A constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat

Abstract

This invention discloses a constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat, comprising a water tank, a synchronous generator, a constant current power supply, a rectifier, a slip-ring motor, a variable-frequency generator, an energy storage device, and an ORC system consisting of a cooling tower, a condenser, an expander, and an evaporator. The rectifier is connected to a controller, which controls the rectifier to achieve a specific DC current to drive the slip-ring motor to the required speed. The mechanical energy output from the expander is received by the energy storage device and converted into elastic potential energy for storage. The mechanical energy stored in the energy storage device is received by the synchronous generator through another path to generate a variable-frequency, variable-voltage three-phase current. Different functions are achieved by controlling the opening and closing of valves, the start and stop of the water pump, and the states of the rectifier and transformer. Power generation and grid connection are performed during peak electricity demand, and mechanical energy storage is performed during off-peak electricity demand; when fluctuating waste heat is insufficient, the stored mechanical energy is used for power generation and grid connection.

Description

Technical Field

[0001] This invention belongs to the field of waste heat power generation and thermal energy storage peak shaving technology, and relates to a constant frequency power generation and mechanical energy storage peak shaving system based on fluctuating waste heat. Background Technology

[0002] The production processes in numerous industrial sectors, such as steel, chemicals, non-ferrous metallurgy, and cement, generate substantial amounts of fluctuating waste heat. Directly releasing this waste heat into the air not only impacts the environment but also results in heat waste. Organic Rankine Cycle (ORC) waste heat power generation systems can achieve low-temperature waste heat recovery and power generation, with minimum waste heat resource temperatures as low as 60°C. However, large amounts of fluctuating waste heat are characterized by low quality, dispersion, and significant volatility. Under these conditions, ORC power generation systems employing quasi-synchronous grid connection lack the ability to dynamically adjust expander speed, leading to a mismatch between expander speed and load, which in turn causes a decline in the system's variable operating condition performance and reduced power generation efficiency. Therefore, to achieve dynamic control of expander speed under grid connection and efficient operation under fluctuating heat sources, it is urgent to explore or introduce new speed control modes and waste heat flow control methods.

[0003] Variable speed constant frequency (ORC) technology refers to a generator whose rotational speed can vary with the expander speed during power generation. A constant frequency is achieved through other control methods, such as adjusting the magnitude, frequency, and phase of the generator rotor current. This technology is widely used in wind power generation. Frequency regulation is often achieved using a combination of rectifiers and inverters; however, current mainstream inverters are designed for high-power circuits, resulting in higher costs. Therefore, a dedicated variable frequency energy storage device suitable for small-scale ORC systems needs to be designed. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides a constant frequency power generation and mechanical energy storage peak shaving system based on fluctuating waste heat. This system can adapt to fluctuating low-quality heat sources, operate efficiently and stably, and achieve the function of energy storage peak shaving.

[0005] To address the aforementioned technical problems, this invention proposes a constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat, comprising a water tank, a synchronous generator, a constant current power supply, a rectifier, a slip-ring motor, a variable-frequency generator, an energy storage device, and an ORC system consisting of a cooling tower, a condenser, an expander, and an evaporator. The rectifier is connected to a controller. The cooling tower and the low-temperature side of the condenser are connected in a loop via a pipeline. A butterfly valve is installed on the pipeline between the low-temperature outlet of the condenser and the inlet of the cooling tower. A first water pump and a first butterfly valve are sequentially connected from the outlet of the cooling tower to the low-temperature inlet of the condenser. A second water pump and a second butterfly valve are sequentially installed on pipe I, which connects the evaporator's low-temperature side inlet to the side outlet. A water storage tank is connected in series on pipe II, with one end connected to the evaporator's high-temperature side inlet and the other end connected to the waste heat inlet pipe. A butterfly valve (19-23) is installed at each of the two ends of the water storage tank. A third water pump and a third butterfly valve are sequentially installed on pipe III, which connects the evaporator's high-temperature side outlet to the waste heat return pipe. The evaporator's low-temperature side outlet is connected to the expander's inlet via a pipe equipped with a butterfly valve. The condensate generated on the condenser's high-temperature side passes through pipe I and the evaporator's inlet in sequence. The low-temperature side of the expander is heated to a steam state before entering the expander, and the exhaust steam discharged from the expander outlet is condensed into a liquid state; the cooling tower provides cooling capacity to the condenser; a fourth water pump and a fourth butterfly valve are sequentially installed on pipeline IV connecting the outlet of the expander to the high-temperature side inlet of the condenser; the drive shaft A of the expander is connected to one end of the first automatic clutch, the other end of the first automatic clutch is connected to one end of the drive shaft B, the other end of the drive shaft B is connected to the drive shaft C through the first universal joint, and the two ends of the drive shaft C are respectively connected to one end of the second automatic clutch and the third automatic clutch; the other end of the third automatic clutch... The second automatic clutch is connected to the drive shaft E via a third universal joint, and the other end of the drive shaft E is connected to the energy storage device. The other end of the second automatic clutch is connected to one end of the drive shaft D via a second universal joint, and the other end of the drive shaft D is connected to the synchronous generator. The constant current power supply is connected to the excitation winding of the synchronous generator, causing the rotor of the synchronous generator to rotate and generate three-phase AC power. The rectifier is connected to the slip differential motor, and the slip differential motor is coaxially connected to the frequency converter. The frequency converter generates three-phase AC power at a frequency of 50Hz, which is connected to the transformer. The transformer boosts the three-phase current to 380V and connects it to the power grid.

