Carnot battery system based on phase change cold storage energy storage and its multi-mode operation method

Abstract

The present invention discloses a Carnot battery system based on phase-change cold storage and energy storage and a multi-mode operation method thereof. The Carnot battery system includes a vapor compression refrigeration unit, a phase-change cold storage device and a power circulation unit. In the charging stage, the vapor compression refrigeration unit is used to generate cold energy using off-peak electricity; in the energy storage stage, the cold energy produced by the vapor compression refrigeration unit is stored at a high density by the phase-change cold storage device; in the discharging stage, the stored cold energy is used as a cold source and the external low-temperature waste heat is used as a heat source, and the power circulation unit is used to simultaneously utilize the cold and heat energy for heat-work conversion to release electrical energy; the Carnot battery system proposed in the present invention can improve the round-trip efficiency and energy storage density of the energy storage system, reduce the energy storage cost, and contribute to large-scale long-term energy storage; the multi-mode operation method proposed in the present invention can make full use of different types of low-temperature heat sources through the scheduling of the phase-change cold storage device and the charge and discharge cycle to meet the cold and electricity energy needs of the user side.

Description

Technical Field

[0001] The present invention relates to the field of novel thermomechanical energy storage technology, and in particular to a Carnot battery system based on phase change cold energy storage and a multi-mode operation method thereof. Background Art

[0002] As the share of renewable energy generation continues to increase, energy storage technology is becoming increasingly important in enhancing the stability and reliability of power systems. The intermittent and unstable nature of renewable energy sources, such as solar and wind power, makes it difficult to ensure stable power system operation. This issue has driven the development of various large-scale, long-duration energy storage technologies, including pumped hydro, compressed air storage, gravity storage, and Carnot batteries.

[0003] Carnot battery is an energy storage technology based on thermodynamic cycle and heat storage, which converts electrical energy into heat through heat pump The heat is stored and converted back into electrical energy through a power cycle when needed. Depending on the storage temperature and the operating conditions of the thermodynamic cycle, Carnot batteries can be divided into high-temperature Brayton-Carnot batteries and low-temperature Rankine-Carnot batteries. The heat storage temperature of high-temperature Brayton-Carnot batteries is usually higher than 500°C, and the requirements for materials and equipment under high temperature conditions are stringent, and the technical maturity and cost of the system face great challenges. In contrast, low-temperature Rankine-Carnot batteries have significant advantages in terms of technical maturity and economic cost, and can effectively utilize low-temperature waste heat to improve the round-trip efficiency of the energy storage system. Currently, existing low-temperature Rankine-Carnot batteries are generally heat storage types, mainly including sensible heat storage, phase change heat storage, and thermochemical heat storage. However, the heat storage tanks using sensible heat storage are bulky, resulting in low energy storage density of the system; while the use of phase change heat storage and thermochemical heat storage is costly, which is not conducive to large-scale and long-term energy storage. For example, Li Wei et al. (CN118030216A) proposed a hydrated salt adsorption thermochemical Carnot battery system and method using air as a heat source. However, it only uses the environment as a heat source, the system's round-trip efficiency is low, and thermochemical heat storage is currently difficult to promote and apply on a large scale. On the other hand, the heat storage-type Carnot battery based on heat pumps does not fully utilize waste heat. During the non-charging phase (heat storage, discharge, and static), the waste heat is almost difficult to be effectively utilized, resulting in a waste of waste heat resources. For example, Pei Gang et al. (CN115468317A) proposed a Carnot battery energy storage device based on the cascade utilization of solar photovoltaic and thermal energy. During the charging phase, thermal energy is used as the heat source for the heat pump to improve system efficiency. In addition to thermal energy, there is also a large amount of low-temperature waste heat (such as geothermal energy, industrial waste heat, data center liquid cooling waste heat, etc.) that is almost uninterrupted throughout the year. The heat source utilization rate of the thermal storage-type Carnot battery is low. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a Carnot battery system based on phase change cold storage and energy storage and a multi-mode operation method thereof, wherein a vapor compression refrigeration unit is used to generate cold energy using off-peak electricity during the charging stage; during the energy storage stage, the cold energy produced by the vapor compression refrigeration unit is stored by a phase change cold storage device; during the discharge stage, the stored cold energy is used as a cold source and the external low-temperature waste heat is used as a heat source, and a power circulation unit is used to simultaneously utilize cold and heat energy for heat-to-work conversion to release electrical energy; compared with the heat storage type Carnot battery in the prior art, it can improve the round-trip efficiency and energy storage density of the energy storage system, reduce the energy storage cost, contribute to large-scale long-term energy storage and make full use of low-temperature heat sources; the multi-mode operation method proposed in the present invention can make full use of different types of low-temperature heat sources through the scheduling of phase change cold storage devices and charge and discharge cycles to meet the cold and electricity energy needs of the user side.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The Carnot battery system based on phase-change cold storage energy storage includes a vapor compression refrigeration unit, a phase-change cold storage device 6, and a power circulation unit; the vapor compression refrigeration unit generates cold energy using off-peak electricity, and the vapor compression refrigeration unit is connected to the phase-change cold storage device 6 via a refrigerant circuit; the phase-change cold storage device 6 is used to store the cold energy generated by the vapor compression refrigeration unit; the power circulation unit is connected to the phase-change cold storage device 6 via a refrigerant circuit, and the heat energy inlet of the power circulation unit is connected to the low-temperature waste heat outlet of the low-temperature heat source module 11. The power circulation unit is used to simultaneously utilize the cold energy stored in the phase-change cold storage device 6 and the heat energy of the low-temperature heat source in the low-temperature heat source module 11 to generate electricity;

