TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: Alternatively, generating hydrogen from the hydride being hydrolyzed in the reaction chamber in the exothermic reaction by the addition of water, where the water supply rate in relation to the hydrogen generated is controlled according to a value x being defined by any of the following four equations: MH + xH2O to produce (1-x)M2O + (2x-1) MOH + H2; M symbolizing a valent metal, x being in the interval of 0.51-0.9; MH2 + xH2O to produce (2-x)MO + (x-1)M(OH)2 + 2H2, M symbolizing a divalent metal, x being in the interval of 1.02-1.8; MH3 + x H2O to produce (1-1/3 x) M2O3 + (2/3 x-1) M(OH)3 + 3H2, M symbolizing a 3-valent metal, x being in the interval of 1.5-3; MH4 + xH2O to produce (2-1/2 x) MO2 + (1/2 x-1) M(OH)4 + 4H2, M symbolizing a 4-valent metal, x being in the interval of 2.04-3.6. For a divalent metal, x is in the interval of 1.1-1.45, preferably in the interval of 1.2-1.3. The hydride is magnesium hydride (MgH2). The hydride is in the form of a granular material having an average particle size of less than 50 mu m and preferably of not more than 10 mu m. The granular packing density is between 0.4 g/cm3 and 0.7 g/cm3. The flow of the hydrogen generated is kept not to exceed 9 normal liter per kg of still un-reacted hydride contained in the reaction chamber, and preferably is less than 3.5 normal liter, normal liter meaning at 1013 mbar and 0 degrees C. The water supply rate is controlled by influencing the temperature in the reaction chamber. The water supply rate is controlled in dependency of the pressure of the hydrogen generated, or in dependency of the water vapor partial pressure in the reaction chamber. For starting of the reaction, the reaction chamber is pre-heated, where pre-heating is carried out electrically by resistance wires. Also, pre-heating is carried out chemically by reacting phosphorus-pentoxide deposited in the reaction chamber and water in an exothermic reaction. The water to be supplied to the reaction chamber is heated before entering the reaction chamber. The reaction chamber is cooled and the excess heat is used to heat the water to be supplied. The stock of water, contained in a water storage vessel applied to the reaction chamber for supplying it with water, an anti-freezing additive is injected. Preferred Generator: In the hydrogen generator, in series with the water supply inlet within the reaction chamber a porous material is arranged, that is permeable to steam but not permeable to the hydride and preferably also not permeable to liquid. The hydrogen generator comprises a reaction chamber, a water supply inlet into the reaction chamber and a hydrogen outlet from the reaction chamber, where the reaction chamber is surrounded by a thermal insulation, having a non-linear insulation characteristic with a high thermal resistance at low temperature and a low thermal resistance at high temperature. The non-linear thermal isolation is realized by vacuum insulation, permeable to thermal radiation. Furthermore, the hydrogen generator comprises a reaction chamber, a water supply inlet into the reaction chamber and a hydrogen outlet from the reaction chamber, where the hydrogen generator comprises a water storage vessel, an inlet connected to the hydrogen outlet of the reaction chamber, a water outlet connected via a pump to the water supply inlet into the reaction chamber and a hydrogen outlet, where the water storage vessel has a volume larger than the amount of water to be stored, and the hydrogen outlet is connected to a hydrogen collecting body within the vessel, having a porous wall which is permeable to hydrogen and impermeable to liquid water. The hydrogen collecting body comprises a tube of porous polytetrafluoroethylene, the tube being formed as a coil penetrating through the complete volume of the vessel so as to allow a part of it being above the water level in all orientations of the vessel. The water outlet within the vessel is connected to a hose open at its far end and having a weight at its far end, the hose being as long as to reach the most distant area in the vessel. Alternatively, the hydrogen generator for the performing the method comprises a reaction chamber, a water supply inlet into the reaction chamber and a hydrogen outlet from the reaction chamber, where the hydrogen generator is connected to a fuel cell powering a load, for supplying hydrogen to the fuel cell. The electric power output of the fuel cell is dimensioned to be higher than the maximum power demand of the load. The fuel cell is also connected to an electrical buffer for powering it. The fuel cell is connected to a water storage vessel applied to the reaction chamber for supplying it with water, for feeding product water into the storage vessel. In a second alternative case, the hydrogen generator for performing the method comprises a reaction chamber, a water supply inlet into the reaction chamber and a hydrogen outlet from the reaction chamber, where the reaction chamber is designed as a replaceable cartridge. Also a water storage vessel applied to the reaction chamber for supplying it with water is designed as replaceable cartridge, preferably integral with the reaction chamber.