Solar thermal combined heating, cooling, and power system and associated control methods

Abstract

A solar thermal combined heating and power system includes: a solar thermal array; a thermal energy storage unit; a generator unit configured to provide electrical power to the structure; an array-to-storage heat transfer device configured to transfer thermal energy from the solar thermal array to the thermal energy storage unit; a storage-to-generator heat transfer device configured to transfer thermal energy from the thermal energy storage unit to the generator unit; a storage-to-water heat transfer device configured to transfer thermal energy from the thermal energy storage unit to the water reservoir; a storage-to-air heat transfer device configured to transfer thermal energy from the thermal energy storage unit to the interior air of the structure; and a control unit configured to operate the array-to-storage heat transfer device, the storage-to-generator heat transfer device, the storage-to-water heat transfer device, and the storage-to-air heat transfer device.

We claim: 
     
         1 . A solar thermal combined heating, cooling, and power system for a structure comprises:
 a solar thermal array;   a stratified thermal energy storage unit;   a heat sink subsystem;
 a low temperature fluid reservoir; 
 a heat sink refrigeration unit; and 
 an exterior air cooling circuit; 
   a generator unit configured to provide electrical power to the structure;   a thermomechanical cooling unit configured to cool interior air in the structure;   an array-to-storage heat transfer device powered by the generator unit and configured to transfer thermal energy from the solar thermal array to the stratified thermal energy storage unit;   a storage-to-air heat transfer device powered by the generator unit and configured to heat the interior air of the structure;   a storage-to-water heat transfer device powered by the generator unit and configured to heat water in the hot water reservoir;   a storage-to-generator heat transfer device powered by the generator unit and configured to transfer thermal energy from the stratified thermal energy storage unit to the generator unit;   a storage-to-cooler heat transfer device powered by the generator unit and configured to transfer thermal energy from the stratified thermal energy storage unit to the thermomechanical cooling unit;   a cooler-to-sink heat transfer device powered by the generator unit and configured to transfer thermal energy away from the thermomechanical cooling unit to the heat sink subsystem; and   a control unit configured to operate the thermomechanical cooling unit; the storage-to-air heat transfer device, the storage-to-water heat transfer device, the array-to-storage heat transfer device, the storage-to-generator heat transfer device, the reservoir-to-generator heat transfer device, and the cooler-to-sink heat transfer device to provide electrical power, air-heating, air-cooling, and water-heating to the structure.   
     
     
         2 . The solar thermal combined heating, cooling, and power system of  claim 1 :
 wherein the stratified thermal energy storage unit defines:
 a set of output strata; and 
 a set of input strata; 
   wherein the stratified thermal energy storage unit comprises:
 an output valve array configured to output a high-temperature fluid at a target output temperature; and 
 an input valve array configured to input the high-temperature fluid to the stratified energy storage unit at a target stratum in the set of input strata; and 
   wherein the control unit is further configured to:
 operate the output valve array to output the high-temperature fluid based on the target output temperature and a set of output strata temperatures corresponding to the set of output strata; and 
 operate the input valve array based on the input temperature and a set of input strata temperatures corresponding to the set of input strata. 
   
     
     
         3 . The solar thermal combined heating, cooling, and power system of  claim 2 , wherein the output valve array comprises:
 for each output stratum in the set of output strata, a set of output valves comprising:
 a storage-to-generator output valve; 
 a storage-to-air output valve; 
 a storage-to-water output valve, and 
   a storage-to-cooler output valve;   a storage-to-generator fluid junction fluidically coupling the storage-to-generator output valve for each output stratum in the set of output strata;   a storage-to-air fluid junction fluidically coupling the storage-to-air output valve for each output stratum in the set of output strata;   a storage-to-water fluid junction fluidically coupling the storage-to-water output valve for each output stratum in the set of output strata; and   a storage-to-cooler fluid junction fluidically coupling the storage-to-cooler output valve for each output stratum in the set of output strata.   
     
     
         4 . The solar thermal combined heating, cooling, and power system of  claim 2 , wherein the input valve array comprises:
 for each input stratum in the set of input strata:
 an array-to-storage input valve in a set of array-to-storage input valves; 
 a generator-to-storage input valve in a set of generator-to-storage input valves; 
 an air-to-storage input valve in a set of air-to-storage input valves; 
 a water-to-storage input valve in a set of water-to-storage input valves, and 
 a cooler-to-storage input valve in a set of cooler-to-storage input valves; 
   an array-to-storage diverter valve configured to direct input array-to-storage high-temperature fluid to a target array-to-storage input valve in the set of array-to-storage input valves;   a generator-to-storage diverter valve configured to direct input storage-to-generator high-temperature fluid to a target generator-to-storage input valve in the set of generator-to-storage input valves;   an air-to-storage diverter valve configured to direct input air-to-storage high-temperature fluid to a target air-to-storage input valve in the set of air-to-storage input valves;   a water-to-storage diverter valve configured to direct input water-to-storage high-temperature fluid to a target water-to-storage input valve in the set of water-to-storage input valves; and   a storage-to-cooler diverter valve configured to direct input storage-to-cooler high-temperature fluid to a target cooler-to-storage input valve in the set of cooler-to-storage input valves.   
     
