management system automatically draws on the battery if more power is needed at any point, perhaps on an adverse gradient or for further acceleration.
To reduce emissions the engine can be switched off when it is not needed, such as when standing in a station, and will start up as the train approaches 30 km/h.
The key to reducing energy consumption is the use of the battery to store energy from braking, which would otherwise be lost. During braking the traction motors act as generators, with kinetic energy converted to electricity, rectified and the resulting DC used to charge the battery rather than being dissipated as heat. Allowing for energy losses in charging and discharging, Hitachi expects that around 80% of the regenerated braking energy will be recovered for the next powering cycle.
Power car No 43 089, now named after the Japanese word for falcon, and a MkIII TGS coach were donated to the project by Porterbrook in November 2005. Modification of the vehicles was undertaken by Brush Traction in Loughborough.
The 48 high energy density 1 kWh lithium-ion modules weigh around 20 kg each, and limitations on weight distribution meant the 1 tonne battery bank could not be installed in the power car. As a result, the battery is located in custom-designed racks in the adjacent coach. Future new-build vehicles would have the batteries incorporated into the design from the start, allowing the modules to be distributed throughout the train and reducing the weight of the supporting structures.
Hitachi is expecting to see a 20% cut in fuel consumption from the prototype, but higher savings could be made with production vehicles, as the use of battery power for acceleration means that a new-build vehicle could have a smaller diesel engine, cooler group and fuel tanks, resulting in an overall reduction in vehicle weight despite the battery.
Further weight reductions are expected as battery technology advances, driven by demand from the automotive industry Hitachi supplies the batteries for Toyota's Prius hybrid car. 'The weight saving is marginal today, but might be significant in a couple of years', said a Hitachi engineer at the launch. Battery life is currently estimated at eight to 10 years, but this is also expected to improve as the mass-market automotive technology matures. 'This is cutting-edge for rail, but exploits mass-market technology', explained Jon Shaw, Hitachi Europe's Safety & Approvals Manager.
Head of Project & Operations Keith Jordan drew a comparison with the silicon chip market, where rapid technological progress brought huge increases in capabilities at the same time as costs fell.
During May the project partners undertook initial trials of the HST at speeds of up to 96 km/h on the Great Central Railway, a heritage line which can offer exclusive use of a double-track main line for testing. From September Hayabusa will undergo six months of extensive trials as part of Network Rail's New Measurement Train (RG 7.03 p441). It is paired with a conventional HST power car to allow direct comparisons of performance and energy efficiency, and use in the NMT will require it to operate at up to 200 km/h to run between passenger trains. Network Rail Chief Engineer Andrew McNaughton said that NMT operations are similar to those of a train in regular inter-city passenger service, which will enable Hitachi to gather realistic performance data. 'The duty cycle of NMT is very onerous, which is why we think it makes a good test bed.'
The current project is focused on research for the future, with the production of a demonstrator train showing Hitachi's commitment to the technology, and willingness to support and develop it further.
Train operators are following the research with interest, but no orders are currently planned. Hitachi has the InterCity Express Programme (RG 2.07 p77) in mind, and McNaughton points out that 'there is a whole swathe of ex-British Rail suburban EMUs coming up for renewal,' offering one possibility for applying the technology to inner-suburban services in the future. McNaughton said that the po