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Audi is jumping on the CNG bandwagon with a natural gas version of its A3 hatchback.
Named A3 Sportback g-tron by Audi, the natural gas vehicle showcases what Audi qualifies as state-of-the-art CNG drive technology, starting with the fuel storage. The vehicle has two tanks, located under the luggage compartment floor. Each can hold seven kilograms (15.43 pounds) of CNG.
In tune with the ultra-lightweight construction concept, each tank weighs 27 kilograms (59.52 pounds) less than its conventional counterpart.
The tanks are made of a new type of matrix. The inner layer consists of gas-impermeable polyamide polymer, while a second layer of carbon fiber-reinforced polymer (CFRP) gives the tank its high strength; a third layer of glass fiber reinforced polymer (GFRP) provides rugged protection against damage from the outside. High-strength epoxy resin is used to bind the fiber reinforced materials.
Another technical highlight of the Audi A3 Sportback g-tron is its electronic gas pressure regulator. This compact and lightweight component reduces the high pressure of the gas flowing from the cylinders in two stages.
This ensures that the right pressure is always present in the gas rail and at the injector valves – low pressure (five bar) for efficient driving in the lower speed range, and higher (nine bar) when the driver calls for more power and torque.
If the pressure in the tank drops below ten bar, the engine management system automatically switches over to gasoline operation.
The Audi A3 Sportback g-tron has identical performance whether running on CNG or gasoline.
CNG provides a range – based on standard fuel consumption – of around 400 km (248.55 miles), with gasoline providing another 900 km (559.23 miles) if necessary; the total range is approximately on a par with an Audi TDI.
Two displays in the instrument cluster provide the driver with up-to-date information on the fuel level in each of the tanks. The driver information system also displays the current fuel consumption based on the particular operating mode.
The CNG and gasoline filler necks are placed under a common fuel flap. After refueling, and whenever it is very cold, the engine is started with gasoline initially, then is switched over to natural gas as quickly as possible.
The engine is based on the new 1.4 TFSI. Key modifications relate to the cylinder head, turbocharging, injection system, and the catalytic converter.
Developing 110 horsepower, the Audi A3 Sportback g-tron has a top speed of 190 km/h (118.06 mph), with 0 to 100 km/h (0 – 62 mph) taking eleven seconds.
The A3 Sportback g-tron will be available at the end of the year.
Audi producing its own CNG
With the e-gas project, Audi said it is the first automobile manufacturer to develop an entire chain of sustainable energy carriers.
The start of the chain has electricity produced from renewable energy sources; the end products are hydrogen and the synthetic Audi e-gas, which can be used in the same way as CNG.
According to Audi, construction of the world’s first industrial plant to produce synthetic methane (e-gas) from CO2 and renewable electricity is almost complete in Werlte (Emsland district of Lower Saxony), Germany.
The Audi e-gas plant uses the renewable electricity in the first stage for electrolysis – splitting water into oxygen and hydrogen (Audi e-hydrogen), which could one day power fuel-cell vehicles.
Because there is not yet a widespread hydrogen infrastructure, however, the hydrogen is then reacted with CO2 in a methanation plant to produce renewable synthetic methane, or Audi e-gas.
Chemically speaking, this e-gas is identical to fossil-based natural gas. As such, it can be distributed to CNG stations via the natural-gas network.
The CO2 used in Audi’s e-gas plant is a waste product from a nearby biogas plant, operated by power utility EWE. The CO2, which would otherwise pollute the atmosphere, is chemically bonded into the fuel at the Audi e-gas plant.
The e-gas plant will annually produce about 1,000 metric tons of e-gas and will chemically bind some 2,800 metric tons of CO2. This corresponds roughly to the amount of CO2 that 224,000 beech trees absorb in a year.
The CO2-neutral e-gas from Werlte will be enough to power 1,500 new Audi A3 Sportback g-tron vehicles over a distance of15,000 kilometers (9,320.57 miles) every year.