PART TWO: MARINE USES OF FUEL CELLS Introduction verse main propellers or to activate side thrust propellers or water jets. Fuel cells have few mov- Why consider fuel cells for marine applications? ing parts, suggesting minimal manning require- As with land-based applications, economic fac- ments. Fuel cells are quiet, suggesting possible uses tors drive the search for improved commercial on anti-submarine warfare ships and seismic ves- marine power generation. These factors include sels. Finally, fuel cells offer greater endurance over capital and operating costs of propulsion and aux- batteries for some types of submerged operation. iliary power systems, cost and availability of fuel, and powerplant efficiency and reliability. Each of Despite potential benefits, the marine market these factors has a strong influence on the design is not in itself large enough to drive fuel cell tech- of ships and other equipment and powerplants. nology developments. Hence, it cannot be ex- Fuel cells have been considered as one of several pected that fuel cells will penetrate marine mar- alternative propulsion systems for the ships of the kets before they become firmly established in the future. Baham, for instance, has evaluated non- commercial utility sector, and shipbuilders will traditional propulsion systems for the commer- need to use and adapt products developed first cial shipping industry (under contract to the Mar- either for the power industry or for DOD. In addi- itime Administration), and concluded that four tion, cost advantages to onsite shore users due to systems show merit worthy of further investiga- large-scale production may not accrue to the ma- tion: nuclear, closed Brayton cycle, Stirling cy- rine industry. cle, and fuel cells .39 Technical barriers, of course, also remain to be Some of the benefits fuel cells would provide resolved. Barriers relating to the commercializa- to the utility industry could also apply in the ma- tion of fuel cells for transportation have been 40 rine field. Of special interest is the potential of noted by Walsh and Rajan. Most bear directly fuel cells for high efficiency, since this efficiency on cost, and include: may translate into fuel cost savings. Moreover, ● high cost of platinum and other catalysts; fuel cell efficiency is relatively constant over a ● thermal control problems; broad range of power settings. Such a character- ● difficult fuel processing requirements; istic suggests that fuel cells might be efficiently ● system complexity; employed in ships that frequently vary power de- ● startup time, especially in PAFCs; mand—e.g., towboats, ferries, offshore supply ● high reformer cost, especially in small systems; boats, or icebreakers. In addition to the poten- ● low volumetric power density; tial for providing main propulsion, fuel cells could ● carbon monoxide intolerance of electrodes; also supply auxiliary power and other needs. ● high cost of membranes (for solid polymer Several other characteristics of fuel cells could electrolyte fuel cells); provide benefits for specific applications. The fact ● low efficiency of the oxygen electrode; that fuel cells are of modular design enables flex- ● deterioration of the cost/performance ratio ibility in the arrangement of plant components in small systems; and and could lead to a more cost-effective layout of ● need to replace cells periodically. power and cargo spaces and of basic ship struc- ture. However, overall space and volume require- Required Characteristics ments of the fuel cell system and fuel will be greater than for present systems. As with other electri- Fuel cells must be competitively priced, relia- cal powerplants, the maneuvering problems of ble, and durable if they are to be accepted by the ships and tugs might be mitigated by the advan- maritime industry, They will be competing with tage fuel cells provide in enabling electric power other types of powerplants, especially with well- to be quickly switched to various locations to re- established diesel-electric plants, for a share of the .— 3qBaham, op. cit, towalsh and Rajan, op. cit., P. g. 20 21 marine market. Current low-speed diesels oper- Requirements for specific uses could vary consid- ating on residual fuel are very nearly as efficient erably, but these will be difficult targets to reach. as present PAFC powerplants, and the efficiency The major factor inhibiting fuel cell usage for of the conventional powerplants of the future is commercial marine applications is high cost. For expected to improve (see table 3). For example, military applications—e. g., for submersibles, diesel manufacturers are continuing their efforts small surface ships, and other specialized vehi- to improve the heavy fuels capability of their en- cles—mission requirements rather than cost are gines. Shipowners will not likely try new propul- generally more important. Thus, if fuel cell tech- sion systems without some very clear and con- nology is determined to have unique advantages vincing reasons to do so. Substantial advantages for a defined mission, high cost may not be the must be demonstrated, not just incremental