It's funny to see people suddenly say this is doable, even though many posters in the past have claimed that it is totally impossible.
The problem ultimately is that CO₂ capture from the air is another expense that has to be paid, both in terms of cost and energy. Sure, if the entire process becomes so cheap and widely available that this no longer becomes issue, then we can certainly do it. But until then, it is a major stumbling block.
The other problem is that if all you want is something more "practical" than hydrogen, you will stop at methane. Same basic idea as this, but you only need the Sabatier process. And we already have many facilities capable of dealing with methane. So we do not necessarily need to go further. But if you insist on long carbon chains, why stop at C3? Keep going until you reach C8, or even C12-20, at which point you have the equivalent of gasoline or diesel. Basically, get to the point where you have a liquid at room temperature, and it will be even more practical than propane.
> The problem ultimately is that CO₂ capture from the air is another expense that has to be paid, both in terms of cost and energy. Sure, if the entire process becomes so cheap and widely available that this no longer becomes issue, then we can certainly do it. But until then, it is a major stumbling block.
That is, of course, very true. Per calculations upthread, the energy cost of DAC isn't that huge, but indeed it's for the time being a very immature technology that hasn't been demonstrated at scale.
> The other problem is that if all you want is something more "practical" than hydrogen, you will stop at methane. Same basic idea as this, but you only need the Sabatier process. And we already have many facilities capable of dealing with methane. So we do not necessarily need to go further.
In principle yes. I guess it's a question of cost. Is the cost of an H2 electrolyzer + the Sabatier reactors etc. lower than this propane electrylyzer? If this propane electrylyzer thing could be done cheaply, that could be the gamechanger. Not the fact that it's technically possible to manufacture synthetic hydrocarbons, we have multiple ways of doing that, though all of them tend to be both expensive in terms of capital cost and somewhat inefficient.
> But if you insist on long carbon chains, why stop at C3? Keep going until you reach C8, or even C12-20, at which point you have the equivalent of gasoline or diesel. Basically, get to the point where you have a liquid at room temperature, and it will be even more practical than propane.
Indeed, from a handling and transportation point of view, the longer hydrocarbons are pretty much optimal. But like above, it's a question of cost. Fischer-Tropsch installations tend to be very capital intensive, yield is an issue etc.
So if this propane electrolyzer turns out to be industrially feasible at a low enough cost, maybe it's overall more efficient to deal with pressurized storage systems.
> Per calculations upthread, the energy cost of DAC isn't that huge
All I’ve seen so far are speculations based on a small prototype in Iceland that is still very expensive and has access to free energy. I’ve had to add up the costs that you list myself (you are not giving any numbers), and it ends up being a prohibitively expensive gallon of fuel—an order of magnitude more expensive than it is now. How is that reasonable when most states would lose their head with a 10% increase?
My concern is that most of the time, the math goes: “Let’s assume electricity is free, and people somehow still want to drive an ICE.” and conclude with, “We just have to continue subsidizing a pathologically dangerous pollution by 90%.” hoping to capitalize on the heads of states fear of a revolution.
I can see why that looks tempting to people who refuse to admit that we must shift away from fossil fuels and latch on to plans to paint their industrial assets as renewable. Still, it ends up being an inefficient Rube-Goldberg machine, where adding solar panels on the roof of wherever you need energy works. I’m all for failing convincingly, but you must admit when it’s not working.
I’ve heard that mining equipment was too large and could never be electrified… Those converted the fastest (custom engines, high torque, regenerative power, far away from fuel supply but sunny/windy location) and with glee (lower maintenance when technicians have to fly in by helicopter). Prototype boats and airplanes can work “indefinitely” because solar panels can generate enough energy for them to work 24/7.
I’ve yet to hear about a single industrial process that needs carbon-chain fuel to work.
The problem ultimately is that CO₂ capture from the air is another expense that has to be paid, both in terms of cost and energy. Sure, if the entire process becomes so cheap and widely available that this no longer becomes issue, then we can certainly do it. But until then, it is a major stumbling block.
The other problem is that if all you want is something more "practical" than hydrogen, you will stop at methane. Same basic idea as this, but you only need the Sabatier process. And we already have many facilities capable of dealing with methane. So we do not necessarily need to go further. But if you insist on long carbon chains, why stop at C3? Keep going until you reach C8, or even C12-20, at which point you have the equivalent of gasoline or diesel. Basically, get to the point where you have a liquid at room temperature, and it will be even more practical than propane.