The Experts below are selected from a list of 11589 Experts worldwide ranked by ideXlab platform
Aldo Steinfeld - One of the best experts on this subject based on the ideXlab platform.
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a cavity receiver containing a tubular absorber for high temperature Thermochemical Processing using concentrated solar energy
International Journal of Thermal Sciences, 2008Co-Authors: Tom Melchior, Aldo Steinfeld, Christopher Perkins, Alan W WeimerAbstract:A solar chemical reactor consisting of a cylindrical cavity-receiver containing a tubular ceramic absorber is considered for performing Thermochemical Processes using concentrated solar radiation as the energy source of high-temperature Process heat. The model chemical reaction selected is the thermal dissociation of ZnO into its elements, which proceeds endothermically at above 1800 K and is part of a 2-step H2O-splitting Thermochemical cycle for H2 production. A lab-scale 5 kW reactor prototype is fabricated and subjected to high-flux solar irradiation in the range 448–2125 kW/m2. A heat transfer reactor model is formulated that encompasses the governing mass and energy conservation equations coupling radiation/convection/conduction heat transfer to the chemical kinetics, and their solution by Monte Carlo ray-tracing and finite difference techniques. Validation was accomplished by comparing numerically computed and experimentally measured temperatures and reaction rates in the 1780–1975 K range. The reactor model is further applied to simulate a continuous Thermochemical Process, identify major sources of irreversibility, and predict solar-to-chemical energy conversion efficiencies.
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solar hydrogen production via a two step Thermochemical Process based on mgo mg redox reactions thermodynamic and kinetic analyses
International Journal of Hydrogen Energy, 2008Co-Authors: Maria Elena Galvez, A Frei, G Albisetti, G Lunardi, Aldo SteinfeldAbstract:Abstract Solar hydrogen production via a two-step water-splitting Thermochemical cyclic Process is considered via MgO/Mg redox reactions. The first endothermic step is the production of Mg by carbothermal or methanothermal reduction of MgO, using concentrated solar energy as the source of high-temperature Process heat. The second exothermic step is the steam-hydrolysis of Mg for the production of H 2 and MgO; the latter is recycled to the first step. Both reaction steps have been thermodynamically examined and experimentally investigated by means of thermogravimetric analysis. The carbothermal reduction of MgO was performed in the temperature range 1450–1550 °C using wood charcoal and petroleum coke as reducing agents. The steam-hydrolysis of Mg was studied in the temperature range 350–550 °C using various water vapor concentrations. Solid products were characterized via BET, XRD, and SEM. The rate laws of both reaction steps were determined by applying either a solid–solid diffusion kinetic model or the gas–solid shrinking core kinetic model.
R.c. Bindal - One of the best experts on this subject based on the ideXlab platform.
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tantalum membrane reactor for enhanced hi decomposition in iodine sulphur is Thermochemical Process of hydrogen production
International Journal of Hydrogen Energy, 2017Co-Authors: Bharat Bhushan, Nitesh Goswami, S.c. Parida, Amit K. Singha, B.n. Rath, H.s. Sodaye, R.c. BindalAbstract:Abstract HI decomposition reaction in Iodine–Sulphur (IS) Thermochemical Process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion. Metallic membrane reactor is proposed to be a Process intensification tool that can enable efficient HI decomposition by overcoming the equilibrium limitation of the reaction. In this study, we report the fabrication and characterization of clay alumina supported tantalum (Ta) membrane and its application in packed bed catalytic membrane reactor for HI decomposition section of IS Process for the first time. The alumina tubes were coated with thin film of Ta metal of thickness 2.5 μm using DC sputter deposition technique under the optimum set of parameters. The membranes were found to remain stable upto 200 Hrs of exposure under HI-H2O environment at 125 °C. Modeling of a packed bed Ta membrane reactor for HI decomposition was carried out to find out the optimum operating parameters of the membrane reactor to get a conversion of at least 95%. A packed bed membrane reactor (PBMR) assembly was fabricated with integration of the in-house synthesized Ta membrane and Pt-alumina catalyst for carrying out HI decomposition studies at 450 °C. The tube side was chosen as permeation zone and the shell side as the reaction zone. A single-pass conversion of 94.7% of HI to hydrogen was obtained by employing Ta metal membrane reactor against the theoretical equilibrium conversion value of 22%. The findings showed that Ta-based PBMR shall offer a potential benefit to reach higher efficiency of IS Thermochemical Process.
