07 October 2024
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Pete Mills, Commercial Technical Operations Manager at Bosch Commercial & Industrial gives his take on heat pumps and how taking a hybrid approach can support their continued pick-up in UK non-domestic buildings.
Retrofitting non-domestic buildings with heat pumps presents both challenges and opportunities for contractors aiming to support their clients’ ambitions to decarbonise heat demand. Given the vast array of building types and heat demand profiles in this sector, there is no one-size-fits-all solution.
Many non-domestic clients are keen to proactively phase out fossil fuels, recognising that the commercial private sector is often targeted when regulatory pressures intensify, usually with limited government support. These clients frequently turn to their trusted heating contractors for advice on cost-effective, reliable solutions that pave the way forward.
While transitioning fully to heat pumps is the ideal route to achieving Net Zero targets, the diverse applications, building types, and locations can quickly temper initial enthusiasm. Costs can escalate rapidly, leading clients to retreat from heat pump solutions, often opting instead for another gas boiler replacement due to the high barriers associated with a full transition.
Hello to hybrid
There is, therefore, a strong case for offering solutions that guide clients toward heat pumps while managing current barriers and costs. Hybrid systems provide a flexible option, allowing clients to take their first steps toward decarbonisation without overwhelming financial or operational risks. Similar to how hybrid vehicles introduced the public to electrification in the transport sector, hybrid heating systems could be the catalyst for a broader shift towards heat pumps in non-domestic settings. Moreover, these systems can also help contractors who are less familiar with full heat pump solutions feel more confident in the range of options they can provide.
Hybrid systems, where gas boilers are retained for domestic hot water (DHW) production, can be particularly advantageous in situations with high hot water demand. By dedicating gas boilers to DHW, the need for high-temperature generation from heat pumps is eliminated, allowing them to operate at stable, low temperatures for extended periods. This can improve the seasonal coefficient of performance (SCOP) and reduce wear and tear on the heat pumps.
This approach also allows for smaller heat pump sizing, along with reduced pipework and thermal storage requirements. Dividing the system into high-temperature and low-temperature zones is generally straightforward in non-domestic systems, as most work will be confined to existing boiler rooms. The simplest configuration assigns heating loads to the heat pumps and DHW loads to existing boilers, although there are many other options to explore. These configurations can allow the heat pumps to pre-heat water and provide a gas boiler backup for high heating demands, offering flexibility while simplifying the design process.
Keeping the spark alive
One of the most common barriers in the non-domestic sector is the availability of sufficient electricity supply capacity, affecting both urban and rural buildings. In urban areas, local supply networks may already be at capacity due to the installation of multiple EV charge points and heat pumps, leaving the next customer-facing costly reinforcement works from the local distribution network operator (DNO). In rural areas, the supply may simply be undersized, or the availability of three-phase supplies may be limited without extensive work.
Hybrid systems that use gas boilers to reduce peak electrical loads can combat this supply challenge to help facilitate the introduction of heat pumps This is because they enable them to cover 70%-80% of annual kWh demand, with gas boilers handling peak loads. This is particularly useful on the coldest days when demand is highest and air source heat pumps operate at their lowest coefficient of performance (COP).
Bringing the old into the new
Hybrid systems can also serve as a practical steppingstone for older heating systems designed for 82°C/71°C flow and return temperatures, where the cost of a major renovation to accommodate low-temperature operations is prohibitive. With some basic rebalancing of radiators and the introduction of weather-compensated heating circuits to replace outdated on/ off controllers, significant performance improvements can be achieved. Weather-compensated heating circuits maintain consistent low flow temperatures throughout the year, enhancing heat pump COP and reducing energy consumption. These systems are particularly beneficial in non-domestic settings with constant heat demands, such as care homes and healthcare facilities, and should be considered essential.
Components and controls
As with any heating system, good design and the selection of efficient components, such as replacement pumps, are crucial for reducing energy consumption. The commissioning process is particularly important to ensure seamless operation as weather conditions change, so adequate time for commissioning should be factored into project estimates, with consideration given to seasonal commissioning visits.
Experience has shown that involving controls specialists early in the project is vital. Delayed engagement of the controls specialist can lead to unnecessary project extensions and callbacks to make adjustments. All parties must understand the system's operation to ensure reliable performance and low energy use.
To summarise, in order to increase the adoption of heat pumps in non- domestic buildings, we must adopt pragmatic approaches to overcoming the barriers preventing some systems from transitioning to electrification. Hybrid systems can help build client confidence in replacing gas boilers with heat pumps, which is especially important for critical heat requirements, such as in care homes. Although hybrid systems may seem more complex to contractors, with the right approach and manufacturer support, they can quickly become a familiar and effective solution.
www.bosch-industrial.com/gb/en
