WE-NET Home Page/Summary of Annual Reports 1998

7. Subtask7: Feasibility Study on Utilization of Hydrogen Energy

7.1 R&D Target

The target of study and investigation carried out since FY 1993 are as follows:

(1) Study and investigate about the demand of level and application technologies for hydrogen energy in the future by different mode of use (gaseous and liquid hydrogen etc.), make proposal for application technologies, clarify the advantage and disadvantage of each technology and identify development issues.

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

In FY 1998, 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 R&D result in FY 1998

7.2.1 Investigation and study for power generation

(1) System proof test

In FY 1998, basic characteristics such as combustion efficiency, indicated efficiency were determined, performing the combustion test wherein hydrogen is injected into argon-oxygen atmosphere and steam-oxygen atmosphere utilizing the rapid compression and expansion equipment installed in the Mechanical Engineering Laboratory of Agency of Industrial Science and Technology, aiming to proof actually for realizability of the two system, namely the hydrogen diesel engine cogeneration of argon circulation type and steam circulating type.

As the result, combustion efficiency more than 90%, and indication efficiency of approximately 42.4% (HHV value) for the argon circulation type and of approximately 33.9%(HHV value) for the steam circulation type were achieved. So that realizability of the hydrogen diesel engine cogeneration system was confirmed and at the same time shifting to the actual proof test for single cylinder unit planed to perform from FY 1999 is prospected.

(2) Element technology proof test

The test of hydrogen injection device and hydrogen ignition device which are important element technologies were performed. The influence of injection nozzle diameter and injection nozzle number to the formation of jet flow and auto ignition phenomenon were observed through a visualizing equipment, furthermore, the forced ignition test using an arc ignition device and a laser ignition device were performed on trial and the ignition condition thereof was grasped.

Observation of jet flow and auto ignition test
The hydrogen combustion under high pressure atmosphere was observed by the schlieren photographing that is an optical observation technique. As the result, the injection characteristics that the jet flow angle is almost constant regardless the nozzle diameter, and the jet flow arrival distance is depend on small injection device when the nozzle diameter become small were grasped. Also, the auto ignition condition become clear, for example, the probability of auto ignition become higher when atmosphere temperature exceeds 950°C.
Fundamental combustion test for hydrogen ignition test
The CDI (Condenser Discharging Ignition) method and the current interception method were tested as the ignition method of hydrogen by spark discharge using a spark plug. As the result, it was observed that the CDI method produce more stable ignition than the current interception method.
Furthermore, it was observed that the sure flame traveling is obtained at not more than 30 degree of nozzle angle through the twin nozzle test. The laser ignition method having high duration due to the non-contact method and high freedom for selection of the ignition position was adopted and made clear the condition in which the stable ignition is obtained.

7.2.2 Investigation and study for transportation means

In FY 1998, the introduction scenario of hydrogen automobiles and the environment LCA (Life Cycle Assessment) including the production process of automobiles which affect warming of globe etc. were performed, because it is estimated in the report of last year that the hydrogen automobiles will be introduced in the market within relative short period of time. Also, the issues which may occur when the hydrogen automobiles are introduced within a short time, for example, preparation of law and regulation, preparation of infrastructure and exhaust of carbon dioxide were investigated and studied.

(1) Introduction scenario

The technical and political issues were selected regarding to the introduction and popularization of hydrogen automobiles, studying the introduction from the view point of short term and mid and long term. Especially, it was pointed out that in order to popularize the hydrogen automobiles in earnest, the prototype hydrogen automobile qualified by the minister must be traveled soon and prepare the technical standard based on the actual proven data. In order to purchase and travel the hydrogen automobiles by popular users, it is necessary further process such as decontrol of qualification by the minister.

In the short term scenario, it was clarified that the establishment of technical standards is a very important factor to determine the commencement time of earnest popularization, preparing the issues to be cleared in process from actual proof test to practical use and earnest introduction during the period till 2010. In the mid and long term view point, it was considered that greater part of automobiles will be family cars and vans when it is assumed that five million automobiles will spread in 2030. It is necessary to increase the hydrogen refueling stations together with increasing of vehicles, therefore it was proposed that the development for hydrogen supply equipment with low cost is essential.

(2) Environment LCA

The study of energy efficiency and exhaust of carbon dioxide in the fuel cycle (analysis along energy flow) was performed, concerning the hydrogen fuel cell automobiles mounting hydrogen produced from regenerable energy and natural gas as primary energy.

