Dissociatiang solid-gas systems are promising for thermal storage and cold production in solar technology. Among them are classified ammoniates and crystal hydrates, hydroxides of alkali and alkali-earth metals, and certain other compounds. At present, studies have appeared which use metallic hydrides for these purposes. The latter are also promising material for storing hydrogen. Such absorbents are powders, therefore, gas fills the whole free volume of a layer and can be absorbed or desorbed at a high rate, with a corresponding thermal effect. It is shown that, as a consequence of poor heat transfer in the layer, a completely different sorption may be realized, when it proceeds in a narrow area near the front moving through the layer. A mathematical model of the sorption process is suggested applicable to calculation of the process in metallic hydrides used in a hydrogen storage cell, which works using a solar battery.