Page 25: of Marine News Magazine (March 2017)

Pushboats, Tugs & Assist Vessels

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HYBRID PROPULSION lliott Bay Design Group (EBDG) serves many ferry published data on their operating costs so we can have con- customers in North America. These clients read the ? dence in using their information to evaluate how different

E trade publications and see various articles on new technologies will impact both operating costs and capital technologies such as hybrid propulsion, battery powered costs using the geared diesel con? guration as the baseline.

vessels, or zero emission vessels. After ? nishing such an The key to any ferry operation is to understand the article they ask themselves: “What advantages would that route. For Pierce County the ferry crosses between Ander- technology bring to my operation and what will it cost”? To son Island and the town of Steilacoom over a distance of that end, EBDG developed some tools to help answer approximately 3.5 nautical miles. With a service speed of those questions. 11.5 knots the vessel is underway for 21 minutes and in

A case study to evaluate ? ve different propulsion alter- dock for 9 minutes for each half hour voyage. For the pur- natives for a conventional ro-pax ferry was devised, using pose of our study, an initial departure at 6 am every morn- the following options: ing and a total of 13 round trips per day were all used as • Geared Diesel (Baseline) assumptions. Costs were based on the ferry operating 350 • Diesel-Electric days per year. The characteristics of the ferry used for this • Diesel-Electric with 13.4 megawatt battery bank study are shown in Table 1. • Diesel-electric with 26.8 megawatt battery bank EBDG has developed a spreadsheet tool called ShipCalc • Hydrogen Fuel Cell to develop initial estimates of vessel weight, powering,

To calibrate the results, EBDG selected a long-term cli- electrical demand, etc. ShipCalc uses weight and cost pa- ent, Pierce County, for whom the ? rm has previously de- rameters based on the U.S. Navy Ship Work Breakdown signed and built two double-ended ferries. The County has Structure (SWBS). Resistance for displacement vessels is

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Marine News is the premier magazine of the North American Inland, coastal and Offshore workboat markets.