Method for charging and discharging a heat accumulator and system for storing and releasing thermal energy suitable for said method

Abstract

A method for charging and discharging a heat accumulator in a charge cycle and in a discharge cycle is provided. The discharging takes place by means of a steam turbine which has a high-pressure part and a low-pressure part. In order to provide heat to both turbine parts, the heat accumulator is divided into a part-accumulator for the high-pressure part and a part-accumulator for the low-pressure part. Furthermore, a system is provided in which the heat accumulator is divided into two part-accumulators. By operating a turbine with the high-pressure part and low-pressure part, the efficiency and yield of heat from the heat accumulator can be advantageously increased. The system can, for example, be used to temporarily store surplus capacities of a wind plant.

1 . A method for charging and discharging a heat accumulator, comprising:
 during a charging cycle, heating up the heat accumulator by a working fluid, a pressure rise being generated in the working fluid, before it runs through the heat accumulator, by a first thermal fluid energy machine, connected up as a working machine, and, after running through the heat accumulator, the working fluid undergoes the substantial part of its expansion, and,   during a discharging cycle, cooling the heat accumulator by a working fluid, a pressure rise being generated in the working fluid before it runs through the heat accumulator, and, after running through the heat accumulator, the working fluid being expanded via a second thermal fluid energy machine connected up as an engine,   wherein the discharging cycle is configured as a Rankine process, in which   the working fluid is first conducted through a first line system running in the heat accumulator,   subsequently, the working fluid is expanded via a high-pressure part HP of the second thermal fluid energy machine,   subsequently, the working fluid is conducted through a second line system running in the heat accumulator, and   subsequently, the working fluid is expanded via a low-pressure part LP of the second thermal fluid energy machine.   
     
     
         2 . The method as claimed in  claim 1 ,
 wherein the charging cycle is implemented by means of a heat pump process.   
     
     
         3 . The method as claimed in  claim 2 ,
 wherein nitrogen or dried air is used in the charging cycle.   
     
     
         4 . The method as claimed in  claim 1 ,
 wherein steam is used in the discharging cycle.   
     
     
         5 . A system for storing and releasing thermal energy, comprising
 a heat accumulator, the heat accumulator being capable of absorbing the stored heat from a charging circuit for a working fluid and of releasing it to a discharging circuit for a working fluid,   wherein the following units are connected to one another in the charging circuit by means of lines in the order indicated:   a first thermal fluid energy machine connected up as a working machine,   the heat accumulator,   a device for expanding the working fluid, and   a first heat exchanger,   and wherein the following units are connected to one another in the discharging circuit by means of lines in the order indicated:   the heat accumulator,   a second thermal fluid energy machine connected up as an engine,   the first heat exchanger or a second heat exchanger, and   a pump,   wherein the second thermal fluid energy machine has a high-pressure part (HP) and a low-pressure part (LP), and two line systems fluidically independent of one another, comprising a first line system and a second line system, in the heat accumulator,   wherein these units are connected to one another by means of lines in the order indicated:   the first line system,   the high-pressure part (HP),   the second line system, and   the low-pressure part (LP).   
     
     
         6 . The system as claimed in  claim 5 ,
 wherein the first line system is accommodated in a first subaccumulator and the second line system is accommodated in a second subaccumulator separated structurally from the first.   
     
     
         7 . The system as claimed in  claim 6 ,
 wherein the first subaccumulator and the second subaccumulator are arranged in parallel in the charging circuit.   
     
     
         8 . The system as claimed in  claim 5 ,
 wherein the first line system and the second line system run in the heat accumulator which is designed as a structural unit.   
     
     
         9 . The system as claimed in  claim 8 ,
 wherein the first line system is accommodated in a first subregion and the second line system is accommodated in a second subregion separated spatially from the first.   
     
     
         10 . The system as claimed in  claim 8 ,
 wherein the second line system is accommodated together with the first line system in a subregion of the heat accumulator.   
     
     
         11 . The system as claimed in  claim 10 ,
 wherein the second line system is accommodated together with the first line system in a plurality of second subregions of the heat accumulator.   
     
     
         12 . The system as claimed in  claim 6 ,
 wherein the ratio of the heat capacity of the first subregion to that of the second subregion or second subregions or of the first subaccumulator to the second subaccumulator is adapted to the heat demand caused by the discharging process, in such a way that the two subregions or subaccumulators are discharged within the same timespan.   
     
     
         13 . The system as claimed in  claim 5 , wherein the device for expanding the working fluid comprises a third fluid energy machine. 
     
     
         14 . The system as claimed in  claim 5 , wherein the first heat exchanger comprises a cold accumulator. 
     
     
         15 . The system as claimed in  claim 11 , wherein the second line system is short-circuited in each of these second subregions via a bypass line.