Methods and Apparatus for Thermal Energy Storage Control Optimization

Abstract

Concentrating solar power (CSP) systems and methods are disclosed featuring the use of a solid-liquid phase change heat transfer material (HTM). The systems and methods include a solar receiver configured to receive concentrated solar flux to heat a quantity of the solid HTM and cause a portion of the solid HTM to melt to a liquid HTM. The systems and methods also include a heat exchanger in fluid communication with the solar receiver. The heat exchanger is configured to receive liquid HTM and provide for heat exchange between the liquid HTM and the working fluid of a power generation block. The heat exchanger further provides for the solidification of the liquid HTM. The systems and methods also include a material transport system providing for transportation of the solidified HTM from the heat exchanger to the solar receiver.

What is claimed is: 
     
         1 . A method of utilizing solar energy comprising:
 providing a heat transfer fluid circuit having heat transfer fluid flowing therein, the heat transfer fluid circuit being in thermal communication with:
 a solar energy concentrator, 
 a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material, and 
 a power block; 
   flowing heat transfer fluid from a solar energy concentrator inlet to a solar energy concentrator outlet, causing the heat transfer fluid to be heated with concentrated solar energy;   while producing energy with the power block, flowing heat transfer fluid from the solar energy concentrator outlet through a bucket of phase change material causing heat exchange between the heat transfer fluid and the phase change material; and   flowing heat transfer fluid from the bucket through the power block causing heat exchange between the heat transfer fluid and water in a steam circuit associate with the power block.   
     
     
         2 . The method of utilizing solar energy of  claim 1  wherein the bucket is a high temperature bucket containing a phase change material that has a melting temperature greater than the phase change materials contained in other buckets of the cascaded series. 
     
     
         3 . A solar power generation system comprising:
 a heat transfer fluid circuit providing for the flow of heat transfer fluid therein;   a solar energy concentrator in thermal communication with the heat transfer fluid circuit;   a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material in thermal communication with the heat transfer fluid circuit; wherein an inlet to a first bucket of the thermal energy storage system is in direct communication through the heat transfer fluid circuit with an outlet from the solar energy concentrator; and   a power block wherein an inlet to the power block is in direct communication through the heat transfer fluid circuit with an outlet from the first bucket of the thermal energy storage system causing heat to be transferred from heat transfer fluid flowing into the power block to water in a steam circuit associated with the power block.   
     
     
         4 . The solar power generation system of  claim 3  wherein the first bucket comprises a high temperature bucket containing a phase change material that has a melting temperature greater than the phase change materials contained in other buckets of the cascaded series. 
     
     
         5 . The solar power generation system of  claim 3  wherein the outlet from the first bucket is also in direct communication through the heat transfer fluid circuit with an inlet to another bucket of the thermal energy storage system. 
     
     
         6 . A cascaded thermal energy storage system comprising:
 a heat transfer fluid circuit having heat transfer fluid flowing therein;   multiple buckets connected in series by the heat transfer fluid circuit with each bucket containing a quantity of a phase change material;   a heat exchanger associated with each bucket and the heat transfer fluid circuit such that heat may be exchanged between the heat transfer fluid and the phase change material in each bucket; and   a secondary branch of the heat transfer fluid circuit connecting an outlet of one or more buckets directly to a power block inlet while producing energy with the power block.   
     
     
         7 . A method of preheating a solar energy system comprising:
 providing a solar energy plant comprising a heat transfer fluid circuit having heat transfer fluid flowing therein, the heat transfer fluid circuit being in thermal communication with:
 a solar energy concentrator, and 
 a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material, and 
 a power block; 
   after complete discharge of at least one bucket of the thermal energy storage system but prior to charging the thermal energy storage system, flowing heat transfer fluid from a power block outlet through one or more not fully discharged buckets of the thermal energy storage system causing heat exchange between the phase change materials in the one or more buckets and the heat transfer fluid; and   flowing preheated heat transfer fluid from the one or more buckets to at least one of the solar energy concentrator and the power block.   
     
     
         8 . The method of preheating a solar energy system of  claim 7  wherein the one or more buckets of the thermal energy storage system receiving heat transfer fluid from the power block are colder temperature buckets containing a phase change material that has a lower melting temperature than the phase change materials contained in at least one other bucket of the cascaded series. 
     
     
         9 . A solar power generation system comprising:
 a heat transfer fluid circuit providing for the flow of heat transfer fluid therein;   a solar energy concentrator in thermal communication with the heat transfer fluid circuit; and   a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material in thermal communication with the heat transfer fluid circuit; wherein an inlet to one or more buckets of the thermal energy storage system is in direct communication through the heat transfer fluid circuit with an outlet from a power block; and an outlet from the one or more buckets of the thermal energy storage system is in direct communication through the heat transfer fluid circuit with at least one of the solar energy concentrator and an inlet to the power block, causing heat transfer fluid flowing in the heat transfer fluid circuit to be preheated after at least one bucket of the thermal energy storage system has been discharged but before the thermal energy system is charged.   
     
