I was already thinking about this idea!
My thoughts on this topic:
It takes about 3000 dollars for solar panels that can supply standard mining rig (1,5 kw).
This is quite expensive for faster return of investment but is cost-effective in the long run.
A mylty coin mining rig is required (For example with Nvidia 1080 graphic card or new special mining cards) in order to mine different cryptocurrencies when they are profitable.
Mining is required for "proof of work" based cryptocurrencies like etherium or litecoin.
But mining is no longer as important as before because new cryptocurrencies based on "proof of stake"emerged. That's why I didn't further elaborate that idea.