Thermal energy storage facility

Abstract

A thermal energy storage facility is provided that consists of a packed bed with an essentially unconstrained outer region and a duct having a heat exchange end region located within a central lower region of the packed bed and a fluid supply end opposite the heat exchange end region. The heat exchange end region of the duct permits heat transfer fluid at an elevated temperature to pass from the duct to the packed bed during a charge cycle to heat the packed bed from an inner region outwards. The heat transfer fluid is drawn from the packed bed into the duct during a discharge cycle.

1 . A thermal energy storage facility comprising a packed bed having an essentially unconstrained outer region and a duct communicating with an interior of the packed bed and having an external fluid supply end wherein the duct has a heat exchange end region located within a central lower region of the packed bed and has apertures over the heat exchange end region so as to permit heat transfer fluid at an elevated temperature in excess of 500° C. travelling into the duct via the fluid supply end to pass from the duct to an interior of the packed bed to heat the packed bed from an inner region of the packed bed outwards during a charge cycle, and, during a discharge cycle, permitting heat transfer fluid to be drawn through a charged packed bed into the heat exchange end region of the duct at an elevated temperature such that it exits the fluid supply end of the duct in a heated condition. 
     
     
         2 . The thermal energy storage facility as claimed in  claim 1 , wherein the fluid supply end is located at or near a top region of the packed bed or underneath the packed bed, and wherein the heat transfer fluid exits the duct via the fluid supply end during the discharge cycle. 
     
     
         3 . The thermal energy storage facility as claimed in  claim 1 , wherein an external surface of the packed bed is substantially exposed to the environment. 
     
     
         4 . The thermal energy storage facility as claimed in  claim 1 , which includes one or more protecting structures for protecting the packed bed from rain or wind. 
     
     
         5 . The thermal energy storage facility as claimed in  claim 1 , wherein the duct is defined by a pipe of substantially rigid material having the heat exchange end region and the fluid supply end opposite the heat exchange end region, the duct extending at least partially and generally vertically through a central region of the packed bed with the heat exchange end region located within a lower region of the packed bed. 
     
     
         6 . The thermal energy storage facility as claimed in  claim 1 , wherein the apertures span between about 20% to about 50% of the height of the packed bed. 
     
     
         7 . The thermal energy storage facility as claimed in  claim 5 , wherein the duct is manufactured from one or more high temperature alloys, preferably steel, and/or concrete or for the duct to consist of element-filled steel gabion bags, and for the elevated temperature to be between 500° C. and 1500° C. 
     
     
         8 . The thermal energy storage facility as claimed in  claim 1  wherein the fluid supply end of the duct is located at or near a top region of the packed bed in which instance elements are packed such that the packed bed and duct together to have a frustum-like shape. 
     
     
         9 . The thermal energy storage facility as claimed in  claim 1  wherein the fluid supply end of the duct is located beneath the packed bed in which instance the packed bed is packed such that the packed bed and duct together have a generally conical or pyramidal shape. 
     
     
         10 . The thermal energy storage facility as claimed in  claim 1  wherein the packed bed is in the form of an elongate mound having at least an upper region of triangular or truncated triangular shape in cross-section wherein the heat exchange end region of the duct is located in an inner lower region of the packed bed. 
     
     
         11 . The thermal energy storage facility as claimed in  claim 1  wherein elements of the packed bed are packed in a generally undisturbed pile, the pile sloping downwards at its natural angle of repose which ranges between 25° and 65°. 
     
     
         12 . The thermal energy storage facility as claimed in  claim 1  wherein elements of the packed bed are natural rock in the form of granite, gneiss or dolerite. 
     
     
         13 . The thermal energy storage facility as claimed in  claim 1  wherein the height of the packed bed is between 1 m and 60 m, the diameter of the duct is between 0.2 m and 15 m, and the packed bed has a volume of from 1 m 3  to 300000 m 3 . 
     
     
         14 . The thermal energy storage facility as claimed in  claim 1 , including a thermal energy source and, a thermal energy load in fluid communication with the thermal energy source and wherein the thermal energy storage facility is for storing thermal energy produced by the thermal energy source so as to supply the thermal energy load during times in which the thermal energy source may have a reduced output. 
     
     
         15 . (canceled) 
     
     
         16 . The thermal energy storage facility as claimed in  claim 14 , wherein the thermal energy source is a concentrating solar power plant. 
     
     
         17 . The thermal energy storage facility as claimed in  claim 14  in which a blower or fan is provided for urging heat transfer fluid towards the duct during the charge cycle and/or for urging heat transfer fluid towards the thermal energy load during the discharge cycle. 
     
     
         18 . A method of constructing a thermal energy storage facility according to  claim 1  comprising the steps of erecting a duct having a heat exchange end region and a fluid supply end opposite the heat exchange end region and packing a packed bed around the duct without substantially constraining the packed bed, the packed bed sloping downwards at its natural angle of repose wherein the heat exchange end region of the duct is located in an inner lower region of the packed bed.