Steam extraction backheating type Carnot battery

Abstract

The invention belongs to the technical field of energy storage, and particularly relates to a steam extraction regenerative Carnot battery. The invention provides a steam extraction and heat regeneration type Carnot battery. The steam extraction and heat regeneration type Carnot battery is divided into a single-stage steam extraction and heat regeneration mode and a double-stage steam extraction and heat regeneration mode. According to the technical scheme, a mixed heat exchanger and an additional working medium pump are introduced in a single-stage steam extraction and heat regeneration mode, and two mixed heat exchangers and two additional working medium pumps are introduced in a double-stage steam extraction and heat regeneration mode. According to the heat regeneration mode, the heat efficiency, the round-trip efficiency and the # imgabs0 # efficiency are greatly improved, and certain guidance is provided for related work for improving the performance index of the heat-integrated Carnot battery.

Description

Technical Field

[0001] The invention belongs to the field of energy storage, and in particular relates to an energy storage method of a regenerative Carnot battery. Background Art

[0002] In order to improve global climate change, reduce carbon dioxide emissions and reduce the use of fossil fuels, it is an effective way. In order to solve the intermittent shortage of renewable energy such as wind and solar energy and balance the mismatch between energy supply and demand between the power grid and users, a flexible and convenient energy storage technology is urgently needed.

[0003] In the past few decades, researchers have proposed energy storage technologies such as pumped storage, compressed air storage, lithium batteries and flow batteries, but all of the above technologies have certain defects: pumped storage and compressed air storage are easily restricted by geographical conditions; electrochemical energy storage technologies such as lithium batteries and flow batteries are only suitable for small-scale electrical energy storage, and have high costs and short lifespans. In order to improve the problems of the above energy storage technologies, a new energy storage technology that is not restricted by geographical conditions, has low costs and a long lifespan, the Carnot battery, came into being.

[0004] Carnot batteries are usually composed of a heat pump subsystem, a heat storage subsystem and a heat engine subsystem. Among them, the heat engine subsystem can be mainly divided into two types: Brayton heat engine subsystem and Rankine heat engine subsystem. A large number of previous studies have shown that the temperature of Carnot batteries using Brayton heat engines is as high as 500°C, and the thermal efficiency is only 60%. The thermal efficiency of Carnot batteries using Rankine heat engines can also reach this level, and compared with Carnot batteries using Brayton heat engines, Carnot batteries using Rankine heat engines have the following advantages: First, the maximum temperature of Carnot batteries using Rankine heat engines is usually below 200°C, the operation is safer, and the heat loss is also smaller; secondly, the mass flow rate of the heat storage fluid is lower, the volume of the heat storage tank is smaller, the cost is less, and the economic performance is better; finally, the Carnot battery using the Rankine heat engine can improve the round-trip efficiency by adding a low-temperature integrated heat source. At this time, the Carnot battery using the Rankine heat engine can be called a heat-integrated Carnot battery, and the Carnot battery mentioned in the present invention is assumed to be a heat-integrated Carnot battery by default. Summary of the invention

[0005] In order to further improve the thermal efficiency of the Carnot battery discharge cycle and In order to improve efficiency and reduce the levelized cost of electricity, the present invention provides a Carnot battery with a steam extraction and heat recovery function. The steam extraction and heat recovery method can be divided into a single-stage steam extraction method and a multi-stage steam extraction method. Steam extraction and heat recovery is to extract a small amount of steam with relatively high pressure and temperature that has not yet fully expanded to do work from the appropriate part of the turbine to heat the remaining working fluid. This part of the steam extraction does not pass through the condenser and does not release heat to the cold source, but directly enters the hybrid heat exchanger to heat the remaining working fluid to achieve the purpose of heat recovery.

