Audi claims it has
taken a major step in the development of new, CO2-neutral fuels.
A pilot plant in Dresden, Germany, has started
production of the synthetic fuel Audi e-diesel.
After a commissioning phase of four months,
the research facility in Dresden started producing its first batches of
high-quality diesel fuel a few days ago.
The energy technology corporation Sunfire is
Audi's project partner and the plant operator.
It operates according to the power-to-liquid
(PtL) principle and uses green power to produce a liquid fuel. The only raw
materials needed are water and carbon dioxide.
The CO2 used is currently supplied by a
biogas facility.
In addition, initially a portion of the
CO2 needed is extracted from the ambient air by means of direct air
capturing, a technology of Audi's Zurich-based partner Climeworks.
Reiner Mangold, head of sustainable product development
at Audi, sees Audi e-diesel and Audi e-fuels in general as an important
component that complements electric mobility.
"In developing Audi e-diesel we are
promoting another fuel based on CO2 that will allow long-distance mobility
with virtually no impact on the climate. Using CO2 as a raw material
represents an opportunity not just for the automotive industry in Germany, but
also to transfer the principle to other sectors and countries," he said.
Production of Audi e-diesel involves various
steps: First, water heated up to form steam is broken down into hydrogen and
oxygen by means of high-temperature electrolysis.
This process, involving a temperature of over
800°C, is claimed to be more efficient than conventional techniques because of
heat recovery, for example. Another special feature of high-temperature
electrolysis is that it can be used dynamically, to stabilise the grid when
production of green power peaks.
In two further steps, the hydrogen reacts with
the CO2 in synthesis reactors, again under pressure and at high
temperature. The reaction product is a liquid made from long-chain hydrocarbon
compounds, known as blue crude. The efficiency of the overall process - from
renewable power to liquid hydrocarbon - is very high at around 70 per cent.
Similarly to a fossil crude oil, blue crude
can be refined to yield the end product Audi e-diesel. This synthetic fuel is
free from sulphur and aromatic hydrocarbons, and its high cetane number means
it is readily ignitable. As lab tests conducted at Audi have shown, it is
suitable for admixing with fossil diesel or, prospectively, for use as a fuel
in its own right.
Construction work on the facility in
Dresden-Reick began in July 2013 and the plant was commissioned on November 14,
2014.
The plant is set to produce over 3,000 litres
of Audi e-diesel over the coming months. Audi is Sunfire's exclusive partner in
the automotive sector.
Over and above the partnership with Sunfire,
Audi has been active in the development of CO2-neutral fuels - Audi e-fuels -
since 2009. The Audi e-gas plant in Werlte, Lower Saxony, already produces Audi
e-gas (synthetic methane) in a comparable manner to power the Audi A3 Sportback
g-tron, which is available in countries in which a suitable fuelling
infrastructure exists.
Audi is also conducting joint research into
the synthetic manufacture of Audi e-gasoline with Global Bioenergies, of
France.
In a further project, Audi has joined forces
with the US company Joule, which uses microorganisms to produce the synthetic
fuels Audi e-diesel and Audi e-ethanol.
Audi is of course part of Volkswagen AG which
also has been working on synthetic fuels.
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