The Experts below are selected from a list of 630 Experts worldwide ranked by ideXlab platform
Bernhard Hoffschmidt - One of the best experts on this subject based on the ideXlab platform.
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Development of a Transient Heat Recovery Steam Generator of the Solar Tower Power Plant Juelich
2020Co-Authors: Spiros Alexopoulos, Bernhard Hoffschmidt, Markus Latzke, J SattlerAbstract:This work describes the procedure of transient simulation for a hybridized solar tower power plant with open-Volumetric Receiver for a site in Northern Algeria. The simulation models have been developed in the simulation environment MATLAB/Simulink. The validation of the simulation tool against real plant data is presented in this work. Basic design calculations for the Algerian plant have been conducted on basis of meteorological data provided by satellites to investigate different concepts. For the concept that is most promising a transient annual simulation using local measured meteorological data has been conducted to yield detailed and accurate results. In addition, a parameter analysis of different thermal energy storage capacities has been carried out.
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Modelling and validation of a transient heat recovery steam generator of the solar tower plant juelich
2020Co-Authors: Spiros Alexopoulos, Bernhard Hoffschmidt, G Breitbach, Markus LatzkeAbstract:Germany’s first and only solar tower power plant for experimental and demonstration purposes has been erected in the town of Julich, North-Rhine-Westphalia. The central Receiver plant, which has been designed with an open-Volumetric Receiver, supplies the grid with a nominal power of 1.5 MWe. Through the open-Volumetric Receiver ambient air is drawn in and due to the concentration high temperatures from 600°C to 800°C can be achieved. These temperatures are in a range to fire a heat recovery steam generator (HRSG) that produces steam in a conventional water-steam-cycle. The presented work describes the development of a transient heat recovery steam generator (HRSG) in the simulation environment MATLAB/Simulink. The implemented simulation model has been validated by comparing the computed results with real performance data of the solar tower power plant Julich. The results show that the model can describe the transient behaviour in a exact way. Additionally, the preciseness of the model could be validated by a deviation less than 9%. The developed HRSG model is integrated in a simulation tool that models the whole power plant. With this simulation tool the annual electricity production of different plant configurations at various sites can be computed as well as optimised plant operations investigated and developed.
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The Solar Tower Jülich – First Operational Experiences and Test Results
2020Co-Authors: Stefan Pomp, Peter Schwarzbozl, Gerrit Koll, Thomas Hartz, Felix Göhring, Mark Schmitz, Bernhard HoffschmidtAbstract:Since March 2009 the Solar Tower Julich is in solar operation. During the last 18 month various operation experiences in different operation modes (gas fired, hybrid & solar only) could be gained. The performance of the main components and of the whole solar power plant were tested. The operation and control of the solar power plant is well performing. All the main components with the exception of the heliostat field are performing as expected or better. In particular the interaction between the main components, the hot- and warm-air-systems and the water-steam-cycle is well functioning. The functionality of the solar power plant concept with an open Volumetric Receiver could be demonstrated. The necessary technical expertise for the further development of the technology could be gained and the next plant generation for a location in north Africa is currently under design.
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induced infrared thermography flow visualizations under the extreme conditions of an open Volumetric Receiver of a solar tower
International Journal of Heat and Fluid Flow, 2017Co-Authors: Arne Tiddens, Kai Risthaus, Marc Roger, Hannes Stadler, Bernhard HoffschmidtAbstract:Current measurement techniques do not allow the visualization of the return air flow of open Volumetric Receivers in solar tower power plants. The reason is that the region of interest is irradiated by concentrated solar radiation and is located on top of a tower. Therefore, a novel method of measurement, the Induced Infrared Thermography (IIT) is introduced within this paper. With this method the return air can easily be observed with an infrared camera. As air has a very low emissivity in the infrared region the activity has to be induced by the addition of an infrared-active component, here carbon dioxide. The temperature of the infrared-active component has the greatest influence on the signal strength but the mole fraction of the component and the distance to the infrared camera are also important. Due to temperature restrictions, the measured signal to noise ratio is low and therefore several post-processing steps have to be conducted to visualize the return air. The most important step for the visualization is subtracting a background image. Furthermore, a video filter is employed in order to remove noise. A time series of ITT images can be used to obtain information on the velocity fields of the flow. The process, called Infrared Image Velocimetry (IRIV) here, is similar to Particle Image Velocimetry (PIV) and is applied in this paper to external fluid flows of the open Volumetric Receiver. As IRIV is in an early stage of development the depicted results are treated as qualitative vector fields.