[0007] The power inlet of the vapor compression refrigeration unit is connected to the power outlet of the renewable energy power generation module 12, and is used to transmit the power generated by the renewable energy power generation module 12 to the vapor compression refrigeration unit for conversion into cold energy;

[0008] The power output shaft of the power circulation unit is connected to the power input shaft of the generator, and the power outlet of the generator is connected to the power inlet of the power grid 13, so as to convert the mechanical energy generated in the power circulation unit into electrical energy through the generator and transmit it to the power grid 13 for transmission to the user side for use; or the power outlet of the generator is connected to the power inlet of the vapor compression refrigeration unit, so as to re-transmit the excess electrical energy generated by the power circulation unit to the vapor compression refrigeration unit for conversion into cold energy.

[0009] The vapor compression refrigeration unit includes a refrigeration condenser 2, a throttle valve 3, a refrigeration evaporator 4, and a compressor 5; the power inlet of the compressor 5 is connected to the power outlet of the renewable energy power generation module 12, and the renewable energy is transported to the compressor 5 to supply power to the compressor 5; the outlet of the compressor 5 is connected to the high-temperature side inlet of the refrigeration condenser 2, and the high-temperature side outlet of the refrigeration condenser 2 is connected to the low-temperature side inlet of the refrigeration evaporator 4 through the throttle valve 3; the working fluid is compressed to a high-pressure state by the compressor 5, and releases heat through the refrigeration condenser 2. The working fluid enters the throttle valve 3 for throttling and pressure reduction, and then enters the refrigeration evaporator 4 to absorb heat. The heat after heat exchange in the refrigeration condenser 2 is released into the environment.

[0010] The phase change cold storage device 6 is connected to the refrigeration evaporator 4 through a refrigerant circuit, and is used to absorb the cold energy provided by the refrigeration evaporator 4; the phase change cold storage device 6 is connected to the heat engine condenser 7 through a refrigerant circuit, and is used to provide cold energy to the heat engine condenser 7.

[0011] The power circulation unit includes a heat engine condenser 7, a working fluid pump 8, a heat engine evaporator 9, and a turbine expander 10; the low-temperature side outlet of the heat engine evaporator 9 is connected to the inlet of the turbine expander 10, the outlet of the turbine expander 10 is connected to the high-temperature side inlet of the heat engine condenser 7, the high-temperature side outlet of the heat engine condenser 7 is connected to the inlet of the working fluid pump 8, and the outlet of the working fluid pump 8 is connected to the low-temperature side inlet of the heat engine evaporator 9; the power output shaft of the turbine expander 10 is connected to the power input shaft of the generator, and the power outlet of the generator is connected to the power of the grid 13. The energy inlet is connected; the low-temperature waste heat outlet of the low-temperature heat source module 11 is connected to the high-temperature side inlet of the heat engine evaporator 9, and the high-temperature side outlet of the heat engine evaporator 9 is connected to the low-temperature waste heat inlet of the low-temperature heat source module 11; the working fluid cooled by the heat engine condenser 7 is pressurized by the working fluid pump 8 and then heat-exchanged with the heat energy of the low-temperature heat source in the low-temperature heat source module 11 absorbed in the heat engine evaporator 9 to increase the temperature, reaching a high-temperature and high-pressure state, and then enters the turbine expander 10 to perform expansion work, drive the generator to rotate and generate electricity, and transmit the generated electricity to the power grid 13.

