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Hadrien Benoit - One of the best experts on this subject based on the ideXlab platform.
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Particle motion and heat transfer in an upward-flowing dense Particle Suspension: Application in solar receivers
Chemical Engineering Science, 2017Co-Authors: Pablo García-triñanes, Hadrien Benoit, Renaud Ansart, Jonathan Seville, Thomas Leadbeater, David ParkerAbstract:Concentrated solar power (CSP) plants conventionally make use of molten salt as the heat transfer medium, which transfers heat between the solar receiver and a steam turbine power circuit. A new approach uses Particles of a heat-resistant particulate medium in the form of many dense upward-moving fluidised beds contained within an array of vertical tubes within the solar receiver. In most dense gas–solid fluidisation systems, Particle circulation is induced by bubble motion and is the primary cause of Particle convective heat transfer,which is themajor contributing mechanismto overall heat transfer. The current work describes experiments designed to investigate the relationship between this solids convection and the heat transfer coefficient between the bed and the tubewall, which is shown to depend on the local Particle concentration and their rate of renewal at the wall. Experimentswere performed using 65 mmsilicon carbide Particles in a tube of diameter 30mm, replicating the conditions used in the real application. Solidsmotion and time-averaged solids concentration were measured using Positron Emission Particle Tracking (PEPT) and local heat transfer coefficients measured using small probes which employ electrical resistance heating and thermocouple temperaturemeasurement. Results show that, as for other types of bubbling beds, the heat transfer coefficient first increases as the gas flow rate increases (because the rate of Particle renewal at thewall increases), before passing through a maximum and decreasing again as the reducing local solids concentration at the wall becomes the dominant effect. Measured heat transfer coefficients are compared with theoretical approaches by Mickley and Fairbanks packet model and Thring correlation. The close correspondence between heat transfer coefficient and solids movement is here demonstrated by PEPT for the first time in a dense upward-moving fluidised bed.
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heat exchanger modelling in central receiver solar power plant using dense Particle Suspension
SOLARPACES 2016: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2017Co-Authors: M A Reyesbelmonte, Hadrien Benoit, Manuel Romero, Jose Gonzalezaguilar, Fabrisio Gomezgarcia, Gilles FlamantAbstract:In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense Particle Suspension (DPS) as heat transfer fluid (HTF) in the solar loop and water-steam as working fluid is presented. HX modelling is based on fluidized bed (FB) technology and its design has been conceived to couple solar plant using DPS as HTF and storage media with Rankine cycle for power generation. Using DPS as heat transfer fluid allows extending operating temperature range what will help to reduce thermal energy storage costs favoring higher energy densities but will also allow running power cycle at higher temperature what will increase its efficiency. Besides HX modelling description, this model will be used to reproduce solar plant performance under steady state and transient conditions.
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Dense gas-Particle Suspension upward flow used as heat transfer fluid in solar receiver: PEPT experiments and 3D numerical simulations
Powder Technology, 2017Co-Authors: Renaud Ansart, Hadrien Benoit, Benjamin Boissière, Pablo García-triñanes, Jonathan Seville, Olivier SimoninAbstract:A dense Particle Suspension, also called an upflow bubbling fluidized bed, is an innovative alternative to the heat transfer fluids commonly used in concentrated solar power plants. An additional advantage of this technology is that it allows for direct thermal storage due to the large heat capacity and maximum temperature of the Particle Suspension. The key to the proposed process is the effective heat transfer from the solar heated surfaces to the heat transfer fluid, i.e. the circulating solid Suspension. In order to better understand the process and to optimise the design of the solar receiver, it is of paramount importance to know how Particles behave inside the bundle of small tubes. To access to the Particle motion in the solar receiver, two different techniques are carried out: experimental using positron emission Particle tracking (PEPT) and 3D numerical simulation via an Eulerian n-fluid approach with NEPTUNE_CFD code. Both numerical predictions and PEPT measurements describe an upward flow at the centre of the transport tube with a back-mixing flow near the wall which influences the heat transfer mechanism. Comparisons between experiment and computation were carried out for the radial profiles of the solid volume fraction, and vertical and radial time-averaged and variance velocities of solid, and demonstrating the capability of NEPTUNE_CFD code to simulate this peculiar upflow bubbling fluidized bed.
