|Audi’s e-gas plant. Click to enlarge.|
The Audi e-gas plant, which can convert 6MW of input power, utilizes renewable electricity for electrolysis to produce oxygen and hydrogen. Because there is not yet a widespread hydrogen infrastructure, the hydrogen is reacted with CO2 in a methanation unit to generate renewable synthetic methane, or Audi e-gas. The e-gas is virtually identical to fossil natural gas and will be distributed via an existing infrastructure—the German natural gas network—to the CNG filling stations beginning in Germany in fall 2013.
|Components of the e-gas plant. Click to enlarge.|
The Audi e-gas plant will produce about 1,000 metric tons of e-gas per year, chemically binding some 2,800 metric tons of CO2. This roughly corresponds to the amount that a forest of more than 220,000 beech trees absorbs in one year. Water and oxygen are the only by-products.
Audi built the e-gas plant in collaboration with the plant construction specialist ETOGAS GmbH (formerly SolarFuel) (earlier post) and its project partner MT-BioMethan GmbH on a 4,100 m2 (44,132 sq ft) plot of land owned by EWE AG. Ground was broken in September 2012, and the topping-out ceremony was celebrated in December.
The efficient use of energy flows is the top priority in the production sequence of the plant. The waste heat given off during methanation is used as process energy in the adjacent biogas plant, significantly increasing overall efficiency. In return, this plant supplies the highly concentrated CO2 required as a basic building block for the e-gas. This CO2 thus serves as a raw material and is not emitted to the atmosphere.
It is anticipated that the e-gas from Werlte will power 1,500 new Audi A3 Sportback g-tron vehicles for 15,000 kilometers (9,321 miles) of CO2-neutral driving every year. The 1.4 TFSI in the five-door model can burn natural gas, biomethane and Audi e-gas; with its bivalent design it can also use gasoline. This gives it a total range of some 1,300 kilometers (808 miles).
Customers can order a quota of e-gas when they purchase the car. This enables them to take part in an accounting process that ensures that the amount of gas that they put in their vehicle at the natural gas filling station is supplied to the grid by the Audi e-gas plant. Payment and billing is handled via the Audi e-gas refueling card.
The Audi A3 Sportback g-tron, which is scheduled for launch late this year, consumes on average less than 3.5 kg (7.72 lb) e-gas per 100 kilometers (62.14 miles). CO2 tailpipe emissions are less than 95 grams per km (153 g/mile) in the NEDC. Driving with Audi e-gas is climate-neutral, since the CO2 generated when the vehicle is driven had been bound previously during the production of the e-gas.
Even in a comprehensive wheel-to-well analysis that includes the construction and operation of the e-gas plant and the wind turbines, CO2 emissions are just 20 grams per kilometer (32 g/mile). The groundbreaking environmental footprint was recently certified by TÜV Nord.
Audi notes that its e-gas project transcends the needs of the automobile industry and shows how large amounts of green electricity can be stored efficiently and independently of location by transforming it into methane gas and storing it in the natural gas network.
The e-gas project is part of Audi’s comprehensive e-fuels strategy. In parallel with the e-gas plant in Werlte, Audi also operates a research facility in Hobbs, New Mexico, USA, for the production of e-ethanol and e-diesel in collaboration with Joule. At this facility, microorganisms use water (brackish, salt or wastewater) sunlight and carbon dioxide to produce high-purity fuels. The strategic goal of these projects is to use CO2 as a raw material for fuels and thus improve the overall footprint substantially. The e-fuels strategy is an important pillar of Audi’s sustainability initiative.