Abstract Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important ... more Abstract Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.
A laser holography interferometer is applied to investigate heat and mass transport phenomena aro... more A laser holography interferometer is applied to investigate heat and mass transport phenomena around the pseudo-critical line of supercritical artificial air with a composition of 79% nitrogen and 21% oxygen. In a previous study, we successfully observed the heat transport phenomenon, the piston effect, around the pseudo-critical line of nitrogen. The same experimental setup is applied to the supercritical artificial air, which is a compressible binary mixture fluid. We attempt to suppress the generation of natural convection, and successfully observe the heat and mass transport phenomena, which are the soret effect and the piston effect, respectively. Here, we discuss these effects observed in the supercritical artificial air.
Due to its ability to perform clean, efficient processes, hydrogen has long been promoted as the ... more Due to its ability to perform clean, efficient processes, hydrogen has long been promoted as the energy carrier of the future, but recent activity and advances suggest a tipping point has been reached as hydrogen is now being recognized by much of the world for its unique capabilities to strongly support global efforts in achieving climate neutrality. The coming decades will require a massive increase in the amount of hydrogen used in the energy system as well as a transition from largely thermochemical to predominantly electrochemical processes involving hydrogen. For this to happen, hydrogen will need to globally approach the gigaton-scale on an annual basis. Thus, before hydrogen can fully achieve its potential, challenges that need to be addressed include achieving scale and further research and development (R&D) advances.
A heat transport mechanism in nitrogen near the critical point is investigated by means of a nume... more A heat transport mechanism in nitrogen near the critical point is investigated by means of a numerical calculation. The thermofluid equations are solved by using the finite difference method. Calculations confirm a piston effect in nitrogen near the critical point. These results show that thin thermal boundary layers form near the walls while the remaining bulk fluid exhibits a uniform temperature distribution. This suggests a typical feature of the piston effect which is a relatively new mechanism of thermal energy transfer; i.e., the thermal energy propagates as acoustic waves rather than as heat conduction. The thermal boundary layers become thinner as the system approaches the critical point. The effect of gravity on the heat transport mechanism is also investigated in this report.
ABSTRACT As a method for simultaneously increasing efficiency of energy use and stability of ener... more ABSTRACT As a method for simultaneously increasing efficiency of energy use and stability of energy supply in commercial buildings, we have proposed Totalized Hydrogen Energy Utilization System (THEUS) that uses hydrogen as a high potential for energy carrier. The hydrogen storage method used by this system adopts metal hydride that excels in volumetric storage density. In this paper, as the model case for electric power load leveling operation, the optimum design and optimum operation method for multiple metal hydride tanks are described with a mathematical model which can simulate operation of the metal hydride tank and experimental equipment. As a result, the combination of tank specifications and operating conditions that produce the effective simultaneous utilization of 1) hydrogen, 2) metal hydride and 3) heat are identified. Furthermore, an operating method to make the most of the metal hydride tank flexibility with respect to tank selection is determined.
We have proposed the Totalized Hydrogen Energy Utilization System (THEUS) for applying to commerc... more We have proposed the Totalized Hydrogen Energy Utilization System (THEUS) for applying to commercial buildings. THEUS consists of fuel cells, water electrolyzers, metal hydride tanks and their auxiliaries. The basic operation of the THEUS is as follows: In the nighttime, hydrogen is produced by water electrolysis and stored in metal hydride tanks. In the daytime, it conducts fuel cell power generation using the stored hydrogen to meet the electric power demand of a building. The chilled and hot water generated in this process are also utilized. It is also possible to use the electric power from renewable energy. That is, THEUS has not only the load leveling function but the function to stabilize the grid system. The metal hydride tank is an important component of THEUS as hydrogen storage. The tank was designed as a thermally driven type, which be able to absorb/desorb hydrogen at normal temperature and pressure and utilize the endothermic reaction during hydrogen desorption as chilled water for air-conditioning. The tank with 50 kg AB5 type metal hydride alloy was assembled to investigate the hydrogen absorbing/desorbing process. The experimental results of the heat utilization ratio using this metal hydride tank are about 43%. Since the reaction heat is consumed to heat and to cool the tank up to the temperature of possible heat utilization. The heat utilization ratio can be improved by reduced the heat capacity of the tank and exchanging heat with multiple tanks.
