Abstract: The invention relates to a method for determining critical operating states in a fuel cell stack, consisting of single cells connected in series, wherein a low-frequency current or voltage signal is applied to the fuel cell stack, the resulting voltage or current signal is measured and the distortion factor thd is determined. According to the invention, the weighted sum of a term dependent on the membrane resistance RM and a term dependent on the distortion factor thd is used to determine an indicator THDAdryout correlating with the drying out of the fuel cell membranes of the fuel cell stack, the membrane resistance Rm being detected by impedance measurement.

Abstract: The invention relates to a method for determining critical operating states in a fuel cell stack, consisting of single cells connected in series, wherein a low-frequency current or voltage signal is applied to the fuel cell stack, the resulting voltage or current signal is measured and the distortion factor thd is determined. According to the invention, the weighted sum of a term dependent on the membrane resistance RM and a term dependent on the distortion factor thd is used to determine an indicator THDAdryout correlating with the drying out of the fuel cell membranes of the fuel cell stack, the membrane resistance Rm being detected by impedance measurement.

Abstract: The invention relates to a method for determining critical operating states in a fuel cell stack, consisting of single cells connected in series, wherein a low-frequency current or voltage signal is applied to the fuel cell stack, the resulting voltage or current signal is measured and the distortion factor thd is determined. According to the invention, the weighted sum of a term dependent on the membrane resistance RM and a term dependent on the distortion factor thd is used to determine an indicator THDAdryout correlating with the drying out of the fuel cell membranes of the fuel cell stack, the membrane resistance Rm being detected by impedance measurement.

Abstract: The invention relates to a method for determining critical operating states in a fuel cell stack, consisting of single cells connected in series, wherein a low-frequency current or voltage signal is applied to the fuel cell stack, the resulting voltage or current signal is measured and the distortion factor thd is determined. According to the invention, the weighted sum of a term dependent on the membrane resistance RM and a term dependent on the distortion factor thd is used to determine an indicator THDAdryout correlating with the drying out of the fuel cell membranes of the fuel cell stack, the membrane resistance Rm being detected by impedance measurement.

Abstract: The invention relates to a method for determining critical operating states in a fuel cell stack, consisting of single cells connected in series, wherein a low-frequency current or voltage signal is applied to the fuel cell stack, the resulting voltage or current signal is measured and the distortion factor thd is determined. According to the invention, the weighted sum of a term dependent on the membrane resistance Rm and a term dependent on the distortion factor thd is used to determine an indicator THDAdryout correlating with the drying out of the fuel cell membranes of the fuel cell stack, the membrane resistance Rm being detected by impedance measurement.

Abstract: The invention relates to a method for determining critical operating states in a fuel cell stack, consisting of single cells connected in series, wherein a low-frequency current or voltage signal is applied to the fuel cell stack, the resulting voltage or current signal is measured and the distortion factor thd is determined. According to the invention, the weighted sum of a term dependent on the membrane resistance Rm and a term dependent on the distortion factor thd is used to determine an indicator THDAdryout correlating with the drying out of the fuel cell membranes of the fuel cell stack, the membrane resistance Rm being detected by impedance measurement.

Abstract: In a method for operating a high-temperature fuel cell, which in normal mode of generating electrical power is supplied with liquid fuel, preferably diesel oil, and is preceded on the anode side by a reformer for liquid fuel, where at least part of the hot anode exhaust gas is recirculated into the anode circuit via a recirculation line. Upstream of a compressor preceding the reformer the liquid fuel is sprayed or injected into the hot anode exhaust gas, the quantity of air needed for reforming the liquid fuel being added to the mixture of anode exhaust gas and fuel. On change-over from normal operational mode to standby mode without power generation, the supply of liquid fuel and air is stopped and the gas mixture present in the anode circuit be permanently circulated. A defined amount of air being introduced into the anode circuit in order to remove deposits and contaminations in the high-temperature fuel cell following standby operation.

Abstract: In a method for operating a high-temperature fuel cell, which in normal mode of generating electrical power is supplied with liquid fuel, preferably diesel oil, and is preceded on the anode side by a reformer for liquid fuel, where at least part of the hot anode exhaust gas is recirculated into the anode circuit via a recirculation line. Upstream of a compressor preceding the reformer the liquid fuel is sprayed or injected into the hot anode exhaust gas, the quantity of air needed for reforming the liquid fuel being added to the mixture of anode exhaust gas and fuel. On change-over from normal operational mode to standby mode without power generation, the supply of liquid fuel and air is stopped and the gas mixture present in the anode circuit be permanently circulated. A defined amount of air being introduced into the anode circuit in order to remove deposits and contaminations in the high-temperature fuel cell following standby operation.

