Solid oxide fuel cell system

A solid oxide fuel cell system comprising:

• a solid oxide fuel cell stack;
• a compressor;
• and a turbine, the solid oxide fuel cell stack comprising at least one solid oxide fuel cell, each solid oxide fuel cell comprising an electrolyte, an anode and a cathode, the compressor being arranged to supply at least a portion of the oxidant to the cathode of the at least one solid oxide fuel cell, a fuel supply being arranged to supply fuel to the anode of the at least one solid oxide fuel cell, the solid oxide fuel cell stack being arranged to supply a portion of the unused oxidant from the cathode of the at least one solid oxide fuel cell back to the cathode of the at least one solid oxide fuel cell, the solid oxide fuel cell stack being arranged to supply a portion of the unused fuel from the anode of the at least one solid oxide fuel cell to a combustor, an oxidant supply arranged to supply oxidant to the combustor, the combustor being arranged to supply the combustor exhaust gases to a first inlet of a heat exchanger, the heat exchanger being arranged to supply at least a portion of the combustor exhaust gases from a first outlet of the heat exchanger to the turbine, the at least a portion of the oxidant from the compressor and the unused oxidant from the cathode of the at least one solid oxide fuel cell being arranged to be supplied to a second inlet of the heat exchanger to preheat the oxidant supplied to the cathode of the at least one solid oxide fuel cell, the heat exchanger being arranged to supply the at least a portion of the oxidant from the compressor and the unused oxidant from the cathode of the at least one solid oxide fuel cell from a second outlet of the heat exchanger to the cathode of the at least one solid oxide fuel cell.