Packed rock bed thermal energy storage facility

Abstract

A packed rock bed thermal energy storage facility is provided in the form of a pile of unconstrained rock that is free to expand and contract with changing temperature without creating significant stress. A hot fluid inlet and outlet space is provided above the bed and a cold fluid inlet and outlet space is formed by a grid and larger rocks, or by larger rocks only, that support the pile toward a bottom of the bed. Fluid flow can occur downward through the rock bed during heating of the bed and upward through the rock bed during cooling of the bed in a heat recovery cycle. The bed is completely covered by an insulated arched roof. The rock bed may be an enclosure having a roof, walls and a floor with a lower central region and somewhat inclined side regions extending at a gentle slope towards sidewalls supporting the roof.

1 . A packed rock bed thermal energy storage facility comprising a pile of unconstrained rock that is free to expand and contract with changing temperature without creating significant stress; and with a hot fluid inlet and outlet space above the bed and a cold fluid inlet and outlet space that is supported by a grid and larger rocks, or by larger rocks only, toward a bottom of the bed, between which fluid flow can occur downward during heating of the bed and upward during cooling of the bed, the bed being completely covered by an insulated arched roof. 
     
     
         2 . A packed rock bed thermal energy storage facility comprising first and second spaces separated by a rock bed of individual rock units such that working fluid may flow between the first and second spaces by way of interstices between rock units forming the rock bed in order to provide for the transfer of heat to or from the rock bed, in use, and at least one communication duct associated with each of the first and second spaces for a working fluid to flow into or out of the first and second spaces, wherein the rock bed is in the form of a pile of rocks with the first space being formed between an upper surface of the pile and an enclosure spaced upwardly from the upper surface of the pile, and the second space is formed generally towards the bottom of the pile of rocks. 
     
     
         3 . A packed rock bed thermal energy storage facility as claimed in  claim 2  in which the enclosure has a roof, walls and a floor. 
     
     
         4 . A packed rock bed thermal energy storage facility as claimed in  claim 3  in which the floor has a lower central region and somewhat inclined side and end regions extending upwards at a gentle slope towards low sidewalls that support the roof, or towards end walls. 
     
     
         5 . A packed rock bed thermal energy storage facility as claimed in  claim 3  in which the first enclosed space is defined by an upper surface of the rock pile and the roof. 
     
     
         6 . A packed rock bed thermal energy storage facility as claimed in  claim 3  in which the second enclosed space is defined by a surface of an inner chamber in the form of one or more passages or tunnels defined by a part of a bottom surface of the rock pile and a part of a floor of the enclosure. 
     
     
         7 . A packed rock bed thermal energy storage facility as claimed in  claim 6  in which the bottom surface of the rock pile includes a support grid and larger rocks to support the rocks of the packed bed and maintain the second space. 
     
     
         8 . A packed rock bed thermal energy storage facility as claimed in  claim 2  in which one or both of the first and second spaces have associated therewith at least two or more communication ducts that may be used selectively for a thermal energy absorption process and a thermal energy usage process. 
     
     
         9 . A packed rock bed thermal energy storage facility as claimed in  claim 2  in which the rock bed consists of rocks selected from rock types being granite, dolerite, gneiss and hornfels. 
     
     
         10 . A packed rock bed thermal energy storage facility as claimed in  claim 1  in which the rocks are of generally similar size and within the range of from 10 to 50 mm in size. 
     
     
         11 . A packed rock bed thermal energy storage facility as claimed in  claim 1  in which the rocks are either rounded or crushed. 
     
     
         12 . A packed rock bed thermal energy storage facility as claimed in  claim 1  in which the rock pile has a flat top and sides that slope downwards at a natural angle of repose.