Monitoring district heating networks: From the control centre to the digital twin

District heating pipes of the Steag Iqony Group
© Iqony

As part of the heat transition, district heating networks are becoming larger, more complex and more dynamic. With new heat suppliers, falling temperature levels and increasing demands for efficiency, security of supply and transparency, the need for precise condition monitoring is growing. Traditional control rooms and leak detection systems remain indispensable for this purpose, but in many places they are no longer sufficient. What is needed are integrated monitoring concepts that combine sensor technology, communication infrastructure, hydraulic models and operational control. The path leads from selective measurement monitoring to data-based platforms and digital twins.

Traditional monitoring remains the foundation

The monitoring of heating networks has traditionally relied on temperature, pressure and flow measurements at central network points, as well as on leak detection systems in pre-insulated pipe systems. This data is collated in the control room, visualised and used for operational management. Added to this are established methods of insulation and loop measurement, which indicate moisture ingress and leaks in the pipe insulation. In many networks, this combination still forms the backbone of operations today.

These systems are robust and have proven themselves in network operation. However, their limitations become apparent where gradual changes, small-scale leaks or hydraulic faults need to be detected as early as possible. Many existing networks still operate with heterogeneous measurement structures and varying levels of remote monitoring. As a result, it is often impossible to obtain a comprehensive picture of the current network status.

Digital leak monitoring in operation: sensors and monitoring systems provide real-time data on temperature, humidity and pipe condition – the basis for predictive maintenance and efficient servicing
© ISOPLUS

Measurement points become data repositories

With increasing digitalisation, the role of monitoring is undergoing a fundamental transformation. Sensors now deliver operational data at a higher temporal resolution, communication modules automatically transmit it to platforms or control systems, and software not only analyses it but also establishes connections between data points. In this way, individual measurement values are transformed into reliable status information. For network operators, the main advantage lies in the continuous identification of trends – such as pressure losses, rising humidity, temperature deviations or changes in load conditions. This significantly improves the basis for maintenance, servicing and operational interventions.

Not every network operator starts out with a fully digitalised heating network. Research shows that a phased approach makes sense, particularly for small and medium-sized systems. The AGFW Nemo project has developed a standardised, cost-effective method for the energy monitoring of district heating systems, which is designed to be applicable regardless of the system’s size and serves as a practical introduction to structured minimum monitoring. This brings not only high-end digitalisation into focus, but also the question of how a robust minimum data set can be established economically.

In parallel, digitalisation is already being driven forward in pipeline construction. Mobile documentation systems for welding and socket joint work, digital test reports and centrally accessible quality databases create a consistent data foundation spanning planning, construction and operation. In this context, companies such as Isoplus are working on solutions that more closely link quality assurance on site, documentation and subsequent condition assessment. As a result, digital quality assurance and operational monitoring are increasingly converging.

Remotely controlled valves in a smart district heating network
© 3S Consult

3SmartFW: Leak detection without copper sensors

The 3SmartFW research project, on which 3S Consult, Fraunhofer IOSB and 3S Antriebe, amongst others, have collaborated with a network operator, demonstrates just how far such an integrated approach can go. The aim was to link the components of an intelligent district heating network in such a way that leaks are not only detected once the insulation has become significantly damp, but can be identified and localised as early as possible using real-time operational data. The approach combines online network monitoring, smart metering, remotely controllable valves, a digital platform and a hydraulic model of the network.

Leak detection using the so-called dual-model method is particularly relevant. In this method, real-time pressure measurements are not considered in isolation, but are fed into a hydraulic model. In the first step, this allows the specific area where the leak is likely to be located to be identified. In the second step, this area is mathematically ‘scanned’ along the pipes to narrow down the most likely leak location. The denser the network of pressure measurement points, the higher the location accuracy. Practical trials have shown that, with a suitably developed measurement infrastructure, spatial narrowing down is possible within a range of approximately 5 to 10% of the route length.

Furthermore, the project demonstrated that leak detection can be integrated with remotely controlled valves and digital user interfaces to form an operational emergency response plan. If affected network segments are isolated quickly, water losses can be limited and consequential damage reduced. Monitoring thus becomes not merely a tool for observation, but an integral part of active operational management.

The digital twin as the next stage

The digital twin is the logical next step in the development of this data-based monitoring. It combines real-time measurement data with a hydraulic-thermal network model and continuously maps the actual behaviour of the heating network. This means that not only can leaks or anomalies be detected, but load changes, switchover operations or interventions can also be virtually analysed before action is taken in the real network. The fact that digitalisation is increasingly being seen as a strategic building block of heating network transformation is also demonstrated by the work of Fraunhofer ISE on the transformation and digitalisation of heating networks.

This is particularly relevant for operators of larger networks and interconnected systems, as district heating networks will need to be operated more flexibly in future: with multiple generators, storage facilities, variable feed-in and more fluctuating load profiles. Companies such as Iqony, which operate large district heating infrastructures whilst simultaneously driving forward the decarbonisation of their heat generation, illustrate this development. Where industrial waste heat, storage facilities, different types of generation and resilient network structures come together, there is a growing need for robust state models and forward-looking operational management.

Furthermore, data-driven methods not only serve to detect faults but can also directly unlock operational efficiency potential. The Fraunhofer IEE reports for the ML4FW project that AI-supported optimisation of controller parameters has been shown to reduce return temperatures by 2 to 3 K and significantly lower energy consumption. This is particularly relevant for district heating networks, as return temperatures have a direct impact on network losses, generation efficiency and the integration of renewable heat sources.

The expansion of local and district heating networks is gathering pace; shown here is the laying of a flexible, pre-insulated CALPEX-PUR-KING pipe system from Brugg Pipes in a pipe trench
© BRUGG

Digitalisation doesn’t just begin during operation

For planners, pipe system manufacturers and network operators, it is crucial to recognise that the subsequent quality of monitoring depends heavily on the quality of the upstream data. When welding parameters, socket documentation, material data, GPS positions and test reports are digitally recorded and stored in a structured manner, this not only improves traceability but also facilitates future maintenance and enhances model quality.

At the same time, pipe system technology itself is coming increasingly into the focus of digitalisation. Pipe system suppliers such as BRUGG are prime examples of flexible system solutions that prove their worth particularly in densely built-up areas, for property connections and in complex route layouts. With such systems, the importance of seamlessly integrating material, installation and operational data into digital planning and monitoring environments also grows. The pipeline is thus no longer merely a thermal transport route, but part of a networked infrastructure in which materials, sensor technology, communication links and software interact. The test and validation environments set up in the Fraunhofer IEE’s District LAB demonstrate the extent to which component development, operational management, simulation and quality issues now influence one another.

Challenges and Outlook

Despite all the progress made, implementation remains challenging. The biggest hurdles often lie less in the sensor technology itself than in the integration of different data sources, proprietary systems and inconsistent interfaces. Added to this are requirements regarding IT security, data availability and model quality, particularly in existing networks.

The direction is nevertheless clear: heating networks are evolving from traditionally monitored infrastructures into digitally described and increasingly model-based systems. In practice, for pipeline construction and district heating, this means that monitoring should not be viewed in isolation, but as an end-to-end task spanning the entire lifecycle of the network. Projects such as Nemo address the cost-effective entry point via minimal monitoring, 3SmartFW demonstrates the integration of leak detection, platform and digital twin, and research environments such as the District LAB create the conditions for validating new components and operational strategies under real-world conditions. As a result, monitoring is evolving from a control room instrument into a central component of the technical and organisational transformation of heating networks.