First of all, we would like to wish you all a happy and healthy new year 2024. 2023 was an eventful year for us and we are looking forward to the new year with great enthusiasm.

In order to achieve greater penetration of district heating networks in Germany (and Europe) in the coming years, a high level of acceptance among end customers is extremely important. As a first step, it is relevant to evaluate how district heating is perceived and which key factors influence this perception. In this newsletter, we present an article that is less technical, but rather presents the results of a detailed survey.

We would also like to provide a few insights into the topology optimization of district heating networks. We are convinced that the optimization of topologies has a decisive advantage over conventional and manual approaches, especially for a seamless transition from municipal heat planning to the actual planning of district heating networks.

Influencing Factors and the Role of Regulation on the Perception of District Heating

The article "Perception of district heating in Europe: A deep dive into influencing factors and the role of regulation" by A. Billerbeck et al. evaluates an intensive survey that was conducted in a total of nine countries (Denmark, France, Germany, Lithuania, the Netherlands, Poland, Slovakia and Sweden). A total of almost 4,500 end customers took part in the survey. The questionnaire contained around 30 questions covering socio-demographic details, the current supply system, decision-making behavior for heating and cooling, current perceptions of district heating and attitudes towards stakeholders. The selection of interviewees was based on the demographic structure as well as the share of district heating in the respective national average.

Overall, the evaluation shows that the majority of respondents have a generally positive attitude towards district heating. This applies in particular to countries where district heating is already widespread (Denmark and Sweden). In countries where district heating systems are less common (Netherlands or Lithuania), on the other hand, a more critical attitude is evident.

The results indicate that socio-demographic factors play a less significant role in perception. Gender and education in particular have only a very minor influence on perceptions of district heating. The age of the respondents, on the other hand, plays a greater role; the older the end customers are, the greater their trust in district heating.

There are some differences between the countries. In Denmark in particular, the positive contribution to an ecological heat supply is decisive. This is explained by the already high proportion of renewable energies in the heating sector in Denmark. However, the result also indicates that the higher the share of renewable energy in district heating, the better the system is accepted. In countries where district heating is less strongly represented, trust in political decision-makers is relevant for the perception of district heating.

The regulatory framework conditions are an important factor in the assessment of district heating from the customer's perspective. District heating is perceived less positively as soon as there is a mandatory connection to the grid. In countries where connection is not mandatory, the district heating price in particular is perceived more positively. However, there are also exceptions to this rule. Especially in Denmark, where there are regulated prices that are still perceived positively. This indicates that the transparency of pricing and regulation is more important than the regulation itself. Last but not least, the results show that district heating is perceived much more positively when it is publicly owned.

Optimization of the Network Topology in District Heating Networks

The network topology of new district heating networks and the expansion of existing networks depends on a large number of factors and is therefore highly complex. Currently, networks are still often planned and dimensioned with a great amount of manual effort. The article "Geographically informed automated non-linear topology optimization of District Heating Networks" by R. Salenbien et al. presents an automated method based on non-linear optimization to find an optimal solution for the topology of district heating networks. For this purpose, geographical information (GIS) as well as information on the heat demand of the buildings is used. The result is tested on a case study and shows that the methodology can also be applied to a challenging problem with generators at different temperature levels and buildings with different consumption characteristics. The full description of the optimization model has been published in a previous article (https://doi.org/10.1016/j.energy.2022.126161). The presented article focuses the application on an urban area in Belgium (Waterschei).

A total of three different scenarios were considered. In the first scenario, two CHP units are used as a heat source, while the second scenario uses only one CHP unit, but a former mine can be used as a heat source. Waste heat at 60 °C is provided here. The third scenario increases the temperature compared to the second scenario; the temperature potential of the mine water is assumed to be 65 °C in this case. The generators are located in the north and south, dividing the region into two potential supply areas.

In the first scenario, both generation units have the same conditions, so that the connection to the southern or northern grid section is essentially determined by the distance to the respective generator. In the second scenario, the optimizer selects a significantly larger proportion of connections to the higher-temperature CHP unit. The reason for this is that the comfort conditions in the buildings (60 °C) must be maintained. In the second scenario, the renewable source can no longer ensure this after a few meters from the grid. As a result, fewer buildings are connected despite the lower heat generation costs. In the third scenario, the temperature is increased slightly, but the grid temperature (65 °C) is still limiting, so that only a few more streets are connected to the renewable energy source. This is supported by the effect that, due to more distant connections, a large pipe is built in the direction of the CHP anyway, which is then to be utilized more from a network perspective. Surprisingly, the costs with the renewable energy source are always higher than the costs of the supply with two CHP units. This shows the great importance of taking temperatures into account when optimizing heating networks.

Further Reading

As always, we recommend reading the articles in full. In addition, several articles have been published recently, particularly on the optimization of network structures (only small selection presented here), which we also consider relevant:

• "Topology optimization method of district heating system considering load uncertainty"
• "Nonlinear topology optimization of District Heating Networks: A benchmark of a mixed-integer and a density-based approach"
• "A Nonlinear Optimization Method for Expansion Planning of District Heating Systems with Graph Preprocessing"

The next issue of our newsletter will be published on February 7, 2024. Until then, please follow us on LinkedIn where we share small application examples and information with you.