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temperature influence on wall to Particle Suspension heat transfer in a solar tubular receiver
SOLARPACES 2015: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2016Co-Authors: Hadrien Benoit, Inmaculada Pérez López, Daniel J Gauthier, Gilles FlamantAbstract:Dense Particle Suspension (DPS) can be used as high temperature heat transfer fluid in solar receiver. Tests conducted with a one-tube experimental setup in real conditions of concentrated solar irradiation resulted in determining heat transfer coefficients for the DPS flowing upward in a vertical tube. They have been obtained for solid fluxes in the range 10-45 kg/m2.s and outlet temperatures up to 1020 K. The influence of solid flux, aeration and temperature is outlined in this paper. Heat transfer coefficient variations are correlated as a function of the solid flux and the temperature for given aeration conditions.
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On-sun operation of a 150 kWth pilot solar receiver using dense Particle Suspension as heat transfer fluid
Solar Energy, 2016Co-Authors: Inmaculada Pérez López, Hadrien Benoit, Daniel Gauthier, Gilles FlamantAbstract:Previous studies proved the Dense Particle Suspension (DPS) - also called Upward Bubbling Fluidized Bed (UBFB) - could be used as Heat Transfer Fluid (HTF) in a single-tube solar receiver. This article describes the experiments conducted on a 16-tube, 150 kWth solar receiver using a dense gas-Particle Suspension (around 30% solid volume fraction) flowing upward as HTF. The receiver was part of a whole pilot setup that allowed the continuous closed-loop circulation of the SiC Particles used as HTF. One hundred hours of on-sun tests were performed at the CNRS 1 MW solar furnace in Odeillo. The pilot was tested under various ranges of operating parameters: solid mass flow rate (660–1760 kg/h), input solar power (60–142 kW), and Particle temperature before entering the solar receiver (40–180 °C). Steady states were reached during the experiments, with continuous circulation and constant Particle temperatures. For the hottest case, the mean Particle temperature reached 430 °C in the collector fluidized bed, at the receiver outlet, and it went up to 700 °C at the outlet of the hottest tube, during steady operation. A temperature difference between tubes is observed that is mainly due to the incident solar flux distribution heterogeneity. The thermal efficiency of the receiver, defined as the ratio of power transmitted to the DPS in the form of heat over solar power entering the receiver cavity, was calculated in the range 50–90% for all the experimental cases. The system transient responses to variations of the solar irradiation and of the solid mass flow rate are also reported.
Shane Ardo - One of the best experts on this subject based on the ideXlab platform.
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evaluating Particle Suspension reactor designs for z scheme solar water splitting via transport and kinetic modeling
Energy and Environmental Science, 2018Co-Authors: Rohini Bala Chandran, Shane Ardo, Sasuke Breen, Yuanxun Shao, Adam Z WeberAbstract:Sunlight-driven water splitting to produce hydrogen and oxygen provides a pathway to store available solar energy in the form of stable, energy-dense chemical bonds. Here we investigate a tandem Particle-Suspension reactor design for solar water splitting comprising micron-scale photocatalyst Particles suspended in an aqueous solution with soluble redox shuttles. A porous separator facilitates redox species transport between the hydrogen and oxygen evolution reaction compartments while averting gas crossover. A two-dimensional, transient model of the reactor is presented to illustrate the coupling between light absorption, interfacial electron-transfer kinetics and species transport, and their combined impacts on overall solar-to-hydrogen conversion efficiency. The volumetric reactivity of the suspended semiconductor Particles is dictated by combining the (photo)current–voltage behavior of a photodiode with Butler–Volmer electron-transfer kinetics. For the first time, a quantitative approach to determine the impacts of surface-dependent redox shuttle kinetic parameters on reaction selectivity in a Z-scheme system is established. Model results provide insights on the effects of optical, transport and kinetic properties of the semiconductor Particles and the redox shuttles on the overall reactor performance. Solar-to-hydrogen reactor efficiencies predicted with BiVO4 Particles for oxygen evolution are at least two times larger than efficiencies achieved with wider band-gap TiO2 Particles due to enhanced visible light absorption; hydrogen evolution with SrTiO3:Rh Particles was considered for both cases. Superior performance is predicted with proton-coupled electron transfer redox shuttles (para-benzoquinone/hydroquinone and iodide/iodate) that absorb little-to-no visible light, while also facilitating operation at near-neutral pH conditions, as compared to the non-proton-coupled triiodide/iodide and iron(III)/iron(II) redox shuttles. For 1 cm tall reaction compartments, diffusive species transport is fast enough to sustain reactor operation at a 1% solar-to-hydrogen conversion efficiency for both para-benzoquinone/hydroquinone and iodate/iodide redox shuttles with less than 2.2 mg L−1 of each of BiVO4 and SrTiO3:Rh Particles in the solution.
