In reply to wintertree:
> That's like saying we have a lot of "free" energy from fossil fuels. It's just there, just like the sun, right? Certainly there's enough for an awfully long time. There's enough transuranics to power the world for over a 1000 years, is that "free"?
> Harvesting sunlight as our primary energy source has large costs. If it didn't, people would be turning a tidy profit using it to recycle all sorts of things that are expensive to extract from the earth.
> Solar-PV is getting rapidly cheaper. Grid scale storage, balancing and distribution technologies are not, and are themselves quite resource heavy.
> I don't think solar will ever deliver radically different energy prices to the current systems - less carbon yes, but not a transformative drop in energy prices. That awaits something else.
> The fact remains that a "circular" economy still demands a massive increase in entropy, and that demands lots of energy conversion ("generation"). The primary limit to this is the energy conversion not public education or financing models. Where there is money to be made doing these things, they are being done.
> Vastly cheaper energy would enable much tighter resource reuse and also decouple the generation of food from agriculture, allowing a lot of the planet to be retuned to a pre-farming biosphere.
Not sure what you mean by asking if fossil fuels / fissile elements are "free"? They're free in the sense that the energy we can receive from reducing them outweights the energy spent on the process. They're free in the sense that if you only pay a process cost and sell the energy you make a profit. They're a complete clusterf(*&k waste of money if you take into account the effects on the biosphere as part of the cost model.
Harvesting solar does have a large cost. But I think you're using the rational market model as the basis for your argument that "if you could make a profit doing it, people would". It's well established that every market humans have come up with has suffered from flaws of human thinking. I think solar is good enough as it is now to disrupt the market, but there are other factors involved such as fossil fuel subsidies and cronyism that will prevent this from happening quickly.
As I've mentioned in another thread - using HVDC and the southern fringes of Europe/Africa/Asia as generation points, a large power distribution network could be developed that provides high-level power for 14-20 hours a day to Eurasia could be developed. Existing technologies such as molten salt storage could increase that to 24 hours a day. There are no major technological issues, only political.
Your claim that a "circular" economy would generate a massive increase in entropy is not correct in the context of the Earth alone. It is quite possible for the entropy of the solar system to increase, but the entropy of Earth to decrease. This is usually what is meant by using the sun's energy on Earth, we are massively increasing the entropy of the solar.