• • • ELECTRIC VEHICLES • • •


Cleaning up automotive emissions


Simone Bruckner, managing director of automotive resistor manufacturer, Cressall Resistors, investigates the problem and solutions to non-exhaust emissions


national total. However, carbon isn’t the only thing nation’s vehicle fleet emits — non-exhaust emissions also have a detrimental impact on the health of the population and the planet. The electrification of the automotive market is in


R


full swing, and with the ban on new fossil-fuelled cars set for 2030, there is light at the end of the tunnel when it comes to reducing vehicle emissions. Electric vehicles (EVs) are often referred to as ‘zero emission’, but this is not entirely true since non-exhaust emissions are produced by all vehicles, irrespective of their fuel source. In fact, the EV rollout is not expected to have any impact on non-exhaust emissions.


It’s not just CO2 Non-exhaust emissions are particles released from brake, tyre and road surface wear, resulting in the production of particulate matter — all of the chemical compounds and materials in the air that are not gas. Particulate matter is classified depending on the


diameter of the particles. PM10 and PM2.5 refer to particles less than ten micrometres and 2.5 micrometres in diameter. According to the Office for National Statistics, the amount of particulate matter in the atmosphere has been steadily decreasing for decades, falling by 75 and 80% for PM10 and PM2.5 respectively between 1970 and 2019. However, road transport remains a significant


source of particulate matter, contributing twelve per cent. Stricter emission targets have significantly reduced carbon emissions from vehicle exhausts, but the positive impact of these efforts has been


oad transportation is widely recognised as a large contributor to carbon emissions, taking responsibility for 30% of the UK’s


offset by an increase in particulate matter from non-exhaust emissions due to increased traffic. Therefore, it’s essential to take further steps to reduce the impact of these other automotive emissions.


The problem with particulate


matter Particulate matter from non-exhaust emissions originates from surface wear, which leads to abrasion and the release of small particles that become airborne. Friction between brake pads and the rotating disc and between the tyre and the road both lead to abrasion, component wear and the release of particles from the surfaces into the atmosphere. The minute size of these particles means that


some of the toxins that they include are small enough to enter the human body through the bloodstream, where they can cause serious damage to the heart, brain and respiratory systems. According to the World Health Organisation (WHO), nine out of ten people worldwide breathe polluted air, and seven million people die a year because of the health effects of air pollution. In addition to the detrimental effects on human


health, particulate matter can seriously damage the environment. Once airborne, it can be carried large distances and settle on the ground or in water where toxins can lead to catastrophic ecosystem disruption, altering the nutrients of water and soil and contributing to increased acidity and agricultural destruction. With so many issues, it comes as a surprise but


there is currently no policy in the UK regulating non-exhaust emissions. The current legal limit for PM2.5 is 25 micrograms per cubic metre air (µg/m3), 15µg/m3 higher than the WHO’s


Sustainable by design When considering how to reduce particulate matter emission it’s important for transport manufacturers to consider the factors that determine the production of non-exhaust emissions. Reducing brake wear is the key area for transport manufacturers can concentrate their efforts to reduce emissions thanks to regenerative braking technology. In regenerative braking, upon deceleration, the


vehicle’s kinetic energy is recovered and stored in the vehicle’s battery. This is particularly useful for EVs as the battery powers the vehicle, and so recharging the battery while driving increases range and improves energy consumption. However, it’s important that these systems have


a safety mechanism in place for when the vehicle’s battery is in a high state of charge. If the battery is full or there is a failure it will be unable to store additional energy from the braking system. Therefore, the energy must have an alternative pathway to keep the vehicle’s power system functional. A dynamic braking resistor is an essential


component of a regenerative braking system, safeguarding the power system by removing excess energy and dissipating it as heat. This energy can be used to warm the vehicle’s cabin or preheat and keep the battery to maintain the correct working temperature and achieve maximum efficiency. Cressall’s EV2 resistor is specifically designed to meet the challenges of automotive manufacturing and can be adapted to suit any transport application. Most of the time, the electric brakes will be


sufficient to slow the vehicle, meaning that the mechanical system will only be used at very low speeds when the motor cannot generate sufficient braking force to stop the vehicle quickly. Less reliance on the brakes leads to minimised brake wear, resulting in a reduction in particulate matter and non-exhaust emissions. The 2030 ban on petrol and diesel vehicles


will ignite the elimination of exhaust emissions, but the idea that this will result in a zero-emission fleet is incorrect. Although some of the contributing factors to non-exhaust emissions may be out of our control, it’s important to minimise those that we can, like vehicle mass and brake wear, to reduce risks for the population and the planet.


26 ELECTRICAL ENGINEERING • NOVEMBER 2022 electricalengineeringmagazine.co.uk


recommendation. However, in June 2021, the UK government announced plans to adopt new targets for particulate matter production by October 2022. To support this, it’s essential for vehicle manufacturers to consider how they can reduce non-exhaust emission through design.


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