[0012] The power circulation unit also includes a preheater 14, the low-temperature side inlet of the preheater 14 is connected to the outlet of the working fluid pump 8, and the low-temperature side outlet of the preheater 14 is connected to the low-temperature side inlet of the heat engine evaporator 9. The preheater 14 uses the air with a higher temperature during the day to preheat the working fluid.

[0013] The power cycle system also includes an intercooler 15, the high-temperature side inlet of the intercooler 15 is connected to the outlet of the high-pressure cylinder of the turbine expander 10, and the high-temperature side outlet of the intercooler 15 is connected to the inlet of the low-pressure cylinder of the turbine expander 10. The intercooler 15 is used to reduce the working medium temperature at the outlet of the turbine expander 10.

[0014] The power cycle system also includes a regenerator 16, the low-temperature side inlet of the regenerator 16 is connected to the outlet of the working fluid pump 8, and the low-temperature side outlet of the regenerator 16 is connected to the low-temperature side inlet of the heat engine evaporator 9, so that the working fluid is further preheated through the regenerator 16; the high-temperature side inlet of the regenerator 16 is connected to the outlet of the turbine expander 10, and the high-temperature side outlet of the regenerator 16 is connected to the high-temperature side inlet of the heat engine condenser 7, so that the high-temperature working fluid at the outlet of the turbine expander 10 is precooled through the regenerator 16.

[0015] The circulating working fluid of the vapor compression refrigeration unit adopts an organic working fluid or a natural working fluid, the organic working fluid is R1234yf or R1234ze(E), and the natural working fluid is ammonia or carbon dioxide;

[0016] The phase change cold storage device 6 is a coil-type phase change cold storage tank or a packaged ice-type phase change cold storage tank for storing a cold storage medium; when the required phase change temperature is zero degrees Celsius, the cold storage medium is ice water; when the required phase change temperature is below zero degrees Celsius, the cold storage medium is eutectic ice; when the required phase change temperature is above zero degrees Celsius, the cold storage medium is gas hydrate; the coolant is ethylene glycol or carbon dioxide; and the refrigerant is chilled water or ethylene glycol.

[0017] The circulating working fluid of the power cycle system is an organic working fluid, specifically R1234yf or R1234ze(E).

[0018] The low-temperature heat source in the low-temperature heat source module 11 is solar energy, geothermal energy, industrial waste heat, regional heating network or data center waste heat.

[0019] The present invention also provides a multi-mode operation method of a Carnot battery system based on phase change cold storage energy storage, comprising:

[0020] In charging mode, the vapor compression refrigeration unit operates at night, compressing the working fluid to a high-pressure state through the compressor 5. The working fluid then releases heat through the refrigeration condenser 2. The throttled low-temperature working fluid absorbs heat in the refrigeration evaporator 4 and transfers the cold energy to the phase-change cold storage device 6 through the refrigerant loop. The liquid cold storage medium in the phase-change cold storage device 6 solidifies into a solid state, consuming off-peak electricity for cooling. If the user has a cooling energy demand at this time, the refrigerant loop can directly supply cooling energy.

[0021] In the energy storage mode, the cold energy produced by the vapor compression refrigeration unit is stored in the phase change cold storage device 6; if the user side has a cold energy demand at this time, the cold energy can be taken from the phase change cold storage device 6 through the refrigerant circuit;

[0022] In the discharge mode, the power circulation unit operates, and the cold energy stored in the phase change cold storage device 6 is provided to the heat engine condenser 7 of the power circulation unit as a cold source through the refrigerant circuit. The working fluid cooled by the heat engine condenser 7 is pressurized by the working fluid pump 8, and absorbs the heat energy of the external low-temperature heat source in the heat engine evaporator 9 to reach a high temperature and high pressure state, and then enters the turbine expander 10 to perform expansion work, drive the generator to generate electricity, and output electrical energy; at this time, if the user side has a cold energy demand, it can take cold from the phase change cold storage device 6 through the refrigerant circuit.

[0023] In the static mode, there is no cold storage as the cold source of the power circulation unit. Air or cooling water in the ambient state can be transported to the thermal engine condenser 7 of the power circulation unit as the cold source; at this time, the power circulation unit uses the environment and low-temperature waste heat as cold and heat sources to convert heat into work, output electrical energy, and realize the full utilization of the low-temperature heat source; at this time, if the user side has both electricity and refrigeration needs, the mechanical energy generated by the power circulation unit can be converted into electrical energy through the generator to supply the steam compression refrigeration unit for operation, thereby realizing the output of cold energy.