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Tantalum membrane reactor for enhanced HI decomposition in Iodine–Sulphur (IS) Thermochemical Process of hydrogen production
International Journal of Hydrogen Energy, 2017Co-Authors: Bharat Bhushan, Nitesh Goswami, S.c. Parida, Amit K. Singha, B.n. Rath, H.s. Sodaye, R.c. Bindal, Soumitra KarAbstract:Abstract HI decomposition reaction in Iodine–Sulphur (IS) Thermochemical Process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion. Metallic membrane reactor is proposed to be a Process intensification tool that can enable efficient HI decomposition by overcoming the equilibrium limitation of the reaction. In this study, we report the fabrication and characterization of clay alumina supported tantalum (Ta) membrane and its application in packed bed catalytic membrane reactor for HI decomposition section of IS Process for the first time. The alumina tubes were coated with thin film of Ta metal of thickness 2.5 μm using DC sputter deposition technique under the optimum set of parameters. The membranes were found to remain stable upto 200 Hrs of exposure under HI-H2O environment at 125 °C. Modeling of a packed bed Ta membrane reactor for HI decomposition was carried out to find out the optimum operating parameters of the membrane reactor to get a conversion of at least 95%. A packed bed membrane reactor (PBMR) assembly was fabricated with integration of the in-house synthesized Ta membrane and Pt-alumina catalyst for carrying out HI decomposition studies at 450 °C. The tube side was chosen as permeation zone and the shell side as the reaction zone. A single-pass conversion of 94.7% of HI to hydrogen was obtained by employing Ta metal membrane reactor against the theoretical equilibrium conversion value of 22%. The findings showed that Ta-based PBMR shall offer a potential benefit to reach higher efficiency of IS Thermochemical Process.
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the application of membrane reactor technology in hydrogen production using s i Thermochemical Process a roadmap
International Journal of Hydrogen Energy, 2012Co-Authors: Soumitra Kar, R.c. Bindal, S Prabhakar, P K TewariAbstract:Abstract Thermochemical cycle using water as raw material and nuclear/renewable energies as sources of energy is believed to be a safe, stable and sustainable route of hydrogen production. Amongst the well-studied Thermochemical cycles, the sulfur–iodine (S–I) cycle is capable of achieving an energy efficiency of 50%, making it one of the most efficient cycles among all water-splitting Processes. The SI cycle is characterized by three basic reactions as shown below. 1. I 2 + SO 2 + 2H 2 O → 2HI x + H 2 SO 4 (120 °C) 2. 2H 2 SO 4 → 2SO 2 + 2H 2 O + O 2 (830 °C) 3. 2HI x → I 2 + H 2 (450 °C) The third section, that is the HI x (HI + I 2 + H 2 O) Processing section, is the most intricate step in terms of the Process efficiency as it has got the lowest overall rate and very complicated separations. In order to overcome the low efficiency due to the poor equilibrium decomposition of HI, ongoing research is dedicated toward development of a hydrogen-permselective membrane reactor. Proper identification of suitable membranes and introduction of membrane reactor is proposed to improve the efficiency of the overall cycle and make hydrogen production more economical. The experimental procedure has already been optimized toward development of an asymmetric silica membrane. The authors presently intend to use the membrane in the form of a packed bed membrane reactor for the enhancement of equilibrium decomposition of HI. The present paper discusses the challenges and intricacies associated toward development of a membrane reactor which can be applied in highly corrosive environment like HI under a high temperature of about 500 °C.
Driss Stitou - One of the best experts on this subject based on the ideXlab platform.
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definition and performance simulations of a novel solar driven hybrid absorption Thermochemical refrigeration system
Energy Conversion and Management, 2018Co-Authors: Alberto Coronas, Jaume Fito, Sylvain Mauran, Nathalie Mazet, Driss StitouAbstract:Abstract This paper proposes a novel hybrid refrigeration system with energy storage, driven by low-grade solar heat and consisting of a single-stage absorption cycle coupled with a Thermochemical Process by sharing the same condenser, evaporator and refrigerant fluid. A first screening of ammonia-based working pairs for evaporation temperatures of −10 °C, condensation temperatures of 30 °C and heat source temperatures of 80 °C reveals LiNO 3 as suitable sorbent salt for the absorption subsystem, and BaCl 2 , PbBr 2 , SrCl 2 , LiCl, NH 4 Br and SnCl 2 as candidate reactive salts in the Thermochemical subsystem. The subsequent parametric study indicates that the absorption subsystem with NH 3 /LiNO 3 reaches close-to-maximum COP at the indicated conditions, and the Thermochemical subsystem delivers its highest COP with the NH 3 /BaCl 2 pair. Then, the power-storage and performance-storage relationships of the Thermochemical subsystem are analyzed for the NH 3 /BaCl 2 pair with respect to variations in operating conditions and several implementation parameters of the reactive composite. Finally, the performance of the hybrid system with the (NH 3 /LiNO 3 + NH 3 /BaCl 2 ) pair combination is compared to its subsystems against a variable demand profile calculated from climatic data of July in Barcelona, Spain. A novel indicator is defined to assess demand coverage: the Coefficient of Satisfaction of Demand (CSD). Depending on solar collector field area and amount of refrigerant storable by the Thermochemical subsystem, the hybrid system reaches up to 24% higher CSD than the reference system (a solar single-stage absorption refrigerator with no storage), and at least 14% higher COP than the Thermochemical Process.
