Pascal

A warming world requires more cooling. By 2050, the number of installed air conditioning units is expected to grow from 1.5 billion to 4 billion globally, mostly based on demand in China, India and Europe. The energy usage of all that will be gargantuan. Already, cooling and refrigeration draws an estimated 20% of the world’s electricity. But energy is not the only impact. Today’s HVAC technologies—including the latest heat pumps—rely on volatile hydrofluorocarbon refrigerants, which are potent greenhouse gasses. While this refrigerant gas isn’t released as part of normal operations, small amounts inevitably leak, with outsized climate effects. An estimated 2% of all warming impacts come from hydrofluorocarbon leaks from HVAC systems, making it equivalent to a gigaton-scale carbon problem.

Pascal, a startup with roots in Harvard’s Department of Chemistry and Chemical Biology, has identified a new class of solid refrigerants with the potential to eliminate the need for the greenhouse gasses that make existing HVAC technologies detrimental to the environment. Its fundamental research discovery is a group of phase-change materials that, under certain conditions, are two orders of magnitude more responsive to pressure than other solids. The remarkable performance of these wax-like solids allows for the engineering of cooling and heating devices that do not use greenhouse gasses, while also being smaller and more efficient than existing technologies. “Our refrigerants can be contained and controlled,” says co-founder and CEO Adam Slavney. “Because they are solids, they cannot get into the atmosphere, which means our systems will not cause additional global warming.” This innovation comes at a critical moment in the industry. The Kigali Amendment to the Montreal Protocol, signed by 147 states and the EU, gives legal teeth to the international effort to reduce the use of hydrofluorocarbons. But HVAC manufacturers are still struggling to identify and implement viable alternatives. “Pascal’s technology offers a new pathway for solving this intractable global problem,” says Slavney.

The most effective refrigerants store and release energy at high densities, without requiring large changes in pressure. Those characteristics allow HVAC systems to efficiently induce the large thermal changes needed for the refrigerant to carry heat between indoors and outdoors (or vice versa, in the case of heat pumps). Gasses work particularly well at this, because they respond readily to changes in pressure. But solids, in contrast, typically require the application of much greater pressure changes to induce similar temperature shifts. In practical applications, this has meant that solid refrigerant systems require larger pumps, pipes, and compressors—all of which has kept them prohibitively expensive and inefficient.

Pascal’s fundamental material innovation disrupts those long-held constraints on the use of solid refrigerants. The discovery arose out of Jarad Mason’s research group at Harvard, which is focused on identifying new materials that can address global challenges, related to both energy and human health. Working with fellow Pascal co-founders Slavney and Jinyoung Seo, Mason identified a class of solid materials that had extremely promising properties for use as refrigerants: they were unusually sensitive to pressure; their phase changes were reversible and durable; they were derived from readily available commodities; and they operated well in the temperature ranges typically required for heating and cooling. Mason, Slavney, and Seo’s subsequent transformative breakthrough was the discovery of a novel way of using pressure to induce phase transitions in these solids, allowing them to create the necessary temperature changes with reduced energy input and under commercially-relevant conditions. “Our threshold for viability was whether or not there was a pathway to making these solid refrigerants work using existing off-the-shelf HVAC compressors and other components,” says co-founder and CTO Jinyoung Seo. “And there definitely was.”

Pascal is commercializing these new solid refrigerants, honing in on the optimal formulations for use in heat pumps, air conditioners, refrigerators, and freezers. Pascal’s next-generation HVAC systems will require less refrigerant material to be pressurized, meaning they will operate 10-20% more efficiently than conventional gaseous systems. Yet because they work using small pressure changes, they can be manufactured within the existing industrial ecosystem, using parts from the conventional HVAC component supply chain. “We're changing what needs to be changed, and nothing beyond that,” notes Seo. “That lets us grow quickly and actually address the problem.”

The HVAC industry urgently needs alternatives to existing hydrofluorocarbon gaseous refrigerants, while continuing to meet the growing cooling needs of the planet. Pascal’s refrigerants are solid, and safe. ”You can throw our systems in the dump, you can smash them with a hammer—and none of that refrigerant is going to end up in the atmosphere,” says Slavney.