Solar energy, carbon dioxide and water directly to butanol. In other words, store solar energy directly as fuel. There are other versions that generate hydrogen, but that has a much lower energy density than liquid fuel.

Just modify your existing ICE to run on butanol and you're good to go. <a bit of hand waving there.>

See https://www.intelligentliving.co/biofuel-solar-energy-co2-wa... for where we were a year ago.