Thermoelectric energy storage system and method for storing thermoelectric energy

Abstract

A thermoelectric energy storage system includes an intercooler for intercooling a working fluid between two compression stages. The intercooling may be carried out by flashing a portion of the working fluid taken from the output of an expander in a flash intercooler and/or by heating a secondary thermal storage with a further heat exchanger.

What is claimed is: 
     
         1 . A thermoelectric energy storage system for storing electrical energy by transferring thermal energy to a thermal storage in a charging cycle, and for generating electricity by retrieving the thermal energy from the thermal storage in a discharging cycle, the thermoelectric energy storage system comprising:
 a working fluid circuit configured to circulate a working fluid;   a first compressor configured to, in the charging cycle, compress the working fluid from a low pressure to an intermediate pressure;   an intercooler configured to, in the charging cycle, cool the working fluid at the intermediate pressure;   a second compressor configured to, in the charging cycle, compress the working fluid from the intermediate pressure to a high pressure; and   a first heat exchanger configured to, in the charging cycle, transfer heat from the working fluid at the high pressure to the thermal storage and, in the discharging cycle, transfer heat from the thermal storage to the working fluid at the high pressure.   
     
     
         2 . The system according to  claim 1 , wherein the intercooler includes a flash intercooler. 
     
     
         3 . The system according to  claim 1 , wherein the intercooler includes a second heat exchanger configured to, in the charging cycle, transfer heat from the working fluid at the intermediate pressure to a second thermal storage and, in the discharging cycle, transfer heat from the second thermal storage to the working fluid at intermediate pressure. 
     
     
         4 . The system according to  claim 1 , comprising:
 a first expander configured to, in the charging cycle, expand the working fluid after the first heat exchanger to the intermediate pressure,   wherein, in the charging cycle, a first portion of the working fluid at the intermediate pressure is input into the intercooler.   
     
     
         5 . The system according to  claim 4 , comprising:
 a second expander configured to, in the charging cycle, expand the working fluid at the intermediate pressure to the low pressure.   
     
     
         6 . The system according to  claim 1 , comprising:
 a third heat exchanger configured to, in the charging cycle, transfer heat from a third thermal storage to the working fluid at the low pressure and, in the discharging cycle, transfer heat from the working fluid at the low pressure to the third thermal storage.   
     
     
         7 . The system according to  claim 1 , wherein:
 the intercooler includes a flash intercooler and a third heat exchanger; and   in the charging cycle, the working fluid between the flash intercooler and the third heat exchanger is compressed from a first intermediate pressure to a second intermediate pressure.   
     
     
         8 . The system according to  claim 1 , comprising:
 a first turbine configured to, in the discharging cycle, expand the working fluid from the high pressure to the intermediate pressure for generating electrical energy; and   a second turbine configured to, in the discharging cycle, expand the working fluid from the intermediate pressure to the low pressure for generating electrical energy.   
     
     
         9 . The system according to  claim 1 , comprising:
 a pump configured to, in the discharging cycle, pump the working fluid from the low pressure to the high pressure during the discharging cycle.   
     
     
         10 . A method for storing electrical energy in a charging cycle and retrieving electrical energy in a discharging cycle,
 wherein, in the charging cycle, the method comprises:   compressing the working fluid from a low pressure to an intermediate pressure for storing electrical energy;   cooling the working fluid at the intermediate pressure;   compressing the working fluid from the intermediate pressure to a high pressure for storing electrical energy; and   transferring heat from the working fluid at the high pressure to the thermal storage, and   wherein, in the discharging cycle, the method comprises:   transferring heat from the thermal storage to the working fluid at the high pressure; and   expanding the working fluid from the high pressure for generating electrical energy.   
     
     
         11 . The method according to  claim 10 , wherein:
 in the charging cycle, the method comprises transferring heat from the working fluid at the intermediate pressure to a second thermal storage; and   in the discharging cycle, the method comprises:   expanding the working fluid from the high pressure to the intermediate pressure for generating electrical energy in a first turbine;   transferring heat from the second thermal storage to the working fluid at the intermediate pressure;   expanding the working fluid from the intermediate pressure to the low pressure for generating electrical energy in a second turbine.   
     
