International. Researchers in the United Kingdom and Spain have identified an ecological solid that could replace the inefficient and polluting gases used in most refrigerators and air conditioners.
When put under pressure, the plastic crystals of neopentyl glycol produce enormous cooling effects, so much so that they are competitive with conventional refrigerants. In addition, the material is economical, widely available and works near room temperature.
"Refrigerators and air conditioners based on HFC and HC 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 a fifth of the energy produced worldwide, and the demand for refrigeration is only increasing."
To solve these problems, material scientists around the world have looked for alternative solid refrigerants. Moya, a researcher at the Royal Society in the Department of Materials Science and Metallurgy of Cambridge, is one of the leaders in this field.
In his recently published research, Moya and collaborators of the Universitat Politècnica de Catalunya and the University of 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 the application of a magnetic field, an electric field or by mechanical force. For decades, these caloric effects have decreased 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 its 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 is also economical.
NPG molecules, composed of carbon, hydrogen and oxygen, are almost spherical and interact weakly with each other. These loose links in their microscopic structure allow molecules to rotate with relative freedom.
The word "plastic" in "plastic crystals" does not refer to its chemical composition, but its malleability. Plastic crystals are at the boundary between solids and liquids.
NPG compression produces unprecedented thermal changes due to molecular reconfiguration. The temperature change reached is comparable with those commercially exploited in HFC and HC.
The discovery of colossal barocaloric effects in a plastic glass 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 marketing arm of the University of Cambridge, to bring this technology to market.
Source: University of Cambridge.