Heat decarbonization in municipalities - Accounting for the local spatial context in techno-economic modeling

Abstract: In Europe, 57% of the energy used for space and water heating is derived from the combustion of fossil fuels, whereas only 24% comes from renewables. Compared to the wide-reaching transmission of electricity between countries, the supply of heat predominantly occurs at the local or individual level. Additionally, the local spatial dimension which influences the supply and consumption of heat implies that the choice of heating solutions is heavily dependent upon the local context. At the same time, it has been pointed out that the local spatial dimension does not receive adequate attention when formulating strategies for the energy systems transition. By addressing heat planning at the local level, it becomes possible to tailor solutions that take the unique local spatial conditions into account. The impacts of the local spatial dimension on heating solutions underscore the important roles played by local authorities, which have comprehensive knowledge of the local context, in research on heat decarbonization. This thesis presents a participatory modeling methodology for investigating local heating system transitions, combining techno-economic modeling and spatial analysis. The developed methodology is divided into five steps: Step 1 – Reviewing the planning processes; Step 2 – Inclusion of spatial features; Step 3 – Scenario formulation; Step 4 – Energy systems modeling; and Step 5 – Evaluation of modeling outcome. The methodology has been tested in both urban and semi-rural case studies, described in the three appended papers. Stakeholder interactions were found to be critical in Step 2 (Inclusion of spatial features) in providing preferences for dividing municipalities into districts to be modeled, and in Step 3 (Scenario formulation) for delimiting the scope of technology options. For example, in the urban case study, the input from municipal planners included their preferences in regard to the number of districts and the criteria to subdivide the municipality to be modeled. Local preferences played a significant role in Step 3, with biomass being excluded as an option due to concerns about local air pollution. In the semi-rural case study, stakeholder interactions were highlighted, particularly on the selection of technology options in the model. As a result, the scenarios took into account the preferences of local energy planners regarding technologies such as biogas injected into the natural gas grid and utilizing excess heat from the municipal wastewater treatment plant and neighboring industries in district heating system. This is particularly significant, as these steps are closely linked to the modeling outcomes, ensuring their relevance for the specific municipality and its unique conditions. The impact of the high spatial resolution is highlighted, with the modeling results showing different heating technology preferences depending on the differences in district properties. This indicates that the model results reflect the local spatial context and thus, can suggest district-specific strategies for the municipality planners. This thesis concludes that establishing a robust and long-term strategy early in the planning process is crucial, particularly from the standpoint of municipal planning. Furthermore, this thesis shows that the strategies employed for heat decarbonization will differ between urban and semi-rural areas, as well as between districts within these areas due to the large variety of spatial conditions pertaining to heat supply, distribution and consumption. Consequently, it emphasizes the importance of the participatory approach in order to understand the diverse local spatial contexts.