A carnot cell system and method based on thermochemical energy storage

Abstract

The application discloses a kind of based on thermochemical energy storage's Carnot cell system and method, including electric drive thermochemical energy storage reactor, steam turbine, generator set, condenser, high-pressure pump, steam accumulator;Steam turbine is connected with generator set, steam turbine is driven by the steam generated by electric drive thermochemical energy storage reactor, and steam turbine drives generator set to generate electricity again;Steam accumulator is connected with the steam passage in electric drive thermochemical energy storage reactor, for storing or providing the steam of reaction;High-pressure pump is connected with the tubular heater in electric drive thermochemical energy storage reactor, and the steam generated by steam turbine is condensed into circulating working medium water by condenser, and is sent back to electric drive thermochemical energy storage reactor by high-pressure pump and circulates to work.The reaction device of the application is compact, and electric energy is efficiently converted into heat energy, and is further converted into chemical energy in the form of chemical reaction heat to store.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage batteries, in particular to a Carnot battery system based on thermochemical energy storage. BACKGROUND

[0002] Due to the characteristics of low energy density, uneven spatial distribution and uneven time distribution of solar energy, it is difficult to be directly and efficiently utilized. The growth of renewable energy requires flexible, low-cost and efficient power storage to balance the mismatch between energy supply and demand. Carnot battery is an emerging electric energy storage technology. It can realize medium to large scale electric energy storage at low cost and without geographical restrictions. Carnot battery converts electric energy into thermal energy, and stores thermal energy in relatively inexpensive media such as water and molten salt. When electric energy is needed, thermal energy is converted into electric energy through special equipment. When power production is higher than demand, Carnot battery can buffer electric energy through charging cycle mode of storing heat from resistance heater or heat pump system. When power demand is higher than production, Carnot battery can generate electricity through stored heat in power cycle mode. Thermochemical energy storage technology has high heat storage density, which is beneficial to long-term energy storage. There are more choices of heat storage materials or reversible chemical reactions, and the applicable temperature range is wide. Therefore, it has great application value in industrial waste heat utilization, solar heat storage and chemical heat pump.

[0003] However, the research on the practical application of Carnot battery has gradually started due to the rise of renewable energy in recent years. People have given many possible technologies and configurations of Carnot battery, but the actual performance indicators of this technology are still unclear. Therefore, this technology has not been widely used. Moreover, the conversion process of Carnot battery involves thermochemical energy storage technology. Compared with other energy storage technologies, thermochemical energy storage technology has the problems of slow reaction rate, low energy storage efficiency and low safety. Therefore, this emerging energy storage technology still needs further research on thermochemical reaction and thermal power generation, so as to generate electricity through stored heat at high efficiency and low cost, and to realize large-scale application layout.

[0004] However, current thermochemical energy storage reactors primarily utilize molten liquids as the basic reactant state, placing high demands on the device's insulation and safety performance. Furthermore, indirect heat exchange reactors suffer from limitations in thermochemical reactions due to the low thermal conductivity of solid particles and significant thermal resistance caused by gas gaps between particles, severely impacting the reactor's heat absorption / release performance. Higher decomposition temperatures can accelerate and expedite the reaction, but high temperatures exacerbate material agglomeration and sintering, reducing the reactor's cycle performance. In addition, these high temperatures result in low overall integration of the reactor, increasing land, production, and operating costs. The application methods and systems of the Ca(OH)₂ / CaO thermochemical energy storage system are still in the initial research stage. To enable more efficient operation of thermochemical energy storage systems and ultimately solve the global renewable electricity storage problem in a more economical and environmentally friendly way than traditional batteries, designing an energy storage system suitable for large-scale, low-cost electricity storage is a crucial issue that urgently needs to be addressed. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention aims to provide a Carnot battery system and method based on thermochemical energy storage. This system utilizes a thermochemical energy storage system to store electrical energy generated from renewable energy sources in a low-cost, stable compound, and provides thermal energy for power generation through an exothermic reaction when needed. In particular, employing resistance heating to drive the thermochemical reaction allows for a compact reaction device, efficient conversion of electrical energy into thermal energy, and further conversion into chemical energy for storage via the heat of chemical reaction. Furthermore, through rational structural integration, thermal storage and exothermic reactions can be integrated into a single reaction device, saving production and land costs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A Carnot battery system based on thermochemical energy storage includes an electrically driven thermochemical energy storage reactor 1, a steam turbine 2, a generator set 3, a condenser 4, a high-pressure pump 5, and a steam accumulator 6.

