Scientists Invented an Entirely New Way to Refrigerate

Say hello to ionocaloric cooling. It is a new method for lowering temperatures, holding the potential to fundamentally replace existing cooling mechanisms with a process that is inherently safer, significantly more energy efficient, and better for the planet.

Background and Context

The modern era of convenience, food preservation, and controlled climate is fundamentally reliant on refrigeration and air conditioning. For over a century, the overwhelming majority of cooling applications—from residential refrigerators and supermarket display cases to industrial chillers and the global cold chain—have operated using the same fundamental mechanism: the vapor compression cycle (VCC). This time-tested technology relies on the cyclic compression and expansion of a chemical refrigerant to transfer heat effectively. While incredibly successful and robust, the VCC is inextricably linked to two critical global challenges: immense energy consumption and catastrophic environmental damage caused by the refrigerants themselves.

The Environmental Toll of Conventional Refrigerants

The history of VCC refrigerants is a continuous cycle of necessary replacement driven by unforeseen environmental catastrophe. The earliest chemical refrigerants, such as ammonia and sulfur dioxide, were highly toxic or flammable, spurring the industry’s adoption of chlorofluorocarbons (CFCs) in the mid-20th century. CFCs, such as Freon, were initially hailed as a miracle solution because they were non-flammable and highly stable. However, their stability allowed them to reach the stratosphere, where they catalyzed the devastating depletion of the ozone layer. This led to the landmark 1987 Montreal Protocol, which mandated the global phase-out of CFCs and, subsequently, hydrochlorofluorocarbons (HCFCs).

The primary replacement for ozone-depleting substances has been hydrofluorocarbons (HFCs). While HFCs solved the immediate ozone crisis, they introduced an equally severe existential threat: they are potent greenhouse gases (GHGs). HFCs typically possess a Global Warming Potential (GWP) often thousands of times higher than carbon dioxide over a 100-year period. Consequently, a small leak from a single commercial or residential cooling unit can have a warming impact equivalent to burning tons of coal. Recognizing this dire threat to climate stability, the world adopted the Kigali Amendment to the Montreal Protocol in 2016, aiming to cut the production and consumption of HFCs by more than 80% over the next three decades. This stringent global mandate puts intense pressure on industry and academic researchers worldwide to identify and implement non-GHG cooling solutions immediately and at scale.

The current transition involves hydrofluoroolefins (HFOs), which have ultra-low GWP. Yet, these alternatives often come with significant compromises regarding flammability, toxicity, material compatibility, or system stability, perpetuating the high-risk cycle of relying on specialized, volatile chemical fluids operating under high pressure.

The Energy Crisis of Cooling

Beyond the problems inherent in refrigerant chemistry, the sheer scale of the energy required for cooling is rapidly becoming unsustainable. As global temperatures rise due to climate change, and as populations in developing nations gain necessary access to climate control and food preservation technologies, the global demand for refrigeration and air conditioning is surging. According to detailed estimates from the International Energy Agency (IEA), global energy demand specifically dedicated to cooling is projected to triple by 2050.

If efficiency improvements do not keep pace with this demand spike, this explosion in cooling consumption will require vast new power generation infrastructure and could catastrophically overwhelm existing electrical grids, particularly in hot, densely populated regions. Cooling systems already account for roughly 10% of global electricity consumption—a percentage that is set to rise dramatically and dangerously. Therefore, any viable successor to the VCC must not only eliminate harmful chemical refrigerants but must also operate with significantly improved energy efficiency to stabilize future electricity consumption.

The Search for Caloric Alternatives

Driven by these severe environmental and energy imperatives, researchers have been intensely focused on developing “caloric” cooling methods, often referred to as solid-state refrigeration. These advanced systems are designed to avoid traditional, chemical refrigerants entirely, instead relying on specialized materials that change temperature when subjected to an external physical field. Prominent examples of this research focus include:

• Magnetocaloric Cooling: This method utilizes a powerful magnetic field to manipulate the internal entropy of specialized ferromagnetic alloys. When the field is applied, the material heats up; when the field is removed, it cools rapidly.
• Electrocaloric Cooling: This technique involves utilizing an intense electric field to change the temperature of specific dielectric ceramic or polymer materials by polarizing the molecular structure.
• Mechanocaloric Cooling (or Elastocaloric): This process involves applying mechanical stress (such as stretching or compressing) to polymer-based materials, which causes internal changes in entropy that lead to heating or cooling.

