Double-acting Stirling heat storage power generation system

Abstract

The invention relates to the technical field of Stirling, and provides a double-acting Stirling heat storage power generation system which comprises a plurality of Stirling heat pump / engine units, a high-temperature heat storage device and a driving device. The multiple Stirling heat pump / engine units are connected in series end to end through connecting pipelines to form a closed loop. A high-temperature heat exchanger, a heat regenerator and a low-temperature heat exchanger are sequentially arranged in each Stirling heat pump / engine unit, and the high-temperature heat storage device is connected with the high-temperature heat exchanger of each Stirling heat pump / engine unit and used for receiving and storing heat released by the high-temperature heat exchanger during electricity storage and releasing heat to the high-temperature heat exchanger during electricity generation; the driving device is in transmission connection with pistons in the Stirling heat pump / engine units, drives the pistons to reciprocate during electricity storage and outputs electric energy to the outside during electricity generation; the same system is utilized, the two functions of power storage and power generation under the same structure can be achieved by adjusting the operation strategy, and the number, occupied area and cost of main equipment are remarkably reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Stirling, in particular to a double-acting Stirling heat storage power generation system. BACKGROUND

[0002] With the accelerating transformation of global energy structure to renewable energy, the installed capacity of intermittent power sources such as wind power and photovoltaic continues to grow, and its inherent volatility and uncontrollability pose a serious challenge to the stable operation of the power grid. Therefore, the development of large-scale, long-cycle and low-cost energy storage technology has become the key to realizing high proportion of renewable energy consumption and safe scheduling of the power grid.

[0003] Among the many energy storage technology routes, the Carnot battery, as a kind of energy storage system based on heat-to-work conversion principle, has received widespread attention in recent years. The basic principle is: in the energy storage stage, the low-temperature heat source is pumped into the high-temperature heat storage medium for storage by using electric energy; in the power generation stage, the stored high-temperature heat energy is converted back into electric energy by a heat engine cycle. However, most of the Carnot battery systems currently still generally use resistance heating to achieve electric-thermal conversion in the energy storage link. This method is limited by the Joule heating effect, has a low theoretical efficiency, and there are significant heat losses in actual operation, resulting in low overall electric-thermal efficiency.

[0004] In addition, although some research has attempted to use Rankine cycle or Brayton cycle heat pumps as the core of the energy storage link, the compressors often face challenges in terms of operating efficiency and reliability under high-temperature conditions, which has become one of the bottlenecks restricting the development of Carnot batteries to higher temperatures and higher efficiencies. At the same time, such systems usually contain independent energy storage and power generation equipment, resulting in complex overall system structure, numerous equipment, large floor area, and increased initial investment and maintenance costs. SUMMARY

[0005] The present application provides a double-acting Stirling heat storage power generation system to solve the low electric-thermal conversion efficiency caused by the widespread use of resistance heating in Carnot battery systems in the prior art, as well as the limitations of traditional heat engine / heat pump system equipment in high-temperature environments and the complexity of the system structure.

[0006] The present application provides a double-acting Stirling heat storage power generation system that can switch between energy storage mode and power generation mode, comprising: A plurality of Stirling heat pump / engine units are connected in series through connecting pipes to form a closed loop; a high-temperature heat exchanger, a regenerator and a low-temperature heat exchanger are arranged in each Stirling heat pump / engine unit in sequence, and one piston is arranged in each Stirling heat pump / engine unit, the low-temperature side of the piston corresponding to the compression chamber of the Stirling heat pump / engine unit, and the high-temperature side corresponding to the expansion chamber; a high-temperature heat storage device connected to the high-temperature heat exchanger of each of the Stirling heat pump / engine units; in the electricity storage mode, the high-temperature heat storage device receives and stores the heat released by the high-temperature heat exchanger; in the electricity generation mode, the high-temperature heat storage device releases heat to the high-temperature heat exchanger; a driving device connected to the piston in each of the Stirling heat pump / engine units; In the electricity storage mode, the driving device drives the pistons of the Stirling heat pump / engine units to move, so that the working medium absorbs heat at the low-temperature heat exchanger and releases heat at the high-temperature heat exchanger to the high-temperature heat storage device for storage. In the electricity generation mode, the high-temperature heat storage device delivers the stored heat energy to the high-temperature heat exchanger, drives the working medium to expand and push the pistons of the Stirling heat pump / engine units and the driving device to move, thereby converting heat energy into mechanical energy and then into electrical energy output.

