Hydrogen Fuel Cell Bus Technology State of the ... - NEXTHYLIGHTS

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Hydrogen Fuel Cell Bus Technology State of the Art Review * Fuel economy depends on drive cycles. It is worth noting that there is not a standard drive cycle to date and hence these figures are indicative of best of class urban drive conditions only. ** Availability is defined as the percentage of days of actual service compared to the number of day of scheduled service (over the year). *** Best of class performance range. Among the hydrogen bus options, hybridised fuel cell designs demonstrate far better fuel economy than non-hybridised fuel cell and hydrogen-fuelled internal combustion buses. The vast majority of hydrogen buses are now being built in a hybrid fuel cell configuration and it is assumed that this will be the basis for commercialising hydrogen buses. State of the art hybrid fuel cell buses provide one of two genuinely zero emission bus options for the urban transit market (the other is an electric drivetrain - typically in a trolley bus). Depending on the source of hydrogen, the buses can provide a zero carbon solution for public transit. Even using today‟s production from natural gas, there are considerable carbon savings available over conventional diesel buses (up to 50%). Other advantages over diesel vehicles include: substantially higher fuel efficiency (up to twice a diesel bus on a calorific basis) reduced urban noise, and in the long term reduced maintenance requirements (due to fewer moving parts and hence less lubrication etc.) The EC‟s HyFLEET:CUTE project proved that hydrogen buses can be operated reliably – a availability figure of 92% was achieved in this trial. It is important to note that this was a well-controlled trial (with maintenance technicians at each site) and did not involve a hybrid drivetrain. 72
Hydrogen Fuel Cell Bus Technology State of the Art Review Hybrid fuel cell bus trials, by contrast, have shown relatively poor availability (55- 80%) in trials before 2010. These will need to be improved before the technology can be rolled out outside small demonstration trials. The next generation of hybrid fuel cell bus trials (starting 2010) are designed to prove that the technology can achieve availability standards over 90% which will be sufficient to begin to commercialise the technology. The next generation of bus demonstrations (such as CHIC 20 ) are also aimed at understanding the fuel economy of next generation FC buses. Initial tests suggest they will achieve the lower bound of the fuel consumption range, e.g. up to 40% improvement over an equivalent diesel route at parity of calorific content. The main technical constraints for fuel cell buses, compared to conventional diesel vehicles are: o Fill time – which is currently around 10 minutes (best available is 7 minutes), compared to a diesel fill times of approx. 3 minutes. This creates logistical problem for bus operators. o Availability – equivalent availability to diesel vehicles has not yet been demonstrated for fuel cells in hybrid configurations. This is expected to be achieved in the next generation demonstrations. o Lack of infrastructure – meaning that dedicated hydrogen fuelling infrastructure is required at hydrogen bus depots – this is bulky and also requires very high availability as there are no local back-up options available Diesel hybrid vehicles are currently gaining traction in the market for environmentally benign urban buses. These have a total cost of ownership higher than diesel buses, suggesting public authorities are prepared to fund some additional cost of operating environmentally friendly However, a Total Cost of Ownership analysis for today‟s fuel cell buses suggests that the cost of operating a fuel cell bus today is over three times that of a conventional diesel bus. This additional cost is not acceptable to bus operators, meaning the technology must reduce in cost to gain genuine commercial traction. There are two main approaches to cost reduction. In the first, progressive generations of fuel cell systems designed for buses are projected to reduce fuel cell system costs below €2,000/kW (from over €4,000/kW today), whilst increased volumes of fuel cell buses reduce the costs for bus builders to assemble and sell the buses. This would reduce fuel cell bus costs to a lower bound of approximately 20 http://chic-project.eu/ 73
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