Abstract: A ceramic fuel cell(s) is supported in a heat conductive interconnect plate, and a plurality of plates form a conductive heater named a stack. Connecting a plurality of stacks forms a stick of fuel cells. By connecting a plurality of sticks end to end, a string of fuel cells is formed. The length of the string can be one thousand feet or more, sized to penetrate an underground resource layer, for example of oil. A pre-heater brings the string to an operating temperature exceeding 700° C., and then the fuel cells maintain that temperature via a plurality of conduits feeding the fuel cells fuel and an oxidant, and transferring exhaust gases to a planetary surface. A manifold can be used between the string and the planetary surface to continue the plurality of conduits and act as a heat exchanger between exhaust gases and oxidants/fuel.

Abstract: A fuel cell based subterranean heater for mineral extraction, in situ decontamination, or other applications. The fuel cells are preferably stacked within a casing which is then inserted into a hole bored, or otherwise formed, into the formation to be heated. Conduits within the casing, and preferably formed by adjacent, aligned holes formed through the plates of the individual fuel cells supply fuel and air and extract exhaust gases. An optional manifold is used to span the overburden without applying heat to it directly. The manifold may also function as a heat exchanger between incoming and exhaust gases. Preferably the fuel cell is fueled by gases produced by the formation and also generates electricity which is available for use or export.