Thermo-acoustic heat pump for residential applications


The Netherlands Organization for Applied Scientific Research (TNO) and its spinoff, Blue Heart Energy, have developed a 6 kW heat pump that works on acoustic waves and is able to produce both heat and cold air.

The thermo-acoustic technology is suitable both for residential and industrial applications,” a spokesperson from TNO told pv magazine. “However, the Blue Heart Energy solution focuses exclusively on domestic applications.”

The device measures 55 cm x 55 cm x 55 cm. It can be used in combination with rooftop solar generation.

The thermo-acoustic heat pump is especially suitable for this given its excellent modulating capability and its temperature flexibility,” the TNO spokesperson said. “When using the thermo-acoustic heat pump in combination with PV, the energy required to drive the heat pump can be taken mainly from the PV-panels, leading to fossil-free heat generation. In the future, smart controls to optimize the efficient use of PV panels and potentially sustainable heat or cold sources are expected.”

The novel heat pump can purportedly reach higher temperatures than existing heat pumps, without the need for refrigerants. It works with two pistons that oscillate at a frequency of 100 Hz in a closed pressure vessel filled with 50 bar helium. It creates an acoustic wave that is able to displace heat from a lower temperature to a higher temperature.

This process takes place in four phases: expansion, displacement, compression, and return displacement.

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“During the expansion phase, the temperature of the gas drops, and the gas in the cold heat exchanger absorbs heat,” the scientists explained. “The gas then moves through the regenerator to the warm heat exchanger. Here, the gas is compressed, the temperature rises, and the heat previously absorbed is released into the warm heat exchanger. Finally, the gas moves back, and the cycle is complete.”

They are currently testing the heat pump in an advanced climate chamber in Delft, the Netherlands.

“‘The climate chamber enables us to mimic reality very closely, so performance in the laboratory can give us a good idea of how the device will perform in people’s homes in the future,” they said. “Not only under the static conditions that relate to the standards, but also under dynamic conditions with changing temperatures which come much closer to real-life conditions. In the climate chamber, we can simulate a cold winter’s day, for example, or we can recreate all four seasons in quick succession.”

Blue Heart Energy plans to test the first devices in real houses in 2023.

“There are no moving parts other than the two oscillators, and the device has a service life of more than 15 years,” the research group said.

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