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A transient three dimensional numerical model of the heat transfer and fluid flow of a windowed fluidized bed reactor for solar thermochemical conversions is formulated and solved using discrete element method coupled to computational fluid dynamics. Radiation transfer equation is solved by discrete ordinate radiation model and the particle collision dynamics is solved by spring-dashpot model based on soft-sphere method. The instantaneous granular flow behavior of the irradiated bed is presented along with the incident radiation and particle size distribution. The results indicate that as time progresses the average velocity of the particle increases due to high temperature and bed expansion effect.

A novel concept of a windowed, particle fluidized bed solar reactor was proposed by Niigata University for performing a two-step thermochemical water splitting cycle with redox metal-oxide particles. The solar reactor concept needs to be combined with a beam-down type solar concentrator. A new type of 100kWth beam-down solar concentrating system with a secondly elliptical reflector was built at the campus of University of Miyazaki, Japan. The solar reactor and the CPC were fabricated for demonstrating the concept of the windowed, particle fluidized bed solar reactor. The first performance tests of the solar reactor with pulverized ceria particles with 100 - 300 μm in diameter were carried out using the Miyazaki beam-down solar concentrating system.

A copper-silicon alloy (Cu-Si alloy) was examined and evaluated as a phase-change material (PCM) for thermal energy storage applications such as load shaving and peak load shifting when coupled to a solar thermochemical reactor, reformer, or gasifier for the production of solar fuel. The Cu-Si alloy was selected as a high-temperature PCM thermal storage medium alternative to molten carbonate salts, and the compatibility of this alloy with a graphite-carbon encapsulation material was experimentally examined. The cyclic thermal storage/discharge properties of the Cu-Si alloy as a latent-heat energy storage material were studied with respect to thermal cycles. A thermal stability test was performed on Cu-20 wt% Si, Cu-25 wt% Si, and Cu-30 wt% Si alloys placed in a graphite container under vacuum. The performances of the Cu-Si alloys with increasing and decreasing temperature were measured during the thermal storage (heat-charge) and cooling (heat-discharge) modes, respectively. The elemental distribution of each Cu-Si alloy after the cyclic reaction was evaluated using an electron probe microanalyzer (EPMA). The heat storage capacities before and after the cyclic reaction were evaluated using differential scanning calorimetry (DSC) and were compared to the thermal storage properties of the molten carbonate salt.

In this study, an iron–germanium alloy (Fe–Ge alloy) was examined as a phase change material at temperatures exceeding 800°C for thermal energy storage in solar thermal applications. The cyclic properties of the thermal charge/discharge of the Fe–Ge alloy were examined at various thermal cycles. A thermal reliability test was performed in the form of a multi-cyclic performance assessment to evaluate the short- and long-term thermal stability of this alloy. Eutectic and hypereutectic chemical compositions of the Fe–Ge alloy were placed in a graphite container under vacuum and an inert atmosphere. The Fe–Ge alloy was experimentally examined for its compatibility with the container material of graphite-carbon. The element distribution of each Fe–Ge alloy was examined via a cyclic performance test. The heat storage capacities were evaluated and compared with those of chloride molten salts. The Fe–Ge alloy exhibits significant potential as a latent heat storage material in next-generation solar thermal applications as it demonstrates various advantages, namely: a higher storage capacity than that of chloride molten salts, temperature followability to the phase diagram, a quick thermal response, satisfactory cyclic behavior of charge/discharge modes, a thermodynamically stable metallographic structure, and non-reactivity with capsulation materials of graphite carbon.

Considering our lives, novel energy production is so required, and many scientists have been investigated this problem from a lot of views. One of the ways for the new energy productions is the solar power thermochemical production by an oxidation-reduction reaction of the ceramics CeO2 (ceria). In this research, the ceria is used for obtaining an H2 gas in vapor reaction in high-temperature thermal equipment which has a heat production system consisting by focused sun light. Nowadays technology has been also developed to keep a human living, not to harm the Earth environment. From these points, it is realized that how important the H2 gas is for our lives, so we are trying to improve the thermochemical H2 gas production by means of a ceria as a catalyst. Our purpose in this study is, to point out what effects occur in doped ceria’s thermal reduction (TR) reaction by using DV-Xα method. Comparing the models between the pure ceria and the Mn doped ceria, we have realized the difference by the reaction. In this appearance, one of the considerations is a view from p-DOSs (partial-Density of States), in which there are different O-2p DOSs by different crystal structures. From this view, we considered that the ceria structure would become more stable to keep the stable cyclic thermal reaction in Mn doped ceria.

