A method for recovery of heat generated by the combustion of coal in situ within coal seams in the earth. Three embodiments are described: one, in which the coal seam crops out and into which can be drilled and inserted a pipe, through the coal seam, to a central point, where it is joined with a vertical pipe drilled from the surface. Water is supplied to the pipe at the point of outcrop. Fires are started within the coal seam and supplied with air from the surface by means of drilled boreholes. The heat of combustion converts the water in the pipe to steam which travels up the vertical pipe and is used to drive a turbine generator system. A second embodiment is used where there is an overlying aquifer above the coal seam. Fires are started by means of air supplied through boreholes leading from the surface into the coal seam. The heat of combustion converts the water in the aquifer to steam, which then is circulated out of the aquifer and up to the surface where it drives a turbine generator system. A third embodiment uses the hot combustion gases to heat water to steam in pipes in a vertical borehole.