Batteries and fuel cells in dual for dominance

| Transport

Fuel cell vehicles don’t have the long charging periods associated with battery electric vehicles

Marcus Sampson, Business Line Manager for Transport at TÜV SÜD discusses batteries versus fuel cells for zero emission vehicles

The UK Government’s ten-point plan sets out its approach to accelerate net zero goals. Part of this will see the sale of new fossil fuel cars and vans banned after 2030. Vehicle manufacturers are therefore investing heavily in electric vehicle (EV) R&D to radically transform the way we drive, and battery development is at the heart of this process. However, while consumers are familiar with the traditional combustion engine, and therefore accept the well-known risks associated with fossil fuel powered cars, there is still an element of distrust relating to relatively new and unfamiliar EV technologies.

Comparatively lightweight and long lasting with good performance, Lithium-ion (Li-ion) batteries have proven invaluable in EV development, and improvements in design, materials, construction and manufacturing processes mean their safety has dramatically improved. However, these batteries still present many electrical hazards, such as electric shock, arc flash burn and explosion, which could include shrapnel and hot molten metal. Of course, because of the energy requirements to power EVs, high voltage / high-capacity battery packs are needed, therefore presenting an electric shock and energy hazard.

It is therefore essential that people working with and using high voltage systems are aware of the potential dangers and protective measures. As the global demand for innovation in EVs increases, so the need for qualified testing of lithium-ion batteries, and education about their use and care, will also continue to grow.

Global regulation

The World Forum for the Harmonization on Vehicles is responsible for harmonizing global technical requirements and protocols for the homologation of all types of vehicles and components. R100 is a United Nations Economic Commission for Europe (UNECE) regulation that addresses the safety requirements specific to the electric power train of road vehicles, as well as high voltage components and systems. The second revision of R100 introduced significant changes in the overall type approval process for RESS such as EV batteries.

International standards organisations set the mandatory regulations, such as the Economic Commission for Europe (ECE) in the EU, with BSI setting national standards in the UK. Three key safety standards apply to battery requirements – E/V’s: UN38.3 for the safe transport of batteries, with BS EN IEC 62660 -1/2/3 and ISO 12405 -1/2/3 covering performance, abuse & safety requirements

Safety testing

Ensuring the safety and reliability of Li-ion batteries requires thorough and accurate testing. EUCAR (European Council for Automotive R & D) has developed a scale to define the level of danger associated with handling batteries for automotive applications. This methodology and risk profile can help define the test programme, which includes life cycle, performance, environmental and durability testing, abuse testing, dynamic impact tests and transportation tests.

Safety tips for battery module and pack designs include the use of physical partitions and fire breaks to minimise fire propagation, employing good thermal management, using pressure vents / relief mechanisms, using sensors and a battery management system, using materials appropriate for foreseeable temperatures and using appropriate construction materials.

There’s no doubt that EV battery technology has developed at pace but nonetheless the requirements of industry to deliver this transition effectively and on time will require significant effort from all involved. There are still major challenges faced by battery manufacturers, and by the entire EV industry, but there are countless innovation opportunities.

Batteries and fuel cells

As battery electric vehicles (BEVs) are recharged from the electricity grid, overall carbon dioxide emissions will be reduced if the method of electricity generation emits less carbon dioxide per charged vehicle than those which use hydrocarbons as a fuel. Likewise, hydrogen fuel cell electric vehicles (FCEVs) have no tailpipe emissions, so provided that either green or blue hydrogen is used, overall carbon dioxide emissions will also be reduced.

One aspect that is commonly overlooked for FCEVs is the ability to effectively trade hydrogen. To achieve net zero, a substantial portion of vehicles will need to be hydrogen powered, but consumers will not buy such vehicles until they can easily refuel them. That will require accurate measurement of the fuel delivered, so they pay for what they get, and a widely available refuelling infrastructure, so they can get to their destination reliably.

It is therefore no surprise that globally there are currently significantly more BEVs than FCEVs, as the capital costs associated with building a hydrogen refuelling station (HRS) mean that they are less common than the relatively low-cost BEV charging points. In the UK, only a handful of hydrogen refuelling stations exist, compared to nearly 100 in Germany – which has set out clear milestones to increase this significantly further.

However, FCEVs do have several advantages, such as a larger range of 400 km and above, compared to a range of around 250 km for BEVs. This is because, when compared with fuel cells and petrol/diesel engines, battery packs store much less energy by weight. On range alone, hydrogen seems to have the upper hand.

In addition, FCEVs can be refuelled in a few minutes, whereas BEVs can take several hours to recharge batteries. For example, while Tesla supercharging stations have a 20-minute charging time this only delivers an 80% charge to protect the battery from high temperatures. After that the rate of charge decreases significantly. For home charging, the charging times are usually many hours, which is only easy for car owners who have their own driveway.

As FCEVS can travel further distances than BEVs and have shorter refuelling times, they are more suitable for the long haul and heavy loads required by HGVs. However, clearly BEVs still have a significant role to play in our quest for net zero as they are more suited to domestic situations that allow for a longer recharging downtime, such as overnight before morning commutes.

We need all the tools in the box

To realistically meet 2030 vehicle targets and hit net zero ambitions, the answer should be to combine the use of both battery and hydrogen fuel cell technologies. Harnessing the benefits of both technologies will deliver the high-performance systems associated with the traditional combustion engine while reducing carbon emissions.

A vehicle will always need a battery system to support its many functions, but fuel cells can enhance their performance. For example, by solving the issues of distance and charging/refuelling times currently associated with pure BEVs. This is because the fuel cell can be used to charge the battery, as petrol hybrid vehicles do today.

However, batteries are more capable of effectively managing the various simultaneous energy load demands of a vehicle. The battery management system monitors vehicle safety and performance, with state-of-health functions determining battery degradation and end of usable life. 5G will also be a driver of smart battery maintenance, using real-time data to optimise battery charging and discharging, and support predictive maintenance and failures, as well as remote troubleshooting.

It is therefore not a question of either/or, as both battery and fuel cell technologies fill the operational and performance gaps of each other. The future of zero emission vehicles will be powered by both.

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