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Particle Suspension reactors and materials for solar driven water splitting
Energy and Environmental Science, 2015Co-Authors: David M Fabian, Nirala Singh, Frances A Houle, Takashi Hisatomi, Kazunari Domen, Frank E Osterloh, Shane ArdoAbstract:Reactors based on Particle Suspensions for the capture, conversion, storage, and use of solar energy as H2 are projected to be cost-competitive with fossil fuels. In light of this, this review paper summarizes state-of-the-art Particle light absorbers and cocatalysts as Suspensions (photocatalysts) that demonstrate visible-light-driven water splitting on the laboratory scale. Also presented are reactor descriptions, theoretical considerations particular to Particle Suspension reactors, and efficiency and performance characterization metrics. Opportunities for targeted research, analysis, and development of reactor designs are highlighted.
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Technical and economic feasibility of centralized facilities for solar hydrogen production via photocatalysis and photoelectrochemistry
Energy and Environmental Science, 2013Co-Authors: Blaise A. Pinaud, Brian D. James, Kevin N. Baum, George N. Baum, Zhebo Chen, Todd G Deutsch, Arnold J. Forman, Linsey C Seitz, Jesse D Benck, Shane ArdoAbstract:Photoelectrochemical water splitting is a promising route for the renewable production of hydrogen fuel. This work presents the results of a technical and economic feasibility analysis conducted for four hypothetical, centralized, large-scale hydrogen production plants based on this technology. The four reactor types considered were a single bed Particle Suspension system, a dual bed Particle Suspension system, a fixed panel array, and a tracking concentrator array. The current performance of semiconductor absorbers and electrocatalysts were considered to compute reasonable solar-to-hydrogen conversion efficiencies for each of the four systems. The U.S. Department of Energy H2A model was employed to calculate the levelized cost of hydrogen output at the plant gate at 300 psi for a 10 tonne per day production scale. All capital expenditures and operating costs for the reactors and auxiliaries (compressors, control systems, etc.) were considered. The final cost varied from $1.60-$10.40 per kg H2 with the Particle bed systems having lower costs than the panel-based systems. However, safety concerns due to the cogeneration of O2 and H2 in a single bed system and long molecular transport lengths in the dual bed system lead to greater uncertainty in their operation. A sensitivity analysis revealed that improvement in the solar-to-hydrogen efficiency of the panel-based systems could substantially drive down their costs. A key finding is that the production costs are consistent with the Department of Energy's targeted threshold cost of $2.00-$4.00 per kg H2 for dispensed hydrogen, demonstrating that photoelectrochemical water splitting could be a viable route for hydrogen production in the future if material performance targets can be met.
Gilles Flamant - One of the best experts on this subject based on the ideXlab platform.
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heat exchanger modelling in central receiver solar power plant using dense Particle Suspension
SOLARPACES 2016: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2017Co-Authors: M A Reyesbelmonte, Hadrien Benoit, Manuel Romero, Jose Gonzalezaguilar, Fabrisio Gomezgarcia, Gilles FlamantAbstract:In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense Particle Suspension (DPS) as heat transfer fluid (HTF) in the solar loop and water-steam as working fluid is presented. HX modelling is based on fluidized bed (FB) technology and its design has been conceived to couple solar plant using DPS as HTF and storage media with Rankine cycle for power generation. Using DPS as heat transfer fluid allows extending operating temperature range what will help to reduce thermal energy storage costs favoring higher energy densities but will also allow running power cycle at higher temperature what will increase its efficiency. Besides HX modelling description, this model will be used to reproduce solar plant performance under steady state and transient conditions.
