Documents disponibles écrits par cet auteur

Heliostat shape and orientation by edge detection / Marc Roger in Transactions of the ASME. Journal of solar energy engineering, Vol. 132 N° 2 (Mai 2010) 

Public ISBD [article]  in Transactions of the ASME. Journal of solar energy engineering > Vol. 132 N° 2 (Mai 2010) . - pp. [021002/1-7] Titre : Heliostat shape and orientation by edge detection Type de document : texte imprimé Auteurs : Marc Roger, Auteur ; Christoph Prahl, Auteur ; Steffen Ulmer, Auteur Année de publication : 2011 Article en page(s) : pp. [021002/1-7] Note générale : Energie Solaire Langues : Anglais (eng) Mots-clés : Edge  detection  Photogrammetry  Heliostat  shape  Heliostat  orientation  Solar  tower  Digital  imaging Index. décimale : 621.47 Résumé : The heliostats of central receiver solar power plants reach dimensions up to 150 m2 with focal lengths up to 1000 m. Their optical properties and tracking accuracy have great influence on the power plant efficiency and need to be monitored both at plant start up and during operation. Up to now, there are few efficient and fast measurement techniques that allow the heliostat properties to be measured. Flux density measurements and close-range photogrammetry are possible approaches, yet they do not fulfill the requirement to be accurate, inexpensive, and fast at the same time. In this paper, we present a noncontact measurement principle, which uses edge detection to extract the heliostat and facet vertices. This information is used to calculate the surface normals. Furthermore, the corners can replace retroreflective targets generally used in close-range photogrammetry, thus, enabling a fast and completely automatic evaluation of the three-dimensional heliostat structure. The pictures are provided by a digital camera, which is mounted on a pan tilt head on top of the central receiver tower, offering visibility to all heliostats and allowing the automated qualification of whole heliostat fields in a short period of time. It is shown that measurement uncertainties in heliostat orientation for the investigated heliostat are below 4 mrad in 80% of the relevant heliostat positions. Heliostat orientation is available within three minutes. Photogrammetric measurements based on edge detection at a 40 m2 CESA-1 heliostat at the Plataforma Solar de Almerìa exhibit an accuracy of 1.6 mrad for a single-facet normal vector with the results being available within 30 min. The reduced measurement time allows the economic characterization of entire heliostat fields. The lower accuracy compared with manual photogrammetry with retroreflective targets is still sufficient to detect facet misalignments in existing heliostat fields. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO00013200 [...] [article] Heliostat shape and orientation by edge detection [texte imprimé] / Marc Roger, Auteur ; Christoph Prahl, Auteur ; Steffen Ulmer, Auteur . - 2011 . - pp. [021002/1-7]. Energie Solaire Langues : Anglais (eng) in Transactions of the ASME. Journal of solar energy engineering > Vol. 132 N° 2 (Mai 2010) . - pp. [021002/1-7] Mots-clés : Edge  detection  Photogrammetry  Heliostat  shape  Heliostat  orientation  Solar  tower  Digital  imaging Index. décimale : 621.47 Résumé : The heliostats of central receiver solar power plants reach dimensions up to 150 m2 with focal lengths up to 1000 m. Their optical properties and tracking accuracy have great influence on the power plant efficiency and need to be monitored both at plant start up and during operation. Up to now, there are few efficient and fast measurement techniques that allow the heliostat properties to be measured. Flux density measurements and close-range photogrammetry are possible approaches, yet they do not fulfill the requirement to be accurate, inexpensive, and fast at the same time. In this paper, we present a noncontact measurement principle, which uses edge detection to extract the heliostat and facet vertices. This information is used to calculate the surface normals. Furthermore, the corners can replace retroreflective targets generally used in close-range photogrammetry, thus, enabling a fast and completely automatic evaluation of the three-dimensional heliostat structure. The pictures are provided by a digital camera, which is mounted on a pan tilt head on top of the central receiver tower, offering visibility to all heliostats and allowing the automated qualification of whole heliostat fields in a short period of time. It is shown that measurement uncertainties in heliostat orientation for the investigated heliostat are below 4 mrad in 80% of the relevant heliostat positions. Heliostat orientation is available within three minutes. Photogrammetric measurements based on edge detection at a 40 m2 CESA-1 heliostat at the Plataforma Solar de Almerìa exhibit an accuracy of 1.6 mrad for a single-facet normal vector with the results being available within 30 min. The reduced measurement time allows the economic characterization of entire heliostat fields. The lower accuracy compared with manual photogrammetry with retroreflective targets is still sufficient to detect facet misalignments in existing heliostat fields. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO00013200 [...]

