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Research facility in Dresden produces first batch of Audi e-diesel; sunfire’s power-to-liquid technology

A pilot plant in Dresden has started production of the synthetic fuel Audi e-diesel using water, CO2 and green power—i.e., power-to-liquid (PtL). After a commissioning phase of just four months, the research facility in Dresden started producing its first batches of high‑quality diesel fuel a few days ago. (Earlier post.)

The energy technology company sunfire is Audi’s project partner and the plant operator. 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.

To demonstrate its suitability for everyday use, Federal Minister of Education and Research Prof. Dr. Johanna Wanka put the first five liters into her official car, an Audi A8 3.0 TDI quattro.

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.

—Reiner Mangold, Head of Sustainable Product Development at Audi

Production of Audi e‑diesel involves a series of steps:

  • Water heated to form steam is broken down into hydrogen and oxygen by means of high-temperature electrolysis. This process, involving a temperature in excess of 800 degrees Celsius, is more efficient than conventional techniques because of heat recovery. High-temperature electrolysis is that it can be used dynamically to stabilize the grid when production of green power peaks.

  • The hydrogen reacts with the CO2 in synthesis reactors under pressure and at high temperature. The reaction product, known as blue crude, is a liquid made from long‑chain hydrocarbon compounds. The efficiency of the overall process—from renewable power to liquid hydrocarbon—is around 70%.

  • 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 sulfur 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.

Sunfire 2
Two cartoons of the basic sunfire concept and process. PtL = Power-to-Liquids. Source: sunfire. Click to enlarge.

The Federal Ministry of Education and Research is supporting the sunfire project, which started in May 2012. Construction work on the facility in Dresden‑Reick kicked off in July 2013 and the plant was commissioned on 14 November 2014. The plant is set to produce more than 3,000 liters (792.5 gallons US) of Audi e‑diesel over the coming months. Audi is sunfire’s exclusive partner in the automotive sector.

In addition to 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; drivers of the Audi A3 Sportback g‑tron can fill up on it using a special fuel card. 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.



How clean does it burn when used in an ICE?

Are we using clean Solar and Wind Power to produce polluting liquid fuel?

If so, would it be wiser to produce H2 and use it in FCEVs?


HarveyD - Currently, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming or partial oxidation of methane and coal gasification with only a small quantity by other routes such as biomass gasification or electrolysis of water..... Wiser???
Do you work for the oil companies??


Not one single word about COST.

I'll bet dollars to doughnuts that if the public saw just what the electric power input alone for a liter of this stuff cost at wind or solar FIT rates, the Energiewende would be history after the very next election.

Henry Gibson

Buy Sodium Sulphur batteries from NGK, Zebra batteries from FZSonick or Durathon batteries from USA general electric and use the electricity for electric vehicles or trains and the mechanical to mechanical efficiency will be much higher; as much as ten times higher. Diesel engines in automobiles are seldom as high as 25 percent. The value 0.7 times 0.25 gives 0.18 or less than 20 percent of the windturbine energy is used to move the vehicle in the best case. A plug in hybrid vehicle at the base of the tower might get even 90 percent of the energy to the wheels; at a far distance it still can be 70 percent. Buy land in foreign countries or islands where oil plantations are destroying natural forests and install CANDU reactors from Canada in less than 4 years and convert all of the electricity to BLUE Diesel with only a few acres of land. Lots of heat is available for very high temperature electrolysis, but perhaps magnesium should be extracted from the ocean instead. Hydrogen is not the only fuel used to make electricity; billions of zink operated cells are sold every year. Magnesium, Sodium, Zink and Calcium can be used in cells of special type. Someone, much like myself, can invent a process to get very high temperatures from the cooling water of CANDU or any other reactor to do the direct production of hydrogen with limited electrical input. I also discovered high temperature electrolysis in 1970.

CANDU reactors can use used fuel rods from light water reactors to produce energy and mix it with Thorium for even more energy or even a continuous use of thorium with no more uranium or plutonium input. Reactors are known and others can be invented to use all of the uranium ever mined including used fuel rods and depleted uranium with very low percentages of U235 from enrichment plants and supply all electricity to the USA for the next 100 years without mining another pound of uranium. But also eliminating most of the present long term nuclear "wastes" and obtaining energy from them.

