Tim Schlichting

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

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Marc Röger

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Kristina Blume

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Robert Pitz‐Paal

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Tobias Hirsch

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Zeyad Yasser

ParisTech

Reiner Buck

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Andreas Pfahl

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Stefan Wilbert

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Pascal Kuhn

Energie Baden-Württemberg (Germany)

Luis F. Zarzalejo

Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas

Cooperative Institutions

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

ParisTech

University of Patras

Institut für Solarenergieforschung

Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas

University of Almería

Solarzentrum Stuttgart (Germany)

Dienstleistungszentrum Ländlicher Raum

Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau

University of Kaiserslautern

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Experimental Methods for Measuring the Efficiency of a Molten Salt Central Receiver

SolarPACES Conference Proceedings (2024)

M. Fernández-Torrijos Cathy Frantz Jana Stengler Marc Röger Tim Schlichting

In this work, two different methods for measuring the efficiency of central receivers are analyzed by the case of the High Performance Molten Salt II Project (HPMS-II): the continuous power-on method, and the semi-analytical method. The main difference between the two methods is the procedure to calculate the thermal losses of the receiver: on the one hand, the continuous power-on method calculates the thermal losses from the measurement of the absorbed power by the molten salt for different measured incident powers on the receiver. Here, it is assumed that the thermal losses are independent of the incident power if the molten salt temperature is kept constant. On the other hand, the semi-analytical method calculates the thermal losses as the sum of convective and radiative losses, calculated directly from the Newton and Stefan-Boltzmann equations by measuring the temperature of the tube surface, the ambient temperature, and the wind speed. Therefore, the calculation of the thermal losses is independent from one method to another. The procedure of applying these methods during the experimental test campaign of the HPMS-II receiver is detailed in this paper. Additionally, an uncertainty analysis of both methods is conducted to determine the uncertainty expected for the receiver efficiency measurements.

10.52825/solarpaces.v1i.715

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A way to increase parabolic trough plant yield by roughly 2% using all sky imager derived DNI maps

AIP conference proceedings (2020)

Bijan Nouri Kareem Noureldin Tim Schlichting Stefan Wilbert Tobias Hirsch

Solar fields of parabolic troughs are extensive complex thermal hydraulic facilities. Intra-hour and intra-minute variabilities of the DNI, mainly caused by passing clouds, pose an operational challenge for parabolic trough power plants. Under perfect circumstances a solar field controller would adjusts the mass flow in such a way, that the design temperature is always maintained constant with a maximized focus rate. However, heterogeneous irradiance conditions or flow distribution may cause some solar field sections to temporarily overheat while others may not reach the set point temperature, which in turn leads to an economic loss. State of the art solar field controllers have only access to incomplete information on spatial DNI variability, from DNI measurements of few pyrheliometers. Solar field controllers could be optimized with access to highly resolved DNI informations both in space and time. Such DNI information can be provided by all sky imager (ASI) based irradiance monitoring systems. In a previous study we developed and benchmarked new solar field controllers with access to spatial DNI information from an ASI system for a 50 MWe plant close to Córdoba (Spain). Significant improvements in revenue were observed. Yet, this previous study was limited to 22 days only. In this study, we estimate the potential benefit of these new solar field controllers over a 2 year period on the basis of the simulation results over 22 days. The upscaling method makes use of DNI variability classes. Using the ASI data we obtain a significant improvement in revenue up to 2% for the 2 year period.

Parabolic trough

10.1063/5.0028667

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Optimization of parabolic trough power plant operations in variable irradiance conditions using all sky imagers

Solar Energy (2020)

Bijan Nouri Kareem Noureldin Tim Schlichting Stefan Wilbert Tobias Hirsch

Parabolic trough

Dispatchable generation

Concentrated solar power

Solar Power

10.1016/j.solener.2020.01.045

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Citations (27)

First lay-down heliostat with monolithic mirror-panel, closed loop control, and cleaning system

AIP conference proceedings (2019)

Andreas Pfahl Jens Rheinländer Andreas Krause Reiner Buck Stefano Giuliano

The first lay-down heliostat with monolithic concentrator was erected at the Solar Tower Jülich. The main components and their main features are described: azimuth and elevation drive, concentrator, control, and the cleaning system concept. The dimensions of the elevation drive and the carriage already match the requirements of a 50 m² heliostat that shall be developed in a follow-up project.

