Encapsulated phase change apparatus for thermal energy storage

Abstract

Provided are apparatus and methods for storing thermal energy. For example, an apparatus including comprising at least one phase change material, and a capsule containing the at least one phase change material. The capsule may be permanently or temporarily sealed to contain the encapsulation material. The encapsulation material includes at least one material that is chemically and physically distinct from the phase change material. The encapsulation material and phase change material are selected to store and discharge thermal energy at temperatures of greater than 400° C. without capsule failure.

1 . An apparatus for storing thermal energy, the apparatus comprising:
 at least one phase change material;   a capsule containing the at least one phase change material, wherein the capsule comprises an encapsulation material, and wherein the encapsulation material comprises at least one material that is chemically and physically distinct from the phase change material, and wherein the encapsulation material and phase change material are selected to store and discharge thermal energy at temperatures of greater than 450° C. without capsule failure.   
     
     
         2 . The apparatus of  claim 1 , wherein the capsule comprises an inner chamber for containing the at least one phase change material. 
     
     
         3 . The apparatus of  claim 1 , wherein the capsule comprises a layer of encapsulation material deposited onto the surface of the phase change material. 
     
     
         4 . The apparatus of  claim 2 , wherein the inner chamber is substantially completely filled with the phase change material when the phase change material reaches a first preselected operating temperature. 
     
     
         5 . The apparatus of  claim 4 , wherein the inner chamber is filled to less than about 90 percent of its volume by the phase change material at the first preselected temperature. 
     
     
         6 . The apparatus of  claim 5 , wherein the preselected temperature is at least about 308° C. 
     
     
         7 . The apparatus of  claim 5 , wherein the preselected temperature is at least about 444° C. 
     
     
         8 . The apparatus of  claim 5 , wherein the preselected temperature is about 725° C. 
     
     
         9 . The apparatus of  claim 5 , wherein the inner chamber is not substantially completely filled with the phase change material when the phase change material reaches a second preselected temperature, the second preselected temperature being lower than the first preselected temperature. 
     
     
         10 . The apparatus of  claim 1 , wherein the phase change material comprises Zinc, and wherein the encapsulation material comprises Nickel. 
     
     
         11 . The apparatus of  claim 1 , wherein the phase change material comprises at least one of stainless steel and MgCl 2 —NaCl eutectic salts, and wherein the encapsulation material comprises at least one of carbon steel or stainless steel. 
     
     
         12 . The apparatus of  claim 1 , wherein the phase change material comprises at least one of NaNO 3 , KNO 3 , NaNO 3 —KNO 3 , MgCl 2 , MgCl 2 —NaCl, MgCl 2 —KCl, NaCl-KCl, and combinations thereof. 
     
     
         13 . The apparatus of  claim 9 , wherein a plurality of capsules are provided to form a thermal energy storage system. 
     
     
         14 . The apparatus of  claim 13 , wherein the thermal energy storage system further comprises at least one fluid in thermal contact with the plurality of capsules, wherein the fluid serves conduct heat from an energy source to the capsules, thereby heating the phase change material to at least the first preselected temperature. 
     
     
         15 . The apparatus of  claim 14 , wherein the fluid is selected from the group consisting of air, silicones, biphenyls, eutectic salt mixtures such as NaNO 3 —KNO 3 , NaNO 3 —KNO 3 —LiNO 3 , and combinations thereof. 
     
     
         16 . The apparatus of  claim 15 , wherein the phase change material, encapsulation material, and heat transfer fluid are selected and arranged to enable storage of thermal energy for at least 6 hours at temperatures of at least about 450° C. 
     
     
         17 . The apparatus of  claim 16 , wherein the thermal energy comprises energy generated from at least one energy source, the energy source comprising at least one of solar, wind, geothermal, and nuclear, and combinations thereof. 
     
     
         18 . The apparatus of  claim 17 , wherein the efficiency of the system permits storage of thermal energy at less than about $40 kWh. 
     
     
         19 . The apparatus of  claim 1 , wherein the capsule comprises an opening that can be operated to adjust the amount of phase change material contained therein. 
     
     
         20 . The apparatus of  claim 1 , wherein the capsule includes a void space that is determined based upon the thermal and physical properties of the phase change material, the thermal and physical properties of the encapsulation material, and the geometric shape of the capsule.