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.
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.
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.
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.
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Papers by Akihiro Nakano