A3 Sportback g-tron runs on Audi's own carbon-neutral e-gas
March 12, 2013
Set to up the eco-ante later this year is Audi’s new e-fueled g-tron 5-door hatchback. Carrying design elements and other familiar amenities from previous A3 outings, the new g-tron is similar in every way except the fuel option. But in this story, the car is only part of the eco-tale.
Powered by Audi’s CO2-neutral "e-gas," the g-tron sportback will incorporate CNG (compressed natural gas) as its primary motivational option. Produced in Werlte, Germany, the new fuel will be developed in the world's first power-to-gas plant built specifically for CNG production.
Cheaper than gasoline and easier on engine lubricants than gas engines, CNG has been shown to offer an eco-friendly tailpipe option relative to the dead dinosaur variants. Not without its detractors and problems, CNG has been gaining acceptance amongst select manufacturers for years. Consumer pickup, on the other hand, has been less than spectacular. The tron-of-g hopes to change the perception.
Audi’s engine of choice is the new 1.4 TFSI. With modifications to the upper head area, turbo-charging units, injection system and catalytic converter, the powerplant delivers a whopping 110 hp (81 kW) and 148 ft.lb (200 Nm) of torque. These numbers bring about a top speed of 118 mph (190 km/h), with 0 - 60 mph (0 - 100 km/h) times plodding in around the 11.0 second mark.
But performance isn’t what the dance is all about. Consuming a meager 3.5 kilograms per 100 km (7.7 lbs per 62 miles) of CNG, the g-tron provides an impressive range of 1,300 km (807 miles), emitting only 30 grams of CO2 per kilometer (48.28 g/mile) in the process. In gas mode, tailpipe stuff is only 95 grams per kilometer (152.89 g/mile).
According to Audi, the g-tron provides a total range equivalent to its turbo diesel alternative. To keep track of fuel statistics, twin displays in the center of the instrument cluster afford drivers complete fuel information on each of the tanks. The system also displays current fuel consumption based on operating mode.
To ensure gassy pressures of a natural sort are in line with driver demands, Audi has designed electronic gas pressure regulators into the system. Similar to gas injection systems, but with a twist, the CNG configuration requires minimum pressures to operate effectively. Working with pressures around 5 to 9 bar in two stages, the system maintains ideal conditions, but should tank pressures drop below 10 bar then the system automatically switches to gas mode. Audi proclaims the system "bivalent," which translates into roughly equivalent performances stats across both fuel offerings.
Two filler necks located under the common fuel flap provide filling needs. The g-tron’s engine is initially started with gasoline, then switched over to natural gas asap. Under cold conditions, the engine again starts with the gas then swaps over to CNG once optimal operating conditions exist.
The Audi’s two CNG tanks, located under the luggage compartment floor, are comprised of a new type of material matrix; an inner layer consists of a gas-impermeable polyamide polymer, while a second layer of carbon fiber-reinforced polymer gives the tank its strength, and a third layer provides external protection. Each tank has a capacity of 7 kg (15.43 lbs) of CNG at a maximum pressure of 200 bar.
What makes the g-tron project unique is not the car so much itself but the holistic energy chain Audi has developed. Electricity produced from renewable sources populates the front of the chain, while end products of hydrogen and Audi’s e-gas finish the cycle.
Opening this year, the Werlte-based Audi e-gas plant uses renewable electricity in the first stage for electrolysis – splitting water into oxygen and hydrogen, creating Audi’s e-hydrogen. This e-fuel, it is hoped, could one day be used to then motivate fuel-cell rides. But as hydrogen as mainstream is not a viable alternative, Audi takes the newly generated hydrogen, which is then reacted with CO2 in a methanation plant; the result, renewable synthetic methane, or Audi’s e-gas. Chemistry clever.
Until now, electricity could be generated from gas, but not vice versa. With Audi’s e-gas plant, however, the opportunity exists to take advantage of the natural gas network’s excess capacity – translating into a storage and transport system for excess electricity. According to Audi, the entire power industry could benefit from its e-gas project, as it addresses the issue of how to store large quantities of electricity produced from wind turbines and solar systems.
To further push the eco-argument, CO2 used in the production of Audi’s e-gas is a waste product from a nearby bio-gas plant. Audi’s e-gas plant is expected to produce about 1,000 metric tons (1,102 tons) of e-gas and chemically bind 2,800 metric tons (3,086 tons) of CO2 annually.
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