Here in W.Australia we've been using solar powered signal repeaters along rail lines and mesa tops since the mid 1970's in the Pilbara mining industry.

Solar powered bores for farms in the wheatbelt and cattle country has been a regular feature for over a decade now.

The panels and batteries are better than ever now, but they've been Total Cost break even better than fossil fuel alternatives in remote Australia for a very long time (esp. factoring in need to travel to a bore to refuel, etc. Vs "it just works" (until it doesn't, but all solutions require upkeep)).