A storage device for thermal energy

Abstract

A storage device for thermal energy includes a thermo-vector unit, and a thermo-accumulator unit. The thermo-vector unit includes one or more flow ducts for a working fluid. The thermo-accumulator unit includes a thermal storage material configured to operate in a thermal exchange relationship with the working fluid and for storing and releasing thermal energy due to a thermal exchange with the working fluid. The thermo-accumulator unit has a thermal diffusivity comprised between 10 and 150 mm2/s.

The invention claimed is: 
     
         1 . A storage device for thermal energy including:
 a thermo-vector unit, and   a thermo-accumulator unit   wherein:   said thermo-vector unit includes one or more flow ducts for working fluid,   said thermo-accumulator unit includes a thermal storage material configured for operating in a thermal exchange relationship with said working fluid and for storage and release of thermal energy as a consequence of a thermal exchange with said working fluid, said thermal storage material having a thermal diffusivity comprised between 10 and 150 mm 2 /s.   
     
     
         2 . The storage device according to  claim 1 , wherein said thermo-vector unit is embedded within said thermo-accumulator unit. 
     
     
         3 . The storage device according to  claim 2 , wherein said thermo-accumulator unit provides a matrix for one or more flow ducts of said thermo-vector unit. 
     
     
         4 . The storage device according to  claim 1 , wherein said thermo-vector unit includes a thermally conductive matrix through which said one or more flow ducts extend, wherein said matrix is in a thermal exchange relationship with said thermo-accumulator unit and it is, alternatively:
 embedded into said thermo-vector unit, or   in contact with the storage material of said thermo-accumulator unit.   
     
     
         5 . The storage device according to  claim 4 , wherein said thermo-vector unit is arranged externally to said thermo-accumulator unit. 
     
     
         6 . The storage device according to  claim 5 , wherein said matrix includes:
 a first plate   a second plate   a serpentine flow duct arranged between said first plate and said second plate,   each of said first and second plates being provided with grooves configured to define, upon matching said first and second plates, channels into which loop portions of said serpentine flow duct are housed.   
     
     
         7 . The storage device according to  claim 4 , including a first thermo-vector unit and a second thermo-vector unit arranged at opposite ends of said thermo-accumulator unit, wherein the matrix of each thermo-vector unit is in a thermal exchange relationship with the thermal storage material of said thermo-accumulator unit. 
     
     
         8 . The storage device according to  claim 1 , wherein the storage material of the thermo-accumulator unit comprises thermal interruptions transverse to a flow direction of the working fluid in the thermo-vector unit. 
     
     
         9 . The storage device according to  claim 1 , wherein said thermal storage material has a thermal diffusivity comprised between 35 and 120 mm 2 /s, and more preferably between 50 and 100 mm 2 /s. 
     
     
         10 . The storage device according to  claim 1 , wherein, named:
 L: characteristic dimension in a transverse/radial direction of the thermo-accumulator unit   L axial : length in the axial/longitudinal direction of the thermo-accumulator unit, said axial/longitudinal direction being a flow direction for said working fluid,   κ mat : thermal conductivity of the material of the thermo-accumulator unit,   S scambio : heat exchange surface between said flow ducts for the working fluid and the thermo-accumulator unit,   and defined:   Thermal resistance in the radial direction
     R   t,radial   ·L /( N·κ   mat   ·S   scambio ) 
   Thermal resistance in the axial/longitudinal direction
     R   t,axial =[ L   axial /(κ mat   ·L   2 )]
 
   the following applies:   (R t,radial /R t,axial )<0.2, preferably (R t,radial /R t,axial )<0.1, more preferably (R t,radial /R t,axial )<0.02.   
     
     
         11 . An array of storage devices for thermal energy including a plurality of storage devices for thermal energy according to  claim 1  hydraulically connected to each other, wherein the thermo-vector units of adjacent and hydraulically connected storage devices for thermal energy have a thermal interruption therebetween. 
     
     
         12 . The array of storage devices for thermal energy according to  claim 11 , wherein, named:
 L: characteristic dimension in a transverse/radial direction of the thermo-accumulator unit   L axial : length in the axial/longitudinal direction of the thermo-accumulator unit, said axial/longitudinal direction being a flow direction for said working fluid,   κ mat : thermal conductivity of the material of the thermo-accumulator unit,   κ int : thermal conductivity of the material forming the thermal interruption   S scambio : heat exchange surface between said flow ducts for the working fluid and the thermo-accumulator unit,   N: number of thermo-accumulator units in the array   N−1: number of thermal interruptions in the array   L int : length in the axial/longitudinal direction of the thermal interruption between two adjacent thermo-accumulator units   and defined:   Thermal resistance in the radial direction
     R   t,radial   ·L /( N·κ   mat   ·S   scambio ) 
   Thermal resistance in the axial/longitudinal direction
     R   t,axial   =N ·[ L   axial /(κ mat   ·L   2 )]+( N− 1)·[ L   int /(κ int   ·L   2 )]
 
   the following applies:   (R t,radial /R t,axial )<0.2, preferably (R t,radial /R t,axial )<0.1, more preferably (R t,radial /R t,axial )<0.02.