While these alternative caloric methods represent a significant conceptual step toward cleaner cooling, they have consistently struggled with technical barriers related to scaling, overall system efficiency (especially when compared to latent heat changes), high manufacturing cost, reliance on scarce materials (like rare-earth elements in magnetocalorics), and the difficulty of achieving rapid, large-scale, and sustained heat transfer necessary for commercial applications. This long period of stagnation in practical implementation has created a clear and urgent niche for a fundamentally new approach—one that combines the simplicity of a non-toxic working fluid with the high thermal efficiency of a reversible, field-driven thermal process. This complex context sets the definitive stage for the revolutionary potential of ionocaloric cooling.

Key Developments: The Science of Ionocaloric Cooling

The successful journey toward ionocaloric cooling was driven directly by the global imperative to phase out hydrofluorocarbons (HFCs) and the inherent limitations that plagued other existing “green” refrigeration alternatives. While technologies like magnetocalorics and elastocalorics offered environmental promise, they often suffered from poor scalability, reliance on rare-earth materials, prohibitively high manufacturing costs, or significant mechanical fatigue during cycling. These systemic hurdles required a completely fresh, electrochemical approach to thermal management.

1. The Establishment of the Theoretical Framework

The first true key development was the establishment of the theoretical framework, which hypothesized that electrochemistry could be leveraged to efficiently drive massive, reversible changes in latent heat. Unlike traditional solid-state cooling methods that rely on subtle changes in magnetic alignment or stress application (which primarily affect specific heat capacity), ionocaloric cooling uniquely exploits the highly energetic phase transition of a bulk material—specifically, the transition between its liquid and solid states.

Researchers posited that if ions, usually dissolved in a liquid electrolyte, could be selectively inserted into or extracted from a specific solid electrode material using an applied voltage, the sudden physical restructuring of the solid crystal lattice would demand or release significant amounts of energy—known as latent heat. This concept elegantly redefined how electrical energy could be used to manage thermal energy with exceptional efficiency, circumventing the critical limitations of caloric methods that rely only on minor specific heat capacity changes.

2. Identification of Functional Material Pairs

The second pivotal step involved the identification of functional material pairs capable of exhibiting a large and useful thermal change upon electrochemical cycling. For the process to be practical for widespread adoption, the materials needed to be safe, globally abundant, and demonstrate a substantial entropy change during the phase transition.

The breakthrough came with the utilization of a specific salt dissolved within a widely used solvent, ethylene carbonate, which is already common in non-aqueous battery applications. The core insight involved exploiting the physical principle of freezing or melting point depression caused by the selective movement of ions. When an electrical potential is applied across the ionocaloric cell, the ions (such as iodide) are forced to mix or electrochemically dissolve into the solid structure of the solvent. This ion intercalation rapidly lowers the melting point of the mixture, causing the solid material to instantly melt. Crucially, this melting process is highly endothermic, meaning it absorbs a substantial amount of latent heat from its surroundings—creating the powerful cooling effect. When the voltage polarity is reversed, the ions are efficiently pushed out of the solid matrix, allowing the material to rapidly solidify and simultaneously release the captured heat elsewhere (the heat rejection phase).

3. Quantifiable Thermal Performance

Quantitatively, this demonstrated an extremely impressive thermal shift. Early proof-of-concept experiments showed that the ionocaloric cycle could induce a temperature change of up to 25 degrees Celsius using only modest voltage inputs, achieved simply by transitioning the material between its solid and liquid states. This magnitude of cooling lift is comparable to, and in some thermodynamic metrics superior to, conventional solid-state cooling techniques, confirming the practical viability of the process for commercial refrigeration. This development proved that the technology could achieve a significant thermal capacity, often measured in hundreds of Joules per gram, which is vital for meeting the demanding requirements of commercial and industrial refrigeration.

