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Jing Ding - One of the best experts on this subject based on the ideXlab platform.
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Thermochemical Storage performance of methane reforming with carbon dioxide using high temperature slag
Applied Energy, 2019Co-Authors: Jing Ding, Yarong Wang, Weilong WangAbstract:Abstract In iron and steel industry, production process is accompanied by a large amount of residual heat as high temperature slag. Methane reforming with carbon dioxide is one of the typical chemical energy Storage processes, and it can be applied to use residual heat and reduce carbon dioxide emission. In this paper, Thermochemical energy Storage performance of methane reforming using high temperature slag is researched. According to experimental and numerical results, high temperature slag can be used as energy source and catalyst for Thermochemical energy Storage process by methane reforming. Slag is almost non-porous material, and its activation energy is higher than that of common catalyst, so slag only has high catalytic activity under high temperature. During methane reforming process, methane conversion and Thermochemical Storage efficiency first increases and then decreases with reaction rate dropping, and the position with maximum reaction rate gradually changes from front of slag bed to the end. Many factors including inlet conditions and reactor structure can affect Thermochemical Storage performance. Increase of slag initial temperature can improve methane conversion and Thermochemical energy Storage efficiency. As reactant flow rate decreases or slag bed length rises, methane conversion gradually increases, while Thermochemical energy Storage efficiency first increases and then decreases. With suitable conditions, Thermochemical energy Storage efficiency of slag can be higher than 60%.
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Thermochemical Storage performances of methane reforming with carbon dioxide in tubular and semi-cavity reactors heated by a solar dish system
Applied Energy, 2017Co-Authors: Qinyuan Yuan, Jing DingAbstract:Abstract Thermochemical Storage performances of methane reforming with carbon dioxide in tubular and semi-cavity reactor heated by a solar dish system have been experimentally and numerically investigated. The methane conversion and Thermochemical Storage efficiency of methane reforming process in tubular reactor were experimentally studied for inlet flow rate 3–6 L/min and direct normal irradiation (DNI) 677.8–714.3 W/m 2 . According to the experimental system and results, Gaussian distribution model is derived for concentrated solar energy flux from solar dish, and a 3D finite volume method coupled with volumetric reaction kinetics and unilateral concentrated solar energy flux is established by experimental verification. The simulated methane conversion and energy Storage efficiency have good agreements with the experimental data, and the temperature and species concentration distributions of the reactor are also successfully predicted. In the middle region of reactor, the concentrated solar energy flux and heat loss reach maxima, while the net heat flux and reaction kinetic rate reach maxima in the front region because of high temperature and high reactant fraction. As the catalyst bed length increases, the residence time and reverse reaction rate both rise, so there exists a proper catalyst bed length. When DNI rises, the methane reforming is promoted, while the heat loss remarkably increases, which results in the maximum Thermochemical Storage efficiency under proper DNI. Structural and operating parameters for the present tubular reactor can be further optimized, and the proper catalyst bed length is 300 mm, while the proper DNI is 250–300 W/m 2 (focal energy flux of 244.3–293.2 kW/m 2 ). A semi-cavity reactor is designed to reduce the heat loss and enhance the energy Storage performance. According to the experimental results under inlet flow rate 2–6 L/min and DNI 452.4–598.5 W/m 2 , the methane conversion of semi-cavity reactor can be increased to 74.8%, and the Thermochemical Storage efficiency and total energy efficiency can be respectively increased to 19.7% and 28.9%.
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Thermochemical Storage performance of steam methane reforming in tubular reactor with simulated solar source
Energy Procedia, 2017Co-Authors: Jing DingAbstract:Abstract The Thermochemical Storage performance of steam methane reforming in a tubular reactor heated by simulated solar source was investigated under different conditions. As inlet flow rate increases, the methane conversion obviously decreases, while the Thermochemical energy Storage efficiency first increase for more reactants, and then it decreases because the methane conversion decreases. 3D numerical model considering unilateral solar irradiation with Gaussian distribution was established to predict heat transfer and chemical reaction inside the reactor. The simulation results very well fit with experiment, and the heat transfer of the reactor was further investigated with the impact of energy flux density. As energy flux density increases, the methane conversion sharply grows, while peak Thermochemical energy Storage efficiency exists.
