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7. Task7 Development of Hydrogen Refueling Stations 7.1 R&D Target The target of research and development of the second stage for hydrogen refueling station is "to develop demonstration system which has hydrogen refueling capacity of 30 Nm3/h corresponding to 1/10 of practical scale and to verify the system performance through technical demonstration combined with hydrogen vehicle system for the purpose of establishment of essential and systematizing technology for hydrogen refueling station". In fiscal 1999, we studied the general system of hydrogen refueling station. We also investigated desirable specification for main component equipment of the station, such as hydrogen production equipment with reformer, polymer electrolyte water electrolysis hydrogen production equipment, hydrogen absorbing alloy tank and hydrogen dispenser unit, assuming aspects of set-up and operation in each hydrogen refueling station to make the total design of the station system. 7.2 R&D Results in Fiscal 1999 7.2.1 Hydrogen Refueling Station with Reformer 7.2.1.1 Total Basic Specification (1) Study of basic specification We studied the construction and specification of basic equipment for hydrogen refueling station and prepared a basic flow of total system in which a high pressure filling system was added to MH(Metal hydride hydrogen absorbing alloy) filling system as in the basic plan. And as a preliminary stage, we investigated an arrangement plan of hydrogen refueling station and calculated the necessary area for the station. (2) Study of the quantity of cold power supply We studied the cooling power during filling hydrogen to MH tank on a vehicle with the target filling speed, hydrogen of 25Nm3 in 10 minutes, and gained a general guideline about the temperature of cooling medium and the capacity of refrigerator. Concerning to the electric power load required for temperature cooling, we confirmed that the load is nearly equal to the power for pressure up to 20MPa in cooling temperature of -10℃. 7.2.1.2 Hydrogen Production Equipment with Reformer (1) Study of operating condition for reformer Through the influence estimation with the variation of S/C (molar ratio of steam to carbon), reforming temperature, ratio of recycling gases and air-fuel ratio, we had a grasp of optimum operation condition of the selected reformer for fuel cell. And consequently, we obtained the design condition of S/C=2.5, reforming temperature =700℃, ratio of recycling gases =0.21, air-fuel ratio =1.3~2.0. (2) Study of PSA unit <1>Study of compressor type The investigation of compressor types about rotary type and reciprocating type, further the study of pressure control system for reciprocating type were made. Each type seems to have some merits and demerits, so we shall continue the investigation. <2>PSA A study was made about the number of adsorption towers and the capacity of off-gas tank aiming to obtain hydrogen gas recovery rate over 70% and realizing more compact equipment. As there remains some possibility for optimization, we shall continue to study this subject. (3) Basic design A basic flow and a balance sheet were prepared based on the above-stated study as well as the study of control method. 7.2.1.3 Hydrogen Absorbing Alloy Storage Equipment (1) A selection of the best absorbing alloy for hydrogen A comparison between AB5 group alloy and AB2 group alloy was made. An effect of the additional element (Al, Co, Mn) to AB5 group alloy on the equilibrium hydrogen pressure was investigated. And consequently, we selected LaNi5 alloy as a base material and Mn as an additional element to it, because Mn can reduce the decrease in quantity of absorbed hydrogen when adding it to LaNi5 alloy and can adjust equilibrium pressure by small amount. And in order to increase the equilibrium pressure, a composition of the alloy was decided to be LmNiMn group alloy added with Ce. (2) Decision of design policy for the best tank In order to obtain design policy for the best tank, the basic characteristics was measured by a trial tank filled with selected alloys. In case of the second trial tank which has increased heat transfer area, we could keep the prescribed absorbing speed up to absorption of 75~85% of hydrogen for the total absorbed quantity. We decided design specification and operating condition based on these results. 7.2.1.4 Hydrogen Dispenser Unit (1) Study of equipment specification and selection of main equipment By investigation of outline of equipment based on requested specification, the basic flow of dispenser unit was prepared. Further, we selected cooling water supply unit, flow control unit and connectors, and consequently we narrowed down candidate types for equipment. For diameter of piping, 20A (inner diameter 23.9mm) was selected for hydrogen piping, 50A (inner diameter 57.2mm) for cooling water piping. (2) Study of system Other than outline investigation about sequence control of system, we investigated about complex type one-touch connector, detector system for full filling of tank and automatic fueling control system. 