Fast calibration of heliostats

We present the HelioPoint method - a fast airborne method for calibrating entire heliostat fields

Airborne characterization of the Andasol 3 solar field

The solar-thermal parabolic trough power plant Andasol 3 (AS3) near Granada/Spain operated by Marquesado Solar SL (MQS) was commissioned in autumn 2011. The installed capacity of 49.9 MWel in combination with thermal energy storage (TES) capacity for 7.5 hours at full load results in a net annual energy production of more than 165 GWh1 (Dinter and Gonzalez 2014). The German Aerospace Center (DLR) has developed a tool for airborne characterization of entire parabolic trough plants. The approach called QFlySURVEY uses an unmanned aerial vehicle (UAV) equipped with a high resolution digital still camera and delivers effective mirror slope deviation and the absolute orientation of the optical axis of each solar collector element (SCE). In order to validate and demonstrate QFlySURVEY, a comprehensive measurement campaign was undertaken in the AS3 power plant in cooperation with MQS between 2016-10-24 and 2016-11-14. The main objective was to demonstrate the advantages of airborne solar field characterization in terms of rapid data acquisition, negligible interference with plant operation, and without the need of any additional installation of measurement equipment in the solar field. QFlySURVEY provides accurate quantitative measures of optical performance of the solar field and supports the maximization of the thermal energy collected from the solar field by identifying low performing areas and the causes for optical losses

Fast airborne calibration of entire solar fields of heliostats

We present a fast airborne method for calibrating entire heliostat fields

Airborne Soiling Measurements in Operating Solar Fields

Soiling is an issue receiving increased attention over the last years. Currently solar field soiling levels are measured with handheld reflectometers that need a technician to operate and are limited to measuring small sections of the vast mirror surfaces present in CSP solar fields. Earlier we presented a method to determine the soiling levels over parabolic trough solar fields using a drone and image analysis techniques in combination with particle scattering simulations [1]. This previous method evaluated those areas of a mirror that showed the black absorber tube in the direct reflection. The light reaching a given pixel of the camera sensor consists of light scattered by the dust on the mirror and the so-called “background contribution” showing the object reflected in the observed section of the mirror. As the reflections of the absorber tube were used in [1] the background contribution could be neglected. Then scattering simulations were used to correct for the effect of different incidence and viewing angles on the intensity of the scattering signal. A good agreement between the scattering corrected RGB camera signal and reference reflectometer measurements could be shown. In operating power plants the parabolic trough field needs to de-focus in order to realize the black absorber tube background. In tower plants a black target would be required. In this study we present an enhancement of the method that allows evaluation of mirror areas that show the sky as a background. Thus, the enhanced method facilitates soiling measurements during full solar field operation and for all CSP technology options. The approach to determine the sky background to be subtracted from the scattering signal is presented and a feasibility study using a test dataset including reference soiling levels will be given

Accelerated Ageing of Solar Reciever Coatings: Experimental Results for T91 and VM12 Steel Substrates

This paper reports experimental results for accelerated ageing test campaigns performed on four different solar receiver coatings applied on T91 and VM12 steel substrates. VM12 tubular samples are exposed at a dish test facility in order to perform thermal cycles under concentrated solar flux. No significant optical degradation could be observed on coated samples after 100 thermal cycles (50 hours at 650 °C), while bare and polished reference substrates oxidized during testing. Three solar receiver coatings achieved a stable solar weighted absorptance αs above 95 % after exposure. A selective coating further showed a thermal emittance of 25 % at 650 °C, instead of 65-75 % for non-selective coatings, thus achieving a thermal efficiency above 90 % at 250 kW/m2, instead of 85 % for non-selective coatings. T91 coated metal coupons were tested in four standard climate test chambers for condensation, damp heat, humidity freeze and neutral salt spray. Two non-selective coatings passed all climate tests without significant optical degradation, while the selective coating did not pass the neutral salt spray test due to severe corrosion