Ensuring safe BEV operations

LOAD BANKS ARE CRUCIAL AT EVERY STAGE OF THE BEV CYCLE

As the battery electric vehicle (BEV) market continues to flourish, and impending fossil fuel bans creep closer and closer, it’s crucial for manufacturers at every stage of the chain consider how best to ensure the correct functioning of their components. Whether it’s at the beginning, end or extreme of the BEV scene, load banks play a role in securing safe operations.

There’s no denying that the future of the automotive market is electric. According to the International Energy Agency’s Global EV Outlook 2022, EV sales doubled between 2020 and 2021, reaching 6.6 million globally. Yet with transition deadlines looming, matching demand with supply is becoming more urgent. This brings an absolute need for reliable, operational vehicles and their enabling technology.

As an essential piece of testing kit, load banks play a vital role in ensuring BEVs and their infrastructure are safe and consistent by validating the proper operational performance of components across the sector — from EV charging point testing to end-of-life battery discharge, and even Formula E pitstops.

FROM THE BEGINNING

EV charging points are a huge new focus for the automotive industry. With a target of delivering 300,000 new charging points in the UK, 500,000 in the US and 6.8 million in the EU all by 2030, production rates are rapidly on the uptake to reach these goals.

Before deploying these charging points, they must undergo quality control to ensure their operational performance. This is where load banks come into play. By stimulating an electrical load, load banks test the charging points postproduction, ensuring they are fit for purpose and to prevent any unexpected failures once set up at their designated sites.

TO END OF LIFE

As well as ensuring the operations of the EV infrastructure from the beginning, load banks also ensure the safe end-of-life disposal of lithium-ion batteries. In general, BEVs are typically expected to last between 10 and 20 years. So, although end-of-life practices aren’t a huge concern right now, they will be by the end of the decade thanks to the ongoing sales boom.

Once an EV reaches the end of its operational life, its batteries need to be safely discharged. EV batteries are typically recycled to recover their scarce heavy metal components — lithium, cobalt, manganese and nickel. But before these processes can take place, there’s an additional step that must be taken.

Even when an EV battery appears to have no charge left, it still naturally generates a small amount of charge, which can be enough to be dangerous if not completely released. By plugging the battery into a load bank, it can automatically determine the battery’s current capacity and continuously discharge it, dissipating the excess electronic load. Removing any remnant charge makes the battery safe for dismantling and metal component extraction, for reuse in the next generation of EV batteries.

AT THE EXTREME

While the electrification of commercial vehicles dominates the automotive market, there are additional applications sitting at the extreme of the electric revolution. That includes the rise of Formula E — the all-electric FIA World Championship. In the electrical future of motorsport, there remains additional considerations regarding the safety of mechanics during pitstops.

While pitstops are not mandatory at the moment in Formula E, thanks to the extended battery life and the use of all-weather tyres, they can still be required in the event of a puncture or other damages. In Formula E, because there are so many electrical components running at such a high voltage, there’s a great risk of electrocution if a fault results in the car’s body becoming live.

To protect mechanics and drivers, load banks are used to consume the car’s electrical circuits power and dissipate, temporarily discharging it and ensuring the system is safe for close contact.

As time goes on and EVs become more widespread, both on the road and track, load bank testing for BEVs will become commonplace. While the EV rollout may be in full swing, getting the right technology in place to ensure safe, correct operations at the beginning, end and extreme of the market is crucial to success.

CRE467

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

Marine resistor design

DIVING INTO MARINE RESISTOR DESIGN

EV2 modular resistor for electric vehicles

DESIGN CONSIDERATIONS FOR OFFSHORE ELECTRICAL COMPONENTS

Covering over 70 per cent of the Earth’s surface, the oceans are a vital element of our planet’s ecosystem. However, for the millions of vessels that cross them, the aquatic environment can present a problem. Vessels are increasingly using electrical systems to power across oceans, but a component’s design must account for these extreme conditions.