International Journal of Hydrogen Energy, May 1, 2017
h i g h l i g h t s Dynamic response of the Totalized Hydrogen Energy Utilization System was stud... more h i g h l i g h t s Dynamic response of the Totalized Hydrogen Energy Utilization System was studied. Adaptability of the THEUS for the intermittent solar energy was investigated. Power, hydrogen, heat output from the THEUS were evaluated quantitatively. Efficiency of the THEUS was evaluated for a sunny day and a partly cloudy day test. A decline in WE efficiency was not observed for the fluctuating power input.
A self-supporting MPL was fabricated and applied to a GDL of a PEMFC. The MPL thickness and inter... more A self-supporting MPL was fabricated and applied to a GDL of a PEMFC. The MPL thickness and interface of MPL/carbon paper could be controlled precisely. Carbon paper free MPL showed better performance than did the integrated GDB/MPL GDL. Low thermal conductivity of MPL would cause vapor diffusion through MPL.
International Journal of Hydrogen Energy, Sep 1, 2018
The effect of species and concentration of electrolytic solution on the performance of anion exch... more The effect of species and concentration of electrolytic solution on the performance of anion exchange membrane (AEM) water electrolysis is experimentally examined. When potassium hydroxide (KOH) or potassium carbonate (K 2 CO 3) solution is applied for the electrolytic solution, electrolysis is successful under mild alkaline conditions, whereas electrolysis with pure water is quite difficult due to the high resistance of the AEM. AEM electrolysis performance with K 2 CO 3 solution is superior to that with KOH solution, even at similar pH of around 12. Hydrogen content in the anode gas compartment and relative humidity of produced hydrogen are also measured during the electrolysis.
International Journal of Hydrogen Energy, Mar 1, 2012
We have been performing research on the Totalized Hydrogen Energy Utilization System (THEUS) whic... more We have been performing research on the Totalized Hydrogen Energy Utilization System (THEUS) which has applications to commercial buildings and a planned added function of supplying energy to stations for hydrogen and electric vehicles. In that case we will utilize liquid hydrogen transported from a hydrogen station and all Boil-Off Gas (BOG) will be recovered in THEUS's metal hydride tanks. It is known that BOG is chiefly composed of para-hydrogen, which has different thermo-physical properties from normal hydrogen. It has been reported that some metal hydride alloys work as a catalyst to accelerate the paraortho conversion and the conversion proceeds relatively fast in the case of LaeNi 5. The conversion is considered to be an endothermic reaction. A misch metal (Mm)-Ni 5 metal hydride alloy, which contained La and Ni, was used in our THEUS metal hydride tank. To examine the effect of the para-ortho conversion on the THEUS operation, we investigated the absorption/desorption characteristics of the metal hydride tank with BOG. We confirmed that the effect of the heat of conversion was very small and BOG could be treated as normal hydrogen for practical application.
