Fuel cell versus battery trucks

FUEL CELL VERSUS BATTERY TRUCKS

HOW CAN AUTOMOTIVE MANUFACTURERS CREATE A ZERO EMISSION FUTURE?

By 2040, all new heavy goods vehicles (HGVs) sold in the UK must be zero-emission. Advances in green energy technology mean this is possible, but automotive manufacturers are still in disagreement about what type of power source is best. In this article, Simone Bruckner, managing director of resistor manufacturer Cressall, explains the pros and cons of fuel cells and battery power, and what these mean for electrifying HGVs.

There are two main types of electric vehicle, categorised by their power source. Battery Electric Vehicles (BEVs) rely on a lithium-ion battery for power. Fuel Cell Electric Vehicles (FCEVs) on the other hand use a fuel cell, which combines hydrogen gas with oxygen to generate electricity.

HYDROGEN POWER

Hydrogen is the most abundant element in existence, so future supply is not an issue. Hydrogen power also has a much higher energy density than batteries, at around 35,000 watts per kilogram of hydrogen, while lithium-ion batteries only have around 200 watts per kilogram.

This increased energy density allows FCEVs to travel distances comparable to petrol or diesel vehicles, and up to 100 miles further than BEVs. For HGVs in particular, it also means that much heavier payloads are possible, with the ability to carry an extra two tonnes or more depending on the vehicle.

The main problem with hydrogen fuel remains with its production. Similar to the way we often refer to more environmentally friendly processes as “green”, hydrogen is colour-coded based on its method of production. Most of the hydrogen produced currently is defined as “grey”.

Grey hydrogen is generated using methane from natural gas, producing about ten times more carbon dioxide than hydrogen. Recapturing the carbon dioxide produced is possible, but it’s still not a perfect solution, only being able to capture up to 80 per cent of the generated carbon.

The ideal type of hydrogen is green, produced by separating hydrogen and oxygen molecules in water using electricity. Provided that the source of this electricity is renewable, this is the most environmentally friendly form of hydrogen. At present, the cost of production is the main barrier for this method, though it is expected to fall to a level that’s more competitive with grey hydrogen by 2035.

REFUELLING AND RECHARGING

Refuelling remains a hot topic for FCEVs. In terms of refuelling time, FCEVs have a huge advantage over BEVs, taking around three to five minutes to refuel. This means that lorries can get straight back onto the road with minimal downtime, without hampering delivery expectations.

In contrast, BEVs can take anywhere between 30 minutes to ten hours to recharge, depending on the voltage of the charger and the battery size. Considering the battery size required to power a HGV compared to a passenger car, it’s likely that most HGV charging times will sit on the higher end of the spectrum on a standard charger.

Rapid chargers operating at a higher voltage can be installed at HGV depots instead, giving access to much faster recharging times, though they will still not be as quick as FCEVS to refuel. It’s important to note, however, that UK legislation requires drivers to take regular breaks regardless.

By law, drivers should take a 45-minute break for every four and a half hours driving, and drive for a maximum of ten hours per day. Factoring in these numbers, the slower refuelling time of a BEV may not be as much of an issue as once thought, provided it can refuel sufficiently to reach the next point in its journey.

The abundance of charging points means that a BEV is never too far away from a top up. In contrast, there are only around 15 stations in the UK currently providing hydrogen fuel. Choosing FCEVs right now, therefore, means that careful route planning is required to ensure the lorry can safely reach a station.

Encouragingly, investments are being made in this area. Bosch has committed to set up 4,000 hydrogen fuelling points worldwide by 2030, and as the cut-off deadline looms for new petrol and diesel vehicles, it’s likely that similar schemes will follow.
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. And 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.

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Cressall Resistors is Cyber Essentials certified

cyber essentials logo

CRESSALL RESISTORS IS CYBER ESSENTIALS CERTIFIED

Cyber Essentials is an internationally recognised, UK Government-backed certification scheme launched in 2014 as part of the Government’s National Cyber Security Strategy.

Developed by the National Cyber Security Centre – a part of GCHQ – and delivered by IASME, the certification scheme supports organisations of all sizes to guard against online threats and demonstrate a commitment to cyber security.