Sweet disease (SD) is a multisystem inflammatory disorder characterised by fever, cutaneous erythematous plaques and aseptic neutrophilic infiltration of various organs. Neuro-Sweet disease (NSD) is a known rare central nervous system complication of SD. We describe a case of a 39-year-old Japanese woman who was diagnosed as NSD associated with Sjögren’s syndrome. She was successfully treated with systemic corticosteroid therapy.

In this research, heat transfer and hydrodynamics of a solar thermochemical fluidized bed reactor filled with ceria particles have been studied numerically and experimentally for beam-down solar concentrating system. A CFD-DEM model has been developed, in which the contact forces between the particles have been calculated by the spring-dashpot model, based on the soft-sphere method. An experimental visualization of particles circulation pattern and mixing of two-tower fluidized bed system has been presented. Simulation results have been compared with experimental data to validate the CFD-DEM model. Results indicate that the model can predict the particle-fluid flow of the two-tower fluidized bed reactor. Using this model, the key operating parameters can be optimized.

The first performance test of a novel windowed solar fluidized bed reactor was carried out for a two-step water splitting cycle with ceria particles by using a 30-kWth sun-simulator. O2 and H2 were successfully produced by the reactor system. During the thermal reduction step of the two-step water splitting, a fluidized bed of ceria particles was created by passing N2 gas through the perforated bottom plate of the reactor, and about 30 kWth of high flux visible light from 19 xenon-arc lamps of the sun-simulator was directed inside the reactor through a quartz window to directly irradiate the top of the fluidized bed. The central bed temperature reached the temperature of 1400 to 1500°C in the thermal reduction step. The subsequent water decomposition or hydrolysis step was performed at the central bed temperature of 800 - 900°C. About 6 - 12 Ndm3 of hydrogen was produced by one cycle.

A laboratory-scale prototype windowed internally circulating fluidized-bed reactor made of quartz sand and coal coke particles was investigated for steam gasification using concentrated Xe-light radiation as the energy source. The quartz sand was used as a chemically inert bed material for the fluidized bed, while the coal coke particles functioned as the reacting particles for the endothermic gasification reaction. The purpose of this study is a preliminary tests of batch type fluidized bed reactor that assuming a continuous feeding process of carbonous materials (cokes, coal, and biomass et al.) into the fluidized bed reactor with a thermal transfer/storage medium (quartz sand). The gasification performances such as the production rates of CO, H2, and CO2 were evaluated for the fluidized bed reactor.

The thermochemical two-step water-splitting cycle using transition element-doped cerium oxide (M–CeO2−δ; M = Fe, Co, Ni, Mn) powders was studied for hydrogen production from water. The oxygen/hydrogen productivity and repeatability of M–CeO2−δ materials with M doping contents in the 5–15 mol% range were examined using a thermal reduction (TR) temperature of 1500 °C and water decomposition (WD) temperatures in the 800–1150 °C range. The temperature, steam partial pressure, and steam flow rate in the WD step had an impact on the hydrogen productivity and production rate. 5 mol% Fe- and Co-doped CeO2−δ enhances hydrogen productivity by up to 25% on average compared to undoped CeO2, and shows stable repeatability of stoichiometric oxygen and hydrogen production for the cyclic thermochemical two-step water-splitting reaction. In addition, 5 mol% Mn-doped CeO2−δ, 10 and 15 mol% Fe- and Mn-doped CeO2−δ show near stoichiometric reactivities.

The characteristics of oxygen/hydrogen productivity using 30-mol%-M (M = Fe, Co, Ni, Mn)-doped CeO2−δ (30-mol%-M-CeO2−δ) were studied for the thermochemical two-step water splitting cycle comprising TR (thermal reduction) at 1500 °C and WD (water decomposition) at 1150 °C. The reproducibility of oxygen evolution was evaluated using 30-mol%-M-CeO2−δ and the effects of different M dopants were compared in the TR temperature range of 1200–1500 °C. Two solid phases detected in the 30-mol%-M- CeO2−δ powders were involved in the redox reaction of the thermochemical two-step water splitting cycle. Among the M-CeO2−δ samples evaluated, Mn-doped CeO2−δ provided the most stable and reproducible results and the highest reactivity for oxygen evolution at all temperatures employed for the TR step of the thermochemical two-step water-splitting cycle.

