Chiltern ‘HybridFLEX’ unit goes into passenger service
Diesel/battery hybrid will help lower emissions in station areas.
A TWO-car Class 168/3 has entered service with Chiltern Railways using Porterbrook’s diesel/battery hybrid technology.
Unit No. 168329 was launched using the 10.22 Marylebone-Aylesbury service on February 10, the culmination of four years of development between operator Chiltern, unit owner Porterbrook, and developer of the hybrid power pack Rolls-Royce.
The line out of Marylebone remains the last terminus in the capital that has not been electrified, and the FLEX project is viewed as an interim solution to reduce emissions and fuel costs for the remaining life of the 20-year-old fleet, while improving the air quality in and around stations.
No. 168329 was trialled at the Ecclesbourne Valley Railway in May 2021 (see RM July 2021) before undertaking trials at higher speeds over Chiltern routes last July. Since then, the unit has been involved in finetuning and driving training at two depots.
The unit has been fitted with two hybrid power packs – an MTU 6H 1800 engine, which meets Stage V emissions, and an MTU battery pack system and electric motor. A new six-speed gearbox has also been fitted, as has AdBlue exhaust treatment equipment.
The unit can accelerate from a station using the electric motor, with the diesel engine kicking in around 30mph. GPS technology allows the diesel unit to be cut out around 300 meters away from a station, and overall it provides an emissionfree approach and restart. Regenerative braking is also used.
What was noticeable on the inaugural public journey was the impressive smoothness of the unit on battery power as it accelerated quietly from a standing start. This faster acceleration could lead to a reduction in journey time too.
The unit is claimed to offer a 25% saving in fuel consumption, along with a similar fall in CO2 emissions, while NOx emissions are 70% less.