These new solid-state ACs promise a cool future. Scientists aren’t so sure.

Scientists and startups are exploring solid-state cooling technologies as a potential alternative to traditional air conditioning (AC) systems, which contribute significantly to global electricity consumption and greenhouse gas emissions. Traditional AC units rely on compressors and refrigerants to transfer heat, while solid-state systems utilize conductive materials like gadolinium and bismuth telluride to move heat. This approach could theoretically offer cooling with fewer environmental side effects. However, a key challenge remains in matching the efficiency of conventional AC systems. Pramod Reddy, a professor of mechanical engineering at the University of Michigan, highlighted the ongoing question regarding the efficiency of solid-state coolers compared to typical thermodynamic cycles. Several pilot programs are testing different solid-state cooling methods. Mimic Systems, based in Brooklyn, is piloting its thermoelectric cooling system in a Vancouver apartment. The German company Magnotherm is testing a magnetocaloric system in supermarkets, which uses the magnetization and demagnetization of materials to transfer heat. Additionally, a team in Hong Kong has developed an elastocaloric device.