Hi John, thanks for your considered response, much appreciated. I believe we will watch as the solar capacity powering Bitcoin approaches something that could make up the difference between whatever fraction we have solar powered by then, and the remainder. China just recently threw out all of its miners. What is never mentioned, is what kind of power infrastructure was left behind, for the government to take control of. Imagine, if we were a government, discoving in our country a significant capacity of solar power, hidden away in remote places, not connected to the grid, enabling the miners to operate under the government taxation radar. We would probably see how we could put that infrastructure to much needed utility use. So it makes sense they kicked out the miners, to gain the utility of their solar infrastructure. That would make logical sense to me.
I think we would do that as a planet, when we realise that by doing it, we become entirely solar powered, and further mining, and the vast bulk of transactions would stop.
After that, what might sound like bad news for Bitcoiners, the capital value of their Bitcoins would be near zero, because of ubiquitouts free money by then. However, they would be in possesion of something more than capital, a uniquely valuable system of allocation, of the right to consume power, to generate our own personal cryptocurrencies, which we will find very useful, representing us, all of us individually, in markets trading mostly with free money. Weirdly, the holders of Bitcoin are likely to quickly find that to maximise what they get out of Bitcoin, they will have to willingly give away whatever fraction of the holdings they have, which happens to be more than they need, as by holding it, they would gain no advantage, unlike capital.
Whilst it is being mined, the way the algorithm works, literally the more power that can be farmed, the more tokens are won, so most miners would start with a small solar farm seed, and work up to much larger installation, gradually scaling it up as they go along, increasing tokens won.
That answers a little of your question about maintainability; there are a mixture of ages of panels, some older, some newer, as more layers get added to the original "Seed" installation. The short term effects of panal degradation are overridden by the increases in power seen from scaling up, but in a mature installation, intended for long term use, it would be necessary to keep an eye on all panels to ensure they are producing reasonable output, and to replace one at a time, whenever they drop below a practical threshold. Not difficult to do now with modern control and monitoring systems, a typical monitoring display might be shown as a kind of health map of the installation, with each panel showing a colour, corresponding to how well it was working. Green panels fine, amber panels might need replacing soon, red panels need to be replaced immediately, etc.
On comparisons with the efficiency of trees, logically solar panels are much, much higher efficiency, but only for our very specialised human needs, not the broad spectrum of the needs of all life supplied by real trees, We might make similar comparisons with birds, they fly incredibly well, much better than anything we've ever built, but we can fly at supersonic speeds, for our very specialist human needs, we surpass the performance of nature, but only in a very narrow spike, where we need it.
The energy we consume in food is only a very small fraction of the energy we use to drive to the food shops, for example, so the main bulk of energy we use as a species is in our industry, which, even with the current ineffeciencies, we can completely supply with solar - easily. The reason we haven't done so yet appears to be an incompatibility with our treatment of all money as capital, rather than as energy, it seems to me.
That looks like the biggest hurdle we need to leap over, and it is a big one, it has existed for around 120 years, since JP Morgan defunded the efforts of Nikolai Tesla to give us the free energy of the sun.
The thing most folk have a problem with is our belief that nothing is for free, all things have to have a cost, but with the energy of the sun, the only way we can have it, I mean really have it, is to accept it for free.
I am also uninvested in Bitcoin, so far. The main reason for that is I've been warned by banks more than once, after I approached them with crypto based business proposals, and even had a major account frozen, for a closely related reason, so I am inclined to wait until they finally see the light, or maybe by some chance I might start earning alternatively in Bitcoin or another crypto.
There is another related "prong" of these stories, which talks more about how fiat money could be used immediately, to do what we are expecting Bitcoin to do eventually, with no assistance from fiat if it comes to it, but that will be a very painful route to Kardashev 1.0, it seems to me. The best result would be for some major capaital holders to start to understand this, and see how a lot of pain could be short-circuited, if they start to issue free "Kardashev Money" funds straight away. You might see that story also in my Medium publications, it is followed by some numerical estimates in the story "Estimating Kardashev Money", though that is in a very provisional state, first attempt at making the calculations, there might be errors, it needs peer reviewed :)