The flux distributions on the device in the solar reactor with the solar furnace were studied. This study aims to understand of characters of concentrated sun rays through KIER solar furnace and design of device shape for uniform heat distribution on the device surface. For the calculation of heat flux on the device with the KIER solar furnace, the optical modeling program Soltrace was used. At first, the KIER 45 kWth solar furnace and flat disk type device shape was simulated for understand of past experimental results. And then 3 cylinder shape device model and 1 conical shape device model was suggested and the heat flux intensity on the device was calculated. Finally, 5 models which is including flat disk type device shape, 3 cylinder shape, and 1 conical shape device models was calculated and compared. The results show that the concentrated sun rays from dish and heat flux intensity are has a directional characteristic concentrated to normal direction than perpendicular direction. The results will be applied to next solar demonstrations which are design of new solar reactor and new device shape.

Thermal energy storage using phase-change materials (PCM) can be utilizedfor load shaving or peak load shifting when coupled to a solar thermochemical reactor, reformer, or gasifier for the production of solar fuel. The PCM is embedded in packages or used in bulkin these storage systems, and therefore the compatibility of the encapsulation materials and the selection of the PCM arekey factorsfor ensuring the long operational life of the system. Variouskinds of molten fluoride, chloride and carbonate salts,andmixed moltensalt, which functionat high temperatures of over 500 °C, are known to cause corrosion or thermaldegradation. It is therefore worth studying newhigh-temperature PCM thermal storage alternatives to these molten salts foruse in solar thermochemical processes.In this study, the focus was on aluminum-silicon alloy (Al-Si alloy)as a high-temperature PCM thermal storage medium,and thecompatibility of this alloy with graphite-carbon encapsulation material wasexperimentally examined. The cyclic properties of thermal storage/discharge for Al-Si alloy as a latent-heat energy storage material was studied with respect to various thermal cycles. Athermal stability test was performed for the Al-20wt%Si, Al-25wt%Si, Al-30wt%Si, and Al-35wt%Si alloysplacedin the graphite container in vacuum. The temperatureincreasing and cooling performances of the Al-Si alloy weremeasured duringthe thermal storage (heat-charge) mode and during the cooling (heat-discharge) mode. Theoxidation levelof the Al-Si alloy after the cyclic reaction (20 cycles) was evaluated using an electron probe microanalyzer (EPMA).

The point-concentration receiver evaluation system was developed using the world class 30 kWth light source of 19 arc xenon lamps. The system comprises of a receiver unit, heat exchanger, blower, chiller and light source. Precise measurement of the thermal power absorbed by air was performed by the enthalpy rise of the coolant water and that of the exhausted air. The experimental test was performed using silicon carbide honeycomb in order to achieve a high air temperature of 560 °C. The efficiency of the receiver, based on the power of the aperture, was 40% to 80%. A three-dimensional simulation based on the dual cell approach was made to reveal detailed information of the flow and temperature fields. This successfully reproduced the thermal nonequilibrium between the solid and fluid parts of the receiver. The air exit temperature and efficiency of the numerical simulation were consistent with that determined experimentally. Air was suctioned from the broad space above the receiver top surface. The adopted simulation model with the free stream was confirmed to be essential for evaluating an open loop receiver.

The joint international project between Niigata University (Japan) and the Korea Institute of Energy Research, KIER (Korea) on “Solar Demonstration of Water-Splitting Reactor using Ceramic Foam Device” has two goals. (1) Develop a solar reactor using reactive cerium oxide foam devices for high-temperature two-step thermochemical water-splitting cycle. (2) Test its performance under various operational methods using a 40 kWth solar furnace driven by natural solar energy. The reactive CeO2/MPSZ (MgO – partially stabilized zirconia) foam device for two-step water-splitting was developed and prepared by Niigata University/Japan; it involves coating an inert zirconia foam matrix with reactive CeO2. In this paper, highly reactive CeO2 particles were used the redox material in CeO2/MPSZ foam devices to investigate the use of solar energy for hydrogen production. The solar-driven thermochemical two-step water-splitting cycle was demonstrated using the 40 kWth KIER solar furnace in Korea combined with the CeO2/MPSZ foam device. At the center of the foam device, temperatures were 1500 °C–1600 °C during the thermal reduction step and 600 °C-1100 °C during the subsequent water decomposition step. Hydrogen was successfully produced from the CeO2/MPSZ foam device, and profiles for hydrogen production and CeO2 conversion indicated definitely improved operations compared to earlier studies.

A laboratory-scale prototype windowed reactor using a fluidized bed of coal coke particles was tested for thermochemical gasification using concentrated Xe light radiation as an energy source. The fluidized-bed reactor, designed to be combined with a solar reflective tower or beam-down optics, is evaluated for steam gasification of coal coke according to gasification performance: CO, H2, and CO2 production rates; carbon conversion; light-to-chemical efficiency. Internal circulation of coal coke particles inside the reactor increases gasification performance, which is further enhanced by higher steam partial pressure of the inlet gas.