We have illvestigated the hydrQgen storage lanks 、 lth meta 幽 ydrides empbyed 「 br lo包d ［ ex ・ et... more We have illvestigated the hydrQgen storage lanks 、 lth meta 幽 ydrides empbyed 「 br lo包d ［ ex ・ eting of comlncroial buildings ． The storage tank uth 50 kg AB5 type lnetal llydride alloy was asbembled to
999 −2W Savannah River Site， Aiken SC20808 ， USA Two horizontal metal hydride tanks with a double... more 999 −2W Savannah River Site， Aiken SC20808 ， USA Two horizontal metal hydride tanks with a double coil heat exchanger that conta 血 ed 50 kg of MmNi5 metal hydride alloy with diff ， ∋rent Press 鵬 一 Composition − Tempera田 re (PCT)isotherm prope 血 es were developed and tested jll this s加 dy ． One was designed fbr 重 he experiments in USA and the other was designed for the experiments in Japan in which there is the high pressure gas safety act ． 皿 1e reaction heat recovery rates of these tanks were compared and it was confirmed that the reaction heat recovery rates were almost the same ． However it could not be filled the tank up with hydrogen in the case ofthe Japanese specifications ． Key Words： Hydrogen storage， Meta1 hydride alloy ， Reaction heat recovery ， Heat exchange
International Journal of Hydrogen Energy, Sep 1, 2011
Experimental results for hydrogen storage tanks with metal hydrides used for load leveling of ele... more Experimental results for hydrogen storage tanks with metal hydrides used for load leveling of electricity in commercial buildings are described. Variability in electricity demand due to air conditioning of commercial buildings necessitates installation of on-site energy storage. Here, we propose a totalized hydrogen energy utilization system (THEUS) as an on-site energy storage system, present feasibility test results for this system with a metal hydride tank, and discuss the energy efficiency of the system. This system uses a water electrolyzer to store electricity energy via hydrogen at night and uses fuel cells to generate power during the day. The system also utilizes the cold heat of reaction heat during the hydrogen desorption process for air conditioning. The storage tank has a shell-like structure and tube heat exchangers and contains 50 kg of metal hydride. Experimental conditions were specifically designed to regulate the pressure and temperature range. Absorption and desorption of 5,400 NL of hydrogen was successfully attained when the absorption rate was 10 NL/min and desorption rate was 6.9 NL/min. A 24-h cycle experiment emulating hydrogen generation at night and power generation during the day revealed that the system achieved a ratio of recovered thermal energy to the entire reaction heat of the hydrogen storage system of 43.2% without heat loss.
Abstract Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important ... more Abstract Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.
A laser holography interferometer is applied to investigate heat and mass transport phenomena aro... more A laser holography interferometer is applied to investigate heat and mass transport phenomena around the pseudo-critical line of supercritical artificial air with a composition of 79% nitrogen and 21% oxygen. In a previous study, we successfully observed the heat transport phenomenon, the piston effect, around the pseudo-critical line of nitrogen. The same experimental setup is applied to the supercritical artificial air, which is a compressible binary mixture fluid. We attempt to suppress the generation of natural convection, and successfully observe the heat and mass transport phenomena, which are the soret effect and the piston effect, respectively. Here, we discuss these effects observed in the supercritical artificial air.
Due to its ability to perform clean, efficient processes, hydrogen has long been promoted as the ... more Due to its ability to perform clean, efficient processes, hydrogen has long been promoted as the energy carrier of the future, but recent activity and advances suggest a tipping point has been reached as hydrogen is now being recognized by much of the world for its unique capabilities to strongly support global efforts in achieving climate neutrality. The coming decades will require a massive increase in the amount of hydrogen used in the energy system as well as a transition from largely thermochemical to predominantly electrochemical processes involving hydrogen. For this to happen, hydrogen will need to globally approach the gigaton-scale on an annual basis. Thus, before hydrogen can fully achieve its potential, challenges that need to be addressed include achieving scale and further research and development (R&D) advances.
A heat transport mechanism in nitrogen near the critical point is investigated by means of a nume... more A heat transport mechanism in nitrogen near the critical point is investigated by means of a numerical calculation. The thermofluid equations are solved by using the finite difference method. Calculations confirm a piston effect in nitrogen near the critical point. These results show that thin thermal boundary layers form near the walls while the remaining bulk fluid exhibits a uniform temperature distribution. This suggests a typical feature of the piston effect which is a relatively new mechanism of thermal energy transfer; i.e., the thermal energy propagates as acoustic waves rather than as heat conduction. The thermal boundary layers become thinner as the system approaches the critical point. The effect of gravity on the heat transport mechanism is also investigated in this report.