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Experimental performances and optimization of a solid/gas Thermochemical Process for solar cooling.
2014Co-Authors: Driss Stitou, N. Mazet, S MauranAbstract:This paper focuses on the analysis of experimental performances and potential optimisations of a solar air-conditioning pilot plant, which is running in PROMES-CNRS laboratory (Perpignan, France) since 2006. This device consists of a solid/gas Thermochemical sorption Process powered at 60-70°C by 21.6 m² of flat plate solar collectors. The experimental device of a daily cooling capacity of 20 kWh of cold at 4°C, is able to refresh a conference room of 130m² and can provide a cooling power of 5 kW during 4 hours. The Thermochemical Process is based on the coupling of a liquid/gas phase change of a refrigerant (NH3) and a reversible chemical reaction between a reactive solid (BaCl2) and this refrigerant. It operates discontinuously according two phases : a diurnal period during which the reactor is connected to a condenser and heated by the solar collectors loop, and a nocturnal period where the reactor is connected to the evaporator and cooled down by an in-ground geothermal loop. The cold is produced at the evaporator and is stored into a PCM that solidifies at 5°C for a subsequent utilization during the day. In this paper, the analysis of the experimental results collected over two summer seasons is carried out. It leads to an averaged efficiency of 50% for the solar collectors, a Process COP ranging from 30 to 40% and a daily cooling productivity of about 0.8 to 1.2 kWh of cold per m² of solar collector. The mean experimental solar COP is about 18% for the summer period (july-august) and decreases to 11% from april to september. A modelling of the whole Process has been carried out in order to analyse the unsteady functioning of this solar cooling Process under variable operating conditions and optimize its performances. This analysis allows identifying ways of improvements of the design of the different components, and defining new strategies for the control/command of the whole Process. As a result, an improvement of the performances of 10% can be achieved by a better adjustment of the trigger thresholds for the different operating phases. The use of more efficient solar collectors and the change of their tilt angle can provide an improvement of 80% of the yearly performances. The simulations showed also that a better design of the Thermochemical reactor and the in-ground cooling loop may provide an improvement of 35% of the yearly produced cold.
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Thermochemical Process for seasonal storage of solar energy characterization and modeling of a high density reactive bed
Energy, 2012Co-Authors: Benoit Y Michel, Nathalie Mazet, Sylvain Mauran, Driss StitouAbstract:This paper focuses on the characterization and modeling of a solid/gas Thermochemical reaction between a porous reactive bed and moist air flowing through it. The aim is the optimization of both energy density and permeability of the reactive bed, in order to realize a high density Thermochemical system for seasonal thermal storage for house heating application. Several samples with different implementation parameters (density, binder, diffuser, porous bed texture) have been tested. Promising results have been reached: energy densities about 430–460 kWh m−3 and specific powers between 1.93 and 2.88 W/kg of salt. A model based on the assumption of a sharp reaction front moving through the bed during the reaction was developed. It has been validated by a comparison with experimental results for several reactive bed samples and operating conditions.
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development and comparison of advanced cascading cycles coupling a solid gas Thermochemical Process and a liquid gas absorption Process
Applied Thermal Engineering, 2000Co-Authors: Driss Stitou, Bernard Spinner, P Satzger, F ZieglerAbstract:Currently marketed double-effect absorption machines attain coefficients of performance (COP) of the order of 1.2 and, therefore, do not enable standard vapour compression air-conditioning systems to compete. The improvement of the COP requires increasing the high driving temperature level of the system in order to make possible additional stages and further refrigeration effects. But at high temperatures, working couples currently used in absorption systems (H2O/LiBr, NH3/H2O) pose corrosion problems for exchangers or decomposition of the working fluid. The implementation at these high temperatures of a solid/gas Thermochemical reaction system enables bypassing these restrictions. The coupling of a chemical reaction Process thermally cascaded with a liquid/gas absorption Process enables leading to triple-effect machines, indeed quadruple effect, the COP of which are from 30% to 60% higher than commercialised double-effect absorption chillers. Numerous coupling configurations are presented in this paper. A method of evaluation of the COP of the global machine is also developed. A comparison of these different configurations is carried out through value criteria characterising the quality of the obtained coupling. In this way, a first selection of combinations of interest can be performed. As part of a Franco–German cooperation, a triple-effect machine based on this approach is currently being realised. This new concept of coupling must lead to a new generation of thermal machines which will be capable in the near future of competing with vapor compression machines by the complementary use of the potentialities appropriate to each of the sorption Processes.