[0007] The double-acting Stirling heat storage and electricity generation system provided by the present application further comprises: a low-temperature heat storage device connected to the low-temperature heat exchanger of each of the Stirling heat pump / engine units, for providing heat for the low-temperature heat exchanger in the electricity storage mode and recovering the low-temperature waste heat released by the low-temperature heat exchanger in the electricity generation mode.

[0008] In the electricity storage mode, the low-temperature heat exchanger is in communication with the low-temperature heat storage device or an external low-grade heat source, for absorbing heat and transferring to the working medium.

[0009] In the electricity storage mode, the pistons of the Stirling heat pump / engine units are configured to move alternately and reciprocally with a preset phase difference, so that the high-temperature side is away from the driving device.

[0010] The double-acting Stirling heat storage and electricity generation system provided by the present application further comprises: a heat storage container; a heat storage medium filled in the heat storage container, the heat storage medium being a high-temperature phase change material, the high-temperature phase change material being at least one of molten salt, metal alloy, Al, NaCl or nitrate; or, the heat storage medium being a sensible heat storage material, the sensible heat storage material being at least one of ceramic refractory brick, high-temperature concrete and alumina packed bed; or, the heat storage medium being a chemical heat storage material, the chemical heat storage material being capable of absorbing and releasing heat through reversible chemical reaction.

[0011] According to the dual-action Stirling thermal energy storage power generation system provided by the present invention, the shell of the thermal energy storage container is made of ceramic material, and the inner wall of the thermal energy storage container is provided with a heat insulation layer.

[0012] According to the dual-action Stirling thermal energy storage power generation system provided by the present invention, the thermal energy storage device is connected in parallel with each of the high-temperature heat exchangers, and is used to connect to the high-temperature heat exchanger of each Stirling heat pump / engine unit respectively.

[0013] According to the dual-action Stirling thermal energy storage power generation system provided by the present invention, the number of Stirling heat pump / engine units is at least three.

[0014] According to the dual-acting Stirling thermal power generation system provided by the present invention, the driving device is one of a free piston linear motor, a rotary motor with crank-connecting rod mechanism, or a swashplate drive structure.

[0015] According to the dual-action Stirling thermal energy storage power generation system provided by the present invention, the power source of the drive device includes at least one of the following: grid power, renewable energy curtailment, standby generator output power, and fuel cell output power.

[0016] This invention provides a dual-action Stirling thermal energy storage and power generation system capable of switching between energy storage and power generation modes. It comprises multiple Stirling heat pump / engine units, a thermal storage device, and a drive unit. Utilizing the same set of dual-action Stirling structures, this invention can achieve both heat pump (energy storage) and generator (power generation) functions, avoiding the complexity of separate energy storage and power generation devices required in traditional solutions. This significantly reduces the number of main equipment, floor space, and initial investment costs. The system power can be flexibly configured by increasing or decreasing the number of units to adapt to different scales of energy storage needs. Each Stirling heat pump / engine unit in this invention is equipped with only one piston, significantly reducing the number of moving parts and lowering the risk of friction loss and seal leakage. It also reduces the number of vulnerable parts, lowering maintenance costs. Furthermore, it simplifies the internal structure of the units, reduces the overall system volume, achieves a compact design, and adapts to distributed layout requirements. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the dual-action Stirling thermal energy storage power generation system provided in an embodiment of the present invention.

[0019] Figure 2This is a schematic diagram of the structure of a free piston double-acting Stirling thermal power generation system in energy storage mode, provided in another embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the free piston double-acting Stirling thermal energy storage power generation system in power generation mode, provided in an embodiment of the present invention.

[0021] Figure label: 1. High-temperature heat exchanger; 2. Regenerator; 3. Low-temperature heat exchanger; 4. Piston; 5. Compression chamber; 6. Expansion chamber; 7. High-temperature heat storage device; 8. Low-temperature heat storage device; 9. Connecting pipes; 10. Inner stator; 11. Outer stator; 12. Back cavity. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] Currently, Carnot battery systems mostly use resistance heaters to convert electrical energy into heat energy in the energy storage stage. In actual operation, due to heat loss, the electro-thermal conversion efficiency is low, resulting in energy waste. In addition, resistance heating is a direct heat generation method and cannot utilize low-grade heat sources in the environment (such as air heat, industrial waste heat, etc.), thus failing to achieve cascaded energy utilization. Furthermore, due to high temperature limitations, the operating temperature of Carnot batteries will not be very high.

