11 April 2023
As the UK Government looks to reduce emissions to net zero by 2050, the heating of virtually all buildings will need to be decarbonised. The phase out of fossil fuel boilers will help to meet these carbon reduction targets, and heat pumps will become an increasingly popular renewable heating solution.
Heat pumps are often said to work like a fridge in reverse. They transfer heat from the outside air (Air Source), the ground (Ground Source) or from water (Water Source) into a building and then increase the temperature until it is suitable for use within a heating system. Air source heat pumps (ASHP) tend to have the largest market share and are the cheapest and easiest to install, however ground source heat pumps (GSHP) are considered more efficient.
GSHPs have a longer lifespan and provide a constant course of heat across different seasons. They require pipes to be laid into the ground and therefore tend to be a bit more expensive to install. They are well suited to new builds, in particular apartments and social housing. It is estimated that the UK still has 23 million gas boilers and with the ban from 2035 on installing any new gas boiler, the government has introduced its Boiler Upgrade Scheme (BUS), aimed at incentivising and increasing the deployment of low carbon heating technologies. Grants are available in the region of £5,000 for an ASHP or biomass boiler, and £6,000 for a GSHP.
Refrigerants – their role and improved profiles
An essential component of any heat pump is the refrigerant, required for the vapour compression cycle which over many years has been mainly R-410A and R-134a. With the focus on sustainability, the global warming potential (GWP) of R-410A of 2088 means that it is unsuitable for new equipment.
Equipment manufacturers are now moving to using lower GWP refrigerants such as R 32 (GWP 675) and R-454B (GWP 466) instead. Some mono-block hermetic systems with low charge sizes use R-290 or R-134a. Some heat pumps, mainly ground source, that have historically used R-407C, are now moving to R-454C or R-455A, both with a GWP of 148. Some of the lower GWP refrigerants have a degree of flammability but as long as the installer is trained in the safety and installation of such refrigerants, their use should be embraced. Long term, R-1234yf (GWP 4) or R-1234ze (GWP 7) will be used instead of R-134a, however R-513A (GWP 631) is a short-term easy switch. In some specialist heat pump applications, R-744, R-1233zd, Propane and Ammonia are being used as a refrigerant.
Using a heat transfer fluid within the heat pump system
The air source, ground source and water source heat pump systems all use a heat transfer fluid, whether it be a glycol solution or water, and heat it in the heat exchanger, using the compressed refrigerant, raising its temperature so that it is suitable for the system.
In the case of a ground source heat pump system for example, the heat transfer fluid or glycol is circulated through a set of underground pipes, also known as a ground loop. A closed-loop GSHP system circulates heat transfer fluid through a closed loop set of underground pipes, whereas an open-loop system uses ground water for the heat exchange process and extracts it after use. Open loops tend to be simpler and cheaper to install however may require more maintenance.
As the ground has a relatively constant temperature through the year, it is considered an excellent source of heat. The Ground Source Heat Pump Association report the natural temperature of undisturbed ground in Britain to be around 10°C at a depth below six metres, although temperature will depend on location and depth. So, to some extent, the HTF has a head start on its heating.
All heat pumps require electricity to operate but can provide very energy efficient heat with high coefficient of performance (COP) values of up to 5, whereas the best condensing boilers can only deliver a COP of 0.9.
Bio-sourced HTF alternatives
Traditionally, heat transfer fluids, used in the food, building and energy industries have been based on mono propylene glycol (MPG) a product from the petrochemical industry. With this tighter focus on carbon reduction targets, and increasing environmental commitments, it’s time to consider the available alternatives to conventional heat transfer products.
One such product being Greenway® Neo N; a plant-based heat transfer fluid which has been formulated with bio-sourced 1,3 propanediol. Plants are harvested, fermented and refi ned to produce this biotechnology. By using a product such as Greenway® Neo N Heat Pump which is biodegradable, there is the reduced risk of soil pollution in the event of a leak, which is particularly important in a heat pump system, and excellent corrosion protection. It’s bacteriostatic formula, prevents the development of bacteria, moulds, fungus and algae which can affect the flow and heat exchange, so it helps to reduce clogging and efficiency can be maintained by a good fl ow rate.
Notably, the production process of bio-sourced 1,3 propanediol consumes less energy and emits less CO2 during manufacture than MPG or synthetic chemicals, helping to reduce environmental footprint.
Climalife prides its expertise in eco-efficient solutions to service the industry and works with many heat pump installers, supporting them with refrigerants and heat transfer fluids, suited to each individual project.
One such installer being Griffiths Air Conditioning and Electrical Contractors, an MCS accredited installer of Air and Ground source heat pump systems. Griffiths AC installed a Daikin 8KW Altherma Monobloc air source heat pump system in the 40m² orangery of a local farmland owner in Northamptonshire, using Greenway® Neo throughout as the HTF. The heat pump is linked directly to a Polypipe ‘In-Screed’ system comprising of a 4-port manifold supplying 18mm underfloor heating pipe secured with castellated floor trays. The pipe was laid at 100mm spacing in a spiral pattern ensuring a comfortable even floor temperature and as low as possible HTF flow temperature whilst still satisfying the buildings heat loss demand. In this case the air off temperatures varied between 35°C and 45°C, and so by running an air source heat pump at the lowest temperature possible, the maximum operating efficiency (SPF) was ensured. The building owner was keen to promote the usage of renewable energy and products, which fits in with the local focus; one of the largest onshore Wind and Solar Farms in the country being situated nearby. An R32 Daikin heat pump AC unit was also installed for the orangery by Griffiths.
Griffiths AC continue to use Greenway® Neo as their standard heat transfer fluid for all their installations, including Solar Thermal systems, Ground and Air source heat Pumps, Monoblock systems and also for underfloor heating. Their technical manager said ‘The choice to use Greenway® Neo was easy, we only need one product, and we chose the most environmentally acceptable product on the market, which fits our company policy to use renewable products wherever possible’.
Time for change
It's been interesting to see heat pump systems beginning to be advertised on mainstream television, which highlights how heat pumps will soon become our everyday norm. So, with sustainability at the heart of the shift, it’s important to be aware of the energy efficient refrigerants that are available and the alternative bio-sourced htf alternative(s) to MPG and MEG. If you would like to find out more about these fluids, consider speaking to Climalife or contact your usual supplier.
Written by Mel Summers, Marketing Manager at Climalife