Thermal-energy-storage tank with integrated steam generator

Abstract

A thermal-energy storage tank ( 1 ) comprising a containing structure ( 2 ) designed to house a store of thermovector fluid in the liquid state, a regenerating circuit ( 6 ) designed to draw the thermovector fluid from a bottom of the containing structure ( 2 ) and, once heated outside the tank, to deposit it in a surface portion of the store of thermovector fluid, at least one steam generator ( 13 ) comprising a heat exchanger ( 14, 16 b ) with vertical extension housed within the containing structure ( 2 ) and having at least one top opening ( 18 ) designed for inlet of the thermovector fluid and a bottom opening designed for outlet of the thermovector fluid ( 15 ).

1 . A thermal-energy storage tank comprising a containing structure designed to house a store of thermovector fluid in the liquid state and spontaneously stratified in temperature, a regenerating circuit designed to draw said thermovector fluid from a bottom of said containing structure for taking it out of said containing structure and, once heated by means of heating means that are lodged outside said containing structure, to deposit it in a surface portion of said store of thermovector fluid, at least one steam generator comprising a heat exchanger with vertical extension that is housed within said containing structure and immersed in said thermovector fluid; said heat exchanger having at least one top opening designed for inlet of said thermovector fluid coming from said store and a bottom opening designed for outlet of said thermovector fluid for its reintroduction in said store. 
     
     
         2 . (canceled) 
     
     
         3 . The thermal-energy storage tank according to  claim 1 , characterized in that said heat exchanger is a tube-nest heat exchanger and shell. 
     
     
         4 . The thermal-energy storage tank according to  claim 3 , characterized in that said steam generator comprises a cylindrical shell and a tube nest with helical conformation and housed entirely within said shell. 
     
     
         5 . The thermal-energy storage tank according to  claim 4 , characterized in that said steam generator comprises a first thermal-insulation jacket set around the shell for insulating thermally the thermovector fluid that flows within the shell from the store of thermovector fluid present in the containing structure, and a second thermal-insulation jacket set inside the heat-exchange portions and outside the delivery portions for insulating thermally the water that flows therein from the thermovector fluid present within the shell. 
     
     
         6 . The thermal-energy storage tank according to  claim 1 , characterized in that said steam generator comprises a diffuser connected in a fluid-tight way to a bottom end of the shell and constituting said bottom opening. 
     
     
         7 . The thermal-energy storage tank according to  claim 6 , characterized in that said steam generator comprises a component designed to promote motion of the molten salts for contributing to onset of natural circulation thereof. 
     
     
         8 . A method for producing steam comprising a step of heat exchange in which water flowing within tubes from the bottom up exchanges heat with a thermovector fluid in the liquid state that flows from the top down in a shell in which said tubes are housed; said method being characterized in that said shell is connected at inlet and at outlet to a store of said thermovector fluid in the liquid state stratified in temperature; said thermovector fluid entering from the top at a high temperature, traversing said shell from top downwards with simultaneous yielding of heat to the water and exiting at the bottom from the shell at a lower temperature to entering said store at a level in which the stratified thermovector fluid has a temperature approximately equal to its own; said shell being set immersed within said store of thermovector fluid in the liquid state stratified in temperature; said thermovector fluid entering said shell from the top by percolation and exiting from the shell at the bottom at the temperature of the thermovector fluid present at the level at which outlet takes place. 
     
     
         9 . (canceled) 
     
     
         10 . The method for producing steam according to  claim 8 , characterized in that said thermovector fluid in the liquid state is constituted by molten salts made up of a mixture of sodium nitrate and potassium nitrate. 
     
     
         11 . The method for producing steam according to  claim 8 , characterized in that it comprises a heating step in which the thermovector fluid is in sequence:
 drawn from the bottom of said store;   subjected to a heating process; and   deposited in a surface portion of said store of thermovector fluid stratified in temperature.   
     
     
         12 . The method for producing steam according to  claim 11 , characterized in that said heating process occurs by means of a set of solar concentrators.