Abstract: A fuel cell system performing a pre-process for electric generation in a fuel cell controls at least one of a flow amount of fuel gas flowing through a fuel gas supply path and a flow amount of off gas flowing through an off gas circulation path in order to regulate a circulation ratio of a mixed gas composed of the fuel gas and the off gas. The circulation ratio is a ratio between a mole flow amount of the off gas to a mole flow amount of the fuel gas. Before initiating usual electric generation of the fuel cell, the fuel cell system performs the pre-process in which the fuel gas is supplied to the fuel cell in order to set the circulation ratio within a predetermined range. The lower limit of the circulation ratio is set to a value by which all initial gas in a fuel electrode of the fuel cell before initiating the pre-process is exhausted completely.

Abstract: A fuel cell system with a fuel cell (FC stack) has an off gas circulation path to the fuel cell, an off gas exhaust unit, and an off gas pressure sensor. The system measures physical properties such as a pressure and temperatures of the off gas at various timings before and after the purging, and the calculator in the system calculates an off gas density and a hydrogen concentration in the off gas based on the measured physical properties. The system determines optimum conditions such as a start-up time and an operation period of time for the purging based on the measured and calculated values.

Abstract: A fuel supply system for use in a fuel cell system which includes a controller, a pressure regulator, and an ejector device. The controller controls the pressure of a main flow of fuel gas outputted from the pressure regulator and the position of an ejector nozzle of the ejector vacuum pump as a function of electricity generated by a fuel cell to adjust a flow rate of an off-gas to be recirculated to the fuel cell. This structure eliminates the need for an additional flow regulator to regulate the flow rate of the off-gas, thereby ensuring the stability in controlling the flow rate of the off-gas to be recirculated.

Abstract: Under a condition that a main stream hydrogen amount fed into a fuel cell is constant, an off-gas circulation amount and a hydrogen concentration of the circulated off-gas are in a predetermined relationship. Considering this relationship, the hydrogen concentration of the circulated off-gas can be obtained by detecting the main stream hydrogen amount and the off-gas circulation amount. The impurities contained in the circulated off-gas are chiefly nitrogen. The nitrogen concentration of the circulated off-gas is inverse proportional to the hydrogen concentration. The nitrogen concentration (i.e., impurity concentration) is obtainable by detecting the hydrogen concentration. Increase of impurities contained in the circulated off-gas is detectable in advance based on the main stream hydrogen amount and the off-gas circulation amount. The impurities can be removed before the output of the fuel cell becomes unstable. The fuel cell operates stably.

Abstract: A fuel cell system is provided which includes a fluid pump such as an ejector pump. The fluid pump is designed to be driven by energy of air flowing within an air line through which air is supplied to a fuel cell. The fluid pump works to suck a fluid containing drops of water and residual gasses from the hydrogen line, thereby ensuring desired startability and stability of operation of the fuel cell.

Abstract: A hydrogen storage unit is provided with a hydrogen storage container containing a hydrogen absorption material, and a filter portion for eliminating impurities contained in stored hydrogen gas. Thereby, the impurities are eliminated from the stored hydrogen gas in the hydrogen storage container, and the hydrogen absorption material is prevented from being poisoned by the impurities. The filter portion can be provided either inside or outside the hydrogen storage container. An adsorbent for adsorbing the impurities can be used in the filter portion. The filter portion is provided with a heating means for enhancing the elimination of the impurities adsorbed in the filter portion, and can be recovered during operation.

Abstract: A hydrogen storage unit is provided with a hydrogen storage container containing a hydrogen absorption material, and a filter portion for eliminating impurities contained in stored hydrogen gas. Thereby, the impurities are eliminated from the stored hydrogen gas in the hydrogen storage container, and the hydrogen absorption material is prevented from being poisoned by the impurities. The filter portion can be provided either inside or outside the hydrogen storage container. An adsorbent for adsorbing the impurities can be used in the filter portion. The filter portion is provided with a heating means for enhancing the elimination of the impurities adsorbed in the filter portion, and can be recovered during operation.