Cleaning up automotive emissions

CLEANING UP AUTOMOTIVE EMISSIONS

IT’S TIME TO START ADDRESSING NON-EXHAUST EMMISSIONS

 Road transportation is widely recognised as a large contributor to carbon emissions, responsible for 24 per cent of the global total. However, carbon isn’t the only thing the world’s vehicle fleet emits —non-exhaust emissions also have a detrimental impact on the health of the population and the planet.

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 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.

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 PROBLEM WITH PARTICULATE MATTER

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 that several nations lack a policy regulating non-exhaust emissions. The current legal limit for PM2.5 is 25 micrograms per cubic metre air (µg/m3) in the UK, 20 µg/m3 in the EU and 25 µg/m3 in Australia, all of which exceed the WHO’s recommended limit of 15µg/m3. Therefore, it’s essential for vehicle manufacturers to consider how they can reduce non-exhaust emission through design.

SUSTAINABLE BY DESIGN

When considering how to reduce particulate matter emissions, 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, increasing EV range and improving 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 thebraking 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 EV by removing excess energy and dissipating it as heat. Most of the time, 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.

CR465

HYDROGEN CATALYST

THE HYDROGEN CATALYST TO THE EV REVOLUTION

 IS HYDROGEN KEY TO THE NET ZERO EV ROLLOUT? 

In November 2021, UK Prime Minister Boris Johnson announced the dawn of the electric vehicle (EV) revolution, fuelled by new regulations and investment pledges across all stages of the EV supply chain. From charging stations to electricity generation, new projects will begin across the United Kingdom in 2022. But there’s one key ingredient that will transform the sector’s sustainability credentials — hydrogen.

With bans on the production of new diesel and petrol-powered vehicles looming, encouraging widespread consumer uptake of more sustainable vehicle choices is becoming an urgent matter. Uptake seems to be increasing — according to The Society of Motor Manufacturers and Traders (SMMT) demand for battery electric vehicles (BEVs) more than doubled between November 2020 and November 2021. But if transport is to decarbonise before its 2050 deadline, there’s more to do to make BEVs carbon neutral.

BEVS’ SUSTAINABILITY SHORTFALLS

Fully decarbonising BEVs is tricky. Using energy from the National Grid means that the sources used for electricity generation directly affect BEVs’ environmental impact. The grid is becoming more renewable and is set to be net zero by 2050. But there is an added challenge. According to The Committee on Climate Change, electricity demand is set to double from today’s 300-terawatt-hour (TWh) requirement to 610 TWh by 2050 thanks to BEV uptake.

So, to complete the dual task of increasing supply and decarbonising electricity generation, the Government is investing in dispatchable low-carbon sources to support variable weather-dependent renewables in powering the grid when production falls short of demand. In the meantime, fossil-fuelled electricity generation is negatively impacting BEVs’ sustainability.

BEVs also have some additional environmental concerns regarding their reliance on lithium-ion batteries. Rare earth metals including cobalt, nickel and manganese are all major components of lithium-ion batteries. Mining these materials can result in huge environmental destruction, disrupting entire ecosystems, while the heavy machinery used contributes even more emissions. So, is there a more sustainable option?

HYDROGEN : THE FUEL OF THE FUTURE

Hydrogen is a promising resource that is key to delivering transport’s decarbonised future. Industrial production of hydrogen is typically delivered through electrolysis — using an electrical current to split water into hydrogen and oxygen. If a renewable source is used to produce electricity, then this creates an entirely carbon-neutral hydrogen fuel, known as green hydrogen.

The Government has set a target to produce five gigawatts (GW) of green hydrogen by 2030 and has already announced investments into projects like Whitelee Windfarm near Glasgow, which will use wind power to generate electricity for hydrogen production.

Hydrogen produced in this way can then be used as a fuel source for an alternative to BEVs: fuel cell electric vehicles (FCEVs). FCEVs are powered by proton exchange membrane fuel cells. FCEVs turn hydrogen into electricity by combining the hydrogen fuel with air and pumping it into the fuel cell. Once inside the fuel cell, this triggers a chemical reaction, resulting in the extraction of electrons from the hydrogen. These electrons then create electricity, which is stored in a small battery used to power the vehicle.

FCEVs fuelled with green hydrogen are completely carbon-free, thanks to the renewable origins of these fuel cells. The only end products of the fuel cell reaction are electricity, water and heat, and the sole exhaust emissions are water vapour and air. This makes them a more-aligned choice with net zero goals, enabling a widespread, carbon-neutral EV rollout.