A solar reactor containing a CeO2-coated reactive foam device for producing hydrogen via a thermochemical two-step water splitting cycle was proposed and experimentally tested. Modeling of the optical properties of the 40 kWth KIER (Korea Institute of Energy Research) solar furnace was performed to design and prepare the optimized foam matrix shape and the new solar reactor. Solar demonstration of the solar reactor was accomplished in the KIER 40 kWth solar furnace and hydrogen was produced successfully during the water decomposition step. The conical shape foam device was suggested and tested the temperature gradients and hydrogen productivity. Finally, five cyclic test was conducted with the conical shape CeO2-coated foam device, the total hydrogen production was 1394.32 Ncm3 during the five cycles and the average hydrogen production per cycle was 278.86 Ncm3.

A window-type, solar fluidized bed receiver with quartz sand particles was tested by a 100-kWth novel beam-down solar concentrating system at Miyazaki, Japan. A compound parabolic concentrator (CPC) was placed above the quartz window of the receiver to increase the concentration of the solar fluxes from the beam-down solar concentrating system. The solar tests were performed in the middle of December, 2015. The central bed temperature of the receiver was reached around 960-1100° C. It was found that only 20 Ndm3/min of air flow rate was enough to create the uniform fluidization of the particles at the given temperature range. It was predicted that if the central bed temperature could have been higher than 1100°C if solar receiver test had conducted in other seasons than winter. The next solar campaign of the receiver test will be carried out in October, 2016.

The present authors (Niigata University, Japan) have developed a tubular reactor system using novel “double-walled” reactor/receiver tubes with carbonate molten-salt thermal storage as a phase change material (PCM) for solar reforming of natural gas and with Al-Si alloy thermal storage as a PCM for solar air receiver to produce high-temperature air. For both of the cases, the high heat capacity and large latent heat (heat of solidification) of the PCM phase circumvents the rapid temperature change of the reactor/receiver tubes at high temperatures under variable and uncontinuous characteristics of solar radiation. In this study, we examined cyclic properties of thermal storage/discharge for Cu-Si alloy in air stream in order to evaluate a potentiality of Cu-Si alloy as a PCM thermal storage material. Temperature-increasing performances of Cu-Si alloy are measured during thermal storage (or heat-charge) mode and during cooling (or heat-discharge) mode. A oxidation state of the Cu-Si alloy after the cyclic ...

This paper presents a numerical analysis of unconstrained melting of high temperature(>1000K) phase change material (PCM) inside a cylindrical container. Sodium chloride and Silicon carbide have been used as phase change material and shell of the capsule respectively. The control volume discretization approach has been used to solve the conservation equations of mass, momentum and energy. The enthalpy-porosity method has been used to track the solid-liquid interface of the PCM during melting process. Transient numerical simulations have been performed in order to study the influence of radius of the capsule and the Stefan number on the heat transfer rate. The simulation results show that the counter-clockwise Buoyancy driven convection over the top part of the solid PCM enhances the melting rate quite faster than the bottom part.

A laboratory-scale prototype windowed internally circulating fluidized-bed reactor made of quartz sand and coal coke particles was investigated for steam gasification using concentrated Xe-light radiation as the energy source. The quartz sand was used as a chemically inert bed material for the fluidized bed, while the coal coke particles functioned as the reacting particles for the endothermic gasification reaction. The advantages of using quartz sand as the bed material for the directly irradiated gasification reactor are as follows: (1) The bed height is maintained at a constant level during the gasification. (2) The quartz sand functions as a thermal transfer/storage medium inside the reactor. The gasification performances such as the production rates of CO, H2, and CO2; carbon conversion; and light-to-chemical energy conversion were evaluated for the fluidized-bed reactor with a thermal transfer/storage medium (quartz sand). The effects of using the bed material (quartz sand) on the gasification performance are described in this paper.

Double-walled reactor tubes containing thermal storage materials based on the molten carbonate salts—100 wt% Na 2 CO 3 molten salt, 90 wt% Na 2 CO 3 /10 wt% MgO and 80 wt% Na 2 CO 3 /20 wt% MgO composite materials—were studied for the performances of the reactor during the heat charging mode, while those of methane reforming with steam during heat discharging mode for solar steam reforming. The variations in the temperatures of the catalyst and storage material, methane conversion, duration of reforming for obtaining high levels of methane conversion (>90%), higher heating value (HHV) power of reformed gas and efficiency of the reactor tubes were evaluated for the double-walled reactor tubes and a single-wall reactor tube without the thermal storage. The results for the heat charging mode indicated that the composite thermal storage could successfully store the heat transferred from the exterior wall of the reactor in comparison to the pure molten-salt. The double-walled reactor tubes with the 90 wt% Na 2 CO 3 /10 wt% MgO composite material was the most desirable for steam reforming of methane to realize large HHV amounts of reformed gas and higher efficiencies during heat-discharging mode.

