13Reliability and Performance of PV Systems

Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies

The solar energy industry continues to push the boundaries of efficiency and reliability. However, as innovative photovoltaic (PV) cell and module technologies emerge, they also bring a new set of challenges in durability and performance. A new report titled “Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies,” offers a comprehensive analysis of degradation and failure mechanisms in current photovoltaic (PV) technologies.

Although new technologies bring new challenges, they also lead to positive trends. The report outlines the changes in degradation and failure modes driven by current innovations. The levelized cost of electricity (LCOE) of photovoltaic applications depends on, among other things, the performance, price and durability of the photovoltaic (PV) module. Performance and price can be determined with little effort. Durability is the least known of these three factors. In this report, we evaluate the impact of degradation/failure modes of innovations in the market.

To produce reliable PV modules, all degradation pathways must be understood and mitigated in one solution. There are currently no comprehensive solutions in the literature to address the multiple reliability issues of PSCs. Along with this report Photovoltaic Failure Fact Sheets (PVFS) 2025 are delivered for praxis and field-oriented information for PV planners, installers, investors, inspectors, consultant or insurance companies. The PVFS are available here: Photovoltaic Failure Fact Sheets 2025 – IEA-PVPS

Best Practice Guidelines for the Use of Economic and Technical KPIs

Key Performance Indicators (KPIs) are important metrics used to assess various aspects of photovoltaic (PV) systems, including their long-term performance, economic viability, and carbon footprint. Technical KPIs support data-driven and informed decision-making when optimising PV systems and provide a comprehensive overview of how PV systems operate across different conditions and climates. Different KPIs are commonly employed throughout the entire value chain of PV projects and can be categorised into technical, economic and sustainability aspects. In this work, a set of best practices for handling PV system data to reliably calculate relevant KPIs is discussed. The work is divided into three parts, each addressing different aspects of KPIs, data management, and their mapping potential.

KPIs that are contractually binding carry direct financial implications, while those used in a technical context serve to support the performance assessment of PV plants, and the associated decision-making by stakeholders. The survey showed additionally that while there are certain KPI usage trends per region, a globalised world and market means that there are no strict differences to be seen. Despite the nominal standardisation of contractual KPIs such as the performance ratio and temperature-corrected performance ratio, there are still considerable variations in the data quality routines employed, and consequently, in the calculation of the resulting KPIs.

This report explores key performance indicators in PV systems, focusing on reliable calculation pathways as well as their use to optimise PV performance. Through a review of current best practices and data management techniques, the report highlights the critical role of KPIs in improving PV operations, contractual transparency, and future PV system designs. The report is available here. Technical Key Performance Indicators for Photovoltaic Systems: Challenges and Best Practices – IEA-PVPS.

Performance of Partial Shaded PV Generators Operated by Optimised Power Electronics

Inhomogeneous shading on the PV generator leads to disproportionately high losses. As the potential of PV generation on roofs or façades is to be increasingly utilised in the coming decades, these cases will occur more frequently. The aim here is to provide an overview of the challenges and state-of-the-art technical solutions for partial shading. Current developments in PV engineering show that maximum performance lies in the combination between optimised module placement, the use of modules that are tolerant of shading and optimised power electronics.

Detailed performance analyses have shown that with partially shaded PV generators, conventional string inverters sometimes even achieve better performance in these applications than the market-dominating optimisers. Such meaningful recommendations for high-performance systems can only be made if the realistic losses of the optimisers themselves are considered, which are typically overestimated by 2 %. However, as these annual performance differences between optimizers and string inverters are usually less than 3 % in a market dominated by lightly to moderately shaded PV systems, optimiser manufacturers are obliged to provide realistic efficiency data.

A wide range of additional research work is being carried out to reduce PV shading effects. They range from new variants of sophisticated power electronics for each solar cell, including the control system, to the optimisation of mechanical tracking of single-axis large-scale PV power plants on uneven terrain. The cost-effectiveness for the end customer of PV partial shading can be characterised not only by the higher investment costs for components and installation, but also by the high costs for tradesmen when replacing defective optimisers. When it comes to comparing the probability of failure rates of optimisers due to the higher ambient temperature on the roof compared to string inverters in the building, the experts still must wait for independent studies of service cases during replacement in the field.

This will include degradation modes in recent PV technologies as well as Perovskite-based future technologies’ degradation. We will also analyse strategies about how old or defective PV modules may have a second life. As batteries are an important part in PV systems, we start to assess their reliability.

Task 13 experts will focus on novel PV applications. Emerging PV applications are floating PV and Agrivoltaics. Experts will collaborate on energy yield modelling and specific loss mechanism, field performance, and reliability, as well as operation & maintenance challenges and best practices. A general overview and definitions for these integrated PV applications will be given. PV systems with bifacial modules and trackers have a rising market share, as well as systems with module level power electronics. Task 13 will conduct a global survey of PV-tracking technologies to gather information on their tracking algorithms and how they improve bifacial PV performance and system designs. Best practices on performance evaluation are compared and developed. Module level power electronics in the PV system and specifically the effect of shading conditions on the performance are also investigated. Finally, the role of digitalisation in cost and performance optimisation of PV systems and best practices are addressed by the Task 13.

Task 13 will identify extreme weather events including hurricanes, typhoons, blizzards, dust storms, hailstorms and wildfires that impact PV systems, and assess the losses/damage associated with them. Experts will carry out a survey addressing asset owners and other stakeholders regarding the scope of and types of weather-related PV damage (equipment damage, replacement costs, and production losses). The impact of decisions along the value chain of a PV projects (i.e., during design, procurement, engineering, transport, installation, O&M, end of life) will be visualised to define best practice flowcharts for PV projects and contribute towards reducing the risk of PV investments. Data coming from various plant typology and configurations will be benchmarked in terms of techno-economic KPIs.

• Reliability plays a significant role in new PV technologies, designs and appearances of PV modules, components and systems for future energy markets. PV technologies are changing rapidly as new materials and designs are entering the market. These changes affect the performance, reliability, and lifetime characteristics of modules and systems. Such information about new technology and how these new technologies interact with each other is of great importance to investors, manufacturers, plant owners, and EPCs. These stakeholders are keenly interested in gaining more information about such technological innovations.
• The digitalisation and robotisation of inspection activities in PV plants are becoming fundamental tools for reducing O&M costs, especially for PV operators managing an ever-growing portfolio of plants, often reaching gigawatt size. While modern monitoring systems are already capable of collecting high quality data, current analytical tools need to be further developed to improve O&M activities, including the detection of degradation factors responsible for energy losses.
• The high quality of Task 13 reports and results is the result of the continuous involvement of highly motivated experts in the field. As with the development of long-term databases for degradation and performance analyses, the relationships built up over the past years must be maintained and supported, as the work of this task must have a similar positive dynamic to the current PV market.