PARIS – Speakers at a hybrid-powertrain conference here say 70% of new cars in Europe in 2020 will need electrification to meet the European Union’s goal of 95 g/km of carbon-dioxide emissions.
To meet goals expected for 2030, every car will require electrification and will need to lose 30% of their mass, a top Renault engineer says.
Low-cost mild-hybridization is the principal subject at the ICE Powertrain Electrification & Energy Recovery conference sponsored by the French auto engineer organization SIA. Industry experts say mild hybrids use a small energy-storage system that can recover braking energy quickly, and software that reuses it just as quickly to keep the internal-combustion engine working efficiently.
French supplier Valeo is using supercapacitors to store energy in its prototype low-cost hybrid system, while other vehicles are being developed for 48V lithium-ion batteries. AVL, the Austrian engine developer, is working with a battery group to develop a 48V lead-acid battery.
“The long-term vision in Europe is to reduce the use of conventional fuel by a factor of three in 2030 and by a factor of 10 in 2050,” says Philippe Doublet, in charge of CO2 emissions strategy at Renault, citing a 2011 White Paper on Transport. The EU wants to phase out all conventionally fueled cars in cities by 2050, and most trucks.
To achieve the potential 2030 goal of a car emitting about 55 g/km of CO2, the equivalent of about 100 mpg using gasoline, electrification alone won’t be enough, Doublet says. “It is achievable only by a combination of reduction of the energy required and electrification.”
Doublet predicts average mass must be cut 30% and aerodynamic and rolling friction reduced along with other onboard electric consumption, while powertrains will need to continue progressing.
“These two directions are very expensive and sometimes contradictory,” he says, noting that hybridization adds weight. “As our customers won’t pay more, we need a breakthrough in technology and the right combination of technologies to make (hybrid-electric) vehicles affordable for our customers.”
Using the Renault Clio as an example, Doublet says that without electrification, a diesel Clio emits 83 g/km and a gasoline version 99. By cutting the weight and other energy requirements and hybridizing the engine, the gas Clio could drop its CO2 emissions to 60 g/km, while turning it into a plug-in hybrid could reduce the CO2 to 30 g/km.
Renault already has gambled €4 billion ($5.2 billion) on developing electric cars, but it intends to meet the 85 g/km goal without counting the contribution of its electric fleet, Doublet says in an earlier presentation to the French government.
The auto maker is working with Valeo and other suppliers to develop mild hybrids using a 48V architecture, says Philippe Bernet, engineer in charge of advance transmissions and electrification. He says using a 48V lead-acid battery to recover energy is not out of the question, as it would be less expensive if one can be developed.
AVL in Austria also is working on low-cost hybridization, says engineer Thomas Pels. The goal is to keep performance high while reducing CO2 emissions, and it believes a 48V hybrid system producing 6kW-8kW is the right size to make a significant contribution to fuel economy.
The German auto industry, headed by three world-class luxury brands, mainly is interested in what 48V can do for additional comfort features such as heated steering wheels and premium audio systems, he says. But once the 48V system is in place, it makes hybridization and energy-saving easier.
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Because currents are reduced with 48V, less copper wire is needed, and plenty of power available to run air-conditioning compressors, vacuum pumps and electric superchargers, all features that would be needed for a downsized hybridized powertrain.
Pels says a 48V hybrid version of a 1.2L engine with an electric supercharger could match or beat the performance of a 1.8L Tsi engine while reducing fuel consumption 24%.
AVL worked with the Advanced Lead-Acid Battery Consortium to produce a prototype Volkswagen Passat shown at a powertrain conference in Vienna in April that uses a 48V lead-acid battery. Nick Pascoe, CEO of U.K.-based Controlled Power Technologies, says using the lead-acid battery means the add-on cost to the customer for a mild hybrid would be only €1,150 ($1,500).
Pels says many auto makers limit their 48V planning to Li-ion batteries, “but there is safety, lifetime and quality to be considered.” Lead acid has high specific power of 800-1,000 W/kg, but is weak in specific energy at 35Wh/kg-40 Wh/kg.
“While this is certainly a disadvantage, we believe we can package those batteries and it should not be the sole criteria,” he says. “OEMs should take it seriously. The test results are promising, and it makes sense to further evaluate this technology.” As for hybridizing diesels, “combining expensive electrification with an expensive powertrain is not evident.”
Valeo’s mild-hybrid approach is similar, says engineer Damien Fournigault. In tests integrating its 48V electric supercharger on a 1.6L turbocharged gasoline direct-injection engine, the supplier calculates stop/start cuts consumption 5.5%, braking regeneration and torque assist another 5% and a zero-emissions electric mode an additional 3.4%. Valeo’s first such system will be in production in 2015-2016.
Both Valeo and AVL also are working on connecting GPS and sensor information to the system to predict energy requirements, which will allow a car to better manage its limited electric storage capability.
Knowing the vehicle must slow down for a coming roundabout, for example, Valeo’s “Copilot" could cut off fuel injection and switch to electric power before the driver lifts his foot off the accelerator, because the car will know that the battery will be recharged at the roundabout.
Valeo believes the system could add up to 3% in real-world fuel-savings, although just 1%-2% on the New European Driving Cycle homologation driving cycle.
AVL’s Laurent Allouchery, a veteran of PSA Peugeot Citroen and Renault, estimates adding predictive energy requirements to a car will allow the battery to charge and discharge at the optimal state of charge and will cut fuel consumption 3%-4%.
“It is a cheap way to reduce CO2 emissions and get a better battery lifetime,” he says. “Customers will see the benefit.”
While it’s clear to these engineers that the internal-combustion engine will survive at least through 2030, “the powertrain can’t do it alone,” says Renault’s Doublet. “It needs energy recovery, and it has to be combined with huge reduction of vehicle energy needs. It has to be right-sized accordingly. The zero-emissions vehicle in the city is a must for the long term.”