Thermochemical two-step water splitting cycle by concentrated solar heat has been studied as an energy conversion of solar energy into hydrogen energy. The thermochemical two-step water splitting cycle using metal oxide redox pair was composed of thermal reduction (T-R) step of metal oxide at higher temperature to release oxygen and, subsequent water decomposition (W-D) step of the reduced metal oxide with steam at lower temperature to produce hydrogen. Recently, cerium oxide (CeO2) is concerned as a redox pair of the thermochemical cycle for highly reactivity and cyclicity at high temperature. In this study, we focused a kinetic analysis of thermochemical two-step water splitting using cerium oxide. Various theoretical reaction models for thermal reduction (T-R) step of CeO2 particles are examined, and the appropriate reaction model for experimental results of thermogravimetric analysis was found by Master plot method. Finally, the reaction rate equation of thermal reduction is estimated.

Steam reforming of methane is a candidate process for converting concentrated high-temperature solar heat to chemical fuels because it is a high-temperature, highly endothermic process. We developed a tubular reformer system using novel double-walled reactor tubes with molten-salt thermal storage for solar reforming to produce hydrogen or synthetic gas (CO + H2) from a gas mixture of methane and steam using concentrated solar radiation as an energy source. The high heat capacity and large latent heat (heat of solidification) of the molten salt circumvents rapid temperature changes in the reactor tubes at high temperatures under fluctuating insolation. In this paper, we focused on under intermittent heating–cooling mode, the steam reforming performance of double-walled reactor tubes with Na2CO3/MgO composite thermal storage in comparison to pure Na2CO3 thermal storage. A heating mode using an electric furnace simulates reactor startup in the morning and reheating of the reactor by concentrated solar radiation after brief periods of cloud passage. The intermittent heating–cooling mode simulates fluctuating incident solar radiation during cyclic short-term cloud passage. The temperature variations of the catalyst and storage material, methane conversion, and higher heating value power of the reformed gas were examined for the double-walled reactor tubes and a single- wall reactor tube without thermal storage.

This study proposes a novel fluidized receiver for absorbing concentrated solar light at high temperatures. Previously, a tubular receiver and a volumetric receiver were developed to make high-temperature air for a solar gas turbine system. The aim was to combine these elements with a tower reflector; however, it was challenging to install these heavy receivers on the top of the tower. Currently, a fluidized receiver prototype is tested by a 3 kWh solar simulator in preparation for a field test at the Miyazaki beam-down reflector system. The fluid dynamics of the prototype receiver is numerically investigated. The currently treated receiver is an inner-circulating fluidized bed spouted by concentric gas streams with high and low velocities in the center and outer annulus, respectively. The draft tube is submerged in the particles to organize particle circulation. Concentrated light irradiates the particles through a quartz window at the top of the receiver container. Such a fluidized bed was first adopted by Kodama et al. for thermochemical reactions; however, it is currently pursued for its potential as a high-temperature receiver aimed at concentrated solar power generation. Experiments of the prototype receiver (inner diameter = 45 mm) demonstrated that the inner particles are heated to a temperature greater than 900 °C and that an increase of the central gas velocity removes the excess temperature near the particle bed surface. A numerical computation suggests that the large-scale circulation of particles leads to the activation of thermal mixing. The currently proposed receiver is thus expected to attenuate re-radiation losses likely to occur in a conventional volumetric porous receiver. The scale-up of the receiver is being considered by the numerical computation for a field test in the Miyazaki 100 kWh beam-down reflector system.

Although cerebral syphilitic gummas are generally considered to be rare manifestations of tertiary syphilis, many reports exist of early cerebral syphilitic gumma. Our finding of cerebral syphilitic gumma in an HIV-negative man within 5 months after syphilis infection suggests that this condition should be considered in syphilis patients who have neurologic symptoms.

