As the district heating sector faces the challenge of decarbonising and meeting ambitious EU climate and renewable energy targets, the key to transformation becomes clear: lower network temperatures. However, achieving that turns out to be challenging. This article explores the requirement for lower temperatures, the complications of introducing decentralised renewables to the grid, and the solution to maintaining operational reliability while embracing lower temperatures. 

The district heating sector confronts the two-faced challenge of decarbonisation and growth. First, introducing renewable energy sources for decarbonisation requires rethinking day-to-day operations and transforming the heating network to a more decentralised operation. Secondly, with a third of the EU's final energy demand attributed to space heating and domestic hot water in buildings, meeting the 2030 target of 43% clean heat means that all district heating systems in Europe will be growing by 2% per year (!) for the next seven years. 

Both decarbonisation and growth indicate that the heating system of 2030 will look entirely different than it does today. It will be operated decentrally and fully sector-coupled with waste heat from industry and with electricity markets.  

However, the intermittency of renewables and the rising costs of fossil fuels make it difficult to determine the best path toward this future situation without risking a substantial increase in operational costs. 

Source: District heating levels of 2020 and 2050 for heating buildings for EU27 (EU and UK)  

The key to transformation is moving to lower operational temperatures across the heating system. This allows for better integration of renewable heat, increased use of (industrial) waste heat, and enhanced profitability of heat production technologies such as heat pumps, geothermal sources, or modern efficient CHPs. In addition, moving to lower temperatures leads to increased efficiency of the whole heating system, freeing up capacity for growth.  

"Efficiency as the first fuel" is the future vision of the district heating industry, and achieving it without lowering temperatures first is next to impossible. 

Source: Euroheat & Power, Fit for 2050 Unleashing the potential of efficient district heating and cooling to decarbonise Europe, 2023. 

In their outlook towards 2050, Euroheat & Power also recognises that district heating networks need to move to low temperatures to design a flexible and renewables-based system. 

So, the need for lower temperatures is clear. However, reducing temperatures can be rather difficult to achieve, seeing that most companies have already undertaken many initiatives to lower their heating curves but may soon run against the limit. For example, too high flow in the pipes may result in too high pressure drops. 

Can you achieve lower temperatures while growing and decarbonising your network?  

Until recently, an integrated understanding of demand and production was sufficient to operate the heating network. Production was often carried out at one or several main plants, and temperatures were regulated based on static operating rules.  

However, when a heating network grows and decarbonises with the introduction of decentral low-temperature heat sources, this is no longer sufficient. Understanding the dynamics inside the grid in terms of temperature and flow becomes increasingly complex. This puts heating companies at risk, given that simply reducing temperatures can cause operational issues such as too low temperatures in some network areas that may compromise supply reliability or present hydraulic constraints. 

The increasing volumes of data about the heating system that follow the introduction of smart heat meters present an opportunity to analyse data and generate insights. However, it's difficult for companies to draw the right conclusions about what is happening without solutions that process data and present it in a usable manner. 

As a result, operators often prioritise the security of supply by applying safety margins. This is due to the lack of comprehensive insights into temperature variations and hydraulic effects throughout the network. However, this is not the most cost-effective decision and presents an extremely limited view. It may lead to unnecessary heat losses, reduce flexibility, and even block further decarbonisation and network growth.  

This makes maintaining the security of supply more challenging in terms of capability (can I still deliver the heat?) and affordability (can I offer a fair price to customers?) across the value chain.  

How can companies reduce temperatures while staying operationally in control so they can continue growing and decarbonising safely? 

Dynamic and data-driven temperature control to enable transformation 

The key lies in adopting a dynamic, real-time, data-driven approach to understanding how temperatures propagate in the network. The conditions within the pipes are continuously changing on an hourly and daily basis. That is why working with daily or seasonal assumptions won't work. Real-time data is required to make the right economic decision based on the actual changes happening in operations.  

That way, companies can learn where their critical points are in real-time and locate potential opportunities for reducing temperatures without risking user commitments. Data can truly serve as the foundation for forecasting, heat planning, temperature control, maintenance strategies, production schedules, and even e-trading. 

The benefits of lower temperatures

Lower temperatures are vital for realising the full potential of district heating and cooling, as well as the integration of sustainable sources. This is confirmed by the IEA DHC guidebook on low-temperature district heating. The figure below shows that the benefits aren't only about reduced heat losses but also higher efficiency of many renewable sources. 

Overview of positive impact on reduced system temperatures. Source: IEA DHC, Low-temperature district heating implementation guidebook. 

Driven by user growth and the introduction of new renewables across the network, heating grids urgently need lower temperatures. And that is why the requirements for real-time, dynamic control have solidified across European heating companies. 

But how to get there? 

Traditional static temperature control solutions, such as heating curves and tables, come with significant limitations. As explained, they aren't future-proof anymore due to their lack of flexibility and disconnection from real-world system performance. 

The first step for many heating companies to embrace lower temperatures is to get rid of their static heating curve that has been in use for years. It can no longer properly support operators who face daily demand fluctuations, changes in heat source availability, and heat coming from different locations across the network. Decarbonisation and growth require a new way of thinking about temperature control. 

Modern end-to-end automation solutions that address these shortcomings allow companies to: 

Wrap up 

The future district heating system is a system that serves more users and uses fewer fossil fuels. How can companies achieve that? Lower temperatures are the enabler. However, the current ways of operating the system make it even harder to reduce temperatures. Security of supply and affordability of heat can never be put at risk, while insight into network impact is lacking. 

What companies need is real-time, dynamic temperature control to reach the lowest possible temperatures. This will increase the efficiency of renewable sources and lower heat losses across the network – enabling decarbonisation and growth. 

Explore this article to see how Gradyent helps district heating companies transform to low temperatures and how companies with large heating grids, such as Wien Energie, benefit from this approach. 

References

Geyer, Roman, Jürgen Krail, Benedikt Leitner, Ralf-Roman Schmidt, Paolo Leoni, Energy-economic assessment of reduced district heating system temperatures, Smart Energy, Volume 2, 2021, 100011, ISSN 2666-9552, https://doi.org/10.1016/j.segy.2021.100011

Mostafa Fallahnejad, Lukas Kranzl, Reinhard Haas, Marcus Hummel, Andreas Müller, Luis Sánchez García, Urban Persson, District heating potential in the EU-27: Evaluating the impacts of heat demand reduction and market share growth, Applied Energy, Volume 353, Part B, 2024, 122154, ISSN 0306-2619, https://doi.org/10.1016/j.apenergy.2023.122154.