Because they contain long lived radioactive potassium since the creation of the earth, every pound of bananas could be considered radioactive waste. One hundred pounds of them give off about 40,000 gamma rays and 40,000 beta rays every second as do most adult humans. Every good food contains potassium, but sugar does not. However Sugar or Ethanol that is not radioactive is umlawful to sell in the USA as food because they are made from fossil fuels which have very very low radioactivity. ..HG..


The cost of the electricity is almost irrelevant, because it is only excess electricity that will be used.
Whether future electricity will be nuclear, wind or solar, there will be times of high supply and low demand. Now already, many wind turbines are turned off because of oversupply.

Obviously, best would be using batteries, second best would be hydrogen.
But in the real world there will be many ICE's around for decades, and fossil fuel burning planes for much longer.
if "waste" electricit can be turned into those fuels, that's great.

The question is not whether diesel engines are sound. The question is where should the fuel we burn so far come from: made in Germany from excess power, or made by dictatorships from fossils.


....or from local shales and neighboring tar sands?

The cost of the electricity is almost irrelevant, because it is only excess electricity that will be used.

If you assume that people will invest money to produce very much electricity they can't use and just give it away, you're not dealing well with reality.

in the real world there will be many ICE's around for decades

I rather doubt it.  How long did it take steam cars to disappear once the ICEV won the race for reliability and convenience?  Much less than 20 years, I bet.  If we get the 140 Wh/kg aluminum ion battery that charges in 1 minute, I expect that it will take over laptops and smaller devices in 2 years (imagine getting 2 hours of laptop power in 6 minutes), completely take over hybrid cars in the next model cycle (3 years or less) and EVs in about the same amount of time.  Once an EV can charge in 10 minutes or less there will be no perceived advantage to ICEVs and the market for them will collapse.

The question is where should the fuel we burn so far come from

Germany has ocean front and can harvest uranium from seawater as easily as anyone else.  Nuclear power can supply all the energy Germany needs, without relying on anyone or anything else.


It would be interesting to know at what electricity cost this is thought to be feasible, at least. Presumably not just at negative prices.

E-P What is the cost of harvesting uranium from seawater?

Roger Pham

>>>>"Not one single word about COST"

The "Sunfire2" diagram states the cost to be 1 Euro per liter, or roughly $4 per gallon US. Not quite as yet cost-competitive with petroleum, because if adding profit and tax, would be priced about $6 per gallon.

Hydrogen using electricity rate at 5 cents per kWh and 53 kWh per kg would have an energy cost of $2.65. Adding $0.50 facility cost would raise the cost per kg to be $3.12 per kg. A FCEV is twice as efficient as an ICEV, so, if this H2 will be sold at $4.5 per kg when adding profit and taxes, then it would be equivalent to gasoline at $2.25 per gallon.

FCEV can fulfill the ZEV mandate while Diesel vehicles cannot.

Eventually, when the majority of summer power demands will be satisfied by RE, then there will be a major surplus of power in Springs and Falls. In Southern States, summer power consumption may be as high as 3x that of springs and falls. If we are going to stop using fossil fuels as much as possible with competitively priced solar, wind, and even NUCLEAR power, then eventually, we will need to install enough solar, wind and nuclear energy to cover the heavy consumption of summers.
Then, we will have a lot of excess electricity generation in falls and springs when the weather is mild and no A/C nor heating required. Most lighting and TV's by then will be by LED, with 1/10 th the consumption of incandescent bulbs and <1/2 that of fluorescent bulbs of today. PC's will become more and more power efficient with miniaturization.

From these surplus electricity of Springs and Falls, we will then be able make H2 or synthetic diesel fuel for transportation use out of the seasonal surplus of RE, because NG may still remain too cheap for "power to gas" replacement with H2 for home heating and home power generation, while H2 for transportation is already competitive with petroleum.