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Air return ratio measurements at the solar tower Jülich using a tracer gas method
Solar Energy, 2017Co-Authors: Arne Tiddens, Marc Roger, Hannes Stadler, Bernhard HoffschmidtAbstract:Abstract The air return ratio is a key factor for the overall efficiency of the open Volumetric Receiver concept. Although first measurements of the air return ratio exist for smaller setups of the open Volumetric Receiver concept, so far no measurement of the air return ratio has been presented for the Solar Thermal Test and Demonstration Power Plant Julich ( ≈ 1.5 MW, ≈10 (kg air)/s; ≈700 °C). This paper describes the application of a tracer gas method at the solar tower Julich to determine this substantial ARR. As tracer gas the environmentally friendly helium has been chosen. The helium is injected dynamically into the circular air flow of the system and the helium mole fraction is measured using a mass spectrometer. The dynamic concentration response of the system is used to determine the air return ratio. This dynamic method only requires one location of measurement. First measurements with this dynamic method were conducted at the solar tower Julich. The ARR of STJ was measured with and without irradiation of the main Receiver with high accuracy. Under low-wind conditions and without irradiation of the main Receiver the air return ratio was measured to be ( 67.7 ± 0.5 ) % for an air mass flow of ( 9.96 ± 0.04 ) kg / s . A slightly higher air return ratio of ( 68.6 ± 0.7 ) % was measured under irradiation with an air mass flow of ( 9.94 ± 0.04 ) kg / s . The air return ratio was sensitive to the air mass flow, showing significantly lower rates when moving further away from the 10 kg / s design air mass flow to 5 kg / s .
Ya-ling He - One of the best experts on this subject based on the ideXlab platform.
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study on heat transfer and stress characteristics of the pressurized Volumetric Receiver in solar power tower system
Applied Thermal Engineering, 2018Co-Authors: Baocun Du, Ya-ling HeAbstract:Abstract In this paper, the analysis of heat transfer and stress characteristics in pressurized Volumetric Receiver (PVR) is presented by coupling Monte Carlo Ray Tracing (MCRT), Finite Volume Method (FVM) and Finite Element Method (FEM). Firstly, an integration model coupling MCRT, FVM and FEM applied in PVR is developed. Based on this model, the coupled characteristics of optical-thermal-stress are numerically studied. Meanwhile, the solar flux is homogenized using multi-point aiming strategy for multi-heliostat field zones. Finally, the effects of air mass flow and inlet temperature on the heat transfer and stress characteristics are discussed. The results indicate that the solar flux distributions on aperture and SiC porous absorber are more uniform using multi-point aiming strategy, and the peak flux in porous could be reduced by an order of magnitude compared with single-point. The peak stress of quartz window occurs at the contact position between the steel shell and quartz window, and the damage would not happen because of the peak stress is lower than the ultimate strength. The inlet parameters of air have significantly influences on the heat transfer and stress characteristics of Receiver. For example, when the air with higher temperature is adopted, the SiC porous temperature increases by 20%, and the temperature and stress of quartz window increase by 31% and 60%, respectively. The overheating in SiC porous could occur using lower mass flow rates, however, the quartz glass stress exhibits a decreasing tendency when the mass flow decreases. Besides, the temperatures of outlet air and porous absorber increase when the flow rate decreases and inlet temperature increases which would lead to local overheating in absorber and lower stress on quartz window.
