CACTUS: Advanced diagnostics for photovoltaic reliability and resilience
The European CACTUS project, coordinated by CEA at INES, concluded in June 2026 after two years of collaboration. It developed advanced diagnostic tools, reference datasets, and methods to assess the performance, durability, and resilience of photovoltaic systems. A key outcome involves the combined use of X-ray Beam Induced Current mapping, Bragg diffraction imaging, X-ray micro-tomography, and neutron reflectometry to detect forms of degradation invisible to conventional electrical diagnostics.
The massive deployment of photovoltaics raises a central question: how can module performance be guaranteed over several decades across widely varying climatic environments? The European CACTUS project, coordinated by CEA at INES, sought to answer this question. Concluding in June 2026, the project leaves behind a significant scientific legacy: advanced diagnostic methods, reference datasets, and recommendations for enhancing the bankability of solar technologies.
Photovoltaic panel degradation is often localized, occurs early on, and depends on environmental factors. Temperature, humidity, UV radiation, dust, thermal cycling, or extreme weather events can cause micro-cracks, loss of passivation, encapsulation defects, or ion migration. Conventional electrical diagnostics provide a useful—though sometimes insufficient—overview: they measure overall performance loss without always identifying the physical cause or the precise location of the defect.
CACTUS leveraged large-scale research infrastructures such as the European Synchrotron Radiation Facility and the Institut Laue-Langevin. The work combined several techniques: X-ray Beam Induced Current mapping to link physical defects with local electrical response; Bragg diffraction imaging to observe crystalline stress and deformation; X-ray micro-tomography to visualize the internal structure of encapsulated modules; and neutron reflectometry to analyze fine interfaces within the materials. The aim is to reveal degradation phenomena that are invisible to standard tools.
The project also compiled multi-site outdoor monitoring datasets covering desert, tropical, alpine, coastal, and temperate climates. These data are essential for evaluating algorithms for diagnostics, performance monitoring, and predictive maintenance. In photovoltaics, model quality depends directly on the variety of observed conditions; an algorithm trained in a temperate climate may fail in desert or tropical environments.
CACTUS is of interest to industry stakeholders because it links materials science, operational data, and financial decisions. A better understanding of aging mechanisms enables improved warranties, optimized maintenance plans, and reduced risk as perceived by financiers. Reliability thus becomes a driver of technological competitiveness, rather than merely a quality indicator.
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