Method for the commencement diagnosis of a heat storage material

Abstract

The invention relates to a method and an apparatus for detecting the point in time of commencement of crystallization of a heat storage material ( 40 ), in particular a latent heat storage material, which is supercooled by means of a Peltier element ( 32 ). The profile ( 10 ) of the current I of the Peltier element ( 32 ) is measured. The commencement of the crystallization process in the heat storage material ( 40 ) is deduced when a discontinuity ( 20, 22 ) which follows a continuous decrease ( 16 ) in the current and after which the current (I) increases again ( 18 ) is detected in the current profile ( 10 ).

1 . A method of detecting a point in time of commencement of crystallization of a supercoolable heat storage material ( 40 ), which is supercooled by a Peltier element ( 32 ), characterized in that a profile ( 10 ) of a current (I) of the Peltier element ( 32 ) is measured and a commencement of the crystallization process in the heat storage material ( 40 ) is deduced when a discontinuity ( 20 ,  22 ) in the profile ( 10 ) is detected. 
     
     
         2 . The method according to  claim 1 , characterized in that the heat storage material ( 40 ) is a latent heat storage material. 
     
     
         3 . The method according to  claim 1 , characterized in that the discontinuity in the profile ( 10 ) is an increase in the current I ( 18 ) following a continuous decrease ( 16 ) in the current I. 
     
     
         4 . The method according to  claim 1 , characterized in that the commencement of crystallization of the heat storage material ( 40 ) occurs as a result of local supercooling from a metastable state in a thermal equilibrium. 
     
     
         5 . The method according to  claim 4 , characterized in that the heat storage material ( 40 ) is a salt hydrate, 
     
     
         6 . The method according to  claim 1 , characterized in that a temperature difference between a hot side and a cold side of the Peltier element ( 32 ) increases and the current I decreases ( 16 ) during a period of time ( 12 ). 
     
     
         7 . The method according to  claim 1 , characterized in that a temperature increase in the heat storage material ( 40 ) occurs at the commencement of crystallization ( 22 ). 
     
     
         8 . The method according to  claim 1 , characterized in that the discontinuity ( 20 ) in the current profile ( 10 ) is detected, with a thermally produced delay, at a current sensor ( 30 ). 
     
     
         9 . An apparatus for carrying out the method according to  claim 1 , having a Peltier element ( 32 ) which locally supercools a heat storage material ( 40 ), of a latent heat store ( 38 ), characterized in that a power supply ( 44 ) to the Peltier element ( 32 ) has at least one current sensor ( 30 ). 
     
     
         10 . The method according to  claim 9 , characterized in that the heat storage material ( 40 ) is a phase change material. 
     
     
         11 . The method according to  claim 9 , characterized in that the Peltier element ( 32 ) is a single-stage element. 
     
     
         12 . The method according to  claim 9 , characterized in that the Peltier element ( 32 ) is a multistage element. 
     
     
         13 . An apparatus according to  claim 9 , characterized in that the at least one current sensor ( 30 ) is located in the power supply ( 44 ) to the Peltier element ( 32 ) 
     
     
         14 . An apparatus according to  claim 9 , characterized in that the at least one current sensor ( 30 ) is integrated into a control device ( 42 ).