Twinsolar

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Bibliothèque des publications

Journal articles

M., David, J., Alonso-Montesinos, J., Le Gal La Salle, P., Lauret (2023). Probabilistic Solar Forecasts as a Binary Event Using a Sky Camera. Energies, 16, 7125. https://doi.org/10.3390/en16207125

Abstract

Avec l’augmentation rapide des énergies solaires, une prévision à court terme de haute qualité est nécessaire pour intégrer en douceur leur production dans les réseaux électriques. Habituellement, les systèmes de prévision prédisent l’énergie solaire future sous la forme d’une variable continue. Mais pour des applications particulières, telles que les centrales à concentration équipées de dispositifs de suivi de la course du soleil, l'exploitant doit anticiper l'atteinte d'un seuil de rayonnement solaire pour démarrer ou arrêter son système. Dans ce cas, les prévisions binaires sont plus pertinentes. De plus, même si la plupart des systèmes de prévision sont déterministes, l’approche probabiliste fournit des informations supplémentaires sur leur incertitude inhérente, essentielles à la prise de décision. L'objectif de ce travail est de proposer une méthodologie pour générer des prévisions solaires probabilistes sous forme d'événement binaire pour des horizons à très court terme compris entre 1 et 30 min. Parmi les différentes techniques développées pour prédire le potentiel solaire dans les prochaines minutes, l’imagerie du ciel est l’une des plus prometteuses. Ainsi, nous proposons dans ce travail de combiner un modèle basé sur une caméra du ciel et un modèle de choix discret pour prédire la probabilité d'atteindre un seuil d'irradiation adapté aux exploitants de centrales solaires. Deux modèles paramétriques à choix discrets bien connus, les modèles logit et probit, ainsi qu'une technique d'apprentissage automatique, la forêt aléatoire, ont été testés pour post-traiter la prévision déterministe issues des images du ciel. Les trois modèles améliorent considérablement la qualité de la prévision déterministe originale. Cependant, la forêt aléatoire donne les meilleurs résultats et fournit surtout des prévisions probabilistes fiables.

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P., Lauret, R., Alonso-Suárez, R., Amaro E Silva, J., Boland, M., David, W., Herzberg, J., Le Gall La Salle, E., Lorenz, L., Visser, W., Van Sark, W., & T, Zech (2024). The added value of combining solar irradiance data and forecasts: A probabilistic benchmarking exercise. Renewable Energy, 237, 121574. https://doi.org/10.1016/j.renene.2024.121574

Abstract

Despite the growing awareness in academia and industry of the importance of solar probabilistic forecasting for further enhancing the integration of variable photovoltaic power generation into electrical power grids, there is still no benchmark study comparing a wide range of solar probabilistic methods across various local climates. Having identified this research gap, experts involved in the activities of IEA PVPS T16 agreed to establish a benchmarking exercise to evaluate the quality of intra-hour and intra-day probabilistic irradiance forecasts.

The tested forecasting methodologies are based on different input data including ground measurements, satellite-based forecasts and Numerical Weather Predictions (NWP), and different statistical methods are employed to generate probabilistic forecasts from these. The exercise highlights different forecast quality depending on the method used, and more importantly, on the input data fed into the models.

In particular, the benchmarking procedure reveals that the association of a point forecast that blends ground, satellite and NWP data with a statistical technique generates high-quality probabilistic forecasts. Therefore, in a subsequent step, an additional investigation was conducted to assess the added value of such a blended point forecast on forecast quality. Three new statistical methods were implemented using the blended point forecast as input.

To ensure a fair evaluation of the different methods, we calculate a skill score that measures the performance of the proposed model relative to that of a trivial baseline model. The closer the skill score is to 100%, the more efficient the method is. Overall, skill scores of methods that use the blended point forecast ranges from 42% to 46% for the intra-hour scenario and 27% to 32% for the intra-day scenario. Conversely, methods that do not use the blended point forecast exhibit skill scores ranging from 33% to 43% for intra-hour forecasts and 8% to 16% for intra-day forecasts.
 
