Heading for hydrogen

Jonathan Welch speaks to Cummins about an alternative use for hydrogen, in the form of the combustion engine

There can’t be anyone in the industry who hasn’t heard of Cummins. The American company, famous for its diesel engines, has had a presence in the UK since 1952, and opened its first manufacturing facility outside the USA in Shotts, North Lanarkshire, in 1956. Its products can be found across many sectors besides bus and coach, including trucks, marine, industrial, power generation and construction.

Today, the company has manufacturing facilities throughout the UK, including in Darlington, Huddersfield and Daventry. The Scottish plant closed in 1998.

In October last year, the company displayed its latest hydrogen combustion engine alongside more familiar products at Busworld Europe. Whilst hydrogen is becoming familiar in the coach and bus industry through fuel cells, Cummins recognises that fuel cell technology might not suit all applications, and also that its hydrogen combustion engine might provide a more sustainable route forward in applications and markets where alternative, zero-emission technology is not yet an answer.

Visitors to the show were able to view Cummins’ B6.7H hydrogen internal combustion engine alongside its Euro 7-compliant X10 advanced diesel engine, and having spoken with representatives on the stand during the event, I was keen to gain a better understanding of how the hydrogen engine works and what benefits it can offer in a market where anything which isn’t fully zero-emission could be seen as a risk.

Although you might expect an engine manufacturer to have a vested interest in selling engines, Cummins believes in making a commitment to providing practical solutions to reduce emissions in heavier-duty or longer-range applications, and offering a zero-carbon, if not zero-emission, option.

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Aimed at coach applications in the 9-10m range, rated at 216kW (290hp) and with 1200Nm peak torque, the B6.7H is accompanied by the larger X15H, with power ratings from 400 to 530hp more suited to larger coaches. Cummins says its hydrogen combustion engines offer diesel-like performance – and give operators a more diesel-like operation – whilst using zero-carbon fuel.

The range has been designed to provide a path to zero-carbon tailpipe emissions that uses technology which is still familiar to manufacturers and operators alike, retaining a similarity with current diesel and natural gas powered vehicles and reducing fleet integration complexity. A high degree of parts commonality also helps minimise cost and improve parts availability for operators with mixed fuel fleets.

Its next generation diesel, the X10, will offer power ratings from 240 to 335kW (320-450hp) and meet proposed Euro 7 ultra-low emissions levels, and Cummins expects fuel savings of up to 5% compared to equivalent Euro VI engines.

In search of efficiency

To find out more, I spoke to William Lamb, Director of Product Strategy at Cummins, and Marketing Communications Director Steve Nendick to find out more about the technology behind a hydrogen-fuelled internal combustion engine, as well as Cummins’ perspective on how such engines can be utilised in the already rapidly decarbonising bus and coach industry and what benefits and challenges they might bring compared to alternatives.

William started off by clarifying what a hydrogen engine is, and how it works. “In principle, it’s the same as a diesel engine,” he explained, “with the versatility and familiarity that brings. It takes the fuel and combusts it just like a diesel or natural gas engine. It’s a spark-ignited fuel like petrol or natural gas, and because there are no carbon elements in hydrogen, there are no carbon emissions, which is why it is of interest.

“You can convert a diesel engine to run on hydrogen, and there are aftermarket retrofitters who do that, but that’s not the route we’ve taken for our new engine platforms. We’ve gone for a bespoke combustion system that’s optimised for spark ignition.

“We’ve designed the new engine range from scratch. We’re calling it a fuel agnostic concept in that the base engine up to the bottom of the cylinder head is largely common whether it’s a diesel, natural gas or hydrogen engine. The cylinder head and pistons are different and highly optimised for either diesel or spark ignition combustion. That gives us real advantages in terms of power, torque, and also efficiency. A diesel engine converted to run on hydrogen would be much less efficient.”

Efficiency seems a difficult concept to grasp though with new technology after years of miles per gallon or kilometres per litre. “It’s measured in kilometres per kilogramme,” William explained, “but obviously a kilogramme of hydrogen doesn’t equate to a litre of diesel, so it’s hard to directly compare. A better way to characterise it is to look at the thermal efficiency of the engine. Diesel engines achieve around 45-50% thermal efficiency. A natural gas engine might achieve around 40%. A hydrogen engine is somewhere in the middle, around 43-46% thermal efficiency.”

What about compared to fuel cells, I asked. “People will say that fuel cells are more efficient, and they are but only in certain conditions,” William clarified. “They tend to be very efficient when running at light load, where efficiencies can reach up to 55-60%. But if you’re running it at a high load then that efficiency drops to around 40%, so there’s a switch-over point where a hydrogen combustion engine becomes more efficient.

“We’re not saying that one is better than the other. We design and manufacture fuel cells as well. They offer different benefits for different applications and to some extent they support each other in that they use the same fuel, which supports the need for wider-reaching hydrogen fuelling infrastructure.”

Supporting infrastructure

Given the worries around production of non-green hydrogen, not to mention that at least one existing hydrogen fleet is already hampered in operation by lack of investment in the installation of the necessary supporting infrastructure, I wondered what William thought was needed to overcome that. “I think there’s lots of interest in Europe and beyond where sustainability and/or the energy security of hydrogen is high on the agenda. There are places where it already makes sense and can be done on a local scale,” he explained. “In the next three to five years, more will start to happen, probably around hubs that companies or governments have set up.

