Nitrogen based thermal storage medium

Abstract

A thermal storage and transfer method for use in both indirect and direct heating solar power plants that involves the use of nitrogen gas as a thermal storage medium for heat transfer in circumstances where little or no solar radiation is available to produce the thermal energy needed to convert water into steam and generate electricity.

1 . A thermal storage and transfer method for use in a direct heating solar power plant comprising the steps of:
 releasing nitrogen from one or more cold nitrogen storage containers and then passing the nitrogen through boiler tubes receiving thermal energy transferred from focused solar energy available during daylight;   storing heated nitrogen in one or more hot nitrogen containers connected to the boiler tubes; and   routing the heated nitrogen from the one or more hot nitrogen containers through the boiler tubes and into a heat exchanger, wherein thermal energy from the heated nitrogen is used to convert water into steam in the heat exchanger.   
     
     
         2 . The thermal storage and transfer method of  claim 1  wherein the said step of routing the heated nitrogen occurs during periods of shade or at night when insufficient solar energy is available for heating the nitrogen at a sufficient temperature to convert water into steam in the heat exchanger. 
     
     
         3 . The thermal storage and transfer method of  claim 1  further comprising the steps of:
 routing a second stream of nitrogen through boiler tubes receiving thermal energy transferred from focused solar energy available during daylight; and 
 routing the heated second stream of nitrogen through a second heat exchanger, wherein thermal energy from the heated second stream of nitrogen is used to convert water into steam in the second heat exchanger during daylight operation. 
 
     
     
         4 . The thermal storage and transfer method of  claim 1  wherein the nitrogen is pressurized. 
     
     
         5 . A thermal storage and transfer method for use in an indirect heating solar power plant comprising the steps of:
 transferring heat from heat transfer fluid, heated by means of a parabolic mirror, to nitrogen in a heat exchanger; and   storing the heated nitrogen in one or more hot nitrogen containers.   
     
     
         6 . The thermal storage and transfer method of  claim 5  further comprising the step of routing the heated nitrogen from the one or more hot nitrogen containers into a second heat exchanger, wherein thermal energy from the heated nitrogen is used to convert water to steam during periods of shade or at night when insufficient solar energy is available for heating heat transfer fluid at a sufficient temperature to convert water into steam. 
     
     
         7 . The thermal storage and transfer method of  claim 5  wherein the nitrogen is pressurized in one or more containers. 
     
     
         8 . A thermal storage and transfer method for use in an indirect heating solar power plant comprising the steps of:
 transferring solar energy to nitrogen by means of a parabolic mirror; and   storing heated nitrogen in one or more hot nitrogen containers.   
     
     
         9 . The thermal storage and transfer method of  claim 8  further comprising the steps of:
 routing the heated nitrogen from one or more hot nitrogen containers during periods of low light or darkness into a heat exchanger; and 
 transferring thermal energy from the heated nitrogen to water in the heat exchanger in order to create steam. 
 
     
     
         10 . The thermal storage and transfer method of  claim 8  further comprising the steps of:
 transferring thermal energy from nitrogen heated by means of a parabolic mirror to a heat exchanger; and 
 transferring thermal energy from the heated nitrogen to water in the heat exchanger in order to create steam. 
 
     
     
         11 . The thermal storage and transfer method of  claim 8  wherein the nitrogen is pressurized.