Patent ID: 8473226

Claim:
A method of determining an average degree of saturation with ammonia (X) of a solid ammonia storage medium porous or not and capable of ad- or absorbing and desorbing ammonia reversibly in a storage container having a container volume (V con ) and essentially free of gases other than gaseous ammonia, wherein a part of the container volume (V con ) is occupied by said ammonia having a pressure (p) and defines a free volume (V free ), said storage container having at least one opening through which ammonia flows out of the storage container with a flow (f), wherein the free volume ( V free), the pressure (p) and the flow (f) vary with time (t), the method comprising: sampling n pairs ((f i ,p i ) (F i ,p i )) of flows (f i ), or accumulated flows (F i ), and pressures (p i ) at a sequence of points of time (t i ), i=1 . . . n and n≧2; determining an estimate volume value (V fit ) on the basis of the sampled pairs ((f i ,p i ) (F i ,p i )); and determining the average degree of saturation with ammonia (X) of the solid ammonia storage medium by applying a predetermined relationship (Rel) between a plurality of estimate volume values (V fit ) and a plurality of values of the average degree of saturation with ammonia (X) of the solid ammonia storage medium to the determined estimate volume value (V fit ); wherein said method is carried out by a computer system or an electronic control unit.