Audi opened a new 6 MW power-to-gas facility in Germany this week, making it the first automaker to develop a chain of sustainable energy carriers.
The plant, located in the Lower Saxony city of Wertle, uses green electricity, water and carbon dioxide to create hydrogen and a synthetic methane known as Audi e-gas, which it will begin distributing to compressed natural gas (CNG) filling stations this fall.
The e-gas plant utilizes a two-step process: electrolysis and methanation. First, the plant uses surplus green electricity to break water down into oxygen and hydrogen in three electrolyzers. While the hydrogen could one day power fuel-cell vehicles, in the absence of an area-wide infrastructure, a second process step is carried out directly: methanation. The hydrogen is combined with carbon dioxide (CO2) to produce synthetic methane, or Audi e-gas.
The Audi e-gas project demonstrates 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 largest public energy storage system in Germany.
Audi plans to begin distributing the gas, which is virtually identical to fossil natural gas, via the existing German natural gas network to compressed natural gas (CNG) filling stations this fall.
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. According to Audi, this roughly corresponds to the amount of CO2 that a forest of over 220,000 beech trees absorbs in one year. Water and oxygen are the only by-products.
The Ingolstadt-based automaker built the e-gas plant in collaboration with the plant construction specialist ETOGAS GmbH (formerly SolarFuel) and MT-BioMethan GmbH on land owned by German energy company EWE AG.
Audi said the efficient use of energy flows was the top priority in the plants production sequence: The waste heat given off during methanation is used as process energy in the adjacent biogas plant, significantly increasing overall efficiency. In return, the biogas plant supplies the highly concentrated CO2 required as a basic building block for e-gas. This CO2 thus serves as a raw material and is not emitted to the atmosphere.
The company is launching its new Audi A3 Sportback g-tron vehicle later this year and says its e-gas can power 1,500 of the cars for 15,000 kilometers of CO2-neutral driving a year.
In addition to the Werlte plant, Audi also operates a research facility in the U.S. state of New Mexico for the production of e-ethanol and e-diesel in collaboration with Joule.
"Audi is taking a giant step toward the mobility of the future today," said Heinz Hollerweger, head of Audi’s Total Vehicle Development. "Audi is the only manufacturer worldwide with such innovative technology. Research into synthetic, environment-friendly fuels is the core of our vigorous e-fuels strategy."
Reiner Mangold, head of the company’s Sustainable Product Development division, added, "The power-to-gas facility we built in Werlte can become a beacon project for the entire energy revolution, far beyond the boundaries of our company."
ETOGAS CEO Karl Maria Gruenauer said the inauguration of the 6 MW plant marked the beginning of "the commercial application of this new power storage technology. In the coming years, we will provide the market with plants of up to 20 MW of electrical power input and reduce investment costs to the necessary level for energy management applications."