Volkswagen launched its Mk VI Golf range in Iceland, but the extra cool news was its serious intent to pursue development of a production plug-in hybrid version. Called the TwinDrive, both common-rail diesel (TDI) and turbocharged direct-injected gasoline (TSI) engines are being considered, with a best combined fuel consumption of 2.5 L/100 km.
Prof. Dr. Martin Winterkorn, Chairman of the VW Board and VW Group CEO, underlined the importance
of the project: “For us, the TwinDrive represents an elementary step along the
path towards the completely electrically driven automobile.” While the electric
motor on a typical hybrid just supplemented the internal combustion (IC) engine, the opposite is the
case with the TwinDrive. “Here, the diesel or gasoline engine
supplements the electric motor,” he said.
At the launch, a 90-kW (121-hp) 1.4-L gasoline was displayed, but a 1.2-L TSI is scheduled and possibly a 1.0-L three-cylinder. Next year, 20 development versions of the TwinDrive will be delivered to users in Berlin for a fleet test that will include government agencies, companies, and families. The information generated will provide VW with data on technical performance and on user driving habits.
VW has stated that it is investing in the “double-digit millions” (of euros) range in advanced development of the technology for the electric-vehicle fleet-test program. If the test proves a success, it would be a positive signal for worldwide climate protection, believes Winterkorn.
The TwinDrive has a lithium-ion battery with 8 kW·h of useable capacity. “It can achieve 12 kW·h, but we have reduced this to enhance life expectancy,” said a VW spokesman. This is deemed sufficient for a typical Berlin commuter journey. The car’s three-phase Wittgenstein electric motor produces 660 N·m (487 lb·ft) of torque. For comparison, a VW diesel V10 Touareg has 750 N·m (553 lb·ft).
The SAFT battery has a mass of about 160 kg (353 lb), and the curb mass of the TwinDrive is some 1.5 t (1.65 ton)—about 200 kg (440 lb) more than that of a comparable conventional Golf. VW is also working with Sanyo on storage systems based on lithium-ion technology. “Our focus in future will be directed more strongly at making electrically powered automobiles alongside ones driven by more efficient combustion engines,” said Winterkorn.
The emissions-free range of the TwinDrive is up to 50 km (31 mi). The car has a single fixed transmission ratio (equivalent to 5th gear), with the electric drive functioning alone at speeds below 50 km/h (31 mph). “Above that speed, the range-extending combustion engine kicks in. It not only propels the car in high gear but as a generator it also recharges the battery,” said a company spokesman.
A significant element of the TwinDrive is a satellite navigation system. When the driver inputs journey details, the car’s integrated computer system will assess likely battery demand to ensure it's sufficient to power the electric motor in urban areas. The TwinDrive also has regenerative braking.
TwinDrive partner E.ON will provide electricity from renewable sources; at present, some 13% of Germany’s electricity is generated via wind power, and this is expected to rise to 30% by 2020. Other companies involved include GAIA and Evonik/Li-tec; Fraunhofer Gessellschaft; Heidelberg Institute for Energy and Environmental Research; the DLR (German Center for Aerospace Technology); and the Westphalian Wilhelms University, Münster. The German Government initiated the fleet-test project.
VW is looking at a possible date for a production version of the TwinDrive of around 2013.