     
         12 . The method according to  claim 10 , wherein, in the charging cycle, the method comprises:
 expanding the working fluid after the heat exchanging at the high pressure to the intermediate pressure; and   using a first portion of the working fluid at intermediate pressure after the heat exchanging at the high pressure for cooling the working fluid before heat exchanging at the high pressure.   
     
     
         13 . The method according to  claim 10 , wherein, in the charging cycle, the method comprises:
 expanding the working fluid at the intermediate pressure to the low pressure; and   transferring heat from a third thermal storage to the working fluid at the low pressure, and   wherein, in the discharging cycle, the method comprises transferring heat from the working fluid at the low pressure to the third thermal storage.   
     
     
         14 . The method according to  claim 10 , wherein, in the charging cycle, the method comprises compressing the working fluid from a first intermediate pressure to a second intermediate pressure between a flash intercooling with the working fluid at the first intermediate pressure and heat exchanging with a second thermal storage at the second intermediate pressure. 
     
     
         15 . The method according to  claim 10 , wherein at least one section of at least one of the charging cycle and the discharging cycle is performed transcritically. 
     
     
         16 . The system according to  claim 2 , wherein the intercooler includes a second heat exchanger configured to, in the charging cycle, transfer heat from the working fluid at the intermediate pressure to a second thermal storage and, in the discharging cycle, transfer heat from the second thermal storage to the working fluid at intermediate pressure. 
     
     
         17 . The system according to  claim 16 , comprising:
 a first expander configured to, in the charging cycle, expand the working fluid after the first heat exchanger to the intermediate pressure,   wherein, in the charging cycle, a first portion of the working fluid at the intermediate pressure is input into the intercooler.   
     
     
         18 . The system according to  claim 17 , comprising:
 a second expander configured to, in the charging cycle, expand the working fluid at the intermediate pressure to the low pressure.   
     
     
         19 . The system according to  claim 16 , comprising:
 a third heat exchanger configured to, in the charging cycle, transfer heat from a third thermal storage to the working fluid at the low pressure and, in the discharging cycle, transfer heat from the working fluid at the low pressure to the third thermal storage.   
     
     
         20 . The system according to  claim 16 , wherein:
 the intercooler includes a flash intercooler and a third heat exchanger; and   in the charging cycle, the working fluid between the flash intercooler and the third heat exchanger is compressed from a first intermediate pressure to a second intermediate pressure.   
     
     
         21 . The system according to  claim 16 , comprising:
 a first turbine configured to, in the discharging cycle, expand the working fluid from the high pressure to the intermediate pressure for generating electrical energy; and   a second turbine configured to, in the discharging cycle, expand the working fluid from the intermediate pressure to the low pressure for generating electrical energy.   
     
     
         22 . The system according to  claim 16 , comprising:
 a pump configured to, in the discharging cycle, pump the working fluid from the low pressure to the high pressure during the discharging cycle.   
     
     
         23 . The method according to  claim 10 , wherein the compressing of the working fluid from the low pressure to the intermediate pressure includes storing the electrical energy for converting the electrical energy into heat energy. 
     
     
         24 . The method according to  claim 11 , wherein, in the charging cycle, the method comprises:
 expanding the working fluid after the heat exchanging at the high pressure to the intermediate pressure; and   using a first portion of the working fluid at intermediate pressure after the heat exchanging at the high pressure for cooling the working fluid before heat exchanging at the high pressure.   
     
     
         25 . The method according to  claim 24 , wherein, in the charging cycle, the method comprises:
 expanding the working fluid at the intermediate pressure to the low pressure; and   transferring heat from a third thermal storage to the working fluid at the low pressure, and   wherein, in the discharging cycle, the method comprises transferring heat from the working fluid at the low pressure to the third thermal storage.   
     
     
         26 . The method according to  claim 25 , wherein, in the charging cycle, the method comprises compressing the working fluid from a first intermediate pressure to a second intermediate pressure between a flash intercooling with the working fluid at the first intermediate pressure and heat exchanging with a second thermal storage at the second intermediate pressure. 
     
     
         27 . The method according to  claim 25 , wherein at least one section of at least one of the charging cycle and the discharging cycle is performed transcritically.