im- major concern. provements in efficiency in order to induce po- tential buyers to switch from a long-established Other important factors to consider in select- powerplant to a new and relatively untested type ing a fuel cell or other unconventional powerplant of unit, include compatibility with salty air and water; system and fuel safety; ability to withstand the What would it take in order for the fuel cell to shocks, vibrations, and ship motions commonly become competitive in the commercial marine in- encountered at sea; ability to withstand and/or dustry? One view is that, for applications such control transient thermal shocks due to rapid as tugboat propulsion, total efficiency improve- changes in load; training and manning require- ments of 10 to 20 percent would be required, that ments; and constraints on weight and volume of installed capital costs would have to be on the or- the powerplant, auxiliary systems, and fuel. The der of $300 to $500 (1985 dollars) per kilowatt questions of fuel storage and possible additional (to compete with direct drive diesels), that power en route refueling time, as well as other elements densities (kW/cubic foot and kW/lb) would have related to fueling along the transportation route, to be reasonably close to those of the diesel en- have not been considered in most studies. The vol- gine, and that the fuel cell (in the near term, at ume of fuel required to travel between two points least) must be capable of running on distillate pe- may be much greater for certain types of fuel (e.g., troleum-type fuels customarily widely available. methanol). This may either place additional space and therefore size requirements on the vessel or necessitate additional refueling stops. Table 3. —Possible Marine Powerplants The ability to burn less expensive, widely avail- Fuel Efficiency (o/o) able fuel would be advantageous, as would the Current: capability to cogenerate steam, since, typically, Steam turbine with reheat steam (1,450 psig, 150 F) . Residual 32-36 ships have well-established uses for steam. Finally, Low-speed diesel ., ... Residual 39-41 fuel cells, like any other marine propulsion sys- Future conventional: tem, will need to be certified by the U.S. Coast Steam turbine with heat pressure, Guard and/or ship classification societies (e.g., high temperature reheat (2,400 psig, 1,050’ F) . Residual 35-39 the American Bureau of Shipping or Lloyd’s of Adiabatic diesel . Diesel 49 London) that they are safe, durable, and perform Naval Academy heat balance to acceptable specifications. Listed below are five engine . Diesel 43 Heavy-duty gas turbine, significant issues that will affect future marine fuel combined cycle . Residual 36-40 cell use. Closed-cycle combustion turbine Residual 40-41 Fuel cells.a Capital, Operating, and Maintenance Costs Phosphoric acid . Naphtha 41 Molten carbonate . Distillate 50 There is no question that it is technically feasi- Alkaline . Hydrogen 60 ble to propel a ship and/or generate auxiliary awlthout cornbltled cycle or other forms of heat recovery power using fuel cells. The issue is whether and/or SOURCE U S Department of Energy, A/ternatfve Energy Sources for Non.lflgh. way Trar?sportaf~on, DOE/CS/05438-T 1, Ju ne 1980 when fuel cells will be economical to purchase, 22 install, operate, and maintain. Manufacturers of cations. However, what little evidence there is fuel cells for the utility industry maintain that suggests that fuel cells will have a difficult time $1,000/kW (1985 dollars) is a realistic installed capturing a large share of the market for most ma- capital cost goal for a mature fuel cell system. As rine propulsion systems. technical improvements are made (e.g., by im- The relatively small size of the marine market proving power density, cell stack cooler arrays, will not likely encourage volume-based cost re- catalyst material, electrolyte management, and/or ductions; nor is the marine market large enough, inverter efficiency) and as automated production by itself, to stimulate development of alternative techniques improve, the capital costs may be re- fuels. For example, it has been estimated that, at duced further. However, in order for fuel cells to best, the U.S. domestic towboat industry might be competitive with direct drive diesel power- 43 acquire 50 fuel cell powerplants per year. Even plants in the commercial marine industry, capi- if all potential Navy applications utilized fuel cells, tal costs may have to be considerably lower than the domestic market could still not be considered $1,000/kW . large. Moreover, there are other reasons why de- Several studies of specific marine applications velopment of marine fuel cells may be difficult. have considered the question of capital costs in Baham notes that it is possible that competing detail. Notably, the Los Alamos National Labora- powerplants could enter the market first and es- tory (LANL) did a levelized life-cycle cost study tablish long-term commitments with major cus- of a typical 7,000-horsepower (hp) vessel capa- tomers; that ship operators and builders tend to ble of operating on inland or coastal waters.