Driving down CO2 emissions with fuel-efficient trucks
A European consortium has tested a range of advanced technologies for trucks and other heavy vehicles that has the potential to reduce fuel consumption by up to 18 %, lower CO2 emissions by 13 %, and meet increasingly stringent environmental standards.
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Working in the EU-funded CORE project, truck manufacturers, component-makers and academic institutions have come together to reduce pollution and improve fuel efficiency in a key segment of the transport sector: the heavy duty vehicles that form the backbone of trade and commerce, but which are also responsible for a quarter of CO2 emissions from road transport and around 6 % of total EU emissions.
“While reducing environmental impact is a key target for the transport industry in general, there are specific priorities and challenges for heavy vehicles,” says CORE project coordinator Johan Engström at Volvo Group Trucks Technology. “For example, robustness is even more essential – trucks are designed to travel a million kilometres a year, compared to around 100 000 kilometres for passenger cars. Maintenance and servicing factors are major concerns, and fuel efficiency is the top priority, more so than performance factors.”
Truck manufacturers have also worked hard to meet increasingly strict EU emissions standards over the last two decades. Since the first European emissions legislation, known as EURO I, was introduced in 1993, particulate matter levels from diesel-powered heavy vehicle exhausts have fallen by 97 %and nitrogen oxide (NOx) emissions have dropped 95 %, with the latest EURO VI rules cutting NOx emissions by more than half.
To continue this progress towards cleaner and more efficient heavy vehicles, the CORE team looked at how to make improvements at all stages of the drive train, from reducing friction in the engine to using hybrid electric technology to recycle energy, and enhancing catalytic conversion systems to cut exhaust emissions.
Three engine technologies
Divided into five sub-projects, CORE implemented three different engine technologies supported by two transversal projects studying advanced friction reduction and improvements to catalytic NOx conversion. The technologies were tested in extensive simulations and road trials on prototype trucks, to emulate a variety of real-world driving conditions from inner-city traffic to hilly terrain and long motorway journeys.
“The data showed that any reduction in friction in the engine, including improved piston and ring design and the use of special coatings, almost automatically translates into reduced fuel consumption and lower CO2 emissions of several percent,” Engström says. “However, if you change one parameter in the drive train, it inevitably has a knock-on effect elsewhere.”
For example, a more efficient engine burns less fuel and usually operates at a lower temperature, resulting in cooler exhaust gases. However, standard selective catalytic reduction (SCR) technology, which converts NOx into harmless nitrogen and water with the aid of a catalyst such as urea or ammonia, only works efficiently at certain temperatures.
“Essentially, by making the engine more efficient and lowering CO2 emissions, you end up with more NOx emissions. We therefore researched and implemented methods to broaden the temperature range and exhaust flow rates at which SCR converters function optimally,” the project coordinator explains.
Other technologies studied in the project can help boost fuel efficiency without significant knock-on effects. Hybrid electric technology allows waste energy from braking to be converted into electricity and stored in a battery to back up engine power. Increasingly implemented in passenger cars, hybridisation has not been used for heavy long-haul vehicles to date as it has yet to be proven cost-effective: on long motorway journeys there is little need to brake. However, Engström says that as battery technology improves there could be viable commercial use cases for implementing hybridisation in heavy vehicles because a further reduction in CO2 emissions by a couple of percent may be needed to meet stricter environmental standards in the future.
“We’re at a stage where we are pushing the boundaries of what is achievable with current combustion-engine technology to extract the most efficiency. In CORE, we focused on making incremental changes to existing engines and configurations to ensure that our innovations are close to market,” he says.
The approach should ensure that the advances made by the project’s research will be implemented in commercial vehicles within the next five years, with Volvo and project partners Daimler and IVECO all building on the results in internal development projects, including some follow-up initiatives with component manufacturers.