Thermotunnel cooling

Thermotunnelung (English thermoelectric tunneling ) is a new physical principle for heat engines and heat pumps, based on the tunnel effect and has similarities with a thermocouple.

It is similar to the Seebeck - and the Peltier - effect. The estimated potential for cooling efficiency is around 55 % of the Carnot efficiency. Thus, the process would be slightly more efficient than a heat pump refrigerator. However, prototypes only achieve 5 % efficiency.

Principle

Rather than two different metals or semiconductors, such as to bring into contact with a thermocouple Thermotunneling method uses a vacuum between the materials. The vacuum they are well insulated with respect to the thermal conduction, although they (70 Å ) are only around 7 nm apart.

The electrons can tunnel through the vacuum of time. To facilitate this, may be applied at the interfaces of the microstructures, or specific dopants. The microstructures prohibit various low-energy quantum states. Thereby, the electrons are automatically at higher power levels and with a greater probability that tunneling through the gap.

Basic problems

Although the heat conduction through the lattice vibrations through the vacuum gap is completely eliminated, but this may only be so wide that single electrons can quantum mechanically tunnel through this crack.

At first glance, this interruption of phonon heat conduction, ie, the heat conduction through the lattice vibrations to be extremely efficient. With a gap size which allows quantum mechanical tunneling, the electromagnetic forces, however, are so large that a virtually unimpeded transmission of the lattice vibration occurs due to electromagnetic coupling.

At ordinary temperatures at which such elements are to be used, the wavelengths of electromagnetic emissions in the range of a few hundred nanometers to a few micrometers. An effective decoupling of the lattice vibrations takes place only when the gap size is in the range of wavelengths. These sizes, however, a quantum- mechanical tunneling is virtually no longer possible.

History

The method was already known in the 1970s. It was at that time but not pursued because you could not make a very small distances between the metal plates.

Currently, the method of the Borealis Exploration Limited and General Electric is further developed. Borealis developed various manufacturing processes: When porous materials are used to realize the tunnel section. The electrons must have a mean free path, which is greater than the layer thickness, so that the tunneling probability is high enough in these materials. Another method makes use of a "lost" thin layer between the contacts, which is removed afterwards and leaves a thin gap.

General Electric is carried out on the active control of the distance of the piezoelectric actuators, such as used in the tunneling microscope. The goal is to develop a refrigerator or freezer, which was 2005, subsidized by the U.S. research and development program Energy Efficient Building Technologies.