ABSTRACT As a method for simultaneously increasing efficiency of energy use and stability of ener... more ABSTRACT As a method for simultaneously increasing efficiency of energy use and stability of energy supply in commercial buildings, we have proposed Totalized Hydrogen Energy Utilization System (THEUS) that uses hydrogen as a high potential for energy carrier. The hydrogen storage method used by this system adopts metal hydride that excels in volumetric storage density. In this paper, as the model case for electric power load leveling operation, the optimum design and optimum operation method for multiple metal hydride tanks are described with a mathematical model which can simulate operation of the metal hydride tank and experimental equipment. As a result, the combination of tank specifications and operating conditions that produce the effective simultaneous utilization of 1) hydrogen, 2) metal hydride and 3) heat are identified. Furthermore, an operating method to make the most of the metal hydride tank flexibility with respect to tank selection is determined.
We have proposed the Totalized Hydrogen Energy Utilization System (THEUS) for applying to commerc... more We have proposed the Totalized Hydrogen Energy Utilization System (THEUS) for applying to commercial buildings. THEUS consists of fuel cells, water electrolyzers, metal hydride tanks and their auxiliaries. The basic operation of the THEUS is as follows: In the nighttime, hydrogen is produced by water electrolysis and stored in metal hydride tanks. In the daytime, it conducts fuel cell power generation using the stored hydrogen to meet the electric power demand of a building. The chilled and hot water generated in this process are also utilized. It is also possible to use the electric power from renewable energy. That is, THEUS has not only the load leveling function but the function to stabilize the grid system. The metal hydride tank is an important component of THEUS as hydrogen storage. The tank was designed as a thermally driven type, which be able to absorb/desorb hydrogen at normal temperature and pressure and utilize the endothermic reaction during hydrogen desorption as chilled water for air-conditioning. The tank with 50 kg AB5 type metal hydride alloy was assembled to investigate the hydrogen absorbing/desorbing process. The experimental results of the heat utilization ratio using this metal hydride tank are about 43%. Since the reaction heat is consumed to heat and to cool the tank up to the temperature of possible heat utilization. The heat utilization ratio can be improved by reduced the heat capacity of the tank and exchanging heat with multiple tanks.
International Journal of Hydrogen Energy, May 1, 2017
h i g h l i g h t s Dynamic response of the Totalized Hydrogen Energy Utilization System was stud... more h i g h l i g h t s Dynamic response of the Totalized Hydrogen Energy Utilization System was studied. Adaptability of the THEUS for the intermittent solar energy was investigated. Power, hydrogen, heat output from the THEUS were evaluated quantitatively. Efficiency of the THEUS was evaluated for a sunny day and a partly cloudy day test. A decline in WE efficiency was not observed for the fluctuating power input.
A self-supporting MPL was fabricated and applied to a GDL of a PEMFC. The MPL thickness and inter... more A self-supporting MPL was fabricated and applied to a GDL of a PEMFC. The MPL thickness and interface of MPL/carbon paper could be controlled precisely. Carbon paper free MPL showed better performance than did the integrated GDB/MPL GDL. Low thermal conductivity of MPL would cause vapor diffusion through MPL.
International Journal of Hydrogen Energy, Sep 1, 2018
The effect of species and concentration of electrolytic solution on the performance of anion exch... more The effect of species and concentration of electrolytic solution on the performance of anion exchange membrane (AEM) water electrolysis is experimentally examined. When potassium hydroxide (KOH) or potassium carbonate (K 2 CO 3) solution is applied for the electrolytic solution, electrolysis is successful under mild alkaline conditions, whereas electrolysis with pure water is quite difficult due to the high resistance of the AEM. AEM electrolysis performance with K 2 CO 3 solution is superior to that with KOH solution, even at similar pH of around 12. Hydrogen content in the anode gas compartment and relative humidity of produced hydrogen are also measured during the electrolysis.
