Volvo steps on the gas

“This is much more than a product launch for us. This is a step towards sustainable transport solutions.”

So declared Lars Mårtensson, Volvo Trucks director of environment and innovation, at the official unveiling recently at a test track near Barcelona, Spain of a range of FM and FH regional and long-haul trucks fuelled by liquefied natural gas (LNG). They go into production at Volvo Group’s main European truck assembly plant in Gothenburg, Sweden in January 2018, to be sold, initially at least, only in western Europe.

Has Mårtensson uncharacteristically allowed marketing hyperbole to get the better of more cool-headed engineering assessment of the latest additions to the FM and FH truck ranges? Maybe not, even though there is surely nothing revolutionary about trucks running on gas instead of diesel, and Volvo itself is no stranger to this alternative fuel.

Take its FE middleweight range (up to 18 tonnes GVW), for instance. This has been available with the option of a 320hp, 8.9-litre gas engine for more than three years. And some rival truck-makers could argue that they are way ahead of Volvo in the introduction of more powerful gas engines.

Iveco boss Pierre Lahutte claims to have started a “natural gas long-haul revolution” with the launch of the 400hp Stralis NP at last year’s Hannover commercial vehicles show.

More recently came the addition of a 460hp version of the 12.9-litre Cursor 13 gas engine to the Iveco Stralis line-up, and no time has been wasted in winning some eye-catching orders.

At the Solutrans show in Lyon, France in October 2017 Iveco announced that one of France’s biggest road haulage firms, Jacky Perrenot, is buying 200 Stralis NP tractors at 460hp to join the 250 at 400hp it has been running since 2016. There are now reckoned to be around 23,000 gas-fuelled Iveco vehicles (trucks, buses and vans) in operation globally.

Clever combustion makes the difference

What makes the new FM and FH gas-powered Volvo trucks any different from these, and indeed all others to date?

In essence, it is the clever gas/diesel injection system at the heart of the G13C version of Volvo’s familiar 12.8-litre, in-line six-cylinder D13 engine. All other purely-gas truck engines (as distinct from dual-fuel engines) to date, including those from Iveco and Volvo’s own 8.9-litre in the FE, depend on spark plugs to ignite gas in the combustion chambers.

In other words, unlike compression-ignition diesel engines, they are categorised as spark-ignition. This means they inevitably have lower compression ratios and thus are unable to match diesel engine torque and overall fuel efficiency.

The Volvo G13C’s power and torque characteristics are virtually the same as those of similarly rated D13 engines running on diesel alone. And the central point of inviting journalists and operators to the Barcelona test track recently was to demonstrate convincingly how the LNG range performs just as well as similar diesel trucks at the same weight.

The Volvo G13C’s injection system, designated HPDI (high pressure direct injection), was designed by Westport Innovations, a long-established Canadian company specialising in natural gas engines.

A 50/50 joint venture between Westport and diesel engine manufacturer Cummins was set up in 2001 to develop and produce Cummins gas engines. But Volvo, not Cummins, is believed to be the first diesel engine manufacturer anywhere to fully adopt the latest Westport HPDI injector (HPDI 2.0). It was developed jointly with and is manufactured by Delphi Automotive.

The injector has two concentric needles to allow two separate fuels to be injected. A small amount of diesel is injected first to initiate combustion. One Volvo engineer describes this graphically as something like a liquid spark plug. But virtually all the engine’s power comes from burning gas.

Some engineers may wonder, therefore, whether this engine really ought to be described as dual-fuel rather than gas. Volvo engineers are having none of it, insisting that it is categorised not only by them but also by independent type approval authorities as a gas engine, not least because the amount of diesel it uses is so small, no more than 5% against 95% gas.

A wide range of LNG tank sizes, said to give refuelling ranges up to 1,000km, will be on offer for the new FM and FH 420 and 460hp gas trucks when they go on sale in 2018. But the only diesel tank size available to go with them will be 170 litres.

Nevertheless, Volvo points out that the trucks do have a useful sort of limp-home ability, just in case they run out of LNG. Running on diesel only, maximum engine power output would be limited to 50hp.

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LNG offers one solution to emissions reduction

The timing of this unveiling of FM and FH regional and long-haul trucks fuelled by gas is significant. It comes as more and more fleet operators and, crucially, many big transport and logistics buyers across Europe are focusing more intensely than ever on how to cut emissions of carbon dioxide (CO2) and other greenhouse gases responsible for climate change.

Back in May, the European Commission finalised the long-awaited European Union regulation on CO2 emissions from heavy trucks and buses. This will mean that from early 2019 every heavy truck model sold in Europe will have to come with a declaration on its CO2 emissions (fuel economy, in other words).

The figures will be calculated by the VECTO (Vehicle Energy Consumption Calculation Tool) software which has been under development for decades. Volvo evidently hopes to steal a march on rivals with LNG trucks, which seem likely to have eye-catching VECTO figures but which offer nearly all the familiar practical benefits of diesel-only trucks.

“Many of our customers and their customers already work hard to reduce their environmental footprint,” says Mårtensson. “This regulation will drive the development of lower emissions, where we see a clear possibility for increasing LNG market shares as a vital part of the solution.

“Our vision is that trucks from Volvo will eventually have zero emissions, although the way of achieving that is not by one single solution but rather through several solutions in parallel.”

