APPENDIX B
A SYSTEMS APPROACH TO REDUCING FUEL CELL
COSTS
INTRODUCING FUEL
CELLS TO
THE COMMERCIAL
PUBLIC TRANSPORT
MARKET
Fuel cells are now recognised as the key technology
in the process of weaning the modern world from its dependence
on fossil fuels and leading it into a new age of hydrogen energy.
The principal obstacle still to be overcome is the high cost of
fuel cells. In transport, for example, one kilowatt from a fuel
cell costs $3,000, compared with $30 per kilowatt for an internal
combustion engine. Somehow a reduction of two orders of magnitude
has to be achieved if fuel cells are to compete with alternatives
in the commercial market for transport.
There are two complementary approaches to achieving
this reduction. The first and most obvious is to increase the
efficiency of the fuel cell in producing electricity from hydrogen.
But producing electricity is not an end in itself. It is rather
a means to enable us to achieve our end objectives of providing
people with useful services such as heat, light and mobility.
The cost of mobility can therefore be reduced just as much by
increasing the energy efficiency of the system in which the fuel
cell is used, as by increasing the efficiency of the fuel cell
itself.
Ultra Light Rail is a transport system designed
to eliminate the two orders of magnitude gap between the fuel
cell and the internal combustion engine. The first step is to
increase the efficiency of the vehicle system in which the fuel
cell is used. This can be done in a number of ways but the most
dramatic "step change" in energy efficiency can be achieved
by using a vehicle running with steel wheels on steel rails. This
immediately reduces the energy requirement by a factor of three,
since the lower rolling resistance allows a tram to use only one
third of the energy required by a similar sized bus.
Further cost reductions in the vehicle system
can be achieved by introducing an on-board energy storage system
in a hybrid electric drive train, similar, in principle, to that
used in the Toyota Prius and other cars and even in some buses.
This makes possible a lower rating for the prime on-board power
source which is required only to run at its optimum level, in
order to keep the energy storage system topped up. It also allows
for the energy from braking to be recaptured and used, rather
than dissipated in heat vented to the atmosphere. Still more efficiency
can be introduced by integrating the electric motors into the
wheels. The overall weight of the vehicle can be reduced by each
of these innovations whilst the body itself can be manufactured
from carbon fibre composite materials in a monocoque form. The
whole process, using standard proven technology, creates a spiralling
cost reduction, resulting from each innovative feature.
Using only some of these features, recent practical
test work carried out, with support from a Carbon Trust grant,
has shown that a 25 kilowatt fuel cell would be sufficient to
power a light tram with similar capacity to the fuel cell buses
currently running in London under the EU's CUTE programme. These
buses are doing an invaluable job in demonstrating to the public
that fuel cells are no different to internal combustion engines
in performance and safety. However, the buses themselves are grossly
inefficient in commercial terms, costing, as they do, more than
five times as much as a similar diesel bus and requiring 250 kilowatts
fuel cell to operate them. The next logical step in commercialising
the operation of fuel cell powered public transport vehicles must
therefore be to integrate the fuel cell into an energy efficient
tram. This will eliminate one order of magnitude in the cost differential.
Eliminating the second order of magnitude involves
engineering down the cost of the transport system within which
the vehicle operates. Conventional trams are, in effect, railway
trains only slightly adapted to run on roads. Using overhead continuous
electrification they have to earth the current through the rails.
This necessitates underground insulation and removal of utility
services from under their path. The excessive weight of the trams,
together with their insulation needs, means that heavy rails and
a massive substructure are required. Ultra Light Rail, using bus-type
vehicles adapted to run on rails, does away with this needlessly
expensive infrastructure. A further significant cost saving arises
from the superior durability of trams which normally have a life
of 30+ years as compared with 8-13 for buses. This has environmental
advantages as well as sharply reducing the amortisation cost of
operating trams as opposed to buses.
Installing an on-board power source allows the
ULR system to eliminate continuous overhead electrification and
the insulation that goes with it. The reduced weight of the tram
means that light rail can be used, which is easy and relatively
cheap to install and also to move when road excavations are necessary
to service utilities, which do not need to be moved. Light temporary
track can easily be laid for diversions.
ULR is designed to be the natural, zero-emission,
next-generation successor to the diesel bus. The passenger capacity
of the trams is therefore designed to be similar to the standard
city buses currently in operation all over the world. Rather than
increase the size, weight and obtrusiveness of the public transport
vehicle it is often preferable to use vehicles with a passenger
capacity of around 100 people, plus or minus 50%. As pedestrianised
areas are extended in city centres less obtrusive, pedestrian-friendly
trams will increasingly be in demand. Passenger capacity can most
easily be increased, with maximum flexibility, by increasing the
frequency of the service, which is not a problem on a tram track.
A 100 passenger tram every three minutes is more convenient and
popular than a 200 passenger tram every six minutes. The extra
driver cost provides additional employment and contributes more
to the local economy than amortising heavier hardware.
All these features, which differentiate ULR
from conventional tram systems, result in massive savings in infrastructure
costs. Typically a ULR system can be installed at a cost of around
£1 million per kilometre as compared with £10 to £15
million per kilometre for a conventional heavy tram system. This
eliminates the second order of magnitude and delivers a public
transport system which is non-polluting, popular and low-cost.
Light, zero-emission trams with on-board power
generation can be used under cover, inside buildings such as stations
and shopping malls, where buses cannot penetrate. A major advantage
in planning to replace buses with light trams is that it does
not involve persuading the public to accept a new unpopular transport
system with which they are not familiar. On the contrary the reverse
is true, as trams are universally more popular with the public
than buses, as market studies around the world have shown. This
popularity is conducive to higher levels of modal shift as people
are more willing to leave their cars behind and travel on the
tram system. This in turn has a positive knock-on effect on property
values, which can be used to facilitate the funding of city regeneration
projects.
ULR is designed to bridge the current cost gap
between internal combustion engines and fuel cells by using standard
production fuel cells more efficiently, rather than waiting for
fuel cell prices to come down. However, as they do come down these
systems will simply become still more economical.
James Skinner
October 2004
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