There are power plants that generate electricity from thermal differentials, but these are ocean based systems. That said, the same principle could be applied to take advantage of the differential between hot surface temperatures and cooler sub-surface temperatures on terra firma. The issue would be one of cost/practicality for collecting/pumping the cooler sub-surface temperature.
I also recall reading a while back about some R&D being done with nano tech and semi-conducting materials to generate electricity from temperature differentials in a more cost effective manner (and with less exotic materials) than what is used in the aerospace industry. If you want a real off the wall concept: see if there is a "macro-tech" way of achieving a similar outcome utilizing the semi conductive and thermal insulating properties in desert sand. I did say it was a bit of a wild idea ...