Energy centre in a heat network: the heart of climate friendly district supply
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Die Kernpunkte auf einen Blick: Was leistet eine Energiezentrale im Wärmenetz?
- Das technische Herzstück (Zentraler Knotenpunkt): Die Energiezentrale bündelt, orchestriert und reguliert verschiedene regenerative Quellen wie Großwärmepumpen, Grundwasser, Aquathermie, Solarthermie oder industrielle Abwärme an einem zentralen Ort.
- Höhere Effizienz durch Skalierungseffekte: Im Vergleich zu Einzelheizungen pro Gebäude ermöglicht ein zentrales System größere Pufferspeicher, eine gleichmäßigere Anlagenauslastung und bessere Jahresarbeitszahlen.
- Systemprägung durch die Position: Bei klassischer Fernwärme speist die Zentrale Wärme auf hohem Temperaturniveau (70–90 °C) ein. Bei kalter Nahwärme verteilt sie Anergie (5–25 °C), während die eigentliche Temperaturanhebung dezentral am oder im Gebäude erfolgt.
- Wirtschaftliche Dimensionierung: Typische Quartierslösungen bewegen sich im Leistungsbereich von 1 bis 10 Megawatt und können flexibel mehrere hundert bis tausende Wohneinheiten hocheffizient und netzverträglich versorgen.
What is an energy centre? Definition and role in a heat network
Question: When we talk about the heat transition, district solutions and heat networks, the term “energy centre” comes up very quickly. For many, it initially sounds like an abstract technical term that is hard to grasp. So let us start right at the beginning: What actually is an energy centre?
Dr Markus Pröll: Put simply, the energy centre is the place where heat for an area is brought together and distributed from there. You can think of it as the heart of the heat network, where the various energy sources converge and are transferred into an ordered, controllable system.
Question: In traditional projects, many still think of “the big boiler in the basement” that supplies a building. Modern district solutions go significantly beyond this and consider entire areas. Can we say that the energy centre is more the control hub of the overall system rather than simply an oversized boiler room?
Dr Markus Pröll: Exactly. It is not a single device, but a combination of several components that are coordinated with each other. This is where we bring together all the energy sources we want to use: large‑scale heat pumps, groundwater or surface water bodies, waste heat from industrial sites or also conventional peak‑load boilers. In addition, there are storage systems, distribution, hydraulics and the entire control and supervisory technology with which we optimise operation.
How does an energy centre work in technical terms?
Question: What exactly happens there from a technical perspective? Most people probably imagine it as simply a “big heating system”.
Dr Markus Pröll: In essence, three things come together in the energy centre: we collect energy, we raise it to the required temperature level, and we distribute it into the network. Collecting means: we connect different sources – for example a groundwater well field, a cold local heat network, solar thermal arrays or industrial waste heat. Raising the temperature means: heat pumps, possibly boilers and thermal stores bring the energy to the temperatures that the network and the buildings require.
Question: And distribution is then “just” hydraulics and pumps – or is there more to it?
Dr Markus Pröll: Distribution is hydraulically and in terms of control engineering quite demanding, especially when several generators and storage units have to interact smoothly. Higher‑level energy management, operating schedules, source prioritisation, temperature control and efficiency optimisation – all of this is orchestrated in the energy centre. Ultimately, this interaction determines whether the overall system later runs efficiently, robustly and with good controllability.
Central energy centre or individual heating? Advantages of a shared supply
Question: In discussions with owners or operators, the question often arises why one would opt for a central system at all. From their point of view, individual heat pumps or boilers per building initially appear more flexible and less complex. From a planning perspective, what are the arguments in favour of an energy centre nonetheless?
Dr Markus Pröll: The major advantage of an energy centre is that I have far more degrees of freedom at one point. I can combine different sources, size plant larger and therefore often more efficient, and optimise operation centrally. Many renewable sources – groundwater, waste heat, large‑scale solar thermal – only become economically viable when I consider several buildings together.
Question: So in the end, is it mainly economies of scale and efficiency gains that tip the balance against individual solutions?
Dr Markus Pröll: Exactly. A central plant can, for example, achieve a more even utilisation and thus better seasonal performance factors, especially for large heat pumps. In addition, I can dimension storage larger, smooth peak loads and thereby limit electrical capacity demand as well as flow temperatures in a targeted way. This feeds directly into efficiency, operating costs and grid compatibility.
Energy centre in district heating and cold local heat: comparing system variants
Question: In projects, the question keeps coming up: “Does the energy centre sit before or after the network?” What is your answer?
Dr Markus Pröll: That both variants exist – and that this fundamental decision significantly shapes the system concept.
Question: Let us break that down: What is the classic case?
