International. Researchers from the UK and Spain have identified an eco-friendly solid that could replace the inefficient gases and pollutants used in most refrigerators and air conditioners.
When put under pressure, neopentyl glycol plastic crystals produce enormous cooling effects, so much so that they are competitive with conventional refrigerants. In addition, the material is economical, widely available and works close to room temperature.
"HFC and HC-based refrigerators and air conditioners are also relatively inefficient," said Dr Xavier Moya of the University of Cambridge, who led the research with Professor Josep Lluís Tamarit, from the Universitat Politècnica de Catalunya. "That's important because refrigeration and air conditioning currently consume one-fifth of the energy produced worldwide, and the demand for refrigeration is only increasing."
To solve these problems, materials scientists around the world have looked for alternative solid refrigerants. Moya, a Royal Society researcher in Cambridge's Department of Materials Science and Metallurgy, is one of the leaders in this field.
In their recently published research, Moya and collaborators from the Universitat Politècnica de Catalunya and the Universitat de Barcelona describe the enormous thermal changes under pressure achieved with plastic crystals.
Conventional cooling technologies are based on the thermal changes that occur when a compressed fluid expands. Most cooling devices work by compressing and expanding fluids such as HFCs and HCs. As the fluid expands, its temperature decreases, cooling its surroundings.
With solids, cooling is achieved by changing the microscopic structure of the material. This change can be achieved by applying a magnetic field, an electric field or by mechanical force. For decades, these caloric effects have diminished due to the thermal changes available in fluids, but the discovery of colossal barocaloric effects in a plastic crystal of neopentyl glycol (NPG) and other related organic compounds has leveled the playing field.
Due to the nature of their chemical bonds, organic materials are easier to compress and NPG is widely used in the synthesis of paints, polyesters, plasticizers and lubricants. Not only is it widely available, but it's also inexpensive.
NPG molecules, composed of carbon, hydrogen and oxygen, are almost spherical and interact with each other weakly. These loose bonds in their microscopic structure allow molecules to rotate relatively freely.
The word "plastic" in "plastic crystals" does not refer to its chemical composition, but to its malleability. Plastic crystals lie on the boundary between solids and liquids.
NPG compression produces unprecedented thermal changes due to molecular reconfiguration. The temperature change achieved is comparable to those commercially exploited in HFC and HC.
The discovery of colossal barocaloric effects in a plastic crystal should bring barocaloric materials to the forefront of research and development to achieve safe and environmentally friendly cooling without compromising performance.
Moya is now working with Cambridge Enterprise, the commercialization arm of the University of Cambridge, to bring this technology to market.
Data Source Provider: University of Cambridge.
