BOX 3-1: Box Fuel Cell Use in Urban BusesBoth the phosphoric acid fuel cell and proton exchange membrane (PEM) fuel cell can utilize hydrogen as a fuel,
and many current working prototypes of fuel cells use pure hydrogen as an input or obtain hydrogen by steam-
reforming methanol or by partial oxidation of methanol. The phosphoric acid fuel cell has been developed by H-
Power Corporation and fitted to an urban bus. The low-power density of the fuel cell requires that the bus carry
batteries to supply power for peak loads, with the fuel cells charging the battery at low loads. The fuel cell used in
the bus delivers a net power of 47.5 kW, and has a net efficiency of 42 percent at rated load, and 46 percent at its
maximum efficiency point which occurs at about 50 percent load. ’ The need to carry a large battery (and its
supporting equipment) for operation during fuel cell warmup and acceleration transients makes the overall system,
including electrical controls, expensive and bulky. Moreover, the methanol reformer is also expensive and
contributes to the overall inefficiencies in the fuel cell system. H-power claims that the transit bus in which this
system has been installed has an overall energy economy level similar to or slightly better than the diesel bus with
the same body and performance level.^2
Ballard Power Systems Inc. has converted a diesel-powered bus to use a PEM fuel cell with compressed
hydrogen as its fuel. The 1993 version uses a fuel cell that produces 120 kW at 160 to 280 volts. Range is 100
miles and the fuel cell itself takes up the space of three rows of seats. The vehicle can attain 45 mph top speed and
accelerates from zero to 30 mph in 20 seconds.^3 This vehicle achieved several firsts for PEM fuel cell systems:
higher power by a factor of more than 10 than previous air-breathing systems; highest voltage; cold, unassisted
startup in less than four seconds; and virtually instantaneous power response.^4 In 1993, Ballard projected
commercialization of a fuel cell-powered 75-passenger bus with 350 mile range by 1998, though no price was
discussed.^5
Ballard currently is developing a 275 HP PEM fuel cell engine designed to be installed into the standard engine
compartment of a full-size 40-foot heavy duty bus (a New Flyer D40LF Low Floor model).^6 The fuel will be
hydrogen from compressed storage and oxygen from air compressed by an electrically driven on-board
compressor. The goals of this phase of Ballard’s commercialization program are to obtain a 250-mile range and top
speed of 60 mph, with zero to 30 mph acceleration in 19 seconds and gradability of a starting capability at 20
percent grade and maintenance of 20 mph on an 8 percent grade.^7
(^1) A. Kaufman,“Phosphoric Acid Fuel Cell for Buses, Automotive Technology Development Contractor Coordination Meeting U.S. Department
of Energy, 1994.
(^2) Ibid.
(^3) "Innovative Fuel Cells Power Canadian ZEV Transit Bus," Ward’s Engine and Vehicle Technology Update, July 15, 1993.
(^4) P.F. Howard and C.J. Greenhill, "Ballard PEM Fuel Cell Powered ZEV Bus,” SAE paper 931817, August 1993.
(^5) Ibid.
(^6) P.F. Howard, Ballard Power Systems Inc., "Ballard Zero Emission Fuel Cell Bus Engine,” 1995.
(^7) Ibid.