Optimal Design of Building Energy Systems for Residential Buildings

This paper addresses the design and sizing of building energy systems for residential applications with exact optimization methods. Similar studies often rely on large simplifications, such as scaling the nominal outputs of representative heat pumps, boilers, combined heat and power units and electrical heaters. In contrast, this paper presents an optimization model in which the building energy system entirely consists of a pool of predefined types of devices, thus enabling a higher modeling accuracy of the individual types. The model considers the aforementioned heat generators as well as renewables like photovoltaics and solar thermal collectors. Batteries and thermal buffer tanks are included as storage technologies. The model is applied to three residential buildings significantly differing in size and usage. The results indicate that gas boilers and combined heat and power units present the most economic options. The findings further suggest that photovoltaics are economically feasible whereas batteries are currently not profitable. The developed model offers a higher modeling accuracy than the simplified model at the costs of long computing times. Thus, the simplified model is further used to limit the search space of the developed model, reducing the deviation from the developed model in terms of accuracy while still maintaining a viable computation time.