The joint research project “Integration of PV storage systems for self‑consumption in the energy industry using innovative measuring systems” was carried out from 1 January 2017 to 31 December 2018 and funded by the German Federal Ministry of Economic Affairs and Energy (BMWi). The consortium comprised the Technical University of Braunschweig (Institute for High‑Voltage Engineering and Electrical Power Systems), EMH Metering GmbH & Co. KG, the Physikalisch‑Technische Bundesanstalt (PTB), and SMA Solar Technology AG. The project’s aim was to develop a measurement and billing concept that allows a photovoltaic (PV) system with battery storage to be used simultaneously by the consumer and by third parties, thereby enabling new market processes while maintaining accurate metering.
The technical work was organised in four phases: requirement profiling, simulation, laboratory testing, and field testing. Requirement profiles and system architectures were defined in workshops and served as a common basis for all subsequent work. Simulations examined operating strategies, business models, and the feasibility of integrating energy meters directly into inverter housings. The laboratory phase demonstrated the feasibility of the proposed measurement concept and produced a mobile reference measurement system for calibration and validation. Field tests were conducted at two research sites to verify the system under real operating conditions.
The core measurement concept uses two electronic energy meters, an external computing unit (RE), and an energy management system (EMS). The EMS calculates virtual metering points every second, enabling simultaneous billing of multiple energy flows. The system is suitable for both AC‑coupled and DC‑coupled PV storage configurations and can be extended to multi‑family buildings. The virtual metering points are generated automatically by the RE based on meter data and the EMS control signal, allowing real‑time billing without the need for a dedicated smart‑meter gateway, which could not be implemented due to regulatory delays and lack of availability.
Performance results show that the EMS must complete its calculations within 500 ms to ensure correct timing of control signals; otherwise, significant errors can occur. The maximum error introduced by asynchronous meter operation is 35 %, but with typical household load curves the error drops below 0.3 %. Synchronising the meters virtually eliminates this error source. The mobile reference system confirmed that all energy flows meet the permissible calibration error of 3.5 % even when considering the maximum possible measurement uncertainty in all operating states.
Economic analyses indicate that the simultaneous use of PV storage does not adversely affect key performance indicators such as self‑consumption and autonomy ratios. The system improves storage utilisation efficiency and allows contractors to achieve higher revenues when offering a bidirectional storage band. The active balance‑of‑system compensation enabled by the virtual metering points offers grid operators a tool to reduce balance‑of‑system deviations and lower regulation energy requirements.
In summary, the project delivered a fully functional, low‑hardware‑overhead measurement and billing system that meets regulatory and technical requirements for multi‑user PV storage. The consortium’s collaborative effort, spanning academic research, industry expertise, and metrological validation, demonstrates a viable pathway for integrating PV storage into the energy market while ensuring accurate, real‑time metering and billing.