9. Task9 Development of Hydrogen Transportation and Storage Technology

9.1 Development of Liquid Hydrogen Transportation and Storage Facilities

9.1.1 R&D Goals

The second phase of WE-NET started this year with the merger of Liquid Hydrogen Transport Tanker Development Section and Liquid Hydrogen Storage Facility Development Section, who took over assignments from last year. We are going to conduct elemental tests of insulation structure that is a common key technology of both transport and to establish the data base of thermal insulation performance as well as strength at liquid hydrogen temperature for many kinds of insulation structures. It is expected that higher contact load and medium thermal load will be put on a contact type specimen in the future. In order to increase measurement accuracy of the specimen, high-function of the device will be required. To this end, we measured background thermal load of thermal insulation performance test, which is critical to thermal insulation performance of low-thermal load specimen.

9.1.2 Results in FY 1999

9.1.2.1 Remodeling of Thermal Insulation Performance Testing Device

In order to enhance performance of testing system for thermal insulation performance, a hardware component (hot plate) was remodeled and appendages were added. Major remodeling was made on following points.

(1) Remodeling of Hot Plate: contact type (20K side of the device contacts with the specimen)
The hot plate was remodeled and rigidness of the guard vessel and the measurement vessel was checked so as to increase contact load of the specimen and the bottom of vessels for guard and measurement, from 400kg to 3 tons.

2) Addition of Emergency Shutdown System: In a thermal insulation performance test, evacuation caused by emission of gas released from specimen may continue for about 1 month. The one-month long evacuation may lead to power failure, water failure, and vacuum down. Emergency shutdown system was added to counteract such situation.

(3) Addition of Mass Measuring Gas Analyzer: Mass gas analyzer (quadrupole gas analyzer) was added with the aim of collecting data of gas released from the specimen.

(4) Addition of Mass Flowmeter: 2 types of mass flowmeter were used so far;
- 1) for high flow with the rated flow of 100 l/min (66.6W by estimate);
- 2) for low flow with the rated flow of 5 l/min (3.3W).
A flowmeter with the rated flow of 20 l/min was newly adapted to measure medium flow.

After remodeling, background tests were conducted in KHI. The testing system has adapted thermal protection flat calorimeter system, which measures evaporation and converts the result to heat flow rate on the specimen's surface for test. Since heat input from the outside may cause errors, heat input was measured. The result was very small, from 0.1W to 0.2W.

In the test, we verified how the evaporation varies according to the variation of pressure variation. The average evaporation is about 0.15-0.2Nl/min. When the pressure is lower, the evaporation is higher. The evaporation declines with the rise in the pressure. During the period of high atmospheric pressure, the slight change of pressure rate corresponds to the change of evaporation rate.

9.1.2.2 Design of Specimen for Thermal Insulation Performance Test

As specimens for thermal insulation performance test, we designed 4 types; 1) solid vacuum insulation structure specimen (with joints on the ordinary temperature side and with joints on the low-temperature side); 2) membrane laminated vacuum insulation structure specimen; 3) vacuum panel insulation structure specimen; and 4) vacuum laminated insulation structure specimen. Among them, tests were conducted on solid vacuum insulation structure specimen (with joints on low-temperature side) and membrane laminated vacuum insulation structure specimen.

(1) Solid vacuum insulation structure specimen
Solid vacuum insulation structure specimen is a specimen with polyurethane foam (PUF) and a joint. It is attached to a tank while a clearance between the specimen and the low-temperature side (20K side) is kept. Heat transfer analysis was conducted by setting the joint position as computational parameter. Thermal effect on the joint part determined the position of joint (200mm from the center) on the test side (bottom of the measurement vessel).

(2) Membrane laminated vacuum insulation structure specimen
Membrane laminated vacuum insulation structure specimen is composed of FRP tube pole and laminated insulator. In order to reduce heat input through conduction of FRP tube structure, thermal stress and strength of FRP tube were analyzed. As a result, the form was changed from single tube type to multiple tube type. As laminated insulator, aluminum two-sided evaporation polyester film was used. It was attached to low-temperature sides (20K side) of measurement vessel and guard vessel, multiple flange part and mainframe.