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Transient Thermochemical Storage Performance of Methane Reforming in Semi-cavity Reactor Heated by Solar Dish System
Energy Procedia, 2017Co-Authors: Qinyuan Yuan, Jing DingAbstract:Abstract The transient Thermochemical Storage performance of methane reforming with carbon dioxide in a semi-cavity reactor heat by a dish solar system was numerically investigated. A 3D transient numerical model with Gaussian solar irradiation from dish solar system was proposed to simulate the temperature and species concentration distribution inside the reactor. Along the flow direction, the bed temperature first increases and then decreases, and its maximum appear behind the centre of the reactor. During the starting stage, the bed temperature sharply increases, and the methane mass fraction quickly decreases for the reaction, while the chemical energy Storage efficiency and the total energy Storage efficiency increase more quickly than the sensible heat energy Storage efficiency. When DNI is decreased for a short time, the incident energy flux quickly decreases, while the methane conversion and energy Storage change very little, so the energy Storage efficiency remarkably increases.
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high temperature energy Storage performances of methane reforming with carbon dioxide in a tubular packed reactor
Applied Energy, 2016Co-Authors: Jianfeng Lu, Jing Ding, Yuan Chen, Weilong WangAbstract:High temperature heat transfer and energy Storage performances of methane reforming with carbon dioxide in tubular packed reactor are investigated under different operating conditions. Experimental results show that the methane reforming in tubular packed reactor can efficiently store high temperature thermal energy, and the sensible heat and heat loss besides Thermochemical energy Storage play important role in the total energy Storage process. When the operating temperature is increased, the Thermochemical Storage efficiency first increases for methane conversion rising and then decreases for heat loss rising. As the operating temperate is 800°C, the methane conversion is 79.6%, and the Thermochemical Storage efficiency and total energy efficiency can be higher than 47% and 70%. According to the experimental system, the flow and reaction model of methane reforming is established using the laminar finite-rate model and Arrhenius expression, and the simulated methane conversion and energy Storage efficiency fit with experimental data. Along the flow direction, the fluid temperature in the catalyst bed first decreases because of the endothermic reaction and then increases for the heat transfer from reactor wall. As a conclusion, the maximum Thermochemical Storage efficiency will be obtained under optimal operating temperature and optimal flow rate, and the total energy efficiency can be increased by the increase of bed conductivity and decrease of heat loss coefficient.
Christian Sattler - One of the best experts on this subject based on the ideXlab platform.
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Oxides and porous structures based on earth-abundant elements for hybrid sensible/Thermochemical solar energy Storage in air-operated solar thermal power plants
2018Co-Authors: Christos Agrafiotis, Simone Tescari, Martin Roeb, Christian SattlerAbstract:The concept of regenerative sensible heat Storage in porous solids employed in air-operated solar thermal power plants can be hybridized with Thermochemical Storage by coating/manufacturing entirely the heat exchange modules with oxides of multivalent metals undergoing reduction/oxidation reactions with significant heat effects. A prerequisite for eventual commercialization of such Thermochemical Storage concepts is the use of low-cost, environmental-friendly, oxide compositions capable of reversible reduction/oxidation under air with high reaction enthalpies. Equally necessary is the shaping of such oxides into structures operating as integrated reactors/heat exchangers. In this perspective, a specific Mn-based mixed oxide system of composition (0.8)(Mn2O3)*(0.2)(Fe2O3) was investigated. The work involved shaping the powder to porous foams and pellets which were comparatively tested in an infrared furnace, to clarify the effect of high heating/cooling rates on redox performance and structure stability. The redox performance of such Mn-rich systems was found sensitive to exposure at high temperatures. As long as a temperature of ~ 1100oC is not exceeded during redox cycling, both powder and pellets seem to operate reversibly for a high number of cycles. However, the high sintering temperatures (1350oC) required to induce strength to high-porosity structures like foams before their use as Thermochemical Storage media, had an adverse effect on their redox performance.
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solar Thermochemical heat Storage via the co3o4 coo looping cycle Storage reactor modelling and experimental validation
Solar Energy, 2017Co-Authors: Abhishek Singh, Gunnar Lantin, Simone Tescari, Christos Agrafiotis, Martin Roeb, Christian SattlerAbstract:Abstract Thermochemical energy Storage (TCES) systems utilize reversible reactions to store solar energy in chemical form. The present work focuses on the cobalt/cobaltous oxide (Co3O4/CoO pair) based redox cycle in which the active oxide is coated on a cordierite honeycomb structure. During the redox cycle, cobalt oxide uptakes and releases oxygen from/to an air stream coming in direct contact with it. Thus air acts as a reaction medium as well as a heat transfer fluid (HTF). In this configuration, the Storage material works as a heat Storage medium and also a heat exchanger. A two-dimensional, axisymmetric numerical model to simulate the heat and mass transfer and the chemical reaction in the Thermochemical heat Storage reactor has been developed. Experimental results from a 74 kW hth-capacity prototype reactor installed at the Solar Tower Julich test facility, Germany, were used to validate the numerical model. The time-dependent boundary conditions in the form of inlet temperature and inlet mass flow rate from the experiments were employed in the numerical model. The temperatures of the redox material at different locations inside the prototype Thermochemical Storage/heat exchanger reactor were used for the numerical model validation. Total energy stored/released (sensible as well as chemical) during the experiments was also compared with the numerical model results. From this study, it is concluded that the numerical model can accurately predict charging/discharging processes for the cobalt oxide based Thermochemical Storage reactor system for multiple redox looping cycles. The model allows a better understanding of the complete process and helps to identify the effect of variation of boundary conditions on the system.
