TACOS-PV: Temperature Analysis and Characterisation in Operational Solar PhotoVoltaics

Context: Understanding and mitigating temperature-related losses in solar photovoltaic (PV) systems is critical for deploying resilient and reliable PV systems, as well as increasing investor and public confidence in renewable energy. Since temperature is the most significant performance factor after irradiance, it can dramatically influence PV system efficiency and power output. Knowing how energy yield depends on temperature is vital in material selection and system design, particularly in new high-efficiency PV technologies in extreme climates. Temperature effects can accelerate degradation, impacting solar module reliability and system performance ratio. Accurate knowledge of temperature coefficients of PV products is critical for accurate prediction of losses, ensuring return of investment and fair contracts in the PV systems sector. It allows the selection of the right products based on geographic and climatic conditions, and is crucial in financial modelling, impacting investment returns and payback periods of all current and future solar energy technologies. Challenge the project addresses: At present, the temperature dependence of the performance of solar modules is calculated by empirical parametrisations in one-diode circuit models. While such an approach is reasonable for low-efficiency, traditional silicon cells, the recent development of high efficiency single (>26%) and tandem junction (>33%) devices desperately requires an improved understanding of temperature effects. For example, recent world-record silicon cells exhibit minimal extrinsic losses, limiting them primarily by intrinsic physical mechanisms. Despite decades of research, the temperature dependence of intrinsic recombination in silicon is still not well understood, measured or modelled. Design and management of solar plants urgently require improved temperature-dependent models to deliver the accuracy and confidence needed for efficient power generation planning, grid management and return of investments. Aims and objectives: This project aims to produce a step change in the knowledge, understanding, and modelling of the temperature dependence of solar PV modules and systems under operation. This is an ambitious multidisciplinary challenge originating in the fundamental physics of semiconductors and extending all the way to the solar cell design, module operation conditions, and PV system performance assessment. It encompasses accurate characterisation of solar materials, devices and modules, physical and empirical modelling and large-scale system modelling. In particular, the temperature dependence and temperature coefficients of materials and high efficiency PV structures will be determined, producing new datasets that will be necessary for faster adoption of these technologies. Based on material and cell temperature dependence knowledge, the effects of temperature will be determined in the field for PV modules, through outdoor testing and the adoption of novel temperature measurement techniques such as phosphor thermometry. Applications and benefits: The above information will be used to improve current temperature models, especially heat transfer and temperature translation models from ambient to junction temperature of PV modules under operation. This new knowledge will be directly applied at a PV system level, to improve current design software packages, reduce uncertainties of PV system performance assessment, and deliver a global map of temperature losses impact for systems. The outcome of the above activities will be new models and datasets for temperature influences of PV materials, cells ad modules, and new standards for performance assessment and modelling of PV systems. This will result in increased confidence in new high efficiency PV technologies, reduced risks in PV system development and hence higher efficiency and resilience of PV systems.