A high efficiency hydrogen fuel system for an aircraft at high altitude which utilizes compressors to compress air to a sufficiently high pressure for the fuel cell. Liquid hydrogen is compressed and then utilized in heat exchangers to cool the compressed air, maintaining the air at a temperature low enough for the fuel cell. The hydrogen is also used to cool the fuel cell as it is also depressurized prior to its entry in the fuel cell cycle. A water condensation system allows for water removal from the airstream to reduce impacts to the atmosphere. The hydrogen fuel system may be used with VTOL aircraft, which may allow them to fly at higher elevations. The hydrogen fuel system may be used with other subsonic and supersonic aircraft, such as with asymmetric wing aircraft.

A fuel cell hot box for improving the system efficiency of a fuel cell. Fuel cell stack parts, an after burner, a reformer, an air pre-heating zone, and a fuel-heat exchanger are provided in a housing allowing heat of the fuel cell stack parts and heat of combustion gas generated in the after burner to be used for reforming, preheating fuel and preheating air at the same time to avoid wasting energy. The fuel cell stack parts under thermal stress can be cooled to improve durability of the stack parts to increase a lifetime of a total system, and the stack parts can share the central chamber part to simplify a structure of the fuel cell hot box. In addition, the reformer includes an opening and closing unit to properly distribute the high-temperature combustion gas so that a reforming ratio is adjustable according to an operating condition of the fuel.

A steam methane reformer-integrated fuel cell system includes: at least one fuel cell including: an anode, a cathode, and an electrolyte matrix separating the anode and the cathode; an anode gas oxidizer (AGO) configured to receive anode exhaust gas from the at least one fuel cell and a preheated air stream such that the anode exhaust gas reacts with the preheated air stream to produce a high-temperature exhaust stream, and configured to provide the high-temperature exhaust stream to the cathode of the at least one fuel cell; and a steam methane reformer configured to utilize heat from the high-temperature exhaust stream output from the AGO and to react methane with steam to produce a first product stream including hydrogen (H.sub.2), carbon dioxide (CO.sub.2), and carbon monoxide (CO).

A carbon dioxide recovery system for collecting carbon dioxide from an exhaust gas generated in a facility including a combustion device includes: a first exhaust gas passage through which the exhaust gas containing carbon dioxide flows; a fuel cell including an anode, a cathode disposed on the first exhaust gas passage so that the exhaust gas from the first exhaust gas passage is supplied to the cathode, and an electrolyte transferring, from the cathode to the anode, a carbonate ion derived from carbon dioxide contained in the exhaust gas from the first exhaust gas passage; and a second exhaust gas passage diverging from the first exhaust gas passage upstream of the cathode so as to bypass the cathode. A part of the exhaust gas is introduced to the second exhaust gas passage.

A fuel cell overheating protection system and method. The system comprises a fuel gas isolation valve (1), a flow control unit (2), a combustor (3), a first controller (4), a second controller (5), a first temperature sensor (6), a second temperature sensor (7), a first switch K1 and a second switch K2. By utilizing the system, a fuel cell fault caused by overheat combustion can be effectively avoided.

A steam methane reformer-integrated fuel cell system includes at least one fuel cell having an anode, a cathode, and an electrolyte matrix separating the anode and the cathode. The system further includes a steam methane reformer configured to react methane with steam to produce a first product stream including hydrogen (H.sub.2), carbon dioxide (CO.sub.2), and carbon monoxide (CO).

A fuel cell system includes a reformer, fuel cell stacks, and an exhaust-gas combustor. The reformer has a tubular shape extending in an axial direction and reforms raw fuel into combustion gas. The fuel cell stacks generate electric power from the fuel gas and oxidant gas. The fuel cell stacks are arranged radially outward of the reformer in a circumferential direction to face the reformer in a radial direction. The exhaust-gas combustor burns fuel gas that is not used and included in exhaust gas from the fuel cell stacks. The exhaust-gas combustor is arranged radially inward of the reformer to face the reformer in the radial direction. Each fuel cell stack includes flat plate type cells stacked in the radial direction. This achieves downsizing of the fuel cell system.

A solid oxide fuel cell (SOFC) system includes high thermal conductivity materials such as copper to increase thermal energy transfer by thermal conduction. The copper is protected from oxidation by nickel electroplating and protected from thermal damage by providing oxidation resistant liners inside combustion chambers.

A fuel cell system includes a solid oxide fuel cell capable of generating power by receiving a supply of a reformed gas and an oxidant gas; an oxidant gas supply device that supplies the oxidant gas to the fuel cell; a reforming unit that supplies the reformed gas to the fuel cell; a fuel supply device that supplies a fuel which is a raw material for the reformed gas to the reforming unit; a combustion unit that combusts discharged gases of the fuel cell, wherein the reforming unit can reform the fuel into the reformed gas by exchanging heat with a combustion gas produced by the combustion unit; and a first control unit controls the fuel supply device to additionally supply the fuel to the fuel cell through the reforming unit in order to prevent the oxidant gas from flowing in from downstream of a fuel electrode of the fuel cell at the time of stopping the system. The fuel cell system further includes a second control unit that controls to supply the fuel to the reforming unit before the additional supply so that the temperature of the reformed gas flowing into the fuel cell does not exceed a predetermined temperature at the time of stopping the system.

A fuel cell system comprising: a fuel cell configured to be supplied with a fuel and air to generate an electric power; a combustor configured to combust an off-gas discharged from the fuel cell to produce a combustion discharged gas; a fuel heating part configured to heat the fuel to be supplied to the fuel cell by the combustion discharged gas; an air heating part configured to heat the air to be supplied to the fuel cell by the combustion discharged gas; an anode-side distribution passage configured to distribute the combustion discharged gas to the fuel heating part; a cathode-side distribution passage configured to distribute the combustion discharged gas to the air heating part; and a discharged gas distribution ratio adjustment part configured to adjust a discharged gas distribution ratio, the discharged gas distribution ratio being a ratio of an anode-side combustion discharged gas flow rate to a cathode-side combustion discharged gas flow rate, the anode-side combustion discharged gas flow rate being a flow rate of the combustion discharged gas that flows in the anode-side distribution passage, the cathode-side combustion discharged gas flow rate being a flow rate of the combustion discharged gas that flows in the cathode-side distribution passage, wherein the discharged gas distribution ratio adjustment part is configured to reduce the discharged gas distribution ratio according to an increase in a supply air flow rate as a flow rate of the air to be supplied to the fuel cell.