A thermochemical two-step water-splitting cycle using perovskite oxides based on LaSrMnAlO3 was examined for hydrogen production from water using concentrated solar radiation. Concurrent Sr and Mn substitutions in La1-xSrxMnxAl1-xO3, Sr and Al substitutions in La1-ySryMn1-yAlyO3, and substitution of Al by Cr in La0.7Sr0.3Mn1-zCrzO3 were examined, and their kinetics, oxygen/hydrogen productivity, and repeatability were compared against LaSrMnAlO3. The impact of the chemical compositions of the perovskite oxides was systematically examined at a thermal reduction temperature of 1350 °C and water decomposition temperatures of 1000–1200 °C. From the viewpoints of average amounts of oxygen and hydrogen produced and the H2/O2 ratios, La0.7Sr0.3Mn0.9Cr0.1O3 and La0.7Sr0.3Mn0.8Cr0.2O3 provided the most reproducible productions of oxygen and hydrogen in the thermochemical two-step water-splitting cycle.

The volumetric solar receiver is a promised technology for high-temperature solar absorption in the concentrated solar power, industrial solar thermal usage and solar fuel production. Existing numerical simulation separated computations of light and convective flow and two-way coupling was not perfectly integrated between radiation and convective transport. This paper describes conjugate analysis of radiation, convection and conduction heat transfer in the volumetric receiver for perfect three-way coupling between three mechanisms of heat transfer. The numerical scheme was used for the volumetric receiver with plane surface and that with cut-back inlets for optimization of the geometry. The simulation was made for single cell of honeycomb with 2.4 mm pitch and 0.5 mm wall thickness. Two cases of surface geometry was computed: plane surface; cut-back inlet with 10 mm depth. Basic equations are momentum and energy equations with radiation transport equation. The discrete ordinates method was applied for solving the radiation intensity to consider perfect interaction between radiation, convection and conduction. The material of the receivers are assumed as stainless steel. The numerical simulation demonstrated the superiority of the cut-back receiver which increased the exit temperature by 30 K and decreased 2 Pa for the smallest beam angle of 10°. The contour plot of total heat flux on the wall revealed that the shadow effect was attenuated by the cut-back inlet leading to heat transfer enhancement. The novelties of this work are to treat perfect interaction between radiation and convection in volumetric receiver and to demonstrate the excellence of cut-back inlet receivers.

The concentrated solar power is utilized for industrial thermal usage, electricity generation and fuel production. To increase the solar thermal temperature is essential for enhancing the thermal efficiency of the energy conversion and for widening application. The synthetic oil, widely used for solar thermal storage, pylorizes at 400 °C, and this cannot be used for very high temperatures. The authors used quartz sand as thermal storage medium in the fluidized bed receiver, and achieved the thermal receiver temperatures beyond 1000 °C in the previous report. The research work was further made on using the particle steady flow for high-temperature solar thermal storage. The steady-flow-type particle receiver was designed through visualization of cold model and numerical simulation. The experimental apparatus was fabricated and tested using beam-down sun simulator of 1.0 kWth. The apparatus comprises of the internal-circulating fluidized bed receiver placed between a loop seal with an inlet port and another loop seal with a weir and an exit port of the particles. The tested particles are quartz sand of 0.1 – 0.2 mm and fused brown alumina of 0.09 – 0.1 mm. The experimental set up produces hot particles of quartz sand at 428°C and those of fused brown alumina at 491°C. The highly efficient steady-flow-type particle receiver created steady particle flow smoothly. This apparatus takes in the concentrated light through the quartz window to continuously discharge the particles at high temperatures beyond the criterion in synthesis oil (400°) for solar thermal storage.

Thermochemical two-step water-splitting using CeO 2 (cerium oxide) particles was studied to examine oxygen and hydrogen productivity and repeatability at thermal reduction (T-R) temperatures of 1300–1550 °C and water decomposition (W-D) temperatures of 400–1000 °C for the production of hydrogen from water using concentrated solar radiation as the energy source. The temperature dependency of oxygen and hydrogen productivity and the cyclic repeatability of CeO 2 are reported in this paper. The characteristic features of CeO 2 particles in the thermochemical two-step water-splitting cycle are compared with the well-known highly active reactive mediums of zirconia-supported Ni-ferrites (NiFe 2 O 4 / m -ZrO 2 and NiFe 2 O 4 / c -YSZ) and unsupported NiFe 2 O 4 .

We investigated the thermal reduction (T-R) of NiFe 2 O 4 , either supported by m -ZrO 2 or unsupported, as the oxygen-releasing step of a solar thermochemical water splitting cycle based on a ferrite/wustite redox system, by performing the Rietveld analysis using powder X-ray diffraction. The solid materials obtained after the T-R step at 1300–1400 °C were subjected to Rietveld analysis. The amounts and chemical compositions of the wustite phase produced by the T-R step and the remaining ferrite phase were identified quantitatively. Chemical reaction formulas for the different T-R temperatures were determined from the results. Consistency for the chemical reactions of the thermal reduction was discussed and evaluated comparing the O 2 amounts predicted by the chemical reaction formulas and measured experimentally by mass spectrometry.