Dr Markus Pröll: Classically, the energy centre is located at the source, generating heat at network temperature level and feeding it into a hot network with correspondingly high flow temperatures. This is the principle behind most existing district and local heating networks: central heat generation, distribution at, for example, 70 to 90 degrees Celsius, and delivery via building interface stations.
Question: Cold local heating networks more or less reverse this picture by distributing the source and only raising the temperature at a later stage. For planners, this means a different allocation of technology between the centre and the buildings. How does the role of the energy centre change in such concepts?
Dr Markus Pröll: In cold local heat systems we initially only distribute the source, meaning energy at a low temperature level, typically 5 to 25 degrees. The actual temperature lift then happens in a decentralised way – either in a smaller energy centre closer to the consumers or directly in the buildings via heat pumps. This reduces network losses and increases flexibility, but requires more plant in the buildings.
Question: So one could say: by deciding on the position of the energy centre, you are not only choosing “where the boiler sits”, but how the overall system behaves?
Dr Markus Pröll: That is exactly how I often put it: It is not just about where the technology is located, but how the entire system functions – including the temperature regime, network losses, redundancy concept and responsibilities within the buildings.
Output and size: how do you size an energy centre?
Question: For project communication, having a realistic feel for order of magnitude is helpful. How big is such an installation typically? Many find it difficult to gauge.
Dr Markus Pröll: It is hard to answer in general terms, because the task defines the size. We have projects where the energy centre fits into an existing plant room and provides in the range of a few hundred kilowatts up to perhaps around one megawatt of thermal output.
Question: From what point do you, based on your experience, tend to talk about an “energy building” rather than a plant room?
Dr Markus Pröll: At the other end of the spectrum we are talking about stand‑alone energy centres that supply entire districts, sites or industrial areas with several megawatts. Typical district solutions are often in the range of roughly one to ten megawatts; for larger urban areas or industrial applications it can be much higher. Then we are more in the realm of classical district heating or industrial power plants.
Question: For decision‑makers, another important point is how many users can be supplied by a single plant. In marketing, the communication is often in “dwelling units” or “buildings”, while the design is based on load profiles. Can we still give a rough sense of what a few megawatts can deliver?
Dr Markus Pröll: Roughly speaking, you can say: an energy centre with several megawatts of output quickly supplies several hundred to a few thousand dwellings – depending on building standard and proportion of domestic hot water. For technical design, however, we work with calculated heat loads, coincident load profiles and full‑load hours, not with generic rules of thumb.
Design and architecture: what does an energy centre look like?
Question: I’d like to touch on the visual aspect again—when I hear "energy center," I tend to picture a spectacular facility. In reality, though, people often walk right past them without even noticing them, don't they?
Dr. Markus Pröll: That’s true. Many energy centers are rather inconspicuous from the outside—container units, utility buildings, basement rooms, or structures that are partially underground. Sometimes they feature distinctive architecture and are clearly visible as an "energy building," while at other times they are deliberately tucked away in the background, such as in maintenance yards or inner courtyards. It really depends on the specific setting and the budget the client is willing or able to spend—but in principle, anything is possible.
Ultimately, however, the interior is what matters most to me. That is where we determine which energy sources to combine and how, the layout of the hydraulic system, the control strategy, and the reserve capacities planned for outages or future expansions. These factors determine whether the energy center operates efficiently, stably, and with room for expansion in the long run—or whether it quickly reaches its limits when faced with load fluctuations or disruptions.
What does an energy centre cost, and when is it worthwhile?
Question: Finally, the question that comes up at some point in every meeting: What does such an energy centre cost?
Dr Markus Pröll: The honest answer is: it depends – and on a great many parameters. Investment costs depend, among other things, on the installed capacity, temperature requirements, number and type of generators, storage configuration, level of automation and, of course, the structural framework conditions.
Question: Can we nevertheless state rough ranges so that project sponsors have an initial indication?
Dr Markus Pröll: In very broad terms and without any claim to general transferability, we occasionally use specific investment costs per kilowatt of installed capacity in early studies. Depending on the system, such guide values are in the range of several hundred to well over one thousand euros per kilowatt of thermal output – including generators, storage, hydraulics and control, but excluding the associated heat network. For concrete projects, however, we quickly replace such rules of thumb with robust cost estimates based on a technical preliminary design.
Question: And compared with a “simple individual heating system”?
Dr Markus Pröll: Centralised systems with an energy centre initially require higher investment in generation, storage and networks, but can be economically attractive over their lifetime thanks to better efficiency, utilisation of renewable sources and optimised operation. The key is to think in terms of the overall system: energy centre, network, buildings and user behaviour must fit together – then the energy centre can be a major building block of a resilient and climate‑friendly heat supply.
Thanks for the conversation, Markus!
The interview was translated with AI