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Solar Thermochemical heat Storage via the Co3O4/CoO looping cycle: Storage reactor modelling and experimental validation
Solar Energy, 2017Co-Authors: Abhishek Singh, Gunnar Lantin, Simone Tescari, Christos Agrafiotis, Martin Roeb, Christian SattlerAbstract:Abstract Thermochemical energy Storage (TCES) systems utilize reversible reactions to store solar energy in chemical form. The present work focuses on the cobalt/cobaltous oxide (Co3O4/CoO pair) based redox cycle in which the active oxide is coated on a cordierite honeycomb structure. During the redox cycle, cobalt oxide uptakes and releases oxygen from/to an air stream coming in direct contact with it. Thus air acts as a reaction medium as well as a heat transfer fluid (HTF). In this configuration, the Storage material works as a heat Storage medium and also a heat exchanger. A two-dimensional, axisymmetric numerical model to simulate the heat and mass transfer and the chemical reaction in the Thermochemical heat Storage reactor has been developed. Experimental results from a 74 kW hth-capacity prototype reactor installed at the Solar Tower Julich test facility, Germany, were used to validate the numerical model. The time-dependent boundary conditions in the form of inlet temperature and inlet mass flow rate from the experiments were employed in the numerical model. The temperatures of the redox material at different locations inside the prototype Thermochemical Storage/heat exchanger reactor were used for the numerical model validation. Total energy stored/released (sensible as well as chemical) during the experiments was also compared with the numerical model results. From this study, it is concluded that the numerical model can accurately predict charging/discharging processes for the cobalt oxide based Thermochemical Storage reactor system for multiple redox looping cycles. The model allows a better understanding of the complete process and helps to identify the effect of variation of boundary conditions on the system.
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experimental evaluation of a pilot scale Thermochemical Storage system for a concentrated solar power plant
Applied Energy, 2017Co-Authors: Simone Tescari, Christos Agrafiotis, Martin Roeb, Abhishek Singh, L De Oliveira, Stefan Breuer, B Schloglknothe, Christian SattlerAbstract:A first of its kind pilot-scale redox-based Thermochemical Storage system has been set up and operated under near-realistic conditions inside a solar power tower plant. The Storage unit is made of inert honeycomb supports (cordierite) coated with 88kg of redox active material (cobalt oxide). An experimental campaign has been carried out consisting of 22 Thermochemical charge-discharge cycles. The heat absorbed or released by the chemical reaction became clearly evident through the temperature evolution inside the reactive material. It allows to store or release energy at constant temperature when crossing respectively the reduction/oxidation temperature of the Co3O4/CoO pair. A Storage performance factor (PF) was defined to evaluate how each experiment approaches the ideal behavior. During the complete campaign no measurable cycle-to-cycle degradation was observed and the system average capacity was very close to the ideal case of PF=0.84. The advantage of Thermochemical Storage could be quantified by comparing the Storage capacity, to that of a sensible-only Storage unit made of uncoated cordierite honeycombs. The Thermochemical system offered almost double Storage capacity (47.0kWh) cf. the same volume of the sensible-only case (25.3kWh).