Abstract: In a method for monitoring the operating state of a battery, preferably a Ni metal hydride or a Li-ion battery, formed of consisting of one or several interconnected battery cells, during the charging and discharging of the battery a low-frequency alternating current signal or voltage signal is applied to the battery. The resulting voltage or current signal is measured and the operating state of the battery or its battery cells is determined from at least one change in the harmonic distortion content of the measured voltage or current signal.

Abstract: A thermoelectric generator for converting thermal energy into electrical energy includes a plurality of Peltier elements which are coupled into a module and are arranged between a heat source and a heat sink, with each Peltier element having of a p-doped leg and an n-doped leg which are connected at their ends in an electrically conductive manner by electrodes. Both the p-doped legs and the n-doped legs of the individual Peltier elements are made of different materials, the efficiency of which is optimized with respect to the different temperature values at the contact points of the individual Peltier elements to the heat source. The high-temperature range of the p-doped legs includes MMyFe4-xCoxSb12 and/or MMyFe4-xNixSb12, with MM being a misch metal of La, Ce, Pr, Nd and Sm, and the high-temperature range of the n-doped legs includes AyCo4-xTxSb12, with A standing for Ba, Ca, Sr and a mixture thereof and T for Ni and Pd.

Abstract: A piezoelectric sensor device, especially for use with a microbalance, with a sensor housing and a holder for holding a piezoelectric sensor element. In order to permit quick exchange of crystals and to minimize the size of the assembly, the holder is configured as a clamping element which has at least one elastic first arm for clamped holding of the contact region of the essentially strip-shaped piezoelectric resonator element, whose measuring region is subjected to a fluid stream to be measured.

Abstract: The invention relates to a method and a device for operating a high-temperature fuel cell using liquid fuel, preferably diesel oil, where a reformer for the liquid fuel precedes the high-temperature fuel cell on the anode side. A recirculation line for the hot anode exhaust gas is provided, which departing from the outlet side of the anode of the high-temperature fuel cell leads to the inlet side of the reformer, an injector for spraying or injecting the liquid fuel into the hot anode exhaust gas being located upstream of a compressor preceding the reformer. The resulting cooling of the anode exhaust gas will permit the use of conventional positive displacement or rotary pumps in the anode circuit.

Abstract: The invention relates to a device for supplying at least one process gas, with independently set temperature and mass flow, in an input line of a test bed for fuel cells or fuel cell components, such as reformer, catalytic converter, etc. At least two dynamically controlled gas injectors are provided for each process gas, which are connected to feeder lines for two partial streams each at defined but different temperature levels, and which open into the input line for the process gas.

Abstract: The invention relates to a piezoelectric sensor device, especially for use with a microbalance, with a sensor housing and a holder for holding a piezoelectric sensor element. In order to permit quick exchange of crystals and to minimize the size of the assembly the holder is configured as a clamping element, which has at least one elastic first arm for clamped holding of the contact region of said essentially strip-shaped piezoelectric resonator element, whose measuring region is subjected to a fluid stream to be measured.

Abstract: The invention relates to an energy generation unit comprising at least one high-temperature fuel cell, which is preceded by a reformer for preprocessing the fuel for the high-temperature fuel cell, having an outgoing line at the cathode side, which transfers thermal energy to the reformer. The reformer is placed in a preferably cylindrical combustion chamber of a flame burner, which flame burner is activated during the start-up phase of the energy generation unit, and the combustion chamber of the flame burner is connected to the outgoing line at the cathode side of the high-temperature fuel cell in order to subject the reformer to cathode exhaust gas from the fuel cell.

Abstract: This invention relates to an internal combustion engine, in particular of the self-igniting type, with a compressor, which is preferably connected to an exhaust gas turbine and is located in an intake flow passage for compression of the intake air, and with a charge air line leading to an intake manifold, the compressor operating independently of the engine, at least in the starting phase. To permit a quick and simple start-up of the engine at a low compression ratio the proposal is put forward that an air recirculation line controlled by a valve depart from the intake manifold, which opens into the intake flow passage upstream of the compressor, charge air line and air recirculation line forming a closed loop.