4. Safety and Low-Pressure Operation

A further critical development was the confirmation of the process’s inherent safety and environmental superiority. Since the technology utilizes benign, widely available, and non-flammable materials (many derived from established battery chemistry), it completely eliminates the risks associated with handling high-pressure, ozone-depleting, or potent greenhouse gases used in traditional vapor compression systems. Unlike toxic ammonia or potent HFCs, the cooling material itself is electrochemically active and environmentally neutral. Furthermore, the system operates at very low pressures, significantly reducing the engineering complexity, material stress, and specialized component costs traditionally associated with high-pressure refrigeration cycles, enabling simpler, more durable, and cheaper manufacturing. The robust combination of large temperature lift, material sustainability, and low-pressure operation solidifies ionocaloric cooling as a truly disruptive and scalable technology in the global thermal management landscape.

Stakeholders and Impact

The introduction of ionocaloric cooling represents not merely an incremental improvement but a fundamental paradigm shift in thermal management systems worldwide. Because refrigeration and air conditioning account for approximately 15% of global electricity consumption—a figure projected to dramatically triple by 2050—any innovation promising higher efficiency and the complete elimination of potent greenhouse gases will have profound, systemic impacts across economic sectors, policy landscapes, and public life.

The Manufacturing Sector

Manufacturers of HVAC (Heating, Ventilation, and Air Conditioning) and refrigeration equipment are the most immediate stakeholders. The mandate for transitioning away from HFCs (under the Kigali Amendment) is creating an enormous market vacuum for safe, high-performance alternatives. Ionocaloric technology offers a clear, differentiated product path.

• Re-tooling and Design: Ionocaloric systems require radically different component designs than traditional VCC systems. This necessitates significant investment in new materials science, electrochemical engineering expertise, and specialized manufacturing lines, potentially creating a new, highly competitive sub-sector of the cooling industry.
• Cost Efficiency: The low-pressure operating environment simplifies equipment casings and sealing requirements, potentially lowering long-term manufacturing costs, maintenance complexity, and material demands compared to high-pressure VCC units.
• Market Leadership: Companies that successfully commercialize efficient ionocaloric units stand to capture significant market share in both the residential and industrial cooling markets, positioning themselves as leaders in sustainable technology.

Policy and Regulatory Bodies

International bodies, national governments, and regional regulatory agencies are intensely focused on climate mitigation. Ionocaloric technology directly supports critical climate goals:

• Meeting Kigali Targets: By providing a genuinely zero-GWP alternative, ionocaloric cooling offers a reliable mechanism for countries to meet or exceed their mandated HFC phase-down schedules, avoiding costly penalties and strengthening climate diplomacy efforts.
• Energy Efficiency Standards: If ionocaloric systems prove to be substantially more energy efficient than current VCC technologies (as preliminary data suggests), regulatory agencies like the Department of Energy (DOE) will likely update minimum energy performance standards (MEPS) for cooling appliances, driving broader adoption.
• De-risking the Cold Chain: Eliminating volatile, high-pressure refrigerants simplifies regulations surrounding storage, transport, and disposal, making the global food and pharmaceutical cold chain safer and more sustainable.

Energy Grids and Utility Companies

The projected tripling of cooling demand by 2050 poses the single greatest threat to global electrical grid stability.

• Load Reduction: Mass adoption of highly efficient ionocaloric systems would significantly slow the projected growth rate of electricity demand for cooling, potentially mitigating the need for billions of dollars in new power plant construction and grid hardening.
• Peak Demand Management: Many cooling systems contribute heavily to dangerous peak electricity loads during hot summer afternoons. More efficient technologies reduce peak strain, enhancing grid reliability and reducing the likelihood of brownouts or blackouts in vulnerable, dense urban areas.

Consumers and Commercial Users

The end-users, from homeowners to large-scale data center operators, will experience tangible benefits:

• Lower Operating Costs: Improved energy efficiency translates directly into lower electricity bills for consumers and substantial operating cost savings for commercial enterprises with massive cooling requirements (e.g., supermarkets, server farms, hospitals).
• Safety and Maintenance: Low-pressure, non-flammable, non-toxic refrigerants reduce maintenance hazards and simplify servicing protocols.
• Durability and Longevity: As ionocaloric systems avoid highly corrosive or high-pressure components, they are expected to offer superior reliability and potentially longer lifespans than traditional systems, leading to a reduced environmental footprint from equipment manufacturing and disposal cycles.