Audi A3 g-tron
Audi’s other ‘production’ vehicle was the A3 g-tron dual-fuel vehicle. However, this vehicle represents more than just a car – the project involves an entire infrastructure aiming for a near-zero carbon footprint for the life cycle of the car.
    Audi A3 g-tron. Click image to enlarge |
The car itself can burn natural gas stored in two pressurized fuel cells under the trunk. To minimize the weight of the fuel tanks (27 kg apiece), Audi used an inner layer of an impermeable lightweight plastic reinforced by a layer of that lightweight carbon-fibre reinforced plastics (CFRP) used extensively in the R18 e-tron racecar and its predecessors and glass-fibre reinforced plastic (GFRP) for the outer shell. They occupy the space vacated by ditching the spare tire, but I’m pretty sure Audi will provide roadside assistance to owners of this rather experimental vehicle. The tanks each hold 7.2 kg of compressed natural gas apiece, good for a range of 400 km.
If the owner cannot find a CNG filling station before the compressed natural gas (CNG) is exhausted, it also has a reserve gasoline tank that extends the range by 900 km for a total range of up to 1,300 km, about the same as Audi’s frugal TDIs. The modified 1.4L turbocharged engine is rated at 110 hp and 148 lb-ft of torque whether burning natural gas or under gasoline power.
We drove the A3 g-tron around Berlin, circling by some famous landmarks and through the urban core, and guess what? It drives pretty much like a regular A3. That’s a good thing, what with the fine steering and all the subtle vibrations and ambient noise of a direct-injected internal combustion engine. While power is down significantly from the 200-hp 2.0TFSI we’re used to here in North America, that 148 lb-ft of torque is enough for low-speed, in-town maneuvering and scooting, but the lack of freeways on our drive route were no doubt calculated to avoid running out of steam – it takes “less than 11 seconds” to hit 100 km/h, so it might not live up to Audi’s sporting image on our high-speed highways, though I’m sure some healthy exercising of Audi’s fine manual transmission isn’t much of a penalty in my books.
However, dial the smug-meter up to 11, because when burning natural gas, the A3 g-tron is effectively carbon neutral. But wait. Even while burning far cleaner natural gas (at a rate of 3.5 kg/100 km – no idea how good that is relative to gasoline ratings) the A3 g-tron still emits 95 g/100 km of carbon dioxide into the air – so how is that possible?
Well, Audi has built the world’s first industrial scale plant that produces methane from waste carbon dioxide and, in theory, renewable windmill-generated electricity. You see, methane can be produced by bonding hydrogen molecules to readily available carbon dioxide (CO2). The hydrogen for Audi’s “e-gas project” is derived from water, using electrolysis (running a current through water will break it down into its component atoms of oxygen and hydrogen) powered by the electricity wired in from the windmills. It’s all a little magic-y, although if you want to delve deep into the science of it, detailed info is available at Audi Future Lab. There are also Audi wagons sliding around in the snow and ice and Le Mans race cars if that’s more your thing…
