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Audi opens power-to-gas facility in Werlte/Emsland; e-gas from water, green electricity and CO2

Audi’s e-gas plant. Click to enlarge.

Audi has opened its e-gas plant in Werlte, making it the first automobile manufacturer to develop a chain of sustainable energy carriers. (Earlier post.)

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.



Alain said:
'We even have to include another fact, and that is that Germany imports most of its fossil fuels, so even if the price is somewhat higher for wind energy than for fossil energy, macro-economically it is ultimately cheaper for the Germans to produce wind-energy than coal-energy, since the extra cost for wind-energy is more than compensated by the the fact that the money remains in the local economy, instead of disappearing to a foreign fuel supplier. '

Your ideas of economics are somewhat singular, and omit generations of study on the division of labour and the efficient allocation of resources.


What I don't understand is how Germany is going to pay for the capital cost of these renewable projects when the product they sell (electricty) is essentially zero at the time they sell it.

This is already a problem for Solar PV during the day in summer in Germany.

There is a huge difference between Energy and Power. In electricity generation people pay for Power not Energy.

I thought this was all obvious...


The efficiency of an internal combustion engine is only 20% - 80% of the energy in the fuel is wasted as heat - so why have internal combustion vehicles been so successful? The fact is, conservation of energy and thermodynamic calculations are highly complex topics that can be easily manipulated by those seeking to promote their economic interests - so take all such claims (as seen above) with a grain of salt.

In reality, it should be possible to use large-scale renewable energy to capture CO2 from the atmosphere while simultaneously producing hydrogen from water - then, using the same type of Fischer-Tropsch (or Haber-Bosch, same general idea, but with N2 as substrate instead of CO2/CO) chemistry developed in Germany in the early 20th century, one could make tons and tons of renewable hydrocarbon fuel.

Yes, it would be a major engineering effort on the scale of the Manhattan Project, but the current fossil fuel infrastructure cost something like $10 trillion to build, so it's not as if it couldn't be done.


People questioning the expense of e-gas are right to do so.  The process efficiency is probably well under 50%, and the capital costs will have to be added to that.  Further, unless there is a substantial amount of electrolyzer overcapacity and storage for H2, there is no way to use this plant for demand-side management to buffer the variable flows of power from wind and solar generators.  If it requires a continuous 6 MW feed, it becomes part of the base-load demand problem (an anti-solution).

If you're going to insist on using e-gas, the best way is probably in an EREV using a solid-oxide fuel cell to use the methane.  You get much higher efficiency using the gas, plus the first X many miles of each trip can be powered directly by electricity at 3x or more the efficiency of e-gas.  The only way this makes any sense at all is in combination with electric propulsion.

Note:  the reaction is CO2 + 4 H2 -> CH4 + 2 H2O
H2 has a heat of combustion of 285.8 kJ/mol
CH4 has a heat of combustion of 802.34 kJ/mol
285.8*4 = 1143.2 kJ in, 802.34 kJ out.  70% efficient.

If the electrolyzer is 70% efficient, the net efficiency is 49%; burned in an ICE at 38% efficiency, you get 18.7% end-to-end (using 60% SOFC yields 29.4%).  This does not count energy costs in capturing, filtering, compressing and transporting the e-gas.  Losses in the electric grid are likely around 5%.


Alain wrote:

from an economic point of view, it is very hard to calculate the "cost" of the electricity, because they will use excess electricity when there is overproduction of wind energy.

It costs whatever you have to pay for it plus the externalized costs.  Under most regimes you pay the feed-in tariff.  The externalized costs are whatever it takes other generators to manage the variability.  IF and ONLY IF this e-gas plant is operated in DSM mode, those costs might be reduced... but I'm inclined to doubt that it will be.

There is only so much capital available (as in physical capital; printing presses can make "money" but not goods).  If you spend a lot of physical capital to power a few miles of travel via e-gas, you cannot use that same capital to power more miles in a more efficient way.  For instance:

6 MW(e) / 120 Wh/km = 50,000 km/hr
50,000 km/hr * 8760 hr/yr = 438 million km/yr

The expected yield from this plant will run 1,500 vehicles for 15,000 km/yr each, a total of 22.5 million km.  This is about 5% of what the same energy could produce using electric propulsion.

Alain, do you have enough physical capital to throw away 95% of your potential yield from RE?



This is a "Promotion campaign", "image building".
All brands have to be branded. Most car companies spend more money on marketing and branding than on R&D.
You could consider this "pilot project" as a marketing campaign. It builds the image of Audi and of the driver.

