# Hydrogen vs. Batteries: Comparative Safety Assessments for a High-Speed Passenger Ferry
## 6 Results and Discussion
### Battery Version  
To quantitatively evaluate the safety level of the battery ferry, six scenarios were developed on the basis of the situation and condition of doors and wind levels:  
* Scenario 1 (S1): this is the default condition with the fire doors shut, the FFS off, and no wind effect;
* Scenario 2 (S2): the FFS is on while keeping the fire doors shut and no wind effect;
* Scenario 3 (S3): the fire doors are open while keeping the FFS off and no wind effect;
* Scenario 4 (S4): the fire doors keep open and no wind effect while the FFS is on;
* Scenario 5 (S5): the fire doors are open and the FFS is on while adding a wind at 38 mph (61 km/h) towards the ferry's bow;
* Scenario 6 (S6): keep doors opened, FFS on, and add a wind at 6.9 mph (11 km/h) towards the ferry's bow.  
All these scenarios were simulated and discussed from the perspectives of fire and smoke paths. The smoke paths under different scenarios can indicate the time to reach the evacuation area.  
Figures 15-20 show the smoke in S1-6 with different conditions of fire doors, FFS, and winds. Figures 15 and 16 show the smoke trapped inside the battery room, with the only difference being the FFS working (green particles in Figure 16). Hence, the risk for passengers is low as long as the smoke/fire does not escalate in adjacent places, considering that fire doors are kept closed, preventing potential further damage.  
In S3 and S4, the situation of the fire door open was simulated, and the smoke paths are presented in Figures 17 and 18. Smoke was mostly concentrated at the aft of the main deck, but in S3, smoke was not blocking the evacuation exit, since it was rising and released into the atmosphere. It took around 6-8 s for the smoke to reach the aft extent of the main deck in S3, and until the end of the simulations, there was no significant difference in the accumulation of smoke at the back of the main deck.  
In the last two scenarios, two wind speeds were integrated into the model to see the smoke movement under extreme and average wind conditions (Figures 19 and 20). It is apparent in S4 and S6 that the smoke accumulated in the evacuation region. The smoke reached the evacuation region in about 13 s in S4 and it took about 4 s to blow the smoke to the evacuation region; following this, the smoke was blown away and dispersed until accumulated again in 12 s. In S5, due to the extremely strong wind, there was no similar accumulation phenomenon. It was observed with the mixture of the agent from FFS in S4, S5, and S6 that the mixed smoke had a higher density than air, and therefore the mixture moved downward and accumulated, different from S3, in which the smoke rose and was released into the atmosphere.  
Figure 16: Simulation of scenario 2.  
Figure 17: Simulation of scenario 3.  
Figure 19: Simulation of scenario 5.  
Figure 18: Simulation of scenario 4.  
To identify the fire conditions under different scenarios, the heat release rates were monitored, as shown in Figure 21. The observation from S1 and S2 is that the FFS reduced the fire time by about 3 s. This means that the selected FFS system can delay the fire by 30%. In all other cases, all the fire doors were open, and the air was continuously circulated for the fire; hence, the HRRs fluctuated significantly. When there was a high wind effect with a velocity of 61 km/h towards the bow of the ferry, with FFS on and firedoors open (S5), the highest heat release rates were observed between 15 and 30 s, varying between 1600 and 2300 kW with a fluctuating nature (Figure 21).