Photovoltaic modules are exposed to a variety of climatic loads during outdoor operation. Over time, these loads trigger a number of degradation modes within the modules leading to performance loss. This paper quantifies the impact of combined climatic loads on the module's maximum power output using a mathematical approach. Three degradation precursor reactions, namely, hydrolysis, photodegradation, and thermomechanical degradation, are assumed to be necessary for service lifetime prediction. For each reaction, an empirical kinetics model is proposed and validated with indoor test measurements. A generalized model to quantify the effects of combined climatic loads is proposed. The generalized model is calibrated and validated using outdoor test measurements. The model is then applied to predict the annual degradation rates and a 20% performance loss of three identical monocrystalline modules installed in three benchmarking climates: maritime (Gran Canaria, Spain), arid (Negev, Israel), and alpine (Zugspitze, Germany) using real monitored meteorological data. A degradation of 0.74%/year corresponding to 21.4 years operation time was predicted as the highest for an arid environment, compared with 0.50%/year and 0.3%/year degradation for maritime and alpine environments, respectively. The proposed models will find applications in outdoor predictions as well as in the combined stress accelerated tests to develop test designs.

Photovoltaic (PV) systems are the cheapest source of electricity in sunny locations and nearly all European countries. However, the fast deployment of PV systems around the world is bringing uncertainty to the PV community in terms of the reliability and long-term performance of PV modules under different climatic stresses, such as irradiation, temperature changes, and humidity. Methodologies and models to estimate the annual degradation rates of PV modules have been studied in the past, yet, an evaluation of the issue at global scale has not been addressed so far. Hereby, we process the ERA5 climate re-analysis dataset to extract and model the climatic stresses necessary for the calculation of degradation rates. These stresses are then applied to evaluate three degradation mechanisms (hydrolysis-degradation, thermomechanical-degradation, and photo- degradation) and the total degradation rate of PV modules due to the combination of temperature, humidity, and ultraviolet irradiation. Further on, spatial distribution of the degradation rates worldwide is computed and discussed proving direct correlation with the Köppen-Geiger-Photovoltaic climate zones, showing that the typical value considered for the degradation rate on PV design and manufacturer warranties (i.e., 0.5%/a) can vary ± 0.3%/a in the temperate zones of Europe and rise up to 1.5%/a globally. The mapping of degradation mechanisms and total degradation rates is provided for a monocrystalline silicon PV module. Additionally, we analyze the temporal evolution of degradation rates, where a global degradation rate is introduced and its dependence on global ambient temperature demonstrated. Finally, the categorization of degradation rates is made for Europe and worldwide to facilitate the understanding of the climatic stresses.

The ever‐growing secondary market of photovoltaic (PV) systems (i.e., the transaction of solar plants ownership) calls for reliable and high‐quality long‐term PV degradation forecasts to mitigate the financial risks. However, when long‐term PV performance degradation forecasts are required after a short time with limited degradation history, the existing physical and data‐driven methods often provide unrealistic degradation scenarios. Therefore, we present a new data‐driven method to forecast PV lifetime after a small performance degradation of only 3%. To achieve an accurate and reliable forecast, the developed method addresses the fundamental challenges that usually affect long‐term degradation evaluation such as data treatment, choosing a good degradation model, and understanding the different degradation patterns. In the paper, we propose and describe an algorithm for degradation trend evaluation, a new concept of multiple “time‐ and degradation pattern‐dependent” degradation factors. The proposed method has been calibrated and validated using different PV modules and systems data of 5 to 35 years of field exposure. The model has been benchmarked against existing statistical models evaluating 11 experimental PV systems with different technologies. The key advantage of our model over statistical ones is the ability to perform more reliable forecasts with limited degradation history. With an average relative uncertainty of 7.0%, our model is outstanding in consistency for different forecasting time horizons. Moreover, the model is applicable to all PV technologies. The proposed method will aid in making reliable financial decisions and also in adequately planning operation and maintenance activities.

The solar conversion market with photovoltaic (PV) systems has experienced and is experiencing an enormous growth worldwide and—according to the agreed goals of many countries to protect the climate—will further grow over the coming decades. Investments related to PV became an important financial product with the special feature of very long contract durations. A typical setting is an operation of more than 20 years, during which the generation of electricity and also revenues are expected. Sometimes Power Purchase Agreements with durations of up to 50 years have been reported. Taking these long operational times into account, quality, durability, reliability, and degradation rates become a crucial topic for the investment and for all stakeholders. PV modules are the dominating components in this regard since they prevail the investment and—due to their sheer quantity—are in most cases hard to replace if a system has PV module immanent issues. Accelerated ageing tests are in general used to ensure the quality of PV components. These tests are partly standardized, for PV mainly by the International Electrotechnical Commission IEC and related national committees. These standards are used for type approval testing or safety testing, which can also address legal issues. Accelerated ageing tests are also adapted to specific needs and for example used for quality assurance (QA) of manufacturers or service life prediction (SLP) by manufacturers or research institutes. All the efforts are taken to gain more knowledge about the behavior of PV modules in operation and thus the accelerated tests have to be related to normal operation. Since PV is used around the globe, the conditions vary significantly depending on the location of installation, from dry and sunny deserts to mountain climates to tropical or maritime climates. In addition, the type of installation has severe influence on the operational conditions of PV modules i.e. mounted on a roof, roof integrated, open rack—or even in upcoming applications like floating PV. The papers attempt is to give an overview on the state of the art of accelerated testing and field performance analysis of PV modules with focus on the developments over the last five to ten years. Developments are described and the status is analyzed regarding the significance of tests including the latest developments and open scientific gaps related to the envisaged correlation of accelerated tests with field performance. In the end the reader is enabled to differentiate between reliability testing and service life prediction. The understanding for a comprehensive approach of reliability testing including field evaluation data will be developed.