[0024] In the heat-to-work conversion (power generation) stage, although technologies such as steam turbines can be used, these systems are usually complex in structure, large in size, and independent of energy storage devices, resulting in low overall system integration.

[0025] Moreover, existing energy storage systems often have a single function, with energy storage such as resistance heating and power generation such as generators being independent of each other. This results in complex system structures, high costs, large footprints, and limitations imposed by specific geographical conditions.

[0026] The following is combined with Figures 1-3 This invention describes a dual-action Stirling thermal energy storage power generation system.

[0027] This invention provides a dual-action Stirling thermal energy storage power generation system capable of switching between energy storage and power generation modes. It uses an inert gas, such as helium, as the working fluid and includes: multiple Stirling heat pump / engine units, a high-temperature thermal energy storage device 7, and a drive device. The multiple Stirling heat pump / engine units are connected in series via connecting pipes 9 to form a closed-loop circuit. Each Stirling heat pump / engine unit is sequentially equipped with a high-temperature heat exchanger 1, a regenerator 2, and a low-temperature heat exchanger 3. Each Stirling heat pump / engine unit also contains a piston 4, with the low-temperature side of the piston 4 corresponding to the compression chamber 5 of the Stirling heat pump / engine unit and the high-temperature side corresponding to the expansion chamber 6.

[0028] The high-temperature heat storage device 7 is connected to the high-temperature heat exchanger 1 of each Stirling heat pump / engine unit, and is used to receive and store the heat released by the high-temperature heat exchanger 1 during power storage; and to release heat to the high-temperature heat exchanger 1 during power generation.

[0029] The drive unit is connected to the piston 4 in each Stirling heat pump / engine unit.

[0030] When the system of the present invention is in the energy storage mode, it operates as a heat pump. The driving device drives the pistons 4 of multiple Stirling heat pump / engine units to move, converting electrical energy into mechanical energy and then into heat energy. The heat energy is transferred to the high-temperature heat storage device 7 for storage through the high-temperature heat exchanger 1. When the system is in the power generation mode, it operates as an engine. The high-temperature heat storage device 7 delivers the stored heat energy to the high-temperature heat exchanger 1, driving the working fluid to expand and pushing the pistons 4 of multiple Stirling engine units to reciprocate, converting heat energy into mechanical energy, and driving the driving device to move to generate electricity, ultimately converting it into electrical energy.

[0031] As can be seen from the above scheme, the present invention utilizes the same double-acting Stirling thermal energy storage power generation system. By adjusting the operating strategy, it can realize both heat pump (energy storage) and power generation functions under the same structure, avoiding the complexity of setting up separate energy storage and power generation equipment in traditional schemes. This significantly reduces the number of main equipment, floor space, and initial investment costs. The system power can be flexibly configured by increasing or decreasing the number of units to adapt to different scales of energy storage needs. Each Stirling heat pump / engine unit of the present invention is equipped with only one piston 4, which significantly reduces the number of moving parts and reduces friction loss and the risk of sealing leakage. At the same time, it reduces the number of vulnerable parts and lowers maintenance costs. The piston 4 has a compression chamber 5 on the low-temperature side and an expansion chamber 6 on the high-temperature side, realizing that a single piston 4 has the functions of both a compressor and an expander. This reduces the number of moving parts, simplifies the internal structure of the unit, reduces the overall system volume, and achieves a compact design that adapts to distributed layout requirements.

[0032] Furthermore, the system's operating characteristics enable a drive-heat separation design, which spatially isolates the drive unit and piston 4 moving parts from the high-temperature parts of the system (high-temperature heat exchanger 1 and high-temperature heat storage device 7). This keeps temperature-sensitive components away from the high-temperature zone, mitigating the adverse effects of high temperatures on moving seals, lubrication, and materials. It also increases the upper limit of the system's operating temperature, allowing the system to operate stably in temperature environments of 500-600℃ or even higher, thus broadening its application scenarios.

