Caloric effects are used to cool solid- and liquid-state materials. Materials undergo some type of phase shift. The University of California Berkeley and Lawrence Berkeley National Laboratory discovered that ions can be used in solutions to regulate the melting or crystallization of materials, creating an “ionocaloric” cycle.
It is crucial that countries find a way to replace harmful refrigerants in order to achieve their climate change goals.
This agreement vows that signatories will reduce hydrofluorocarbons’ (HFCs), production and consumption by at least 80 percent over the next 25-years.
HFCs, powerful greenhouse gases found in refrigeration and air conditioning systems can trap heat up to tens of thousands times more effectively than carbon dioxide.
Drew Lilley is a doctoral candidate at University of California Berkeley and Lawrence Berkeley National Laboratory. He stated that the landscape of refrigerants remains a problem. “No one has succeeded in developing an alternative solution that makes things cold, works efficiently and is safe and doesn’t harm the environment.”
We believe the ionocaloric cycles has the potential for all of those goals, if it is used appropriately.”
This new ionocaloric cooling cycle is one of several types currently in development.
These techniques employ different ways to manipulate solid materials in order for them absorb heat or release it. The use of ions to cause phase shifts in solid-to liquid phases is what makes ionocaloric cool different.
The added advantage of using liquid is that it makes the material more pumpable. This allows for easier heat transfer, something which solid-state cooling often has difficulty with.
Lilley and his colleagues found that the efficiency of ionocaloric cycles could be comparable to or exceed those of most gaseous refrigerants in modern systems. The technique was also tested experimentally.
The salt was made from sodium and iodine, along with ethylene carbonate which is a common organic solvent in lithium-ion battery batteries.
Lilley stated that there is potential for refrigerants to be not only GWP (global heating potential)-zero but also GWP-negative.
The use of ethylene carbonate as a raw material could be considered carbon-negative because it is made from carbon dioxide. It could be used to capture carbon dioxide.
The ions are moved by running current, which changes the material’s melting points.
It melts and absorbs heat. When the ions are gone and it solidifies it will give heat back.
First experiment demonstrated a temperature rise of 25% using less than 1 volt. This is a higher temperature than other caloric technology.
“There are three factors we want to balance: The GWP of refrigerant and energy efficiency and the price of the equipment,” stated Dr. Ravi Prasher from the University of California at Berkeley and Lawrence Berkeley National Laboratory.
Our data look very promising in all these areas, starting with the initial try.”
We have a brand new thermodynamic framework and cycle that brings elements together from various fields. It has proven to be effective.
It’s now time to experiment to see if different materials or techniques can be used to solve engineering problems.
Published in the journal was the team’s research Science.
Drew Lilley & Ravi Prasher. 2022. The ionocaloric refrigeration cycles. Science 378 (6626): 1344-1348; doi: 10.1126/science.ade1696