Object of studying is family car or wagon car correspond to gasoline automobile with displacement of 1500cc.

It was clarified that there is possibility of the primary energy consumption of fuel cell automobiles become less than half of the current automobiles according to the fuel cycle analysis and become about half even in LCA. It was concluded that the energy flow with highest efficiency is the system of hydrogen refueling station produced by solar cell, and the next is the system in which natural gas transmitted through the pipe line is transported to the consuming area and is reformed at the station.

Although the exhaust volume of carbon dioxide is only generated in the manufacturing process of automobiles when regenerable energy is used as primary energy, it was concluded that the exhaust volume of carbon dioxide even when natural gas is used as primary energy can be reduced less than about 40% in respect of the current automobiles, and less than half even in LCA.

7.2.3 Investigation and study for fuel cell utilizing pure hydrogen

In FY 1998, market research of the polymer electrolyte fuel cell(PEFC) utilizing pure hydrogen in the period of about 2010 to 2030 was performed. Also, the specification, the manufacturing method and the materials of PEFC were investigated for LCA of the fuel cell automobiles.

(1) Market research of PEFC utilizing pure hydrogen

For electric enterprise
The hydrogen combustion turbine generators are suitable to the large capacity power generation for electric enterprise. As for market of the fuel cell, the distributed power generation with MW class and the peak cut power generation are taken into consideration, however, popularization of the distributed power generation is issue in the future, so that the estimation of market is difficult in this moment.
For industry
The introduction of fuel cell with 100kW to 5000kW class is possible and introduction to salt electrolysis, petrochemistry and steel works where hydrogen are produced as a secondary product are considered.
For public welfare and business
70% of the power generation plants are not more than 500kW, and it is necessary to compete with the existing equipment economically that hydrogen price must be not more than 25 yen/Nm³, equipment price must be not more than 0.15 million yen/kW and unit price of the power generation must be not more than about 22 yen/kWh.
For transportable power generation equipment
The price of existing equipment are degree of 40 to 80 kyen/kW and inexpensive, however, the requirement of low noise for construction power source in night is very strong, so that the introduction into market can be expected even expensive some degree.
For automobiles
In the present, world wide automobile manufacturers are endeavoring to develop the fuel cell automobile of methanol reforming type and pure hydrogen type, but the ultimate automobile is said as the pure hydrogen type. It is supposed that the introduction of fuel cell automobiles into the market will begin about 2004, and will grow up to several million about 2030 corresponding to the preparation of hydrogen supply base.
For other market
There are market for propulsion of ship, for space and for household other than above.

(2) Investigation of fuel cell data for LCA of fuel cell automobiles

The specification of 25kW stack with the membrane humidifier was estimated, modeling the newest stack of Ballard's Mark 7 which seemed to be mounted on NECAR II and NECAR III of Daimler-Benz by Barad. In addition, the material and the dimension of each components such as cells , humidifiers, end plates, as well as used amount materials per stack was calculated , assuming the manufacturing method of menbrane-electrode assemblies and separators for cells and humidifiers.

7.2.4 Investigation and study for cryogenic energy application

The study of distributed type oxygen supply equipment utilizing the cryogenic energy of liquid hydrogen was performed.

(1) Study for a combined cycle of He brayton cycle utilizing liquid hydrogen cryogenic energy and oxygen production equipment

In order to optimize the combination of oxygen production equipment and He brayton cycle utilizing the liquid hydrogen cryogenic energy, three cases of He conditions were studied (supply/return temperature: 140.7/199.4, 152.7/217.3, 166.6/232.7K) and the specific power consumption of oxygen for each case was calculated, Furthermore, economical comparison with the conventional process was performed.

Typical results are
Produced oxygen concentration : 96.0%
Production rate: 1651Nm³/h(as pure oxygen)
Specific power consumption of oxygen: 0.330kWh/Nm³(as pure oxygen)

(2) Study for cryogenic VSA utilizing liquid hydrogen

The specification was clarified with performing the simulation analysis in a practical equipment scale and that the specific power consumption of oxygen was calculated against the oxygen yield and concentration. It is found that the specific power consumption of oxygen decreases with decrease of concentration.

Typical results are
Produced oxygen concentration : 93.0%
Production rate: 484Nm³/h(as pure oxygen)
Specific power consumption of oxygen: 0.66kWh/Nm³ (as pure oxygen)

(3) Study for air separation equipment utilizing liquid hydrogen

The specific power consumption of oxygen and the rough production cost was calculated on trial, when production scale, oxygen concentration and oxygen pressure were varied for the air separation equipment where oxygen gas is produced utilizing the cryogenic energy of liquid hydrogen.