[0024] Compared with the existing technology, the advantages of the present invention are:

[0025] 1. The Carnot battery system proposed in the present invention utilizes the diurnal temperature difference, i.e., the low nighttime temperature, to improve the coefficient of performance of the vapor compression refrigeration unit by cooling (charging) and storing cold at night and generating electricity using low-temperature waste heat and stored cold during the day. During the day, when the temperature is high, air preheating can be used to improve the power generation efficiency of the power circulation unit, thereby improving the round-trip efficiency of the entire Carnot battery system. Furthermore, the system can utilize the difference in peak and valley electricity prices, i.e., charging at night when electricity prices are low and discharging during the day when electricity prices are high, thereby improving the economic efficiency of the energy storage system and shortening the payback period.

[0026] 2. The Carnot battery system proposed in this invention achieves high-density storage and release of low-temperature cold energy by adopting a phase-change cold storage device. Commonly used ice water as the energy storage medium has high latent heat properties, providing large-capacity cold energy storage in a relatively small volume, which can improve the system's energy storage density. Furthermore, the high maturity of ice storage technology and the low-cost cold storage medium can ensure low-cost scalability of system capacity.

[0027] 3. The multi-mode operation method proposed in this invention enables the Carnot battery system to operate in multiple modes. By utilizing a phase-change cold storage device and scheduling the charge-discharge cycle, it can achieve cooling and electricity synergy, shaving power system peaks while simultaneously meeting user-side cooling and electricity energy needs. It is also suitable for a variety of medium- and low-temperature heat sources, enabling full recovery and utilization of daytime solar thermal energy or other year-round low-temperature waste heat.

[0028] In summary, compared with the prior art, the present invention utilizes low-priced nighttime electricity for cooling by adopting a vapor compression refrigeration unit during the charging phase; during the energy storage phase, the cold energy produced by the vapor compression refrigeration unit is stored by a phase change cold storage device; during the discharge phase, the stored cold energy is used as a cold source, and external low-temperature waste heat is used as a heat source, and a power circulation unit is used to convert cold and heat energy into heat-to-work to release electrical energy; compared with the heat storage-type Carnot battery in the prior art, the round-trip efficiency and energy storage density of the energy storage system can be improved, the energy storage cost can be reduced, and it is conducive to large-scale long-term energy storage and can fully utilize the low-temperature heat source. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of the phase-change cold-storage energy storage Carnot battery system of Example 1.

[0030] Figure 2 This is a schematic diagram of the structure of the phase-change cold storage energy storage Carnot battery system of Example 2.

[0031] Figure 3 This is a structural diagram of the phase-change cold storage energy storage Carnot battery system of Example 3.

[0032] Figure 4 This is a schematic structural diagram of the phase-change cold energy storage Carnot battery system of Example 4.

[0033] In the figure: cooling tower 1, refrigeration condenser 2, throttle valve 3, refrigeration evaporator 4, compressor 5, phase change cold storage device 6, heat engine condenser 7, working fluid pump 8, heat engine evaporator 9, turbine expander 10, low-temperature heat source module 11, renewable energy module 12, power grid 13, preheater 14, intercooler 15, regenerator 16. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0035] Example 1

[0036] The Carnot battery system based on phase-change cold storage energy storage includes a vapor compression refrigeration unit, a phase-change cold storage device 6, and a power circulation unit; the vapor compression refrigeration unit generates cold energy using off-peak electricity, and the vapor compression refrigeration unit is connected to the phase-change cold storage device 6 via a refrigerant circuit; the phase-change cold storage device 6 is used to store the cold energy generated by the vapor compression refrigeration unit; the power circulation unit is connected to the phase-change cold storage device 6 via a refrigerant circuit, and the heat energy inlet of the power circulation unit is connected to the low-temperature waste heat outlet of the low-temperature heat source module 11. The power circulation unit is used to simultaneously utilize the cold energy stored in the phase-change cold storage device 6 and the heat energy of the low-temperature heat source in the low-temperature heat source module 11 to generate electricity;

[0037] The power inlet of the vapor compression refrigeration unit is connected to the power outlet of the renewable energy power generation module 12, and the power generated by the renewable energy power generation module 12 is transmitted to the vapor compression refrigeration unit to be converted into cold energy;

[0038] The power output shaft of the power circulation unit is connected to the power input shaft of the generator, and the power outlet of the generator is connected to the power inlet of the power grid 13. The mechanical energy generated in the power circulation unit is converted into electrical energy through the generator and transmitted to the power grid 13 for transmission to the user side for use; or the power outlet of the generator is connected to the power inlet of the vapor compression refrigeration unit, and the excess electrical energy generated by the power circulation unit is re-transmitted to the vapor compression refrigeration unit for conversion into cold energy.