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temperature influence on wall to Particle Suspension heat transfer in a solar tubular receiver
SOLARPACES 2015: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2016Co-Authors: Hadrien Benoit, Inmaculada Pérez López, Daniel J Gauthier, Gilles FlamantAbstract:Dense Particle Suspension (DPS) can be used as high temperature heat transfer fluid in solar receiver. Tests conducted with a one-tube experimental setup in real conditions of concentrated solar irradiation resulted in determining heat transfer coefficients for the DPS flowing upward in a vertical tube. They have been obtained for solid fluxes in the range 10-45 kg/m2.s and outlet temperatures up to 1020 K. The influence of solid flux, aeration and temperature is outlined in this paper. Heat transfer coefficient variations are correlated as a function of the solid flux and the temperature for given aeration conditions.
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On-sun operation of a 150 kWth pilot solar receiver using dense Particle Suspension as heat transfer fluid
Solar Energy, 2016Co-Authors: Inmaculada Pérez López, Hadrien Benoit, Daniel Gauthier, Gilles FlamantAbstract:Previous studies proved the Dense Particle Suspension (DPS) - also called Upward Bubbling Fluidized Bed (UBFB) - could be used as Heat Transfer Fluid (HTF) in a single-tube solar receiver. This article describes the experiments conducted on a 16-tube, 150 kWth solar receiver using a dense gas-Particle Suspension (around 30% solid volume fraction) flowing upward as HTF. The receiver was part of a whole pilot setup that allowed the continuous closed-loop circulation of the SiC Particles used as HTF. One hundred hours of on-sun tests were performed at the CNRS 1 MW solar furnace in Odeillo. The pilot was tested under various ranges of operating parameters: solid mass flow rate (660–1760 kg/h), input solar power (60–142 kW), and Particle temperature before entering the solar receiver (40–180 °C). Steady states were reached during the experiments, with continuous circulation and constant Particle temperatures. For the hottest case, the mean Particle temperature reached 430 °C in the collector fluidized bed, at the receiver outlet, and it went up to 700 °C at the outlet of the hottest tube, during steady operation. A temperature difference between tubes is observed that is mainly due to the incident solar flux distribution heterogeneity. The thermal efficiency of the receiver, defined as the ratio of power transmitted to the DPS in the form of heat over solar power entering the receiver cavity, was calculated in the range 50–90% for all the experimental cases. The system transient responses to variations of the solar irradiation and of the solid mass flow rate are also reported.
Jose Gonzalezaguilar - One of the best experts on this subject based on the ideXlab platform.
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heat exchanger modelling in central receiver solar power plant using dense Particle Suspension
SOLARPACES 2016: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2017Co-Authors: M A Reyesbelmonte, Hadrien Benoit, Manuel Romero, Jose Gonzalezaguilar, Fabrisio Gomezgarcia, Gilles FlamantAbstract:In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense Particle Suspension (DPS) as heat transfer fluid (HTF) in the solar loop and water-steam as working fluid is presented. HX modelling is based on fluidized bed (FB) technology and its design has been conceived to couple solar plant using DPS as HTF and storage media with Rankine cycle for power generation. Using DPS as heat transfer fluid allows extending operating temperature range what will help to reduce thermal energy storage costs favoring higher energy densities but will also allow running power cycle at higher temperature what will increase its efficiency. Besides HX modelling description, this model will be used to reproduce solar plant performance under steady state and transient conditions.
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preliminary design and performance analysis of a multi megawatt scale dense Particle Suspension receiver
Energy Procedia, 2015Co-Authors: Alessandro Gallo, James Spelling, Manuel Romero, Jose GonzalezaguilarAbstract:Abstract A novel receiver concept is presented, based on the use of a dense Particle Suspension as the heat transfer medium; this medium allows receiver operation at high temperatures (above 650 °C), resulting in significant gains in power plant efficiency. A 10 MW th receiver has been designed based on the scale-up of a 150 kW th prototype currently undergoing testing. The predicted thermal efficiency is 81.3%, well above the design target of 70%. Material temperatures within the absorber tubes were maintained below 850 °C throughout the receiver, below the limits of high temperature steels.
