Zero emission vehicle repower accreditation scheme (ZEVRAS)

• Anyone can adopt the ZEVRAS standard in their procurement criteria, and repowering is a good way to achieve net zero targets, whether you want to claim for the bus service operator grant (BSOG) or not. The ZEFRAS standard can also be used as a guide for repowering other vehicle types like trucks or vans.  
• With the new zero emission bus (ZEB) incentive, operators of vehicles that hold a zero emission bus certificate may be eligible for a 22p per kilometer rate of BSOG for those vehicles. Eligible buses must meet the normal BSOG rules, demonstrate zero tailpipe emissions and have no internal combustion engine. 
• There is no age or Euro Emissions Standardlimit for a ZEVRAS product approval, however repower conversions are typically best suited for buses and coaches between five and1 0 years of age. We recommend a thorough inspection of the vehicle is conducted with support from your selected repower company, to ensure a vehicle is suitable for repowering.  
• There are no minimum or maximum zero emission range requirements for ZEVRAS, but vehicles must demonstrate they are as energy efficient as new zero emission bus and coaches.  

• The ZEVRAS standard has been developed for M2 and M3 class vehicles, covering buses and coaches. The scheme may be expanded in future to cover other vehicle types.  
• The ZEVRAS standard has been designed for zero emission technologies. This excludes the use of any combustion emissions, such as diesel heaters, to ensure repowered vehicles are completely emission-free whilst driving. The recent improvements in heat pump technology provides more than enough heating and cooling solutions for zero emission repowered vehicles.  
• ZEVRAS approved repowered vehicles will be placed on the ZEVRAS register of approved vehicles for entry into clean air zones (CAZ). This also includes Scottish low emission zones (LEZ) and London’s ultra low emission zone (ULEZ) areas. Operators will be required to contact the Driver and Vehicle Licensing Agency (DVLA) to change the engine (otherwise known as the powertrain) registration of their ZEVRAS approved products. 
• ZEVRAS is separate to the clean vehicle retrofit technology scheme (CVRAS) which focused on retrofitting exhaust aftertreatment systems to Euro 6 equivalent emission levels. ZEVRAS focuses on repowering combustion engine vehicles with new zero emission engines. 

There are two main technologies that enable a repower to qualify under the ZEVRAS standard. They are battery electric and hydrogen fuel cell electric systems.  

There are currently no companies offering hydrogen fuel cell repower systems for buses and coaches in the UK, but the ZEVRAS scheme is open to all zero emission technologies.  

Battery electric  

Battery electric is currently the most popular zero emission technology for buses and coaches. There are over 1,500 battery electric buses in the UK, and over 50 zero emission coaches.  

Battery electric vehicles (BEVs) operate using an electric motor powered by an onboard battery for propulsion rather than a diesel internal combustion engine. Electricity from the grid is used to charge the battery via a cable, overhead pantograph or inductive wireless chargers depending on charging strategy. 

Battery electric buses are designed with regenerative braking, enabling a proportion of the energy that would otherwise have been lost when the vehicle is decelerating to be recovered back to the batteries, typically 20-30% of total daily energy consumption. 

Find out more by downloading the zero emission bus guide from Zemo Partnership. 

Hydrogen fuel cell electric 

There are currently 68 hydrogen fuel cell electric buses in service in the UK. Hydrogen fuel cell solutions can provide a greater zero emission range depending on the number of hydrogen storage tanks on board.  

Hydrogen fuel cell electric vehicles (FCEVs) are electric buses but with energy stored in compressed hydrogen tanks rather than in batteries, making the daily range up to 500km. A fuel cell electric bus engine is made of a fuel cell stack and hydrogen storage tanks in combination with batteries or super-capacitors. FCEVs also have regenerative braking to recover energy in the same way as BEVs. 

Fuel cells convert the chemical energy stored in a fuel (in this case hydrogen) and oxygen (taken from the air) into electrical energy. To achieve sufficient electrical power to propel a vehicle, multiple cells must be compiled into a fuel cell ‘stack’. The leading fuel cell type for automotive vehicles is the polymer electrolyte membrane (PEM) fuel cell.