Dual fuel duel06 July 2011

Alternatives to standard diesel are rising slowly up fleet engineers' agendas but, as Dave Young find out, they may be limited by refuelling infrastructure and operator acceptance

During the 1990s two retailers, Body Shop and M&S, operated CNG-powered (compressed natural gas) trucks. The two upmarket chains shared an environmentally aware customer base and, as own account operators, could offset higher running costs against good PR. Gas powered vehicles weren't new even then; several local authority fleets (London Borough of Haringey, for example) ran dual fuel petrol/methane LCVs, but these ERFs (now MANs) were rarities.

A generation hence, and dual/alternative/hybrid fuel chassis have scarcely penetrated the HGV market. But for LCVs the picture is different: gas and electric power are making their ways onto fleets, not least because the shorter range and depot refuelling make such vans less vulnerable to fuel infrastructure shortcomings.

Higher up the gvw range, however, and product is thin on the ground. A 6x2 rear-steer rigid diesel-electric Renault Premium Distribution is in service with Norbert Dentressangle, delivering wine in south east England, but it is not yet part of the UK model range. The truck's powertrain consists of an automated gearshift, DXi7 310bhp SCR (selective catalytic reduction) engine and a 120kW (peak power) electric motor connected to lithium-ion traction batteries that generate a 20% diesel fuel saving and 6db noise reduction, at the cost of an 800kg payload penalty. Braking is assisted by a retarder, simultaneously slowing the vehicle and generating electricity. By recovering and storing kinetic energy when decelerating, the batteries function autonomously and don't require external recharging.

Warburtons has six dual-fuel (CNG/diesel) Mercedes-Benz Axor tractor units – converted by the Hardstaff Group, with full manufacturer approval and support – on its distribution fleet, working double-shifted, seven days per week and averaging 100,000 miles per year across the UK. The baker has used gas-powered trucks for 10 years; indeed, 20% of its 100 tractors already run on CNG. Group transport manager Mark Sutcliffe says: "We're committed to gas for environmental reasons. It's a clean fuel that helps us to reduce our emissions and so meet our own carbon management and corporate social responsibility targets. But the trucks also had to make financial sense, and a dependable warranty is a key part of that equation." Warburtons' Axors are contract hired for seven years from CharterWay.

CCE's CBM Stralis
Meanwhile, Coca-Cola Enterprises (CCE) has begun trials with an Iveco Stralis Active Day 21 tonne distribution vehicle running on compressed biomethane (CBM) to help determine the UK firm's sustainable transport strategy. Darren O'Donnell, logistics asset manager at CCE, explains: "Our primary reason for selecting CBM is that it has the lowest carbon intensity of all commercially available alternative fuels. The gas used to make CBM comes from a landfill site in Surrey, which means it's not depleting any fossil resources."

The Stralis, line-built for natural gas-powered applications, features a six cylinder, 7.8-litre, 300bhp Cursor engine, driven through an Allison six-speed automated gearbox. Its performance will be carefully monitored by Cenex – the government's centre of excellence for low carbon and fuel cell technologies.

Waitrose, too, is currently operating five Mercedes-Benz Sprinters, also running partially on sustainable fuel made from landfill gas. The 3.5-tonne 316 NGTs, with insulated bodies, are bi-fuel vehicles, powered by either petrol or gas. Ray Collington, fleet engineer at John Lewis Partnership, which includes Waitrose, says that the 1.8-litre, four-cylinder engines – upgraded to meet the voluntary EEV (enhanced environmentally friendly vehicle) emissions threshold – delivers 156bhp, irrespective of the fuel source. "We're keen to learn from these new vehicles, because we firmly believe that gas – in this case bio-methane produced using locally-sourced, sustainable materials – has a viable future as an alternative fuel source," explains Collington.

And fuel innovation is also being pursued by firms in the component supply chain. Axeon, Europe's largest independent lithium-ion automotive battery systems supplier, has been awarded research funding from the EU to reduce the weight, volume and cost of batteries in electric and hybrid vehicles, as part of a consortium programme called SmartBatt. Targets for a 20kWh battery include: weight down by 10—15%); volume 20—30%; and cost 5—10%.

Chris Smith, managing director of multi-fuelling systems firm G-volution, disagrees with those who say all this work is just stop-gap engineering. "It's a genuine alternative to diesel, which can operate from today until the emergence of fuel cell HGVs. We have some heavyweight backing on this view from our technical guru, Doug Greenhalgh [ex-chair, IEA Clean Combustion Committee], as well as some fuel companies."

