Reversible fuel cells have so much more to offer to a new solar powered economy than batteries, as far as I can see.

Besides having a much smaller manufacturing impact, the capability of exchanging energy for valuable clean fuel and vice versa at any point in an ecosystem is something only seen when the whole System picture is put together. Production of both clean fuel, and of the food-from-sunlight (see "Solein") catalyst; hydrogen, could be ubiquitous, from distributed solar collection in and around every community, workplace, and city, with the effect that we would all be financially motivated towards maximising that infrastructure, with an end result of having fuel for all transportation produced at all points in the system.

I believe this is the only way out of the apparent energy cul-de-sac we find ourselves in as a species.

I think we are in process of evolving to it anyway, forced by nature, but it looks like still some pain before we realise as a species how it has to work.

It looks to me like humanity is at a point in its evolution, similar to the shoot of a tree, at the point when it first starts to form leaves.

Up until that point, all of the energy used by humanity was extracted from Earth, like the energy needed to grow the shoot to the point where it shoots leaves, humanity is now sprouting the first human equivalents of leaves all over our planet in the form of solar farms.

Right now, the flow of energy through humanity is in process of switching source, from limited Earth capital yielded only by extraction, to the unlimited donated energy of the sun.

So pretty soon we are going to see currency change from something representing capital, and promises to pay / promises to extract, to something representing donated energy.

That will bring in a new world, very different from any we know in history, it seems to me.

That is why a lot of folk think the world is turning upside down.

Actually it is just our species moving to its next phase, beyond what we might see in the future as what was really just the selfish infant stage.