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numerical simulation of solar radiation transmission process for the solar tower power plant from the heliostat field to the pressurized Volumetric Receiver
Applied Thermal Engineering, 2013Co-Authors: Ya-ling He, Ze-dong Cheng, Zengyao LiAbstract:Abstract In the present work, a concentrating and collecting subsystem optical model for the solar tower power plant is fully developed and the corresponding solar radiation transmission process from heliostat field to the pressurized Volumetric Receiver (PVR) is simulated by the in-house developed Monte Carlo Ray Tracing (MCRT) code. Based on the above model, the optical efficiency of heliostat field and the local heat flux distribution within the SiC absorber are calculated, and then the influences of time and date, Receiver mounting height and heliostats tracking error on the radiation transmission and absorption process are also investigated. The computation results show that, the heat flux distribution within the SiC absorber exhibits a great non-uniform characteristic, while the maximum heat flux density at the top area of the absorber is up to 2.58 × 109 W/m3. The variation tendencies of the field efficiency and the maximum heat flux density of the absorber are similar to that of the solar altitude angle during a day or a year. Furthermore, the annual mean field efficiency and the maximum heat flux of the absorber exhibit a rapid decreasing trend as the tracking error increases, but show a little increasing trend as the Receiver mounting height increases.
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numerical investigations on coupled heat transfer and synthetical performance of a pressurized Volumetric Receiver with mcrt fvm method
Applied Thermal Engineering, 2013Co-Authors: Ze-dong Cheng, Ya-ling HeAbstract:Abstract This paper presents an axisymmetric steady-state computational fluid dynamics model and further studies on the complex coupled heat transfer combined radiation–convection–conduction in the pressurized Volumetric Receiver (PVR), by combining the Finite Volume Method (FVM) and the Monte Carlo Ray-Trace (MCRT) method. Based on this, effects of geometric parameters of the compound parabolic concentrator (CPC) and properties of the porous absorber on synthetical characteristics and performance of the photo-thermal conversion process in the PVR are further analyzed and discussed detailedly. It is found that the solar flux density distributions are always very heterogeneous with large nonuniformities, and the variation trends of the corresponding temperature distributions are very similar to these but with much lower order of magnitude. The CPC shape determined by the CPC exit aperture has much larger effects on synthetical characteristics and performance of the PVR than that of the CPC entry aperture with a constant acceptance angle. And a suitable or optimal thickness of the porous absorber could be determined by examining where the drastic decreasing trends occur at the curves of variations of synthetical characteristics and performance with the porosity.
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Numerical investigations on coupled heat transfer and synthetical performance of a pressurized Volumetric Receiver with MCRT–FVM method
Applied Thermal Engineering, 2013Co-Authors: Ze-dong Cheng, Ya-ling HeAbstract:Abstract This paper presents an axisymmetric steady-state computational fluid dynamics model and further studies on the complex coupled heat transfer combined radiation–convection–conduction in the pressurized Volumetric Receiver (PVR), by combining the Finite Volume Method (FVM) and the Monte Carlo Ray-Trace (MCRT) method. Based on this, effects of geometric parameters of the compound parabolic concentrator (CPC) and properties of the porous absorber on synthetical characteristics and performance of the photo-thermal conversion process in the PVR are further analyzed and discussed detailedly. It is found that the solar flux density distributions are always very heterogeneous with large nonuniformities, and the variation trends of the corresponding temperature distributions are very similar to these but with much lower order of magnitude. The CPC shape determined by the CPC exit aperture has much larger effects on synthetical characteristics and performance of the PVR than that of the CPC entry aperture with a constant acceptance angle. And a suitable or optimal thickness of the porous absorber could be determined by examining where the drastic decreasing trends occur at the curves of variations of synthetical characteristics and performance with the porosity.