[0008] The steam turbine 2 is connected to the generator set 3. The steam generated by the electro-driven thermochemical energy storage reactor 1 drives the steam turbine 2, which in turn drives the generator set 3 to generate electricity.

[0009] The steam accumulator 6 is connected to the steam channel 9 in the electro-driven thermochemical energy storage reactor 1 and is used to store or provide steam for the reaction.

[0010] The high-pressure pump 5 is connected to the tubular heater 7 inside the electro-driven thermochemical energy storage reactor 1. The exhaust steam generated by the steam turbine 2 flows through the condenser 4 and is condensed into circulating working fluid water, which is then sent back to the electro-driven thermochemical energy storage reactor 1 by the high-pressure pump 5 to absorb heat and perform work in a cycle.

[0011] The system composed of the above device can realize the functions of storing and discharging electricity through thermo-chemical reaction and steam cycle.

[0012] The electrically-driven thermo-chemical energy storage reactor 1 comprises an external reactor shell 12, a tubular electric heater 7 in the center of the axis inside the reactor shell 12, a spiral hollow perforated fin 8 arranged outside the tubular electric heater 7, the outer side of the spiral hollow perforated fin 8 being in contact with the inner wall of the reactor shell 12, the reaction cavity 10 being between the spiral hollow perforated fins 8, the top of the spiral hollow perforated fin 8 not being in contact with the reactor shell 12, leaving a cavity of the reaction cavity 10, the reactor shell 12 being provided with a reactant feeding port 13 at the top, the reactant feeding port 13 being in communication with the cavity of the reaction cavity 10, and the solid reactant 11 entering the reaction cavity 10 through the solid reactant feeding port 13.

[0013] The spiral hollow perforated fin 8 has a spiral structure, a hollow structure, and uniform mesh holes arranged thereon; the spiral structure is used for facilitating the filling of solid reactant particles by gravity; the hollow structure forms a steam passage 9, so that the reaction steam rapidly enters or leaves the reaction cavity 10; and the fin structure is used for strengthening the conduction of heat between the tubular electric heater 7 and the solid reactant 11.

[0014] The reactor shell 12 is provided with an external heat preservation layer 14 to reduce the heat loss of the system during high-temperature operation.

[0015] A running mode of a Carnot cell system based on thermo-chemical energy storage comprises the following steps:

[0016] a charging mode: the grid power drives the tubular electric heater 7 in the electrically-driven thermo-chemical energy storage reactor 1 to heat, the generated heat is introduced into the reaction cavity 10 through the spiral hollow perforated fin 8, and the solid reactant 11 filled therein is heated to the thermo-chemical reaction temperature to cause the following endothermic reaction:

[0017] solid alkali metal hydroxide + heat → solid alkali metal oxide + water vapor, wherein the generated solid alkali metal oxide remains in the reaction cavity 10, the water vapor enters the steam passage 9 through the small hole structure of the spiral hollow perforated fin 8 and is discharged out of the electrically-driven thermo-chemical energy storage reactor 1, then enters the steam accumulator 6 and is stored; the above process realizes the Carnot cell system charging process of converting the electric energy from the grid into chemical energy through the chemical reaction heat of endothermic reaction, and into latent heat of vaporization through the vaporization process, and storing them respectively;

[0018] b Discharge mode: the steam accumulator 6 releases water vapor through pressure regulation, the water vapor enters the reaction cavity 10 through the steam channel 9 and the small hole structure of the spiral hollow perforated fin 8, and drives the solid reactant 11 in the reaction cavity 10 to generate the following exothermic reaction: solid alkali metal oxide + water vapor → solid alkali metal hydroxide + reaction heat, wherein the generated solid alkali metal hydroxide remains in the reaction cavity 10, and the reaction heat released in the reaction is conducted to the tubular electric heater 7 by the spiral hollow perforated fin 8; the high-pressure pump 5 passes the circulating working medium water into the tubular electric heater 7, and the circulating working medium water is vaporized into steam after absorbing heat and enters the steam turbine 2 to do work, the output shaft work drives the generator set 3 to generate electricity and is transmitted to the power grid, the exhaust steam generated by the steam turbine 2 is condensed into circulating working medium water by the condenser 4, and then is sent back to the electric heat-driven thermochemical energy storage reactor 1 by the high-pressure pump 5 to continue heat absorption and circulating work; the above process realizes the discharge process of the Carnot cell system which utilizes the chemical reaction heat of the exothermic reaction to drive the steam power cycle to generate electricity after the release of the stored chemical energy and the latent heat of vaporization.

