Current refrigerant technologies use gases like chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) to function. These gases pose a threat to global stability, given their warming and ozone depletion potential. To solve this issue, scientists like Dr. Drew Lilley are developing ways to perform refrigeration and heating without the need for environmentally hazardous gases, like ionocaloric refrigeration. For a transcript, please visit https://climatebreak.org/out-with-classic-refrigerants-and-in-with-ionocaloric-refrigeration-with-dr-drew-lilley/.
In 2020, nearly 90% of homes used air conditioning systems in the United States. Heating, ventilation and air conditioning (HVAC) systems are used by both homeowners and businesses alike, with their usage only expected to rise as climate change increases global temperatures. Refrigerant, a chemical compound that is capable of transitioning from liquid to gas and back again, has been an important part of indoor cooling systems since modern AC systems were invented in 1902. Its ability to cool as it vaporizes and heat up as it condenses facilitates heating and cooling. As part of both air conditioner and heat pump systems, refrigerant either helps transfer heat and humidity out of one’s home for conditioning or draws heat from outdoor air and brings it inside for heating.
Refrigeration technology has historically relied upon gases like chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) to promote cooling in appliances, due to their effectiveness at transferring heat within a refrigeration system. While effective, these gases are hazardous for the environment. HFCs have a global warming potential (GWP) that can be hundreds to thousands of times greater than that of carbon dioxide. Gaseous CFCs have a high ozone depletion potential (ODP), meaning there is less protection from the sun’s rays and greater exposure to UVB radiation, negatively impacting human and ecological health. Instead of relying upon harmful CFCs and HFCs in refrigeration technology, UC Berkeley researchers are on the cusp of developing a new alternative known as “ionocaloric” refrigeration, which utilizes salt water to provide cooling.
Created in 1987, the Montreal Protocol regulates the production and consumption of nearly 100 human made chemicals classified as ozone depleting substances (ODS). The Montreal Protocol mandated the eventual phase-out of CFCs and HCFCs, instead turning to HFCs as a replacement. Although HFCs do not deplete ozone, they were later found to have a significant GWP, prompting a recent amendment to reduce HFC usage by 80% in the next thirty years. As HFCs are phased out, ionocaloric cooling has been proposed as an alternative for refrigerant.
Ionocaloric cooling relies on the principle that liquids release energy, or heat, when solidified, and solids absorb energy when liquified. In an ionocaloric refrigerant system, a mixture of a liquid and salt is frozen and melted. When a current is added, ions flow and change the material from solid to liquid, which allows them to absorb heat from their surroundings. Similarly, when ions are removed, the material crystallizes into a solid, releasing heat. The mixture is easier to manage as it is never in a gas state and is unable to enter the atmosphere. Additionally, certain solvents like ethylene carbonate, which have been used to test the technology, can be carbon-negative due to their ability to be produced from CO2 supplied by carbon capture. This means that ionocaloric cooling can prevent current emissions with high GWP and ODP, while also removing emitted gases from the atmosphere.
Ionocaloric cooling has the potential to modify current HVAC systems, which rely upon high GWP gases that act as refrigerants. By using solid and liquid components as opposed to HFCs to function, ionocaloric refrigeration prohibits these harmful gases from ever entering the atmosphere. In addition to its cooling purposes, this technology can also be used for heating. Ionocaloric technology has the potential to compete with or even exceed the efficiency of gaseous refrigerant. Currently, ionocaloric cooling technology is still being developed. If proven successful, this innovative technology could transform the current landscape of HVAC systems.
As of now, ionocaloric cooling is not fully developed. Although the material cost for the salt water is cheap, it is unclear the cost of every component needed on a larger scale. The research currently being conducted for ionocaloric cooling experimentation is heavily subsidized. As it is still under R&D, this technology’s viability on a larger-market scale will be continually determined. To facilitate a transition away from gas refrigerants, ionocaloric cooling will likely need government incentives, such as consumer rebates, to make the technology competitive with conventional units.
In addition to being environmentally harmful, gas refrigerants have proven to be costly and difficult to dispose of. Dr. Lilley believes that ionocaloric cooling can thus be an advantageous solution in a variety of ways. The end of life management (or disposal) of output components from ionocaloric cooling will be much easier as it relies upon liquid inputs. Additionally, Lilley notes that there is no way to completely seal refrigerants from the atmosphere, so a liquid refrigerant eliminates that problem altogether. As the technology becomes more advanced, Dr. Lilley believes that initial cost concerns will fade with state subsidies and market adoption.
Dr. Drew Lilley is the CEO and co-founder of Caliion Technologies. He holds a PhD from UC Berkeley in Mechanical Engineering, where his research is focused on alternatives to current refrigerants. His main research focus is on the R&D process of solid-to-liquid ionocaloric cooling.
For a transcript, please visit https://climatebreak.org/out-with-classic-refrigerants-and-in-with-ionocaloric-refrigeration-with-dr-drew-lilley/.
Ethan: I’m Ethan Elkind, and this is Climate Break. Climate solutions in a hurry. Today’s proposal: replacing climate-damaging gas refrigerants in air conditioning units with cleaner, more efficient refrigeration. Traditional gas refrigerants—chlorofluorocarbons or CFCs, and hydrochlorofluorocarbons, or HCFCs, cause ozone depletion when released into the air, which exacerbates climate change. Dr. Drew Lilley, CEO of Calion Technologies, explains:
Dr. Lilley: Refrigerants are a huge component of climate change at the moment, and projected to get much worse. And for a traditional air conditioner that's used to, let’s say, cool a two or three bedroom home, that's going to be roughly like driving across the country 55 times. And so, a really easy solution uh would just be to use a different gas and liquid combination, you know, that it doesn't really have high global warming potential or ozone depletion potential or flammability.
Ethan: Whereas air conditioning units traditionally compress these harmful refrigerant gases to cool the air, Lilley’s technology instead applies an electric current to a mixture of a liquid and salt. The electricity changes the ion concentration in the liquid, which alters its melting point. That means the solution can stay frozen longer for cooling, and release more heat when it melts.
Dr. Lilley: When we change the ion concentration, it creates a heating or cooling effect. And so, we just have a completely new way to make things cold that doesn't rely on compressing a gas. If you don't compress a gas, we don't have refrigerants, and then we don't have anything harmful to the atmosphere or human health.
Ethan: To learn more about new refrigerant technologies, visit climatebreak.org.