In the UK, the Low Carbon Vehicle Partnership (LowCVP) and the Energy Saving Trust (EST), together with industry stakeholders, have launched the Clean Vehicle Retrofit Accreditation Scheme (CVRAS). The UK’s DEFRA/DfT Joint Air Quality Unit (JAQU) is providing funding support.
CVRAS provides a single validation standard for any emission technology to meet the standards set out in the government’s Clean Air Zone Framework for England. The scheme will enable the existing fleet of urban vehicles (initially buses, but extending rapidly to a wide range of vehicles) to be fitted with proven emission control solutions. The scheme will also provide the backbone of future retrofit funding.
Manufacturers of abatement equipment need to get their equipment accredited before it can be added to the list of approved devices available to vehicle and Clean Air Zone (CAZ) scheme operators. This ensures that approved filters meet minimum technical standards and that vehicles fitting these approved emission reduction systems meet the national CAZ emissions standards.
For a number of local authorities, the UK plan for tackling roadside NO2 concentrations presents a significant challenge, requiring them to improve poor air quality as quickly as possible. While the latest Euro VI buses and advanced electrified options comfortably meet clean emission requirements, a significant majority of the older, existing bus fleet are seen as being a significant source of pollution and need a rapid and cost-effective solution.
Larger vehicles (buses, vans and HGVs) contribute more than half of UK national average roadside concentration of NO2 according to Defra’s AQ analysis. Next year the Government will publish a comprehensive Clean Air Strategy which will address other sources of air pollution.
The initial objectives of the scheme are to develop a set of test protocols (using the existing bus and commercial vehicle technology evaluation schemes as starting points) to accredit retrofit technologies which will deliver on road emission levels equivalent to. Euro VI/6, based on the best available data and representative operating cycles.
A minimum of four emissions tests, one recording engine-out emissions, and three measuring tailpipe emissions will be conducted using the vehicle(s) fitted with the low emission adaptation(s).Tests will be executed using the appropriate test cycle agreed in worst-case discussions and defined in the test procedure document. Data from the three tailpipe emissions tests will be averaged to yield a mean result.
If CO2 tailpipe emissions recorded for any test vary by more than plus or minus 1% from the mean of the three tests, the outlying test results will be rejected, and at least one further emissions test shall be carried out to establish a recalculated mean value.
The low emission adaptation(s) fitted must control both particulate and gaseous emissions in the vehicle exhaust by whatever means is selected by the adaptation supplier.
To ensure that performance tests are only carried out on engines/vehicles which have reached a stable phase after the completion of catalyst de-greening, vehicles fitted with low emission adaptations and intended for emissions testing must first complete a distance of 1,800 road miles (2,900 km). The supplier of the low emission adaptation(s) must provide evidence of completion of this pre-test de-greening distance accumulation to approved certification body prior to acceptance for emissions testing of the vehicle fitted with the low emission adaption.
The retrofit accreditation process will be technology-neutral and designed to allow all potential suppliers of eligible, credible emission reduction technology to apply for accreditation.
Technologies already potentially identified and in common use include: SCR (Selective Catalytic Reduction) fitted to exhaust systems; hybrid powertrain systems; and engine repowers with gas (LPG or CNG). New technologies will need to provide robust, independent relevant test data of the performance, prior to being considered for CVRAS accreditation.
The most effective retrofit technologies can cut polluting emissions by over 95%. But it is critical that these systems are properly calibrated and matched to the vehicle and its operation and that we have a common and robust approval system.
By making sure that we fit a range of the most appropriate technologies to the right vehicles, retrofitting can make a very significant, immediate impact on our air quality problems, supporting the complementary strategy to adopt new vehicles as quickly as economically viable. As you would expect from the LowCVP, our accreditation process will also ensure that there is no adverse impact on fuel efficiency or carbon emissions and aims to maximise the simultaneous benefits for both the environment and climate.—LowCVP’s Managing Director, Andy Eastlake