His point: multi-fuelling operates within the current fuel infrastructure and can allow the roll-out of more fuels, more easily than any alternative. As Volvo and many of the other truck majors say: the diesel engine remains the most efficient engine, so multi fuelling based on diesel engines will remain the greenest alternative for many, many years.

View from the top
Away from the views of operators and suppliers, major truck manufacturers are taking a cautious view of the alternative fuels market. "We're beginning to see volume take-up of small vehicles, which suit gas and electric power," states Tony Pain, marketing director of DAF Trucks UK. "For heavies, though, the future will continue to be diesel-powered. To get the same energy from a 400-litre diesel tank requires the equivalent of 108 tonnes of lead acid batteries."

Why? Because a 44-tonne gvw truck needs around 200bhp on the motorway but 400bhp to pull away from stationary – so that's a lot of power. And Pain point to significant improvements in conventional diesel-only engine technology that make it a hard act to follow. A recent road test comparison by DAF revealed that in 1960, a top weight truck returned about 8mpg, at 24 tonnes gvw and averaging 24mph over the route. Today a 44-tonne gvw vehicle returns at least 8mpg (often better) at an average 47mph – that's a fourfold productivity increase.

"Not only can gas and electric fuel limit a vehicle's range but also its flexibility of operation," says Pain "Recharging batteries overnight, for example, means a vehicle is not available for double shifting. The diesel engine will continue to be most efficient. A DfT Low Carbon Supply Chain Steering Group report recently revealed that over 99% of heavy chassis purchases in the UK are diesel."

This in turn affects the market: without volume sales and economies of scale the unit cost of multi-fuelled vehicles will remain much higher. Pain suggests prices can sometimes be double that of their diesel-only peers, with most being retro converted – tough in an industry with around 6% profit margin. Then there's the unknown issue of residual value, meaning that diesel-electric hybrids, at least, have to be leased rather than purchased.

And there are still practical concerns. Pain points to last winter, when temperatures fell below 11°C and halted gas-powered bus services in the north of England. And he adds: "Given the payload penalty of biogas, perhaps it might more effectively reduce emissions by being used for heating fuel."

So what will the diesel of the future look like? Pain predicts it will split roughly as 33% each synthetic, fossil fuel and biomass. With those source, he insists, diesel engines will predominate in heavy trucks for at least the next 15 years.

Meanwhile, UK buyers may purchase a AF 12-tonne hybrid (160bhp EEV diesel engine/60kW electric motor) off-the-peg, offering a "30—40% fuel and emissions reduction," advises Pain.

Electric dreams, diesel reality
For Nigel Emms, director of brand and communications at Iveco UK, the next few years is set for diesel domination. "The electric dream won't go above 3.5-tonnes," he predicts. Not for want of manufacturing technology, but because of "the limitations of existing refuelling infrastructure and lack of government backing," he continues.

"Manufacturers need a clear minimum five-year political support strategy to justify investment, and are looking for a lead and incentives from a government that, thus far, has an inconsistent stop/start approach to green energy," assets Emms. He points to the withdrawal of Energy Savings Trust grants. "Other countries, such as Benelux, have subsidies, and these can be soft or hard, product or infrastructural, tax breaks or price support. Such initiatives could stimulate the green manufacturing economy."

For Iveco UK, its current multi-fuel focus is on the LCV market and the Daily model range. "CNG has turned a corner," reveals Emms. "That business is starting to move, because it's a viable option. We see few heavy conversions but lots of Daily conversions. Tesco has recently taken 25 on long-term evaluation. They're also ideal for central London, being congestion charge exempt." Indeed, Emms claims the payback on a CNG Daily is three to four years over a seven-year life.

Iveco's alternative fuel range is based upon CNG (UK) or electric for the Daily (lightweights); Eurocargo as hybrid or CNG (mid-range); and Stralis, CNG or LNG (heavy, but not yet in the UK). Pricing is "dependent on volume and government support," concludes Emms.

Given the advent of Euro 6, a decline in the overall UK HGV park and many other means (both specification and operational) of reducing road transport's carbon footprint, diesel-fuelled engines will dominate the heavy truck sector for the immediate future, with small numbers of dual/alternate fuel lorries employed on niche operations.

The product is present, but government's strategic role is lacking. As the FTA recently stated: "For the logistics sector, many opportunities to reduce carbon dioxide emissions have the potential to be a win-win, with cost reduction going hand-in-hand with cutting fuel use. However, what can be done at an individual operator level and by vehicle manufacturers can only get us so far. We are looking to government to reward those embracing this philosophy, rather than punitively taxing them."

Dave Young

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