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Exploitation of Thermochemical cycles based on solid oxide redox systems for Thermochemical Storage of solar heat. Part 6: Testing of Mn-based combined oxides and porous structures
Solar Energy, 2017Co-Authors: Christos Agrafiotis, Simone Tescari, Martin Roeb, Tina Block, Marion Senholdt, Christian SattlerAbstract:Abstract Low-cost, environmental-friendly, oxide compositions capable of reversible reduction/oxidation under air with significant reaction enthalpies are the first prerequisite for eventual commercialization of Thermochemical Storage concepts in air-operated solar thermal power plants. Equally necessary however, is the shaping of such oxides into compact structures operating as integrated reactors/heat exchangers. In this perspective two Mn-based mixed oxide systems were investigated: a specific Mn 2 O 3 -Fe 2 O 3 composition and selected Ca-Mn-based perovskite compositions CaMn 1−x B x O 3−δ doped in the B site with Ti, Al or Mg. The particular (0.8)(Mn 2 O 3 ) ∗ (0.2)(Fe 2 O 3 ) powder composition not only was reduced and re-oxidized in a fast and reproducible manner for 58 cycles under a wide range of heating/cooling rates in contrast to Mn 2 O 3 , but its re-oxidation was much more exothermic than that of Mn 2 O 3 . Furthermore the presence of Fe 2 O 3 enhances the shapability of this system to foams; such foams also demonstrated cyclic redox operation maintaining their structural integrity for 33 cycles, not exploiting however all the amount of oxide used for their manufacture for the Thermochemical reactions. The attribute of perovskites for continuous, quasi-linear oxygen uptake/release, can be beneficial to hybridization of Thermochemical with sensible Storage within a wider temperature range. Addition of Ti was found to have a beneficial effect on the perovskites’ redox stability. Whereas the shaping of such compositions to foams has not been attempted, CaMn 0.9 Ti 0.1 O 3−δ perovskite pellets exhibited oxygen release/uptake per mass very close to that of the respective loose powder without structural degradation. However, the induced heat effects of the perovskites’ redox reactions are substantially lower and need to be improved in the perspective of commercial-scale applications.
Weilong Wang - One of the best experts on this subject based on the ideXlab platform.
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Thermochemical Storage performance of methane reforming with carbon dioxide using high temperature slag
Applied Energy, 2019Co-Authors: Jing Ding, Yarong Wang, Weilong WangAbstract:Abstract In iron and steel industry, production process is accompanied by a large amount of residual heat as high temperature slag. Methane reforming with carbon dioxide is one of the typical chemical energy Storage processes, and it can be applied to use residual heat and reduce carbon dioxide emission. In this paper, Thermochemical energy Storage performance of methane reforming using high temperature slag is researched. According to experimental and numerical results, high temperature slag can be used as energy source and catalyst for Thermochemical energy Storage process by methane reforming. Slag is almost non-porous material, and its activation energy is higher than that of common catalyst, so slag only has high catalytic activity under high temperature. During methane reforming process, methane conversion and Thermochemical Storage efficiency first increases and then decreases with reaction rate dropping, and the position with maximum reaction rate gradually changes from front of slag bed to the end. Many factors including inlet conditions and reactor structure can affect Thermochemical Storage performance. Increase of slag initial temperature can improve methane conversion and Thermochemical energy Storage efficiency. As reactant flow rate decreases or slag bed length rises, methane conversion gradually increases, while Thermochemical energy Storage efficiency first increases and then decreases. With suitable conditions, Thermochemical energy Storage efficiency of slag can be higher than 60%.
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high temperature energy Storage performances of methane reforming with carbon dioxide in a tubular packed reactor
Applied Energy, 2016Co-Authors: Jianfeng Lu, Jing Ding, Yuan Chen, Weilong WangAbstract:High temperature heat transfer and energy Storage performances of methane reforming with carbon dioxide in tubular packed reactor are investigated under different operating conditions. Experimental results show that the methane reforming in tubular packed reactor can efficiently store high temperature thermal energy, and the sensible heat and heat loss besides Thermochemical energy Storage play important role in the total energy Storage process. When the operating temperature is increased, the Thermochemical Storage efficiency first increases for methane conversion rising and then decreases for heat loss rising. As the operating temperate is 800°C, the methane conversion is 79.6%, and the Thermochemical Storage efficiency and total energy efficiency can be higher than 47% and 70%. According to the experimental system, the flow and reaction model of methane reforming is established using the laminar finite-rate model and Arrhenius expression, and the simulated methane conversion and energy Storage efficiency fit with experimental data. Along the flow direction, the fluid temperature in the catalyst bed first decreases because of the endothermic reaction and then increases for the heat transfer from reactor wall. As a conclusion, the maximum Thermochemical Storage efficiency will be obtained under optimal operating temperature and optimal flow rate, and the total energy efficiency can be increased by the increase of bed conductivity and decrease of heat loss coefficient.
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Heat Transfer and Energy Storage Performance of Methane Reforming with Carbon Dioxide in Semi-cavity Reactor☆
Procedia Engineering, 2016Co-Authors: Qinyuan Yuan, Jing Ding, Weilong WangAbstract:Abstract The heat transfer and energy Storage performance of methane reforming with carbon dioxide in a semi-cavity reactor catalyzed by Ni/Al2O3 are numerically investigated. The concentrated solar energy flux is calculated by Gaussian distribution model, and the heat losses of radiation and convection in semi-cavity reactor are reduced by considering the angle factor. The simulated methane conversion and Thermochemical Storage efficiency have good agreements with previous experimental data. The simulation results indicate that the higher operating temperature promotes the methane reforming reaction, so the methane conversion obviously increases with the operating temperature. As DNI (direct normal irradiation) increases, the methane conversion increases, while the Thermochemical Storage efficiency first increases and then decreases. Compared with tubular reactor, the methane conversion of semi-cavity reactor increases for 13.2%, and the Thermochemical Storage efficiency get an increase of 12.9%. When the inlet velocity rises, the fluid temperature decreases with heat loss increasing, the methane conversion remarkably decreases with the residence time decreasing, and the Thermochemical Storage efficiency has a maximum.
