Ionocaloric cooling takes advantage of how energy, or heat, is stored or released when a material changes phase, such as changing from solid ice to liquid water. The ionocaloric cycle causes this phase and temperature change through the flow of ions that come from a salt.
The team at the US Department of Energy’s Lawrence Berkeley National Laboratory hopes that this method could one day provide efficient heating and cooling, which accounts for more than half of the energy used in homes, and help phase out current ‘vapour compression’ systems which use gases with high global warming potential (GWP) as refrigerants.
Ionocaloric refrigeration would eliminate the risk of such gases escaping into the atmosphere by replacing them with solid and liquid components, researchers said.
“The landscape of refrigerants is an unsolved problem. No one has successfully developed an alternative solution that makes stuff cold, works efficiently, is safe, and doesn’t hurt the environment,” said Drew Lilley, a graduate research assistant at Berkeley Lab and PhD candidate at UC Berkeley who led the study.
“We think the ionocaloric cycle has the potential to meet all those goals if realised appropriately.”
Finding a solution that replaces current refrigerants is essential for countries to meet climate change goals, such as those in the Kigali Amendment (accepted by 145 parties including the US, in October 2022).
MORE IN ENERGY AND ENVIRONMENT
The agreement commits signatories to reduce production and consumption of hydrofluorocarbons (HFCs) by at least 80 per cent over the next 25 years. HFCs are powerful greenhouse gases commonly found in refrigerators and air conditioning systems, and can trap heat thousands of times as effectively as carbon dioxide.
The new ionocaloric cycle joins several other kinds of ‘caloric’ cooling in development. Those techniques use different methods – including magnetism, pressure, stretching and electric fields – to manipulate solid materials so that they absorb or release heat.
Ionocaloric cooling differs by using ions to drive solid-to-liquid phase changes. Using a liquid has the benefit of making the material pumpable, making it easier to get heat in or out of the system – something solid-state cooling has struggled with, researchers explained.
Lilley and corresponding author Ravi Prasher, a research affiliate in Berkeley Lab’s Energy Technologies Area and adjunct professor in mechanical engineering at UC Berkeley, laid out the theory underlying the ionocaloric cycle. They calculated that it has the potential to compete with, or even exceed. the efficiency of gaseous refrigerants currently found in most systems.
They also demonstrated the technique experimentally. Lilley used a salt made with iodine and sodium, alongside ethylene carbonate, a common organic solvent used in lithium-ion batteries.
“There’s potential to have refrigerants that are not just GWP-zero, but GWP-negative,” Lilley said in a statement. “Using a material like ethylene carbonate could actually be carbon-negative, because you produce it by using carbon dioxide as an input. This could give us a place to use CO2 from carbon capture.”
Running current through the system moves the ions, changing the material’s melting point. When it melts, the material absorbs heat from the surroundings, and when the ions are removed and the material solidifies, it gives heat back. The first experiment showed a temperature change of 25°C using less than one volt, a greater temperature lift than demonstrated by other caloric technologies.
Prasher said that data looks promising on the GWP, energy efficiency and cost of the equipment – three aspects the team is trying to balance.
While caloric methods are often discussed in terms of their cooling power, the cycles can also be harnessed for applications such as water heating or industrial heating. The ionocaloric team is continuing work on prototypes to determine how the technique might scale to support large amounts of cooling, improve the amount of temperature change the system can support, and improve the efficiency.
Lilley and Prasher have received a provisional patent for the ionocaloric refrigeration cycle. Their work is published in Science and was supported by the DOE’s Energy Efficiency and Renewable Energy Building Technologies Programme.
First seven members join NG’s Great Grid Partnership
Agreed. It is all pretentious posturing and trite branding with no meaning or gravitas. Prepare to be disappointed by all of these greats/grates.