[0033] It should be noted that double-acting means that each Stirling heat pump / engine unit has exactly one moving piston 4, one side of which acts as a compressor and the other side as an expander. Therefore, this structure significantly reduces the number of moving parts, lowers the risk of friction and leakage, and improves mechanical reliability. Furthermore, the theoretical efficiency of the Stirling cycle is the same as that of the Carnot cycle.

[0034] Preferably, the system contains at least three Stirling heat pump / engine units.

[0035] In this embodiment, during energy storage, the pistons 4 of adjacent Stirling heat pump / engine units are configured to reciprocate alternately according to a preset phase difference, so as to keep the high-temperature side away from the drive device.

[0036] During energy storage, the system operates as a heat pump. Driven by the drive unit, multiple pistons 4 alternately move up and down according to the phase difference set by the system, generating reciprocating linear motion. This drives the working fluid to continuously absorb heat from the low-temperature heat exchanger 3, and after being heated by the regenerator 2, it releases heat to the high-temperature heat storage device 7 through the high-temperature heat exchanger 1, ensuring continuous heat transfer to the high-temperature heat storage device 7 and achieving efficient heat storage. During power generation, the system operates as an engine. The high-temperature heat released by the high-temperature heat storage device 7 drives the working fluid to expand. At this time, multiple pistons 4 move alternately according to the phase difference, which drives the working fluid to continuously circulate between absorbing heat in the high-temperature heat exchanger 1 and releasing waste heat in the low-temperature heat exchanger 3, ensuring that mechanical energy is stably converted into electrical energy output.

[0037] Furthermore, it also includes a low-temperature heat storage device 8, which is connected to the low-temperature heat exchanger 3 of each Stirling heat pump / engine unit. When storing electricity, it provides the required low-temperature heat to the low-temperature heat exchanger 3; when generating electricity, it can recover the low-temperature waste heat released by the low-temperature heat exchanger 3. The heat stored in the low-temperature heat storage device 8 can be used to prepare domestic hot water or low-temperature steam. Domestic hot water (50℃-70℃) can be directly supplied to the daily hot water needs of factory employees and residential users, and low-temperature steam (100℃-120℃) can meet the low-temperature heat demand of light industrial production.

[0038] With this setup, if the low-temperature surplus of the low-temperature heat exchanger 3 of the Stirling heat pump / engine unit is directly discharged during power generation, it will cause energy loss. However, by setting up a low-temperature heat storage device 8 connected to the low-temperature heat exchanger 3, this part of the low-temperature waste heat can be recovered and stored, realizing combined heat and power. This not only avoids the waste of low-grade heat, but also enables the system energy utilization to form a cascade utilization of high-temperature heat energy (high-temperature heat storage device 7) → power generation → low-temperature waste heat (low-temperature heat storage device 8) → domestic / production heat, which significantly improves the energy utilization rate.

[0039] This invention enhances adaptability to various demand scenarios. For example, in industrial scenarios such as chemical plants and food factories, the system can simultaneously meet the dual needs of power grid peak-shaving power generation and domestic water and low-temperature steam for production in the plant area, without the need for a separate heating system. In distributed residential scenarios such as urban communities and remote villages, the system can achieve a mode of heat storage-power generation-waste heat supply through photovoltaic / wind power, simultaneously solving the electricity and hot water needs of residents, and is especially suitable for areas lacking centralized heating facilities.

[0040] In this embodiment, the low-temperature heat exchanger 3 is connected to the low-temperature heat storage device 8 or an external low-grade heat source. Alternatively, the external low-grade heat source can be stored in the low-temperature heat storage device 8. When storing electricity, the low-temperature heat storage device 8 can use low-grade heat sources such as industrial waste heat or domestic waste heat as the heat input of the heat pump. When generating electricity, the low-temperature heat storage device 8 can recover the heat released by the low-temperature heat exchanger.

