Bus repower to zero-emission: Increasingly attractive option

Mercedes Citaro bus having undergone repower to battery electric

With the consultation on the end date for sales of new non-zero-emission buses currently live, there are lots of discussions underway about how that date might impact the values of second-hand diesel buses.

Some people believe that the value of diesels could rise if the end date for new sales is set too early and operators are unable to replace older diesels with zero-emission buses (ZEBs). Others believe that values will fall as there may already be a glut of diesel buses in the market, and that local authorities will drive operators to zero-emission through local policies and tendering conditions.

Electric bus repower could give ‘taster’ of zero-emission

The general feeling from the discussions so far is that operators want to roll out ZEBs at a slower pace as technology continues to evolve alongside new operational and cultural practices. Supply challenges in the market and the long lead times for upgrading and installing grid connections are resulting in longer planning cycles for introducing ZEBs compared to procuring new diesels.

This alongside funding shortfalls in the light of reduced passenger journeys post-COVID-19 and the tradition of procuring vehicles outright mean that operators are taking a cautious approach. One potential solution that may help operators to overcome some of these hurdles is converting or repowering diesel buses to zero-emission.

By removing the diesel engine and installing a zero-emission drivetrain, the operator can have a ZEB for a lower initial cost, increasing the residual value of the bus and reducing maintenance and fuel costs. Another advantage, particularly for smaller operators, is that repowering allows them to learn about zero-emission without having to fully commit. Staff can get used to ZEB technology and practices without having to transition a whole depot or route.

Experience of repowers in the UK is limited, with only a handful in operation. The key experiences so far have been around choosing the right vehicle (i.e., one that is not too old) and potentially investing in refurbishing key parts of it to prepare the vehicle for repowering, such as fitting a new drive axle.

Momentum growing for mid-life ZE retrofit

There are currently three different ZEB repower suppliers with solutions set to hit the road this year. Ricardo recently posted highlights of its hydrogen fuel cell-electric repower, which is set to go on trial in the coming weeks as part of the Teesside Hydrogen Transport Hub.

A key potential driver for seeing more repowers on the road is the new BSOG ZEB uplift in England of 22p per kilometre. That equates to close to £11,000 per year for a bus covering 50,000km and close to £60,000 after five years’ operation, the minimum expected lifetime of a repower.

Zemo Partnership has undertaken a project to create an accreditation scheme to ensure that future ZEB repowers are of an equal standard and match those set for new vehicles, e.g., no diesel-fuelled heaters. The Zero Emission Vehicle Repower Accreditation Scheme, or ZEVRAS, will require repower suppliers to demonstrate that their solutions meet the Zero Emission Bus standard and achieve a ZEB certificate to access the BSOG ZEB uplift.

It is still early days, but should the new generation of ZEB repower suppliers be able to prove that their systems work in service and be able to install them quickly enough, there may be an attractive solution when an end of sale date for new non-zero-emission buses is introduced.