Parabolrinnen-Qualitätskontrolle in der Serienfertigung Q-Foto

Mittels photogrammetrischer Methoden lassen sich quantitative Größen für die Qualifizierung der Genauigkeit eines Parabolrinnen-Kollektors schnell und zuverlässig messen. Für eine Serienfertigung der Parabolrinnen wurde eine automatisierte photogrammetrische Messeinrichtung entwickelt. Sie wird in die Kollektorproduktionslinie integriert und ermöglicht es, Montagefehler im Produktionsprozess sofort zu erkennen, um rechtzeitig deren Ursachen zu beseitigen. Der Einsatz eines solchen Systems stellt daher eine sinnvolle Maßnahme zur Dokumentation der Fertigung sowie zur Sicherung des energetischen Ertrags des Solarfeldes und damit des ökonomischen Erfolges eines Kraftwerkprojekts dar

Kombinierte Methode zur Bestimmung der Flussdichteverteilung am Beispiel Solugas

Turmkraftwerke weisen einen hohen Wirkungsgrad und große Kostensenkungs-potenziale auf. Zur Bestimmung der Wirkungsgrade und Eintrittsleistung und zur Optimierung des Betriebs dient die Messung der solaren Flussdichteverteilung in der Ebene der Eintrittsapertur des Receivers. Flussdichtemesssysteme nutzen häufig einen diffus reflektierenden Schwenkbalken, der sich vor dem Receiver vorbeibewegt, während eine CCD-Kamera die Helligkeitsverteilung der am Balken reflektierten solaren Strahlung aufnimmt. Anschließend wird das Bild mit Radio-meterwerten kalibriert. An kommerziellen Turmkraftwerken höherer Leistung und entsprechend größerer Apertur sind mechanische Schwenkbalken sehr groß und daher nur bedingt geeignet. Aus diesem Grund werden Messmethoden untersucht, die ohne Schwenkbalken auskommen [1]. Eine Methode kombiniert eine Raytracing-Simulation mit einer vereinfachten Messung im Bereich des Strahlungsschutzes. Die Messung dient dabei zur Validierung der Simulationen. Aus dem Simulationsergebnis lassen sich dann alle wichtigen Größen zur Charakterisierung des Kraftwerkes ableiten. Dieses Poster präsentiert die Anwendung dieser Methode an dem Demonstrationskraftwerk SOLUGAS, einem Cavityrohrreceiver mit Mikrogasturbine [2]

Absorber tube displacement in parabolic trough collectors – A review and presentation of an airborne measurement approach

Parabolic trough collectors for concentrating solar sower plants are large scale optical devices with demanding requirements on optical and mechanical properties. Accurate mirror shape and absorber tube alignment are necessary to harness solar radiation with high efficiency. There are several methods to assess the shape of the mirror surface, yet there exist few approaches to effectively measure the Position of the absorber tube. This paper provides a comprehensive overview on causes and effects of absorber tube displacement and on state of the art measurement techniques. A new approach on fully automated airborne absorber tube position measurement for parabolic trough collectors is presented, which outperforms existing methods concerning speed, spatial resolution, and level of automation, thereby achieving an accuracy of about 1.5 mm in vertical and lateral direction

Soiling determination for parabolic trough collectors based on operational data analysis and machine learning

Advanced cleaning strategies for parabolic trough collectors at concentrated solar power plants maximize the yield and minimize the costs for cleaning activities. However, they require information about the current soiling level of each collector. In this work, a novel, data-driven method for soiling estimation with machine learning for parabolic trough collectors is developed using gloss values as a surrogate for soiling values. Operational data and meteorological data from the solar field Andasol-3 with changing time horizons are used together with various Machine Learning techniques to estimate the soiling of every collector in the field. The best results were achieved with a Decision Tree model, with a coefficient of determination of $^2$ = 0.77 from the maximum value of 1 and a mean squared error of = 6.14 for the determination of specific soiling values. A second metric to evaluate the quality of soiling predictions from the models classifies whether soiling is above or below a cleaning threshold was also investigated. Model results are compared to soiling measurements that indicate the need for cleanings. Cleaning recommendations are derived and compared with the current fixed-time cleaning schedule of Andasol-3. All models show an improvement over the cleaning schedule currently in use. The use of a Decision Tree model increases the detected necessary cleanings by 12.2 %, while the number of unnecessary cleanings are reduced by 14.3 %. This has the potential to reduce operational costs and increase the solar field yield. The dataset used in this work is made publicly available https://doi.org/10.5281/zenodo.7061913, along with the code to reproduce all results, which can be found at https://doi.org/10.5281/zenodo.7554806

