Standardization of Mirror Shape Accuracy Measurement - First Results of Round Robin Test between DLR and Fraunhofer ISE

Standardized qualification measurement and evaluation of parabolic trough collectors include reflector shape accuracy, as well as the solar reflectance properties of reflector materials and durability tests. Within SolarPACES Task III a draft guideline for the measurement and assessment of mirror shape for concentrating solar collectors was elaborated. In order to verify the current status of shape and slope testing a round robin measurement campaign between DLR and Fraunhofer ISE has been initiated within the German StaMeP project

Advanced Measurement Techniques to Characterize the Near-Specular Reflectance of Solar Mirrors

The precise measurement of the reflected energy form a solar reflector to the Receiver is a challenging Task because of ist dependency on three different Parameters: the wavelength of the incident lieght, ist incidence angle and the acceptance angle of the Receiver. Up to today, the commonly empleyed measurement Equipment is not able to fully characterize the mirrors in the required range of Parameters which is relevant for CSP. Within this work, four reflectometers were upgraded to overcome the current drawbacks. A Round Robin test among the different characterization methods has been carried out on four reflector materials. The conclusions drawn from the comparison of the measurement results help to improve the current SolarPACES Reflectance Guideline

Konzentrierende Solarkollektoren für Prozesswärme und Stromerzeugung

Mit konzentrierenden Kollektoren wird Prozesswärme für industrielle Prozesse und zur Stromerzeugung in Gebieten mit hohem Direktstrahlungsanteil erzeugt. Deutsche Firmen und Forschungseinrichtungen tragen dazu bei, konzentrierende Kollektoren zu entwickeln und in den internationalen Markt zu bringen. In diesem Beitrag werden konzentrierende Kollektoren vorgestellt und einen Überblick über Forschungsinhalte aus den Bereichen neue Kollektorkonzepte, Direktverdampfung und kombinierte Strom- und Prozesswärmeerzeugung gegeben

Performance assessment of a secondary concentrator for solar tower external receivers

In the EU-project RAISELIFE, a secondary concentrator for Solar Tower systems has been developed conceptually, which is discussed techno-economically herein. Based on a detailed three-level simulation methodology (optical assessment of radiation distribution on receiver surfaces, thermal FEM-simulation of receiver efficiency and transient system simulation), an annual performance assessment of the secondary concentrator by means of a reference system incorporating a receiver with a thermal rating of 600 MW is presented, including a breakdown of the different loss contributions. The annual electrical yield for the secondary setup is increased by 1.57% compared to the reference system, with the potential for further boosts. Regarding material and component costs, an integration of this secondary design could decrease the receiver costs by up to 6.1%

Hemispherical Reflectance Results of the SolarPACES Reflectance Round Robin

Mirrors are the first link in the energy-conversion chain from Sun to electricity-delivery in the grid. Shape and solar reflectance are the key-parameters of mirrors, respectively affecting how solar radiation is concentrated around the focus, and how much of the impinging solar power is reflected. In SolarPACES Task III, an expert group is drafting the solar reflectance guidelines; in order to speed up the discussion the SRRR round robin was launched at the beginning of 2013. Identical kits, each one consisting of ten specimens collected from eight cooperating producers, were distributed and measured at six research institutes, acting as evaluators. The kit includes both traditional (glass based) and innovative (first-surface) solar mirrors. The paper only reports on the simplest task among those of SRRR: the solar hemispherical reflectance measurement. Near-specular solar reflectance was also measured and compared but the results are still under investigation and are not part of this paper. The measurements were accomplished according to the guidelines. The differences among the achieved results are within the typical accuracy of spectrophotometers, demonstrating the reliability of the reflectance guidelines. The statistic of the deviations from the true value is analysed separately for each evaluator, and allows us to infer information abut the gauging-status of the adopted reference mirror, as well as the measurement reproducibility

Kalibrierungsverfahren und Kalibrierungsvorrichtung für eine Gruppe von Reflektoren zur Konzentration von Sonnenstrahlung auf einen Strahlungsempfänger

The invention relates to a calibration method for a group of reflectors for concentrating solar radiation onto a radiation receiver, having the following steps: A) aligning the reflectors in order to at least partly expose a calibration surface to solar radiation reflected by the reflectors; B) modifying the intensity distribution of the radiation incident on the calibration surface by carrying out a pattern of movements by means of each reflector of the group, wherein at least one specified parameter for the pattern of movements of each reflector differs from the parameters of the other reflectors, said parameter being selected from the group: - movement frequency, - movement amplitude, - movement phase position, and - path curve of the solar radiation reflected by the reflector within the calibration surface; C) recording rows of pixels for a plurality of differently located location points of the calibration surface by means of at least one camera, each row of pixel having at least five temporally offset pixel recordings; D) ascertaining a spectrum for each row of pixels by transforming the row of pixels into the frequency domain; E) assigning a subset of spectra to the reflectors on the basis of the movement pattern parameter of the reflector; and F) determining at least one reflection target position for each reflector at least on the basis of the subset of spectra assigned to the reflector. The invention additionally relates to a calibration device for a group of reflectors for concentrating solar radiation onto a radiation receiver