[0019] The tubular electric heater 7 works as a heat source for driving the thermochemical reaction in the charging mode, and does not work and only functions as a heat transfer pipe in the discharging mode.

[0020] The present application has the following beneficial effects:

[0021] 1. The Carnot cell system based on thermochemical energy storage provided by the present application adopts direct contact heat exchange for the electric heat-driven thermochemical energy storage reactor, so that external electric energy can be converted into heat energy by the tubular electric heating net, and the heat energy can be uniformly and effectively transferred to the reactant through the large-area contact between the spiral hollow perforated fin and the reactant, so as to drive the chemical reaction and convert the heat energy into chemical energy. The utilization rate of the input electric energy and the reactant can be improved.

[0022] 2. The spiral hollow perforated fin of the electric heat-driven thermochemical energy storage reactor in the Carnot cell system based on thermochemical energy storage provided by the present application has the following advantages: the spiral structure can make the solid reactant particles fill the material by gravity, which is convenient and fast; the hollow structure is used to form a steam channel, so that the reaction steam can quickly enter or leave the reaction cavity, and the contact between the water vapor and the reactant is more sufficient, which promotes the chemical reaction in the required direction from the perspective of chemical equilibrium, effectively improves the reaction yield and reaction efficiency, and saves the manufacturing cost.

[0023] 3. The tubular heater of the electric heat-driven thermochemical energy storage reactor in the Carnot cell system based on thermochemical energy storage provided by the present application works as a heat source for driving the thermochemical reaction in the charging mode, and does not work and only functions as a heat transfer pipe in the discharging mode, so that the multifunctional use is realized, the internal space is saved, and the manufacturing cost is reduced.

[0024] 4. The thermal-chemical energy storage Carnot cell system provided by the application separates solid and gaseous reactants / products and blocks air interference in the reaction system through cooperation of the reactor and external steam circulation, thereby improving the overall energy storage performance of the reaction system.

[0025] 5. The thermal-chemical energy storage Carnot cell system provided by the application adopts a steam accumulator to realize regulation of water vapor supply and reflux, effectively ensures material circulation while saving system operation cost, and improves system operation efficiency.

[0026] 6. The thermal-chemical energy storage Carnot cell system provided by the application is suitable for various gas-solid phase heat absorption and release reversible reactions, such as heat absorption and release reactions of magnesium hydroxide and water, thereby having greater application space. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Figure 1 is a schematic diagram of an internal structure of an electrically driven thermal-chemical energy storage reactor.

[0028] Figure 2 Figure 2 is a schematic diagram of an appearance of an electrically driven thermal-chemical energy storage reactor.

[0029] Figure 3 Figure 3 is a schematic diagram of a thermal-chemical energy storage Carnot cell system.

[0030] Figure 4 Figure 4 is a schematic diagram of an energy storage mode of a thermal-chemical energy storage Carnot cell system.

[0031] Figure 5 Figure 5 is a schematic diagram of an energy release mode of a thermal-chemical energy storage Carnot cell system.

[0032] Figure 6 Figure 6 is a schematic diagram of an energy storage mode of an electrically driven thermal-chemical energy storage reactor.

[0033] Figure 7 Figure 7 is a schematic diagram of an energy release mode of an electrically driven thermal-chemical energy storage reactor.

[0034] In the figures, the components and corresponding labels are as follows:

[0035] The electrically driven thermal-chemical energy storage reactor 1, the steam turbine 2, the generator set 3, the condenser 4, the high-pressure pump 5, and the steam accumulator 6, wherein the electrically driven thermal-chemical energy storage reactor 1 comprises a tubular electric heater 7, a spiral hollow fin with holes 8, a steam passage 9, a reaction cavity 10, solid reactants 11, a reactor shell 12, a solid reactant feeding port 13, and a thermal insulation layer 14. DETAILED DESCRIPTION

[0036] The application will be further described in detail below in combination with examples.

[0037] Reference is made toFigure 1 , Figure 2 The internal structure and appearance of the electric-driven thermo-chemical energy storage reactor of the Carnot battery system based on thermo-chemical energy storage are shown in the schematic diagram. The internal structure of the reactor includes a tubular electric heater 7, a spiral hollow perforated fin 8, a steam passage 9, a reaction cavity 10, a solid reactant 11, a reactor shell 12, a solid reactant feeding port 13, and a thermal insulation layer 14.