MAKING HYDROGEN VIABLE

Although the benefits of FCEVs are clear, the technology behind them still needs refining. Fuel cells are unable to work under heavy loads for a long time, which presents issues when rapidly accelerating or decelerating.

Studies into fuel cell function have shown that, when an FCEV begins accelerating, the fuel cell’s power output increases gradually to a point, but then it begins to oscillate and drop despite velocity remaining consistent. This unreliable power output presents a challenge for automakers.

The solution is to install a fuel cell for a higher power requirement than necessary. For example, if a FCEV needs 100 kilowatts (kW) of power, installing a 120-kW fuel cell would ensure there is always 100 kW of power available, even if the fuel cell’s power output drops. Opting for this solution requires a resistor to remove the excess energy when not required, to perform a “load bank” function.

Cressall’s water-cooled EV2 is designed specifically for heavy-duty applications including hydrogen-powered FCEVs. It absorbs excess energy from the system and dissipates it as heat, which can be used to warm the vehicle’s passenger cabin. This protects the electrical system, allowing FCEVs to be very reactive to high-power demands, and accelerate and decelerate rapidly without storing excess energy in a battery.

The EV rollout is well underway, with pressing deadlines for the retirement of fossil fuelled vehicles edging closer and closer. Although BEVs are the main player in the decarbonisation of transport, it’s important to not rule out the distinct benefits that FCEVs bring to the market. But combining the two could be the key to unlocking the EV revolution

CR469

ELECTRIC MINES

POWERING THE SHIFT TO ELECTRIC MINES

According to a 2020 McKinsey report, the global mining industry is responsible for between four and seven per cent of total greenhouse gas emissions, so any technology that contributes to the sector’s decarbonisation is valuable. For decades, diesel-powered machinery and vehicles have dominated mining. Its long success is down to the fact diesel engines can handle the extremely harsh conditions of underground mines, enabling access to once unreachable depths.

THE PROBLEM WITH DIESEL

Diesel’s power doesn’t come without problems. From an environmental perspective, the use of diesel engines doesn’t support mining’s decarbonisation agenda.

However, there is another reason why moving away from diesel is a good idea — its negative impact on worker safety. According to the International Labour Organisation, despite only employing one per cent of the global labour force, mining is accountable for eight per cent of fatal workplace accidents.

Two major sources of hazard in underground mining are ventilation and noise, which are both worsened by the use of diesel-powered machinery. The emissions from diesel mining equipment are a large contributor to the toxic gases found in underground mines, which require vast, comprehensive ventilation systems to clear the air for workers to breathe. In addition, the noise produced by large diesel engines adds to the noise pollution, which is already significant, and can lead to noise-induced hearing loss.

THE MOVE TO ELECTRIC

EVs eliminate the noise and emission problems associated with diesel power systems. However, currently only 0.5 per cent of mining vehicles are fully electric, and many mines are reluctant to make a complete shift due to performance concerns.

The same worries holding automotive consumers back from changing to an electric car hold true for mine operators, who are reluctant to move away from diesel’s reliability due to concerns around battery capacities. 

With operations taking place hundreds, or even thousands, of metres below the ground, underground mining vehicles need to consistently perform well. Equipment failure in underground mines can not only result in huge repair costs and significantly impact production, but it can also risk health and safety, so it is critical that electric mining vehicles can meet the demands of this application.

THE REGENERATION GENERATION

Underground mining equipment encounters some of the harshest conditions out there — unseen holes, tight tunnels and uneven terrain can all place stress on automated equipment. Therefore, vehicles must be designed with these conditions in mind.

An essential component of any EV is its dynamic braking resistor (DBR). Heavy duty applications like mining require heavy duty components to withstand the tough operating conditions they face.

When a mining vehicle brakes, using the principles of regenerative braking, the first option is to store the excess energy produced in the vehicle’s battery for reuse, improving the energy efficiency of the vehicle and keeping the system operational for improved safety.

However, when the battery is close to its full charge, this is not possible. A dynamic braking resistor is the simplest, most reliable and cost-effective solution to this problem as it dissipates the excess energy as heat, allowing the EV to stop when required. This is particularly useful in mining applications, where operational efficiency and reliability are crucial.

Cressall’s EV2 water-cooled DBR has a unique design, meaning it takes up just ten per cent of the volume and 15 per cent of the weight of a conventional air-cooled DBR. Units can be combined in up to five-module assemblies to meet high-power requirements.

