TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Module: Cooling ducts (19) forming the coolant distribution structure may be embedded in the cooling surface of only one of the two pole plates (7a, 7b), then covered by the flat surface of the other plate or embedded in both plates as the mirror images of one another so as to form the distribution structure. There may be a flat conductive element (26) between the cooling surfaces but only within the area enclosed by the seal (21). This element contains graphite foil or a woven or non-woven fabric, sheet or paper made of graphite or carbon fibres. Recesses to hold the adhesive may be provided on the cooling surface(s) outside the seal (21).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Adhesive: Electrically non-conductive material, preferably based on cyanoacrylate or epoxy resin. EXAMPLE - Pole plates with a thickness of 3 mm were injection moulded from a graphite-thermoplastic composite material, then pole plates (7a) were provided with a cathode-side distribution structure for oxidising agent and (on the cooling surface) a coolant distribution structure, while pole plates (7b) were provided with an anode-side fuel distribution structure and (on the cooling surface) a mirror image of the structure on plate (7a). Seals (21) made from EPDM elastomer were adhesively bonded in a sealing groove and the cooling surfaces were bonded together with epoxy resin adhesive (outside the seal) which was cured for 1 hour at room temperature under pressure (1.3 MPa); a sheet of graphite foil was also placed between the cooling surfaces in the area enclosed by the seal. Pole plates (7a) and (7b) showed a volume resistance (at right angles to the plate) of 10.9 (11.6) and 11.6 (11.3) milliohms.cm2 respectively, with a total resistance (7a + 7b) of 22.5 (22.9) milliohms.cm2; the assembled module showed a resistance of 20.2 (30.4) milliohms.cm2, so that the contact resistance was -2.3 (7.5) milliohms.cm2. Parallelism values (difference between greatest and smallest thickness values at 4 points on the plate) were 0.02 (0.1) mm for plate (7a), 0.08 (0.09) mm for (7b) and 0.07 (0.07) mm for the module. Values in brackets are for a similar module without the graphite foil.