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 without refrigerants. This approach could theoretically reduce environmental side effects associated with conventional ACs. However, a key challenge remains in matching the efficiency of solid-state coolers to that of conventional thermodynamic cycles, according to Pramod Reddy, a professor of mechanical engineering at the University of Michigan. Several pilot programs are testing different solid-state cooling methods. Mimic Systems in Brooklyn is piloting a room-scale thermoelectric cooling system in a Vancouver apartment. 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, though details on its implementation are still emerging. The International Energy Agency projects a tripling of AC units by 2050, highlighting the urgency for more sustainable cooling solutions, as current AC usage accounts for 7% of global electricity and 3% of greenhouse gas emissions.