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FC buses [86]. The hydrogen has been transported in liquid form to the depot and converted into gaseous form to refuel buses [83], it is then stored on site in gaseous form at 500 bar [86]. The buses themselves have developed throughout this project, where the first generation was powered only by a FC. These utilised a 250 kW fuel cell [82] and achieved a hydrogen economy of 18.4–29.1 kg H2/100 km [87]. The buses deployed as part of the CHIC project utilised a series hybrid configuration, with a 75 kW PEM FC from Ballard and a 0.5 kWh Bluways supercapacitor energy storage system [88]. This introduction of the hybrid system significantly reduced the hydrogen economy to <10 kg H2/100 km [87] and is one of the most significant results of the CHIC project in London. Figure 12 shows that the fuel economy of the buses operated as part of the CHIC project showed considerable improvements over those in the CUTE project. It can also be seen that the London buses performed better than the CHIC target, exceeding it by nearly 50%. For all of the London FC buses, the hydrogen is stored as a compressed gas at 350 bar, with the gas cylinders stored on the roof of the bus [82]. Between 2011 and 2016, the FC buses in operation in London have covered over 1.1 million kilometres [89], and a number of the FC buses have achieved the milestone of 20,000 hours of operation [90]. This reflects the improvement of availability seen over the course of the deployment of CHIC’s London fleet. Figure 13 shows the availability from January 2012 until May 2015. The monthly availability of London FC buses has also significantly increased after Figure 12. Average fuel consumption of FC buses in CHIC project (figure from FCH JU, 2016) [87]. Figure 13. Availability of London FC buses in CHIC project (figure from FCH JU, 2016) [87]. Development of Bus Drive Technology towards Zero Emissions: A Review http://dx.doi.org/10.5772/68139 49