The system is likely to work with no chemical refrigerants and might use hydrocarbons.
Last month (19 December), Malta Inc., a US-based electro-thermal energy storage firm, announced it had raised $26 million (€22.7m) to commercialise a heat pump for storing grid-scale electrical energy that might use hydrocarbons as the refrigerant.
Boston, Massachusetts-based Malta Inc. is looking to commercialise a heat pump energy storage system invented by the Nobel Physics laureate Professor Robert Laughlin of Stanford University, California. Laughlin presented his system in a 2017 paper entitled ‘Pumped thermal grid storage with heat exchange’.
The heat pump energy storage system, described in Laughlin’s paper and on Malta Inc’s website, works by using electricity to drive a heat pump, which then converts the electrical energy into thermal energy by creating a temperature difference. The idea is to use the heat pump energy storage system with wind/solar energy, which is not always available.
Laughlin's paper says the working fluid should be Argon gas with heat storage provided on the high pressure side by molten salt and onthe low pressure side by a hydrocarbon liquid.
The professor does consider a feedstock of R32 called dichloromethane, but notes that this, “would increase the stress on stratospheric ozone,” or in other words deplete the ozone layer. He considers the hydrocarbon n-hexane more suitable for use.
The thermal energy stored in the molten salt and the hydrocarbon liquid would be converted back to electrical energy when needed by the grid, with the aid of a heat pump.
Malta Inc. will now work with industry partners including Sweden-based heat exchange manufacturer Alfa Laval, Hong Kong-based Concord New Energy Group and US-based Breakthrough Energy Ventures LLC (led by Microsoft founder Bill Gates), to make this technology cost-effective.
"We believe that Malta is a very interesting initiative, with great potential," said Susanne Pahlén Åklundh, president, energy division, Alfa Laval. "We will bring our unique expertise within heat transfer technology, including design and production of heat exchangers, to the invaluable knowledge and resources within the group of investors in Malta Inc."
"We are excited to partner with them to bring this innovative new approach in energy storage to the market," Åklundh said.