VW's Twin Drive Plug-In Hybrid

Automakers around the globe are betting on the future of electric powertrains for clean, efficient transportation. In Germany, where more than 13 percent of electricity is currently generated by local wind power, electric cars make sense on many levels. Germany is on track to provide wind power generation to 30 percent of the nation's electrical needs by 2020 and the addition of solar and hydro energy will further increase their use of renewable resources and move toward energy independence.

Not surprisingly, Volkswagen is ramping up to put electric drive cars on the road by as early as 2010. VW, the fourth largest automaker in the world, recently announced a fleet test program of 20 Golfs (Rabbits in the U.S.) with a dual powertrain system called TwinDrive. The design has both a gasoline engine and an electric motor for propulsion, but this is not a conventional gas-electric hybrid. TwinDrive is engineered to deliver extended range on the electric motor for city driving conditions in pure EV (electric vehicle) mode. In traditional parallel hybrid designs, the electric motor is integrated to compliment the gasoline engine. With Volkswagen's TwinDrive the internal combustion engine supplements the electric motor.

Volkswagen is testing both gasoline and diesel combustion engines with the TwinDrive system. In addition to overall fuel efficiency, VW's goal is zero emissions operation in congested and confined urban areas and city driving situations where these vehicles can have the greatest impact on the surrounding environment. Importantly, the TwinDrive Golf is said to have an electric only range of 50 kilometers, or 31 U.S. miles. That's plenty of EV range for around-town errands and shorter commutes.

In a sample round trip route from Potsdam, Germany to downtown Berlin and back - which VW cites as a fairly typical commute of 100 kilometers (62 miles) - the TwinDrive used just 8 kW hours of electricity and 2.5 liters (0.66 gallons) of fuel. That's about 94 mpg for the trip. Electricity prices vary by region, but at the current average rate 8 kW hours is roughly $0.75 worth of electricity.

These Golfs should be fun to drive and offer plenty of power to manage a wide range of driving situations. VW cites the tandem output of up to 130 kW of power, which translates into 174 horsepower. For comparison, the 2008 U.S. spec Rabbit with a 2.6-liter 5-cylinder produces 170 horsepower and is quite peppy. The Golf/Rabbit is a versatile, well-proven world car. As a five-door hatchback, it is adept at many missions in addition to the role of commuter and makes a great go-to vehicle for everyday use.

The TwinDrive Golf is said to be simple to operate with functions monitored on the large center console-mounted nav system screen. The instrument cluster is different, however. In place of a traditional tachometer, the car has a large power gauge that reads from "Off" to 125 kW of power, with the redline area starting above 75 kW. To monitor battery condition, there is a battery charge gauge alongside the fuel gauge.

Critical to the success of electric drive powertrains and the TwinDrive system is the development of lithium-ion battery technology. Volkswagen states that a prerequisite to electrify our transportation is the development of Li-ion batteries with high energy density, quick charging, and long life. It will utilize the TwinDrive test fleet to evaluate the latest advanced Li-ion technology in a large-scale study in real world conditions. Volkswagen is working with GAIA and Evonik/LiTec on the battery technology. The Golf's Li-ion battery is situated below the cargo floor in the rear hatch area, a location that helps optimize weight distribution in the front-wheel drive platform.

Volkswagen is teaming with E.ON, a German energy provider, for the infrastructure to operate the test fleet. 'Refueling' in this case involves plugging the TwinDrive into an electrical outlet. Public and private parking spaces, including parking structures, will be equipped with electric refueling stations, essentially power outlets, to make the most of the EV capability.

The fleet program is scheduled to run through 2012. Total cost of the program was not released, but VW has stated it is investing "double-digit" millions in advanced development of the electric drive vehicle technology. The German Federal Ministry for the Environment is partnering on the program and committing support of millions of euros for the study.

Is electric drive just around the corner? That reality seems closer every day.