• • • ELECTRIC VEHICLES • • • The problems with
lithium power Most BEVs are powered by lithium-ion batteries. These have decreased substantially in price since they first started appearing in electric vehicles, making electric lorry fleets a lot more financially viable. However, this downward pricing trend is not
expected to last. High global demand of lithium is predicted to result in chronic shortages by 2030. While there is still enough lithium in the ground, lacking infrastructure means that not enough of it can be mined to meet modern demands for much longer. Another issue with BEVs is their heavy reliance
on the power grid, as more than half of the energy on the grid is provided by non-renewable sources. Grid reliance can also be tricky in the cases of power cuts and blackouts. Overnight power disruption may result in a half-empty battery the next day, having a knock-on effect to scheduled deliveries and supply chains.
Preserving battery life In response to these issues, manufacturers should be looking for ways to ensure that their HGVs can get the maximum value out of their fuel. Preserving battery life can help to ease the pressure on the lithium supply, as well as lower overall fuel demand. One of the ways that battery life preservation
can be achieved is through regenerative braking. In an electric vehicle, the electric motor runs in two directions. The forward direction drives the movement of the wheels and the vehicle. Reversing the motor direction takes the excess
energy away from the braking system and puts it back into the battery. Using regenerative braking, the kinetic energy from braking that would otherwise be wasted can be saved and reused elsewhere.
Batteries only have a limited capacity though,
and a full battery has nowhere for the excess electricity to go. This can lead to component damage as well as overheating. To dissipate the excess electricity safely and prevent this from happening, a dynamic braking resistor, or DBR, can be used. DBRs are also useful in ensuring that
emergency braking can be done safely, which is essential in heavier vehicles. FCEVs struggle with fast acceleration and deceleration, as fuel cell output is not consistent due to the method of generating electricity. The solution is to install cells that have a higher
output than what is needed, meaning that there is always sufficient energy available, and using the DBR to safely remove the excess.
Choosing a lightweight DBR like Cressall’s EV2
helps to reduce the overall weight of a HGV, maximising its payloads. The EV2 also has a modular design, allowing multiple modules to be combined to give up to 125 kW in one single unit, which could be then put in parallel or series with others for higher power for safe emergency braking. At only a tenth of the size of conventional convection cooled DBRs, the liquid cooled EV2 provides a compact solution to safer braking. It’s clear that there’s still a long way to go to
providing cost-effective and sustainable fuel for heavy vehicles. But boosting battery life can go a long way in meeting overall demand. By implementing technologies like regenerative braking, even the largest of road vehicles can benefit from cleaner, greener fuel technologies.
electricalengineeringmagazine.co.uk
ELECTRICAL ENGINEERING • DECEMBER 2022/JANUARY 2023 35
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