AIR CONDITIONING
circuit incorporating an electrically driven compressor. It can then be delivered at a suitable temperature for heating the inside of a building. For cooling, this process is simply reversed. So, low-temperature heat is collected from inside the building, upgraded, and then rejected to the atmosphere, water or ground. But the power and versatility of heat pumps can be increased still further by combing them with other technologies.
Traditionally, ‘hybrid’ heat pumps composed
of standard heat pumps incorporating other heating elements such as boilers. These are increasingly prevalent driven by the pressing environmental imperative to reduce global greenhouse emissions.
A couple of years ago, as part of its wider research into heat decarbonisation, the UK government commissioned a study to advance the understanding of the potential role of hybrid heat pump systems in the UK’s long-term decarbonisation of domestic heat The study, which examined mixed heating systems incorporating heat pumps and gas boilers in houses, revealed that, for some building types, hybrid heat pumps can offer large lifetime cost savings over individual heat pumps.
Noting that the share of heat met by a heat pump component of a hybrid system can be between 30% and 96%, it concludes: “Hybrid heat pumps currently offer upfront cost savings of £450 to £2,800 compared to a standalone heat pump, for a typical semi-detached house.” Overall, the analysis suggests that for typical existing buildings, hybrid devices offer substantially more cost-effective heat decarbonisation option than standard heat pumps.
But the latest hybrid heat pump technology refines the technology still further, often incorporating extra features such as heat recovery.
Our own award-winning Rhoss EXP/HT four- pipe heating and cooling system, for example, is a hybrid system that can produce independent cooling and heating, just like a traditional chiller or heat pump, but the innovative part of the system is the use of a third heat exchanger within the machine so that, when cooling, the heating can be essentially free due to heat recovery, or vice versa.
The system comprises two parts. A hybrid four-pipe air or water source heat pump produces simultaneous or independent cooling
and heating – using heat recovery wherever possible for ‘free’ heating or cooling– with typical chilled water temperatures of 6/12°C and hot water temperatures, typically up to 55°C. A high temperature water source heat pump
is then used, with the recovered heat being the source to raise the temperature of the domestic hot water loop to up to 78°C with a CoP of up to 6.0.
Since it is an integrated heat pump solution, there is no need for a separate boiler which results in a significant plant space saving and lower equivalent CO2
emissions in operation. So,
consultants are shifting away from chillers and boilers towards all-electric combined cooling and heating solutions, with demand being driven by legislation and government targets to cut carbon emissions by 80% by 2050. The Rhoss EXP/HT typically hs operating energy cost savings of around 22% and 28% reduction in carbon emissions compared to a traditional chiller and boiler four-pipe solution (without water source heat pump). Any additional cost for the hybrid heat
solution over a chiller and boiler system is typically recovered within just over two years from the energy cost saving.
www.acr-news.com
September 2020 31
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