NOVELTY - Fuel cell comprises a chamber for holding an electrolyte, a mechanism to enable rotation of the electrolyte about an axis of rotation of the chamber, at least one structure defining inlet(s) for introducing an oxidant and/or a fuel into the chamber, electrode(s) contactable with the electrolyte and the oxidant, and electrode(s) (5) contactable with the electrolyte and the fuel.    USE - Used for vehicles (claimed).    ADVANTAGE - The fuel cell exhibits increased working efficiency. Centrifugal forces acting on the electrolyte phase together with inverse-centrifugal forces acting on the oxidant and/or fuel phases act jointly to increase the overall circulation flow rate so improving the overall rate of chemical reaction. The acceleration field induced in the fuel cell as a result of rotation of the electrolyte about an axis of rotation of the chamber and the improved convection which results can promote and improve the internal circulation of the electrolyte fluid without the use of pumps. The cell uses the enhanced natural circulation to provide an increase in the power output of fuel cells. The use of enhanced natural circulation reduces the need for external pumps, piping or other components, resulting to a more compact and cost-effective design with fewer moving parts so increasing overall reliability. It also reduces the dendritic growth of species, e.g. metal oxide crystals, which can be responsible for short circuiting fuel cell devices. The enhanced throughput of oxidant and/or fuel also enables the use of higher flow resistance electrodes. The fuel cell also exhibits controllable power output.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (A) a fuel cell system comprising several fuel cells which are physically connected in series with one another and electrically connected in series or in parallel with one another; and    (B) a method for improving the efficiency and performance of a fuel cell, which comprises introducing an oxidant and/or fuel into contact with an electrolyte present in a fuel cell by at least one inlet spaced from the axis of rotation of the chamber and rotating the electrolyte about an axis of rotation of the chamber.