[0041] With this configuration, the environmental heat sources (such as air and geothermal energy) or industrial waste heat (such as low-temperature wastewater and exhaust gas) absorbed by the low-temperature heat exchanger 3 are low-grade energy sources that are easily directly discharged and underutilized in traditional scenarios. By introducing them into the system and transferring them to the working fluid, the waste energy can be converted into energy input for the heat pump cycle, avoiding the waste of low-grade energy. Compared with traditional resistance heating, which consumes a lot of electrical energy, the low-temperature heat exchanger 3 can reduce the electric drive load in the energy storage mode after absorbing low-grade heat sources. At the same time, by absorbing industrial waste heat through the low-temperature heat exchanger 3, the direct emission of waste heat into the environment can be reduced, thus reducing pollution. Furthermore, the system is not constrained by geographical environment and can be widely applied to various scenarios such as distributed energy storage, industrial waste heat recovery, and grid peak shaving. For industrial waste heat, the system can be directly connected to the industrial waste heat pipeline in the factory area through the low-temperature heat exchanger 3, without the need for additional heat source configuration, realizing the dual functions of industrial waste heat recovery and energy storage. If there is a lack of industrial waste heat, the system can absorb environmental heat sources such as air and groundwater through the low-temperature heat exchanger 3, realizing heat pump heat storage and power generation without relying on specific industrial facilities, without the need to build additional heat source supply facilities (such as gas boilers and electric heating devices), reducing initial investment and subsequent maintenance costs.

[0042] In some embodiments, the drive device is an electric drive device, for example, it may be one of a free piston linear motor, a rotary motor with crank-connecting rod mechanism or a swashplate drive structure; if a rotary motor with crank-connecting rod mechanism is used, it is suitable for medium and large-sized stationary energy storage scenarios; if a swashplate drive structure is used, it is suitable for multi-cylinder compact layout to reduce system size.

[0043] Furthermore, the power source for the drive unit includes at least one of the following: grid power, renewable energy curtailment, backup generator output power, and fuel cell output power, thereby improving power supply reliability and flexibility.

[0044] like Figure 1 As shown, in energy storage mode, the system acts as a heat pump, converting electrical energy into high-temperature heat energy for storage. The specific process includes: Energy storage stage: The drive device, such as the electric drive device, is powered on and operates, driving the piston 4 of each Stirling heat pump / engine unit in the closed loop to reciprocate, converting electrical energy into mechanical energy, and generating acoustic work and pressure fluctuations in the compression chamber 5 and expansion chamber 6; the working fluid absorbs heat from the low-grade heat source in the low-temperature heat storage device 8 from the low-temperature heat exchanger 3, and then consumes acoustic work in the regenerator 2, generating a temperature gradient; the high-temperature working fluid, after being heated by the regenerator 2, flows into the high-temperature heat exchanger 1, releasing heat to the high-temperature heat storage device 7 for storage, completing the conversion of electrical energy to mechanical energy to thermal energy.

[0045] In this embodiment, the high-temperature heat storage device 7 includes a heat storage container and a heat storage medium filled in the heat storage container. The shell of the heat storage container can be made of ceramic material, and the inner wall of the heat storage container is provided with a heat insulation layer to reduce heat loss.

[0046] The heat storage medium can be flexibly selected according to the actual temperature and application. For example, the heat storage medium is a high-temperature phase change material, which is at least one of molten salt, metal alloy, Al, NaCl or nitrate, and can stably store high-temperature heat at 500℃-600℃; or, the heat storage medium is a sensible heat storage material, which is selected from at least one of ceramic refractory bricks, high-temperature concrete, alumina bed; or, the heat storage medium is a chemical heat storage material, which can absorb and release heat through reversible chemical reactions.

[0047] Power generation stage: When external power is needed, the high-temperature thermal energy stored in the high-temperature thermal storage device 7 drives the Stirling cycle in reverse. The specific process includes: The high-temperature heat stored in the high-temperature heat storage device 7 heats the working fluid through the high-temperature heat exchanger 1 of the Stirling heat pump / engine unit. The working fluid expands when heated, and after a certain temperature difference is formed between the regenerators 2, the heat energy is gradually converted into mechanical energy in the form of acoustic work. The acoustic work is transferred to the piston 4 through the high-temperature heat exchanger 1 and the expansion chamber 6, and drives the piston 4 to reciprocate to drive the power generation device to generate electricity. If the linear motor is driven to run in reverse, the mechanical energy is converted into electrical energy for external output, completing the conversion of heat energy-mechanical energy-electrical energy. At the same time, the remaining mechanical work is converted into acoustic work in the compression chamber 5 and enters the next Stirling heat pump / engine unit through the connecting pipe.

[0048] like Figure 1 , Figure 2 As shown, in some optional embodiments, the high-temperature heat storage device 7 is connected in parallel with each high-temperature heat exchanger 1, and is used to connect to the high-temperature heat exchanger 1 of each Stirling heat pump / engine unit respectively, which can avoid heat loss and transfer delay caused by series connection.

