HEATING TECHNOLOGY
Swapping gas-fired systems with heat pumps
Simon Witts, a director at VA Sciences – a scientific consultancy based in Vermont, Victoria, in Australia, which offers a fully developed suite of STEM (science, technology, engineering, and mathematics) services, discusses the integration of heat pumps into existing hospital systems. He examines the challenges and necessary adaptations for replacing traditional gas-fired systems with heat pump technology during the electrification process.
Heat pumps, essential for generating hot water, have operating parameters that differ significantly from conventional systems, requiring modifications to existing infrastructure such as risers, pumps, and main distribution systems, to handle lower temperatures and higher flow rates. The transition is particularly complex in healthcare facilities, where complete re-piping to optimise heat pump performance may be impractical, often leading to sub- optimal operation. This article underscores the importance of distinguishing between heating and domestic hot water systems, as they operate at different temperatures, which impacts their energy efficiency and overall system performance.
Integration of heat pumps The all-electrification process in most instances requires the use of heat pump-based technologies to generate the hot water. When considering system replacements, the installed systems in existing hospital systems have different requirements. The integration of heat pumps into legacy systems is not just a case of swapping one heat source for another. Heat pumps invariably have different operating parameters to ‘traditional’ gas-fired heating water and domestic hot water systems. These parameters are not always compatible with the embedded infrastructure within an existing facility. When swapping gas for electricity using heat pumps, the design needs to consider the system and its operation, not just the swapping out of the heat source. If the design parameters are altered to suit common heat pump performance specifications (lower temperatures and higher flow rates), then it’s likely this will result in changes to the existing infrastructure, such as risers, pumps, and main distribution. So, when considering integration into an existing healthcare facility, it may have to be accepted that in most buildings and systems the heat pumps will be operating sub-optimally, since it may well not be practical to completely re-pipe the existing systems in the building to accommodate common heat pump systems’ optimal flow rates and temperatures. Such integration may also introduce other factors, such as the need for enhanced infection control measures. The distinction between heating and Domestic Hot
Water (DHW) is important, as the different temperatures mean that the coefficient of performance (CoP) of the two systems can vary significantly. Design conditions are key – for example at 3 °C ambient, the CoP of a heat pump supplying 60 °C DHW is around 3.5. For a Low Temperature Hot Water (LTHW) system at 80 °C, with a return temperature of 60 °C, the CoP is closer to 2, i.e. much less efficient in the use of energy to create heat.
New-build installations Choosing system-appropriate heat pump technology that is able to provide the correct temperatures and flow rates for buildings should not present too much of a challenge for competent healthcare building services designers, as they have full control over the primary and secondary water circuits, and incoming power requirements, and should be fully aware of the activities undertaken in the building. Swapping gas out of existing facilities is, however, a very different proposition.
Existing installations
n Estimating the demand In most hospital facilities the systems that serve the buildings have evolved over time – starting from an initial coherent design, and slowly morphing into systems that have been extended, cut back, or repurposed. The result of this evolution is that the building systems are often performing in a manner distinctly different from that envisaged in the original design parameters. Establishing the required duty is the first challenge in retrofitting a heat pump.
n Availability of power The second challenge in retrofitting a heat pump will be the availability of power from the local plant level mechanical switchboard. When the system uses gas as the primary thermal fuel, the mechanical switch board (MSSB) only supplies the power to the pumps for circulation and controls to enable the equipment to
February 2025 Health Estate Journal 31
Heat pumps, essential for generating hot water, have operating parameters that differ significantly from conventional systems, requiring modifications to existing infrastructure.
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