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a high efficiency solar thermal power plant using a dense Particle Suspension as the heat transfer fluid
Energy Procedia, 2015Co-Authors: James Spelling, Alessandro Gallo, Manuel Romero, Jose GonzalezaguilarAbstract:Abstract A novel solar power plant concept is presented, based on the use of a dense Particle Suspension as the heat transfer fluid which allows receiver operation at high temperatures (above 650 °C), opening the possibility of using high-efficiency power generation cycles such as supercritical Rankine cycles. A 50 MW e solar power plant was designed based on this new heat transfer fluid and compared with a conventional molten salt solar power plant. The supercritical Rankine-cycle power block increases the thermal conversion efficiency from 39.9% to 45.4%, corresponding to a 9.6% reduction in the size of the heliostat field. The operating temperature range is increased by 24.5%, which leads to a 12.5% increase in storage density and a 22.5% reduction in the total storage volume.Parasitic power consumption is also reduced due to the elimination of the need for heat tracing. Overall, the combination of increased cycle efficiency, increased storage density and reduced parasitics to leads to a predicted electricity cost reduction of 10.8%.
Aldo Steinfeld - One of the best experts on this subject based on the ideXlab platform.
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a numerical investigation of gas Particle Suspensions as heat transfer media for high temperature concentrated solar power
International Journal of Heat and Mass Transfer, 2015Co-Authors: Jan Marti, Andreas Haselbacher, Aldo SteinfeldAbstract:Abstract This paper investigates the detailed heat-transfer mechanisms in dense gas-Particle Suspensions used as heat transfer media for high-temperature concentrated solar power applications. A two-phase Euler–Euler model for dense gas-Particle systems is built on the open-source code OpenFOAM. The model is capable of predicting the complex hydrodynamic behavior of bubble formation, coalescence, and breakup together with conduction, convection, and radiation heat transfer. At each time step, the model calculates the effective radiative properties as a function of the local solid volume fraction. Therefore, the model captures radiation penetrating through gas bubbles near the riser wall and radiation being absorbed within a few millimeters by the dense gas-Particle Suspension. Comparisons with on-sun experimental results indicate that the model accurately predicts coupled hydrodynamics and heat transfer in dense gas-Particle systems. The model is used to investigate the heat-transfer mechanisms in a slowly rising, dense gas-Particle Suspension located in a directly irradiated riser tube. The majority of the heat transfer takes place within a distance of a few Particle diameters from the heated riser wall. In this region, the Particles are heated by solid conduction and heat is then transferred by solid convection to the colder flow in the center of the riser. It is shown that with a moderate riser wall temperature of 581 K and a Particle diameter of 64 μm, solid conduction accounts for about 97% of the wall-to-Suspension heat flux. Increasing the wall temperature to 981 K together with a Particle diameter of 400 μm leads to an increase of the radiation heat-flux contribution up to about 10% of the total wall-to-Suspension heat flux.
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experimental determination of the radiative properties of Particle Suspensions for high temperature solar receiver applications
Heat Transfer Engineering, 2014Co-Authors: Jan Marti, Matthew Roesle, Aldo SteinfeldAbstract:This study combines experimental measurements with a numerical method to determine the effective radiative properties of Particle Suspensions. A spectroscopic goniometry system is applied to measure the attenuation and angular radiation distribution of irradiated samples produced by uniformly suspending Particles within a transparent epoxy resin. Samples of varying porosity and thickness are examined. A collision-based Monte Carlo model is formulated for a continuous participating medium representing the Particle Suspension. The volume-averaged radiative properties, namely, the extinction coefficient, the scattering albedo, and the scattering phase function, are determined for porosities between 0.72 and 0.95 by fitting to the experimental data. Extended correlations of the independent scattering theory show good match with the experimental determined extinction coefficient and capture the dependent scattering effect. The modified double Henyey–Greenstein scattering phase function yields the best agreemen...
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radiative transfer in a solar chemical reactor for the co production of hydrogen and carbon by thermal decomposition of methane
Chemical Engineering Science, 2004Co-Authors: David Hirsch, Aldo SteinfeldAbstract:Abstract Radiation heat transfer in a solar chemical reactor for the co-production of hydrogen and carbon by thermal decomposition of CH 4 is analyzed by the Monte Carlo ray-tracing method. The solar chemical reactor features a vortex flow of CH 4 confined to a cavity and laden with carbon Particles that serve simultaneously as radiant absorbers and nucleation sites for the heterogeneous decomposition reaction. The reactor is treated as a 3D non-isothermal non-gray absorbing–emitting–scattering gas/Particle Suspension directly exposed to concentrated solar irradiation. The analysis includes coupling to conduction/convection heat transfer and chemical kinetics. Calculated temperature distribution and chemical conversion are compared with the experimentally measured values obtained with a 5 kW prototype reactor tested in a solar furnace.