Three Distinctly Different Refrigeration Cycles

The cycle shown on top is the conventional refrigeration cycle used by household refrigerators and air conditioners. Such a cycle utilises the phase changes of a refrigerant such as "freon" to move heat from one volume to another.

The cycle just below the conventional refrigerant cycle, is an electromagnetic refrigerant cycle, which uses switched electromagnetic fields to chill a magnetocaloric material. The electrogmagnetic cycle is supposed to save at least 20% of the energy used in refrigeration, compared to the conventional cycle.

The cooling cycle shown below is based upon the compression and de-compression of a special solid material, a Nickel Manganese Indium, or Ni-Mn-In alloy developed by a team of Spanish researchers.

Until recently, the most promising materials for applications in this field were giant magnetocaloric materials, which change temperature under the influence of an external magnetic field. The authors of this new study show that application of a moderate hydrostatic pressure to a nickel-manganese-indium alloy (Ni-Mn-In) produces results comparable to those achieved with the most effective magnetocaloric materials.
According to Lluís Mañosa, a professor with the Department of Structure and Constituents of Matter at the UB and principal investigator of the study, "the aim of this field of research is to identify materials that are efficient, economic and environmentally respectful, and the advantages of the alloy used in this study is that all of the component materials meet these requirements."
In addition, Antoni Planes, a professor with the same UN department, explains that, "this type of material can produce much greater caloric effects with only slight variations in pressure, which makes it ideal for domestic refrigeration systems (refrigerators, air conditioning, etc.)." When these alloys are submitted to an external field, either magnetic or pressure, the material undergoes a solid-state phase transition, and Lluís Mañosa explains that, "this phase change generates a considerable latent heat exchange." _ScienceDaily

The "phase change principle" is analogous to that used for conventional refrigerants, but occurs in a solid state material, and is called a solid-state phase transition. According to the authors, the Ni-Mn-In alloy can undergo a solid-state phase transition in response to either pressure or a magnetic field.

This method of refrigeration could offer multiple advantages over conventional refrigeration and air conditioning:

1. At 20 to 30% more efficient, it will save power costs.
2. The "refrigerant" is not likely to leak or become contaminated or incorrectly mixed.
3. There will be no danger to the ozone layer or of "global warming" from solid state refrigerants.
4. Design, installation, and servicing of systems should be much simpler.
5. The systems should last longer with fewer maintenance problems.
6. Disposal of obsolete systems will be simpler and less costly.

We are still looking for the perfect form of cooling and refrigerating, but the new solid-state approaches appear to be in the right direction.