We literally do not know if we will ever be able to store enough energy to fly a plane with energy generated through wind, solar, etc.. We don't even know if it is possible through the laws of physics. Why not focus on cold fusion instead? Why not incentivize harnessing power from the rainbows farted by unicorns?
Governments incentivizing one action, by definition, detract from opportunities to invest in other areas. Relying on government to pick winners while government officials keep their hands off piles of money in their control won't work. It never does. Government's most impactful and viable role should be to make sure those willing to invest in "green" are not impeded by outside forces interested in stifling them.
It's possible that Beetlegeuse has already gone supernova and that the gamma rays from it are careening our way. If that's true, however unlikely, we'll soon be extinct. Just in case, shouldn't government incentivize a deflector beam device to save us all?