Thermal storage facility especially suitable for concentrating solar power installations

Abstract

A thermal storage facility stores thermal energy at elevated temperature. The facility includes an enclosure for retaining a thermal storage medium; primary heat transfer surfaces for transferring heat from a circulating heat transfer fluid; and secondary heat transfer surfaces for transferring heat from the thermal storage medium to steam pipes associated with a power generation facility. The thermal storage medium is a metallic phase change material, preferably having a melting temperature above 500° C., interposed between the primary heat transfer surfaces and the secondary heat transfer surfaces. Solar power installations can incorporate one or more of the thermal storage facilities.

1 . A thermal storage facility for storing thermal energy at an elevated temperature, the facility comprising an enclosure configured to retain a thermal storage medium, primary heat transfer surfaces configured to transfer heat from a circulating heat transfer fluid, and secondary heat transfer surfaces configured to transfer heat from the thermal storage medium to steam pipes associated with a power generation facility, wherein the thermal storage medium is a metallic phase change material that is interposed between the primary heat transfer surfaces and the secondary heat transfer surfaces and wherein the heat transfer fluid is a liquid metal. 
     
     
         2 . A thermal storage facility as claimed in  claim 1 , wherein the metallic phase change material has high thermal conductivity, a high latent heat of fusion with and a high melting temperature. 
     
     
         3 . A thermal storage facility as claimed in  claim 2 , wherein the melting temperature of the metallic phase change material is above 500° C. 
     
     
         4 . A thermal storage facility as claimed in  claim 3 , wherein the metallic phase change material is selected from the group consisting of an alloy of aluminium and silicon comprising 87.76% Al and 12.24% Si, and an alloy comprising 83.14% Al, 11.7% Si and 5.16% Mg. 
     
     
         5 . A thermal storage facility as claimed in  claim 1 , wherein the metallic heat transfer fluid is liquid over an extended range of temperatures from ambient temperature through to a maximum operating temperature in excess of the melting point of the metallic phase change material. 
     
     
         6 . A thermal storage facility as claimed in  claim 5 , wherein the metallic heat transfer fluid is selected from the group consisting of a molten alkali metal and an alloy of alkali metals. 
     
     
         7 . A thermal storage facility as claimed in  claim 6 , wherein the metallic heat transfer fluid is an alloy of sodium and potassium. 
     
     
         8 . A thermal storage facility as claimed in  claim 1 , wherein the heat transfer surfaces are surfaces of generally parallel pipes extending through or adjacent the enclosure. 
     
     
         9 . A thermal storage facility as claimed in  claim 1 , wherein the thermal storage facility forms part of a unit selected from the group consisting of a pre-heater, a boiler, a super-heater, a re-heater and a combination unit designed to perform the function of any two or more of such units. 
     
     
         10 . A solar power installation having a single heliostat field and associated solar receiver mounted on a tower, wherein a thermal storage facility according to  claim 1  is built into the tower. 
     
     
         11 . A solar power installation comprising multiple heliostat fields with associated solar receivers carried on towers, wherein each of the solar receivers are connected to one or more common thermal storage facility as defined in  claim 1 , wherein the thermal storage facility is embodied in any one or more units selected from the group consisting of a pre-heater, a boiler, a super-heater, and a re-heater, and wherein the flow of heat transfer fluid to each of the facilities is controlled to achieve an objective of the one or more units.