     
         10 . The solar power generation system of  claim 9  wherein the one or more buckets of the thermal energy storage system in communication with the power block outlet are colder temperature buckets containing a phase change material that has a lower melting temperature than the phase change materials contained in at least one other bucket of the cascaded series. 
     
     
         11 . A cascaded thermal energy storage system comprising:
 a heat transfer fluid circuit having heat transfer fluid flowing therein;   multiple buckets connected in series by the heat transfer fluid circuit with each bucket containing a quantity of a phase change material;   a heat exchanger associated with each bucket and the heat transfer fluid circuit such that heat may be exchanged between the heat transfer fluid and the phase change material in each bucket; and   a secondary branch of the heat transfer fluid circuit connecting an outlet from a power block to an inlet to one or more buckets of the cascaded thermal energy storage system after discharge of the thermal energy storage system but prior to charging the thermal energy storage system.   
     
     
         12 . A method of utilizing solar energy comprising:
 providing a heat transfer fluid circuit having heat transfer fluid flowing therein, the heat transfer fluid circuit being in thermal communication with:
 a solar energy concentrator, 
 a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material wherein each bucket contains a phase change material having a selected melting temperature, and 
 a power block comprised of multiple steam train components wherein each steam train component has a designed operating temperature; and 
   while discharging the thermal energy storage system, flowing heat transfer fluid from a first selected bucket of phase change material to the inlet of a corresponding first steam train component and flowing heat transfer fluid from a second selected bucket of phase change material to the inlet of a corresponding second steam train component, causing heat exchange between the heat transfer fluid and water in a steam circuit associated with each of the selected steam train components.   
     
     
         13 . The method of utilizing solar energy of  claim 12  wherein the melting temperature of the phase change material in the first bucket corresponds to the designed operating temperature of the first steam train component and the melting temperature of the phase change material in the second bucket corresponds to the designed operating temperature of the second steam train component. 
     
     
         14 . The method of utilizing solar energy of  claim 12  wherein the melting temperature of the phase change material in the first bucket is approximately equal to the designed operating temperature of the first steam train component and the melting temperature of the phase change material in the second bucket is approximately equal to the designed operating temperature of the second steam train component. 
     
     
         15 . A solar power generation system comprising:
 a heat transfer fluid circuit providing for the flow of heat transfer fluid therein;   a solar energy concentrator in thermal communication with the heat transfer fluid circuit;   a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material in thermal communication with the heat transfer fluid circuit; and   a power block comprised of multiple steam train components linked by a steam circuit, wherein a heat transfer fluid circuit outlet from at least first and second buckets of the thermal energy storage system are in direct communication with a heat transfer fluid circuit inlet to at least corresponding first and second steam train components.   
     
     
         16 . The solar power generation system of  claim 15  wherein the melting temperature of the phase change material in the first bucket corresponds to the designed operating temperature of the first steam train component and the melting temperature of the phase change material in the second bucket corresponds to a designed operating temperature of the second steam train component. 
     
     
         17 . The solar power generation system of  claim 15  wherein the melting temperature of the phase change material in the first bucket is approximately equal to the designed operating temperature of the first steam train component and the melting temperature of the phase change material in the second bucket is approximately equal to a designed operating temperature of the second steam train component. 
     
     
         18 . A cascaded thermal energy storage system comprising:
 a heat transfer fluid circuit having heat transfer fluid flowing therein;   multiple buckets connected in series by the heat transfer fluid circuit with each bucket containing a quantity of a phase change material;   a heat exchanger associated with each bucket and the heat transfer fluid circuit such that heat may be exchanged between the heat transfer fluid and the phase change material in each bucket; and   multiple secondary branches of the heat transfer fluid circuit connecting an outlet from at least a first and second bucket to an inlet to at least a first and second steam train component during discharge of the thermal energy storage system.   
     
     
         19 . The cascaded thermal energy storage system of  claim 18  wherein the melting temperature of the phase change material in the first bucket corresponds to a designed operating temperature of the first steam train component and the melting temperature of the phase change material in the second bucket corresponds to a designed operating temperature of the second steam train component. 
     
     
         20 . The cascaded thermal energy storage system of  claim 18  wherein the melting temperature of the phase change material in the first bucket is approximately equal to the designed operating temperature of the first steam train component and the melting temperature of the phase change material in the second bucket is approximately equal to a designed operating temperature of the second steam train component. 
     
