Apr 19 2019
Scientists from Spain and the United Kingdom have discovered an eco-friendly solid that could be an alternative to the ineffective and polluting gases used in most air conditioners and refrigerators.
Image credit: University of Cambridge
When subjected to pressure, plastic crystals of neopentylglycol produce adequately immense cooling effects that they could compete with traditional coolants. Furthermore, the material is economical, extensively available, and operates at close to room temperature. The study has been reported in the journal Nature Communications.
The conventional gases used in the significant majority of air conditioners and refrigerators—hydrocarbons and hydrofluorocarbons (HCs and HFCs)—are inflammable and harmful. When they are released into the atmosphere, they also contribute to global warming.
Refrigerators and air conditioners based on HFCs and HCs are also relatively inefficient. That’s important because refrigeration and air conditioning currently devour a fifth of the energy produced worldwide, and demand for cooling is only going up.
Dr Xavier Moya, Royal Society Research Fellow, Department of Materials Science and Metallurgy, University of Cambridge
Moya led the study with Professor Josep Lluís Tamarit, from the Universitat Politècnica de Catalunya.
To overcome these issues, materials scientists worldwide have looked for alternative solid refrigerants. Moya, a Royal Society Research Fellow in Cambridge’s Department of Materials Science and Metallurgy, is one of the best experts in this area.
In their newly reported study, Moya and partners from the Universitat Politècnica de Catalunya and the Universitat de Barcelona explain the huge thermal variations under pressure obtained with plastic crystals.
Traditional cooling methods depend on the thermal variations that happen on expanding a compressed fluid. Majority of the cooling devices operate by compressing and expanding fluids such as HCs and HFCs. When the fluid expands, it reduces the temperature, thus cooling its surroundings.
When it comes to solids, cooling is attained by varying the material’s microscopic structure. This variation can be obtained by applying an electric field, a magnetic field, or through mechanical force. For several years, these caloric effects have lagged behind the thermal variations found in fluids; however, the finding of colossal barocaloric effects in a plastic crystal of neopentylglycol (NPG) and other associated organic compounds has evened out the playfield.
Organic materials are easier to compress because of the nature of their chemical bonds, and NPG is extensively employed in the production of polyesters, paints, lubricants, and plasticizers. It is extensively available as well as inexpensive.
NPG’s molecules, made up of hydrogen, oxygen, and carbon, are almost spherical and there is only weak interaction with each other. These loose bonds in its microscopic structure allow the molecules to spin quite freely.
The term “plastic” in “plastic crystals” indicates its malleability and not its chemical composition. Plastic crystals are present at the boundary between liquids and solids.
By compressing NPG, exceptionally great thermal variations can be obtained due to molecular reconfiguration. The temperature variation attained is analogous to those utilized commercially in HCs and HFCs.
The breakthrough finding of colossal barocaloric effects in a plastic crystal should bring barocaloric materials to the vanguard of research and development to realize safe eco-friendly cooling without affecting performance.
Currently, Moya is working with Cambridge Enterprise, the commercialization arm of the University of Cambridge, to commercialize this technology.