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numerical simulations of the solar transmission process for a pressurized Volumetric Receiver
Energy, 2012Co-Authors: Ya-ling He, Ze-dong Cheng, Dongchang LiAbstract:A three-dimensional optical model for a pressurized Volumetric Receiver (PVR) is developed and corresponding solar radiation propagation process within the PVR is simulated by the Monte Carlo Ray Tracing (MCRT) method. In the computation, the complicated photon transmission process in the SiC porous absorber is simplified as the transmission process in the statistically homogeneous and isotropic turbid medium. Meanwhile, the non-uniform cylindrical coordinate grid is applied in the statistics of energy distribution, which could greatly reduce the number of cells in the computational grid and time compared with normal uniform grid. Based on the above model, the energy distribution in the irregular macro scale porous absorber is determined and then the effects of system parameters, including the incidence angle, the shape of absorber and the optical property of absorber, on the local heat flux of the absorber are investigated. The results show that, under the given operating condition, the radiation heat flux is mostly concentrated at the top area of the absorber and the maximum heat flux value is up to 2.73 × 109 W m−3, but it quickly decreases in the sideward locations. The incidence angle and a relative narrow shape of absorber are helpful to reduce the maximum heat flux in the absorber. Furthermore, as the ratio of absorption coefficient/extinction coefficient decreases, the absorbed radiation energy distribution is more uniform and the max heat flux in the absorber decreases greatly.
J Sattler - One of the best experts on this subject based on the ideXlab platform.
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Development of a Transient Heat Recovery Steam Generator of the Solar Tower Power Plant Juelich
2020Co-Authors: Spiros Alexopoulos, Bernhard Hoffschmidt, Markus Latzke, J SattlerAbstract:This work describes the procedure of transient simulation for a hybridized solar tower power plant with open-Volumetric Receiver for a site in Northern Algeria. The simulation models have been developed in the simulation environment MATLAB/Simulink. The validation of the simulation tool against real plant data is presented in this work. Basic design calculations for the Algerian plant have been conducted on basis of meteorological data provided by satellites to investigate different concepts. For the concept that is most promising a transient annual simulation using local measured meteorological data has been conducted to yield detailed and accurate results. In addition, a parameter analysis of different thermal energy storage capacities has been carried out.
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transient simulation of a solar hybrid tower power plant with open Volumetric Receiver at the location barstow
Energy Procedia, 2014Co-Authors: Spiros Alexopoulos, Bernhard Hoffschmidt, G Breitbach, Markus Latzke, J SattlerAbstract:Abstract In this work the transient simulations of four hybrid solar tower power plant concepts with open-Volumetric Receiver technology for a location in Barstow-Daggett, USA, are presented. The open-Volumetric Receiver uses ambient air as heat transfer fluid and the hybridization is realized with a gas turbine. The Rankine cycle is heated by solar-heated air and/or by the gas turbine's flue gases. The plant can be operated in solar-only, hybrid parallel or combined cycle-only mode as well as in any intermediate load levels where the solar portion can vary between 0 to 100%. The simulated plant is based on the configuration of a solar-hybrid power tower project, which is in planning for a site in Northern Algeria. The meteorological data for Barstow-Daggett was taken from the software meteonorm. The solar power tower simulation tool has been developed in the simulation environment MATLAB/Simulink and is validated.
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high temperature thermal storage system for solar tower power plants with open Volumetric air Receiver simulation and energy balancing of a discretized model
Energy Procedia, 2014Co-Authors: Valentina Kronhardt, Bernhard Hoffschmidt, Spiros Alexopoulos, J Sattler, M Reisel, Matthias Hanel, Till DoerbeckAbstract:Abstract This paper describes the modeling of a high-temperature storage system for an existing solar tower power plant with open Volumetric Receiver technology, which uses air as heat transfer medium (HTF). The storage system model has been developed in the simulation environment Matlab/Simulink ® . The storage type under investigation is a packed bed thermal energy storage system which has the characteristics of a regenerator. Thermal energy can be stored and discharged as required via the HTF air. The air mass flow distribution is controlled by valves, and the mass flow by two blowers. The thermal storage operation strategy has a direct and significant impact on the energetic and economic efficiency of the solar tower power plants.