Like diesel, natural gas (methane) is a fossil fuel, he acknowledges. But its CO2 emissions can be 20% lower than diesel’s, he argues. If the gas is biomethane then the well-to-wheel cut in CO2 emissions is 100%.

But methane is itself a potent greenhouse gas. Growing popularity of dual-fuel (diesel and gas) truck engines in the UK was killed off about a year ago by the discovery of an alarming amount of “methane slip” (where the gas leaked to atmosphere during switching of the engine from diesel to gas and vice versa).

Mårtensson and his colleagues are confident that they have done enough to ensure that methane slip will not occur on their LNG trucks or their fuelling systems. Extensive training of dealer network technicians is underway, as is delivery of the specialist equipment needed for workshops.

The supply of biogas is limited at present, he concedes, but describes long-term availability of natural gas as “excellent in a global perspective.”

Given the recent increasing popularity of gas as a truck fuel in the US, it seems surprising on the face of it that Volvo is deliberately confining the introduction of its latest long-haul LNG ranges to Western Europe.

The explanation seems to lie in the need for a reliable gas refuelling infrastructure. The European Commission and many EU member states now are firmly committed to expanding this refuelling network across western Europe. And the substantially lower price of LNG compared with diesel in most European countries at present is another important plus point.

“All told, this makes liquefied gas the best widely available climate alternative on the market for regional and long-haul transport,” says Mårtensson.

“What is needed now is gas-powered trucks that can compete with diesel in terms of performance and fuel consumption, and continued expansion of LNG infrastructure. In both cases major progress has been achieved.

“We regard LNG as a long-term first choice alternative to diesel, both for regional and long-haul truck operations where fuel efficiency, payload and productivity are crucial. With a higher proportion of biogas, climate impact can be reduced far more.

“For transport operations in urban environments, where range is not as critical, electrified vehicles will play a greater role in the future. Our vision is that trucks from Volvo will eventually have zero emissions, although the way of achieving that is not by one single solution but through several solutions in parallel. Liquefied natural gas is one of them.”

Price of gas compared to diesel
Average fuel prices across Europe, showing the lower costs of LNG

Operators want to know if LNG will pay off

Among the nitty-gritty questions being asked of Volvo by fleet managers and engineers taking a close look at these new LNG trucks, weight, capital cost, safety and total operating costs are sure to be among the top priorities.

Volvo engineers do not shy away from these topics. Capital cost is one subject on which it is hard to get clear-cut answers. It is clear, however, that the LNG FM and FH trucks will carry substantially heftier price tags than conventional diesel equivalents.

That is hardly surprising, given the double-skinned, stainless steel, LNG tanks and associated pumping and metering equipment, which certainly does not come cheap.

When the trucks go on sale in the UK early in 2018 they are expected to carry a price premium of at least 30% over comparable diesel models. Volvo engineers are confident, however, that it will not be too difficult to show operators how this additional capital cost can easily be more than amortised over the truck’s lifetime.

“With a truck covering 120,000km a year, an operator choosing natural gas instead of diesel can cut CO2 emissions by 18 to 20 tonnes a year,” says Mats Franzén, Volvo Trucks engines product manager.

“Our new trucks running on liquefied natural gas or biogas produce a far smaller climate footprint than diesel trucks do. In addition, they are much more fuel-efficient than the gas-powered trucks available on the market today. This makes gas more viable as a replacement for diesel even for heavy long-haul operations.”

As for kerb weight and thus payload, there is inevitably a penalty from those big, double-skinned LNG tanks. About 100kg on a typical 6×2 tractor, it is reckoned.

Some fleet managers and their drivers may have safety worries about gas tanks. Carl Johan Almqvist, vastly experienced safety director at Volvo Trucks, is more than happy to tackle such concerns head-on. He points to the vast array of tests through which the tanks are put.

“The new LNG trucks are as safe as any Volvo,” he says. “Liquefied natural gas is one of the safest fuels. It is harmless, colourless and odourless but a very cold liquid. So you must wear protective clothing (stout gloves and eye protection) when refuelling.”

The LNG is stored on the truck at about minus 130 degrees Celsius in a cryogenic, vacuum-insulated stainless steel tank at a pressure of about 10 bar. A hydraulic pump inside the tank increases its pressure, vaporises the liquid and thus converts it to high-pressure (300 bar) compressed natural gas (CNG) as it leaves the tank.

After passing through a five-litre “integrated gas module” to stabilise pressure, the gas then passes through a “gas conditioning module” to regulate pressure for injection. Around 90% of the components on the D13 engine are unchanged from the diesel-only version. Service intervals are the same. So too is engine oil specification.

Much of the development effort spent over the past three years, since the Westport HPDI 2.0 injector was first unveiled, has been spent ensuring that any gas leaks between tank and injector are extremely unlikely.

“It’s been an extensive process, but as a result these are going to be very high-performing trucks,” says Franzén. “You will not be able to tell if you are driving a diesel truck or a gas truck. They combine fuel cost savings with CO2 savings and diesel-like durability.”

Volvo LNG 460 in Spain (The Truck Expert)

Tim Blakemore
Tim Blakemore
Tim Blakemore is an award-winning automotive journalist and the former editor of our sister title, Commercial Vehicle Engineer magazine. He is also the UK representative on the panel of judges for the biennial, pan-European Trailer Innovation Award scheme.