Anyone explain how this works in regards to the laws of thermodynamics?
A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
211–220 of 291 posts
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#212Earlier quoted context omitted.
> natural gas -> hydrogen and CO2 -> separate out CO2 -> geological CO2 storage. Everything I've seen about H2 tells me that electric cars are just better. Luckily for your theory, it's still possible to do what you want with electric cars - just carbon capture at electric power plants.
Maybe cars, but the weight of batteries is a problem for larger vehicles that need long range, like a bus, truck, or plane. For those hydrogen might be better.
There's a big difference between US, Canada or Australia, and say Europe regarding this. In Europe the majority of buses and trucks don't need to travel long distances. And as the population in Europe is generally much more dense soon there will be a local infrastructure of recharging stations available everywhere, so even those that need to cross long distances won't have a big problem recharging more often. The regulations in EU are really strict on bus and truck drivers, so they have to make a lot of stops and take regular breaks anyway (every 4.5 hours IIRC)
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#213Earlier quoted context omitted.
It’s not thermodynamically possible to recapture carbon from the air without using more energy than was obtained by burning it the first place.
Thermodynamically, no. But is that the question? We're a long way away from consuming so much energy we thermodynamically scorch the Earth, right? It seems like they want to know if you can be mostly carbon neutral and generate existing fuels. If that's the case, then if you have access to a cheap form of renewable energy -- huge amounts of geothermal, tidal, or solar -- you could generate a ton of something-like-gas…
As an aside, we're not that far from boiling the oceans at the current rate of growth in energy usage. Maybe 400 years, IIRC.
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#214Earlier quoted context omitted.
Hi Graycat, it actually may be easier to make fuel by mining air. We used to make fertilizer by mining guano and collecting animal droppings, but once Haber and Bosch figured out how to make ammonia from atmospheric N2, it just make more economic and practical sense. It's hard to mine oil, transport it, refine it, etc. Compare that to making it where and when you need it with no waste. I think it will be better.
As soon as PV is cheap enough, lots of fleets will convert to liquid anhydrous ammonia. Sure it's different than petrol/diesel, but it's already in wide use as a fertilizer and no technological breakthroughs are required to get it burning in ICEs. It's not yet economical but if PV keeps getting cheaper it will be. So it seems like the effort described in TFA is barking up the wrong tree?
Ammonia? WOW! As at
https://en.wikipedia.org/wiki/Ammonia#Combustion
4 NH3 + 3 O2 → 2 N2 + 6 H2O
The stuff is darned dangerous, quite challenging to handle, highly regulated due to the dangers, with lots of potential for toxicity, and likely close to ammonium nitrate, one heck of an explosive, etc., but a little arithmetic might show some astounding energy per gallon.
If it has a lot of potential, then I'd wonder why it has not been used in military piston/jet engines.
I would guess that a little too much O2 would give off nitric acid, etc.
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#215Earlier quoted context omitted.
Hi Rob! Is it possible to produce gasoline through atmospheric CO2 capture for less than traditional methods? Will CO2 capture be competitive in real costs?
I cannot see how you could take CO2 and make gasoline out of it using less energy than what the gasoline contains. At best, you will need to supply that energy via something like solar panels. Then it becomes a question of efficiency: how many Watts of gasoline can you produce per Watt of electricity you have? My guess is, not many.
The ideal method would be CRISPRing up some algae to synthesize gasoline, but we're pretty far from that.
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#216Wouldn't it make more sense to pull the CO2 directly out of the exhaust pipe, because the concentration is higher there?
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#217Wouldn't it make more sense to pull the CO2 directly out of the exhaust pipe, because the concentration is higher there?
Because you’d need additional tanks and pipe work. And you’d add additional back pressure to the engine which would decrease the efficiency of the engine and only get worse as the tank filled.
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#218Earlier quoted context omitted.
Maybe cars, but the weight of batteries is a problem for larger vehicles that need long range, like a bus, truck, or plane. For those hydrogen might be better.
> the weight of batteries is a problem for larger vehicles that need long range, like a bus, truck, or plane. For those hydrogen might be better. China is already leading the world in electric busses. They work great. Busses are such good vehicles for batteries, that for some routes it may even make sense to run them with super-capacitors, with chargers embedded in the road at stops. Trucks are always going to be a p…
A small percentage of vehicles by sheer number perhaps, but not by miles travelled. An average truck is working 50 hr weeks, plus commute time for the driver etc. As opposed to your average car which runs twice a day for 30 mins.
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#219Earlier quoted context omitted.
Point sources won't scale to the size of the problem. Easier initially, but to replace fossil fuels for transportation and heating, will need to get the CO2 from the air.
>Easier initially... Then start with point sources initially. Considering a good portion of transportation and basically all of the heating can be replaced by electricity directly, you will not need to go beyond point sources anyway.
There is a much more efficient way to deal with point sources, if you have a clean energy source in their neighborhood: just shut them down and replace the energy they provide with the clean energy you would use to scrub the CO2 from the air.
Re: A Quest to Make Gasoline Out of Thin Air: Prometheus (YC W19)
#220This is really, fundamentally important technology. Emissions reduction will not work: https://www.scientificamerican.com/article/nations-are-not-r... > The authors of the report stated in a press release that the kind of drastic, large-scale action the planet desperately needs has yet to be seen, even though global emissions have reached record levels at 53.5 billion metric tons in 2017, with no signs of peaking. >…
> The only serious solution to climate change is carbon recapture.
To me it always comes back to the numbers: sifting 400 parts out of a million of anything is intrinsically a pain in the ass. There's no way this is ever going to scale.