In the face of relentless heat waves over the past three years, the demand for air conditioning (AC) is projected to surge. The International Energy Agency anticipates that the global number of AC units will triple by 2050. While this surge in AC use may contribute positively to public health—potentially preventing up to 200,000 premature deaths annually, according to a Lancet study—it raises significant environmental concerns. Currently, traditional air conditioning accounts for approximately 7% of global electricity consumption and 3% of greenhouse gas emissions. Moreover, improper disposal of these units can release potent refrigerants that have a much higher global warming potential than carbon dioxide.
To address these challenges, scientists and innovative startups are exploring solid-state cooling technologies, which are already implemented on a smaller scale in applications like mini-fridges and electric vehicle batteries. Unlike conventional AC systems that utilize compressors and fans to circulate refrigerants, solid-state cooling operates by transferring heat through conductive materials such as gadolinium and bismuth telluride, potentially offering a cleaner and more efficient alternative.
However, a critical question looms: can solid-state systems achieve the efficiency of traditional AC? As Pramod Reddy, a mechanical engineering professor at the University of Michigan, points out, the efficiency disparities between solid-state coolers and conventional systems remain a significant barrier to widespread adoption. Various research efforts are underway to evaluate different solid-state cooling methods. Brooklyn-based Mimic Systems is piloting a thermoelectric cooling system in a Vancouver apartment, while Germany’s Magnotherm is set to test a magnetocaloric design in supermarkets. Other ventures, such as a Hong Kong team working on elastocaloric devices and the UK’s Barocal focusing on barocaloric systems, are also in the mix, showcasing a range of promising technologies.
Despite optimism, experts caution about the competitiveness of these solid-state technologies. Jeff Snyder from Northwestern University emphasizes that traditional HVAC systems currently achieve a coefficient of performance (COP) of around 3, meaning they effectively move three units of heat for every unit of energy consumed. In contrast, thermoelectric systems often perform poorly under high temperature differentials, limiting their applications to niche markets, such as car seat cooling. Efficiency alone may not dictate success; Lindsay Rasmussen from the Rocky Mountain Institute argues that the environmental impact of refrigerants used in conventional AC systems, like R410A, poses additional challenges. As researchers work to compare the long-term energy usage of solid-state and traditional systems, it becomes increasingly clear that even a modest market share for solid-state cooling could yield significant environmental benefits. While solid-state ACs may not completely replace traditional systems, their emergence could help mitigate the growing global demand for cooling in a warming world.
Source: These new solid-state ACs promise a cool future. Scientists aren’t so sure. via MIT Technology Review