Not everyone mine with coal. «A signifcant concentration [of Bitcoin mines] can be observed in the Sichuan province, where miners have struck deals with local hydroelectric power statons to access cheap electricity» p. 94 of https://www.jbs.cam.ac.uk/fileadmin/user_upload/research/cen...

Also, coal in China is much cleaner than coal in the US, for example. https://www.americanprogress.org/issues/green/reports/2017/0...

Many are located in Georgia and WA (honourable mention goes out to Labrador), which have cheap hydroelectricity.

Soon to be located in Africa - more sun, cheap panels.

I think solar would have to become cheaper before this becomes viable.

Luckily trends show that this will happen soon, but other challenges posed in Africa is political stability (e.g. government decides BitCoin mining is illegal or imposes unreasonable taxes due to lack of understanding), lack of competency, and other types of infrastructure.

The only countries I can see that are suitable are South Africa and Namibia.