Bharat Bhushan - One of the best experts on this subject based on the ideXlab platform.
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tantalum membrane reactor for enhanced hi decomposition in iodine sulphur is Thermochemical Process of hydrogen production
International Journal of Hydrogen Energy, 2017Co-Authors: Bharat Bhushan, Nitesh Goswami, S.c. Parida, Amit K. Singha, B.n. Rath, H.s. Sodaye, R.c. BindalAbstract:Abstract HI decomposition reaction in Iodine–Sulphur (IS) Thermochemical Process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion. Metallic membrane reactor is proposed to be a Process intensification tool that can enable efficient HI decomposition by overcoming the equilibrium limitation of the reaction. In this study, we report the fabrication and characterization of clay alumina supported tantalum (Ta) membrane and its application in packed bed catalytic membrane reactor for HI decomposition section of IS Process for the first time. The alumina tubes were coated with thin film of Ta metal of thickness 2.5 μm using DC sputter deposition technique under the optimum set of parameters. The membranes were found to remain stable upto 200 Hrs of exposure under HI-H2O environment at 125 °C. Modeling of a packed bed Ta membrane reactor for HI decomposition was carried out to find out the optimum operating parameters of the membrane reactor to get a conversion of at least 95%. A packed bed membrane reactor (PBMR) assembly was fabricated with integration of the in-house synthesized Ta membrane and Pt-alumina catalyst for carrying out HI decomposition studies at 450 °C. The tube side was chosen as permeation zone and the shell side as the reaction zone. A single-pass conversion of 94.7% of HI to hydrogen was obtained by employing Ta metal membrane reactor against the theoretical equilibrium conversion value of 22%. The findings showed that Ta-based PBMR shall offer a potential benefit to reach higher efficiency of IS Thermochemical Process.
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Tantalum membrane reactor for enhanced HI decomposition in Iodine–Sulphur (IS) Thermochemical Process of hydrogen production
International Journal of Hydrogen Energy, 2017Co-Authors: Bharat Bhushan, Nitesh Goswami, S.c. Parida, Amit K. Singha, B.n. Rath, H.s. Sodaye, R.c. Bindal, Soumitra KarAbstract:Abstract HI decomposition reaction in Iodine–Sulphur (IS) Thermochemical Process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion. Metallic membrane reactor is proposed to be a Process intensification tool that can enable efficient HI decomposition by overcoming the equilibrium limitation of the reaction. In this study, we report the fabrication and characterization of clay alumina supported tantalum (Ta) membrane and its application in packed bed catalytic membrane reactor for HI decomposition section of IS Process for the first time. The alumina tubes were coated with thin film of Ta metal of thickness 2.5 μm using DC sputter deposition technique under the optimum set of parameters. The membranes were found to remain stable upto 200 Hrs of exposure under HI-H2O environment at 125 °C. Modeling of a packed bed Ta membrane reactor for HI decomposition was carried out to find out the optimum operating parameters of the membrane reactor to get a conversion of at least 95%. A packed bed membrane reactor (PBMR) assembly was fabricated with integration of the in-house synthesized Ta membrane and Pt-alumina catalyst for carrying out HI decomposition studies at 450 °C. The tube side was chosen as permeation zone and the shell side as the reaction zone. A single-pass conversion of 94.7% of HI to hydrogen was obtained by employing Ta metal membrane reactor against the theoretical equilibrium conversion value of 22%. The findings showed that Ta-based PBMR shall offer a potential benefit to reach higher efficiency of IS Thermochemical Process.
Sylvain Mauran - One of the best experts on this subject based on the ideXlab platform.
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The value of Thermochemical storage for concentrated solar power plants: economic and technical conditions of power plants profitability on spot markets
Energy Conversion and Management, 2019Co-Authors: Emeric Tapaches, Sylvain Mauran, David Salas, Maxime Perier-muzet, Didier Aussel, Nathalie MazetAbstract:This paper explores two new paradigms by studying the techno-economic relevance of a concentrated solar power plant in spot electricity markets involving strong price variations, and by investigating the integration of an innovative thermal storage performed by a Thermochemical Process in such plant. It aim is to optimize simultaneously the physical characteristics of the storage and the operation of the plant (combining production/storage/discharge phases). The methodology is based on pre-scenarios for the plant operation, and net present value as optimization criteria. The results show original scenarios involving one or two discharge phases (according to day, season, solar multiple, or location) with higher revenues and stored energies than the classical scenario (i.e. one discharge at sunset). Nevertheless, these revenues in the spot market are too low, leading to negative net present values. Thus, such power plant requires subsidies, that are here estimated from 12 €/Mwhe (depending on case study), which are much lower than classical flat feed-in tariffs.