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Thermochemical Storage Performance of Methane Reforming with Carbon Dioxide Tubular Reactor in a Solar Dish System
Energy Procedia, 2015Co-Authors: Jing Ding, Weilong Wang, Qinyuan YuanAbstract:Abstract The Thermochemical Storage performances of methane reforming with carbon dioxide catalyzed by Ni/Al 2 O 3 in a tubular reactor heat by a dish solar system were studied under different inlet velocity, solar direct irradiation (694.9-720.5 W/m 2 ). A 3D numerical model considering unilateral solar irradiation with Gaussian distribution was established to predict the temperature and species concentration distribution inside the reactor. The simulation results have a good agreement with the experimental data. The heat and mass transfer of the reactor was investigated with the impact of the catalyst bed length and insulation length. The decline of catalyst bed length will decrease reaction time and avoid reverse reaction, while the insulation will reduce the heat loss and hinder the concentrated solar radiation absorption, which indicate the existence of the proper catalyst bed length and insulation length.
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High Temperature Energy Storage Performances of Methane Reforming with Carbon Dioxide in Tubular Packed Reactor
Energy Procedia, 2014Co-Authors: Yuan Chen, Jing Ding, Weilong WangAbstract:Abstract High temperature heat transfer and energy Storage characteristics of methane reforming in tubular packed reactor are investigated under different operating temperature and inlet conditions. Experimental results show that the methane reforming in tubular packed reactor can efficiently Storage high temperature thermal energy, and the Thermochemical Storage, sensible heat increment and heat loss are all very important. As the operating temperature increases, the Thermochemical Storage efficiency first increases for methane conservation rising and then decreases for heat loss rising. When the operating temperate is 800 o C, the methane conservation is about 80%, and the Thermochemical Storage efficiency and total energy efficiency can be higher than 45% and 70%. The methane reforming process is further simulated using the laminar finite-rate model and Arrhenius expression, and the simulated temperature distribution, methane conversion and energy Storage efficiency totally have good agreements with experimental data.
Martin Roeb - One of the best experts on this subject based on the ideXlab platform.
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Oxides and porous structures based on earth-abundant elements for hybrid sensible/Thermochemical solar energy Storage in air-operated solar thermal power plants
2018Co-Authors: Christos Agrafiotis, Simone Tescari, Martin Roeb, Christian SattlerAbstract:The concept of regenerative sensible heat Storage in porous solids employed in air-operated solar thermal power plants can be hybridized with Thermochemical Storage by coating/manufacturing entirely the heat exchange modules with oxides of multivalent metals undergoing reduction/oxidation reactions with significant heat effects. A prerequisite for eventual commercialization of such Thermochemical Storage concepts is the use of low-cost, environmental-friendly, oxide compositions capable of reversible reduction/oxidation under air with high reaction enthalpies. Equally necessary is the shaping of such oxides into structures operating as integrated reactors/heat exchangers. In this perspective, a specific Mn-based mixed oxide system of composition (0.8)(Mn2O3)*(0.2)(Fe2O3) was investigated. The work involved shaping the powder to porous foams and pellets which were comparatively tested in an infrared furnace, to clarify the effect of high heating/cooling rates on redox performance and structure stability. The redox performance of such Mn-rich systems was found sensitive to exposure at high temperatures. As long as a temperature of ~ 1100oC is not exceeded during redox cycling, both powder and pellets seem to operate reversibly for a high number of cycles. However, the high sintering temperatures (1350oC) required to induce strength to high-porosity structures like foams before their use as Thermochemical Storage media, had an adverse effect on their redox performance.
