The danger I see with it not being solar powered from the outset, is that it will get pulled into the quagmire of greed etc associated with traditional money, this is where it has to go if it's negative powered, then it has overheads that have to be met, then you have to start worrying about efficiency, yada yada, it becomes just more bullshit business for profit which has to be energy extracted from the planet, pushing up the temperature etc.
Here is the thing, if we accept established cryptocurrencies are now solar powered, moving there automatically as they did, for the cheapest form of energy, there was nonetheless a very large amount of energy required, to get to the point of being now in money-fuel tree architecture.
That energy was consumed and thrown to heat when we still had a budget of sorts for that, the planet had headroom for the temperature rise, and there were significant stocks of cheap fossil fuels.
That budget isn't there any longer.
Hence another reason I would say make it solar powered from the outset.