These results suggest that using (a) blended point forecasts that optimally combine different sources of input data and (b) a post-processing with a statistical method to produce the quantile forecasts is an effective and consistent way to generate high-quality intra-hour or intra-day probabilistic forecasts.
 

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T. A., Randrianantenaina, J. Le Gal La Salle, S. V., Spataru, & M., David, M. (2025). Increasing the self-sufficiency of a university campus by expanding the PV capacity while minimizing the energy cost. EPJ Photovoltaics, 16, 7. https://doi.org/10.1051/epjpv/2024048

Abstract

Microgrids, which promote the production and consumption of renewable energy on site, are a relevant solution to reduce carbon emissions and the price of energy for end users. However, converting an existing building stock into a microgrid powered mainly by renewable energy requires finding a technical and economic optimum while taking into account strong constraints. This work proposes a methodology to achieve this objective on an existing university campus located in La Reunion, a French island in the Indian Ocean. The campus already has three photovoltaic (PV) systems and high-quality measurement data of weather, loads and energy production. The goal of the work is to find an optimal rooftop PV capacity that maximizes campus selfsufficiency while keeping energy price affordable for users. The results do not highlight a unique combination of roofs as a solution to the optimization problem. However, the analysis of possible combinations gives clear rules for defining the total photovoltaic capacity to be installed and selecting the most suitable roofs.

 

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Conferences

M., David, M.N.  Andriamandroso, M. N., P., Behrensdorff Poulsen, J., Castaing-Lasvignottes, N., Cutululis, K., Das, C., Durif-Aboukali, J., Francou, P., Lauret, J., Le Gal La Salle, E., Lorenz, O., Marc, D., Melgar and S., Spataru (2023). A set of study cases for the massive integration of solar renewables in non-interconnected areas. SWC 2023: ISES Solar World Congress 2023, New-Delhi, 30 Oct. – 4 Nov. https://doi.org/10.18086/swc.2023.05.02

Abstract

The massive integration of solar renewable energies is challenging in non-interconnected areas such as remote islands or isolated regions. Indeed, their power grid, which cannot rely on the support of larger electricity networks, is more vulnerable to the inherent variability of the solar resource and grid failures, such as sudden breakdown of production units or transmission lines. The TwInSolar project, funded by the European Commission, aims to provide support and solutions to overcome the problems faced by island territories not connected to continental electricity grids. As a part of this project, four study cases are presented to the scientific community, each highlighting specific issues observed at different scales on the island of La Reunion. This article aims to provide a detailed description of the four selected systems, the corresponding challenges, and the data available.
 

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E., Lorenz, T., Zech, W., Herzberg, P., Lauret, M., David (2024). Probabilistische Kurzfristvorhersage der Globalstrahlung mittels Analog Ensemble unter Nutzung von satellitenbasierter Einstrahlung. Fachtagung Energiemeteorologie, Bad Staffelstein, Germany, 24 Jan..

Abstract

At the German Energy Meteorology Conference in January 2024 Fraunhofer ISE presented on “Probabilistic short-term prediction of global radiation using analog ensembles and satellite-based irradiation” along with an evaluation of these forecasts in a probabilistic benchmark of intra-hour irradiance forecasting, a joint work with University of La Reunion. UR was leading the benchmarking exercise that was carried out in the framework of the IEA PVPS Task 16 “Solar Resource for High Penetration and Large Scale Applications” and received funding from the TwInSolar project. Warning: The presentation is written in German.
 

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J., Le Gal La Salle, M., David, P., Lauret (2024). Finding the Optimal Size and Design of a Microgrid Energy System Using Genetic Algorithm. EU PVSEC 2024, Vienna, Austria, 23-27  Sept. 2024.

