Bold claim: a breakthrough cooling method could ditch gas-based refrigerants and their climate impact, offering a safer, more efficient alternative. Here’s the rewritten, fully unique version that preserves all key details and context while clarifying concepts for newcomers.
A team of researchers has unveiled a radically new approach to refrigeration that could significantly reduce the environmental footprint of today’s cooling systems. This method, known as the ionocaloric cycle, generates cooling power without relying on greenhouse gases or energy-intensive compressors.
Instead of compressing a gas, the ionocaloric cycle uses a carefully chosen mix of charged particles (ions), an organic solvent, and a small amount of electricity to control when a material melts or solidifies. The heat is absorbed during melting and released during solidification, creating a cycle capable of cooling—and even heating—a space.
Developed by scientists at Lawrence Berkeley National Laboratory and the University of California, Berkeley, this technique holds the potential to make conventional air conditioning systems obsolete. Their findings, published in Science, suggest the ionocaloric cycle could achieve efficiency comparable to today’s best commercial systems while eliminating refrigerants with high global warming potential.
As lead author Drew Lilley explains, the refrigerant landscape remains a major challenge: there hasn’t been a proven solution that cools effectively, operates efficiently, stays safe, and minimizes environmental harm.
Cooling with ions rather than gas
Most modern cooling relies on a vapor compression cycle, where a refrigerant gas circulates in a closed loop, absorbing heat as it evaporates and releasing it when it condenses. However, the gases used—particularly hydrofluorocarbons (HFCs)—are among the most potent climate pollutants.
Many countries are phasing them out under agreements like the Kigali Amendment, which aims to reduce HFC emissions by about 80% over the next two decades. This has spurred a global search for safer, scalable, and eco-friendly refrigerants.
The ionocaloric system takes a different route. It employs a salt-and-solvent mixture—specifically sodium iodide and ethylene carbonate—and uses a low-voltage electric current to adjust ion concentration. When the ions are introduced, the mixture melts and absorbs heat; reversing the charge draws the ions away, causing solidification and heat release.
In laboratory tests, the researchers achieved a temperature change of about 25°C with less than one volt, a performance level higher than many other caloric cooling technologies. Because the working fluid remains liquid, it can be pumped and circulated like traditional refrigerants, offering easier scalability than many solid-state cooling approaches.
The inspiration, as described in a ScienceAlert overview, comes from the way salt can lower the melting point of ice. In the ionocaloric version, however, the ion concentration is precisely controlled electrochemically, enabling efficient temperature control without compressors.
Cleaner cooling—and possibly carbon-negative cooling?
A standout feature of the ionocaloric system is its refrigerant material. Ethylene carbonate can be produced using captured carbon dioxide, which opens the possibility of carbon-negative cooling. In other words, the process could remove CO₂ from the atmosphere rather than add to it.
There’s even a sense that refrigerants could move from “global warming potential zero” to “global warming potential negative.” According to Lilley, producing ethylene carbonate with CO₂ as an input could help achieve this negative footprint.
Compared with traditional HFCs or newer synthetic refrigerants like HFOs, this approach avoids combustion risks and long atmospheric persistence. It also eliminates the need for compressors, reducing energy use and system complexity.
Performance metrics and scalability
The team measured a coefficient of performance (COP) at roughly 30% of the Carnot efficiency, a standard benchmark in thermodynamics. While this is not yet at commercial-grade performance, it already surpasses many emerging caloric cooling contenders.
To make the system practical, the researchers turned to electrodialysis—an established technology used in desalination—to separate ions and reset the cycle. Current membrane resistance is a bottleneck when operating in organic solvents like ethylene carbonate, but tailoring membranes designed for organic solvents could dramatically improve power output, potentially boosting cooling capacity by up to two orders of magnitude.
Beyond cooling, the ionocaloric cycle could also enable space heating or industrial temperature control, suggesting year-round thermal management using a single clean energy source.
The researchers are exploring other salt–solvent combinations to optimize performance. A follow-up Science study introduced a liquid-state dipolarcaloric cycle using nitrate-based salts (such as ammonium nitrate and potassium nitrate), delivering temperature shifts up to 37.3°C and COPs up to 9.4 in optimized lab setups. Using water as a solvent in these systems could further boost efficiency.
Ravi Prasher, senior author of the study, notes that this is a brand-new thermodynamic cycle that blends concepts from multiple fields and has already demonstrated real-world feasibility.
Barriers and momentum
While the ionocaloric concept is still in early stages, the team has filed a provisional patent, and the technology is available for licensing. The next steps focus on scaling the system, improving material durability, and integrating the technology into compact cooling devices that could eventually supplement or replace current HVAC systems.
One challenge is the relatively slow ion transport due to current membrane designs. Most existing ion-exchange membranes are built for water-based systems, not organic solvents like ethylene carbonate. Developing low-resistance membranes tailored for this new context could unlock the full potential of ionocaloric cooling.
Despite these hurdles, the elegance of the idea—replacing volatile gases with safe, recyclable liquids and using electricity instead of compressors—positions ionocaloric cooling as a standout contender in the race to reinvent next-generation air conditioning.
Would you embrace a future where your air conditioner relies on salts, liquids, and electricity rather than gas-powered compressors? Is a carbon-negative refrigerant realistic, or is it still a distant possibility? Share your thoughts in the comments about how this technology could change homes, businesses, and the climate conversation.