“I think public infrastructure is further away, into the late 2020s or early 2030s, but we’ve seen huge investment pledged to kick-start both the generation and distribution sides.”

“The Tees Valley Mayor is looking at creating a hydrogen hub in the region, and of course we’re based right there in Darlington,” added Steve. “It’s in its early stages but we’re supporting the project, and looking for other opportunities where we can help to build and invest in hydrogen.

“Cummins is also involved in the production of electrolysers which can create green hydrogen from wind, solar and hydro power now through our acquisition of Hydrogenics a few years ago. We have factories in Canada and Belgium and we’re opening a new one in Spain soon. We’re seeing a very high demand for those right now, though not in transport. It’s coming more from the power generation industry.

“We’re part of the whole supply chain. We have electrolysers, as well as a joint venture with NPROXX for tanks, so we’re not just selling a product that uses the fuel. We want to be part of that whole supply chain, which is quite a change in our strategy.”

Market segments

Speaking about current demand for hydrogen combustion engines, William explained: “It’s the on-highway heavy duty segment that drives a lot of new technologies. We’re seeing that in the US, in China, and in Europe, wherever there’s legislation to reduce greenhouse gases in a very tight timescale.

“Battery electric has potential, but also limitations with heavier-duty operations, and fuel cells are likely to remain quite expensive for some time, so hydrogen combustion seems like a pragmatic alternative that offers the required range but with zero carbon tailpipe emissions. Off highway isn’t driven by legislation, demand there is driven by ESG goals, and that translates into contracts which specify a certain percentage of zero emission vehicles.

“The urban bus market is very heavily focused on battery electric and will likely continue to be. But there are opportunities for those vehicles used on cycles which are challenging to achieve with battery electric, such as coaches and inter-city buses, as well as those operating at altitude or in cold conditions. It will suit operations where people are needing diesel-like performance and flexibility, but want to decarbonise those routes as well.”

Engine sizes

William pointed out that although many parts of the worldwide Cummins business are now looking at hydrogen solutions, the initial development work began in the UK. “We received government funding through the Advanced Propulsion Centre which kick-started the development work on the 6.7-litre medium-duty engine,” he said. “That project has been running for around two years now, and brought a lot of technology development and learning which we’ve been able to feed into our development programmes at our technical centres in the US, UK, India and China.

“We’re prioritising the 6.7-litre, which will be the first to hit the market. Shortly after that will be the new 15-litre platform as well, the X15.”

Could the perceptions around hydrogen, either as a fuel in general or as an internal combustion engine, be an issue for uptake, I wondered? “To some extent, it’s a case of horses for courses,” William said. “Different technologies have benefits, and the benefit of hydrogen combustion is that it uses zero-carbon fuel at a lower investment cost than some of the alternatives, plus it’s a known and familiar technology. It will still produce a very small amount of NOx and a very small amount of particulates, but it’s entirely capable of meeting the proposed Euro 7 standards for 2029 and onwards.

“Battery electric and fuel cell solutions might have an advantage in urban environments, but for interurban and long-haul operation, I think the pragmatic balance of being affordable, familiar and easily refillable while offering zero-carbon emissions is a good trade-off.

“The UK Government has not adopted the European approach and is pushing for 100% zero-emission for on-highway use, but we’re working with the industry to say that it’s maybe too idealistic in its approach. Europe has changed tack already to allow hydrogen combustion to be categorised as a zero carbon vehicle.”

“It’s useful to remember too that on the engine side, the long-established engine families have quite a range of power. For example our 6.7 litre diesel can produce from 150 to 326hp, so it can cover a range of applications,” added Steve. “When you look at new technology, they have to be sized to the duty cycle of the vehicle from a cost and installation perspective. The knowledge of the expected duty cycle is a lot more critical, whereas a hydrogen combustion engine retains a lot more of the flexibility we have with diesel.”

Unprecedented development

“We’re currently rolling out our new fuel-agnostic engine platforms, which the B6.7H and the X10 advanced diesel engine seen at Busworld Europe are part of,” continued William. “We’re making extensive investments in our engine technology, which is a sign of our confidence in the combustion engine. We recognise that it’s not going to be the same everywhere, and that different countries and markets will adopt different solutions.

“We see it as a more pragmatic solution; whereas today diesel is used in the majority of vehicles, in future there will be a much bigger mix of fuels, including biogas, ethanol, diesel, hydrogen, natural gas depending on what’s available and incentivised in particular countries, as well as fuel cells, battery electric and hybrid options.

“With our new fuel-agnostic platform, we’ve designed-in the ability to cover all of those different fuels to suit different markets. We believe there’s a lot of life yet for the combustion engine.”

Although Cummins’ hydrogen internal combustion engines are at the prototype stage, Cummins has a wide base of manufacturers using its diesel and natural gas products, across an equally wide swathe of sectors. Installation of a hydrogen engine in a vehicle should be a lot less complicated than a fuel cell, given that a large part of the engine, including mounting points, are the same as with current natural gas products. An after-treatment system will also still be needed, which could be smaller but similar in function to a diesel vehicle. The 350 or 700 bar tanks could be roof-mounted in the same way as on current gas buses.

“As we get closer to 2030, that’s when the legislation starts to get really stringent,” William explained, “so that’s when we expect to see demand really start to ramp up.“

With lots of markets to consider beyond the UK, Cummins certainly sees a strong future in cleaner combustion engines, and is investing significant sums into its development here in the UK.

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