Heliostat

Elevation (ballistics)

Concentrator

10.1063/1.5117554

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Dynamic photogrammetry applied to a real scale heliostat: Insights into the wind-induced behavior and effects on the optical performance

Solar Energy (2020)

Kristina Blume Marc Röger Tim Schlichting Ansgar Macke Robert Pitz‐Paal

Wind loads may decrease a heliostat's optical performance by affecting its shape and orientation. As small scale wind tunnel or numerical models cannot reflect a heliostat's dynamic behavior entirely, in this study we investigated a real scale Stellio heliostat installed on the DLR heliostat testing platform where it was exposed to the natural wind. The wind-induced response was captured with a dynamic photogrammetry system that combines a high spatial and high temporal resolution. As its application to a heliostat is novel, the first focus of this paper is to validate the applied setup and the accuracy of measured displacements. The second focus is to discuss the wind-induced Stellio behavior. A method is presented which allows for separating the total wind-induced behavior into a tracking- and a slope-relevant part. Based on this separation, the wind-induced tracking deviation (0.44mradRMS) during the investigated measurement period (mean wind speed ≈4.8m/s, mean turbulence intensity ≈26%) reached a level of approximately one third of a heliostat's typical total tracking deviation. Likewise, during the time step of largest deformations, the wind-induced slope deviation (0.75mradRMS) of the most affected facet reached a level of approximately one third of a Stellio facet's total slope deviation. However, wind-induced slope deviations occurred only locally and temporally. Furthermore, wind-excited eigenfrequencies were revealed to have a negligible impact on both the tracking and slope deviation in case of the Stellio. Oscillations and deformations related to frequencies below the eigenfrequencies were rather found to have a predominant impact on the optical performance.

Heliostat

Tracking (education)

10.1016/j.solener.2020.10.056

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Citations (16)

Heliostatenqualifizierung auf der Testplattform in Jülich

Kristina Blume Tim Schlichting Marc Röger Ansgar Macke Andreas Kämpgen

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Status update of the SolarPACES heliostat testing activities

AIP conference proceedings (2022)

Marc Röger Kristina Blume Tim Schlichting Mike Collins

Power tower or central receiver systems use hundreds to ten thousands of two-axis tracking mirrors, so called heliostats, which reflect and focus the sunlight onto a receiver on top of a tower during the day.As basis for a well performing heliostat field, a single heliostat has to perform "correctly".In order to describe and measure the performance of a single heliostat, the SolarPACES Guideline for Heliostat Performance Testing has been developed by a group of R&D and industry experts during the last years.However, at the end, the performance of the whole field, which means the superposition and interaction of all heliostats determines the energy collected in the aperture of a solar central receiver.For that reason, a second guideline is currently outlined, the SolarPACES Guideline for Heliostat Field Performance Testing.Both guidelines aim to be commonly agreed protocols between R&D centers and industry in the field of heliostat performance testing.Recently, a third guideline activity has been started to improve and unify heliostat wind load design methods.The once finalized guidelines (or their concepts) should be included in international standards (e.g.IEC) and used by national organizations like DKE, AENOR, ASME, ASTM.This paper gives an update of the state of the three guidelines being developed in the SolarPACES task III-heliostat working group.

Heliostat

10.1063/5.0087037

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Citations (6)

Design, construction, and qualification of a lightweight, modular heliostat made from high-performance concrete

Solar Energy (2024)

Patrick Forman Marius Schellen Tim Schlichting Andreas Pfahl Peter Mark

Heliostat

Modular construction

10.1016/j.solener.2024.113093

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Bewertung der Verwendbarkeit von Strahlungskarten für den Einsatz in der Regelung eines Parabolrinnensystems

Tim Schlichting

The present work deals with the usability of irradiance maps to support the control of a parabolic trough system. Irradiance maps describe the spatially-resolved Direct Normal Irradiance across the power plant. To utilize the information provided by the irradiance maps, classification methods are developed, investigated and evaluated. The created classes describe the spatial and temporal variability of Direct Normal Irradiance which are triggered by transient clouds. The purpose of this work is to optimize the control by the information provided by the irradiance maps. Therefore, the impact of the transient clouds represented by the created classes needs to be investigated by using the simulation environment Virtual Solar Field. Thereby occurring problems in each class can be spotted and solution approaches derived. The gained knowledge leads to class specific control approaches, which are capable of stabilizing the solar power plant during transient cloud conditions. During the entire optimization process, irradiance maps that represent 30 test days are investigated. Finally, the usability of irradiance maps in context with the control of a parabolic trough system is evaluated by comparing the results of the optimized Control to the initial control.

Transient (computer programming)

Parabolic trough

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Citations (1)