[0039] The vapor compression refrigeration unit includes a refrigeration condenser 2, a throttle valve 3, a refrigeration evaporator 4, and a compressor 5; the power inlet of the compressor 5 is connected to the power outlet of the renewable energy power generation module 12, and the renewable energy is transported to the compressor 5 to supply power to the compressor 5; the outlet of the compressor 5 is connected to the high-temperature side inlet of the refrigeration condenser 2, and the high-temperature side outlet of the refrigeration condenser 2 is connected to the low-temperature side inlet of the refrigeration evaporator 4 through the throttle valve 3; the working fluid is compressed to a high-pressure state by the compressor 5, and releases heat through the refrigeration condenser 2. The working fluid enters the throttle valve 3 for throttling and pressure reduction, and then enters the refrigeration evaporator 4 to absorb heat. The heat after heat exchange in the refrigeration condenser 2 is released into the environment through the cooling water circuit and the cooling tower 1.

[0040] The circulating working fluid of the vapor compression refrigeration unit adopts an organic working fluid or a natural working fluid, the organic working fluid is R1234yf or R1234ze(E), and the natural working fluid is ammonia or carbon dioxide.

[0041] The phase change cold storage device 6 is a cold storage tank for storing cold storage medium. The phase change cold storage device 6 is connected to the refrigeration evaporator 4 through a refrigerant circuit, and is used to absorb the cold energy provided by the refrigeration evaporator 4; the phase change cold storage device 6 is connected to the heat engine condenser 7 through a refrigerant circuit, and is used to provide cold energy to the heat engine condenser 7.

[0042] The phase change cold storage device 6 adopts a coil-type phase change cold storage tank or a packaged ice-type phase change cold storage tank; the cold storage medium adopts a phase change cold storage medium, and the phase change cold storage medium is selected according to the required phase change temperature. When the required phase change temperature is zero degrees Celsius, it is specifically ice water; when the required phase change temperature is lower than zero degrees Celsius (-20-0°C), eutectic ice is used for cold storage, specifically sodium chloride eutectic ice or calcium chloride eutectic ice; when the required phase change temperature is higher than zero degrees Celsius (5-13°C above zero), gas hydrate is used for cold storage, specifically methane hydrate or carbon dioxide hydrate; the coolant adopts ethylene glycol or carbon dioxide; the refrigerant adopts chilled water or ethylene glycol.

[0043] The power circulation unit includes a heat engine condenser 7, a working fluid pump 8, a heat engine evaporator 9, and a turbine expander 10; the low-temperature side outlet of the heat engine evaporator 9 is connected to the inlet of the turbine expander 10, the outlet of the turbine expander 10 is connected to the high-temperature side inlet of the heat engine condenser 7, the high-temperature side outlet of the heat engine condenser 7 is connected to the inlet of the working fluid pump 8, the outlet of the working fluid pump 8 is connected to the low-temperature side inlet of the heat engine evaporator 9, the power output shaft of the turbine expander 10 is connected to the power input shaft of the generator, and the power outlet of the generator is connected to the power inlet of the power grid 13; the low-temperature waste heat outlet of the low-temperature heat source module 11 is connected to the high-temperature side outlet of the heat engine evaporator 9 The warm side inlet is connected, and the high temperature side outlet of the heat engine evaporator 9 is connected to the low temperature waste heat inlet of the low temperature heat source module 11; the working fluid cooled by the heat engine condenser 7 is pressurized by the working fluid pump 8 and then heat-exchanged with the heat energy of the low temperature heat source in the low temperature heat source module 11 absorbed in the heat engine evaporator 9 to increase the temperature, reaching a high temperature and high pressure state, and then enters the turbine expander 10 to expand and perform work, driving the generator to rotate and generate electricity, and transmit the generated electricity to the power grid 13; according to different forms of low temperature heat sources, the low temperature heat source flowing through the heat engine evaporator 9 is absorbed by the working fluid and cooled, and then discharged into the environment or returned to the low temperature heat source module 11 to be reheated.

[0044] The circulating working fluid of the power cycle system is an organic working fluid, specifically R1234yf or R1234ze(E).

