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Apparently Solid-State Trumps Fluids for Cooling

Mechanical Cooling Without Big Environmental or Dollar Costs

Credit: Courtesy

With increasing temperatures, the demand for air conditioning is growing around the planet. The refrigerant compounds used in cooling equipment are the number-one contributor to climate change, according to Paul Hawken’s recent book, Drawdown, The Most Comprehensive Plan Ever Proposed to Reverse Global Warming. 

The 1987 Montreal Protocol was a binding international agreement to phase out the use of ozone-depleting chemicals to save the earth’s ozone layer. The replacement compounds, however, have powerful heat-trapping properties, thousands of times more potent than carbon dioxide. Consequently, an amendment to the Montreal Accord was internationally ratified in 2016. Known as the Kigali Amendment, it is expected to have an impact equal to or greater than the Paris Climate Accord of 2015, in part because it is binding on all signatories. There is already concern, however, that the allowed replacement chemicals may not achieve the goals set forth in the Agreement — reducing warming potential with higher energy efficiency. In addition, all are turning out to be costly.

A collaboration of scientists from Cambridge University in England, two universities in Spain, and one in China have developed a substitute for all the gases used in cooling equipment, even the most recent ones attempting to comply with the Kigali requirements. All cooling gases rely on compression and expansion to produce the desired cooling effect. In moving through these cycles, these hydrofluorocarbons and hydrocarbons require a lot of energy, a fifth of all the energy consumed worldwide. Plus, they are toxic, flammable, and damaging to the environment when they escape.

This scientific team has been able to get big cooling effects by putting plastic crystals (neopentyl glycol) under weak pressure by means of a magnetic or electric field or even by mechanical pressure. The microscopic structure of these crystals can be altered under small compression, leading to a large caloric phase change. In other words, the crystals get cold very fast. These inexpensive organic crystals are widely used in manufacturing and are thus readily and inexpensively available. 

The team is currently working on the commercialization of this technology and on bringing it to market. This holds the promise of safer, greener, and more efficient cooling systems. The goals of the Kigali Amendment may yet be met or even exceeded, perhaps sooner and at much reduced cost than anticipated. If this new technology is widely adopted, our food will continue to be preserved for long periods of time and cooling quite likely will be brought to many hot regions of the planet, making them as comfortably habitable as any temperate area. Best of all, these scenarios could happen with almost no contribution to global warming.


Dennis Allen is chair of Allen Construction, an employee-owned company committed to building and operating sustainably. He also serves as chair of the Dean’s Council at the Bren School of Environmental Science & Management at UCSB and as a boardmember of the Community Environmental Council.

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