(3) Vacuum panel insulation structure specimen
Vacuum panel insulation structure specimen is a vacuum panel containing polyurethane foam (PUF). Polyurethane foam and glass wool are used for the joint part. Heat transfer analysis was conducted to verify the impacts of heat inflow on the side face of specimen and impacts of thermal contact resistance between specimen and joint parts or vessel.

(4) Vacuum laminated insulation structure specimen
Vacuum laminated insulation structure of a full-scale tank was studied. While studying the form of specimen to simulate the structure, technological problems such as measurement error were extracted.

9.1.2.3 Results of Thermal Insulation Performance Tests

Last year, performance test was conducted on solid vacuum insulation structure specimen (without joint, contact type). In this year, solid vacuum insulation structure specimen (with joint on the low-temperature side) and membrane laminated vacuum insulation structure specimen were tested. Results of those tests were as follows.

(1) Solid vacuum insulation structure specimen
In the previous year, performance test of solid vacuum insulation structure specimen (without joint, contact type) was conducted. Based on the results, radial heat flux was taken into consideration. Radial heat flux was revised, thermal contact resistance was discussed and a correlation between the surface roughness of the specimen and thermal resistance was studied.
Solid vacuum insulation structure specimen (with joint on the low-temperature side) was set with clearance between the low-temperature side (20K) and specimen kept, and its heat conductivity was determined. The rate was higher than the analytic value, which may be due to insufficient emission of urethane foam gas.

(2) Lamination vacuum insulation structure specimen
Lamination vacuum insulation structure specimen (FRP multiple tube) has a bolt tie-in that allow radial of multiple tube flanges. The specimen was bonded to the bottoms of a measurement vessel and guard vessel with two-sided adhesive tape. Heat flux (heat conductivity) was 5 to 6 times of the analytic value, whose cause was found when the specimen was released after the test. It was because the measurement vessel was fallen off the laminated insulator and had contact with the high-temperature side.

9.1.2.4 Strength Test of Heat Insulator

With the use of foamed glass (φ100mm, cylinder), low-temperature compression test was conducted at room temperature, in the states of liquid nitrogen and liquid hydrogen. To verify the shape effect of foamed glass, strength test of large-scale full block (610mm*410mm) was conducted. At room temperature, the result was about 1.12Mpa and scale effect was not verified. In the state of liquid hydrogen, compression test strength was 1.61Mpa, about 60% higher than that at room temperature. Depend on the cooling rate process, thermal shock may damage the specimen.

9.1.2.5 Study on Support Structure of Tank

Studies were conducted on the square tank and the spherical tank spherical tank designed in phase 1.

(1) Square Tank (IHI)

Future approaches were discussed.

(2) Spherical Tank (MES)

Yield strength of roughly designed tank support structure was evaluated under the condition of static load. It was found that temperature loading affects vertical directional surface stress of the skirt part and its load level is very low.

9.1.3 Research Plan for FY 2000

Based on the results of design testing of large-scale liquid hydrogen tanker and its storage facility, various insulation structures were proposed. The most important technological assignment is collecting data of insulation performance and insulation structure strength at liquid hydrogen temperature and tests are conducted to that end. Up to this year, tests were conducted on solid vacuum insulation structure specimen and membrane laminated vacuum insulation specimen, through which insulation data close to real-scale model are collected. It is planed to make detailed analysis of data and utilize the results for designing real structure from next year on. In addition, insulation tests will be continued with other types of specimens such as normal pressure insulation structure specimen and vacuum powder insulation structure specimen. For low-temperature strength test, foam glass was tested this year. In next year, microsphere insulator will be tested.

To respond to the wide spread of fuel cell cars in the near future, infrastructure for hydrogen gas supply system will be required. A system to liquefy, store, transport and supply byproduct hydrogen gas is regarded as promising one. Task 9 is aiming at development of large-scale system of liquid hydrogen transport and storage originally. However, studies on small capacity liquid hydrogen transport and storage system will be taken up as short-and-medium term challenge, and feasibility study of the system will be conducted to extract technological problems.