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solar Thermochemical heat Storage via the co3o4 coo looping cycle Storage reactor modelling and experimental validation
Solar Energy, 2017Co-Authors: Abhishek Singh, Gunnar Lantin, Simone Tescari, Christos Agrafiotis, Martin Roeb, Christian SattlerAbstract:Abstract Thermochemical energy Storage (TCES) systems utilize reversible reactions to store solar energy in chemical form. The present work focuses on the cobalt/cobaltous oxide (Co3O4/CoO pair) based redox cycle in which the active oxide is coated on a cordierite honeycomb structure. During the redox cycle, cobalt oxide uptakes and releases oxygen from/to an air stream coming in direct contact with it. Thus air acts as a reaction medium as well as a heat transfer fluid (HTF). In this configuration, the Storage material works as a heat Storage medium and also a heat exchanger. A two-dimensional, axisymmetric numerical model to simulate the heat and mass transfer and the chemical reaction in the Thermochemical heat Storage reactor has been developed. Experimental results from a 74 kW hth-capacity prototype reactor installed at the Solar Tower Julich test facility, Germany, were used to validate the numerical model. The time-dependent boundary conditions in the form of inlet temperature and inlet mass flow rate from the experiments were employed in the numerical model. The temperatures of the redox material at different locations inside the prototype Thermochemical Storage/heat exchanger reactor were used for the numerical model validation. Total energy stored/released (sensible as well as chemical) during the experiments was also compared with the numerical model results. From this study, it is concluded that the numerical model can accurately predict charging/discharging processes for the cobalt oxide based Thermochemical Storage reactor system for multiple redox looping cycles. The model allows a better understanding of the complete process and helps to identify the effect of variation of boundary conditions on the system.
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Solar Thermochemical heat Storage via the Co3O4/CoO looping cycle: Storage reactor modelling and experimental validation
Solar Energy, 2017Co-Authors: Abhishek Singh, Gunnar Lantin, Simone Tescari, Christos Agrafiotis, Martin Roeb, Christian SattlerAbstract:Abstract Thermochemical energy Storage (TCES) systems utilize reversible reactions to store solar energy in chemical form. The present work focuses on the cobalt/cobaltous oxide (Co3O4/CoO pair) based redox cycle in which the active oxide is coated on a cordierite honeycomb structure. During the redox cycle, cobalt oxide uptakes and releases oxygen from/to an air stream coming in direct contact with it. Thus air acts as a reaction medium as well as a heat transfer fluid (HTF). In this configuration, the Storage material works as a heat Storage medium and also a heat exchanger. A two-dimensional, axisymmetric numerical model to simulate the heat and mass transfer and the chemical reaction in the Thermochemical heat Storage reactor has been developed. Experimental results from a 74 kW hth-capacity prototype reactor installed at the Solar Tower Julich test facility, Germany, were used to validate the numerical model. The time-dependent boundary conditions in the form of inlet temperature and inlet mass flow rate from the experiments were employed in the numerical model. The temperatures of the redox material at different locations inside the prototype Thermochemical Storage/heat exchanger reactor were used for the numerical model validation. Total energy stored/released (sensible as well as chemical) during the experiments was also compared with the numerical model results. From this study, it is concluded that the numerical model can accurately predict charging/discharging processes for the cobalt oxide based Thermochemical Storage reactor system for multiple redox looping cycles. The model allows a better understanding of the complete process and helps to identify the effect of variation of boundary conditions on the system.
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experimental evaluation of a pilot scale Thermochemical Storage system for a concentrated solar power plant
Applied Energy, 2017Co-Authors: Simone Tescari, Christos Agrafiotis, Martin Roeb, Abhishek Singh, L De Oliveira, Stefan Breuer, B Schloglknothe, Christian SattlerAbstract:A first of its kind pilot-scale redox-based Thermochemical Storage system has been set up and operated under near-realistic conditions inside a solar power tower plant. The Storage unit is made of inert honeycomb supports (cordierite) coated with 88kg of redox active material (cobalt oxide). An experimental campaign has been carried out consisting of 22 Thermochemical charge-discharge cycles. The heat absorbed or released by the chemical reaction became clearly evident through the temperature evolution inside the reactive material. It allows to store or release energy at constant temperature when crossing respectively the reduction/oxidation temperature of the Co3O4/CoO pair. A Storage performance factor (PF) was defined to evaluate how each experiment approaches the ideal behavior. During the complete campaign no measurable cycle-to-cycle degradation was observed and the system average capacity was very close to the ideal case of PF=0.84. The advantage of Thermochemical Storage could be quantified by comparing the Storage capacity, to that of a sensible-only Storage unit made of uncoated cordierite honeycombs. The Thermochemical system offered almost double Storage capacity (47.0kWh) cf. the same volume of the sensible-only case (25.3kWh).