"If you assume that people will invest money to produce very much electricity they can't use and just give it away, you're not dealing well with reality."

This is how it is almost everywhere. Every nuclear power plant produces electricity at a continuous rate, day and night in order to be able to cover peak demand (could be lowered with the seasons, but not overnight).
All produced electricity not used is lost.
wind turbines are often shut down because of excess.
solar and wind will become cheaper and cheaper for years to come, so it is very economical to build "overcapacity" of solar/wind to replace fossil electricity as much as possible, and the excess power that will be produced (and is already produced) will be vertually free.

it's comparable with "free" computing power you can donate when you pc is idle.
you did never buy a computer to give free computing power to SETI, but you want the power when you need it and sell it to the highest bidder when you don't need it.

I agree with more nuclear, but you can't drive a car on uranium or thorium. Nukes also have lots of "spare" electricity you can use to make fuels.
Still, I am confident solar will be (and in many places is already) much cheaper than nuclear within 10 years (= the minimal time it takes to build a new nuke).


Storing excess RE may be a challenge now but lower cost solutions will be found in the not too distant future.

Transforming excess electricity into liquid fuel for airplanes and other specific uses will become a reality.

Transformation to H2 for FCEVs and home/industrial uses is a cleaner way to do it. It would reduce pollution and GHG.

This is how it is almost everywhere.

I'm aware of pumped-storage systems which use overnight excess power (there's one maybe 100 miles from me), and a CAES unit somewhere down in Alabama or the like, but that power is sold.  I'm aware of nobody giving it away, especially not during their peaks of production.

wind turbines are often shut down because of excess.

Yes, about that.  Excess wind power could easily substitute for fuel in industrial process heat.  Iowa has a bunch of ethanol operations, which all use heat to mash the grain and distill the product.  Excess wind power could be dumped to heaters there, substituting for natural gas and avoiding the need for curtailment.  Why isn't this happening?

solar and wind will become cheaper and cheaper for years to come

It doesn't matter how cheaply you can make something if you get zero or negative value from it.  Schalk Cloete has calculated that the value of intermittent RE falls to zero at about 27% penetration on the grid.  After that, it's negative due to the costs of integration.

I agree with more nuclear, but you can't drive a car on uranium or thorium.

27% of the electric power generated in my state is nuclear, and about 2/3 of my driving is powered by electricity.  I am driving my car on uranium, about 1 mile out of 5.  If I lived in Ontario that figure would be closer to 1 out of 2.


the aluminium-ion battery from Stanford has an (estimated) energy density of just 40 wh/kg. You can check it in the Nature paper.
I think we will be stuck with Litihium chemistries for a while...


Peskanov, the part of the Nature paper outside the paywall says 70 mAh/g and a nominal 2 volts or so.  That's about 140 Wh/kg.  If you have access to the full paper, please quote the figures which show how that is in error.


With few exceptions, such as variable over equipped Hydro with large water reservoirs, most power generation facilities DO NOT supply/sell energy close to their Name Plate capability because demand varies too quickly from close to 95% to as low as 15% on a daily and/or seasonal basis.

Most of todays power generating facilities are built to meet 110% to 120% of peak demands and huge energy (unused) surpluses exist on daily and seasonal basis. Many producers offer those surpluses below cost because any price is better than nothing.

H2 producers could get base load energy and RE at very low price (below cost) during surplus hours, specially if they could return energy to the network (for short periods) during peak demands. H2 two-way converters could that.

Yordan Georgiev

Well for the US citizens out there EU looks like clumsy giant yet there is a clear strategy:

that is a single Energy Market , which WILL
promote lower electricity prices. Well how ?!

Now what is the percentage of taxes from the fossil fuels in EU ?!
from around 40% till 80%

This is the reason why Europe's economies do not get huge pushes from cheaper oil prices, it makes them also much more resilient when the prices are higher ...

How easy would it be for Europe to start promoting cost effective technology based scalable transport fuels production solely on tax policy ?! After taking into consideration geopolitics with Russia, Saudis and Iran ... Well it makes sense ...

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