In principle this is an idea worth pursuing. Single well heat...

In principle this is an idea worth pursuing. Single well heat exchangers are the holy grail of geothermal heat harvesting and but no-one has yet achieved a viable working example for electricity production. The basic problem is that the descending cold input fluid cools the up-flowing hot fluid, so the wall between them must be highly insulated.

CeraPhi seems to have the idea but no apparent projects, and is raising funds - so both sides are still finding their way. This is fine, they need to start somewhere, but the time-scale to profitable operation may be long, and the scale of initial operation may be small.

One way to accelerate the process is to find an used hydrocarbon well which taps high heat flow at depth, and which can be retro-fitted with the heat-exchange stem.

Overall, a more interesting plan than their previous geothermal plans.