Yohsuke tamura Japan Automobile Research Institute Kenji Sato Toho University

1. ID 146 The possibility of an accidental scenario for marine transportation of fuel cell vehicle -Hydrogen releases from TPRD by radiant heat from lower deck- Yohsuke tamura Japan Automobile Research Institute Kenji Sato Toho University

2. Situation of activated TPRD TPRD Hydrogen gas TPRD Hydrogentank Hydrogentank Flame Ignition The hydrogen releases are immediately burned by the flames existing around TPRD.

3. Marine transportation for FCV A pure car carrier or a ferry boat having decks of steel structure. http://www.iwakitec.co.jp/machineryMarineuse.htmより

4. An accident scenario of fire from lower deck HFCV Upper deck Hydrogen cylinder TPRD Deck floor heated by the fire Lower deck

5. An accident scenario of fire from lower deck Fire by parts of the vehicle Deck floor heated by the fire

6. An accident scenario of fire from lower deck Hydrogen flame No explosion!

7. An accident scenario of fire from lower deck HFCV Upper deck Hydrogen cylinder TPRD Deck floor heated by the fire Lower deck Assuming that TPRDis activated by the radiant heat without the presence of flamesin upper deck, hydrogen gas will be released by TPRD to form combustible air-fuel mixtures which may cause explosion.

8. An accident scenario of fire from lower deck TPRD from hydrogen gas Assuming that TPRDis activated by the radiant heat without the presence of flamesin upper deck, hydrogen gas will be released by TPRD to form combustible air-fuel mixtures which may cause explosion.

9. Contents To investigate the possibility of this accident scenario, • An experimental study of the relationship between radiant heat and TPRD activation time. • When the temperature of the deck is self-ignition temperature of the plastic parts of the vehicle, radiant heat flux q of TPRD is calculated. Then q and qc are compared. • In the absence of flame, it was examined whether or TPRD is activated by radiant heat from the floor.

10. Thermocouple Performance test for TPRD by radiant heat Thermocouple #A #B #C Fuse metal type #D Glass bulb Glass bulb type

11. Test method To predict TPRD’s activation time under radiant heat

12. TPRD Body Temperature when TPRD activated Fuse metal type TPRD’s (A,B,C) body temp. > TPRD’s activation temp. Glass bulb type TPRD(D) body temp. < TPRD activation temp.

13. TPRD Body Temperature when TPRD activated TPRD A,B,C (Fuse metal type) The heat must be transmitted from the body surface to the embedded fuse metal through the TPRD body having a certain heat capacity. TPRD D (Glass bulb type) The radiant heat reached the glass bulb directly from an aperture in the TPRD body. #D Glass bulb type

14. Relationship with TPRD activation time ＆ radiant flux

15. Relationships with 1/TPRD activation time ＆ radiant flux Critical radiant flux qc

16. Relationships with TPRD activation time ＆ radiant flux

17. Discussion - Radiant Heat Model  Radiation shape factor

18. Discussion - Fire by tire Heat flux q received by TPRD when the floor temp. was 400°C, the self-ignition temperature of tire rubber. The emissivity ɛ＝ 0.16~0.35 (TPRD’s body:stainless steel) Stefan-Boltzmann constant σ =5.67  10-11[kW/m2K-4] The critical radiant flux necessary for TPRD activation is 5 kW/m2. TPRDs would not activate under the floor temperature condition equal to the self-ignition temperature of tire. Cabin would be burnt down due to ignition of tire before TPRD activation.

19. Discussion - Fire by undercover http://toyota.jp/mirai/performance/ FCVs have a plastic undercover. Undercover : Polypropylene ⇒ Softening temperature 128 °C Self-ignition temperature 498 °C When subjected to radiant heat from lower deck, the polypropylene undercover first softens and drops onto the floor before TPRD activation.

20. Discussion - Fire by undercover Deck floor temp. 500°C (the self-ignition temperature of PP) Calculated by radiation model The radiant heat qreceived by TPRD ：7 kW/m2 Relationships with TPRD activation time ＆ radiant flux TPRD activation needs to be exposed to radiant heat for 90 min.. The PP undercover fallen onto the floor would have undergone self-ignition before TPRD activation.

21. Conclusions This study was conducted to examine the accident scenario for FCV marine transportation during which fires may break out in the lower deck and induce TPRD activation in the FCVs parked on the upper deck. The experiment on relationships between TPRD activation time and radiant heat from the lower deck found that it took at least 90 minutes for TPRD to activate under the condition of lower-deck temperature reaching the spontaneous ignition temperature of FCV tires and polypropylene parts; that even if polypropylene parts are melted and self-ignited under radiant heat, hydrogen releases would be burned immediately by the flames present in the vicinity. Accordingly it was concluded that the explosion of air-fuel mixtures assumed in the accident scenario cannot occur in the real world.

22. Thank you for your attention. ご清聴頂きまして有難うございました． This paper introduces one of the achievements of the “technology development project for hydrogen production, transport and storage systems” commissioned by New Energy and Industrial Technology Development Organization (NEDO) in Japan.