Master's Thesis Anna Scholl


Thermal heat supply scenarios for a changing building stock - Exemplary application for Jülich Research Centre using evolutionary algorithms

In order to reduce the global energy consumption, the energetic optimization of large building stocks arouses more interest. Additionally, its a challenge that large building stocks are constantly changing, since buildings are retrofitted, demolished or new buildings are build. To find an optimal energy supply systemfor such building stocks this thesis deals with the design of thermal heat supply scenarios for a changing building stock. A tool is developed, which enables the energetic and economic optimization of an energy supply system based on evolutionary algorithms. The tool is applied to the research centre Jülich, which currently utilizes heat from a district heating network. Since the heat is provided by a lignite-fired power station, which will be decommissioned in the next years, the demand for a new energy supply system has rapidly increased. Therefore, proposals are offered to retrofit the whole building stock and a number of energy supply systems are provided. In a first step a variety of retrofit scenarios for the building stock is received, where the objective function is the maximization of the energy savings by retrofit and minimizing its costs. Every scenario describes a sequence of building refurbishments. After selecting one retrofit scenario the energy supply system is optimized. Subsequently, a Pareto Set of optimal systems is provided depending on prime energy and net present value. In this way, it is possible to present a multitude of solutions and therefore the tool can be used as a decision-making aid for a new energy supply.

By analyzing different parameters, the effect of external conditions on the choice of the energy supply system can be investigated. In this way, the retrofit of the building stock, the interest factor, the flow temperature of the heating network, the number of starts and stops of the CHPs and the weather are examined. Exemplary, only the influence by retrofitting the building stock is presented here: it can be observed, that the cost saving obtained through the new energy supply system exceeds the cost for retrofitting the campus also at high renovation rates. In this way, the combination of optimizing the energy supply system and retrofitting the building stock is always economic independently of the economic efficiency of retrofitting the building stock. However, it is important to note that retrofitting the building stock affects the prime energy consumption of the energy supply system in a positive way. So, at higher renovation rates and equal net present value lower prime energy consumptions can be achieved. In a last step, fist investigations based on a district heating network simulation are enquires to analyze the feasibility of a new energy supply system. So, the impacts of the optimization results on the existing heating network are considered. The network is inspected on critical points like low mass flows and high heating losses