Customized energy concepts for urban districts

On behalf of and in collaboration with Mainzer Stadtwerke Energie und Service GmbH, Fraunhofer UMSICHT developed customized energy concepts for a co-owners' association that take a holistic view of the technology, operation, and economic efficiency of the district. The starting point was a structured recording of the requirements and goals of the owners' association. On this basis, the existing heat and electricity supply was analyzed and local potential for renewable energies and storage was identified.

The next step was to develop supply concepts with future viability, which were evaluated in terms of quality and simulated using ESyOpT®/oemof.solph. The results show concrete technical and organizational options for action in the district. The approach included workshops, data preparation, potential analysis, and model-based simulations. This resulted in a clearly structured basis for the further development process.

Approach and methodology

• on-site workshop: clarify goals, requirements, and framework conditions; district inspection
• data preparation and potential analysis: review and supplement existing data; identify renewable potential and storage options
• concept workshop: discuss relevant technologies and possible combinations
• concept development and evaluation: development of basic concepts and variants; qualitative evaluation based on prioritized criteria
• results workshop: consolidation of findings and derivation of options for action
• simulative concept evaluation: model-based (ESyOpT®/oemof.solph) transparent comparison of concepts

The further development of urban and local energy supply systems presents property owners' associations with complex decisions: increasing demands for climate protection and efficiency, new technical options, and growing expectations for cost certainty and security of supply. The project team addressed these challenges by providing a neutral and reliable basis for decision-making for the district.

The concepts developed provide clarity about possible transformation paths, their emission effects, and their economic consequences. They show practical ways to meet legal requirements in the heating sector and facilitate coordination within the community. The project was characterized by a combination of moderated goal clarification, sound data analysis, potential assessment, and model-based evaluation. This resulted in a systemic view of technology, operation, and organization – transferable to similar districts.

The evaluation of the existing heat and electricity supply as well as several technical options reveals different transformation paths for the district. The variants differ in terms of renewable energy share, security of supply, complexity, and dependence on fossil fuels. In addition, the potential for photovoltaics, solar thermal energy, storage, and electric transportation was analyzed, and efficiency issues in the existing building stock were identified. Overall, the analysis provides a comprehensive picture of the technical possibilities and their respective operational consequences.

Evaluated supply concepts

• reference system (fossil fuel heat generation): supply via CHP and gas boiler, but dependent on natural gas and with increased maintenance costs; competition between combined heat and power base load generation for domestic hot water demand and PV yield in the summer
• CHP and heat pump: good greenhouse gas balance and high security of supply thanks to two base load generators; note investments and noise emissions; heat storage is a central component
• heat pump and gas boiler: clear division into base and peak load, high operational reliability; gas price risks exist; design of heat pump and storage is crucial
• heat pump and electric boiler: complete independence from gas; very low emissions with green electricity; high electricity demand at high flow temperatures; electric boiler suitable as peak load supplier
• solar thermal energy as a supplement: increases the proportion of renewable heat and reduces the load on the heat pump; however, increases system complexity and control and maintenance requirements; competition for space between photovoltaics and solar thermal energy
• electric transportation as a supplement: enables greater use of photovoltaic electricity and reduces traffic-related emissions; requires suitable charging management and consideration of winter grid loads

Findings from the inventory analysis

• significant losses occur in the existing system in terms of generation, storage, and distribution, particularly due to centralized hot water supply
• decentralized hot water supply (fresh water stations or electrical solutions) can reduce these losses and improve overall efficiency

• Miteigentümergemeinschaft in Mainz
• Mainzer Stadtwerke Energie und Service GmbH