The invention relates to a stack (200) comprising a plurality of stacked fuel cells (100), fixed and fluidically connected to a first head (210), which comprises: a feeding inlet (301) for a fuel flow and a corresponding outlet (302); a feeding inlet (303) for a comburent flow and a corresponding outlet (306); a feeding inlet (302) and a corresponding outlet (305) for a flow of a cooling heat-transfer fluid thermally coupled with the fuel cells (100) in order to remove at least part of the reaction heat at the fuel cells (100) themselves; the first head (210) comprising a feeding inlet (307) and a corresponding outlet (308) for a flow may pass, said volume being thermally coupled with the cooling heat-transfer fluid flow, so that the cooling heat-transfer fluid delivers at least some of the heat removed from the fuel sells (100) to the working heat-transfer fluid.