Evelyn N Wang - One of the best experts on this subject based on the ideXlab platform.
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Optimization of nanofluid Volumetric Receivers for solar thermal energy conversion
Solar Energy, 2012Co-Authors: Andrej Lenert, Evelyn N WangAbstract:Improvements in solar-to-thermal energy conversion will accelerate the development of efficient concentrated solar power systems. Nanofluid Volumetric Receivers, where nanoparticles in a liquid medium directly absorb solar radiation, promise increased performance over surface Receivers by minimizing temperature differences between the absorber and the fluid, which consequently reduces emissive losses. We present a combined modeling and experimental study to optimize the efficiency of liquid-based solar Receivers seeded with carbon-coated absorbing nanoparticles. A one-dimensional transient heat transfer model was developed to investigate the effect of solar concentration, nanofluid height, and optical thickness on Receiver performance. Simultaneously, we experimentally investigated a cylindrical nanofluid Volumetric Receiver, and showed good agreement with the model for varying optical thicknesses of the nanofluid. Based on the model, the efficiency of nanofluid Volumetric Receivers increases with increasing solar concentration and nanofluid height. Receiver-side efficiencies are predicted to exceed 35% when nanofluid Volumetric Receivers are coupled to a power cycle and optimized with respect to the optical thickness and solar exposure time. This work provides insights as to how nanofluids can be best utilized as Volumetric Receivers in solar applications, such as Receivers with integrated storage for beam-down CSP and future high concentration solar thermal energy conversion systems. © 2011 Elsevier Ltd.
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optimization of nanofluid Volumetric Receivers for solar thermal energy conversion
Solar Energy, 2012Co-Authors: Andrej Lenert, Evelyn N WangAbstract:Abstract Improvements in solar-to-thermal energy conversion will accelerate the development of efficient concentrated solar power systems. Nanofluid Volumetric Receivers, where nanoparticles in a liquid medium directly absorb solar radiation, promise increased performance over surface Receivers by minimizing temperature differences between the absorber and the fluid, which consequently reduces emissive losses. We present a combined modeling and experimental study to optimize the efficiency of liquid-based solar Receivers seeded with carbon-coated absorbing nanoparticles. A one-dimensional transient heat transfer model was developed to investigate the effect of solar concentration, nanofluid height, and optical thickness on Receiver performance. Simultaneously, we experimentally investigated a cylindrical nanofluid Volumetric Receiver, and showed good agreement with the model for varying optical thicknesses of the nanofluid. Based on the model, the efficiency of nanofluid Volumetric Receivers increases with increasing solar concentration and nanofluid height. Receiver-side efficiencies are predicted to exceed 35% when nanofluid Volumetric Receivers are coupled to a power cycle and optimized with respect to the optical thickness and solar exposure time. This work provides insights as to how nanofluids can be best utilized as Volumetric Receivers in solar applications, such as Receivers with integrated storage for beam-down CSP and future high concentration solar thermal energy conversion systems.
Spiros Alexopoulos - One of the best experts on this subject based on the ideXlab platform.
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Modelling and validation of a transient heat recovery steam generator of the solar tower plant juelich
2020Co-Authors: Spiros Alexopoulos, Bernhard Hoffschmidt, G Breitbach, Markus LatzkeAbstract:Germany’s first and only solar tower power plant for experimental and demonstration purposes has been erected in the town of Julich, North-Rhine-Westphalia. The central Receiver plant, which has been designed with an open-Volumetric Receiver, supplies the grid with a nominal power of 1.5 MWe. Through the open-Volumetric Receiver ambient air is drawn in and due to the concentration high temperatures from 600°C to 800°C can be achieved. These temperatures are in a range to fire a heat recovery steam generator (HRSG) that produces steam in a conventional water-steam-cycle. The presented work describes the development of a transient heat recovery steam generator (HRSG) in the simulation environment MATLAB/Simulink. The implemented simulation model has been validated by comparing the computed results with real performance data of the solar tower power plant Julich. The results show that the model can describe the transient behaviour in a exact way. Additionally, the preciseness of the model could be validated by a deviation less than 9%. The developed HRSG model is integrated in a simulation tool that models the whole power plant. With this simulation tool the annual electricity production of different plant configurations at various sites can be computed as well as optimised plant operations investigated and developed.
