7. Subtask7: Feasibility Study on Utilization of Hydrogen Energy

7.1 R&D Goals

(1) Study and investigate the demand levels and application technologies for hydrogen energy in the future by different modes of use (gaseous and liquid hydrogen etc.), make proposals for application technologies, clarify the advantages and disadvantages of each technology and identify development issues.

(2) Develop element technologies, if needed, for each of the studied hydrogen utilization technologies.

In fiscal 1997, for achieving these targets, continue study on promising technologies for each area of application and develop element technologies for especially promising utilization technologies.

7.2 Result in fiscal 1997

7.2.1 Power Generation

(1) System study

In fiscal 1997, trial calculations on the electrical efficiency were made taking the followings into consideration; 1. hydrogen purity, which influences efficiency of the argon circulation type hydrogen-combustion diesel engine cogeneration system, and 2. the power for oxygen separation from air. As the result, this system proved to have electrical efficiency higher than or equal to the conventional diesel engine cogeneration system even with these considerations. Also, detailed design was carried out for a laser ignition device, which was planned for actually application in fiscal 1998.

(2) Essential element technology

Then, a hydrogen injection device and an ignition device, as essential element technologies for realizing the hydrogen-combustion diesel engine cogeneration system, were manufactured and test operated, and by combining them with a rapid compression and expansion device together with a gas supply device, a fundamental combustion test device was manufactured and preliminary tests were performed using it.

Fig.7-1-1 Image Drawing of the Rapid Compression and Expansion Device

  1. Hydrogen injection device
    The hydrogen injection device, which adopted electronically controlled hydraulic drive system, was not only used in the experiment of rapid compression and expansion device but also provided the function and construction taking its application in the development of the engine in the future into consideration. It was manufactured targeting the injection pressure of 20 MPa, the minimum injection period of 3 ms and the injection volume of 300 mL, which corresponded to the planned actual engine performances, and it proved to have well controlled injection performance even under such a high pressure.

  2. Hydrogen ignition device
    For finding ignitable conditions for the ignition device having a spark plug for secure hydrogen ignition, it was equipped with a controllable ignition energy source and the current and voltage at the moment of discharge was made measurable.

  3. Fundamental combustion test
    The hydrogen injection and dissipation behaviors were optically observed and preliminary ignition experiments were performed, through which ignition of hydrogen by the spark plug under certain conditions was confirmed.

    Preparing for beginning of the regular combustion experiment in fiscal 1998, fundamental combustion phenomena were grasped and the problems in development of the engine were identified.

7.2.2 Transport

From the family car driven by a hydrogen-combusted engine and the microbus driven by a hybrid fuel cell, which were investigated in fiscal 1996, the latter was selected as the basis for study of the application for public transport.

(1) Performance Prediction by Simulations

Investigation was made into the necessary conditions for simulating exactly the effects by the practical application. Characteristics of the fuel cell were determined assuming further developments in the near future. The Lithium ion battery, which made remarkable progress in development, was selected. The evaluation were made for 15- mode, of which the off-mode fuel consumption was influenced largely by the inclination of the road, performance of the energy recovery by means of the regenerative braking and others. Moreover, serious influence of mass of the automobile on them, as was seen during the development of the electric automobile, was also confirmed.

(2) Scenario for Popularization

The mode of development and movements for popularization for the compressed natural-gas-fired automobiles and for electric automobiles were studied. Consecutively, necessary items for making hydrogen automobile popular were investigated.

(3) Advantages and Disadvantages of Each Type of Infrastructure for Hydrogen Supply to the Transport

  1. Within the scope of the case studies of R & D on the infrastructure for hydrogen supply to the transport, the infrastructures for liquid and compressed hydrogen in Europe and Unites States were investigated.

  2. As a investigation into the system flow, most practically feasible cases were studied for the hydrogen storage (liquid hydrogen, metal hydride and compressed hydrogen) .

  3. Investigation was made into the infrastructure for natural gas automobiles, which were technologically most similar to hydrogen automobiles.

  4. Investigation was made into the law and regulation to control the infrastructure for supplying hydrogen to the transport and the countermeasures for them were studied.

7.2.3 Fuel Cells Using Oxygen and Hydrogen

Investigation into fuel cells was continued, on the basis of the results in 1996, for 3 fuel cell systems, a 200 kW scale system and a 5,000 kW scale system for stationary use and a system for automobile use. Further, an investigation was carried out for a new system, which should produce hydrogen and oxygen electrolytically from water using electricity by night and utilize them for power generation by day.

(1) 200 kW Scale Fuel Cell System

A 200 kW scale normal pressure PEFC system was the object of study, which adopted internal humidification i.e. a part of cooling water was to be supplied directly to the fuel electrode for humidifying solid polymer membranes. The system construction and system flow were investigated for the fuel supply system, air supply system and cell cooling water system respectively, through which the issues for future investigation were identified.

(2) 5,000 kW Scale Fuel Cell System

The development trend of the fuel cell using oxygen as its oxidant was investigated, because above mentioned system was to use oxygen as the oxidant. Further, for cases which showed high efficiency in the fiscal 1996, study was made on the composition and size of the cell, scale of the system, roles of the auxiliary machines, control, safety and operating system.

(3) Fuel Cell System for Automobile

Characteristics of the fuel cell for automobiles and hydrogen absorption rate of the metal hydride was reviewed to 3 wt%, which was the target value of the WE-NET subtask 5. Further, the published data of NECAR II by Daimler-Benz, which was leading the today's development, were analyzed. In the high current density area, PEFC as well as its peripheries showed high energy density.

