Developed by Chinese researchers, the system is designed to reach a heating capacity of 5.7 kW and an overall coefficient of performance of 1.40 at nominal conditions. It is made with an engine unit, a heat pump unit, and a gas resonator unit in a loop.

Schematic of the heat-driven thermoacoustic heat pump

Image: Chinese Academy of Science, Energy Proceedings, Creative Commons License CC BY 4.0

Researchers led by the Chinese Academy of Sciences have designed a novel thermoacoustic heat pump system that they claim is able to use medium/low-grade heat for heating supply in domestic applications.

“The system consists of one simple thermoacoustic energy-conversion unit with a direct-coupling configuration, which greatly reduces the system complexity compared to the traditional multi-stage thermoacoustic systems,” they explained, adding that the device has no moving parts.

The system is designed to reach a heating capacity of 5.7 kW and an overall coefficient of performance (COP) of 1.40 at nominal conditions. It is made with an engine unit, a heat pump unit, and a gas resonator unit in a loop.

The engine consists of a heat-sink heat exchanger, a regenerator, a high-temperature heat exchanger, and a thermal buffer tube. The cooler unit is made with a heat-sink heat exchanger, a regenerator, a heat-source heat exchanger, and a thermal buffer tube.

The system is initially excited by the thermoacoustic oscillation and it uses the amplified acoustic power to drive the heat pump unit to pump heat from the heat source to the heat sink.

“The heat-source temperature varies between 260 K and 310 K, reflecting the variations in system performance over the seasons,” the scientists emphasized. “The heat-sink temperature varies between 298 K and 363 K, covering the range of applications from low-temperature underfloor space heating to the provision of domestic hot water.”

According to the research team, the heat pump is capable of offering stable COP values varying between 1.1 and 1.5 over most of the temperature range. “Especially in the typical domestic heating supply temperature range of 50-70 C, the proposed heat pump system can pump several kilowatts (1-11 kW) of heat from a heat source of 260 K to 310 K with remarkable efficiency,” it also noted.

The research team comprises academics from the Karlsruhe Institute of Technology in Germany and the Tsinghua University and Southeast University, which are both located in China. Its findings were published in the paper “A heat-driven thermoacoustic heat pump with a single direct-coupling configuration capable of utilizing medium/low-grade heat for domestic applications,” published in Energy Proceedings.