Techniques to Measure Solar Flux Density Distribution on Large-Scale Receivers

Flux density measurement applied to central receiver ystems delivers the spatial distribution of the concentrated solar radiation on the receiver aperture, measures receiver input power, and monitors and might control heliostat aimpoints. Commercial solar tower plants have much larger aperture surfaces than the receiver prototypes tested in earlier research and development (R&D) projects. Existing methods to measure the solar flux density in the receiver aperture face new challenges regarding the receiver size. Also, the requirements regarding costs, accuracy, spatial resolution, and measuring speed are different. This paper summarizes existent concepts, presents recent research results for techniques that can be applied to large-scale receivers and assesses them against a catalog of requirements. Direct and indirect moving bar techniques offer high measurement accuracy, but also have the disadvantage of large moving parts on a solar tower. In the case of external receivers, measuring directly on receiver surfaces avoids moving parts and allows continuous measurement but may be not as precise. This promising technique requires proper scientific evaluation due to specific reflectance properties of current receiver materials. Measurement-supported simulation techniques can also be applied to cavity receivers without installing moving parts. They have reasonable uncertainties under ideal conditions and require comparatively low effort

Air-Borne Shape Measurement of Parabolic Trough Collector Fields

The optical and thermal efficiency of parabolic trough collector solar fields is dependent on the performance and assembly accuracy of its components such as the concentrator and absorber. For the purpose of optical inspection/approval, yield analysis, localization of low performing areas, and optimization of the solar field, it is essential to create a complete view of the optical properties of the field. Existing optical measurement tools are based on ground based cameras, facing restriction concerning speed, volume and automation. QFly is an airborne qualification system which provides holistic and accurate information on geometrical, optical, and thermal properties of the entire solar field. It consists of an unmanned aerial vehicle, cameras and related software for flight path planning, data acquisition and evaluation. This article presents recent advances of the QFly measurement system and proposes a methodology on holistic qualification of the complete solar field with minimum impact on plant Operation

Heliostat Testing according to SolarPACES Task III Guideline

The SolarPACES Guideline for Heliostat Performace Testing finally provides a solid base for standardized testing and comparison as well as the definitions of essential heliostat parameters such as slope and tracking errors. SBPS is running an extensive test program for their 4 Stellio preseries heliostats at the DLR Solar Tower in Juelich, Germany until summer 2019. Additional objective is to accumulate operating hours and evaluate long-term effects on the Stellio performance quality. Slope error measurement has been performed by CSPS and is repeated every 3 months. First results show 1D slope errors of 0.7 to 1.2 mrad. Tracking performance could not have been concluded due to missing final measurements of the kinematic system of each heliostat which is necessary for calibration. However, beam centroid evaluation software has been tested with first uncalibrated tracking hours and is prepared for normal operation. First photogrammetric measurements have been performed to characterize the dead weight deflection of the heliostat in 15 different azimuth and elevation combinations. This has been prepared and implemented in Rhino CAD. Adaptions may be necessary to include pylon deflection as well

Simplified analytical model to describe wind loads and wind-induced tracking deviations of heliostats

Wind-induced tracking deviations of heliostats can be analyzed through numerical simulations or experimental studies on a full-scale heliostat. However, these methods are relatively costly and often, simpler estimations are necessary and sufficient. One simpler approach is to use an analytical model that describes the wind-induced tracking deviations and which requires only a few input parameters that can be determined through straightforward measurements at the full-scale heliostat. Therefore, this paper presents the derivation of an analytical model and describes the development process in a detailed way to clarify the necessary assumptions and simplifications. For verification purposes, the developed model is furthermore applied to measurement data of a field study. It is shown that the results of the model application agree well with the expectations and that the measured heliostat response matches the predicted response well, provided the underlying assumptions of the model fully apply to the investigated heliostat. Overall, no unexplainable inconsistencies are identified and the results support the model well. Thus, a method is provided which allows the estimation and prediction of wind-induced tracking deviations with comparatively little effort. In addition, the developed model helps to identify and analyze those parameters that have the greatest impact on the wind-induced tracking deviations of different types of heliostats