Optimal design of energy conversion units and building envelopes for residential neighborhoods

  • Optimale Auslegung von Energiewandlungsmaschinen und Gebäudehüllen in Wohngebieten

Schütz, Thomas; Müller, Dirk (Thesis advisor); Hagenmeyer, Veit (Thesis advisor)

Aachen (2018, 2019)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2018


In recent years, many different envelopes and energy system components have evolved for application in buildings. Such modern, efficient and even renewable devices are indispensable for achieving politically motivated CO2 reductions. Furthermore, additional economic and ecological benefits can result from connecting multiple buildings via local electricity grids. The European Commission also foresees such developments as new business models. However, designing such systems requires methodical approaches that can be supported through optimization methods. Thus, this work contributes to this field by developing a thermal building model and energy system design formulations for simultaneously optimizing building envelopes and energy systems. Additionally, this work develops a decomposition method for extending these models to city districts. All approaches are formulated as multiobjective optimization for assessing economic and ecological factors. The developed building model fulfills standard tests for validating building simulation tools and leads to similar results as more detailed models. Additional verifications are conducted for individual building optimization. Furthermore, the decomposition approach is verified for two neighborhoods by comparison with the compact model formulation. Both formulations lead to similar results; however, the compact formulation is limited to at most four buildings, whereas the decomposition approach allows for scaling the models to more buildings and it converges in less computing time. The individual building optimization has been applied to the German residential building stock for a long-term planning. The results favor heat pumps over gas boilers due to expected decreased electricity tariffs. Furthermore, investments in low-emission energy systems are more cost-efficient for reducing emissions than building envelopes for the chosen future developments. The developed decomposition approach is used in a second case study consisting of thirteen buildings to investigate potential advantages of local electricity grids in comparison to unconnected settings. The findings highlight that a supply of individual, unconnected buildings through gas boilers is neither economically nor ecologically recommendable. In contrast, additional photovoltaic modules or a system combining photovoltaic modules and heat pumps significantly reduce costs and emissions simultaneously. When accounting for local electricity grids, total annualized costs and emissions can be reduced even further. The results show that energy systems present more cost-efficient methods for reducing emissions than envelope components. Furthermore, an uncertainty analysis shows that the optimization results are robust to variations in the input parameters. Overall, this case study illustrates that future business models utilizing local electricity grids can be beneficial in terms of costs and emissions.


  • E.ON Energy Research Center [080052]
  • Chair of Energy Efficient Buildings and Indoor Climate [419510]