[0045] The low-temperature heat source in the low-temperature heat source module 11 can be solar energy (photothermal energy), geothermal energy, industrial waste heat, regional heating network or data center waste heat.

[0046] Example 2

[0047] like Figure 2 As shown, in addition to the system structure of Example 1, this embodiment also includes a power circulation unit. The low-temperature side inlet of the preheater 14 is connected to the outlet of the working fluid pump 8, and the low-temperature side outlet of the preheater 14 is connected to the low-temperature side inlet of the heat engine evaporator 9. The preheater 14 uses the higher temperature air during the day to preheat the working fluid, which can improve the thermal efficiency of the power cycle and reduce the configuration of the heat source (such as solar heat) and the corresponding investment.

[0048] Example 3

[0049] like Figure 3 As shown, in addition to the system structure of Example 1, this embodiment also includes an intercooler 15, the high-temperature side inlet of the intercooler 15 is connected to the outlet of the high-pressure cylinder of the turbine expander 10, and the high-temperature side outlet of the intercooler 15 is connected to the inlet of the low-pressure cylinder of the turbine expander 10; the intercooler 15 is used to lower the working medium temperature at the outlet of the turbine expander 10, reduce the demand for cold storage, and improve the round-trip efficiency of the entire energy storage system.

[0050] Example 4

[0051] like Figure 3 As shown, in addition to the system structure of Example 1, this embodiment also includes a power cycle system. The low-temperature side inlet of the regenerator 16 is connected to the outlet of the working fluid pump 8, and the low-temperature side outlet of the regenerator 16 is connected to the low-temperature side inlet of the heat engine evaporator 9, so that the working fluid is further preheated by the regenerator 16; the high-temperature side inlet of the regenerator 16 is connected to the outlet of the turbine expander 10, and the high-temperature side outlet of the regenerator 16 is connected to the high-temperature side inlet of the heat engine condenser 7, so that the high-temperature working fluid at the outlet of the turbine expander 10 is precooled.

[0052] The multi-mode operation method of the Carnot battery system based on phase change cold storage energy storage includes:

[0053] In charging mode, the vapor compression refrigeration unit operates at night, compressing the working fluid to a high-pressure state through the compressor 5. The working fluid then releases heat through the refrigeration condenser 2. The throttled low-temperature working fluid absorbs heat in the refrigeration evaporator 4 and transfers the cold energy to the phase-change cold storage device 6 through the refrigerant loop. The liquid cold storage medium in the phase-change cold storage device 6 solidifies into a solid state, consuming off-peak electricity for cooling. If the user has a cooling energy demand at this time, the cooling can be directly supplied through the refrigerant loop.

[0054] In the energy storage mode, the cold energy produced by the vapor compression refrigeration unit is stored in the phase change cold storage device 6, which can be stored for several hours or several days depending on the application scenario. At this time, if the user side has a cold energy demand, the cold energy can be taken from the phase change cold storage device 6 through the refrigerant circuit;

[0055] In the discharge mode, the power circulation unit operates, and the cold energy stored in the phase change cold storage device 6 is provided to the heat engine condenser 7 of the power circulation unit as a cold source through the refrigerant circuit. The working fluid cooled by the heat engine condenser 7 is pressurized by the working fluid pump 8, and absorbs the heat energy of the external low-temperature heat source in the heat engine evaporator 9, and is converted into a high-temperature and high-pressure state, and then enters the turbine expander 10 to perform expansion work, drive the generator to generate electricity, and output electrical energy; at this time, if the user side has a cold energy demand, it can take cold from the phase change cold storage device 6 through the refrigerant circuit.

[0056] In the static mode, there is no cold storage as the cold source of the power circulation unit. Air or cooling water in the ambient state can be transported to the thermal engine condenser 7 of the power circulation unit as the cold source; at this time, the power circulation unit uses the environment and low-temperature waste heat as cold and heat sources to convert heat into work, output electrical energy, and realize the full utilization of the low-temperature heat source; at this time, if the user side has both electricity and refrigeration needs, the mechanical energy generated by the power circulation unit can be converted into electrical energy through the generator to supply the steam compression refrigeration unit for operation, thereby realizing the output of cold energy.

