Low-carbon heat pumps draw energy from external low temperature sources, like outdoor air, to heat indoor spaces and are more eco-friendly than conventional gas boilers.

But cold weather can impact their performance and with high operational costs and low heat supply temperature the growth of the product has been limited in the UK.

Researchers have now designed a more cost-effective flexible heat pump with integrated heat storage by using a small water tank and coil of copper tube.

Zhibin Yu, Professor of Thermal energy at the University of Glasgow’s James Watt School of Engineering and leader of the research, said: ‘We’re at a critical juncture in our global move towards net-zero, where we need to start scaling up our low-carbon infrastructure quickly and effectively. That urgency is being particularly keenly felt at the moment, where energy prices are rising and many households are facing rapidly escalating bills.

‘The advantages of the flexible heat pump against current heat pump products is analogous to the advantages of condensing boiler against the non-condensing boiler – both recover excess heat to greatly improve efficiency.’

The water tank recovers some excess thermal energy produced during the pump’s operation and stores an additional heat source for operation later.

This recovered heat can be reused as a temporary heat source since it has a much higher temperature than the outdoor air used by the pump, drastically reducing its power consumption.

It also allows the pump to run continuously while defrosting, making it more efficient and effective than current heat pump models which interrupt supply and use up electricity during defrosting.

Testing against current models of heat pumps has shown the new design to be 3.7% more efficient with a relatively low heat supply temperature of 35°C.

At temperatures of 65°C it’s thought the new designs could be up to 10% more efficient, as when the supply temperature increase, so does the amount of energy recovered.

Professor Yu said: ‘Our flexible heat pump solves many of the problems with the current generation of heat pumps, making them capable of delivering improved performance while using less power. The cost of a small water tank heat storage is marginal, but the power saving is significant. It can be widely applied for all kinds of the heat pump applications. We believe that this could help drive improved takeup of heat pump technology in homes across the UK.

‘Now that we have acquired a patent on the technology and proved the concept in laboratory, we’re keen to start working with manufacturers, energy suppliers and other partners to take the first steps towards putting these next-gen heat pumps into homes in Britain and around the world.’

Photo by Erik Mclean