[0006] The technical solution adopted by the present invention is:

[0007] A Carnot battery using a steam extraction heat recovery method includes a heat pump subsystem, a heat storage subsystem and a Rankine cycle subsystem. The heat pump subsystem includes an evaporator 1, a compressor, a condenser 1 and a throttle valve. The function of the evaporator 1 is to provide a working fluid to absorb heat from a low-temperature integrated heat source. The function of the compressor is to compress the working fluid to increase the temperature and pressure of the working fluid. The function of the condenser 1 is to transfer the heat of the working fluid to the heat storage subsystem. The function of the throttle valve is to adiabatically throttle the working fluid to reduce the temperature and pressure of the working fluid.

[0008] The heat storage subsystem includes a heat storage tank and a cold storage tank. The heat storage tank is used to provide a place for storing hot working fluid, and the cold storage tank is used to provide a place for storing cold working fluid.

[0009] The Rankine cycle subsystem can be divided into a single-stage extraction steam heat recovery Rankine cycle subsystem and a double-stage extraction steam heat recovery Rankine cycle subsystem.

[0010] The single-stage steam extraction heat recovery Rankine cycle subsystem includes an evaporator 2, a turbine, a condenser 2, a working fluid pump 1, a working fluid pump 2 and a hybrid heat exchanger. The function of the evaporator 2 is to provide a place for the working fluid to absorb the heat stored in the heat storage subsystem. The function of the turbine is to expand the working fluid and output electrical energy. The function of the condenser 2 is to condense the working fluid. Assume that the steam extraction volume is x c1 The function of the hybrid heat exchanger is to receive the mass fraction of the incompletely expanded work in the turbine x c1 The mass fraction of the working fluid and the fully expanded work is (1-x c1 ) mixed heat exchange of working fluid. The function of the working fluid pump 1 is to pressurize all the working fluids after being fully mixed and heat exchanged in the hybrid heat exchanger, and the function of the working fluid pump 2 is to pressurize the mass fraction (1-x c1 )’s working fluid is pressurized.

[0011] The multi-stage steam extraction and heat recovery Rankine cycle subsystem also includes an evaporator 2, a turbine, and a condenser 2. The difference from the single-stage steam extraction and heat recovery Rankine cycle subsystem is that for each additional stage of steam extraction, an additional working fluid pump and an additional hybrid heat exchanger are added. Therefore, in the multi-stage steam extraction and heat recovery subsystem, the number of working fluid pumps is the number of steam extraction stages plus 1, and the number of hybrid heat exchangers remains the same as the number of steam extraction stages. The present invention only introduces the two-stage steam extraction and heat recovery Rankine cycle subsystem in detail here.

[0012] The two-stage steam extraction and heat recovery Rankine cycle subsystem includes an evaporator 2, a turbine, a condenser 2, a working fluid pump 1, a working fluid pump 2, a working fluid pump 3, a hybrid heat exchanger 1 and a hybrid heat exchanger 2. The functions of the evaporator 2, the turbine and the condenser 2 are the same as those of the single-stage steam extraction and heat recovery Rankine cycle subsystem. Assume that the first steam extraction volume is x c1 , the second extraction volume is x c2 The function of the hybrid heat exchanger 1 is to provide a mass fraction of incomplete expansion work x c1 The working fluid and the remaining mass fraction are (1-x c1 The function of the hybrid heat exchanger 2 is to provide a mass fraction of x for the incomplete expansion work. c2 The mass fraction of the working fluid and the work done by complete expansion is (1-x c1 -x c2 ) is a place for mixing and heat exchanging working fluids. The working fluid pump 1 is used to pressurize all the working fluids after being fully mixed and heat exchanged in the hybrid heat exchanger 1, and the working fluid pump 2 is used to pressurize the working fluids after being fully mixed and heat exchanged in the hybrid heat exchanger 2. c1 ) is pressurized. The working fluid pump 3 is used to pressurize the working fluid having a mass fraction of (1-x c1 -x c2 )’s working fluid is pressurized.

[0013] As a preferred embodiment of the present invention, the steam extraction heat recovery mode is set to a single-stage steam extraction heat recovery mode and a double-stage steam extraction heat recovery mode.