Abstract

The laboratory PIMENT leads the Horizon European project “TwInSolar”, aiming to propose cost-effective technical solutions for establishing an electrical microgrid on the Terre Sainte campus, in the island of La Reunion. The primary goal is to maximize self-sufficiency of the microgrid, while ensuring the cost-effectiveness of the system. In order to achieve this multi-objective optimization, the laboratory PIMENT has developed a decision-making support tool called ERMESS, that uses genetic algorithm approach. ERMESS determines the optimal technical design of a microgrid based on meteorological data, existing assets, grid connection, and availability for new installations. The tool, initially created for TwInSolar, is now poised to become a standalone software, serving as an open-access decision-making tool for microgrid designers. As a first step, the promising results concerning the campus of Terre Sainte need to be consolidated, compared with those of already comparable existing tools and reviewed.
 

Best poster award

 

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T. A., Randrianantenaina, J., Le Gal La Salle, S. V., Spataru, M., David (2024). Increasing the self-sufficiency of the Terre Sainte campus microgrid by expanding the PV capacity while minimizing the cost. EU PVSEC 2024, Vienna, Austria, 23-27  Sept. 2024.

Abstract

This work is dedicated to enhance the self-sufficiency of the the Terre Sainte campus of the University of La Reunion with onsite solar energy production. The main goal is to boost energy production by integrating additional photovoltaic (PV) panels while minimizing the installation and operation costs. To navigate toward this objective, four distinct tasks have been outlined. The first focus of the study is on validating the collected data before its application. Five thorough quality check tests have been carefully performed. This work clearly explains the significant importance of each test in ensuring the reliability of the dataset. Moving forward, the study dives into the simulation of the current microgrid PV systems, drawing comparisons with recorded data to assess the accurracy and reliability of the model. This step is important in establishing the performance of the simulation tool and its alignment with actual observations. In the next step, the research work provides a comprehensive exploration of the available rooftop areas on the campus, strategically identifying potential expanses for the scaling up of the microgrid PV capacity. By analyzing these available areas, the study lays the foundation for informed decision-making in the pursuit of an optimized and efficient solar energy system. Finally, using the results of the previous tasks, this study focuses on minimizing the Levelized Cost of Energy for self-consumption (LCOEsc) while maximizing the self-sufficiency. This strategic approach aims to help identify the optimal combinations of rooftops suitable for installing the additional PV panels.

 
This work was selected for a publication in the Special Issue on “EU PVSEC 2024: State of the Art and Developments in Photovoltaics” of the journal EPJ Photovoltaics
 

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Grondin, E., Grondin, D., Delsaut, M., Tang, C., & Morel, B. (2024, November 13). Inter-comparison and validation against in-situ measurments of satellite estimates of incoming solar radiation at Reunion BSRN site. Southern African Sustainable Energy Conference SASEC 2024, Somerset West, South Africa.

Abstract

In Reunion, where the objective is a 100% renewable electricity mix by 2030, climate variability and complex topography make it difficult to integrate solar energy into the electricity grid. This study aims to compare satellite (SARAH-3) and in-situ (IOS-net) data of global horizontal irradiance (GHI) and direct normal irradiance (DNI). First, the entire methodology was applied to the Reunion BSRN site, then extended to all stations in the IOS-net network. The BSRN site was selected for its different sensors, which measure the three components of solar radiation using SPN1 pyranometers (GHI and diffuse horizontal irradiance, DHI) and CHP1 pyrheliometers (DNI). The BSRN site serves as a reference to assess the accuracy of the SARAH-3 satellite estimates for other IOS-net stations, which are only equipped with SPN1 sensors. This comparison allows us to assess the reliability of satellite data because in-situ data are very accurate but often incomplete. In contrast, satellite data are more systematically available but less accurate due to their dependence on estimation models and a lower spatial and temporal resolution. The study covers data from December 1, 2008 to April 1, 2024, focusing on DNI (2017-2024) for concentrated solar systems and GHI (2008-2024) for PV systems. In-situ data from Reunion are imported from IOS-net, quality-checked according to BSRN criteria, and matched with corresponding satellite data. High-quality measurements, at oneminute resolution, collected since 2008 are used to establish correlations between ground-based and satellite data, potentially filling data gaps and improving solar irradiance predictions. This approach could help estimate GHI and DNI in areas without meteorological stations, thereby identifying new regions with high solar potential.
 

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