[0038] The tubular electric heater 7 serves as a heat source for driving the thermo-chemical reaction in the charging mode and plays a role in heat conduction in the discharging mode. The spiral hollow perforated fin 8 can facilitate the filling of solid calcium hydroxide particles and form the steam passage 9, and can also strengthen the conduction of heat. The steam passage 9 is used for the introduction of water vapor. The reaction cavity 10 provides a reaction site for the thermo-chemical reaction. The solid reactant 11 is selected as solid calcium hydroxide particles. The reactor shell 12 is the shell of the electric-driven thermo-chemical energy storage reactor. The solid reactant feeding port 13 is used for filling solid calcium hydroxide particles. The thermal insulation layer 14 is covered on the outside of the reaction shell 12 to reduce heat loss and improve energy conversion efficiency.

[0039] Referring to Figure 2 The electric-driven thermo-chemical energy storage reactor of the Carnot battery system based on thermo-chemical energy storage is shown in the appearance diagram, which is a cylindrical tank, facilitating manufacturing and loading.

[0040] Referring to Figure 3 The schematic diagram of the thermo-chemical energy storage Carnot battery system is shown. The system includes an electric-driven thermo-chemical energy storage reactor 1, a steam turbine 2, a generator set 3, a condenser 4, a high-pressure pump 5, and a steam accumulator 6. The system composed of the above devices can realize the functions of charging and discharging through thermo-chemical reaction and steam circulation.

[0041] The Carnot battery system of thermo-chemical energy storage has two different working modes according to the different needs of energy storage and discharge.

[0042] Charging mode: refer to Figure 4 , Figure 6 The electric energy generated by renewable energy enters the tubular electric heater 7 in the electric-driven thermo-chemical energy storage reactor 1 from the power grid. The tubular electric heater 7 is electrified and generates heat. The generated heat is introduced into the reaction cavity 10 through the spiral hollow perforated fin 8 to heat the solid calcium hydroxide. When the calcium hydroxide is heated to the thermo-chemical reaction temperature, the following endothermic reaction occurs: calcium hydroxide + heat → calcium oxide + water vapor. The generated solid calcium oxide remains in the reaction cavity 10, and the water vapor enters the steam passage 9 through the small hole structure of the spiral hollow perforated fin 8 and is discharged from the electric-driven thermo-chemical energy storage reactor 1, and then enters the steam accumulator 6 for storage. The above process realizes the Carnot battery system charging process, in which the electric energy from the power grid is converted into chemical energy through the heat of chemical reaction of the endothermic reaction, and into latent heat of vaporization through the vaporization process, and is stored respectively.

[0043] Discharge mode: reference Figure 5 , Figure 7 The steam accumulator 6 releases water vapor by pressure regulation, the water vapor enters the reaction cavity 10 through the steam channel 9 and the small hole structure of the spiral hollow perforated fin 8, and drives the solid calcium oxide in it to generate the following exothermic reaction: calcium oxide + water vapor → calcium hydroxide + reaction heat, wherein the generated solid calcium hydroxide remains in the reaction cavity 10, and the reaction heat released by the reaction is conducted to the tubular electric heater 7 by the spiral hollow perforated fin 8. The high-pressure pump 5 passes the circulating working medium water into the tubular electric heater 7, and the circulating working medium water is vaporized into steam after absorbing heat and enters the steam turbine 2 to do work, and the output shaft work drives the generator set 3 to generate electricity and is transmitted to the power grid, the exhaust steam generated by the steam turbine 2 is condensed into circulating working medium water by the condenser 4, and then is sent back to the electric heat-driven chemical energy storage reactor 1 by the high-pressure pump 5 to continue to absorb heat and circulate to do work. The above process realizes the discharge process of the Carnot cell system which uses the chemical reaction heat of the exothermic reaction to drive the steam power cycle to generate electricity after the release of the stored chemical energy and the latent heat of vaporization.

