EDF Renouvelables

Abstract The authors report on the light‐ and elevated temperature‐induced degradation (LeTID) effect observed on bifacial photovoltaic modules and its potential impact on photovoltaic plants performance. Indoor LeTID quantification using indoor carrier‐induced degradation (CID) is carried out using current injection. Power measurements yielded higher LeTID sensitivity for the rear side of bifacial modules compared to the front side, hence leading to a variation of the bifaciality factor by several percentage points. The difficulty in evaluating the maximal power degradation caused by LeTID is also highlighted as a reduced number of samples are used most of the time and as cells within a single module do not have always the same performance evolution trends. Using indoor CID results with the help of empirical fitting and Arrhenius relation, the yield impact of LeTID on a bifacial power plant is simulated under three different climates. Modeling results help to identify the main parameters related to LeTID modules sensitivity that impact photovoltaic (PV) plants yield: maximal power degradation, stabilized power value after regeneration, activation energy value, and LeTID kinetics. In some cases, the yield variation caused by LeTID sensitive modules could be mitigated by carefully selecting the modules as a function of climatic conditions.

International audience

International audience

La plupart des éoliennes offshore sont fondées sur monopieux. L’augmentation constante de la capacité des turbines et l’insuffisance des procédures évoquées dans les documents normatifs, notamment en ce qui concerne la prise en compte des chargements cycliques, posent des défis pour leur dimensionnement. Dans le cas des sites français, la présence de sols et roches carbonatés, dont le comportement est encore mal connu aujourd’hui, rend la tâche encore plus complexe. Le projet SOLCYP+, lancé en 2017 pour une durée de 3 ans, doit permettre de disposer de nouvelles méthodologies fiables et robustes pour le dimensionnement des monopieux de grand diamètre y compris dans le contexte géotechnique du plateau continental français. Cet article présente une description détaillée du projet ANR SOLCYP+. On aborde, tout d’abord, le contexte, la problématique et les objectifs du projet puis, dans un second temps, on décrit plus en détail les quatre principales tâches scientifiques.

This research focuses on the reliability and durability of polyolefin in double glass photovoltaic (PV) modules, which is popular among PV maunfactures. We investigate three predominant failure modes, discoloration, delamination, and PID, of polyolefin under various stresses close to outdoor environment conditions and propose service lifetime prediction based on data-driven degradation models. In this paper, the transmittance of 6 types of laminated commercial polyolefin with exposure to UV and moisture at elevated temperatures are measured. Polyolefin demonstrates good optical durability, some even better compared to EVA. We show that measured decrease in transmittance translates into a two-step decay for short-circuit current of PV (Isc) module. The Isc degradation can be well fitted by models of exponential decay and piecewise linear decrease. The latter has fit parameters with physical meanings and is thus preferred. To correlate Isc results of different aging tests with field performance, modified Arrhenius equation considering the impact of UVB irradiance and temperature is used. The Isc decreases of PV modules caused by discoloration of 2 types of polyolefin in Miami are estimated, ~3.6% and ~1.3% respectively for 30 years.

The design of monopiles foundation for Offshore Wind Farms requires the characterisation of the rigidity between the<br> soil and the shaft of the pile. While soil investigation methods are normally used, return of experience with measured<br> data is rarely available. This paper presents a series of simple dynamic tests, performed on two 1:6 scaled monopiles<br> foundation installed in rock as part of a lateral pile test campaign. Results of the dynamic tests can be compared with<br> the theoretical fixed beam using frequency, damping and modal shape parameters with the aim of assessing to rigidity<br> of the soil-structure interaction. The tests were carried out onshore France in 2016 by FUGRO and EDF-RE for offshore<br> wind farms development projects as an add-on to a large-scale pile testing program. Two foundation piles of 1.2 m<br> diameter, partially installed into Calcarenite, received a range of lateral dynamic strokes. The dynamic response of each<br> pile was recorded at high frequency by accelerometers installed along the stick-up length of piles. The results were<br> analysed to identify the lowest resonant frequency and subsequent vibration patterns. In addition, logarithmic<br> decrement analyses and modal deformation analyses were performed to better understand the piles dynamic response.<br> Comparing those results to the theoretical values of a fixed beam provides valuable information and help to assess the<br> as-built connection between the rock and the piles. Such information can be used at design stage to quantify the rigidity<br> of interaction between the soil and the pile. It can also be used during the lifetime of the foundation to monitor the time<br> evolution of this connexion.

