High temperature thermal energy storage system

Abstract

High temperature thermal energy storage system comprised of solid-liquid phase change material that is fully encapsulated in helically grooved, sealed, thin-wall, metal tubes. Multitude of horizontally oriented, pressure-rated steam pipes or vessels filled with PCM tube capsules form a battery of thermal storage system. The steam pipes in the battery are connected through a common liquid-side distribution header system and a common steam-side distribution header system. Multitude of steam pipes stacked up to fill a block-shaped container space. This insulated enclosure provides the basis for simple fabrication, transport and filed-erection and forms the basic building block for a modular thermal storage system.

I claim: 
     
         1 . A helically or axially grooved metal tube capsule wherein the ratio of the length to the diameter of the tube is from 6 to 300 and wherein the capsule may be formed from a thin wall tube and wherein the helical grooving along the length of the tubes may be formed by rolling or other metal-forming procedure and wherein the grooved tubes may resemble the rifled barrel of guns and wherein the profile of the groove is curved to facilitate radial and axial flexibility of the tube-capsule and wherein the number of the grooves on the tube may be from 2 to 12 and wherein the ratio of the depth of the groove to the diameter of the tube may be from 0.02 to 0.4 and wherein the angle between the tangent of the helix of the grooves and the axis of the tube may be from 0 to 30 degrees. 
     
     
         2 . The helically or axially grooved metal tube capsule of  claim 1  wherein the inside of the tube has heat transfer fins to promote the heat transfer in radial direction and wherein the fins extend in radial direction from circumference toward the center of the tube and extend in axial direction along the length of the tube and wherein the fins may be integral part of the wall manufactured by extrusion or similar process along with the wall of the tube or the fins may be inserted separately in the tube and pressed against the inside wall during the plastic deformation process of grooving. 
     
     
         3 . The helically or axially grooved metal tube capsule of  claim 1  wherein the tube is filled with a molten phase change material and hermetically sealed to complete the encapsulation and wherein the phase change material may or may not have eutectic properties and it may be a mixture of two or more molten-salt compounds such as Sodium Nitrate, Sodium Nitrite, Sodium Chlorate, Potassium Nitrate, Sodium Hydroxide, Potassium Bi-fluoride, Sodium Peroxide, Calcium Nitrate, etc. 
     
     
         4 . The bundle of sealed PCM tube capsules of  claim 1  filling a pressure rated steam-pipe or vessel wherein the free space between the grooved tube capsules is available for steam and condensate flow and wherein steam pipe or vessel has one or multiple steam ports and one or multitude of condensate/feedwater ports. 
     
     
         5 . The multitude of pressure rated steam-pipes or vessels of  claim 3  connected to form a battery wherein the steam pipes of the battery are connected through a common liquid-side distribution header system and a common steam-side distribution header system. 
     
     
         5 . The battery of steam-pipes or vessels of  claim 4  stacked up to fill a block-shaped container space wherein the battery is housed in a thermally insulated enclosure designed for structural integrity and wherein the battery enclosed in the housing forms one module of the high temperature thermal storage system.