BOILERS, PUMPS & VALVES Barrie Welsh


HOW SUSTAINABLE IS YOUR HEAT PUMP?


Barrie Welsh, technical sales manager at Hamworthy Heating, examines the role heat pumps play in sustainability


T


he definition of sustainability in the Oxford English Dictionary is: ‘The property of being


environmentally sustainable; the degree to which a process or enterprise is able to be maintained or continued while avoiding the long-term depletion of natural resources’. When it comes to heating our buildings, this translates into more effective use of resources to maintain comfortable temperatures, combined with a reduction of emissions. Heat pumps – air source heat pumps in


particular – are being championed as the most sustainable and practical solution that we currently have available to achieve this. Heat pumps are more energy efficient than gas boilers by a factor of up three and have zero emissions from their process, whereas fossil fuel appliances are a major emitter of greenhouse gases and air pollutants.


HOW DOES A HEAT PUMP WORK? Heat pumps gather heat energy from the surrounding air which, via a heat exchanger, is transferred into the heat pump’s refrigerant and turned into vapour. The vapour is passed through a compressor and turned into high pressure, high temperature refrigerant, raising the temperature to a point that can deliver heat throughout a building’s heating system. Heat pumps don’t require high external temperatures to function; they can continue to operate with external air temperatures down to -20˚C.


IMPROVING SUSTAINABILITY CREDENTIALS There’s absolutely no doubt that heat pumps are a


more sustainable solution to heating than gas boilers. However, their sustainability credentials are impacted by a number of factors. The first of these


is the energy supply. Heat pumps utilise up to 75% of the required energy from the environment for heating output but require electricity to operate. If the electricity supply comes from a renewable source, then the heat pump really is an incredibly sustainable piece of kit. In the UK, however, the current renewables share of electricity generation was 38.6% in quarter 2 2022, according to the government’s Energy Trends report. Whilst this figure is an increase on the same quarter in 2021, it still means that the majority of heat pumps will be powered by electricity generated from fossil fuels. It would be wrong to therefore say heat pumps are a 100% sustainable solution, rather that they are low carbon ready. Refrigerant, a vital component of a heat pump,


is another important factor when it comes to determining the sustainability of individual heat pumps. There are a variety of refrigerants in use for heat transfer, but some are of questionable sustainability and raise environmental concerns. Heat pumps that use refrigerants with a low Global Warming Potential (GWP) should be a priority. Our Tyneham range of heat pumps, for example, use R32 refrigerant which has a very low GWP and a zero Ozone Depletion Potential (ODP).


www.essmag.co.uk The Tyneham range of heat pumps


The correct specification of the heat pump,


along with ensuring the entire heating system is suited to running on a heat pump, will impact its efficiency and therefore its sustainability. Heat pumps need to be correctly sized, which is based on the calculated thermal efficiency of all the areas to be heated, plus the external air temperature ranges. I say ‘correctly’, because going for an oversized heat pump – as you might do with a gas boiler, to be on the safe side – actually makes it less efficient as you have to run a higher capacity compressor using more electricity. Heat pumps operate at lower temperatures, so require radiators with larger surface areas to transfer the required heat to the room. In refurbishments, this could mean replacing radiators that are too small, which not only has an impact on sustainability in the short term, but also cost. Where possible, try to use heat pumps with correctly designed and sized underfloor heating systems as these typically have a large surface area from which to disperse heat. The last point to make in relation to


sustainability has to be directed at the air tightness of the building. The more airtight, the less heat escapes, which improves energy efficiency and sustainability. But this same advice should apply to all buildings, regardless of the heat source!


Hamworthy Heating T: 01202 662552 www.hamworthy-heating.com


ENERGY & SUSTAINABILITY SOLUTIONS - Spring 2023 27


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