No noise, no chemicals: How solid-state AC units could change the way you cool your home

Inside a Vancouver apartment, a sleek, humming prototype installed beneath a window is quietly attempting a minor miracle: cooling a room without a drop of chemical refrigerant or a single rumbling compressor.

Built by Brooklyn-based startup Mimic Systems, the unit represents a radical departure from the architecture of modern climate control. It relies instead on thermoelectric cooling — running an electric current through conductive semiconductors to force heat from one side to the other. 

Global cooling paradox 

As the planet warms, the demand for relief is exploding. The International Energy Agency predicts the number of air conditioning units worldwide will triple by 2050. While artificial cooling is a literal lifesaver — preventing close to 200,000 early deaths in 2019 alone according to the Lancet Countdown — it carries a devastating environmental toll.

Cooling currently accounts for 7% of global electricity use and 3% of greenhouse gas emissions. Worse, standard units heavily rely on synthetic gases; the majority of US air conditioners utilize R-410A, a refrigerant with a global warming potential more than 2,000 times that of carbon dioxide. 

Shaking up the science of cool 

To break this feedback loop, scientists and startups are betting heavily on solid-state cooling. By manipulating materials like gadolinium, bismuth telluride, or advanced polymers, these systems aim to transfer heat via solid matter rather than chemical phase changes. In theory, eliminating the compressor removes the primary source of mechanical wear, leaks, and noise. 

Four distinct technologies are currently vying for supremacy: 

• Thermoelectric: Running an electric current through semiconductors to shift heat, currently being tested at room-scale by Mimic Systems. 
• Magnetocaloric: Heating and cooling materials by rapidly magnetising and demagnetising them. Germany’s Magnotherm plans to pilot this system inside a supermarket chain. 
• Elastocaloric: Cooling via the mechanical stretching and compressing of specialised materials. A research team in Hong Kong has built an elastocaloric device capable of dropping temperatures below 0°C. 
• Barocaloric: Utilising structural materials that change temperature in direct response to pressure changes, a method backed by the UK startup Barocal. 

The thermodynamic hurdle 

Yet, despite the influx of innovation, the laws of thermodynamics present a steep hurdle. Conventional air conditioners are highly optimised, typically operating at a Coefficient of Performance (COP) of around 3 — meaning they move three units of heat for every single unit of electricity consumed. 

"Most modern HVAC systems have a coefficient of performance, or COP, of around 3," notes Jeff Snyder, a professor at Northwestern University who studies electrical and thermal conductivity. Snyder cautions that thermoelectric systems historically underperform as the temperature gap between the inside and outside widens, making them brilliant for niche applications like cooling car seats, but deeply challenged when scaling up to whole houses. 

Pramod Reddy, a mechanical engineering professor at the University of Michigan who studies heat transfer, points out a deeper scientific frustration: "Nobody has completely figured out why these systems keep underperforming compared to conventional AC." 

Redefining the metrics of success 

However, efficiency in a vacuum may not be the final metric of success. Lindsay Rasmussen, a manager at Third Derivative — the Rocky Mountain Institute’s climate tech accelerator backing both Magnotherm and Mimic — argues that the focus must shift to holistic climate impacts. Solid-state devices suffer no catastrophic refrigerant leaks and possess far fewer moving parts, vastly extending their operational lifespan. 

Rasmussen stresses that the true test will not be a static COP recorded under ideal laboratory parameters, but rather the total "long-term energy draw compared with conventional units." While Mimic claims its thermoelectric room unit will match the annual energy consumption of standard ACs, alternative prototypes utilizing elastocaloric and barocaloric designs remain two to three years away from realistic room-scale deployment.