International Journal of Hydrogen Energy, Mar 1, 2012
We have been performing research on the Totalized Hydrogen Energy Utilization System (THEUS) whic... more We have been performing research on the Totalized Hydrogen Energy Utilization System (THEUS) which has applications to commercial buildings and a planned added function of supplying energy to stations for hydrogen and electric vehicles. In that case we will utilize liquid hydrogen transported from a hydrogen station and all Boil-Off Gas (BOG) will be recovered in THEUS's metal hydride tanks. It is known that BOG is chiefly composed of para-hydrogen, which has different thermo-physical properties from normal hydrogen. It has been reported that some metal hydride alloys work as a catalyst to accelerate the paraortho conversion and the conversion proceeds relatively fast in the case of LaeNi 5. The conversion is considered to be an endothermic reaction. A misch metal (Mm)-Ni 5 metal hydride alloy, which contained La and Ni, was used in our THEUS metal hydride tank. To examine the effect of the para-ortho conversion on the THEUS operation, we investigated the absorption/desorption characteristics of the metal hydride tank with BOG. We confirmed that the effect of the heat of conversion was very small and BOG could be treated as normal hydrogen for practical application.
We have illvestigated the hydrQgen storage lanks 、 lth meta 幽 ydrides empbyed 「 br lo包d ［ ex ・ et... more We have illvestigated the hydrQgen storage lanks 、 lth meta 幽 ydrides empbyed 「 br lo包d ［ ex ・ eting of comlncroial buildings ． The storage tank uth 50 kg AB5 type lnetal llydride alloy was asbembled to
999 −2W Savannah River Site， Aiken SC20808 ， USA Two horizontal metal hydride tanks with a double... more 999 −2W Savannah River Site， Aiken SC20808 ， USA Two horizontal metal hydride tanks with a double coil heat exchanger that conta 血 ed 50 kg of MmNi5 metal hydride alloy with diff ， ∋rent Press 鵬 一 Composition − Tempera田 re (PCT)isotherm prope 血 es were developed and tested jll this s加 dy ． One was designed fbr 重 he experiments in USA and the other was designed for the experiments in Japan in which there is the high pressure gas safety act ． 皿 1e reaction heat recovery rates of these tanks were compared and it was confirmed that the reaction heat recovery rates were almost the same ． However it could not be filled the tank up with hydrogen in the case ofthe Japanese specifications ． Key Words： Hydrogen storage， Meta1 hydride alloy ， Reaction heat recovery ， Heat exchange
International Journal of Hydrogen Energy, Sep 1, 2011
Experimental results for hydrogen storage tanks with metal hydrides used for load leveling of ele... more Experimental results for hydrogen storage tanks with metal hydrides used for load leveling of electricity in commercial buildings are described. Variability in electricity demand due to air conditioning of commercial buildings necessitates installation of on-site energy storage. Here, we propose a totalized hydrogen energy utilization system (THEUS) as an on-site energy storage system, present feasibility test results for this system with a metal hydride tank, and discuss the energy efficiency of the system. This system uses a water electrolyzer to store electricity energy via hydrogen at night and uses fuel cells to generate power during the day. The system also utilizes the cold heat of reaction heat during the hydrogen desorption process for air conditioning. The storage tank has a shell-like structure and tube heat exchangers and contains 50 kg of metal hydride. Experimental conditions were specifically designed to regulate the pressure and temperature range. Absorption and desorption of 5,400 NL of hydrogen was successfully attained when the absorption rate was 10 NL/min and desorption rate was 6.9 NL/min. A 24-h cycle experiment emulating hydrogen generation at night and power generation during the day revealed that the system achieved a ratio of recovered thermal energy to the entire reaction heat of the hydrogen storage system of 43.2% without heat loss.
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Papers by Akihiro Nakano