T. Tjaden

Economics of Residential PV Battery Systems in the Self-Consumption Age

This paper investigates the profitability of PV battery systems that aim to reduce the electricity purchased from the grid of households. The economic feasibility is assessed based on the approach of calculating the mean electricity cost of the household equipped with a PV battery system. The study focuses on the main question: What is the break-even point of the battery system price at which residential PV battery systems become economically viable in Germany? This is analyzed by determining the limit of profitability in terms of required battery system price, which makes the investment in a PV battery system under given circumstances profitable. The impact of different economic input parameters on the required battery system price was studied for a defined reference case. The results reveal that the major factor is the interest rate, followed by the PV system price, retail electricity price and feed-in tariff. Nevertheless, several uncertainties with regard to the economic assessment exist. However, assuming that the calculated required battery prices will be achieved in the future; investing in a PV battery system is financially more attractive than purchasing the entire electricity demand from the grid.

Feed-in Power Limitation of Grid-Connected PV Battery Systems with Autonomous Forecast-Based Operation Strategies

Considering the challenges of grid integration, battery systems could be used to smooth the infeed of PV systems. This paper presents autonomous forecast-based operation strategies for residential PV battery systems that can be used to improve grid integration of PV systems. Simulation calculations on a timescale of one minute were performed to determine the impact of error-prone forecasts of the PV generation and load demand. Like load forecasts which need to be calculated on-site, also PV forecasts can be autonomously derived from measurements to avoid costs from forecast services. For the purpose of dealing with forecast errors a model predictive controller is implemented which can compensate the essential undesired effects of forecast errors. In this paper basic forecast approaches were assessed to show that even simple prediction models result in an economic feasible and autonomous grid relieving operation of residential PV battery systems.