And they have a lifespan of 20-ish year, zero possible payback, and take WAY more area.
I think that panel lifetime, efficiency and economics relative to utility power have evolved quite a bit since you last looked into it. That doesn't necessarily mean the Audi process is an efficient way to use electricity, although it might be someday. The interesting bit about it is carbon-neutrality. Burn the fuel and release CO2, then recapture it when making more fuel.
It's hard to beat liquid fuel. It's the best on volume/mass efficiency, it's easy to transfer rapidly, and it's easy to store for long periods. Maybe someday when we get fusion figured out, or at least people chill out and allow modern fail-safe fission designs. There are also places where electricity is very, very cheap for other reasons. Some hydro depending on the market, also geothermal in Iceland I think. Isn't that why almost all aluminum smelting is done there?
If a process is developed that goes from electricity-plus-air to liquid fuel with
any semblance of efficiency, even if it's not very good, that opens opportunities.
There's solar panels available today with somewhat low efficiency (compared to the best modern ones) but are
very cheap. So they're really good in terms of $$ invested/kWh delivered, but you need too many to fit on your roof. Instead, you go put a shitload of them out in the desert. That doesn't make sense right now because of grid transmission losses and no local consumers. If you can get to liquid fuel instead? Game changer. That energy is captured into stable storage that can be marketed and used nearby, or transported long-distance by pipeline or tanker with relative ease.
Also, as Uwe kind of alluded to, baseload plants really like to put out a certain amount of power and wind/solar can be unpredictable. Sometimes you have more power than you can use, and you have to do
something with it, or things get explodey. Liquid fuel generation would be another good way to dump off excess power. In some cases, utilities have to literally pay (negative rates) to get rid of power. If you have electricity available that you literally have to pay to get rid of, who gives a shit if your liquid fuel generation is only 10% (made-up figure) efficient? Today in some places they use pumped hydro storage, like
Taum Sauk in Missouri. This would be another interesting option, along with battery stations and flywheels and other experimental stuff that's been done.
Jason