A method for controlling the effective heat transfer from a storage unit, wherein the storage unit contains a solid gas storage material, said method being carried out by using an apparatus comprising: a fluid gap between an outer encapsulation and the storage unit that provides an insulation layer when there is no active movement of the gaseous fluid in the fluid gap, or when there is no passive convection enabled; a fluid flow device creating forced convection of gaseous fluid being in contact with the surface of the storage unit to increase heat transfer from the storage unit, or a passive-convection control device enabling passive convection of gaseous fluid being in contact with the surface of the storage unit to increase heat transfer from the storage unit; an exit of the encapsulation where the gaseous fluid forced in convection by the fluid flow device, or the gaseous fluid with enabled passive convection, can exit; a heater to heat the storage material; wherein during gas release from the storage material, the storage material is heated by the heater, and during re-saturation of the storage material with gas, the heater is off; and wherein the controlling of the effective heat transfer from the storage unit is performed, during gas release, by ceasing operation of the fluid flow device, or by regulating the convection created by the fluid flow device such that it is lower than that during re-saturation, or by disabling passive convection by means of the passive-convection control device; and, during re-saturation, by operating the fluid flow device, or by regulating the convection created by the fluid flow device such that it is higher than that during gas release, or by enabling passive convection by means of the passive-convection control device, characterized in that said solid gas storage material is capable of reversible storage of ammonia by absorption, or adsorption, and desorption, and that the gas reversibly stored in the solid gas storage material is ammonia. a fluid gap between an outer encapsulation and the storage unit that provides an insulation layer when there is no active movement of the gaseous fluid in the fluid gap, or when there is no passive convection enabled; a fluid flow device creating forced convection of gaseous fluid being in contact with the surface of the storage unit to increase heat transfer from the storage unit, or a passive-convection control device enabling passive convection of gaseous fluid being in contact with the surface of the storage unit to increase heat transfer from the storage unit; an exit of the encapsulation where the gaseous fluid forced in convection by the fluid flow device, or the gaseous fluid with enabled passive convection, can exit; a heater to heat the storage material; wherein during gas release from the storage material, the storage material is heated by the heater, and during re-saturation of the storage material with gas, the heater is off; and wherein the controlling of the effective heat transfer from the storage unit is performed, during gas release, by ceasing operation of the fluid flow device, or by regulating the convection created by the fluid flow device such that it is lower than that during re-saturation, or by disabling passive convection by means of the passive-convection control device; and, during re-saturation, by operating the fluid flow device, or by regulating the convection created by the fluid flow device such that it is higher than that during gas release, or by enabling passive convection by means of the passive-convection control device, characterized in that said solid gas storage material is capable of reversible storage of ammonia by absorption, or adsorption, and desorption, and that the gas reversibly stored in the solid gas storage material is ammonia.