by "bhtooefr" (bhtooefr)
Published 11/09/2017 at 05:41
by "bhtooefr" (bhtooefr)
Published 11/09/2017 at 05:41
Tags: audi
; volkswagen
; tdi
; renewable energy
; hydrogen
; electric vehicles
STARS: 2
So, Audi’s apparently continuing research into their Rube Goldbergian e-diesel experiments , which attempt to make synthetic renewable diesel fuel.
This is, in a word, silly. None of this is cost-effective, for starters - electrolytic hydrogen production and Fischer-Tropsch synthesis are both rather expensive. And then, there’s the efficiency problems - practical efficiency of the electrolysis step is in the 50-75% ballpark, Fischer-Tropsch is AFAIK in the 25-50% efficiency ballpark...
Not to mention, this does almost nothing about the emissions impact of diesel combustion - did nobody at Audi get the memo that they killed diesel?
So, I decided to fix Audi’s process for them.
Much better.
"duurtlang" (duurtlang)
11/09/2017 at 05:55, STARS: 0
Not to mention, this does almost nothing about the emissions impact of diesel combustion - did nobody at Audi get the memo that they killed diesel?
It is supposedly close to CO2 neutral, so it does impact greenhouse gas emissions. If it impacts smog related gasses I’m not so sure, but the main issue there is Nitrogen Oxide (NOx) based and I’m not seeing any Nitrogen in that image.
Anyway, the advantage of this fossil diesel alternative is that the infrastructure, technology (excluding chemical synthesis) and the vehicles are already there. This isn’t true for electric vehicles. If they can make this so called e-diesel cost effective is up to them, but if they were not at least somewhat confident they can make it work they wouldn’t pump money into the research.
"bhtooefr" (bhtooefr)
11/09/2017 at 06:13, STARS: 1
Point on CO2 near-neutrality. (I was thinking criteria pollutants, not global warming potential.)
NOx, however, is a result of high temperature combustion with air (which is mostly nitrogen) as the source of oxidizer, and excess oxygen in the cylinder (which is guaranteed to happen in a diesel) - under high temperature, these two reactions happen:
N 2 + O 2 2NO
N 2 + 2O 2 2NO 2
This is actually why lean burn technology for gasoline engines is nearly dead - lean burn, unless you can keep the temperatures very low (as in HCCI engines), means NOx. Diesels have to lean burn due to the poor atomization of their fuel, though, and the resulting smoke that would happen if they weren’t lean burning.
There is actually some potential for criteria pollutant emissions reduction (at least before the aftertreatment systems), from this fuel, though - Fischer-Tropsch synthesis provides much better control of the fuel’s properties than traditional refining, and there’s no sulfur to remove, so particulate matter emissions would be reduced.
"duurtlang" (duurtlang)
11/09/2017 at 06:16, STARS: 0
with air (which is mostly nitrogen)
Damnit, how could I overlook this most obvious fact? You’re right.
"pip bip - choose Corrour" (hhgttg69)
11/09/2017 at 06:31, STARS: 1
VW/Audi/Skoda/Seat need to ditch diesel completely.
"Cé hé sin" (michael-m-mouse)
11/09/2017 at 06:38, STARS: 0
The death of diesel is a long way off - despite all you hear about buyers turning away from it more than 60pc of cars sold where I am are diesel and more than 70pc of VWs.
"Cé hé sin" (michael-m-mouse)
11/09/2017 at 06:41, STARS: 0
Why? Buyers keep buying. About 70pc of VWs sold here are diesel and that figure has only dropped slightly in the past few years.
"pip bip - choose Corrour" (hhgttg69)
11/09/2017 at 06:44, STARS: 1
they can’t be trusted to do the right thing.
"bhtooefr" (bhtooefr)
11/09/2017 at 06:48, STARS: 0
What about governments banning it, though? And, actual enforcement of the emissions standards through Euro 6c’s phasing in of WLTP and RDE making it impractical for anything but higher-end cars?
"Aaron M - MasoFiST" (amarks563)
11/09/2017 at 07:54, STARS: 2
I started my energy career looking at carbon capture and storage. It’s the same sort of thing, an attempt to preserve current infrastructure and value chains (and in doing so, keep money going to the same people). The problem that inevitably arises is that the research usually is initiated when there looks to be a serious cost gap...and by the time it’s over, said cost gap no longer exists. Carbon capture and storage was interesting when wind and solar were expensive, but now that they’re the cheapest form of bulk energy there’s nothing you can do to make it make sense..
At the very least, synthetic liquids have their roots in old and fairly robust technology, but you’re still right: the cost of converting CO2 and hydrogen into a liquid fuel is incredibly high, and by the time it can be done at scale, the electric car problems it purports to solve will have already been solved by battery manufacturers.
"Cé hé sin" (michael-m-mouse)
11/09/2017 at 08:39, STARS: 0
True, but bans are at the moment mainly proposed for urban areas and are usually some considerable time in the future. There are still plenty of diesel users who won’t be affected by bans for some considerable time - off road, rail, marine, industrial. These will reduce over time but there’s still going to be a (diminishing) demand for diesel for decades to come.
"Spoon II" (Spoon_II)
11/09/2017 at 12:29, STARS: 0
This reminds me of the Navy system that was developed to turn sea water into jet fuel.
"Spoon II" (Spoon_II)
11/09/2017 at 12:30, STARS: 1
You have to take into consideration more commercial vehicles too, like semi trucks. It’s unlikely that those will be banned from using diesel, or that the majority of them will be switched to some other fuel in the near future.