[0049] With this configuration, if a series connection is used, i.e. multiple high-temperature heat exchangers 1 are connected to the high-temperature heat storage device 7 in sequence, the heat from the previous stage high-temperature heat exchanger 1 will be easily lost due to heat dissipation during pipeline transmission, resulting in a decrease in the temperature of the heat transferred from the next stage high-temperature heat exchanger 1 to the high-temperature heat storage device 7, affecting the phase change efficiency of the heat storage medium such as phase change material. The parallel design allows the high-temperature heat exchanger 1 of each Stirling heat pump / engine unit to be directly and independently connected to the high-temperature heat storage device 7. The heat does not need to be transmitted through a series of pipelines, and the high-temperature heat can be directly injected into the high-temperature heat storage device 7, minimizing heat dissipation loss through pipelines and ensuring that the heat storage medium can quickly and efficiently absorb sufficient high-temperature heat and complete the phase change.

[0050] Reference Figure 2 In some optional embodiments, the electric drive device is a free-piston linear motor. The free-piston linear motor shares a moving part with the Stirling heat pump / engine unit. The free-piston linear motor includes an inner stator 10, an outer stator 11, and a piston 4. The outer stator 11 and the inner stator 10 are respectively surrounded on both sides of the piston 4. Coils are provided on the outer stator 11 and the inner stator 10. A permanent magnet is provided on the piston 4. When the coil is energized, it generates an alternating magnetic field, which drives the piston 4 to reciprocate.

[0051] In some alternative embodiments, the electric drive device includes a crank-connecting rod mechanism and a rotary motor. The output shaft of the rotary motor is connected to the input end of the crank-connecting rod mechanism, and the output end of the crank-connecting rod mechanism is connected to the piston 4. The rotary motor drives the crank-connecting rod mechanism to move, thereby causing the piston 4 to reciprocate.

[0052] In some alternative embodiments, the drive device is a swashplate drive structure or a rocking disc drive structure, and the power output end of the swashplate drive structure or the rocking disc drive structure is connected to the piston 4 to drive the piston 4 to reciprocate.

[0053] The dual-action Stirling energy and thermal energy storage system of the present invention will be described below with reference to three implementation schemes.

[0054] Example 1 In this embodiment, the system includes four Stirling heat pump / engine units connected end to end.

[0055] The Stirling heat pump / engine unit adopts a double-acting Stirling heat pump structure, including: compression chamber 5, piston 4, expansion chamber 6, high-temperature heat exchanger 1, regenerator 2, and low-temperature heat exchanger 3. The high-temperature heat exchanger 1 is connected to the expansion chamber 6, and the low-temperature heat exchanger 3 is connected to the compression chamber 5 of the next Stirling heat pump / engine unit. Thus, adjacent Stirling heat pumps / engines are connected end to end through connecting pipes 9 to form a closed loop.

[0056] Energy storage stage: External electrical energy is input to the drive device, converting electrical work into mechanical energy for the reciprocating motion of piston 4. This mechanical energy drives the gas in the cold and hot chambers to generate pressure fluctuations and acoustic energy. Subsequently, the gas stored in the low-temperature heat storage device 8 is absorbed in the low-temperature heat exchanger 3. Simultaneously, the acoustic energy is mainly consumed in the regenerator 2, generating a temperature gradient. This heat energy is then transferred to the high-temperature heat storage device 7 at the high-temperature heat exchanger 1 and stored in the heat storage medium. Under the drive of the electric drive device, the four pistons 4 and the gas alternately circulate. The four pistons 4 move up and down alternately according to the phase difference set by the system, generating a reciprocating linear motion.

[0057] Power generation stage: The high-temperature heat stored in the high-temperature thermal storage device 7 re-enters the system, converting thermal energy into mechanical energy of the reciprocating motion of piston 4, and driving the generator to generate electricity.

