Mostly they're concentrated around cheap hydroelectricity, with major mines in Labrador (2c/kwh), Central China (varies, but <4c/kwh), and Georgia (unknown, bitfury likely has a special deal with the local government). A few exceptions are Northern China (coal grid @ ~3c/kwh) and Iceland (geothermal @ maybe 5c/kwh, this isn't too clear either).
Solar panels are not effective for bitcoin mining, because hardware needs to run 24/7 (a shitload of batteries are needed) and the upfront cost is high.
Why?
Now if the price of solar electricity is completely free and bitcoin doesn't crash then mathematically there'll come a point when you'll break even but it might take a long while as the mining rewards keep dwindling as difficulty increases while you spend most of your time not mining. Eventually your miner hardware or solar panels will need maintenance and that will increase your costs.
You'd have to do the math to see how long it'll take you to break even, but something tells me that it won't be nearly as competitive as those server farms using cheap hydroelectricity.
The problem is that you have the difficulty going up, and the capital costs.
Track those three curves and you have a good sense of the window for profit.
The biggest mining operations have legal partnerships with local and national governments.[1] As well, Russia isn't a major place for bitcoin mining: instead, mining is mostly concentrated in Georgia (the country, not the state) and China.
