In 2022, Drew Lilley and Ravi Prasher, both at UC Berkeley and Lawrence Berkeley National Laboratory, used an alternative ‘ionocaloric refrigeration’ scheme. Instead of applying a field externally, they used the electrochemical binding between the ions in a salt (in this case sodium iodide) and a solvent (ethylene carbonate). When the salt is added to the partially-frozen solvent, it begins to dissolve. To do so, however, the solvent must melt, and this requires energy. ‘[The solvent] wants to become a liquid, but it needs energy to do so, so it steals it from itself and cools down,’ explains Lilley.
They placed the system in thermal contact with a cold reservoir. Finally, they separated the salt from the solvent by electrodialysis. This raises the solvent’s melting point, causing it to partially freeze again, releasing heat. This crystalline slush is pumped back to the hot reservoir, completing the refrigeration cycle. The researchers showed a maximum temperature decrease of 28°C and an energy efficiency of 29% under practicable operating conditions – superior to other caloric refrigeration systems – and they believe there is significant room for improvement.
The US Department of Energy has given some grants to develop this technology.
Calion Technologies, Inc. — Zero-GWP Air Source Heat Pump Steam Generation Using Ionocalorics
Funding will support the project’s small-scale research and development of an air source heat pump steam generator that could seamlessly
replace natural gas boilers for industrial processes and introduce heat pump technology to new customers. Specifically, the project team will
1) design, test, and verify an ionocaloric heat pumping system and
2) apply design adjustments, test, and verify system performance.
If successful, this project would result in a device that would harness ionocaloric heat pumping technology to generate steam at very high temperatures compared with current heat pumps and accelerate the decarbonization of industrial heating, which accounts for 9% of U.S. greenhouse gas
emissions.
Calion Technologies (Danville, CA) will develop a heat pump steam generator that could seamlessly replace natural gas boilers for industrial processes and introduce heat pumps to a new swath of customers. Calion Technologies’ approach is designed to generate steam at temperatures not possible with current heat pump technologies to accelerate the decarbonization of industrial heating, which accounts for 9% of U.S. greenhouse gas emissions annually. (Award amount: $500,000)
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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In my opinion there are two critical point. One is electrodialysis, the other is pumping the crystalline slush. Both can be source of high maintenance need.
The solvent and salt are inexpensive; the cost of the equipment and its maintenance is another story altogether. I am sure it needs to prove itself in a large-scale demonstration unit first, and then engineers can work to bring down costs.
It would be interesting to know if this could replace home AC systems and industrial evaporative cooling (ie cooling towers)
They’re targeting an unserved niche first. If that works, maybe they can eventually grow and compete with mature HVAC technology.