Well there is geothermal besides the sun, though that is neither here not there as per your proposals. I read an article, I think here on Medium, where some company is taking high-powered lasers developed for fusion reactors and repurposing them to drill wells (not very wide but really really deep) to provide geothermal practically anywhere. Best places to use it: next door to a coal-fired electricity generation plant, and then convert the plant over to geothermal. I like that!