French startup Equium has developed a heat pump core that works on acoustic waves and produces hot and cold air. Equium manufactures the core and works with another company that integrates it into heat pump systems. The units are scalable from 1 kW to 3 kW and are designed for residential applications.
The novel heat pump can purportedly reach higher temperatures than existing heat pumps, without the need for refrigerants. It works with a high-fidelity (Hi-Fi) speaker powered by electricity that creates an acoustic wave in a closed-pressure vessel filled with helium at a pressure of 30 bars. The acoustic wave causes the gas to compress or expand, displacing heat from a lower temperature to a higher temperature, or vice versa. The heat pump core is filled with water, which absorbs or releases that heat.
“The acoustic wave does the work of compression and expansion of the gas that produces heat or cold, respectively,” Philippe Loyer, a product manager at Equium, told pv magazine.
Loyer said the heat pump can generate domestic water at up to 80 C. He claims that one of the key benefits of the acoustic heat pump, in comparison with traditional units using refrigerants, is its ability to reach very high or low temperatures.
“Traditional heat pumps use refrigerants with a temperature phase. They a have temperature limit, which is the temperature of the changing phase from liquid to gas of the refrigerant,” said Loyer. “In our core, the helium stays in gas form. Because helium remains a gas until -200 C, we can achieve higher temperatures inside our heat pump core.”
The heat pump purportedly works with all external heat sources, including air sources from -15 C to 50 C. Given that its core is filled with water, it works best as a water-source and geothermal heat pump. To be used as an air-source heat pump, the unit can be equipped with a fan that transfers the heat from the air to the water, according to Loyer.
The heat pump has a coefficient of performance (COP) of three to four, which means that it produces 3 kW to 4 kW of heat for each kilowatt of power it consumes. Equium is targeting 8 kW to 10 kW of thermal power for its heat pump core, Loyer said. It has a 30-year lifetime, with an easy installation process. The acoustic heat pump also offers better modulation than traditional units.
“We have the same efficiency as traditional heat pumps, but we have better modulation thanks to acoustic transfer,” said Loyer.
Traditional fixed-output units cycle between on and off multiple times a day, switching between zero and maximum capacity to achieve the right temperature balance. But the new heat pump modulates its output to continuously provide the desired temperature.
“The output regulation of a classical heat pump is very energy consuming. On our acoustic system, the regulation is very easy,” Loyer explained. “If you want less power, you can just decrease the volume of the Hi-Fi speaker.”
Equium claims that the heat pump system is completely silent, despite the use of a speaker to generate the acoustic wave. The level of noise is reportedly lower than 30 dB – the equivalent of a whisper.
“The sound our system produces stays confined inside the core, so you cannot hear it from outside,” said Loyer.
Equium is now conducting field tests for its thermos-acoustic heat pump. It expects to launch it at the end of 2023.
*This article was amended on 03/01/2023 to reflect that the helium is at a pressure of 30 bars and that it remains a gas until -200 C, not -300 C as previously reported.
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