Decarbonization of District Heating Networks and Integration of Renewable Heat Sources

this is issue 30 of our heatbeat Research Newsletter with an update on recent research results from the field of district heating and cooling. When looking at the most recently published papers in this field, we continue to see much work regarding the decarbonization of the heat sector and the integration of renewable heat sources.

For this issue, we selected an overview of the potential for using lake-water in district heating and cooling, a study on the influence of building retrofits on the feasibility of district heating, and an interesting case study for the transformation to green heat in the city of Rostock.

Lakes as Energy Sources for Heating and Cooling in Europe

In the paper The potential of lake-source district heating and cooling for European buildings by Eggimann et al. we see a great overview of how lake-water can play a significant role in decarbonizing the heating and cooling sector all over Europe. In this paper, the authors used open data (e.g. from OpenStreetMap) to analyze the total heating and cooling demands around all major lakes in Europe and identify the techno-economic potential of meeting these demands via lake-water as an energy source.

Depending on the distribution of lakes and buildings in close proximity, the study finds the largest potentials in Italy, Germany, Switzerland, and Turkey. Overall, the study finds a cooling potential for Europe of 1.9 TWh/year or a combined heating and cooling potential of 11.3 TWh/year while at the same time determining a potential to save up to 0.8 TWH/year of electricity.

What we found especially interesting was the sensitivity of these results: The paper determines that the techno-economic potential increases by around 2.5 TWh/year if the electricity price doubles, but the potential goes down by around 1 TWh/year for every percent increase of the assumed interest rate. Thus, this is a great example for how a holistic techno-economic approach is needed to address the uncertainty of market forces on the optimal technical solution to decarbonization.

Influence of Building Retrofits on the Development of District Heating

In another recently published study, Popovski et al. investigate the Decarbonization of district heating and deep retrofits of buildings as competing or synergetic strategies for the implementation of the efficiency first principle. For this analysis, the authors evaluate how different building retrofit rates (1, 2, or 3 %/year) influence the suitability of district heating compared to individual heating for each building in 5 cities with different boundary conditions like district heating market shares and climate zones.

The study shows, that even for high retrofit rates and the resulting reduction in heat demand, district heating remains a viable option to cover between 49 and 83 % of the total heat supply in the investigated cities. Even though the authors expect that the price of district heating can increase by 14 - 35 %, they conclude that under their assumptions maximizing the number of buildings connected to district heating leads to lower overall heating costs than individual building options.

Transformation to Renewable District Heating in Rostock

And even though it is still in pre-print, we already wanted to include the paper Transition of district heating from fossil to renewable energies – pathways analysed by dynamic simulation by Wittenburg et al., because it presents a nice case study for the transformation of an existing district heating network in the city of Rostock.

This analysis is based on a dynamic simulation of 5 different generation scenarios to meet the forecasted heat demand of the Rostock district heating network in 2035. In all those scenarios, the authors consider a wide range of heat sources ranging from waste heat from a large-scale electrolysis plant, sewage heat pumps, incineration of sewage sludge and waste, as well as large thermal storage capacities. Between the scenarios, the size of the electrolyzer and storage options varies as well as the inclusion of other heat pumps, industrial waste heat, and biomass.

We especially recommend this study because it not only compares these scenarios regarding different KPIs like investment, operating costs, and climate impact. The study also shows the yearly heat supply time series and the shares each heat source covers. This gives a detailed picture of how a carbon-neutral district heating system can work by combining a wide variety of heat sources and can be a valuable resource for transformation plans in other cities.

Further Information

Already tomorrow (April 6), we're happy to have the opportunity to present our work from the research project TransUrban.NRW within the EWB-Stunde series of webinars. We'll share how our heatbeat Digital Twin helps to realize 5th Generation District Heating and Cooling networks from planning to operation.

The next issue of our newsletter will be published on May 3, 2023.