International audience

Foundations contribute to around 30% of offshore wind capital expenditure. Due to significant uncertainties in soil properties, it is important for wind farm development to evaluate the propagation of those uncertainties through various design criteria. In the early design stages, data availability is scarce. As the project advances, geotechnical campaigns are performed, increasing the ground knowledge and reducing the overall uncertainty. The objective of this article is to provide a methodology to quantify the impact of uncertain soil properties on geotechnical design criteria for offshore monopile foundations. The approach proposed in this article is based on metamodels, allowing identification of predominant soil parameters and possible correlations between soil properties inputs and foundation outputs. The geotechnical criterion used in this paper is the critical pile length.

This Work Deals with the Robustness of Transparent Backsheet Modules using Coating/PET/PVF (TPC) Polymer Layers when Exposed to an Extended Potential Induced Degradation (PID) Stress based on IEC 61215. Results show a Significant Power Decrease on the Front Side after 576h of Testing for Negative Voltage with Three Time more Impact at the Rear Side Despite the Absence of Glass. PID is Confirmed with Electroluminescence (EL) and Photoluminescence (PL). Measurements Showing the Appearance of Dark Areas on Several Cells and an Inhomogeneous Signal all Along the Module with “Light trails”. Moreover, Transmission Electron Microscopy Measurement Points out Sodium Presence at Both Cell Interface Despite POE Encapsulant and the Absence of Glass at the Rear Side. Two Types of PID Seem to be Present: Low Light Current-Voltage Measurements Suggest the Presence of PID-Potential at the Rear Side of the Cells And the Dark Area Could Be linked To PID-Corrosion Effect as Depassivation is observed with EL and PL.

The PIBE project is the first French collaborative research project on wind turbine noise. One of its objectives is to quantify the experimental dispersion observed in situ on acoustic quantities/metrics and influencing parameters, and to compare it with the numerical dispersion estimated using acoustic propagation models. A long-term experimental campaign was carried out over consecutive 410 days around a wind farm comprising eight 80-metre-high and 90-metre diameter turbines. Acoustic sensors (five Class I sound level meters) were deployed on site, recording third-octave spectra and overall A- and Z-weighted values of the Leq indicator and fractile indices (L10, L50 and L90), at distances from 325 m to 1400 m from the wind turbines row. In addition, three 3D ultrasonic anemometers and a Lidar system were used to measure meteorological variables influencing long-range sound propagation (e.g. wind and temperature verical profiles). Besides, train and aircraft passing close to the site were inventoried to identify periods of high background noise. All experimental data have been processed into an ElasticSearch database. An interactive web application has been developed in R Shiny to facilitate processing, visualization and analysis of the experimental database.

The PIBE project aims to improve wind turbine noise prediction methods and to explore new solutions for noise reduction. This five years project brought together French experts in aeroacoustics, sound propagation, experimental noise characterization and wind engineering, and was structured around three work packages. The first one aimed to study amplitude modulation phenomena and focused particularly the characterization of dynamic stall noise. Specific aerodynamic and acoustic measurements were carried out in a wind tunnel, showing the influence of several stall regimes on noise production. The second work package focused on quantifying the uncertainties of noise prediction methods. It developed an open-access online application (WindTUNE) that quantifies uncertainties on noise prediction of a wind farm, and a parametric and uncertainties calculation tool for the engineering application Code-TYMPAN. This axe also produced an open-access database of a 400 days campaign of meteorological and acoustical measurements around a wind farm. The last work package investigated new noise reduction devices using blades with modified leading and/or trailing edges. The efficiency of the solutions were characterized in a wind tunnel, both acoustically and aerodynamically. The paper presents the main results obtained at the end of the project.

Wind Turbine Noise (WTN) variability is often related to the influence of local micrometeorology as well as to space and time variations in the ground properties. Thus, the PIBE Project (2020-2024) aims to estimate these variabilities and their associated uncertainties. Its objective is to enable engineering companies or wind farm developers to estimate more accurately the risk of noise. In the WP2 of the PIBE project, 3 approaches are explored: (i) a NUMerical approach through the development of a metamodel, (ii) an EXPerimental approach through a major in-situ measurement campaign lasting more than 1 year, and (iii) a STATistical approach consisting in the evaluation of WTN variability. The NUM approach consists in sound emission calculation of each wind turbine using the Amiet's theory, and sound propagation calculation using a wide-angle Parabolic Equation (WAPE) modelling. The EXP part of the PIBE project has led to the development of a large database, accessible via a dedicated Shiny application. The last approach (STAT) has been carried out using both an open-access online tool called WindTUNE and an open-source tool based on Code_TYMPANTM, namely OCP. The 3 approaches (NUM + EXP + STAT) are presented and the corresponding results are discussed.