Claims

1. The Carnot battery system based on phase change cold storage energy storage is characterized by: The invention comprises a vapor compression refrigeration unit, a phase change cold storage device (6) and a power circulation unit; the vapor compression refrigeration unit generates cold energy by using off-peak electricity, and the vapor compression refrigeration unit is connected to the phase change cold storage device (6) via a refrigerant loop; the phase change cold storage device (6) is used to store the cold energy generated by the vapor compression refrigeration unit; the power circulation unit is connected to the phase change cold storage device (6) via a refrigerant loop, the heat energy inlet of the power circulation unit is connected to the low-temperature waste heat outlet of the low-temperature heat source module (11), and the power circulation unit is used to simultaneously use the cold energy stored in the phase change cold storage device (6) and the heat energy of the low-temperature heat source in the low-temperature heat source module (11) to generate electricity; The power inlet of the vapor compression refrigeration unit is connected to the power outlet of the renewable energy power generation module (12), and the power generated by the renewable energy power generation module (12) is transmitted to the vapor compression refrigeration unit to be converted into cold energy; The power output shaft of the power circulation unit is connected to the power input shaft of the generator, and the power outlet of the generator is connected to the power inlet of the power grid (13), so that the mechanical energy generated in the power circulation unit is converted into electrical energy through the generator and transmitted to the power grid (13) for transmission to the user side for use; or the power outlet of the generator is connected to the power inlet of the vapor compression refrigeration unit, so that the excess electrical energy generated by the power circulation unit is re-transmitted to the vapor compression refrigeration unit for conversion into cold energy.

2. The Carnot battery system based on phase change cold energy storage according to claim 1 is characterized in that: The vapor compression refrigeration unit comprises a refrigeration condenser (2), a throttle valve (3), a refrigeration evaporator (4), and a compressor (5); the power inlet of the compressor (5) is connected to the power outlet of the renewable energy power generation module (12), and the renewable energy is transported to the compressor (5) to supply power to the compressor (5); the outlet of the compressor (5) is connected to the high-temperature side inlet of the refrigeration condenser (2), the high-temperature side outlet of the refrigeration condenser (2) is connected to the low-temperature side inlet of the refrigeration evaporator (4) through the throttle valve (3), and the low-temperature side outlet of the refrigeration evaporator (4) is connected to the inlet of the compressor (5); the working medium is compressed to a high-pressure state by the compressor (5), and releases heat through the refrigeration condenser (2). The working medium enters the throttle valve (3), is throttled and depressurized, and then enters the refrigeration evaporator (4) to absorb heat. The heat after heat exchange in the refrigeration condenser (2) is released into the environment.

3. The Carnot battery system based on phase change cold energy storage according to claim 1 is characterized in that: The phase-change cold storage device (6) is connected to the refrigeration evaporator (4) via a refrigerant circuit and is used to absorb the cold energy provided by the refrigeration evaporator (4); the phase-change cold storage device (6) is connected to the heat engine condenser (7) via a refrigerant circuit and is used to provide cold energy to the heat engine condenser (7).

4. The Carnot battery system based on phase change cold energy storage according to claim 1, characterized in that: The power circulation unit comprises a heat engine condenser (7), a working fluid pump (8), a heat engine evaporator (9), and a turbine expander (10); the low-temperature side outlet of the heat engine evaporator (9) is connected to the inlet of the turbine expander (10), the outlet of the turbine expander (10) is connected to the high-temperature side inlet of the heat engine condenser (7), the high-temperature side outlet of the heat engine condenser (7) is connected to the inlet of the working fluid pump (8), and the outlet of the working fluid pump (8) is connected to the low-temperature side inlet of the heat engine evaporator (9); the power output shaft of the turbine expander (10) is connected to the power input shaft of the generator, and the power outlet of the generator is connected to the power grid (1 3); the low-temperature waste heat outlet of the low-temperature heat source module (11) is connected to the high-temperature side inlet of the heat engine evaporator (9), and the high-temperature side outlet of the heat engine evaporator (9) is connected to the low-temperature waste heat inlet of the low-temperature heat source module (11); the working fluid cooled by the heat engine condenser (7) is pressurized by the working fluid pump (8) and then heat-exchanged with the heat energy of the low-temperature heat source in the low-temperature heat source module (11) absorbed in the heat engine evaporator (9) to increase the temperature, reaching a high-temperature and high-pressure state, and then enters the turbine expander (10) to perform expansion work, drive the generator to rotate and generate electricity, and transmit the generated electricity to the power grid (13).

5. The Carnot battery system based on phase change cold energy storage according to claim 4 is characterized in that: The power circulation unit further comprises a preheater (14), the low-temperature side inlet of the preheater (14) being connected to the outlet of the working medium pump (8), and the low-temperature side outlet of the preheater (14) being connected to the low-temperature side inlet of the heat engine evaporator (9), and the preheater (14) utilizing the higher temperature air during the day to preheat the working medium.

