Heat pumps proven to deliver

UK: Test by scientists at one of the leading low carbon research units have proven that heat pumps can deliver a home’s daily hot water needs in the toughest climates.

Professors at The University of Salford’s Energy House 2.0 have conducted the first research on whether the low carbon technology can deliver hot water that meets British Standards.

The research was carried out on a concept home built by housebuilder Barratt Redrow and construction company Saint-Gobain UK & Ireland, known as eHome2, at the Energy House 2.0.

Energy House 2.0 is a specially built climate chamber that recreates temperatures ranging from -20˚C to +40˚C, as well as simulating wind, rain, snow and solar radiation. In practice, the chamber can simulate the weather conditions in 95% of the world’s current climates, as well as the climates predicted in the future.

With the UK preparing to go gas-free, researchers have spent the past 16 months testing different systems to see which ones will run a consumers’ home in the most efficient way at the lowest cost.

Professor Richard Fitton at the University of Salford said: “Following our detailed study on heat pump performance for space heating tasks, hot water provision was always the missing piece of the puzzle, it was reassuring to see that under typical winter conditions that delivered efficiency was over 180%, and hot water demands were being met.”

Oliver Novakovic, head of technical and innovation at Barratt Redrow, said that it was understandable that consumers had concerns around whether heat pumps could meet their daily requirements for heating and hot water. “After all, nobody wants a cold bath,” he said.

“These rigorous hot water tests – along with our earlier tests on heating – demonstrate that heat pumps are an effective and cost-efficient alternative to gas boilers.”

There are two air-source heat pumps installed in eHome2: a compact Curv 195 litre stand-alone cylinder located internally in a cupboard and a 236 litre storage cylinder attached to a Vaillant system.

The Vaillant system, with its Unistor cylinder and aroTHERM air-source heat pump, came out on top as the most stable and reliable hot water for a house.

The heat pump is said to have maintained consistent hot water temperatures within the target range, from 25°C to 55°C, across varying environmental temperatures (5°C, 7°C and 14°C).

The bath tap, which has the highest demand, maintained a steady flow rate for both hot water and mixed water, demonstrating the system’s ability to handle the peak demands of the home without a noticeable drop in performance.

Researchers say that the energy consumption data reveals that the heat pump’s electricity usage decreased as the chamber temperature increased. At 5°C, the heat pump consumed an average of 8.58kWh/day, whereas at 14°C, the consumption dropped to 6.62kWh/day.

While its performance diminishes in colder environments, the Unistor cylinder’s buffer tank played a crucial role in reducing short cycling, enhancing system reliability and efficiency by maintaining a consistent water temperature in the cylinder.

Curv System

The Curv system, a compact 195-litre stand-alone cylinder with a smaller buffer tank, sits in a cupboard within the eHome2 at Energy House 2.0, providing a solution for terraced homes and apartments. It only provides hot water, not heating.

The energy-efficient heat pump solution held similar temperatures as the Vaillant system, although it had minor fluctuations at lower temperatures due to the smaller buffer tank.

The rate of water flow was said to be consistent, meeting required volumes for both bath and kitchen taps for the average family. Its energy consumption was lower than the Vaillant system, dropping from 5.61kWh/day at 5°C to 4.15kWh/day at 14°C. 

“We have put the two heat pumps under large daily hot water use based on a British Standard to cover the worst-case scenario,” said University of Salford professor Lubo Jankovic, who led the work.

“This included water draw-offs for various uses, from dish washing to household cleaning, baths, showers and other daily demand. It was encouraging to see that both heat pumps provided sufficient hot water volume and temperature throughout each day of testing.”

Professor Richard Fitton revealed that they were now looking to advance the work to examine dynamic pricing, solar PV and battery storage later this year.”