[0058] Example 2 This embodiment relates to the energy storage process of a free-piston type double-acting Stirling thermal energy storage power generation system, which includes four Stirling heat pump / engine units connected end to end. Each Stirling heat pump / engine unit shares a piston 4 with a linear motor. The linear motor includes a back cavity 12, an outer stator 11, and an inner stator 10. When the system is running, the input electrical energy generates an alternating magnetic field through the coils of the inner and outer stators 11. The permanent magnet on the piston 4 is driven by electromagnetic force under the action of the magnetic field and moves back and forth in a straight line. Through the connecting rod, it drives the piston 4 of the Stirling heat pump / engine unit to move, which is converted into the acoustic power of the working fluid.

[0059] The Stirling heat pump / engine unit adopts a double-acting Stirling heat pump structure, including a low-temperature heat exchanger 3, a piston 4, a regenerator 2, a high-temperature heat exchanger 1, a compression chamber 5, and an expansion chamber 6. The heat is transferred sequentially through the piston 4, the high-temperature heat exchanger 1, the regenerator 2, and the low-temperature heat exchanger 3, and a temperature gradient is generated in the regenerator 2. Finally, the heat is transferred to the high-temperature heat storage device 7 at the high-temperature heat exchanger 1. The connecting pipe 9 connects the expansion chamber 6 of the previous stage heat pump unit with the expansion chamber 6 of the next stage, forming a loop. The heat input required for the system operation comes from the low-temperature heat storage device 8.

[0060] When the system operates as a heat pump (energy storage stage), by controlling the direction of the input current, the piston 4 of the previous stage Stirling heat pump / engine unit is adjusted to lag behind the piston 4 of the next stage Stirling heat pump / engine unit by 90°, which enables the high-temperature side of the heat pump to be moved away from the linear motor end.

[0061] Example 3 This embodiment relates to the power generation process of a free-piston double-acting Stirling thermal energy storage power generation system, and the system structure is the same as that in Embodiment 2 above.

[0062] Power generation stage: High-temperature heat exchanger 1 utilizes the high-temperature heat stored in high-temperature heat storage device 7. Together with low-temperature heat exchanger 3, a temperature gradient is formed in regenerator 2. When the temperature difference reaches a certain level, the thermal energy is converted into mechanical work that drives piston 4 to reciprocate. This mechanical work, through piston 4 overcoming electromagnetic resistance, enables electrical energy output. At this point, the phase of piston 4 in the previous stage Stirling heat pump / engine unit leads the phase of piston 4 in the next stage Stirling heat pump / engine unit by 90°. Simultaneously, low-temperature heat exchanger 3 releases heat to low-temperature heat storage device 8, storing the waste heat for use in providing domestic hot water or low-temperature steam, thus achieving combined heat and power (CHP).

[0063] The dual-acting Stirling thermal energy storage and power generation system provided by this invention couples a dual-acting Stirling ultra-high temperature heat pump / generator with a Carnot battery system to replace the original electric heating method of the Carnot battery system. This improves the electro-thermal conversion efficiency, achieves efficient thermal energy storage, effectively utilizes low-grade waste heat, and expands the functions of the heat pump. At the same time, the dual-acting Stirling heat pump can keep the hot end away from the driving equipment, eliminating the high-temperature limitation of the compressor. In addition, the dual-acting Stirling heat pump can also serve as a power generation device, generating electrical energy when electricity is needed. It realizes the dual functions of heat pump and power generation in the same structure, reducing the complexity of the system.

