Hybrid trucks will be unfairly penalised unless EU rules that fail to take into account the actual amount of pollutants emitted in real-life operation are changed, says Volvo. It says that the certification procedures applied to hybrid trucks should be the same as those used on cars and light vans which measure the weight of pollutants emitted per kilometre travelled. At the moment hybrid trucks are dealt with in the same way as regular diesel-engined LGVs - using the grams/kilowatt-hour measurement, related to the engine's horsepower rating - meaning that any hybrid truck is effectively judged only on the horsepower rating of its diesel-engine. This ignores the fact that the diesel part of the engine is frequently inactive or working at very low power. Volvo made its comments in a presentation of hybrid technology to EC officials and members of the European Parliament in Brussels last week.
Compliance
Anders Kroon, director of Volvo's hybrid vehicle project, pointed out that Euro 5 or 6 compliance certification discriminated against hybrids when real-life emissions were being assessed. A diesel-electric hybrid truck working in air quality sensitive city centre conditions, typically accelerated away from rest under electric power only, with the engine shut down, producing zero emissions. Furthermore, said Kroon, the automatic engine stop-start feature included in most hybrid packages eliminated idling while stationary at traffic lights where normally emissions were high. In simulated urban operation, comparing Volvo's parallel hybrid powertrain with an equivalent Euro 3 diesel, it had been found that total (g/km) emissions of oxides of nitrogen (NOx) were reduced by as much as 90% and particulate matter (PM) by up to 95%, even though the engine was to regular Euro 4 specification.
At the Brussels presentation the main emphasis, both from Volvo and from European transport commissioner Stavros Dimas in his introductory remarks, was on the potential for hybrid commercial vehicles to save fuel and reduce greenhouse gas emissions. Dimas acknowledged that European legislators had, till now, placed more stress on improving average passenger car fuel consumption, largely ignoring trucks and buses. In North America a number of incentivised fuel-saving programmes for heavy vehicles were now up and running, and Europe could perhaps learn from that experience.
Jan-Eric Sundgren, Volvo senior vice-president responsible for environmental affairs, said the fuel efficiency of diesel engines was expected to go on improving with advances in fuel systems, air handling and combustion technology. Over the 15-year period from 2005 to 2020, diesel fuel consumption should improve by 15 to 20%. But with the addition of hybrid powertrains those improvements could be greatly enhanced, particularly for trucks working in heavily-trafficked urban areas and/or on frequent delivery or collection working. He cited the Greater London area as the ideal application for hybrids, where stop-starts were sufficiently frequent for electrical power from regenerative braking to contribute significantly to a vehicle's energy needs. Sundgren said that urban refuse collection vehicles (RCVs) are perhaps the most worthwhile application, where fuel savings of 25 to 35% could be expected.
He added though that on RCV operation which involved little distance running, extra battery charging via an overnight mains 'plug in' facility might be necessary. He argued that 'plug in' hybrids should not be derided, as some critics had done in the US. Mains electric power was generally more fuel efficient and often cleaner - depending on the fuel burned at the power station - than the same amount of power generated by a hybrid vehicle's engine. Kroon said he envisaged that on future hybrid vehicles, many truck auxiliaries, which today were mechanically belt or gear driven - continuously - from the engine, being electrically powered, only when required. Those included power-steering pumps and brake system air compressors. More obviously, all the regular on-board electrics which now rely on a separate alternator, would draw their power from the main traction battery pack, in turn charged by the I-SAM (integrated starter alternator motor) at the heart of most of today's prototype truck hybrid powertrains.
Prototype
Volvo's first current-generation hybrid truck, seen in Brussels but first shown last autumn at the Hanover Show, is a 26-tonne GVW FM9 rigid six-wheeler. Its 290hp 9.4 litre D9 engine is retained, though Kroon says that a production version would almost certainly have the company's smaller Deutz-built 7.2 litre D7 unit, exploiting the now well-recognised potential of hybrid development for engine downsizing. The engine is coupled directly to the 250mm-long I-SAM unit, which on Volvo's prototype hybrids (including a bus) has been sourced from Canadian company TM4 Transport, based in Boucherville, Quebec. In electric traction drive mode, the I-SAM is rated at 120kw (roughly 160hp), but more impressively it exerts a maximum 800Nm of torque which - as with all electric motors - is available from zero revs, to confer impressive acceleration characteristics.
Specifications
In generator mode it provides the main charge to the batteries which, on the FM9 hybrid, are 600v nickel metal hydride (NiMH) units with a total energy capacity of 9.6kWh. Volvo makes clear that battery specification will prove crucial if hybrids are to be made acceptable in terms of cost, weight and chassis space. Unfortunately the lighter the batteries the more they cost. The NiMH batteries on the FM9 weigh 550kg. A cheaper alternative would be the traditional lead-acid type, but they would weigh up to 1,500kg. Volvo is however collaborating with Effpower, a Swedish battery maker, to produce a more advanced lead-acid battery which would be 30 to 50% lighter.
Lithium-ion is a further option which could bring battery weight down to just 150kg, but the cost is regarded at present as unacceptably high. So-called supercapacitors are another light but costly option and are unaffected by low temperature and they should last the life of the vehicle. Other operational hybrid attractions highlighted by Volvo include the 'free' retarder function of regenerative braking. Experience in North America on RCVs suggests a seven-fold increase in brake pad life.
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