When you are going to do the same economic calculations to determine whether it is economically sound to spend tens of thousands of dollars on a large car battery, and calculate how many money you will make by saving gasoline, the conclusion will probably be that it is absolutely crazy. Likewise, what is the efficiency of buying an expensive "luxury car" compared to an "average car". How much money per driven trip will it cost extra in a luxury car ? You don't care, simply because you like driving a sexy car. It is not about saving gasoline, or cheap transport. It is about the image and the experience and people are willing to pay (a lot) for that.

As everyone seems to agree, it's all about the money. If Audi uses the "green image" to sell more cars, and buyers like the green image and are willing to pay for it, and green electricity suppliers are happy to sell there spare electricity at a higher price to audi than they would get elsewhere, then what's the problem ?

If any Audi-NG-driver prefers to buy cheaper "normal" NG, than they are free to do so. If they prefer to buy more expensive "synthetic NG", they are also.

It is absolutely true that you can use a worker only once, and if you use him in a useless plant, you can not use him somewhere else. However, the money spent on this plant is a money for "image building" and "branding". If it is not spent on the production of synthetic NG, it would be spent on a marketing campaign, or sponsoring a formula-1 race, or something like this.
Most of our GDP is not spent on clever engineering, but on marketing, branding, advertisment, ...

Again, and again, I completely agree that electric drive is much more energetically efficient and I would prefer it by far. But the economic reality seems to demonstrate that economically, it is at this moment and and that location in the world more sound driving on wind energy by burning renewable NG than on batteries.

One should see the four aspects separately : there is (1) a very sexy car on NG, there is (2) the possibility to produce synthetic NG, there is (3) a need to convince a customer to buy your products, (4) some customers who like to drive carbon-free NOW and are willing to pay some extra for this without sacrificing range.

It's a free market. If branding and advertisement money can pay for the large scale implementation of renewable NG, who would care ? (except for the genuine marketing industry)

Everything makes economic sense when taken those 4 together.

@ Davemart, considering "the division of labour and the efficient allocation of resources" : I agree completely, but there are certainly limitations on that. That's what the WTO-agreements are all about. Why would Europe bother on buying dirt-cheap Chinese solar panels at dumping prices, if only considering "efficient allocation on resources" ? Trade barriers and export subsidies are made exactly to prevent "efficient allocation on resources".

For instance, the economic power of China is largely because they sell whatever the can to other countries, but try to import as less as possible. The trick to do it is simply to keep their currency artificially cheap.

Kit P

“80% of the energy in the fuel is wasted as heat ”

It is only wasted if there is a use for it. The general problem with improving thermal efficiency is that improvements come at high cost and create new engineering problems,

“it should be possible ”

Of course it is possible but why would you do it. Since I work in nuclear power I am not the least bit worried about a time centuries from now when. Tiny South Korea is building 5 1400 MWe nukes as we speak. While South Korea is small they are a relatively large industrial power.

“it is economically sound to spend tens of thousands of dollars on a large car battery ”

Of course not! Just because BEV are a bad engineering choice does not make e-gas a good choice. Rent the movie Dumb and Dumber.

What is possible and costs nothing is just to drive less or car pool. What is very frustrating as an engineer is people who refuse to make simple personal choices but expect engineers to find solutions. When do find things like nuclear power they invent reasons to reject them.


IMO the simplest and most economical way to store excess electrical energy from intermittent renewable sources is to use it to heat well isolated liquids (water) in tanks, used for heating in winter with heat pump systems.
Apparently, as several people posted here in comments to a previous article, critical shortage of electricity occurs during cold winter days (and nights), when solar power is practically non-existent. But wind is in many places plentiful in winter, although intermittent. Intermittency is a non-issue for heating underground water tanks, that can keep heat for 3+ days, or much longer, when used with smart meters, that can turn on and off the water heaters instantly.
So wind power can be well matched with heat storage in winter.
If wind turbines are located close to heat tanks, then they could be connected directly via DC current cables, no need to synchronize turbine speed or do DC-AC conversion. Even the voltage regulation is not needed, just over-voltage prevention. By using (omnidirectional) vertical axis wind turbines, that can also work with high speed winds, would make things simpler and cheaper.


High efficiency energy storage is a short term challenge. It will be resolved within one or two decades.


If only we had 2 decades to get moving... we are more like 2 decades behind already.


Decades are relatively very short 'periods' of time.

By the end of the current one, e-storage units will have improved 2X to 4X or enough for practical EVs. Solid state 600+ Wh/Kg batteries should be mass produced by 2020.

By the end of the next decade, the majority of new cars will be EVs and many will be charging 'free' with home, very high (30% to 50%) efficiency, solar + storage system. Ultra quick charging (less than 10 minutes) public stations will progressively replace existing gas stations.

Japan, South Korea, China and USA will lead the way to electrified vehicles.

Wouldn't be surprised to see major Oilcos invest heavily into e-storage units, public charging stations and e-energy generation plants.

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