(4) 1,000 kW Scale Power Generation System Utilizing Electric Power by Night

Combinations of a Solid Oxide Steam Electrolyzer (SOEC) with a Polymer Electrolyte Fuel Cell(PEFC) and a Polymer Electrolyte Electrolyzer (PEEC) with a Solid Oxide Fuel Cell (SOFC) were studied. The result showed , that the SOEC-PEFC system had the highest overall efficiency of ca. 61 %. It was also known, that power generation hours affected largely, because of high costs of water electrolysis equipment.

7.2.4 Cryogenic Energy Applications

The investigation into oxygen production using cryogenic energy of liquid hydrogen was continued.

(1) Oxygen Separation

  1. PSA Combined Single Stage Condensation Method
    This is a method for producing oxygen by separation of the air by means of slush argon (triple point 83 K), which is produced using cryogenic energy of the liquid air. The feature of this system is increased safety by averting solidification of the air and also because of existence of argon between hydrogen and the air. By single stage condensation only, however, oxygen concentration could be raised merely by 5%. As its countermeasure, its combination of PSA was studied but as it could bring only a little improvement than PSA alone and as changes of the conditions could bring also no reduction of the consumption rate , this method was given up.

  2. Improvement in the Consumption Rate by the 2 Towers + Liquid Oxygen Pump Process
    Until the report of the fiscal 1996, investigation was made focusing on reduction of the power for oxygen production by utilizing cryogenic energy of the liquid hydrogen. In this year, however, investigation was made for a process utilizing still surplus (50 %) cryogenic energy as the power for compressing oxygen.

    The calculation on a 5,000 kW scale fuel cell system showed the consumption rate of 0.32 kW/Nm3 by applying the liquid compression using the liquid oxygen pump process, which resulted in a reduction of 26% compared with 0.43 kW/Nm3 for the normal temperature compression. The results of the calculation were as follows:

    Material air flow rate 7970 Nm3 /h
    Product oxygen flow rate 1720 Nm3 /h
    Product oxygen purity 96 %
    Power for oxygen production 527 kW
    (by normal temperature compressor 712 kW)

(2) Fundamental investigation into the air solidification

Investigation was made into the air solidification procedure, feared by sinking of temperature at the heat exchanging wall surface to the liquid hydrogen temperature, accompanied by reduction of the heat conduction.

Although heat conductivity of nitrogen and hydrogen on the solid phase coexistent line could be obtained, it proved to be impossible to acquire physical data in the vicinity of the triple point (on the solid and liquid coexistent line). There can be two processes presumed for air solidification, one from liquid phase and the other directly from gas, namely by frosting. As composition of the solid air after liquefaction varies from part to part, it is necessary hereafter to measure heat conductivity preparing local models. In case of frost, although its composition remains nearly the same, its density differs and needs to be measured.

7.2.5 Hydrogen Supply System

(1) Concrete issues in the assumed hydrogen supply system in a model city

  1. Suppression of boil off gas as well as its utilization
    Investigation was made into development of new containers and receiving systems, and problems for suppression of the boil off gas were identified. Supply systems to each of the hydrogen utilizing devices were also studied.

  2. Hydrogen receiving base
    Regarding the harbor facilities used as hydrogen receivinng bases, investigation was made into their service time and safety.

  3. A scenario for transferring to the hydrogen energy system
    As prerequisite conditions for the transfer, study was begun from the necessity of hydrogen and hydrogen resources and investigation was made into the scenario for introduction of the hydrogen energy system, including hydrogen production methods at the transfer stage.

(2) Stand-alone hydrogen refueling station

For promoting reasonable transfer to a hydrogen energy society, it is necessary to produce hydrogen on site even in a small scale, as well as to realize energy circulation system in which this hydrogen is consumed directly. For this purpose, stand-alone hydrogen refueling station was investigated and examined.
  1. Production capacity of the stand-alone hydrogen refueling stations were determined for 300 Nm3/h , which corresponded to the supply volume for 400 hydrogen automobiles a day (12 h).

  2. Hydrogen production method was investigated on the basis of natural gas reforming by steam and water electrolysis using electricity by night, and further, two types for water electrolysis, a polymer electrolyte type and an alkaline type, were investigated. As for the hydrogen storage and supply system, hydrogen shall be stored at the pressure of 20 MPa in long size cardres having a capacity of 3600 m3 and supplied to automobiles from them.

  3. The costs were estimated under these conditions.

7.3 Research plan for fiscal year 1998

(1) Concerning power generation, through ignition tests using the rapid expansion and compression testing system, fundamental data for determining the optimal ignition position and timing shall be acquired, influence of the injection stream shall be obtained, heat generation rate shall be analyzed, combustion rate shall be measured by means of the exhaust gas analysis and, moreover, the laser ignition shall be tested as a new ignition method. Further, investigation shall be made into the possible market of hydrogen combusted diesel engine cogeneration system.

(2) Concerning transport, investigation shall be made into preparation of a scenario for introduction of hydrogen automobiles and also into an environmental life cycle assessment of the hydrogen automobile. Further, investigation shall be continued for the fuel system in hydrogen automobiles.

(3) Concerning fuel cells using hydrogen, although numerous minute technical issues remain, essential technological issues have been completed. It is necessary hereafter to investigate applicable markets for this fuel cell including hydrogen demand in them. Further, for preparing an environmental life cycle assessment for hydrogen automobiles, evaluation shall be made on the production of the fuel cells and the findings shall be compiled.

(4) Concerning the cryogenic energy application, for easy restart of the development in the future on the basis of the first phase investigation, the optimal system capacity shall be selected for two types of small scale oxygen production system( low temperature separation and low temperature VSA method) and their system construction, composing devices, comparison of performances and characteristics, oxygen production costs and technological development issues shall be made clear.

(5) Concerning the hydrogen supply system, liquid hydrogen supply for small scale consumption systems shall be compiled and the hydrogen refueling station for automobiles shall be generally investigated.

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