Typical results are
Produced oxygen concentration : 96.0%
Product0ion rate: 1651Nm³/h(as pure oxygen)
Specific power consumption of oxygen: 0.441kWh/Nm³(as pure oxygen)

(4) Study for measuring method of thermal conductivity of solid air

The features, the comprised equipment and the equipment price were studied regarding to the transient hot-wire method, the forced Rayleigh scattering method and the radial steady heat flow method. It was clarified that the recommendable method for measuring of the thermal conductivity of solid nitrogen are in order of the transient hot-wire method, the forced Rayleigh scattering method and the radial steady heat flow method.

Through the study from (1) to (4) improvement of the specific power consumption of oxygen become possible in spite of the small scale oxygen production equipment owing to the utilization of cryogenic energy and the proposal of original combined cycle by this task.

However, economical merit could not be found out under the present condition compared with the conventional oxygen production process.

The important issues of further study are the basic research for thermal properties and basic thermal conductive mechanism of solid air (nitrogen) including the cost reduction means, which enables the design of direct heat exchange between hydrogen and oxygen, as well as the basic test at laboratory scale for the temperature dependence of mass transfer coefficient as is pointed out by VSA.

7.2.5 Investigation and study for hydrogen refueling station

In FY 1998, the following concrete items were investigated and studied, following the report of last year concerned with the study of hydrogen supply system and issues thereof, and supposing the various utilization method for hydrogen supply to the hydrogen automobiles through the distributed type hydrogen refueling station where produces hydrogen from regeneratable energy including natural gas, as a countermeasure during the period till large amount of hydrogen become possible to import.

The hydrogen production technology, the transportation technology, the storage technology and the filling technology were investigated and studied, and summarized the various issues, the performance of efficiency and pressure etc. and the suppression for generation of boil off gas.
Configuration of hydrogen refueling station
- System where hydrogen is produced at supplying site: Five systems (the reforming of natural gas, the reforming of methanol, the alkali water electrolysis, the solid polymer water electrolysis, the combination of solar generation and solid polymer water electrolysis) were investigated and studied.
- System where hydrogen is produced collectively out of refueling station: The system where liquid or high pressure hydrogen produced collectively at a hydrogen storage base and supplied to the hydrogen refueling stations through transportation by tank lorry etc. was investigated and studied. Also, it is clarified that liquid hydrogen can be transported through the current transportation system.
Result of cost analysis for various refueling station
The supposed supplying cost of hydrogen refueling stations was compared and studied under the ideal conditions. As the result, the details of cost structure become possible to read directly from the diagram, in other hand the economical factors at the present was clarified, for example, in the case of high pressure hydrogen the transportation cost is given much weight, and in the case of water electrolysis method the electricity price is given much weight at the production process. It is also important for the selection of hydrogen refueling station system that the both system must be studied under consideration of the preparation state of infrastructure at the installed location, so that this study offers one solution against the various selection possibilities.

7.3 Further plan and issues

FY 1999 is the initial year when entire WE-NET are active as the second phase. Therefore, investigations and studies will be newly promoted re-constructing the project.

(1) Power generation technology

A hydrogen diesel engine of 100 kW class with single cylinder will be developed for cogeneration plant. The engine shall not exhaust environment affecting substances and shall be possible to achieve the efficiency at transmission terminal of about 45% and total efficiency of higher than 85% (based on HHV) The development and continuous operation test will be carried out and research and development issues for actual use will be extracted.

(2) Hydrogen automobile system

The development of elementally technology of the fuel system for the hydrogen fuel cell automobile keeping in mind the fuel supply from a hydrogen refueling station will be performed. The technical verification of hydrogen automobile system combined with the hydrogen supply system, as well as the evaluation of energy efficiency etc. will be carried out.

(3) Polymer electrolyte fuel cells supplied pure hydrogen

The elementally technology of the fuel cell power generation system suitable for pure hydrogen fuel will be established, and will be verified the power generation system with 30 to 50 kW for fixed installation. The system shall be possible to achieve the efficiency at transmission terminal of about 45% (based on HHV, and about 50% based on LHV).

(4) Hydrogen refueling station

In order to establish the elementally and systematization technology of the stand alone type hydrogen refueling station aiming to supply fuel to the hydrogen automobile, a small scale testing system with 30 Nm³/h correspond to about 1/10.