7.2.2 Polymer Electrolyte Water Electrolysis Hydrogen Refueling Station 7.2.2.1 Study of Total System We decided the basic specification of total system through the investigation of water electrolysis equipment, hydrogen absorbing alloy tank and dispenser. We studied and designed common utility condition, alarm system, central control system to decide the total basic system for the station. We investigated a German hydrogen refueling station and could confirm the technologies about water electrolysis equipment, dispenser, safety system etc.. Further, we investigated the domestic research organizations developing water electrolysis equipment and fuel cell, and employed the results to the design of hydrogen refueling station. We studied the site for equipment installation and demonstration test and clarified the conditions of space and power supply for equipment. Refer to these results, we could make the system specifications for the total system more accurate. 7.2.2.2 Development of Water Electrolysis Equipment We made the basic design of water electrolysis equipment which satisfies the hydrogen producing capacity prescribed in basic specification of hydrogen refueling station. In order to fit in the hydrogen supply condition of hydrogen absorbing alloy tank, we designed refining equipment and compressing equipment and a packaging structure combined with water electrolysis equipment. 7.2.2.3 Decision of Specification and Design for Hydrogen Absorbing Alloy Storage Equipment By studying the coincidence with the specification of water electrolysis type hydrogen producing equipment, we decided the specification of storage equipment which satisfies continuous filling performance and cooling/warming equipment which has good energy efficiency to make overall design for the equipment. 7.2.2.4 Decision of Specification and Design for Dispenser Unit We investigated hydrogen dispenser and various kinds of dispensers, and studied the design and make-up of the equipment to satisfy the developing condition. Further, we investigated the condition of absorbing alloy tank on a vehicle, decided the condition of rapid filling and design condition of cooling equipment. By investigation of instrument to measure hydrogen refueling quantity, we could select high precision instrument. Consequently, the specification for the unit could become clear. 7.3 Future Plan and Issues In this year's investigation , we studied an outline of specification for basic construction equipment of hydrogen refueling station. In the next year's investigation, based on the results obtained in this year's investigation, we will design in detail and partially begin manufacturing of equipment. Further, we will make detailed design for the total system of hydrogen refueling station based on the final specification of component equipment, and will construct a control system including safety measures. The coming year's action plan and R&D issues of every theme are as follows. 7.3.1 Total System (1) Detailed design of total system for hydrogen refueling station based on the final specification of every component equipment. (2) Constructing the operating method of hydrogen refueling station and total control system. (3) Constructing the total system which aims to have high energy efficiency based on the design introducing an effective heat utilizing system. (4) Investigation of various safety measures and safety management, and construction of the system. 7.3.2 Hydrogen Production Equipment with Reformer (1) Detailed design and manufacturing of reformer unit and PSA unit (including number of absorbing towers, down-sizing of off-gas tank). (2) Study of the control system including method for waiting. 7.3.3 Polymer Electrolyte Water Electrolysis Hydrogen Production Equipment (1) Promotion of detailed design and trial production of cell stack. (2) Establishment of a priori estimation method of high efficient operating
condition for water electrolysis equipment(temperature of
supplied water, pressure of produced hydrogen), and optimization
of purity improving method of produced hydrogen(dehumidify
and removal of impurities). 7.3.4 Hydrogen Absorbing Alloy Storage Equipment (1) Design of construction, trial production and estimation of high speed reaction unit. (2) Endurance cycle test with high speed reaction unit. (3) Hydrogen supply test from hydrogen reservoir unit to simulated tank for vehicle and hydrogen absorbing test with simulated MH tank for vehicle. 7.3.5 Hydrogen Dispenser Unit (1) Detailed design and manufacturing of dispenser unit (2) Investigation of control and operation system (including detection of full state, automatic filling control) for dispenser unit, trial production and estimation of one-touch connectors.
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