Thermoelectric energy storage system and method for storing thermoelectric energy

Abstract

A system and method are provided for thermoelectric energy storage. A thermoelectric energy storage system having at least one hot storage unit is provided. In an exemplary embodiment, each hot storage unit includes a hot tank and a cold tank connected via a heat exchanger and containing a thermal storage medium. The thermoelectric energy storage system also includes a working fluid circuit for circulating working fluid through each heat exchanger for heat transfer with the thermal storage medium. Improved roundtrip efficiency is achieved by minimizing the temperature difference between the working fluid and the thermal storage medium in each heat exchanger during heat transfer. Exemplary embodiments realize this improved roundtrip efficiency through modification of thermal storage media parameters.

1 . A thermoelectric energy storage system for providing thermal energy to a thermodynamic machine for generating electricity, the system comprising:
 a heat exchanger;   a hot storage unit which is connected to the heat exchanger and which contains a thermal storage medium; and   a working fluid circuit configured to circulate a working fluid through the heat exchanger for heat transfer with the thermal storage medium contained in the hot storage unit, and   wherein working fluid circuit is configured to minimize a temperature difference between the working fluid and the thermal storage medium in the hot storage unit during heat transfer.   
     
     
         2 . The system according to  claim 1 , wherein the hot storage unit comprises at least two hot storage units,
 wherein each of the at least two hot storage units is connected to a respective heat exchanger and contains a thermal storage medium.   
     
     
         3 . The system according to  claim 1 , wherein the thermal storage medium is a liquid, and the working fluid circuit is configured to modify a flow rate of the thermal storage medium such that the temperature difference between the working fluid and the thermal storage medium in the hot storage unit is minimized during heat transfer. 
     
     
         4 . The system according to  claim 1 , wherein the working fluid circuit is configured to modify the temperature of the thermal storage medium at entry and exit points of the heat exchanger such that the temperature difference between the working fluid and the thermal storage medium in the hot storage unit is minimized during heat transfer. 
     
     
         5 . The system according to  claim 2 , wherein at least one of the hot storage units contains a different type of thermal storage medium such that the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is minimized during heat transfer. 
     
     
         6 . The system according to  claim 1 , wherein the temperature difference between the working fluid and the thermal storage medium in the hot storage unit is less than 50° C. during heat transfer. 
     
     
         7 . A method for storing thermoelectric energy in a thermoelectric energy storage system, comprising;
 charging a hot storage unit by providing heat via a heat exchanger to a thermal storage medium by compressing a working fluid;   discharging the hot storage unit by expanding the working fluid heated via the heat exchanger from the thermal storage medium through a thermodynamic machine; and   modifying thermal storage media parameters to ensure that a temperature difference between the working fluid and the thermal storage medium is minimized during charging and discharging.   
     
     
         8 . The method according to  claim 7 , wherein the step of modifying the thermal storage media parameters comprises modifying the flow rate of the thermal storage medium. 
     
     
         9 . The method according to  claim 7 , wherein the step of modifying the thermal storage media parameters comprises modifying an initial temperature and final temperature of the thermal storage medium. 
     
     
         10 . The method according to  claim 7 , wherein the step of modifying the thermal storage media parameters comprises modifying the type of thermal storage medium. 
     
     
         11 . The system according to  claim 2 , wherein the thermal storage medium is a liquid, and the working fluid circuit is configured to modify a flow rate of the thermal storage medium such that the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is minimized during heat transfer. 
     
     
         12 . The system according to  claim 11 , wherein at least one of the hot storage units contains a different type of thermal storage medium such that the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is minimized during heat transfer. 
     
     
         13 . The system according to  claim 2 , wherein the working fluid circuit is configured to modify the temperature of the thermal storage medium at entry and exit points of each connected heat exchanger such that the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is minimized during heat transfer. 
     
     
         14 . The system according to  claim 13 , wherein at least one of the hot storage units contains a different type of thermal storage medium such that the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is minimized during heat transfer. 
     
     
         15 . The system according to  claim 3 , wherein the working fluid circuit is configured to modify the temperature of the thermal storage medium at entry and exit points of each connected heat exchanger such that the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is minimized during heat transfer. 
     
     
         16 . The system according to  claim 15 , wherein the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is less than 50° C. during heat transfer. 
     
     
         17 . The system according to  claim 2 , wherein the temperature difference between the working fluid and the thermal storage medium in each hot storage unit is less than 50° C. during heat transfer. 
     
     
         18 . The method according to  claim 8 , wherein the step of modifying the thermal storage media parameters comprises modifying an initial temperature and final temperature of the thermal storage medium. 
     
     
         19 . The method according to  claim 8 , wherein the step of modifying the thermal storage media parameters comprises modifying the type of thermal storage medium. 
     
     
         20 . The method according to  claim 9 , wherein the step of modifying the thermal storage media parameters comprises modifying the type of thermal storage medium.