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Thermochemical Storage for CSP via redox structured reactors/heat exchangers: The RESTRUCTURE project
2017Co-Authors: George Karagiannakis, Simone Tescari, Martin Roeb, Abhishek Singh, Chrysoula Pagkoura, Athanasios G. Konstandopoulos, Matthias Lange, Johnny Marcher, Aleix Jové, Cristian PrietoAbstract:The present work provides an overview of activities performed in the framework of the EU-funded collaborative project RESTRUCTURE, the main goal of which was to develop and validate a compact structured reactor/heat exchanger for Thermochemical Storage driven by 2-step high temperature redox metal oxide cycles. The starting point of development path included redox materials qualification via both theoretical and lab-scale experimental studies. Most favorable compositions were cobalt oxide/alumina composites. Preparation of small-scale structured bodies included various approaches, ranging from perforated pellets to more sophisticated honeycomb geometries, fabricated by extrusion and coating. Proof-of-concept of the proposed novel reactor/heat exchanger was successfully validated in small-scale structures and the next step included scaling up of redox honeycombs production. Significant challenges were identified for the case of extruded full-size bodies and the final qualified approach related to preparati...
Christos Agrafiotis - One of the best experts on this subject based on the ideXlab platform.
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Oxides and porous structures based on earth-abundant elements for hybrid sensible/Thermochemical solar energy Storage in air-operated solar thermal power plants
2018Co-Authors: Christos Agrafiotis, Simone Tescari, Martin Roeb, Christian SattlerAbstract:The concept of regenerative sensible heat Storage in porous solids employed in air-operated solar thermal power plants can be hybridized with Thermochemical Storage by coating/manufacturing entirely the heat exchange modules with oxides of multivalent metals undergoing reduction/oxidation reactions with significant heat effects. A prerequisite for eventual commercialization of such Thermochemical Storage concepts is the use of low-cost, environmental-friendly, oxide compositions capable of reversible reduction/oxidation under air with high reaction enthalpies. Equally necessary is the shaping of such oxides into structures operating as integrated reactors/heat exchangers. In this perspective, a specific Mn-based mixed oxide system of composition (0.8)(Mn2O3)*(0.2)(Fe2O3) was investigated. The work involved shaping the powder to porous foams and pellets which were comparatively tested in an infrared furnace, to clarify the effect of high heating/cooling rates on redox performance and structure stability. The redox performance of such Mn-rich systems was found sensitive to exposure at high temperatures. As long as a temperature of ~ 1100oC is not exceeded during redox cycling, both powder and pellets seem to operate reversibly for a high number of cycles. However, the high sintering temperatures (1350oC) required to induce strength to high-porosity structures like foams before their use as Thermochemical Storage media, had an adverse effect on their redox performance.
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solar Thermochemical heat Storage via the co3o4 coo looping cycle Storage reactor modelling and experimental validation
Solar Energy, 2017Co-Authors: Abhishek Singh, Gunnar Lantin, Simone Tescari, Christos Agrafiotis, Martin Roeb, Christian SattlerAbstract:Abstract Thermochemical energy Storage (TCES) systems utilize reversible reactions to store solar energy in chemical form. The present work focuses on the cobalt/cobaltous oxide (Co3O4/CoO pair) based redox cycle in which the active oxide is coated on a cordierite honeycomb structure. During the redox cycle, cobalt oxide uptakes and releases oxygen from/to an air stream coming in direct contact with it. Thus air acts as a reaction medium as well as a heat transfer fluid (HTF). In this configuration, the Storage material works as a heat Storage medium and also a heat exchanger. A two-dimensional, axisymmetric numerical model to simulate the heat and mass transfer and the chemical reaction in the Thermochemical heat Storage reactor has been developed. Experimental results from a 74 kW hth-capacity prototype reactor installed at the Solar Tower Julich test facility, Germany, were used to validate the numerical model. The time-dependent boundary conditions in the form of inlet temperature and inlet mass flow rate from the experiments were employed in the numerical model. The temperatures of the redox material at different locations inside the prototype Thermochemical Storage/heat exchanger reactor were used for the numerical model validation. Total energy stored/released (sensible as well as chemical) during the experiments was also compared with the numerical model results. From this study, it is concluded that the numerical model can accurately predict charging/discharging processes for the cobalt oxide based Thermochemical Storage reactor system for multiple redox looping cycles. The model allows a better understanding of the complete process and helps to identify the effect of variation of boundary conditions on the system.
