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A top-class solution to low-carbon heat

Mike Hefford looks at the growing interest in gas absorption heat pumps for low-cost, low-carbon heating and hot water in schools

Posted by Stephanie Broad | May 13, 2016 | HVAC & lighting

For schools juggling tight budgets with challenging environmental targets, heating offers huge scope for energy and carbon savings as, together with hot water, it accounts for over half the energy consumed in school buildings. For this reason, renewable technologies are increasingly specified as the prime source of ‘green’ energy in new buildings and in conjunction with condensing boilers on refurbishment projects. One low-carbon alternative that is growing in popularity due to its ability to significantly improve the environmental ratings of a building and reduce its operating costs is gas absorption heat pumps (GAHPs).


GAHPs are a flexible solution that can be specified as a single unit, in cascade arrangement or in a hybrid system alongside condensing boilers. GAHPs are equally suited to new build and refurbishment projects but particularly effective when used in conjunction with low temperature radiators and underfloor heating. This makes them ideally suited for use in schools with their high demand for heating and hot water and requirement for the removal of any scald hazard from exposed pipework.

So how do they work?

GAHPs are externally sited and operate by capturing energy from the surrounding air, which converts to higher temperatures with the aid of an ammonia water refrigeration cycle. By combining this renewable energy with a gas-driven condensing heat generator, GAHPs can increase the heat output to offer exceptionally high real-world gas utilisation efficiencies (GUE) of between 120 and 130% – rising as high as 160% under ideal conditions. The high performance of GAHPs means that they deliver reliable operation even at low outside temperatures and continuous heating even in defrost operation.

Energy and carbon savings

A key advantage of GAHPs is their use of gas rather than electricity for operation. This reduces operating costs as natural gas is typically around a third the price of electricity. It is also more energy efficient as, by using gas at the point of use rather than grid-supplied electricity, GAHPs can provide 98 per cent of usable heat energy – which in turn significantly reduces the school’s carbon footprint. And as they require only an extremely low electrical running current to operate, they can be easily retrofitted without the need to increase the electrical incoming supply.

Remeha Fusion GAHPs at Hardwick and Cambourne Community Primary School 

Improved environmental rating

GAHPs also score high in terms of environmental credentials, enhancing both the rating of the building and the school’s reputation for sustainability. Five BREEAM points are awarded for using this technology. Using ammonia, a naturally forming chemical, as the refrigerant brings two credits for zero ozone depletion potential and zero global warming potential and a third for the absence of Hydrofluorocarbons (HFC) refrigerants. Further points come from its status as a low carbon technology and its ability to achieve Class 5 NOx levels by using a condensing heat generator with a premixed modulating gas burner. The improved operational performance and reduced carbon footprint of the building are visibly reflected in the school’s Display Energy Certificate (DEC).

Smart design for maximum performance

As with all renewable technologies, good system design is essential in order to maximise carbon and energy savings. Look for suppliers with a thorough understanding of the technology who can advise on best-practice system design and control. Avoid a performance gap between predicted and actual building energy performance by requesting data that will assist accurate calculation of the achievable GUE of the GAHPs. With well-integrated GAHP technology, schools have the ability to deliver on their environmental commitments while pumping up operational savings that can be used for the benefit of their students. It’s a proven route to sustainable success.

Mike Hefford is Head of Low Carbon Technologies at Remeha Commercial


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