Quantifying and aggregating the flexibility of building energy systems
Aachen / E.ON Energy Research Center, RWTH Aachen University (2018) [Book, Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (xxxiv, 198 Seiten) : Diagramme
A growing share of renewable energy systems was installed in Germany in recent years. This trend is meant to be continued in the following years. With the introduction of weather-dependent energy systems like photovoltaics and wind energy systems, the intermittency in the electrical energy system increases. This intermittency needs to be balanced on the national energy system level as well as the local electrical grid level using flexibility options. As flexibility options, different alternatives are possible. Numerous options have the potential to serve as flexibility measures. One of these options are buildings, as the building sector is one of the biggest energy consumers in Germany. Here, especially heat pump and combined heat and power systems in combination with thermal energy storages are a viable option. In this thesis, a generic quantification method for the operational flexibility of heat pumps and combined heat and power plants is developed. This includes flexibility indicators for power and energy flexibility as well as the corresponding flexibility losses. Most of the characterized flexibility indicators are time-dependent and vary around the year depending on different outdoor conditions. For the purpose of operational flexibility quantification of single buildings, suitable building performance simulation models are used. As single buildings do not have noticeable capacities for generation/consumption, the methodology is designed to easily aggregate the flexibility of single flexibility options. This includes the combination of flexibility provided by building energy systems and e.g. batteries or conventional power plants. An extensive simulation study is performed to evaluate the influencing parameters on different flexibility indicators for heat pump and combined heat and power systems. As parameters, the capacity of the heat generators as well as the volume of the thermal energy storage are found to be important. In addition, parameters like the share of domestic hot water consumption at the total heat demand, the thermal energy storage losses or the minimum supply temperature of the building energy system influence power and energy flexibility indicators. The flexibility of different building and plant size setups can easily be compared due to the dimensionless characterization of the single flexibility indicators. Besides the technical evaluation of flexibility options (especially building energy systems), this thesis presents an approach for the economical comparison of different flexibility options. Here, the restrictions of a certain flexibility demand and times to recover storage capacities are important. The economical comparison is applied to different scenarios. Firstly, an aggregation of flexibility options on the national energy system level is performed. Within this analysis, the share of renewable energy sources and the amount of potential flexibility options from building energy systems is varied. Additionally, the influence of different assumptions concerning investment in flexibility options is analyzed. Secondly, the flexibility provision in a local electrical grid is analyzed. Here, the investments for the different flexibility options are varied to analyze their influence on the optimal portfolio. As a result, different portfolios of optimal flexibility options are calculated. In all scenarios, building energy systems are a part of the optimal solution. Nonetheless, other flexibility options like batteries, conventional power plants and curtailment are necessary.