Proof of work was not invented (or envisioned to be used with digital currencies) by Satoshi. It's been around since 1993. I can't really find a reference to prove what I claimed so I would agree I might have been misled to think that. But the truth is that it doesn't matter whether it was taken into account or not, what matters is that you can mine Bitcoin (or do any PoW) using untapped renewable resources (which is why big mining operations are based in places with abundant geothermal/hydropower and very little, if any, population) but you wouldn't be able to do much else in those places.