Optimal design and operation of a CHP based district heating system including a heat storage and electrode boiler to increase self-consumption

Energy systems with a high share of renewable energy sources (RES) require a large degree of flexibility due to the inherent volatility of wind and photovoltaic based power generation. Here, cross-sector coupling of the power and district heating system can add such flexibility and increase the self-consumption of RES. To couple these two systems, components such as electric boilers, heat storages and combined heat and power (CHP) systems must be optimally sized. Existing optimization algorithms mostly size the components based on volatile energy prices. In contrast, this paper investigates the sizing based on the reduction of network charges for different degrees of self-consumption in two future RES scenarios. For that, the operating mode of an existing CHP system is changed to "power-led" by introducing a hot water storage and an electrode boiler. The optimization determines the best design of the hot water storage and electrode boiler for a district of a town in Germany. It is shown, that such a system can add flexibility to a micro grid and increase the degree of self-consumption while reducing the network charges and thus being economical up to 60 % of self-consumption.