     
         5 . The solar thermal combined heating, cooling, and power system of  claim 1 , wherein the generator unit comprises a Stirling engine. 
     
     
         6 . The solar thermal combined heating, cooling, and power system of  claim 1 , wherein the thermomechanical cooling unit comprises a Stirling chiller. 
     
     
         7 . The solar thermal combined heating, cooling, and power system of  claim 1 :
 wherein the array-to-storage heat transfer device comprises an array-to-storage variable speed pump configured to circulate a high-temperature fluid between the solar thermal array and the stratified thermal energy storage unit;   wherein the storage-to-generator heat transfer device comprises a storage-to-generator variable speed pump configured to circulate the high-temperature fluid between the stratified thermal energy storage unit and the generator unit;   wherein the storage-to-cooler heat transfer device comprises a storage-to-cooler variable speed pump configured to circulate the high-temperature fluid between the stratified thermal energy storage unit and the thermomechanical cooling unit; and   wherein the cooler-to-sink heat transfer device comprises a cooler-to-sink variable speed pump configured to circulate the low-temperature fluid between the thermomechanical cooling unit and the heat sink subsystem.   
     
     
         8 . The solar thermal combined heating, cooling, and power system of  claim 1 , wherein the storage-to-air heat transfer device comprises:
 a storage-to-air heat exchanger configured to transfer thermal energy from a high-temperature fluid to a hydronic fluid;   a storage-to-air high-temperature fluid pump configured to circulate the high-temperature fluid between the stratified thermal storage unit and the storage-to-air heat exchanger; and   a hydronic heating circuit configured to circulate the hydronic fluid between the storage-to-air heat exchanger and the structure to heat an interior air volume of the structure.   
     
     
         9 . The solar thermal combined heating, cooling, and power system of  claim 1 , wherein the storage-to-water heat transfer device comprises;
 a storage-to-water heat exchanger configured to transfer thermal energy from the high-temperature fluid to water;   a storage-to-water high-temperature fluid pump configured to circulate the high-temperature fluid between the stratified thermal storage unit and the storage-to-water heat exchanger; and   a storage-to-water water-heating circuit configured to circulate water between the storage-to-water heat exchanger and a potable hot water supply of the structure.   
     
     
         10 . The solar thermal combined heating, cooling, and power system of  claim 1 , wherein the stratified thermal energy storage unit comprises a pebble bed thermal energy storage unit utilizing a high-temperature oil as the high-temperature fluid characterized by chemical and physical stability up to 400° C. 
     
     
         11 . The solar thermal combined heating, cooling, and power system of  claim 1 , wherein the heat sink subsystem comprises a refrigerated low-temperature fluid reservoir configured to maintain a low-temperature fluid temperature of less than 10° C. 
     
     
         12 . A solar thermal combined heating and power system for a structure comprises:
 a solar thermal array;   a stratified thermal energy storage unit comprising:
 an output valve array configured to output a high-temperature fluid from the stratified energy storage unit at a target output temperature; and 
 an input valve array configured to input the high-temperature fluid to the stratified energy storage unit at a target strata approximating an input temperature of the high-temperature fluid; 
   a generator unit configured to provide electrical power to the structure;   a storage-to-air heat transfer device powered by the generator unit and configured to heat the interior air of the structure;   a storage-to-water heat transfer device powered by the generator unit and configured to heat water in the hot water reservoir;   an array-to-storage heat transfer device powered by the generator unit and configured to transfer thermal energy from the solar thermal array to the stratified thermal energy storage unit;   a storage-to-generator heat transfer device powered by the generator unit and configured to transfer thermal energy from the stratified thermal energy storage unit to the generator unit; and   a control unit configured to:
 calculate a current electrical load for the generator unit based on a sum of a current generator operative load, a current plug load for the structure, a current air-heating load for the storage-to-air heat transfer device, and a current water-heating load for the storage-to-water heat transfer device; 
 calculate a current thermal load for the generator unit based on the current electrical load; 
 calculate a current storage-to-generator heat transfer rate sufficient to supply the current thermal load to the generator; 
 calculate a current target output temperature for the high-temperature fluid based on a set of generator operative parameters; 
 operate the output valve array to output the high-temperature fluid at the current target output temperature; 
 operate the storage-to-generator heat transfer device in accordance with the current storage-to-generator heat transfer rate; 
 operate the storage-to-air heat transfer device in accordance with the current air-heating load; and 
 operate the storage-to-water heat transfer device in accordance with the current water-heating load. 
   
     
     
         13 . The solar thermal combined heating and power system of  claim 12 , wherein the control unit is further configured to:
 calculate the current air-heating load for the storage-to-air heat transfer device based on a current air temperature and a current air set temperature for the structure; and   calculate the current water-heating load for the storage-to-water heat transfer device based on a current hot water temperature and a current hot water set temperature.   
     
