The art of technology fusion
The heat is on for the UK to increase its generation of energy from renewable sources if we are to meet our target of 15 per cent by 2020, says Mike Hefford, Head of Renewables at Remeha Commercial. For the building services, the challenge is to deliver ever-lower carbon footprints and ever-higher system efficiencies for new and existing buildings.
With space and water heating accounting for as much as 60 per cent of the total energy use of a building and 40 per cent of carbon emissions, renewable technologies such as heat pumps are increasingly specified as the prime source of ‘green’ energy for heating and hot water provision in new buildings. They are also playing a greater role in refurbishment projects, where heat pumps operating alongside replacement condensing boilers can maximise the building’s carbon and energy savings potential.
Amongst the range of heat pump options, gas absorption heat pumps (GAHPs) are growing in popularity as a high efficiency, low-carbon, low-NOx solution that can significantly improve the environmental ratings of a building and reduce operating costs. Rather than the ‘new heat pump on the block’, this is in fact a well-established technology that has been available for some time.
Gas absorption heat pumps use gas-fired heat pump technology and a low-NOx thermodynamic condensing heat generator containing an ammonia water working fluid to draw energy from the air. By combining this energy with the gas input, they are able to increase the thermal output to offer exceptionally high realistic seasonal efficiencies of between 120 and 130 per cent with reliable operation even at low sub-zero outside temperatures and continuous heating even in thaw phase.
GAHP technology offers a range of environmental and cost-saving benefits to building operators. Using gas rather than electricity to fire the heat pump reduces operating costs as gas is typically a third of the price of electricity. It also brings a strong environmental credential as gas has a lower carbon-emission factor than grid-supplied electricity. GAHPs use ammonia, a naturally forming chemical, as the refrigerant offering no harmful effects to the ozone; with a resulting zero ozone depletion potential and zero global warming potential, using a GAHP provides buildings with a credit in BREEAM assessment ratings whilst the absence of CFC (used by air-to-water pumps) meets the Energy and Atmosphere requirement for the LEED’s Fundamental Refrigerant Management.
GAHPs offer a flexible, versatile heating alternative as they can be used as a single unit or cascade, or, as is often the case, operated in tandem with gas condensing boilers. While GAHPs are relatively easy to install, good system design is essential to achieve the headline high efficiencies and savings. Despite the increase in use of renewable technologies in bivalent heating systems as a means of reducing energy and carbon, according to recent research many new and existing buildings consume between 1.5 to 2.5 times more energy than predicted whilst heat consumption can be as much as 1.5 to 6 times higher than anticipated.
To avoid an energy performance gap with GAHP technology, there are five key steps to follow: size right, design right, install right, control right and commission right.
Size right – carry out an accurate heat loss calculation of the building. Basing the heat loss calculation on the existing equipment will result in over-specification and failure to achieve the maximum efficiencies. The GAHP should be sized between 30 to 50 per cent of the total heat requirement for lower energy usage and significant reductions in operating costs and carbon emissions.
Design right – allow the system to operate in a ‘renewable’ way at lower temperatures and design accordingly. On new build, GAHPs work very well with underfloor heating due to the low water temperature. However on retrofit, radiators will need to be recalculated and resized to lower temperatures in order to deliver the higher efficiencies. Including buffer vessels for hot water pre-heat also increases the efficiency of the system.
Install right – as with all bivalent systems, failure to install correctly can lead to the two technologies competing against each other. The low-carbon technology will fail to perform as expected – and, worst case scenario, may not even operate at all – which will result in higher than expected operating costs. It is advisable to use the same supplier whose knowledge and expertise of the two technologies will support smarter system design and installation.
Control right – controls are an integral part of good system design and central to effective performance. Controls such as weather compensation ensure maximum operation of the GAHP and condensing technologies. Controls can also unite the two technologies, optimising their combined operation and savings potential. In existing buildings, specially-configured controls that integrate the bivalent system into the existing building management system are the answer to achieving high performance.
Commission right – this last step in the overall design concept, hydraulic, combustion and controls commissioning, is crucial to ensure high performance, reliability and maximum efficiency.
The energy and carbon saving potential of GAHP technology is clear. To avoid any performance gap and achieve maximum efficiencies, we at Remeha have responded with a bespoke bivalent system combining our GAHP range and high efficiency condensing technology with a fully-integrated, scalable building control system that can be specially tailored to meet the unique needs of a building to maximise energy and carbon savings. Fusion Hybrid can reliably achieve outstanding seasonal efficiencies of between 120 and 130 per cent with carbon reductions of up to 40 per cent compared to traditional gas equipment. The specially-configured building management control system can be easily integrated into existing building management systems, making it perfectly suited for retrofit purposes as well as new build. The control system also has an integrated touchscreen control panel, the Remeha Touch, for easy and accurate operation and monitoring.
If we are to meet both our steep carbon reduction target of 80 per cent by 2050 and our 2020 renewables target, we must raise heating efficiencies in our new and old buildings with low-carbon technologies. With the arrival of smarter bespoke bivalent systems that bridge the energy performance gap, the future looks bright for gas absorption heat pumps.
For more information, email us at email@example.com or call us on 0118 978 3434.
This article originally appeared in EIBI magazine, June 2014
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