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Researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) developed a new way of heating and cooling that used electrically charged atoms or molecules, known as ions, to control changes between solid and liquid states. The method, called "ionocaloric cooling," was described in a study published in the journal Science.
The idea was based on a familiar example. When salt is spread on roads before a winter storm, it changes the temperature at which ice forms. The new method worked in a similar way by using ions to change the melting point of a material. This created a controlled phase change, which is the process of a material changing between solid and liquid. When the material melted, it absorbed heat from its surroundings. When it became solid again, it released that heat. This allowed heat to be moved from one place to another without using conventional refrigerant gases.
The study addressed a long-standing challenge in refrigeration: developing cooling systems that were energy efficient while using refrigerants that had little or no impact on global warming. Most refrigerators and air conditioners use vapor-compression refrigeration, where a refrigerant gas is compressed and expanded in a continuous cycle to absorb heat from one place and release it somewhere else. Many of these systems use hydrofluorocarbons (HFCs), synthetic refrigerant gases with a high global warming potential (GWP), a measure of how much heat a greenhouse gas can trap in the atmosphere compared with carbon dioxide. The ionocaloric system instead used only solid and liquid materials, removing the need for refrigerant gases.