[0014] As a preferred solution of the present invention, the steam extraction heat recovery method is different from the common heat recovery method. The common heat recovery system adds a heat regenerator between the turbine and the condenser 2, thereby recovering and utilizing the heat of the valve steam with a certain temperature.

[0015] As a preferred embodiment of the present invention, the working fluid of the heat pump subsystem and the Rankine cycle subsystem can be organic fluids such as R1233zd(E), and the working fluid of the heat storage subsystem can be easily obtained fluids with large specific heat capacity such as water.

[0016] The beneficial effects of the present invention are:

[0017] The present invention introduces a hybrid heat exchanger and an additional working fluid pump into the Rankine cycle subsystem to form a single-stage steam extraction and heat recovery Rankine cycle subsystem. Two hybrid heat exchangers and two additional working fluid pumps are introduced into the Rankine cycle subsystem to form a two-stage steam extraction and heat recovery Rankine cycle subsystem. After this heat recovery method, the thermal efficiency of the Rankine cycle will be improved. Therefore, the steam extraction and heat recovery greatly improves the performance of the Carnot battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a single-stage steam extraction regenerative Carnot battery;

[0019] Figure 2 It is a schematic diagram of a double-stage steam extraction and regenerative Carnot battery;

[0020] Reference numerals:

[0021] 1- Heat pump subsystem;

[0022] 11- evaporator 1;

[0023] 12-Compressor;

[0024] 13- condenser 1;

[0025] 14-Throttle valve;

[0026] 2- Thermal storage subsystem;

[0027] 21-heat storage tank;

[0028] 22-cold storage tank;

[0029] 3-Rankine cycle subsystem;

[0030] 31- evaporator 2;

[0031] 32-turbine;

[0032] 33- condenser 2;

[0033] 34-working fluid pump 1;

[0034] 35- Single-stage steam extraction and regenerative Carnot battery working fluid pump 2;

[0035] 36- Single-stage extraction steam regenerative Carnot battery hybrid heat exchanger;

[0036] 35'-two-stage steam extraction and regenerative Carnot battery working fluid pump 2;

[0037] 36'-two-stage steam extraction and regenerative Carnot battery working fluid pump 3;

[0038] 37-Two-stage extraction steam regenerative Carnot battery hybrid heat exchanger 1;

[0039] 38-Two-stage extraction steam regenerative Carnot battery hybrid heat exchanger2. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

[0041] Figure 1 Schematic diagram of a single-stage steam extraction and regenerative Carnot battery provided by the present invention. As shown in the figure, the single-stage steam extraction and regenerative Carnot battery provided by the present invention includes:

[0042] The heat pump subsystem 1 includes an evaporator 11, a compressor 12, a condenser 13 and a throttle valve 14 connected in sequence. When the system is in the charging working mode, the working fluid first absorbs heat from the low-temperature integrated heat source in the evaporator 11 to become superheated, and then enters the compressor 12. The compressor 12 receives electricity from the power grid and drives the compressor 12 to compress the working fluid, so that the temperature and pressure of the working fluid are increased. Next, the working fluid releases heat to the heat storage subsystem 2 in the condenser 13. Then the working fluid is adiabatically throttled in the throttle valve 14, the temperature and pressure are reduced, and enters the evaporator 11 for the next cycle.

[0043] The heat storage subsystem 2 includes a heat storage tank 21 and a cold storage tank 22 connected in sequence. When the system is in the charging working mode, the working fluid absorbs heat in the condenser 13 and stores it in the heat storage tank 21. When the system is in the discharging working mode, the working fluid releases heat in the evaporator 31 and then enters the cold storage tank 22.