Cressall first achieved certification in 2021 and has just successfully renewed following rigorous re-assessment. As the nature of threats develop and working practices evolve the certification requirements are reviewed and changed frequently, hence the requirement for annual renewal.

Cressall takes our commitment to protecting data very seriously and this certification provides evidence of that commitment to our Customers, Suppliers and other stakeholders.

Could hydrogen decarbonise transport?

THE HYDROGEN FUTURE OF EUROPE’S AUTOMOTIVE MARKET

April 2021 saw the latest collaboration in support of fuel cell electric vehicle (FCEV) uptake, with automotive manufacturer Nikola announcing plans to create a hydrogen pipeline and refuelling system across Europe. What technology is required to make hydrogen a viable option both in terms of sustainability and automotive efficiency?

Europe has one of the world’s most developed hydrogen markets and is home to over half of all projects, according to The Hydrogen Council and McKinsey’s Hydrogen Insights Reports 2021. Both the UK and the EU have plans to develop their hydrogen offering and have committed to reach a production capacity of five gigawatts (GW) and 40 GW respectively by 2030.

Despite the maturity of the sector, Europe’s hydrogen still needs considerable development in order to reach net zero targets and to become a viable fuel source for automotive applications. Making usable, renewable hydrogen is no easy feat — so where’s the best starting point?

CLEAN IS GREEN

First, we must consider how we make hydrogen green. Hydrogen can be produced in many ways, each corresponding to a different colour. Most hydrogen produced in Europe is currently grey — it is produced by mixing natural gas and steam to create hydrogen and carbon dioxide in a process known as steam methane reformation.

The problem with this production method is that it relies on a fossil fuel to produce hydrogen, which conflicts with hydrogen’s alleged sustainability superiority over petrol and diesel-powered vehicles.

Ideally, we need to make green hydrogen, which uses renewable electricity to separate the hydrogen and oxygen atoms that make up water in a process called electrolysis. This results in zero carbon emissions.

Geographically, Europe is in an advantageous position thanks to an abundance of renewable energy sources in the surrounding area. The EU’s Hydrogen Strategy Report has already identified North Africa as a priority region for increasing hydrogen availability across Europe, thanks to a plentiful supply of sunlight and subsequent renewable energy.

IMPROVING FUEL EFFICIENCY

Next on the agenda is making hydrogen-powered vehicles commercially viable. According to Hydrogen Mobility Europe, if hydrogen remains at the current low levels of demand, the cost of producing and supplying hydrogen could be passed onto end users. This would mean that hydrogen vehicles would cost more to run than both battery electric vehicles (BEVs) and fossil-fuelled cars. Therefore, any technology that can drive down cost is crucial to increasing uptake.

Fuel cell electric vehicles constantly convert hydrogen into electricity, which in turn charges the vehicle’s battery. In a process known as regenerative braking, most excess energy can be retained to help power the vehicle. However, if the battery is already fully charged or there is a failure in the system, there must be a mechanism in place to dissipate this energy surplus.

A dynamic braking resistor (DBR) is one of the most efficient ways to safely dissipate excess energy and ensure the system remains operational. Cressall’s EV2 DBR is a water-cooled resistor, which allows for safe dissipation without the need for extra components, resulting in an 80 per cent weight reduction when compared to a conventional air-cooled DBR.

These weight-saving properties lighten the load of the vehicle itself, meaning that it can travel further on the same amount of energy. This is particularly advantageous for weight-sensitive freight vehicles, such as pulp and paper or iron and steel transport. What’s more, the weight of a BEV’s battery or the additional components of an air-cooled DBR would reduce the potential load of the vehicle more than a FCEV would, which makes the EV2 and hydrogen a perfect combination for freight transport.

Nikola’s European hydrogen pipeline and fuel system is a landmark step in facilitating widespread uptake of FCEVs. However, if FCEVs are to overtake BEVs, then the refuelling system has to be accompanied by further developments in vehicle efficiency and hydrogen production to make the resource a completely sustainable, feasible option.

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Diving into marine resistor design

DIVING INTO MARINE RESISTOR DESIGN

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.

When required Cressall can design the resistors to help with your application. Contact us here.

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