited by the difference in temperature between the hot and cold side. The higher the temperature difference, the lower the maximum theoretical COP. Both temperatures depend on the rate of heat transfer to or away from the device as well as heat movement driven within.

A typical Peltier cell based heat pump can be used by coupling the thermoelectric generators with photovoltaic air cooled panels. Considering the system with an air plant that ensures the possibility of heating on one side and cooling on the other. By changing the configuration it allows both winter and summer acclimatization. These elements are expected to be an effective element for zero-energy buildings, if coupled with solar thermal energy and photovoltaic with particular reference to create radiant heat pumps on the walls of a building.

This acclimatization method ensures the ideal efficiency during summer cooling if coupled with a photovoltaic (PV) generator. The air circulation could be also used to cool PV modules.

The most important engineering requirement is the accurate design of heat sinks to optimize the heat exchange and minimize the fluiddynamic losses.