Serologische Untersuchung von Blutspenden auf Antikörper gegen SARS-CoV-2 (SeBluCo- Studie) – Blutspendedienste unterstützen die Pandemieüberwachung

Blutspendeproben können die SARS-CoV-2-Serosurveillance unterstützen, um Maßnahmen zur Infektionskontrolle anzupassen. In einer wiederholten Querschnittsstudie von April 2020 bis April 2021, September 2021 und April / Mai 2022 wurden aus 13 Blutspendeeinrichtungen 134.510 Proben in 28 Regionen auf Antikörper gegen SARS-CoV-2 getestet. Die Seroprävalenz lag bis Dezember 2020 unter 2 % und stieg im April 2021 auf 18,1 %, im September 2021 auf 89,4 % und im April / Mai 2022 auf 100 %. Die Untererfassung lag in den ersten beiden Wellen der Pandemie zwischen 5,1 und 1,1 und blieb danach unter 2, was auf eine angemessene Teststrategie und ein funktionierendes Meldesystem in Deutschland hinweist.Blood donor samples can support SARS-CoV-2 serosurveillance to adapt infection control measures. In a repeated cross-sectional study 134,510 specimens from 13 blood establishments in 28 study regions were tested for antibodies against SARS-CoV-2 from April 2020 to April 2021, September 2021, and April / May 2022. The SARS-CoV-2 seroprevalence remained below 2 % until December 2020 and increased to 18.1 % in April 2021, 89.4 % in September 2021, and to 100 % in April / May 2022. Underreporting ranged between 5.1 and 1.1 in the first two waves of the pandemic and remained below 2 afterwards, indicating an adequate test strategy and notification system in Germany

Erprobung eines Tracergas-Messverfahrens zur Bestimmung der Luftrückführrate bei offenen volumetrischen Receivern von Solarturmkraftwerken

Um die Luftrückführrate an offenen volumetrischen Receivern mit großer Genauigkeit bestimmen zu können, wird derzeit ein neuartiges Tracergas-Messverfahren entwickelt. Das Ziel der Diplomarbeit besteht in der Erprobung dieses Messverfahrens an einem bereits vorhandenen Receiver-Modell. Das Modell bildet einen Teil des Receivers des Solarturms Jülich nach und umfasst 6 x 9 Absorbermodule im Maßstab 1:2. Die Diplomarbeit ist in drei Teilaufgaben gegliedert. Zunächst sollen die bereits vorhandenen Komponenten des Versuchsstands ergänzt, miteinander verbunden und für den Betrieb vorbereitet werden. Einige Komponenten müssen noch beschafft werden. Das Programmieren einer Software für den Betrieb des Versuchsstands stellt eine weitere Teilaufgabe dar. Diese Software soll sowohl die Steuerung des Versuchsstands als auch die Aufnahme von Messwerten ermöglichen. Schließlich sollen erste Messungen bei unterschiedlichen Konfigurationen der Versuchsparameter durchgeführt werden. Dabei sollen das Messverfahren auf seine Praxistauglichkeit überprüft werden und Erfahrungen im Umgang mit der Messumgebung gesammelt werden. Sowohl die Fertigstellung der Hardware des Versuchsstands als auch die Programmierung der Software befinden sich jeweils in einem weit fortgeschrittenen Stadium. Der Versuchsstand wurde bereits in Betrieb genommen und es wurden einige Testmessungen durchgeführt. In Kürze folgt der Beginn der Hauptmessungen