     
         14 . The solar thermal combined heating and power system of  claim 12 , wherein the control unit is further configured to:
 calculate a current heat transfer capacity of the storage-to-generator heat transfer device based on a set of strata temperatures of the stratified thermal energy storage unit; and   in response to the current thermal load exceeding the current heat transfer capacity of the storage-to-generator heat transfer device:
 calculate an electrical load deficit based on the current thermal load and the current heat transfer capacity; and 
 calculate a throttled water-heating load, a throttled air-heating load, or a throttled plug load for the structure to eliminate the electrical load deficit. 
   
     
     
         15 . The solar thermal combined heating and power system of  claim 14 , wherein the control unit is further configured to:
 in response to the current water-heating load exceeding the electrical load deficit, calculating the throttled water-heating load by subtracting the electrical load deficit from the current water-heating load;   in response to the electrical load deficit exceeding the current water-heating load and the current air-heating load exceeding a first remainder of the electrical load deficit equal to the electrical load deficit less the current water-heating load:
 set the throttled water-heating load equal to zero watts; and 
 calculate the throttled air-heating load by subtracting the first remainder of the electrical load deficit from the current air-heating load; 
   in response to the electrical load deficit exceeding a sum of the current water-heating load and the current air-heating load and the current plug load exceeding exceeding a second remainder of the electrical load deficit equal to the electrical load deficit less the sum of the current water-heating load and the current air-heating load:
 set the throttled water-heating load equal to zero watts; 
 set the throttled air-heating load equal to zero watts; and 
 calculate the throttled plug load by subtracting the second remainder of the electrical laid deficit from the current plug load. 
   
     
     
         16 . The solar thermal combined heating and power system of  claim 14 , wherein the control unit  160  is further configured to calculate the throttled water-heating load, the throttled air-heating load, or the throttled plug load for the structure to eliminate the electrical load deficit based on a user-defined load reduction protocol. 
     
     
         17 . The solar thermal combined heating and power system of  claim 12 :
 wherein the generator unit is electrically coupled to an electrical grid; and   wherein the control unit is further configured to:
 calculate a current heat transfer capacity of the storage-to-generator heat transfer device based on a set of strata temperatures of the stratified thermal energy storage unit; and 
 in response to the current thermal load exceeding the current heat transfer capacity of the storage-to-generator heat transfer device:
 calculate an electrical load deficit based on the current thermal load and the current heat transfer capacity; and 
 draw grid power equal to the electrical load deficit from the electrical grid; and 
 
 in response to a current thermal energy storage state-of-charge exceeding a threshold state-of-charge:
 operate the storage-to-generator heat transfer device at the current storage-to-generator heat transfer capacity; and 
 discharge excess electrical energy produced by the generator unit to the grid. 
 
   
     
     
         18 . The solar thermal combined heating and power system of  claim 12 :
 further comprising:
 a thermomechanical cooling unit powered by the generator unit and configured to cool interior air in the structure; 
 a heat sink subsystem
 a low temperature fluid reservoir; 
 a heat sink refrigeration unit; and 
 an exterior air cooling circuit; 
 
 a storage-to-cooler heat transfer device powered by the generator unit and configured to transfer thermal energy from the stratified thermal energy storage unit to the thermomechanical cooling unit; and 
 a cooler-to-sink heat transfer device powered by the generator unit and configured to transfer thermal energy away from the thermomechanical cooling unit to the heat sink subsystem; and 
   wherein the control unit is further configured to, in response to a current temperature of the structure exceeding a current air set temperature:
 calculate a current air-cooling load of the thermomechanical cooling unit  130 , the storage-to-cooler heat transfer device, and the cooler-to-sink heat transfer device; and 
 operate the storage-to-cooler heat transfer device, the cooler-to-sink heat transfer device, and the thermomechanical cooling unit in accordance with the current air-cooling load. 
   
     
     
         19 . The solar thermal combined heating and power system of  claim 18 , wherein the control unit is further configured to, in response to a threshold temperature of the low temperature fluid reservoir exceeding a current temperature of the LTF reservoir: operating the heat sink refrigeration unit to lower the temperature of the low temperature fluid reservoir below the threshold temperature of the low temperature fluid reservoir. 
     
     
         20 . A solar thermal combined heating and power system comprises:
 a solar thermal array;   a thermal energy storage unit;   a generator unit configured to provide electrical power to the structure;   an array-to-storage heat transfer device powered by the generator unit and configured to transfer thermal energy from the solar thermal array to the thermal energy storage unit;   a storage-to-generator heat transfer device powered by the generator unit and configured to transfer thermal energy from the thermal energy storage unit to the generator unit;   a storage-to-water heat transfer device powered by the generator unit and configured to transfer thermal energy from the thermal energy storage unit to the water reservoir;   a storage-to-air heat transfer device powered by the generator unit and configured to transfer thermal energy from the thermal energy storage unit to the interior air of the structure; and   a control unit configured to operate the array-to-storage heat transfer device, the storage-to-generator heat transfer device, the storage-to-water heat transfer device, and the storage-to-air heat transfer device.