[0064] During energy storage, the piston 4 of the Stirling heat pump moves under the drive of external electrical energy, converting electrical energy into mechanical energy. The working fluid absorbs heat from the low-temperature heat storage device 8 in the low-temperature heat exchanger 3, and then heats up in the high-temperature heat exchanger 1 through pumping, releasing high-temperature heat. The released heat is stored in the high-temperature heat storage device 7. When electrical energy is needed, the system uses the high-temperature heat stored in the high-temperature heat storage device 7 to heat the high-temperature heat exchanger 1. When the temperature difference in the regenerator 2 reaches a certain level, the piston 4 begins to move, converting thermal energy into mechanical energy, driving the motor to generate electricity. At the same time, the low-temperature heat exchanger 3 releases low-temperature waste heat into the low-temperature heat storage device 8, which can be used for domestic hot water or low-temperature steam. The heat pump temperature range in this system can reach over 200℃, and the heating temperature can reach 500-600℃. The system can utilize surplus renewable energy or electricity generated during off-peak hours to drive a Stirling heat pump, converting electrical energy into heat energy and storing it in a thermal storage system, thus playing a role in peak shaving and valley filling. When generating electricity, the system can achieve combined heat and power, further improving energy utilization efficiency.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual-action Stirling thermal energy storage power generation system, characterized in that, It can switch between energy storage mode and power generation mode, including: Multiple Stirling heat pump / engine units are connected in series to form a closed loop through connecting pipes (9); each Stirling heat pump / engine unit is provided with a high-temperature heat exchanger (1), a regenerator (2) and a low-temperature heat exchanger (3) in sequence, and each Stirling heat pump / engine unit is provided with a piston (4), the low-temperature side of the piston (4) corresponds to the compression chamber (5) of the double-acting Stirling heat pump / engine unit, and the high-temperature side corresponds to the expansion chamber (6). A high-temperature heat storage device (7) is connected to the high-temperature heat exchanger (1) of each Stirling heat pump / engine unit. When storing electricity, the high-temperature heat storage device (7) receives and stores the heat released by the high-temperature heat exchanger (1); when generating electricity, the high-temperature heat storage device (7) releases heat to the high-temperature heat exchanger (1). A drive unit, which is connected in drive to the piston (4) in each of the Stirling heat pump / engine units; In the energy storage mode, the driving device drives the pistons (4) of multiple Stirling heat pump / engine units to move, so that the working fluid absorbs heat at the low temperature heat exchanger (3) and releases heat at the high temperature heat exchanger (1) to the high temperature heat storage device (7) for storage. In the power generation mode, the high-temperature thermal storage device (7) delivers the stored thermal energy to the high-temperature heat exchanger (1), drives the working fluid to expand and pushes the pistons (4) of the multiple Stirling heat pump / engine units and the driving device to move, converting thermal energy into mechanical energy and then into electrical energy output.

2. The dual-action Stirling thermal energy storage power generation system according to claim 1, characterized in that, Also includes: The low-temperature heat storage device (8) is connected to the low-temperature heat exchanger (3) of each Stirling heat pump / engine unit, and is used to provide heat to the low-temperature heat exchanger (3) in the power storage mode and to recover the low-temperature waste heat released by the low-temperature heat exchanger (3) in the power generation mode.

3. The dual-action Stirling thermal energy storage power generation system according to claim 2, characterized in that, In the energy storage mode, the low-temperature heat exchanger (3) is connected to the low-temperature heat storage device (8) or an external low-grade heat source to absorb heat and transfer it to the working fluid.

4. The dual-action Stirling thermal energy storage power generation system according to claim 2, characterized in that, In the energy storage mode, the pistons (4) of adjacent Stirling heat pump / engine units are configured to reciprocate alternately according to a preset phase difference, so as to keep the high-temperature pump heat side away from the drive device.

5. The dual-action Stirling thermal energy storage power generation system according to claim 3 or 4, characterized in that, The high-temperature thermal storage device (7) includes: Thermal storage containers; The heat storage medium filled in the heat storage container is a high-temperature phase change material, which is at least one of molten salt, metal alloy, Al, NaCl, or nitrate; or, the heat storage medium is a sensible heat storage material, which is selected from at least one of ceramic refractory bricks, high-temperature concrete, and alumina bed; or, the heat storage medium is a chemical heat storage material, which can absorb and release heat through a reversible chemical reaction.

6. The dual-action Stirling thermal energy storage power generation system according to claim 5, characterized in that, The shell of the heat storage container is made of ceramic material, and the inner wall of the heat storage container is provided with a heat insulation layer.

7. The dual-action Stirling thermal energy storage power generation system according to claim 1, characterized in that, The high-temperature heat storage device (7) is connected in parallel with each of the high-temperature heat exchangers (1) and is used to connect to the high-temperature heat exchanger (1) of each Stirling heat pump / engine unit respectively.

8. The dual-action Stirling thermal energy storage power generation system according to any one of claims 1-7, characterized in that, The number of Stirling heat pump / engine units is at least three.

9. The dual-action Stirling thermal energy storage power generation system according to any one of claims 1-7, characterized in that, The drive device is one of the following: a free piston linear motor, a rotary motor with a crank-connecting rod mechanism, or a swashplate drive structure.

10. The dual-action Stirling thermal energy storage power generation system according to any one of claims 1-7, characterized in that, The power source of the drive device includes at least one of the following: grid power, renewable energy curtailment, backup generator output power, and fuel cell output power.

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