Flux density measurement for industrial-scale solar power towers

For separate acceptance tests of a solar power tower’s heliostat field and receiver, it is necessary to determine the solar flux density distribution over the whole absorber surface. Integrating the flux density delivers the receiver input power, which is required for calculating the energy conversion efficiencies of both heliostat field and receiver. Furthermore, flux density measurement is valuable for supervision and control during operation of a power tower. Flux density at small-scale prototype receivers has mostly been measured by using a camera and a moving bar so far. The moving bar is a white diffusely reflecting target which is moved quickly through the radiation’s focus in front of the receiver surface. At the same time, a digital camera cap-tures the radiation reflected off the moving bar, which allows determining the incident flux density. At industrial-scale receivers though, the installation of a moving bar is hardly feasible due to difficult construction and high costs. Therefore, the development of a measurement method without any mov-ing parts is aspired. For this purpose, the radiation reflected off the absorber itself can be measured in order to calculate the incident flux density [1]. Preliminary work on this method is still immature and has not yet lead to a reliable and satisfying measuring accuracy under all conditions [2]; achieving this is a main aim of the presented thesis. The central challenge with measuring flux density by reflection off the absorber is the absorber’s non-diffusive reflectivity, which depends especially on the direction of the incident radiation as well as on the observation angle [1]. Hence, detailed understanding of reflection at the structured surface of open volumetric receivers as well as tube receivers and following software-aided correction of these effects are essential for reducing the measurement uncertainty. The improvements will be imple-mented and tested at the Solar Tower Jülich. Finally, the improved flux density measurement system is planned to be used in a demonstrational acceptance testing at the Solar Tower Jülich, including a comparison of measurements and simulation results

Flux density measurement for industrial-scale solar power towers using the reflection off the absorber

Flux density measurement is precious for operation as well as for performance testing of solar power towers. The radiation reflected off the absorber can be used for this task. The disturbance of the plant operation is close to zero. Besides a digital camera, a computer and optionally a radiometer, almost no further hardware is required. That’s why it is suitable for industrial-scale receivers. This paper presents several enhancements for this measuring process. Especially the so-called “scan method” appears promising, because it leads to significantly smoother flux density results compared to formerly presented methods. The article also deals with the determination of the irradiation’s directional composition as well as with calibration routines. The proposed innovations were demonstrated at the Juelich Solar Tower with its open volumetric receiver and are likely to be suitable for external tube receivers, too. A plausibility check using CFD simulations was carried out. In summary, the discussed techniques show promise for future application at large-scale solar towers

CFD model for the performance estimation of open volumetric receivers and comparison with experimental data

Obtaining reliable information on the thermal performance of a receiver in a solar thermal power plant during the design phase is essential for optimisation purposes and for the determination of the economic performance of the entire power plant. In open volumetric receivers, where the heat transfer circuit is open to the environment, this task is particularly challenging due to the influence of convection phenomena on the air return ratio and thus the heat losses. These losses can only be estimated by means of CFD simulations, however, since the small scale absorber structure is several orders of magnitude smaller than the receiver itself, the required computational grid becomes too large to be economically viable. In this paper a modelling approach is presented, which for the first time allows the efficient simulation of the entire receiver including the flow in front of and around the receiver while at the same time considering internal heat transfer within the absorber. A set of boundary conditions has been developed for the absorber surface of open volumetric receivers in which the characteristic behaviour of the absorber is modelled without the need of detailed resolution of the absorber structure. The model has been validated against new measurements at the solar tower Jülich. Moreover, in comparison with literature data of air return ratio measurements a very good agreement was found. A characteristic map of the receiver efficiency has been compiled showing peak efficiencies of the open volumetric receiver of the solar tower Jülich of 70.9% at a hot air temperature of 650 °C and 75.4% at 450 °C. The model can now be used for the assessment of design concepts for commercial power plants

Proof of Concept: Real-Time Flux Density Monitoring System on External Tube Receivers for Optimized Solar Field Operation

An experimental tube receiver was constructed, built and brought to operation. This receiver served as a model to try out the so-called scan-method and the measurement of the flux density by reflection off the receiver. in real time during irradiation. A comparison with a flux map obtained by a radiometer-based method shows qualitatively similar results. It is concluded that the camera-method is applicable to tube receivers. Experiments at large-scale industrial receivers are planned