A novel concept of particles fluidized bed receiver/reactor with a beam-down solar concentrating optics was performed using a 30-kWth window type receiver by a big sun-simulator. A fluidized bed of quartz sand particles was created by passing air from the bottom distributor of the receiver, and about 30 kWth of high flux visible light from 19 xenon-arc lamps of the sun-simulator was directly irradiated on the top of the fluidized bed in the receiver through a quartz window. The particle bed temperature at the center position of the fluidized bed went up to a temperature range from 1050 to 1200°C by the visible light irradiation with the average heat flux of about 950 kW/m2, depending on the air flow rate. The output air temperature from the receiver reached 1000 - 1060°C.

In 2014, Niigata University and the Institute of Applied Energy developed a point-concentration receiver-evaluation system using a silicon carbide (SiC) honeycomb and a three-dimensional simulation method. The system includes several improvements over its forerunner, including the ability to increase/decrease the power-on aperture (POA), air-mass flow-rate (AMF) and the height of the focal surface. This paper will focus on the results of tests using an improved receiver evaluation system, at a focal height of 1600 mm. Maximum outlet air temperature reached as high as 800 K, but exerted no untoward effects on the system. Also, receiver efficiency rated between 45 % and 70 %, according to POA. A numerical, 3D method of analysis was created at the same time, in order to analyze temperature and flow-distribution, in detail. This simulation, based on the dual-cell approach, reproduced the thermal non-equilibrium between the solid and fluid domain of the receiver material. The most interesting feature of this s...

The impacts of internal circulation of a mixture of coal-coke particles and quartz sand on the fluidization state in a fluidized bed reactor are investigated by a cold test with a benchtop set-up in order to design 10-30 kWth scale prototype windowed fluidized-bed reactor. Firstly, a basic relationship between pressure loss of inlet gas and gas velocity was experimentally examined using quartz sand with different particle sizes by a small-scale quartz tube with a distributor at ambient pressure and temperature. Based on the results, an appropriate particle range of quartz sand and layer height/layer diameter ratio (L/D ratio) was determined for a design of the fluidized bed reactor. Secondly, a windowed reactor mock-up was designed and fabricated for solar coke gasification using quartz sand as a bed material. The pressure loss between the inlet and outlet gases was examined, and descending cokes and sand particles on the sidewall of the reactor was observed in the reactor mock-up. The moving velocity and...

For the solar thermochemical gasification of coal coke to produce CO + H2 synthetic gas using concentrated solar radiation, a windowed reactor prototype is tested and demonstrated at laboratory scale for CO2 gasification of coal coke using concentrated Xe light from a 3-kWth sun simulator. The reactor was designed to be combined with a solar reflective tower or beam-down optics. The results for gasification performance (CO production rate, carbon conversion, and light-to-chemical efficiency) are shown for various CO2 flow rates and ratios. A kinetics analysis based on homogeneous and shrinking core models and the temperature distributions of the prototype particle bed are compared with those for a conventional fluidized bed reactor tested under the same Xe light irradiation and CO2 flow-rate conditions. The effectiveness and potential impacts of internally circulating fluidized bed reactors for enhancing gasification performance levels and inducing consistently higher bed temperatures are discussed in this paper.

Thermochemical two-step water splitting using a redox system of iron-based oxides or ferrites is a promising process for producing hydrogen without CO 2 emission by the use of high-temperature solar heat as an energy source and water as a chemical source. In this study, thermochemical hydrogen production by two-step water splitting was demonstrated on a laboratory scale by using a single reactor of an internally circulating fluidized bed. This involved the successive reactions of thermal-reduction (T-R) and water-decomposition (W-D). The internally circulating fluidized bed was exposed to simulated solar light from Xe lamps with an input power of 2.4–2.6 kW th for the T-R step and 1.6–1.7 kW th for the subsequent W-D step. The feed gas was switched from an inert gas (N 2 ) in the T-R step to a gas mixture of N 2 and steam in the W-D step. NiFe 2 O 4 / m -ZrO 2 and unsupported NiFe 2 O 4 particles were tested as a fluidized bed of reacting particles, and the production rate and productivity of hydrogen and the reactivity of reacting particles were examined.

