12 JULY 2017 • FOGHORN FOGHORNFOCUS: ENVIRONMENTAL ISSUES Figure 3 - Concept Design of a 35 knot, 150 passenger Hydrogen Fuel Cell Ferry (Source: EBDG) instead of 300 passengers that would be found on an equivalent diesel- driven vessel. • The combination of high capital cost, expensive fuel (currently), and low carrying capacity resulted in a vessel that was technically feasible but not economically viable. In order to further assess the pos- sibilities of a hydrogen-fueled ferry, EBDG applied the technology to a conventional car ferry. EBDG selected a vessel that was previously designed for Pierce County, WA, that has reliable data readily available on capital and operating costs (see Figure 5). This allowed EBDG to benchmark perfor- mance and financial assumptions as the design was modified for hydrogen fuel cells. The reference vessel has the following characteristics (see Table 1). The U.S. Coast Guard does not allow gas fuels to be stored under- neath accommodation spaces due to the risk of a gas leak creating an explosive condition. Therefore, the fuel storage was placed on the open deck adjacent to the passenger spaces. Since hydrogen is significantly lighter than air, any leaking hydrogen rapidly moves up and away from potential ignition sources. The liquid hydrogen is converted back into a gas state in a cold box adjacent to the fuel storage tank. The gas fuel is then carried in double- walled piping in a dedicated, well- ventilated trunk down to the fuel cells located in the hull under the main deck. The fuel cells are arranged in racks similar to lithium ion batteries. The fuel cell room is also well-ventilated and monitored to detect any gas leaks and to prevent the accumulation of gas. Since the ferry is double-ended, the powering is split approximately 80 percent to the pushing propeller and 20% to the pulling propeller. This means that the total propulsive require- ments are approximately 830 kW. If we assume a 10 percent conversion loss for the electrical motors and control- lers, plus add the shipboard electrical consumption of 105 kW, the total elec- ITEM ENGLISH UNITS Length Overall: 216 ft Beam: 68 ft Depth: 16.5 ft Design Draft: 10.25 ft Lightship Weight: 733 LT Full Load Displacement: 996 LT Car Capacity 54 vehicles Passenger Capacity 325 Crew Size 5 Main Propulsion 2 x 1050 hp Electrical Capacity 2 x 110 eKW Table 1.Vessel Characteristics. Figure 4 - M/V Steilacoom II (Source: EBDG)