Lightweight Electric/Hybrid Vehicle Design

Fig. 2.10 TXI London taxi.
Viable energy storage systems 41
become discharged would be if one travelled more than 400 km in one day. In this case the
battery would be rapidly charged at a service station. Since the battery is light the cost is
moderate and because it is not normally deep cycled a long life can be expected. Aluminium
test cells have already demonstrated over 3000 deep discharge cycles and operation down to
−80°C, as seen in the previous section.
At the present time we need to use larger fuel cells and smaller batteries similar to the hybrids
with thermal engines. The vehicle which is going to be the development testbed is the new TX1
London taxi chassis made by LTI International, a division of Manganese Bronze in Coventry,
shown in Fig. 2.10. This vehicle has been chosen because of growing air quality problems in
London. The City of Westminster is now an Air Quality Improvement Area. This is mainly due to
a large increase in diesel use which has resulted in unacceptable levels of PM10 emissions. Public
Transport is a major contributor, with the concentration of large numbers of vehicles in the central
zone.
Two types of fuel cell are attractive for use in vehicles – the PEM membrane and the alkaline
types, as described in the following chapter. Both types have undergone a revolution in stack
design in the last few years with the result that the stack (Fig. 2.11) is no longer the major cost item
in small systems, it is the fuel-cell controller and the power converter. In this section we shall
review the problems to be solved and offer some suggestions as to the likely course of development.
As always the fundamental issue is to convert a high cost technology for mass production civilian
use. Current (1998) fuel cells cost $1000 per kW and most of that cost lies in the control system
and power conversion. Stacks will cost less than $100 per kW in mass production. The challenge
is to reduce the control system cost. It is for this reason that most vehicle fuel-cell manufacturers
are opting to supply the stacks, and leave the car industry to manufacture the controller, Fig. 2.12.
This is an opportunity that Fuel Cell Control Ltd intends to take up by offering control systems
commercially.