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Solar Thermochemical heat Storage via the Co3O4/CoO looping cycle: Storage reactor modelling and experimental validation
Solar Energy, 2017Co-Authors: Abhishek Singh, Gunnar Lantin, Simone Tescari, Christos Agrafiotis, Martin Roeb, Christian SattlerAbstract:Abstract Thermochemical energy Storage (TCES) systems utilize reversible reactions to store solar energy in chemical form. The present work focuses on the cobalt/cobaltous oxide (Co3O4/CoO pair) based redox cycle in which the active oxide is coated on a cordierite honeycomb structure. During the redox cycle, cobalt oxide uptakes and releases oxygen from/to an air stream coming in direct contact with it. Thus air acts as a reaction medium as well as a heat transfer fluid (HTF). In this configuration, the Storage material works as a heat Storage medium and also a heat exchanger. A two-dimensional, axisymmetric numerical model to simulate the heat and mass transfer and the chemical reaction in the Thermochemical heat Storage reactor has been developed. Experimental results from a 74 kW hth-capacity prototype reactor installed at the Solar Tower Julich test facility, Germany, were used to validate the numerical model. The time-dependent boundary conditions in the form of inlet temperature and inlet mass flow rate from the experiments were employed in the numerical model. The temperatures of the redox material at different locations inside the prototype Thermochemical Storage/heat exchanger reactor were used for the numerical model validation. Total energy stored/released (sensible as well as chemical) during the experiments was also compared with the numerical model results. From this study, it is concluded that the numerical model can accurately predict charging/discharging processes for the cobalt oxide based Thermochemical Storage reactor system for multiple redox looping cycles. The model allows a better understanding of the complete process and helps to identify the effect of variation of boundary conditions on the system.
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experimental evaluation of a pilot scale Thermochemical Storage system for a concentrated solar power plant
Applied Energy, 2017Co-Authors: Simone Tescari, Christos Agrafiotis, Martin Roeb, Abhishek Singh, L De Oliveira, Stefan Breuer, B Schloglknothe, Christian SattlerAbstract:A first of its kind pilot-scale redox-based Thermochemical Storage system has been set up and operated under near-realistic conditions inside a solar power tower plant. The Storage unit is made of inert honeycomb supports (cordierite) coated with 88kg of redox active material (cobalt oxide). An experimental campaign has been carried out consisting of 22 Thermochemical charge-discharge cycles. The heat absorbed or released by the chemical reaction became clearly evident through the temperature evolution inside the reactive material. It allows to store or release energy at constant temperature when crossing respectively the reduction/oxidation temperature of the Co3O4/CoO pair. A Storage performance factor (PF) was defined to evaluate how each experiment approaches the ideal behavior. During the complete campaign no measurable cycle-to-cycle degradation was observed and the system average capacity was very close to the ideal case of PF=0.84. The advantage of Thermochemical Storage could be quantified by comparing the Storage capacity, to that of a sensible-only Storage unit made of uncoated cordierite honeycombs. The Thermochemical system offered almost double Storage capacity (47.0kWh) cf. the same volume of the sensible-only case (25.3kWh).
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Exploitation of Thermochemical cycles based on solid oxide redox systems for Thermochemical Storage of solar heat. Part 6: Testing of Mn-based combined oxides and porous structures
Solar Energy, 2017Co-Authors: Christos Agrafiotis, Simone Tescari, Martin Roeb, Tina Block, Marion Senholdt, Christian SattlerAbstract:Abstract Low-cost, environmental-friendly, oxide compositions capable of reversible reduction/oxidation under air with significant reaction enthalpies are the first prerequisite for eventual commercialization of Thermochemical Storage concepts in air-operated solar thermal power plants. Equally necessary however, is the shaping of such oxides into compact structures operating as integrated reactors/heat exchangers. In this perspective two Mn-based mixed oxide systems were investigated: a specific Mn 2 O 3 -Fe 2 O 3 composition and selected Ca-Mn-based perovskite compositions CaMn 1−x B x O 3−δ doped in the B site with Ti, Al or Mg. The particular (0.8)(Mn 2 O 3 ) ∗ (0.2)(Fe 2 O 3 ) powder composition not only was reduced and re-oxidized in a fast and reproducible manner for 58 cycles under a wide range of heating/cooling rates in contrast to Mn 2 O 3 , but its re-oxidation was much more exothermic than that of Mn 2 O 3 . Furthermore the presence of Fe 2 O 3 enhances the shapability of this system to foams; such foams also demonstrated cyclic redox operation maintaining their structural integrity for 33 cycles, not exploiting however all the amount of oxide used for their manufacture for the Thermochemical reactions. The attribute of perovskites for continuous, quasi-linear oxygen uptake/release, can be beneficial to hybridization of Thermochemical with sensible Storage within a wider temperature range. Addition of Ti was found to have a beneficial effect on the perovskites’ redox stability. Whereas the shaping of such compositions to foams has not been attempted, CaMn 0.9 Ti 0.1 O 3−δ perovskite pellets exhibited oxygen release/uptake per mass very close to that of the respective loose powder without structural degradation. However, the induced heat effects of the perovskites’ redox reactions are substantially lower and need to be improved in the perspective of commercial-scale applications.