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Development of a Transient Heat Recovery Steam Generator of the Solar Tower Power Plant Juelich
2020Co-Authors: Spiros Alexopoulos, Bernhard Hoffschmidt, Markus Latzke, J SattlerAbstract:This work describes the procedure of transient simulation for a hybridized solar tower power plant with open-Volumetric Receiver for a site in Northern Algeria. The simulation models have been developed in the simulation environment MATLAB/Simulink. The validation of the simulation tool against real plant data is presented in this work. Basic design calculations for the Algerian plant have been conducted on basis of meteorological data provided by satellites to investigate different concepts. For the concept that is most promising a transient annual simulation using local measured meteorological data has been conducted to yield detailed and accurate results. In addition, a parameter analysis of different thermal energy storage capacities has been carried out.
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transient simulation of a solar hybrid tower power plant with open Volumetric Receiver at the location barstow
Energy Procedia, 2014Co-Authors: Spiros Alexopoulos, Bernhard Hoffschmidt, G Breitbach, Markus Latzke, J SattlerAbstract:Abstract In this work the transient simulations of four hybrid solar tower power plant concepts with open-Volumetric Receiver technology for a location in Barstow-Daggett, USA, are presented. The open-Volumetric Receiver uses ambient air as heat transfer fluid and the hybridization is realized with a gas turbine. The Rankine cycle is heated by solar-heated air and/or by the gas turbine's flue gases. The plant can be operated in solar-only, hybrid parallel or combined cycle-only mode as well as in any intermediate load levels where the solar portion can vary between 0 to 100%. The simulated plant is based on the configuration of a solar-hybrid power tower project, which is in planning for a site in Northern Algeria. The meteorological data for Barstow-Daggett was taken from the software meteonorm. The solar power tower simulation tool has been developed in the simulation environment MATLAB/Simulink and is validated.
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high temperature thermal storage system for solar tower power plants with open Volumetric air Receiver simulation and energy balancing of a discretized model
Energy Procedia, 2014Co-Authors: Valentina Kronhardt, Bernhard Hoffschmidt, Spiros Alexopoulos, J Sattler, M Reisel, Matthias Hanel, Till DoerbeckAbstract:Abstract This paper describes the modeling of a high-temperature storage system for an existing solar tower power plant with open Volumetric Receiver technology, which uses air as heat transfer medium (HTF). The storage system model has been developed in the simulation environment Matlab/Simulink ® . The storage type under investigation is a packed bed thermal energy storage system which has the characteristics of a regenerator. Thermal energy can be stored and discharged as required via the HTF air. The air mass flow distribution is controlled by valves, and the mass flow by two blowers. The thermal storage operation strategy has a direct and significant impact on the energetic and economic efficiency of the solar tower power plants.
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transient simulation for hybrid solar tower power plant with open Volumetric Receiver in algeria
2012Co-Authors: Spiros Alexopoulos, Gerrit Koll, Bernhard Hoffschmidt, G Breitbach, Till Doerbeck, Tahar SahraouiAbstract:This work describes the procedure of transient simulation for a solar tower power plant with open-Volumetric Receiver for a site in Northern Algeria. The simulation models have been developed in the simulation environment MATLAB/Simulink. Basic design calculations have been conducted on basis of meteorological data provided by satellites to investigate different concepts. For the concept that is most auspicious a transient annual simulation using local measured meteorological data has been conducted to yield detailed and accurate results.