A Ferrite/zirconia foam device in which reticulated ceramic foam was coated with zirconia-supported Fe3O4 or NiFe2O4 as a reactive material was prepared by a spin-coating method. The spin-coating method can shorten the preparation period and reduce the coating process as compared to the previous wash-coating method. The foam devices were examined for hydrogen productivity and cyclic reactivity in thermochemical two-step water-splitting. The reactivity of these foam devices were studied for the thermal reduction of ferrite on a laboratory scale using a sun simulator to simulate concentrated solar radiation, while the thermally reduced foam devices were reacted with steam in another quartz reactor under homogeneous heating in an infrared furnace. The most reactive foam device, NiFe2O4/m-ZrO2/MPSZ, was tested for successive two-step water-splitting in a windowed single reactor using solar-simulated Xe-beam irradiation with a power input of 0.4–0.7 kWth. The production of hydrogen continued successfully in the 20 cycles that were demonstrated using the NiFe2O4/m-ZrO2/MPSZ foam device. The NiFe2O4/m-ZrO2/MPSZ foam device produced hydrogen at a rate of 1.1–4.6 cm3 per gram of device through 20 cycles and reached a maximum ferrite conversion of 60%.

An educational practice entitled “Breaking Away from Shallow Learning Habits” of the Faculty of Engineering, Niigata University is adopted as “Good Practice (GP) of Education” by The Ministry of Education, Culture, Sports, Science and Technology. This practice consists of a new introductory educational program for freshmen entitled “Introduction to Engineering Literacy” , as well as improvement of other lectures/experimentations/exercises for design education. “Introduction to Engineering Literacy” of The Department of Chemistry and Chemical Engineering, is programmed to let the students make “failure” (discrepancy from the knowledge obtained from the textbooks) in experiments, let them propose improvement, and let them conduct the same experiment again after the improvement, so that the freshmen can experience a PDCA (Plan-Do-Check-Action) cycle.

The kinetics of methane reforming over Ru/γ-Al 2 O 3 -catalyzed high porosity Ni–Cr–Al foam were examined at temperatures of 650–900 °C in a quartz tubular reactor using an electric furnace. The kinetic data were analyzed by four different types of kinetic models based on the basic, Eley–Rideal, Langmuir–Hinshelwood, and stepwise mechanisms. Validation of the kinetic models was carried out by calculating the determination coefficient r 2 between the predicted and the experimental results for each model. The absolute average deviation percentage (AAD%) between the predicted and the experimental results was also estimated for each model. The kinetic model based on the reversible stepwise mechanism provided the best prediction of the experimental reforming rates with an AAD value of 6% in the range 650–850 °C.

In this work, we compare the activity of unsupported and monoclinic zirconia – supported nickel ferrites, calcined at two different temperatures, for solar hydrogen production by two-step water-splitting thermochemical cycles at low thermal reduction temperature. Commercial nickel ferrite, both as-received and calcined in the laboratory, as well as laboratory made supported NiFe2O4, are employed for this purpose. The samples leading to higher hydrogen yields, averaged over three cycles, are those calcined at 700 °C in each group (supported and unsupported) of materials. The comparison of the two groups shows that higher chemical yields are obtained with the supported ferrites due to better utilisation of the active material. Therefore, the highest activity is obtained with ZrO2-supported NiFe2O4 calcined at 700 °C.

Ni catalyst supported on MgO–Al2O3 (Ni/MgO–Al2O3) prepared from hydrotalcite, and Ni–Mg–O catalyst are studied in regard to their activity in the CO2 reforming of methane at high temperatures in order to develop a catalytically activated foam receiver–absorber for use in solar reforming. First, the activity of their powder catalysts is examined. Ni/MgO–Al2O3 powder catalyst exhibits a remarkable degree of high activity and thermal stability as compared with Ni–Mg–O powder catalyst. Secondly, a new type of catalytically activated ceramic foam absorber – Ni/MgO–Al2O3/SiC – and Ni–Mg–O catalyzed SiC foam absorber are prepared and their activity is evaluated using a laboratory-scale receiver–reactor with a transparent quartz window and a sun-simulator. The present Ni-based catalytic absorbers are more cost effective than conventional Rh/γ-Al2O3 catalyzed alumina and SiC foam absorbers and the alternative Ru/γ-Al2O3 catalyzed SiC foam absorbers. Ni/MgO–Al2O3 catalyzed SiC foam absorber, in particular, exhibits superior reforming performance that provides results comparable to that of Rh/γ-Al2O3 catalyzed alumina foam absorber under a high flux condition or at high temperatures above 1000 °C. Ni/MgO–Al2O3 catalyzed SiC foam absorber will be desirable for use in solar receiver–reactor systems to convert concentrated high solar fluxes to chemical fuels via endothermic natural-gas reforming at high temperatures.