A system for storing ammonia in and releasing ammonia from a storage material capable of binding and releasing ammonia reversibly by adsorption or absorption for a process with a gradual ammonia demand that can vary over the time. The system has a container capable of housing the ammonia-containing storage material; a heating source arranged to supply heat for the desorption of ammonia from the solid storage medium; and a controller arranged to control the heating source to release ammonia. The heating source may be arranged inside the container and surrounded by ammonia storage material. A controllable dosing valve is arranged to dose released ammonia according to the ammonia demand. The controller comprises a feed-forward control arranged to control the heat supplied by the heating source, based on the ammonia demand.