Coupled chemical-thermal solar power system and method

Abstract

A CSP system is disclosed which couples a thermal and a chemical energy pathway. The thermal pathway utilizes a heat transfer fluid to collect concentrated sunlight as thermal energy at medium temperature and transfer this energy to a thermal-to-electric power cycle. In parallel, the chemical pathway uses a redox material which undergoes direct photoreduction in the receiver to store the solar energy as chemical potential. This redox material is then oxidized at very high temperatures in the power cycle in series with the thermal pathway heat exchanger. This coupling allows the receiver to perform at the high efficiencies typical of state of the art thermal power towers while simultaneously achieving the power cycle efficiencies typical of natural gas combustion plants and achieving a very high overall solar-to-electric conversion efficiency.

What is claimed is: 
     
         1 . A concentrating solar power system comprising:
 a solar receiver configured to receive concentrated solar flux;   heat transfer fluid in thermal communication with the solar receiver such that concentrated solar flux heats a quantity of the heat transfer fluid;   a heat exchanger in thermal communication with the heat transfer fluid, the heat exchanger providing for heat exchange between the heat transfer fluid and a working fluid of a power cycle;   a heat transfer fluid conduit providing for the flow or transport of heat transfer fluid between the solar receiver and the heat exchanger;   chemical energy storage material in communication with the solar receiver such that concentrated solar flux reduces a quantity of the chemical energy storage material;   an oxidizer in communication with the chemical energy storage material, the oxidizer providing for the oxidation of the chemical energy storage material and further providing for heat exchange between the chemical energy storage material and the working fluid of the power cycle; and   a chemical energy storage material conduit providing for the flow or transport of chemical energy storage material between the solar receiver and the oxidizer.   
     
     
         2 . The concentrating solar power system of  claim 1  further comprising a thermal energy storage system operatively associated with the heat transfer fluid conduit. 
     
     
         3 . The concentrating solar power system of  claim 2  further comprising:
 a hot thermal energy storage system receiving heated heat transfer fluid from the solar receiver; and 
 a cold thermal energy storage system receiving cooled heat transfer fluid from the heat exchanger. 
 
     
     
         4 . The concentrating solar power system of  claim 1  further comprising:
 a reduced chemical energy storage material storage system operatively associated with the chemical energy storage material conduit and receiving reduced chemical energy storage material from the solar receiver; and 
 an oxidized chemical energy storage material storage system operatively associated with the chemical energy storage material conduit and receiving oxidized chemical energy storage material from the oxidizer. 
 
     
     
         5 . The concentrating solar power system of  claim 1  wherein the heat transfer fluid comprises one or more of water, a solid salt; a molten salt, a solid metal;
 a molten metal and an oil. 
 
     
     
         6 . The concentrating solar power system of  claim 1  wherein the heat transfer fluid comprises an aluminum silicon phase change material. 
     
     
         7 . The concentrating solar power system of  claim 1  further comprising:
 a tower supporting the solar receiver; and 
 a heliostat field having heliostats positioned to focus sunlight on the receiver. 
 
     
     
         8 . The concentrating solar power system of  claim 1  wherein the power cycle comprises:
 an open air Brayton upper power cycle; and 
 steam Rankine bottoming cycle. 
 
     
     
         9 . The concentrating solar power system of  claim 1  wherein the working fluid of the power cycle contains an oxidizing agent. 
     
     
         10 . A power generation method comprising:
 providing a solar receiver configured to receive concentrated solar flux;   heating a heat transfer fluid in thermal communication with the solar receiver with the concentrated solar flux;   flowing or transporting the heat transfer fluid between the solar receiver and a heat exchanger in a heat transfer fluid conduit;   exchanging heat between the heated heat transfer fluid and a working fluid of a power cycle within the heat exchanger;   reducing a chemical energy storage material in communication with the solar receiver by irradiating the chemical energy storage material with concentrated solar flux;   flowing or transporting the reduced chemical energy storage material between the solar receiver and an oxidizer in a chemical energy storage material conduit;   oxidizing the reduced chemical energy storage material in an oxidizer, the oxidizer further providing for heat exchange between the chemical energy storage material and the working fluid of the power cycle; and   generating power with the working fluid of the power cycle.   
     
     
         11 . The method of  claim 11  further comprising storing heat transfer fluid in a thermal energy storage system operatively associated with the heat transfer fluid conduit. 
     
     
         12 . The method of  claim 11  further comprising:
 storing heated heat transfer fluid received from the solar receiver in a hot thermal energy storage system; and 
 storing cooled heat transfer fluid received from the heat exchanger in a cold thermal energy storage system. 
 
     
     
         13 . The method of  claim 11  further comprising:
 storing reduced chemical energy storage material received from the receiver in a reduced chemical energy storage material storage system; and 
 storing oxidized chemical energy storage material received from the oxidizer in an oxidized chemical energy storage material storage system. 
 
     
     
         14 . The method of  claim 11  wherein the heat transfer fluid comprises one or more of water, a solid salt; a molten salt, a solid metal; a molten metal and an oil. 
     
     
         15 . The method of  claim 11  wherein the heat transfer fluid comprises an aluminum silicon phase change material. 
     
     
         16 . The method of  claim 11  further comprising:
 providing a tower to support the solar receiver; and 
 providing a heliostat field having heliostats positioned to focus sunlight on the receiver. 
 
     
     
         17 . The method of  claim 11  further comprising generating power with a power cycle comprising:
 an open air Brayton upper power cycle; and 
 steam Rankine bottoming cycle. 
 
     
     
         18 . The method of  claim 11  further comprising oxidizing the reduced chemical energy storage material in the oxidizer with a oxidizing agent in the working fluid of the power cycle.