The HEAT4U project has designed a heat pump system for the residential market. This gas-fired retrofit solution was designed to produce air-sourced heat quietly and cost-effectively, even at temperatures well below zero — and field tests indicate that it is delivering on its promise.

The partners estimate that their new system will use 35% less energy on average than a condensing boiler, enabling households to reduce their energy consumption and heating bills significantly.

Like other heat pumps, the HEAT4U unit taps into a source of renewable energy. In contrast to some, says project coordinator Luigi Tischer of lead partner ROBUR spa, it is easy to install, requiring no changes to the building itself. It therefore brings energy savings in existing homes within easier reach and could help the EU meet its climate and energy goals.

And the cost should be competitive, says Tischer, stressing the importance of comparing like with like. In terms of renewable heating for the residential market, he explains, the leading technologies at the moment include condensing boilers combined with solar or electrical heat pumps.

Home heating innovation

While new constructions are often highly energy efficient, they only constitute a very small part of the building stock. On the whole, Europe’s buildings tend to be venerable, with 35% dating back more than half a century, and renewal rates are slow. Solutions to make this type of building more energy efficient could therefore significantly reduce consumption across the EU.

Gas-fired absorption heat pump (GAHP) technology holds the key, according to the HEAT4U consortium. Heat pumps are placed outside the home and essentially work like fridges, only in reverse: instead of extracting heat from a closed space (e.g. the inside of the refrigerator) and dissipating it elsewhere, they extract heat from the environment to pipe it into a closed space (e.g. a house).

GAHPs are one of several types of heat pump that extract heat from ambient air. They are powered by natural gas rather than electricity, which is still predominantly generated from fossil fuels, Tischer notes. GAHP technology is often used for larger buildings, such as hotels and schools. The objective of HEAT4U was to adapt it for single-family detached homes.

Doing so involved a major rethink. Current GAHP systems usually involve several heat pump units, Tischer explains, and adaptations to changing demand and weather are made by adjusting the number of units that are actually running.

Individual households would, of course, just use a single heat pump, and so HEAT4U had to design a standalone unit that can cope with varying conditions. Field tests in five sites across Europe indicate that this objective has been met: the new unit works efficiently even at temperatures down to –20 °C and does not require a back-up boiler.

Sourcing heat from cold air may seem counter-intuitive, but the approach builds on the fact that it could actually be colder: the appliances cool the outside air even more, and the heating process exploits this difference in temperature.

No-fuss retrofit

Keeping the installation simple was another priority. Many heat pump systems involve work in or around the building — such as switching from radiators to under-floor heating, or uprooting the lawn to bury pipes. 

In contrast, the HEAT4U unit hooks up to the pipes of the existing central heating, says Tischer. It runs on gas, and electricity is needed for the display. Other than drilling through the building’s outer wall for a few small connections, no changes to the construction are needed. “It is also by far the quietest heat pump technology on the market,” Tischer reports.

HEAT4U ended in October 2014. The new GAHP is now being prepared for commercialisation, which notably involves completing the industrial design of what is, currently, a functional prototype. Tischer expects the finished product to be available to customers across the EU within a year or so. “With our units, the European family can start saving 35% of consumption immediately, without any particular building work,” he concludes.

Below: HEAT4U project: picture of the prototype unit

© Robur