I think this option is very good and it will be less expensive
I disagree, even with government subsidies solar panels are still incredibly expensive. It'd take a very long time to get a return on your investment.
That is correct. This is one reason why solar electricity is not so common (in general and not specific to mining).
It is abundantly available and if it indeed were inexpensive, you would solar electricity easily overtaking coal/other non-renewable sources of electricity.
You also need to be aware that the angle and amount of sun they get is going to have a huge impact on how much electricity is collected. Just because a solar panel says it can produce a certain amount of watts doesn't mean it always will. That is under perfect conditions. You will get maybe ,50-75% Depending on how you place it it can be more.