Solid oxide fuel cell stack

A solid oxide fuel cell stack (10) comprising a plurality of modules (12), each module (12) comprising an elongate hollow member (14), each hollow member (14) having at least one passage (32) extending longitudinally through the hollow member (14) for the flow of a reactant, each hollow member (14) having two parallel flat surfaces (16,18), at least one of the modules (12A,12B,12C) including a plurality of solid oxide fuel cells (20), the solid oxide fuel cells (20) being arranged on at least one of the flat surfaces (16,18) of the at least one module (12A,12B,12C), the surfaces (16,18) of adjacent modules (12A,12B,12C) being arranged substantially parallel and spaced apart, characterised in that at least one end (34) of each module (12) being connected to an end (36) of an adjacent module (12) to allow reactant to flow sequentially through the modules (12) and such that thermal and mechanical stresses in the solid oxide fuel cell stack (10) are reduced.