Performance Assessment of Residential PV Battery Systems

Presently, more than 120,000 photovoltaic (PV) battery systems are operating in German households. They differ in the coupling between PV and battery, the nominal capacities of their components, and their degree of integration. This thesis develops and evaluates methods for a uniform determination of PV battery system performance. Therefore, major Influences on system performance are analysed and used to derive requirements regarding the test procedures and key performance indicators (KPIs) as final metrics of the system evaluation. Already this requirement analysis reveals that the performance comparison must cover the efficiency and effectiveness during system operation. As the assessment of effectiveness based on application-independent investigations is impossible, an application-oriented evaluation proves to be necessary. Based on these findings, a method that combines an application test of system operation during multiple
days with additional application-independent investigations is proposed. By using the results of the application test, two KPIs are calculated, namely: (i) the efficiency as a classic performance figure and (ii) the effectiveness to evaluate control and energy management of the system. This method is applied to five different devices under test (DUT) and its advantages and drawbacks are discussed. The analysis reveals that the method does sufficiently address all specifications and is beneficial in terms of result comprehensibility and KPI validity.