10 JULY 2017 • FOGHORN FOGHORNFOCUS: ENVIRONMENTAL ISSUES I n 1970, the phrase “hydrogen economy” was introduced by John Bockris. It referred to a world where hydrogen could be used as a transportation fuel, provide sta- tionary power generation, and serve as an energy buffer for renewable forms of energy such as solar and wind. Hydrogen is the chemical element with the lowest atomic weight and can be readily combined with other elements to form a variety of molecules. As the chemical energy inputs into a fuel cell, hydrogen can combine with oxygen to create water while generating electricity and heat (see Figure 1). The energy efficiency of a fuel cell is generally between 40% and 60% (see Figure 2). Although the fuel cell was invented in 1838, the first practical use came in the 1950s and 1960s as NASA applied the technology to powering spacecraft and satellites. Fuel cells have no moving parts and are therefore very reliable and require minimal maintenance. Recently, fuel cells have been applied to stand-by power generation, transportation (automobiles, buses, forklifts), military applications, and portable power systems. The largest fuel cell plant is a 59- megawatt facility in South Korea. In marine applications, the German Type 212 submarine uses two fuel cells of 120 kilowatts each. In 2015, Seattle-based Elliott Bay Design Group (EBDG) was selected by Sandia National Laboratories (Sandia) as part of a team to look at the feasibility of hydrogen fuel cells for a commercial marine application. Sandia chose a chal- lenging scenario: Is it technically and economically feasible to operate a high speed passenger vessel in San Francisco Bay using hydrogen powered fuel cells and producing zero emissions? The Sandia team worked closely with the U.S. Coast Guard and the American Bureau of Shipping to evaluate the safety regulations for small passenger ferries and gas-fueled vessels. Sandia, along with EBDG, also looked at commercially available technology to see if there were “off the shelf” components that could be used. EBDG developed a vessel design (see Figure 3) that met the perfor- mance requirements. This then provided the basis for esti- mating capital and operating costs. Acopy of the final report may be found at: http://energy.sandia.gov/transportation- energy/hydrogen/market-transformation/maritime-fuel- cells/sf-breeze/ Some lessons learned from that project: • If significant quantities of hydrogen are required, storing the hydrogen as a cryogenic liquid is more space efficient. Also, the combination of fuel and storage tank weighs less than a compressed hydrogen system and has lower capital cost. The Hydrogen Fueled Ferry By John Waterhouse, PE, PMP, FSNAME, Chief Concept Engineer Figure 1. Block Diagram of a Fuel Cell (Source: Wikipedia) Figure 2. Performance Characteristics of a PEM Fuel Cell (Source: Hydrogenics) • Refueling frequency is a critical design decision. Carrying a minimal amount of fuel reduces weight and space re- quirements, which for a high speed vessel means reduced propulsion requirements, that in turn further reduces the fuel storage requirements. • The set of safety regulations developed for LNG as a cryogenic fuel can be readily adapted for use with liquid hydrogen. • The weight and space requirements for the fuel storage, the fuel cells, and the electrical propulsion equipment meant that the carrying capacity was only 150 passengers