Researchers from the UK and Spain have identified an eco-friendly material that could replace the inefficient and polluting gases used in most refrigerators and air conditioners.
When put under pressure, plastic crystals of neopentylglycol (NPG) yield huge cooling effects, enough that they are competitive with conventional coolants, and in addition, the material is inexpensive, widely available, and functions at close to room temperature.
The gases used in the vast majority of refrigerators and air conditioners, hydrofluorocarbons and hydrocarbons (HFCs and HCs) are toxic and flammable, and when they leak into the air, they also contribute to global warming.
Dr Xavier Moya, from the University of Cambridge, said: “Refrigerators and air conditioners based on HFCs and HCs are 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.”
To solve these problems, materials scientists around the world have sought alternative solid refrigerants, and Moya is one of the leaders in this field.
The research, which was done in collaboration with researchers from the Universitat Politecnica de Catalunya and Universitat de Barcelona, describes the enormous thermal changes under pressure achieved with plastic crystals.
Conventional cooling technologies rely on the thermal changes that occurs when compressed fluid expands, as most cooling devices work by compressing and expanding fluids such as HFCs and HCs, and as the fluid expands, it decreases in temperature, cooling its surroundings.
With solids, cooling is achieved by changing the material’s microscopic structure, a change which can be achieved by applying a magnetic field, and electric field, or through mechanical force.
For decades, these caloric effects have fallen behind the thermal changes available in fluids, but the discovery of colossal barocaloric effects in a plastic crystal of NPG and other related organic compounds has levelled the playing field.