DISTRICT HEATING/HEAT NETWORKS
Choosing the right heat source for the network
Heat networks are set to play a much larger role in the UK’s transition to low carbon heating, expected to provide 7% of the UK’s heating demand by 2035 and 20% by 2050, compared with approximately just 3% today. Offering a flexible way of distributing heat (or cooling) from centralised plant to a wide range of domestic and commercial buildings, the success of these schemes relies heavily on choosing the right HVAC source. Tim Mitchell, sales director for Klima- Therm, explains
M
odern heat networks vary widely in scale and design. Some serve a single residential block, while others connect hospitals, offices,
schools, leisure facilities, homes and public buildings across a wider district. This diversity means the chosen HVAC solution/s must meet often varied requirements, ensuring end user comfort, efficiency, sustainability and year-round climate control. At the time of writing, we are in the midst of one of the hottest summers on record – adequate cooling should now be an essential part of all building design.
While heat networks can take advantage of heat sources that would otherwise be difficult for individual buildings to use - waste heat from industry, energy-from-waste plants and naturally occurring sources such as geothermal energy or rivers - heat pumps are likely to be a feature of almost all schemes. The Heat Pump Association’s recent report, Accelerating the Widescale Deployment of Heat Pump Driven Low Carbon Heat Networks and Drilling, outlines a raft of policy recommendations to accelerate the deployment of heat pump driven networks, including shared ground loops and ambient systems, combined with waste heat, solar thermal and other recoverable sources. In most cases, these heat pumps will be of the high temperature variety.
Why high temperature?
High temperature heat pumps provide the versatility to meet varying building needs, giving designers more options when connecting existing buildings, serving commercial hot water loads or phasing projects over time. They can also reduce the need for additional top-up heat sources, provided they are correctly selected and integrated. The aim should be to meet the required comfort and hygiene standards while keeping operating temperatures as low as the network practically allows - lower temperatures generally support better efficiency and reduced operating costs.
Choosing the right heat pump
Heat pumps used in district heating schemes may operate for long hours across a wide range of ambient conditions, return temperatures and load profiles. Specifiers should therefore look at seasonal performance, part-load operation, defrost strategy, controls and how the unit
performs at the flow temperatures the network will actually require.
The ideal heat pump should be source-flexible, control-ready and able to operate efficiently within the selected network architecture. It should also be capable of working alongside thermal storage, secondary heat sources or future network expansion, rather than locking the operator into a single operating mode. A ‘smart’ mode linked to primary generation availability or grid flexibility is also becoming a default requirement. As heat networks are often used in urban
environments, noise is also a consideration. Heat network zoning is intended to identify areas where heat networks are expected to provide the lowest-cost, low-carbon heating option, which means more projects are likely to be developed close to homes, workplaces, healthcare settings and education buildings. Acoustic performance, night-time operation and plant location should therefore be considered from the earliest design stages. The best heat pump solution in a high-density setting, should be straightforward to deliver on a constrained site, accessible for routine service, compatible with the project’s controls strategy and supported by clear monitoring data. Features such as integrated pumping options, modular control, master/slave operation, remote monitoring capability and clear user interfaces can all help operators keep systems performing as designed.
Single-source heating, cooling and hot water
Reversible and polyvalent heat pumps are particularly attractive where a scheme has both heating and cooling requirements. Instead of treating cooling as a separate design challenge, a reversible or polyvalent unit can provide true climate control and domestic hot water production from a single product. In the right application, this can reduce the need for separate chillers and boilers, simplify procurement and reduce the number of interfaces that must be installed, commissioned and maintained. That simplicity can reduce overall cost. Heat networks are long-term infrastructure assets, and the initial plant selection influences plantroom space, access requirements, maintenance regimes and resilience. A single-source approach can reduce system complexity and may also reduce the number of separate components that can fail, therefore contributing to leaner ongoing maintenance.
Single source heat pump solutions from Rhoss - WinPACK ECO HT65
The Rhoss WinPACK ECO HT65 heat pump range, distributed by Klima-Therm, is a reversible heat pump platform designed for small to medium systems. It can provide cooling, heating and domestic hot water from a single source, potentially replacing separate chillers and boilers. The range uses low GWP R454B refrigerant and a dual-circuit arrangement with four scroll compressors and vapour injection technology. Hot water can be produced up to 65°C and WinPACK ECO HT65 can operate in extreme temperatures – between 55°C and -20°C. Seven sizes are available, with heating capacities from approximately 120kW to 190kW, including a high-efficiency ‘T’ version and a reduced-noise ‘Q’ version. Other available features include integrated pumping groups, master/slave control, partial heat recovery, Smart Grid and photovoltaic contacts, an HMI touchscreen and microprocessor control with Adaptive Function Plus logic.
Environmental performance and refrigerant choice
The environmental credentials of a heat network depend on more than the heat source alone. Low carbon performance should be assessed using the expected operating profile, grid carbon intensity, heat losses, pumping energy and the carbon impact of any plant used during peak load periods. Refrigerant choice is also part of the equation, particularly as lower GWP refrigerants become more important to responsible specification and the F Gas phase down.
For heat network applications, the most suitable heat pumps will combine low carbon operation with good practical environmental performance. This includes using low GWP or natural refrigerants, achieving efficient seasonal operation, supporting heat recovery and reducing reliance on fossil-fuelled back-up wherever practicable.
Designing for growth and regulation
To help meet net zero targets, the district heating market is becoming more structured. Government guidance points to heat network investment potential of £60 billion to £80 billion by 2050, while the emerging policy framework includes zoning, consumer protection and technical assurance. Energy UK has also highlighted the role of thermal storage and multiple heat sources in providing flexibility and resilience to the wider energy system. For specifiers, this means today’s heat pump choices need to work not only for the initial phase of a scheme, but also for future network expansion, regulation and performance expectations. The ideal unit will offer reliable high temperature output where required, efficient operation across the real duty cycle, low environmental impact, manageable noise levels, good maintainability and the flexibility to integrate with storage, recovery and controls. Heat networks are set to expand from a small
share of UK heating demand to a mainstream decarbonisation solution; it’s important we make the right choices now to ensure their long- term success.
26 BUILDING SERVICES & ENVIRONMENTAL ENGINEER SEPTEMBER 2026 Read the latest at:
www.bsee.co.uk
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