Metrology to Support the Optimisation of Large-Scale Efficient Dependable Photovoltaic Systems

To support investment decisions and optimize the construction of PV power plants, the solar industry relies on real-world performance and environmental data. However, the reliability of these data is limited by a lack of understanding and insufficient quantification of associated measurement uncertainties. This project quantifies and reduces uncertainties related to PV plant performance data and provides the necessary metrological tools. The goal is to enable harmonization, traceability, and continuous improvement of collected data. The project delivers European-level standards, performance metrics, best practices, calibration capacities, and research infrastructure to ensure the quality of PV plants and technologies. All of this will support the solar industry and secure its business valued at an estimated €100 billion.

Initial Situation

PV plants are complex systems composed of active components (PV modules, inverters, transformers), passive components (cabling, fuses), structures (mounting systems, tracking systems), and monitoring devices. They are hierarchically organized (e.g., 72 cells per module, 24 modules per string, 8 strings per inverter, multiple inverters per grid connection). System sizes in Europe range from small rooftop installations on residential buildings to utility-scale plants with up to 200,000 modules. System performance depends on component interactions. Previous projects developed advanced measurement and calibration capabilities at the cell and module levels, but gaps remain at the system level – addressing these promises further efficiency gains.

Objective

The project aims to identify, quantify, and reduce uncertainties related to key performance indicators (Performance Ratio (PR) and Performance Loss Rate (PLR)) of PV plants and provide tools for their implementation and continuous improvement beyond the project duration.

Developed Outputs:

• A specification for classification and SI-traceable calibration of reference devices
• Models for propagating measurement uncertainties to performance indicators
• Harmonized methods for determining PLR, including uncertainty budgets, supported by on-site measurements and tests (IV curves, electroluminescence)
• Reference PV plants with validated digital twins and publicly accessible time-series data, alongside measures for adoption by the measurement supply chain, standardization bodies, and end users

Approach

Fraunhofer ISE contributes to modeling the propagation of measurement uncertainties from sensors to performance indicators (PR, PLR) and develops guidelines for accurate, cost-efficient monitoring through optimized sensor selection and placement. Additionally, Fraunhofer ISE is involved in creating methods and sampling strategies for determining PLR over time by quantifying system degradation rates. By combining system-level monitoring data with field characterization and testing of modules, uncertainty budgets for PLR determination are derived. We record TMon sub-processes, derive requirements and develop a standardised knowledge graph model that describes systems, sensors, control systems and energy and hydraulic connections. To this end, we are expanding the TBSys ontology developed at Fraunhofer ISE, which is based on Standard 223P and Brick Schema. Building on this, we are creating a plant database with templates, test variables and control sets, as well as a data structure for digital mobile measurement tasks. An AI pipeline combines text recognition using generative AI with time series classification and symbolic AI for data point and topology recognition. The components will be integrated into the monitoring platform of project partner Mondas. The methods will be demonstrated and validated on demonstrators in real monitoring projects.

• The National Physical Laboratory (NPL)
• Aalto (Metrology Research Institute)
• Czech Meterology Institute (CMI)
• Central Office of Measures (GUM)
• Laboratoire National de Métrologie et d'Essais (LNE)
• Physikalisch-Technische Bundesanstalt (PTB)
• Research Institutes of Sweden (RISE)
• Türkiye Bilimsel ve Teknolojik Araştırma Kurumu (TUBITAK)
• University Ljubljana (UL)
• Austrian Institute of Technology – AIT
• Centro Nacional de Energías Renovables (CENER)
• Certisolis
• Centro Tecnológico (CIRCE)
• Institute for Energy Technology (IFE)
• Interuniversity Microelectronics Centre (IMEC)
• Institut für Solarenergieforschung Hameln (ISFH)
• Loughborough University (LU)
• Photovoltaic Performance Labs (PVPL)
• Schweizerisches Forschungsinstitut für Hochgebirgsklima und Medizin in Davos (SFI)
• University of Applied Sciences and Arts of Southern Switzerland (SUPSI)

The “SOLiD-PV” project is funded by the European Union and by the European Association of National Metrology Institutes (EURAMET).