Mining techniques have evolved many times throughout its rich history. With increased pressure to decarbonise, mining EVs will play an essential role in bringing the industry into the 21st century, making operations efficient, reliable and safe.

CR469

Powering autonomy 

POWERING AUTONOMONY

ENERGY-EFFICIENT BRAKING CRUCIAL TO SUCCESS OF AUTONOMOUS VEHICLES

When a self-driving Uber crash led to a fatality in 2018, to many, it seemed that the autonomous vehicle revolution was over before it had chance to gather speed. If autonomous vehicles are to make it onto our driveways, braking systems will be crucial to minimising accidents.

One year after the Uber crash, the National Transportation Safety Board (NTSB), an independent US government investigative agency, concluded that a major factor in the collision was a misjudgement by the vehicle’s safety operator — or, the human that sits in the vehicle and monitors the autonomous driving system.

While it seems that human error will never go away, manufacturers have not given up on the concept that the right technologies can help autonomous vehicles steer away from disaster. Automotive giants, like Jaguar Land Rover (JLR), continue to invest in autonomous technology. JLR’s Project Vector concept aims to have an “autonomy-ready” and “multi-use electric vehicle” on the road by 2021. 

While it’s clear that the future will be self-driving, how will manufacturers avoid the accidents of the past — and what role can advanced braking systems play?

FOLLOW THE ROUTE

Operating from March 2018 to June 2019, the Route 12 driverless bus concept successfully provided Schaffhausen, Switzerland with a driverless bus system over a year. Big cities can learn a lot from the small Swiss town and, last year in Germany, Berlin’s public transport company, Berliner Verkehrsbetriebe (BVG), also tested out its own autonomous buses.

Autonomous transport offers many benefits to towns and cities alike, not least in terms of safety. The UK’s Department for Transport reports that 27,820 people were killed or seriously injured in reported road traffic accidents in the year ending June 2019. Leading causes for these accidents included speeding, lack of focus or driving under the influence — all of which are results of human error. 

Programmable driving systems should eliminate these unsafe human habits, of course. In addition, driverless vehicles can also reduce traffic congestion by following fixed routes that are simpler to handle than the various and complicated routes along which a taxi or car usually travels. 

REGENERATIVE BRAKING

Choosing the most effective system for an autonomous vehicle goes beyond merely bringing the vehicle to a stop. As most autonomous vehicles in the future are expected to be electric vehicles (EVs), braking systems will also play a crucial role in optimising energy consumption.

This applies to EVs used for public transport, where multiple stops and starts along a single route are an energy drain. When these stops occur, and because the electric motor behaves like a generator under these conditions, the EV releases energy that is fed back into the drive system. This energy needs somewhere to go, so heads towards the EV’s battery as part of a process is known as regenerative braking. 

If the battery is full, and the EV has no other means to dissipate the excess energy, then the speed of the vehicle might be limited in order that the mechanical brakes can safely bring the vehicle to a stop without the possibility of causing brake fade or failure. 

To remedy this, a braking resistor, such as Cressall’s EV2, can dissipate excess energy when the battery does not accept the charge. This type of braking is known as dynamic braking. Wherever possible, braking should be regenerative rather than mechanical. This creates the possibility of storing and re-using braking energy, rather than just dissipating it as waste heat. 

Furthermore, many public service and heavy goods vehicles are fitted with auxiliary or endurance braking systems that work in tandem with the service brakes. The EV2 is an ideal substitute to these mechanical, hydraulic or magnetic systems. 

Heating also plays an important role in making use of this regenerated energy. The EV2 is a liquid cooled resistor. Specifically, it is cooled by pumping the cold liquid that comes into one end of the system, which then absorbs the heat generated by the resistor. This heated liquid can be pumped through a radiator, then used to provide heat to the cabin of the vehicle for a more comfortable passenger experience. 

This method of heating reduces the amount of energy required from the battery, and uses heat that would otherwise have been wasted.  

While the wide-spread adoption of autonomous transport has yet to become a reality, it’s not difficult to imagine the day when cars will brake on their own, as commanded by autopilot. After all, electric steering systems already perform a similar function. Braking technology can’t change the mistakes of the past, but it can be a huge driver in delivering energy-efficient autonomous transport. 

To find out more about Cressall’s EV2 for electric vehicles, click here

CRE413