Validation of two optical measurement methods for the qualification of the shape accuracy of mirror panels for concentrating solar systems / Tobias März in Transactions of the ASME. Journal of solar energy engineering, Vol. 133 N° 3 (N° Spécial) (Août 2011) 

Public ISBD [article]  in Transactions of the ASME. Journal of solar energy engineering > Vol. 133 N° 3 (N° Spécial) (Août 2011) . - 07 p. Titre : Validation of two optical measurement methods for the qualification of the shape accuracy of mirror panels for concentrating solar systems Type de document : texte imprimé Auteurs : Tobias März, Auteur ; Christoph Prahl, Auteur ; Steffen Ulmer, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Solar energy Langues : Anglais (eng) Mots-clés : Error  analysis  Hybrid  power  systems  Mirrors  Photogrammetry  Solar  energy  concentrators  Solar  power  stations  Spatial  variables  measurement  Thermal  power  stations Index. décimale : 621.47 Résumé : The solar field is the major cost component of a solar thermal power plant and the optical quality of the concentrators has a significant impact on the field efficiency and thus on the performance of the power plant. Measuring slope deviations in the parabolic shape of the mirror panels in the accuracy and resolution required for these applications is a challenge as it is not required with the same characteristics in other industries. Photogrammetry and deflectometry are the two optical measurement methods that are typically used to measure this shape accuracy of mirror panels used in CSP applications. They have been compared and validated by measuring a typical mirror panel under optimal conditions. Additionally, a flat water surface has been measured as an absolute reference object using deflectometry. The remaining deviations between the results of both methods and to the reference object are discussed and possible sources of errors during the measurement are identified. A detailed error analysis is conducted for both methods and compared to the experimental findings. The results show that both methods allow for surface slope measurement with the necessary accuracy for present CSP applications and that among the two, deflectometry exhibits advantages in speed, measurement accuracy, and spatial resolution. However, for obtaining correct results several sources of errors have to be addressed appropriately during measurement and postprocessing. DEWEY : 621.47 ISSN : 0199-6231 En ligne : asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO0001330000030310220 [...] [article] Validation of two optical measurement methods for the qualification of the shape accuracy of mirror panels for concentrating solar systems [texte imprimé] / Tobias März, Auteur ; Christoph Prahl, Auteur ; Steffen Ulmer, Auteur . - 2012 . - 07 p. Solar energy Langues : Anglais (eng) in Transactions of the ASME. Journal of solar energy engineering > Vol. 133 N° 3 (N° Spécial) (Août 2011) . - 07 p. Mots-clés : Error  analysis  Hybrid  power  systems  Mirrors  Photogrammetry  Solar  energy  concentrators  Solar  power  stations  Spatial  variables  measurement  Thermal  power  stations Index. décimale : 621.47 Résumé : The solar field is the major cost component of a solar thermal power plant and the optical quality of the concentrators has a significant impact on the field efficiency and thus on the performance of the power plant. Measuring slope deviations in the parabolic shape of the mirror panels in the accuracy and resolution required for these applications is a challenge as it is not required with the same characteristics in other industries. Photogrammetry and deflectometry are the two optical measurement methods that are typically used to measure this shape accuracy of mirror panels used in CSP applications. They have been compared and validated by measuring a typical mirror panel under optimal conditions. Additionally, a flat water surface has been measured as an absolute reference object using deflectometry. The remaining deviations between the results of both methods and to the reference object are discussed and possible sources of errors during the measurement are identified. A detailed error analysis is conducted for both methods and compared to the experimental findings. The results show that both methods allow for surface slope measurement with the necessary accuracy for present CSP applications and that among the two, deflectometry exhibits advantages in speed, measurement accuracy, and spatial resolution. However, for obtaining correct results several sources of errors have to be addressed appropriately during measurement and postprocessing. DEWEY : 621.47 ISSN : 0199-6231 En ligne : asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO0001330000030310220 [...]