     
         21 . A method of utilizing solar energy comprising:
 providing a heat transfer fluid circuit having heat transfer fluid flowing therein, the heat transfer fluid circuit being in thermal communication with:
 a solar energy concentrator, 
 a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material, and 
 a power block; 
   during periods of insolation too low to charge the thermal energy storage system, partially discharging the thermal energy storage system by flowing heat transfer fluid from a power block outlet through one or more buckets of the thermal energy storage system causing heat exchange between the phase change materials in the one or more buckets and the heat transfer fluid; and   flowing preheated heat transfer fluid from the one or more bucket through the solar energy concentrator to the power block causing heat exchange between the heat transfer fluid and water in a steam circuit associate with the power block.   
     
     
         22 . The method of utilizing solar energy of  claim 21  wherein the one or more buckets of the thermal energy storage system receiving heat transfer fluid from the power block are colder temperature buckets containing a phase change material that has a lower melting temperature than the phase change materials contained in other buckets of the cascaded series. 
     
     
         23 . A solar power generation system comprising:
 a heat transfer fluid circuit providing for the flow of heat transfer fluid therein;   a solar energy concentrator in thermal communication with the heat transfer fluid circuit; and   a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material in thermal communication with the heat transfer fluid circuit; wherein an inlet to one or more buckets of the thermal energy storage system is in direct communication through the heat transfer fluid circuit with an outlet from a power block; and an outlet from the one or more buckets of the thermal energy storage system is in direct communication through the heat transfer fluid circuit with the solar energy concentrator and an inlet to the power block thereby causing heat transfer fluid flowing in the heat transfer fluid circuit to be heated by partial discharge of the thermal energy storage system during periods of insufficient insolation to charge the thermal energy storage system.   
     
     
         24 . The solar power generation system of  claim 23  wherein the one or more buckets of the thermal energy storage system in communication with the power block outlet are colder temperature buckets containing a phase change material that has a lower melting temperature than the phase change materials contained in other buckets of the cascaded series. 
     
     
         25 . A cascaded thermal energy storage system comprising:
 a heat transfer fluid circuit having heat transfer fluid flowing therein;   multiple buckets connected in series by the heat transfer fluid circuit with each bucket containing a quantity of a phase change material;   a heat exchanger associated with each bucket and the heat transfer fluid circuit such that heat may be exchanged between the heat transfer fluid and the phase change material in each bucket; and   a secondary branch of the heat transfer fluid circuit connecting an outlet from a power block to an inlet to one or more buckets of the cascaded thermal energy storage system during periods of insufficient insolation to charge the thermal energy storage system.   
     
     
         26 . The cascaded thermal energy storage system of  claim 25  wherein the one or more buckets of the thermal energy storage system in communication with the power block outlet are colder temperature buckets containing a phase change material that has a lower melting temperature than the phase change materials contained in other buckets of the cascaded series. 
     
     
         27 . A solar power generation system comprising:
 a heat transfer fluid circuit providing for the flow of heat transfer fluid therein;   a solar energy concentrator in thermal communication with the heat transfer fluid circuit;   a thermal energy storage system comprising a cascaded series of multiple buckets of phase change material in thermal communication with the heat transfer fluid circuit;   a power block in thermal communication with the heat transfer fluid circuit the power block being comprised of multiple steam train components in thermal communication with a steam circuit; and   a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and a steam train component or a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and the solar field.   
     
     
         28 . The solar power generation system of  claim 27  further comprising a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and a steam train component and a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and the solar field. 
     
     
         29 . The solar power generation system of  claim 27  further comprising multiple secondary branches of the heat transfer fluid circuit extending between selected phase change material buckets and one or more steam train components and multiple secondary branches of the heat transfer fluid circuit extending between selected phase change material buckets and the solar field. 
     
     
         30 . A cascaded thermal energy storage system comprising:
 a heat transfer fluid circuit having heat transfer fluid flowing therein;   multiple buckets connected in series by the heat transfer fluid circuit with each bucket containing a quantity of a phase change material;   a heat exchanger associated with each bucket and the heat transfer fluid circuit such that heat may be exchanged between the heat transfer fluid and the phase change material in each bucket; and   a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and a steam train component or a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and the solar field.   
     
     
         31 . The cascaded thermal energy storage system of  claim 30  further comprising a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and a steam train component and a secondary branch of the heat transfer fluid circuit extending between a phase change material bucket and a solar field. 
     
     
         32 . The cascaded thermal energy storage system of  claim 30  further comprising multiple secondary branches of the heat transfer fluid circuit extending between selected phase change material buckets and one or more steam train components and multiple secondary branches of the heat transfer fluid circuit extending between selected phase change material buckets and a solar field.