[0044] The above is only the preferred embodiment of the present application, and the purpose, technical scheme and beneficial effects of the present application are further described in detail, and it should be understood that the above is only a specific embodiment of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A Carnot cell system based on thermochemical energy storage, characterized in that, It comprises an electrically driven thermo-chemical energy storage reactor (1), a steam turbine (2), a generator set (3), a condenser (4), a high-pressure pump (5), and a steam accumulator (6); The steam turbine (2) is connected with the generator set (3), and the steam generated by the electrically driven thermo-chemical energy storage reactor (1) drives the steam turbine (2), which in turn drives the generator set (3) to generate electricity; The steam accumulator (6) is connected with the steam channel (9) in the electrically driven thermo-chemical energy storage reactor (1) for storing or providing reaction steam; The high-pressure pump (5) is connected with the tubular electric heater (7) in the electrically driven thermo-chemical energy storage reactor (1), and the exhaust steam generated by the steam turbine (2) is condensed into circulating working fluid water by the condenser (4), which is then sent back to the electrically driven thermo-chemical energy storage reactor (1) by the high-pressure pump (5) to absorb heat and circulate to work; The electrically driven thermo-chemical energy storage reactor (1) comprises an external reactor shell (12) and a tubular electric heater (7) at the center of the reactor shell (12), and the tubular electric heater (7) is surrounded by a spiral hollow perforated fin (8) outside, the outer side of the spiral hollow perforated fin (8) is in contact with the inner wall of the reactor shell (12), the space between the spiral hollow perforated fins (8) is a reaction cavity (10), the top of the spiral hollow perforated fin (8) is not in contact with the reactor shell (12), leaving a cavity for the reaction cavity (10), and the reactor shell (12) is provided with a reactant feeding port (13) at the top, which is in communication with the cavity of the reaction cavity (10), and the solid reactant (11) enters the reaction cavity (10) through the solid reactant feeding port (13); The spiral hollow perforated fin (8) has a spiral structure, a hollow structure, and a mesh surface; the spiral structure is used to facilitate the filling of solid reactant particles by gravity; the hollow structure forms a steam channel (9) to quickly enter or exit the reaction cavity (10); and the fin structure is used to strengthen the heat conduction between the tubular electric heater (7) and the solid reactant (11); The electric grid power drives the filled solid reactant (11) to undergo the following endothermic reaction: Solid alkali metal hydroxide + heat → solid alkali metal oxide + water vapor; Water vapor drives the solid reactant (11) to undergo the following exothermic reaction: solid alkali metal oxide + water vapor → solid alkali metal hydroxide + reaction heat.

2. A Carnot cell system based on thermochemical energy storage according to claim 1, characterized in that, The reactor shell (12) is provided with a heat preservation layer (14) outside.

3. A mode of operation of a Carnot cell system based on thermochemical energy storage according to any of claims 1-2, characterized in that, The method comprises the following steps: a charging mode: the tubular electric heater (7) in the electrically driven thermo-chemical energy storage reactor (1) is heated by the electric grid power, and the generated heat is introduced into the reaction cavity (10) through the spiral hollow perforated fin (8), so that the solid reactant (11) filled therein is heated to a thermo-chemical reaction temperature and undergoes the following endothermic reaction: Solid alkali metal hydroxide + heat → solid alkali metal oxide + water vapor, wherein the generated solid alkali metal oxide remains in the reaction cavity (10), and the water vapor enters the steam passage (9) through the small hole structure of the helical hollow porous fin (8) and is discharged from the electrically driven thermal chemical energy storage reactor (1), and then enters the steam accumulator (6) and is stored; the above process realizes the charging process of the Carnot cell system, that is, the electrical energy from the power grid is converted into chemical energy through the chemical reaction heat of the endothermic reaction, and is converted into latent heat of vaporization through the vaporization process, and is stored respectively; b Discharge mode: the steam accumulator (6) releases water vapor through pressure regulation, and the water vapor enters the reaction cavity (10) through the steam passage (9) and the small hole structure of the helical hollow porous fin (8), and drives the solid reactant (11) therein to undergo the following exothermic reaction: solid alkali metal oxide + water vapor → solid alkali metal hydroxide + reaction heat, wherein the generated solid alkali metal hydroxide remains in the reaction cavity (10), and the reaction heat released by the reaction is conducted to the tubular electric heater (7) by the helical hollow porous fin (8); the high-pressure pump (5) passes the circulating working medium water into the tubular electric heater (7), and the circulating working medium water is vaporized into steam after absorbing heat and enters the steam turbine (2) to do work, and the output shaft drives the generator set (3) to generate electricity and is transmitted to the power grid, and the exhaust steam generated by the steam turbine (2) is condensed into circulating working medium water by the condenser (4), and then is sent back to the electrically driven thermal chemical energy storage reactor (1) by the high-pressure pump (5) to continue to absorb heat and circulate to do work; the above process realizes the discharge process of the Carnot cell system, that is, after the release of the stored chemical energy and latent heat of vaporization, the chemical reaction heat of the exothermic reaction is used to drive the steam power cycle to generate electricity.

4. A mode of operation of a Carnot cell system based on thermochemical energy storage according to claim 3, characterized in that, The tubular electric heater (7) works as a heat source for driving the thermal chemical reaction in the charging mode, and does not work in the discharge mode, only serving as a heat transfer pipe.

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