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definition and performance simulations of a novel solar driven hybrid absorption Thermochemical refrigeration system
Energy Conversion and Management, 2018Co-Authors: Alberto Coronas, Jaume Fito, Sylvain Mauran, Nathalie Mazet, Driss StitouAbstract:Abstract This paper proposes a novel hybrid refrigeration system with energy storage, driven by low-grade solar heat and consisting of a single-stage absorption cycle coupled with a Thermochemical Process by sharing the same condenser, evaporator and refrigerant fluid. A first screening of ammonia-based working pairs for evaporation temperatures of −10 °C, condensation temperatures of 30 °C and heat source temperatures of 80 °C reveals LiNO 3 as suitable sorbent salt for the absorption subsystem, and BaCl 2 , PbBr 2 , SrCl 2 , LiCl, NH 4 Br and SnCl 2 as candidate reactive salts in the Thermochemical subsystem. The subsequent parametric study indicates that the absorption subsystem with NH 3 /LiNO 3 reaches close-to-maximum COP at the indicated conditions, and the Thermochemical subsystem delivers its highest COP with the NH 3 /BaCl 2 pair. Then, the power-storage and performance-storage relationships of the Thermochemical subsystem are analyzed for the NH 3 /BaCl 2 pair with respect to variations in operating conditions and several implementation parameters of the reactive composite. Finally, the performance of the hybrid system with the (NH 3 /LiNO 3 + NH 3 /BaCl 2 ) pair combination is compared to its subsystems against a variable demand profile calculated from climatic data of July in Barcelona, Spain. A novel indicator is defined to assess demand coverage: the Coefficient of Satisfaction of Demand (CSD). Depending on solar collector field area and amount of refrigerant storable by the Thermochemical subsystem, the hybrid system reaches up to 24% higher CSD than the reference system (a solar single-stage absorption refrigerator with no storage), and at least 14% higher COP than the Thermochemical Process.
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Thermochemical Process for seasonal storage of solar energy characterization and modeling of a high density reactive bed
Energy, 2012Co-Authors: Benoit Y Michel, Nathalie Mazet, Sylvain Mauran, Driss StitouAbstract:This paper focuses on the characterization and modeling of a solid/gas Thermochemical reaction between a porous reactive bed and moist air flowing through it. The aim is the optimization of both energy density and permeability of the reactive bed, in order to realize a high density Thermochemical system for seasonal thermal storage for house heating application. Several samples with different implementation parameters (density, binder, diffuser, porous bed texture) have been tested. Promising results have been reached: energy densities about 430–460 kWh m−3 and specific powers between 1.93 and 2.88 W/kg of salt. A model based on the assumption of a sharp reaction front moving through the bed during the reaction was developed. It has been validated by a comparison with experimental results for several reactive bed samples and operating conditions.
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solar heating and cooling by a Thermochemical Process first experiments of a prototype storing 60 kw h by a solid gas reaction
Solar Energy, 2008Co-Authors: Sylvain Mauran, H Lahmidi, V GoetzAbstract:Abstract The chemical heat pumps using monovariant solid/gas reactions and thermal solar energy are potentially interesting for the air-conditioning of building (heating in winter or mid-season and refreshing in summer). They provide a function of storage without loss and potentially at high energy density. The selected reaction involves SrBr2 as reactant and H2O as refrigerant fluid. It is adapted to the thermodynamic constraints in temperature (heat provided by plane solar collector, heating and cooling on the level of the floor) and uses reagents having a weak impact for the environment and health. The reactive salt SrBr2 is implemented with an expanded natural graphite in the form of a consolidated material which has acceptable thermal conductivity and permeability adapted to low pressure. The prototype reactor has a total volume of 1 m3. It is able to store, with a complete reaction, 60 kW h or 40 kW h for the heating or cooling function respectively. This prototype was tested under conditions representative of summer or mid-season; the mean heating or cooling powers, typically about 2.5–4 kW, are still insufficient because of a low heat transfer at the interface between the reactive layer and the exchanger wall. However this limitation can be clearly attenuated; that is the subject of current work in following these first experiments.
