Lightweight Electric/Hybrid Vehicle Design

Process engineering and control of fuel cells, prospects for EV packages 89
Standard test conditions used by Ballard for SPFC stack systems are a pressure of 3 atm,
stoichiometry of 2.0 for air and 1.5 for hydrogen. Their MK 513 stack is reported 9 to give 13 kW
at 0.58 V and a power density of 300 W/kg and 300 W/l. The same reference quotes the performance
of the stack developed for Daimler-Benz as achieving 32.3 kW at 0.68 V, and power densities of
1000 W/l and 700 W/kg, which meet the target set in 1990 by the US DOE for automotive fuel
cells of 560–1100 W/kg.
The major challenges for fuel cells are (a) to develop systems which require similar mass and
volumes to the engine plus fuel tank of current gasoline or diesel cars, at competitive prices when
mass produced and (b) development of the required fuel infrastructure.
4.6 Steps towards the fuel-cell engine
Earlier sections of this chapter, contributed by Roger Booth, have dealt with process engineering
of the fuel-cell stack. Hereafter the steps leading to the development of viable fuel-cell engines are
considered. While hybrid drive vehicles, using conventional battery-electric and thermal-engine
power sources, provide improved fuel economy and a viable solution for urban operation, the
fuel-cell powered vehicle is now seen as the long-term option. Already it is realized that thermalengine
driven vehicles can never provide the necessary fuel economy and emissions control required
by world governments, primarily because the thermal engine is running at 10% of its total power
potential for most of its time and there is no known way of eliminating CO emissions from it.
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Over the next 20 years, people using HC vehicles are going to face increasing fuel scarcity,
increasing fuel cost and ever increasing restrictions on use and size of vehicles, because of the
emissions they produce. The high operating efficiency and zero emission characteristic of the
fuel-cell vehicle are strong arguments for its adoption. But the passage into the period of the
hydrogen-fuel economy has to be a gradual and peaceful one, requiring considerable changes in
attitude by the motoring publics worldwide.
4.6.1 FUEL CELLS: TOWARDS A PAINLESS TRANSITION
The only way to break out of the cycle of increasing fuel costs and heavier restrictions is for
motorists to accept the necessity to move over to a hydrogen-fuel economy in the shorter term and
to lessen its impact by replacing their current vehicles, when the time comes, with much more
fuel-efficient types. There are two advantages to the hydrogen economy: if early hydrogen-fuelled
vehicles are not very efficient it does not matter because pollution-wise they have zero emissions,
and more importantly, the existing cost of expensive exhaust after-treatment is removed.
The publication by the OECD International Energy Agency in 1998 of ‘World Energy Outlook’,
a year after the Kyoto Earth Summit, was a pivotal point in understanding world energy and
pollution problems. The basic message was that, as people now live longer, energy usage and
pollution rise exponentially and a ‘brick-wall situation threatening in ten years’ time means that
we cannot stay as we are’. It was also from this point that the major G7 economies took global
warming seriously. China, too, takes it seriously, realizing that nine-tenths of its population live in
its southeastern corner delta region, which could be subject to flooding if global warming is not
seriously addressed. World oil supply is expected to peak in 2010 and then tail off; this is unless
the cost can be met of tapping into the vast oil deposits beneath the polar icecaps. But North
American motorists remain blissfully unaware of these threatening situations. While the UK and
Europe pay what gasoline and diesel actually costs, in total, US users have an enormous effective
subsidy which hides the governmental costs, and keeps them oblivious to the problems involved.
Fuel/vehicle taxes in the UK pay for road building, health care related to accidents, also defence
costs relating to naval protection of oil rigs, whereas in the USA the petrol price paid at the pumps