[0044] The Rankine cycle subsystem 3 includes an evaporator 31, a turbine 32, a condenser 33, a working fluid pump 35, a hybrid heat exchanger 36 and a working fluid pump 34 connected in sequence. When the system is in the discharge working mode, the working fluid absorbs heat in the evaporator 31, enters the turbine 32 to expand and do work, and extracts a mass fraction x from an appropriate part of the turbine 32. c1 , the steam with relatively high pressure and temperature that has not been fully expanded and performed work enters the hybrid heat exchanger 36 to heat the condensing medium. The mass fraction of the remaining fully expanded work is (1-x c1 ) enters the condenser 33 and is condensed by the condensate, then pressurized by the pump 35, and then the mass fraction of the work done by the uncompleted expansion is x c1 The steam is mixed and heat exchanged in the mixing heat exchanger 36, and finally enters the evaporator 31 after being pressurized by the pump 34 to complete the next cycle.

[0045] Figure 2 Schematic diagram of a double-stage steam extraction and regenerative Carnot battery provided by the present invention. As shown in the figure, the double-stage steam extraction and regenerative Carnot battery provided by the present invention includes:

[0046] Heat pump subsystem: Same as the heat pump subsystem of the single-stage steam extraction heat recovery Carnot battery.

[0047] Thermal storage subsystem: The same as the thermal storage subsystem of the single-stage steam extraction heat recovery Carnot battery.

[0048] Rankine cycle subsystem: Based on the single-stage steam extraction and heat recovery method, one more stage is added, including the evaporator 31, turbine 32, condenser 33, working fluid pump 36', hybrid heat exchanger 38, working fluid pump 35', hybrid heat exchanger 37 and working fluid pump 34 connected in sequence. When the system is in the discharge working mode, the mass fraction x is first extracted at the appropriate position c1 The working fluid enters the hybrid heat exchanger 37; then a second extraction with a mass fraction of x is conducted at another suitable location. c2 The working fluid enters the hybrid heat exchanger 38; the remaining mass fraction is (1-x c1 -x c2 ) The fully expanded working fluid absorbs heat in the evaporator 31 and enters the turbine 32 to expand and work, then passes through the condenser 33 to be condensed by condensed water, and then is pressurized by the working fluid pump 36' and enters the hybrid heat exchanger 38. The mass fraction of the incompletely expanded working fluid is x c2 The working fluid mixed heat exchange, at this time the mass fraction of the working fluid becomes (1-x c1 ), then enters the working fluid pump 35' and is pressurized before entering the hybrid heat exchanger 37, and the mass fraction of the work done by the incomplete expansion is x c1 The working fluid is mixed for heat exchange, and after being fully mixed, it enters the working fluid pump 34 for pressurization, and finally enters the evaporator 31 for the next cycle.

[0049] After adding an additional working fluid pump and a hybrid heat exchanger, the steam extraction regenerative Carnot battery has a higher thermal energy utilization rate, higher thermal efficiency, and a round-trip efficiency and Higher efficiency, more electrical energy output and lower levelized cost of electricity.

[0050] In summary, this patent has a good guiding significance for the research on improving the performance parameters of Carnot batteries.

[0051] This patent is not limited to the above optional implementation methods. Anyone can derive other forms of products under the inspiration of this patent. However, no matter what changes are made in its shape or structure, all technical solutions that fall within the scope of the claims of the present invention are within the scope of protection of this patent.

Claims

1. Steam extraction and regenerative Carnot battery, characterized in that: include: The charging subsystem (1) includes an evaporator 1 (11), a compressor (12), a condenser 1 (13) and a throttle valve (14). The evaporator 1 is used to provide a place for the working fluid to absorb heat from a low-temperature integrated heat source, the compressor is used to compress the working fluid and increase the temperature and pressure of the working fluid, the condenser 1 is used to provide a place for transferring the heat of the working fluid to the heat storage subsystem, and the throttle valve is used to adiabatically throttle the working fluid and reduce the temperature and pressure of the working fluid.

2. Heat storage subsystem (2): including a heat storage tank (21) and a cold storage tank (22). The heat storage tank is used to store hot working fluids, and the cold storage tank is used to store cold working fluids.

