Cryptocurrency mining is a difficult and costly activity. Miners must pay to build rigs capable of vast amounts of processing power, and then the rigs themselves must be powered with large quantities of electricity. It's all a careful balance between how much the operation costs and how much profit it is able to generate.
With mining operations for Ethereum, one of the leading digital currencies on the market today, taking up same share of electricity as that of a small country, miners have to be careful that they aren't spending more than they are making. Because of that, some mining operations have begun to look to solar-powered rigs, set up in the desert, in order to reduce mining costs and make the largest profit possible.
Mining operations with the tools and resources to be able to set up solar-powered rigs in the desert are finding that it is a good investment. Once you have paid for the solar panel system itself, the cost of mining is virtually free. Getting rid of a hefty electric bill which typically weighs down mining operations leaves more room for profit.