Volvo Trucks is set to launch a concept heavy-duty long-haul hybrid truck along with production gas-powered engines before the end of the year, as it seeks alternatives to diesel for a variety of transport solutions.
Speaking at Volvo Trucks’ Future Trends & Innovation event held at the Slovakia Ring race circuit near Bratislava, Slovakia, Volvo’s engine product manager Mats Franzen recalled that back in 2007, the company had built seven externally identical trucks running on seven different alternative fuels, and had sent them on a tour of world leaders to ask which alternatives the political leaders would prefer to see developed.
“There was no answer from the politicians,” he recounted.
“We decided diesel engines should remain at the core of our production,” he recounted, and pointed out the tremendous improvements made in terms of diesel power output, fuel economy and emissions reduction since then.
However, the development of alternatives continued, with four leading contenders – dimethyl ether (DME), hydro-treated vegetable oil (HVO), methane (CNG/LNG) and electricity – emerging as Volvo decided to continue to develop those fuels it thought were most likely to be viable.
Mr Franzen produced a graph showing how alternative fuels progressed from innovation, through a ‘peak of inflated expectation’ and into a ‘trough of disappointmen’t before (sometimes) climbing a ‘slope of enlightenment’ and reaching a ‘plateau of productivity’.
DME was a fuel that had stalled because of difficulty in sourcing it from renewable feedstock, even though it could be made from forestry waste. HVO was promising as a direct and renewable replacement for diesel for all Volvo engines from Euro 3 onwards, but methane was showing the most potential.
“Electricity,” he warned, “is currently at the top of the hype curve.”
Volvo had offered a production hybrid truck from 2007, but production of it ended with the introduction of Euro 6 emissions limits. The FE Hybrid’s performance had not been thought good enough to make an update worthwhile.
“We expected the battery industry to develop smaller, lighter and less expensive batteries, but that didn’t happen,” Mr Franzen said.
“However, there are now some interesting developments.
“Volvo Bus is now offering hybrids, plug-ins and full-electrics. So Volvo Group is leading with electric mobility and is prepared to take the step with trucks when the time comes.
“Electric roads will be the solution for long-haul,” he asserted, explaining that Volvo had a test track where an electric truck drew current from the road like a giant Scalextric car.
This would obviously require massive infrastructure investment, so in the meantime Volvo Trucks had turned its attention to a long-haul hybrid solution. This had started under the Obama administration as a US Government-backed project known as SuperTruck, and had become a joint Volvo Trucks Sweden and Volvo Trucks North America venture, which was now at the final testing stage.
The objective had been to achieve a 50 per cent improvement in litres per tonne-payload/km efficiency over a standard 2009 Class 8 truck, and this had not been possible to achieve by hybridisation alone. So attention had turned to aerodynamics, resulting in an FH-based design that substituted cameras for rear-view mirrors, had a rounded cab-front and enclosed centre and drive-axle wheels.
This had generated 30 per cent of the saving in drag that was eventually achieved, with the rest coming from attention to the trailer, with a boat-tail being the most significant factor. Other changes included an air management system under the trailer, a profiled trailer roof and careful matching of the front of the trailer with the rear of the cab. The resultant vehicle had “the same CD (drag coefficient) as a Lamborghini sports car”.
Mr Franzen (pictured) emphasised that the combination was a practical design: one side of the trailer opened to facilitate unloading, while the trailer floor was strong enough to support the weight of a forklift driven inside.
Attention had been given to reducing rolling resistance, with liftable front and rear trailer axles, and low-resistance tyres from Continental fitted. Careful attention to weight had saved 1900 kg.
There were few details forthcoming about the driveline, which appears to be a parallel hybrid with a D13 420 diesel engine. But Mr Franzen said that, when the truck was driven on downhill slopes of greater than one per cent, the battery was replenished by regenerative braking, and it was possible for the truck to cover up to 30 per cent of its mileage without running the diesel engine.
A GPS mapping system based on Volvo’s I-See system used predictive technology to ensure optimum battery charging, and could be programmed to ensure that the truck’s diesel engine was not run in sensitive areas. The 6×2 tractor shown at the event had all the aerodynamic features of the hybrid, but ran a conventional driveline.
The finished concept had yielded a fuel saving in the order of 30 per cent.
On gas engines, Volvo was not going to follow Iveco and Scania in developing a spark-ignition solution. Mr Franzen maintained that compression ignition technology was far more efficient, and only a small amount of diesel would be injected to initiate gas ignition.
“Otto (spark) engines are 15 to 25 per cent less efficient than diesel.”
Challenged by Transport Operator on the issue of methane slip, which has plagued aftermarket dual-fuel conversions, he maintained that this was caused because methane was being injected too early and it was escaping through the still-open exhaust valve. This would not be a problem with the Volvo design, where 90 per cent of the burn was methane and injection was closely controlled.
He said the small amount of diesel used was best described as a “fluid spark-plug.” In contrast, the burn on aftermarket conversions had been 40 per cent diesel, and gas injection was not closely controlled.
Mr Franzen said that gas-powered versions of the FH and FM for long-haul use would be available before the end of the year in markets where there was a good gas distribution network such as the UK. Engines would have outputs of 420-460 hp, with torque comparable to diesel engines of the same power, making them ideal for motorway and long-haul use.
“We have diesel performance and robustness, and the same driveability. Payback depends on the relative prices of the fuels, but the more distance is covered the quicker it will be,” he asserted, adding that using liquid natural gas meant range and refuelling times were not an issue.
Methane was an important fuel from an environmental point of view because as natural gas it was one of the cleanest fossil fuels, and it paved the way to the use of bio-gas: carbon-neutral methane derived from organic waste.