As temperatures rise, the need for cooling is growing worldwide. Conventional cooling systems consume large amounts of electricity and use refrigerants with a high global warming potential. Caloric cooling could offer a sustainable alternative by using solid-state materials instead of conventional refrigerants. Researchers at Karlsruhe Institute of Technology (KIT), together with international partners, have analyzed the state of development of such systems. Their Review, published in Nature, shows the progress achieved so far and the challenges that still stand in the way of practical deployment. (DOI: 10.1038/s41560-026-02143-1)
According to the German Meteorological Service, June 2026 ended with a historic heat wave. As such extreme events become more frequent worldwide, energy demand for space cooling is expected to more than double by 2050. The rapid development of artificial intelligence is also increasing cooling demand, as more powerful data centers generate more waste heat and have to protect their servers reliably against overheating. Cooling is becoming increasingly important not only in buildings and data centers, but also in electronics, medicine, and logistics. So far, this demand has mainly been met by vapor-compression systems. Although mature, this technology consumes large amounts of electricity and can cause noise through its compressors.
Research by Dr. Jingyuan Xu shows that there are other ways to cool. The multiple award-winning early-career researcher heads the “Zero-Emission and Environmentally Friendly Heating and Cooling Technologies” research group at KIT’s Institute of Microstructure Technology (IMT). Her expertise also informs the current Review, which she led as the responsible author. “Caloric cooling offers two key advantages: It does not require refrigerants with a high global warming potential and can reduce energy consumption,” Xu explains.
Progress in Devices
Caloric cooling technologies use materials that heat up under external stimuli and cool down again when the stimulus is removed. Magnetic and electric fields can be used for this purpose, as can pressure or tensile strain. In a device, this change can be harnessed to absorb heat in one place and release it elsewhere, much like in a refrigerator.
Current prototypes show how far the field has developed. Some now achieve cooling powers that go beyond pure laboratory demonstrations: systems based on magnetic fields exceed three kilowatts, reaching a performance range relevant for larger cooling applications. Mechanically driven prototypes have passed the one-kilowatt mark. Smaller devices using electric fields could be suitable for electronics or wearables.
Despite major progress, a gap remains between the material and the cooling performance of the finished device: heat losses, material fatigue, and incomplete work recovery during the cooling cycle reduce overall performance. “The material can show large temperature changes in the laboratory,” says first author Dr. Nun Wang of IMT. “What matters, however, is how efficiently this effect can be used for cooling in a device.”
Roadmap for Practical Deployment
In their study, the researchers show what caloric systems still need in order to provide reliable cooling in everyday use. Durability is particularly important. Devices have to remain stable over many millions of cycles if they are to cool reliably for years. It is also crucial that they can absorb and release heat quickly and require as little energy as possible for the cooling cycle.
In the short term, caloric systems will not replace established cooling systems across the board. “At first, they will be of interest where conventional cooling reaches practical limits,” Xu explains. “This may be the case when devices need to operate very quietly or when refrigerants with a high global warming potential must be avoided.” Standardized testing and application-oriented demonstrators will show which systems are suitable for these uses.
Originalpublication
Wang, K., Seelecke, S., Sun, Q. et al. Caloric cooling devices and systems. Nat Energy (2026) DOI: 10.1038/s41560-026-02143-1
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