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Building In Sustainability With Heat Pumps

Adveco explores how commercial organisations should approach building in sustainability with heat pumps… 

The implementation of low-carbon water heating is one of the fastest, low-impact means of introducing sustainability into an existing commercial building. A considered, well-designed replacement system will reduce carbon emissions by at least half compared to equivalent-sized gas-fired water heating and likely by much more as the electricity grid continues to become greener. Efficient, robust and relatively low maintenance, the latest generation of renewables represents a solid investment in the future of a building and the comfort it supplies to those visiting or working there.

The current renewable technology of choice is the heat pump, of which the easiest and lowest cost to implement is the air source heat pump (ASHP). The technology uses a reverse refrigerating circuit to extract heat from the air, even when ambient temperatures drop during the winter months. The efficiency of a heat pump is measured by its COP (coefficient of performance) which defines how much energy it uses compared to the heat energy it generates. The higher the number the better. The COP will fluctuate with external temperatures so it’s always best to use the seasonal COP which averages the efficiency across the year. As the ambient temperatures drop the heat pump will demand more electrical energy to run the compressor to maintain necessary operating temperatures. This is where heat pumps have a weakness because they were designed to operate at low working flow temperatures (35°) to supply radiators and underfloor heating, not the more stringent heating requirements of water (+60°C) required to prevent legionella.

This additional electrical energy required to raise temperatures comes from the grid and remains far more expensive than gas. In the past three years, electricity prices have fluctuated and climbed from three to nearly five times the cost of gas. This means building in sustainability with low-carbon technology can deliver considerable increases in operational costs if not approached with care and consideration.

Heat pumps have a valid role to play, but for water heating, they need to be used as part of a wider process to ensure cost-effective, efficient operation. This hybrid approach employs the ASHP as a source for preheating cold water flowing into the system to 45°C. This is more than achievable for most heat pumps, maximising the efficiency and reducing the energy required to run the unit. This warmed water is then fed into a cylinder where a second heating source tops up the water temperature to a safe 65°C for use throughout the building. This top-up can come in the form of a gas water heater, gaining very low operational costs, but a less meaningful reduction in carbon emission, typically around 30%. To maximise emission reduction, an electric boiler is preferred, although operational costs will climb, smart controls will optimise the two heat sources to minimise energy demands and provide control over operational costs.

With a hybrid system, there will be an increased plant, with a heat pump, boiler and larger cylinder needed to account for slower system reheat after peak demand. Compared to traditional gas water heating this can be a concern when retrofitting as space holds value.  The latest generation of renewables, from monobloc ASHPs to electric boilers, are increasingly more compact, while smart controls maximise storage optimising cylinder size.

For smaller to mid-sized organisations with basin-led hot water demands Adveco has redefined this approach with its award-winning FUSION electric water heating system. Conceived as a direct replacement for old gas systems, FUSION mounts an electric boiler onto a cylinder with prebuilt pipework. The controls and sealed multiple immersions within the boiler ensure resilience and means almost completely nullify damaging limescale in hard water areas. For soft water areas, the stainless steel cylinder provides anti-corrosion protection. The optional addition of an electric immersion also provides redundancy with short-term backup to guarantee service should repair be required. FUSION excels with a twin coil cylinder variant that enables a monobloc heat pump to be connected to preheat the water. With the latest options supporting storage capacities of up to 750 litres, there is a variant for most small to mid-sized organisations which is quick and easy to install for minimal operational disturbance.

For larger buildings, a more bespoke system is likely to be required, although the basic premise remains the same, using ASHP preheat and a secondary energy source, preferably electric. It may also be possible to integrate solar thermal technology as a mid-heat to further cut energy demands, by as much as 30% annually to further offset operational costs and reduce emissions.

When building in sustainability through water heating every building, from structure to usage, is different. So before embarking on any major renovation to a water system, it’s always sensible to gather data on current system use and especially the peak demand periods. That is easily achieved through non-invasive water metering which takes approximately a month to collate necessary data to accurately model the building’s requirements. From this data, a thermotical system design can be produced. One that delivers on the building’s demands whilst optimising the equipment necessary which translates usually into lower up-front investment and a better grasp on future operational costs. That is truly valuable as it enables more accurate planning and budgeting before making any initial move towards a more sustainable operation.