3. Discharge subsystem (3): It is divided into a single-stage steam extraction and heat recovery mode and a two-stage steam extraction and heat recovery mode. The components of the single-stage steam extraction and heat recovery mode include an evaporator 2 (31), a turbine (32), a condenser 2 (33), a working fluid pump 1 (34), a working fluid pump 2 (35) and a mixed heat exchanger (36). The components of the two-stage steam extraction and heat recovery mode include an evaporator 2 (31), a turbine (32), a condenser 2 (33), a working fluid pump 1 (34), a working fluid pump 2 (35'), a working fluid pump 3 (36'), a mixed heat exchanger 1 (37) and a mixed heat exchanger 2 (38). The function of the evaporator 2 is to provide a place for the working fluid to absorb and store heat in the heat storage subsystem. The function of the turbine is to expand the working fluid to do work and output electrical energy to the outside. The function of the condenser 2 is to condense the working fluid. The function of the mixed heat exchanger is to provide a place for the working fluid to perform mixed heat exchange. The function of the working fluid pump is to pressurize the working fluid.

4. The steam extraction regenerative Carnot battery according to claim 1, characterized in that: In a single-stage steam extraction regeneration Carnot battery, compared with a Carnot battery with a basic configuration, the system component has an additional hybrid heat exchanger (36) and an additional working fluid pump 2 (35) between the condenser 2 (33) and the working fluid pump 1 (34). In a double-stage steam extraction regeneration Carnot battery, compared with a Carnot battery with a basic configuration, the system component has an additional hybrid heat exchanger 1 (37) and a hybrid heat exchanger 2 (38), a working fluid pump 2 (35') and a working fluid pump 3 (36') between the condenser 2 (33) and the working fluid pump 1 (34).

5. The steam extraction regenerative Carnot battery according to claim 1, characterized in that: In a single-stage steam extraction and regeneration Carnot battery, a hybrid heat exchanger 1 (36) is connected to a turbine (32) to receive a portion of the working fluid that has not yet fully expanded to perform work. A hybrid heat exchanger 1 (36) is connected to a working fluid pump 2 (35) to receive the remaining working fluid after fully expanding to perform work and cooling. A hybrid heat exchanger 1 (36) is connected to a working fluid pump 1 (34) to send all the working fluid after sufficient mixing and heat exchange to the working fluid pump 1 (34) for pressurization. In a two-stage steam extraction and regeneration Carnot battery, a hybrid heat exchanger 1 (37) is connected to a turbine (32) to receive a mass fraction of x of the first extracted steam that has not yet fully expanded to perform work. c1 The hybrid heat exchanger 1 (37) is connected to the working fluid pump 2 (35') for receiving the working fluid with a mass fraction of (1-x c1 ) of the remaining working fluid. The hybrid heat exchanger 1 (37) is connected to the working fluid pump 1 (34) to send all the working fluid after sufficient heat exchange into the working fluid pump 1 (34) for pressurization. The hybrid heat exchanger 2 (38) is connected to the turbine (32) to receive the mass fraction of the second extracted fluid that has not yet fully expanded and done work, which is x c2 The hybrid heat exchanger 2 (38) is connected to the working fluid pump 3 (36') for receiving the fully expanded mass fraction (1-x c1 -x c2 ) of the remaining working fluid. The mixing heat exchanger 2 (38) is connected to the working fluid pump 2 (35') to transfer the mass fraction of the fully mixed working fluid to (1-x c1 ) is sent to the working fluid pump 2 (35') for pressurization.

6. The Carnot battery using the steam extraction and heat recovery method according to claim 1, characterized in that: Instead of simply utilizing the valve steam heat for heat recovery, the heat of the working fluid that has not yet fully expanded in the turbine is utilized for heat recovery, wherein the single-stage steam extraction heat recovery Carnot battery is utilized once, and the double-stage steam extraction heat recovery Carnot battery is utilized twice.

7. The Carnot battery using steam extraction and heat recovery according to claim 1, characterized in that: The working fluid of the heat pump subsystem and the Rankine cycle subsystem can be organic matter such as R1233zd(E), and the working fluid of the heat storage subsystem can be a fluid with large specific heat capacity and easy to obtain such as water.

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