Whether for main propulsion propellors, crane or lifting systems, or cable laying, electrical drives can be found at the heart of many marine operations, offering increased control, reliability and mechanical simplicity. Dynamic braking resistors (DBRs) are an essential part of an electric drive system that remove excess energy from the system when braking to either dissipate as heat if system is not receptive to regeneration or if system is receptive, but energy level goes beyond the system limits, so needs to be removed.

When designing electrical components for offshore applications, material selection is key from the start of the process to guarantee that equipment will perform under harsh conditions, including saline atmosphere, high wind loadings and corrosive sea water.

Engineers tasked with designing resistors for marine applications must consider material choice, structural stability and cooling method.

CORROSION-RESISTANT MATERIALS

Sea water and the saline atmosphere is corrosive, which could leave equipment inoperable. Due to this, stainless steel, combined with special paint systems, is typically used for the enclosure metalwork for resistor elements. With materials containing at least 10.5 per cent chromium, stainless steel reacts with oxygen in the air to produce a protective layer on its surface to prevent corrosion if not painted.

There are many grades of stainless steel that can offer high corrosion resistance, which can be further enhanced by the addition of extra elements. For below-deck applications, 316 and 304 stainless steel contain nickel to broaden the protective layer created by the chromium, and can be used in unpainted condition.

However, for above-deck components, 316 stainless steel has a higher nickel quantity and added molybdenum, so the resistor unit’s metalwork receives optimum protection against the marine atmosphere, but in some conditions, painting will also be required. Cressall’s resistor enclosures for the EV2 resistor terminal cover boast at least an IP56 ingress protection rating, certifying that sea water cannot enter the unit to cause harm.

In addition to the exterior, it is important that the resistor’s element can withstand the harsh conditions. For these applications, Alloy 825 sheathed mineral-insulated elements are less vulnerable to atmospheric corrosion. As the element in encased within the mineral insulated sheathing, the sheath is at earth potential, so if water or high humidity is present this will prevent accidental contact with the live element, making them a much safer choice for marine applications.

STRUCTURAL STABILITY

Weather at sea is unpredictable, so vessels must be able to withstand the large variance in wind and harsh sea conditions found worldwide. Many offshore structures such as wind turbines are located in areas with high winds, so if the system requires resistors to help provide stability to their electrical components these considerations must be considered within a resistor’s design.

Considering the impact of a vessel’s rotational motions — its side-to-side motion, or pitch, and its front-to-back motion, or roll, is crucial. Design engineers need to ensure that there is enough mechanical support in the structure to stabilise the resistors for safe operation when it is subjected to these forces.

Cressall can conduct finite element analysis (FEA) to help ensure structural stability. FEA allows design engineers to predict a product’s performance in the real world, then see the impact of forces and make changes accordingly. This ensures the resistor performs well in the potentially extreme weather conditions.

It’s also important to consider the size constraints of marine applications. In contrast to onshore units, offshore electrical components must fit into a compact area, so the size of the unit’s support structures must be minimised without compromising durability.

COOLING METHOD

An essential part of a resistor is its cooling system. Since the resistor dissipates excess energy as heat, the cooling system is responsible for cooling the resistor element to ensure continued operation. Depending on the layout and resources of the system, resistors can be naturally or forced air or water-cooled.

Air-cooled resistors come in two types — forced and naturally cooled systems. Forced cooling systems use a fan to dissipate heat in a compact space. These units are suitable for deck mounting and can be secured using anti-vibration mounts. Natural cooling is the most common in marine applications, offering a higher power rating and can be mounted in machinery spaces, protected environments or on deck. For machinery spaces or protected areas, consideration should be given to how the hot air released from the resistors should be evacuated to ensure other equipment mounted locally does not overheat.

Alternatively, the cooling system can use the vessel’s chilled water system, which circulates cool water for air conditioning and equipment cooling. If the chilled system uses sea water, titanium-sheathed elements with super duplex steel metalwork can be incorporated, for continuous use in acidic, tropical sea water and downgraded to 316 stainless steel for freshwater systems.

The ocean is a valuable asset for energy, transport and trade. Ongoing development of electric drives for marine applications can be challenging, but taking these conditions and energy savings into account makes them a viable and advantageous option for powering vessel and for use in offshore structures.

CR470

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