Method for charging and discharging a heat accumulator and plant for storing and releasing thermal energy, suitable for this method

Abstract

A method for charging and discharging a heat accumulator is provided. A system by which the method can be performed is also provided. By means of the heat accumulator, it is possible to convert overcapacities of wind turbines, for example, into a charging circuit as heat in the accumulator by a compressor. If necessary, electricity can be stored into the network by a turbine and a generator, wherein the heat accumulator is discharged. The charging circuit and the discharging circuit are operated by a Rankine cycle, wherein for example river water is available as a reservoir for heat exchangers in order to cause evaporation of the working medium in the charging circuit and condensation of the working medium in the discharging circuit.

1 . A method for charging and discharging a heat accumulator, comprising:
 during a charging cycle the heat accumulator is heated by means of a working fluid, wherein before passing through the heat accumulator a pressure increase is created in the working fluid by means of a first thermal fluid energy machine which is operated as a working machine, and after passing through the heat accumulator the working fluid is expanded and   during a discharging cycle the heat accumulator is cooled by means of a working fluid, wherein before passing through the heat accumulator a pressure increase is created in the working fluid and after passing through the heat accumulator the working fluid is expanded via a second thermal fluid energy machine which is operated as a power machine, or via the first thermal fluid energy machine which is operated as a power machine,
 wherein both the charging cycle and the discharging cycle are designed as a Rankine process in which the working fluid 
   is evaporated during the charging cycle via a first heat exchanger and   is condensed during the discharging cycle via the first or a second heat exchanger,
 wherein the first heat exchanger, and if the second heat exchanger is present, the second heat exchanger also, create a temperature balance with the environment. 
   
     
     
         2 . The method as claimed in  claim 1 , wherein the working fluid is ammonia or water. 
     
     
         3 . A method for charging and discharging a heat accumulator, comprising:
 during a charging cycle the heat accumulator is heated by means of a working fluid, wherein before passing through the heat accumulator a pressure increase is created in the working fluid by means of a first thermal fluid energy machine which is operated as a working machine, and after passing through the heat accumulator the working fluid is expanded and   during a discharging cycle the heat accumulator is cooled by means of a working fluid, wherein before passing through the heat accumulator a pressure increase is created in the working fluid and after passing through the heat accumulator the working fluid is expanded via a second thermal fluid energy machine which is operated as a power machine, or via the first thermal fluid energy machine which is operated as a power machine,
 wherein both the charging cycle and the discharging cycle are designed as a Rankine process in which the working fluid 
   is evaporated during the charging cycle via a third heat exchanger,   is condensed during the discharging cycle via a second heat exchanger and   during the charging cycle the third heat exchanger is heated by means of another working fluid with lower boiling point, wherein before passing through the heat exchanger a pressure increase is created in the other working fluid by means of a third thermal fluid energy machine which is operated as a working machine and after passing through the heat exchanger the other working fluid is expanded,
 wherein the first heat exchanger and the second heat exchanger create a temperature balance with the environment. 
   
     
     
         4 . The method as claimed in  claim 3 ,
 wherein the working fluid is water and the second working fluid is carbon dioxide.   
     
     
         5 . The method as claimed in  claim 1 ,
 wherein water is used as the heat transfer medium from the environment.   
     
     
         6 . A plant for storing and releasing thermal energy comprising:
 a heat accumulator, wherein the heat accumulator can release the stored heat to a charging circuit for a working fluid and to a discharging circuit for a working fluid,   wherein in the charging circuit the following units are interconnected in the specified sequence by means of lines:
 a first thermal fluid energy machine which is operated as a working machine, 
 the heat accumulator, 
 a device for expanding the working fluid, especially a first throttle and 
 a first heat exchanger, 
   wherein in the discharging circuit the following units are interconnected in the specified sequence by means of lines:
 the heat accumulator, 
 a second thermal fluid energy machine which is operated as a power machine or the first thermal fluid energy machine which is operated as a power machine, 
 the first heat exchanger or a second heat exchanger and 
 a pump, 
   wherein the first heat exchanger, and if the second heat exchanger is present, the second heat exchanger, ensure an exchange of heat with the environment of the plant.   
     
     
         7 . A plant for storing and releasing thermal energy comprising:
 a heat accumulator, wherein the heat accumulator can release the stored heat to a charging circuit for a working fluid and to a discharging circuit for a working fluid,   wherein in the charging circuit the following units are interconnected in the specified sequence by means of lines:
 a first thermal fluid energy machine which is operated as a working machine, 
 the heat accumulator, 
 a device for expanding the working fluid, especially a first throttle, and 
 a third heat exchanger, 
   wherein in the discharging circuit the following units are interconnected in the specified sequence by means of lines:
 the heat accumulator, 
 a second thermal fluid energy machine which is operated as a power machine or the first thermal fluid energy machine which is operated as a power machine, 
 a second heat exchanger and 
 a pump, 
   wherein in an additional circuit the following units are interconnected in the specified sequence by means of lines:
 a third thermal fluid energy machine which is operated as a working machine, 
 the third heat exchanger, 
 a device for expanding the working fluid, especially a second throttle and 
 a first heat exchanger, 
   wherein the first heat exchanger and the second heat exchanger ensure an exchange of heat with the environment of the plant.   
     
     
         8 . The plant as claimed in  claim 6 ,
 wherein the charging circuit and the discharging circuit extend through the same line, at least in certain sections.   
     
     
         9 . The plant as claimed in  claim 8 ,
 wherein the same lines are provided for the charging circuit and the discharging circuit, at least inside the heat accumulator.   
     
     
         10 . The method as claimed in  claim 3 ,
 wherein water is used as the heat transfer medium from the environment.   
     
     
         11 . The plant as claimed in  claim 7 ,
 wherein the charging circuit and the discharging circuit extend through the same line, at least in certain sections.   
     
     
         12 . The plant as claimed in  claim 11 ,
 wherein the same lines are provided for the charging circuit and the discharging circuit, at least inside the heat accumulator.