6. The Carnot battery system based on phase change cold energy storage according to claim 4 is characterized in that: The power circulation unit further includes an intercooler (15), wherein a high-temperature side inlet of the intercooler (15) is connected to an outlet of a high-pressure cylinder of the turbine expander (10), and a high-temperature side outlet of the intercooler (15) is connected to an inlet of a low-pressure cylinder of the turbine expander (10), and the temperature of the working medium at the outlet of the turbine expander (10) is reduced by the intercooler (15).

7. The Carnot battery system based on phase change cold energy storage according to claim 4 is characterized in that: The power circulation unit further includes a regenerator (16), wherein the low-temperature side inlet of the regenerator (16) is connected to the outlet of the working medium pump (8), and the low-temperature side outlet of the regenerator (16) is connected to the low-temperature side inlet of the heat engine evaporator (9), and the working medium is further preheated by the regenerator (16); the high-temperature side inlet of the regenerator (16) is connected to the outlet of the turbine expander (10), and the high-temperature side outlet of the regenerator (16) is connected to the high-temperature side inlet of the heat engine condenser (7), and the high-temperature working medium at the outlet of the turbine expander (10) is precooled by the regenerator (16).

8. The Carnot battery system based on phase change cold energy storage according to any one of claims 1 to 7, characterized in that: The circulating working fluid of the vapor compression refrigeration unit adopts an organic working fluid or a natural working fluid, the organic working fluid is R1234yf or R1234ze(E), and the natural working fluid is ammonia or carbon dioxide; The phase change cold storage device (6) is a coil-type phase change cold storage tank or a packaged ice-type phase change cold storage tank for storing a cold storage medium; when the required phase change temperature is zero degrees Celsius, the cold storage medium is ice water; when the required phase change temperature is lower than zero degrees Celsius, the cold storage medium is eutectic ice; when the required phase change temperature is higher than zero degrees Celsius, the cold storage medium is gas hydrate; the coolant is ethylene glycol or carbon dioxide; and the refrigerant is chilled water or ethylene glycol. The circulating working fluid of the power circulation unit is an organic working fluid, specifically R1234yf or R1234ze(E).

9. The Carnot battery system based on phase change cold energy storage according to claim 8, characterized in that: The low-temperature heat source in the low-temperature heat source module (11) is solar energy, geothermal energy, industrial waste heat, regional heating network or data center waste heat.

10. A multi-mode operation method of a Carnot battery system based on phase change cold storage energy storage, characterized in that: include: In the charging mode, the vapor compression refrigeration unit operates at night, compresses the working medium to a high-pressure state through the compressor (5), releases heat through the refrigeration condenser (2), and the throttled low-temperature working medium absorbs heat in the refrigeration evaporator (4), and transmits the cold energy to the phase-change cold storage device (6) through the refrigerant loop. The liquid cold storage medium in the phase-change cold storage device (6) solidifies into a solid state, consuming off-peak electricity for refrigeration. At this time, if the user side has a cold energy demand, the cold energy can be directly supplied through the refrigerant loop; In the energy storage mode, the cold energy produced by the vapor compression refrigeration unit is stored in the phase change cold storage device (6); if the user side has a cold energy demand at this time, the cold energy can be taken from the phase change cold storage device (6) through the refrigerant circuit; In the discharge mode, the power circulation unit operates, and the cold energy stored in the phase change cold storage device (6) is provided to the heat engine condenser (7) of the power circulation unit as a cold source through the refrigerant circuit. The working fluid cooled by the heat engine condenser (7) is pressurized by the working fluid pump (8), absorbs the heat energy of the external low-temperature heat source in the heat engine evaporator (9), reaches a high-temperature and high-pressure state, and then enters the turbine expander (10) to perform expansion work, driving the generator to generate electricity and output electrical energy. At this time, if the user side has a cold energy demand, the cold energy can be taken from the phase change cold storage device (6) through the refrigerant circuit; In the static mode, there is no cold storage as the cold source of the power circulation unit, and air or cooling water in the ambient state can be used to transport to the heat engine condenser (7) of the power circulation unit as the cold source; at this time, the power circulation unit uses the environment and low-temperature waste heat as cold and heat sources to convert heat into work, output electrical energy, and realize full utilization of the low-temperature heat source; at this time, if the user side has both electricity and refrigeration needs, the mechanical energy generated by the power circulation unit can be converted into electrical energy through the generator to supply the steam compression refrigeration unit to operate, thereby realizing the output of cold energy.

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