[0006] Furthermore, in the constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat described in this invention, wherein:

[0007] The controller is connected to the rectifier and is used to control the rectifier to achieve a specific amount of DC-DC conversion.

[0008] The rectifier converts the alternating current generated by the synchronous generator into a specific amount of direct current to drive the slip motor to reach the required speed.

[0009] The mechanical energy output from the expander is received by the energy storage device via the drive shafts A, B, C, and E, and converted into elastic potential energy for storage.

[0010] The mechanical energy stored in the energy storage device is received by the synchronous generator via the drive shafts E, C, and D, and generates a variable frequency and variable voltage three-phase current.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] The present invention proposes a constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat, which can output constant and usable electrical energy under fluctuating waste heat. Compared with traditional power generation systems, it can achieve variable-temperature operation and higher conversion efficiency because it does not require controlling the synchronous generator speed to stabilize. At the same time, it can store energy through elastic potential energy during off-peak hours and convert it into electrical energy during peak hours, thus realizing a greater degree of energy recovery and utilization. Attached Figure Description

[0013] Figure 1 This invention relates to a constant-frequency power generation and mechanical energy storage peak-shaving system based on fluctuating waste heat.

[0014] In the picture:

[0015] 1-Fourth butterfly valve; 2-Condenser; 3-Cooling tower; 4, 19, 21, 23-Butterfly valves

[0016] 5-First butterfly valve; 6-Energy storage device; 7-Third automatic clutch; 8-First automatic clutch

[0017] 9-Second automatic clutch 10-Synchronous generator 11-Constant current power supply 12-Rectifier

[0018] 13-Controller 14-Slip-ring motor 15-Variable frequency generator 16-Transformer

[0019] 17-Power Grid 18-Evaporator 20-Water Storage Tank 22-Third Butterfly Valve

[0020] 24-Expander 25-Second Butterfly Valve 26-Fourth Water Pump 27-Third Water Pump

[0021] 28-First water pump 29-Fourth water pump 30-Third universal joint 31-First universal joint

[0022] 32-Second Universal Joint Detailed Implementation

[0023] The design concept of a constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat proposed in this invention is as follows: Figure 1 As shown, the system mainly includes a condenser 2, a cooling tower 3, a water storage tank 20, an energy storage device 6, a transformer 16, a variable frequency generator 15, a constant current power supply 11, a slip-ring motor 14, a rectifier 12, a synchronous generator 10, an expander 24, an evaporator 18, a controller 13, a water storage tank 20, and three automatic clutches. The cooling tower 3, condenser 2, expander 24, and evaporator 18 constitute the ORC system. The controller 13 is connected to the rectifier 12 and controls the rectifier 12 to achieve a specific DC-DC conversion. The rectifier 12 converts the AC power generated by the synchronous generator 10 into a specific DC power to drive the slip-ring motor 14 to the required speed. In this invention, the power generation and energy storage requirements under different fluctuating waste heat are met by controlling the opening and closing of all butterfly valves, the state of the three automatic clutches (first automatic clutch 8, second automatic clutch 9, and third automatic clutch 7), and the speed of the slip-ring motor 14. The three-phase electricity of different frequencies generated by the synchronous generator 10 is converted into a specific amount of DC electricity by the rectifier 12. The DC electricity is then fed into the slip-ring motor 14 to generate a specific speed, which causes the coaxially connected variable frequency generator 15 to generate 50Hz three-phase electricity. This electricity is then converted into 380V grid-connected three-phase electricity by the transformer 16. This process is controlled by the controller 13, which is connected to the rectifier 12. This system can adapt to fluctuating low-quality heat sources, operates efficiently and stably, and achieves the function of energy storage and peak shaving.

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention.

[0025] like Figure 1As shown, this invention proposes a constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat. The cooling tower 3 and the low-temperature side of the condenser 2 are connected in a loop via a pipeline. A butterfly valve 4 is installed on the pipeline between the low-temperature side outlet of the condenser 2 and the inlet of the cooling tower 3. A first water pump 28 and a first butterfly valve 5 are sequentially connected from the outlet of the cooling tower 3 to the low-temperature side inlet of the condenser 2. A second water pump 29 and a second butterfly valve 25 are sequentially installed on pipeline I connecting the high-temperature side outlet of the condenser 2 to the low-temperature side inlet of the evaporator 18. A water storage tank 20 is connected in series on pipeline II, one end of which is connected to the high-temperature side inlet of the evaporator 18, and the other end of which is connected to the waste heat inlet pipe. A butterfly valve (i.e., butterfly valve 19 and butterfly valve 23) is installed at each of the two ports of the water storage tank 20. A third water pump 27 and a third butterfly valve 22 are sequentially installed on pipe III, which connects the high-temperature outlet of the evaporator 18 to the waste heat return water pipe. The low-temperature outlet of the evaporator 18 is connected to the inlet of the expander 24 via a pipe equipped with a butterfly valve 21. The condensate generated on the high-temperature side of the condenser 2 is heated to steam state through pipe I and the low-temperature side of the evaporator 18 before entering the expander 24. The exhaust steam discharged from the outlet of the expander 24 is condensed into liquid state. The cooling tower 3 provides cooling capacity to the condenser 2. A fourth water pump 26 and a fourth butterfly valve 1 are sequentially installed on pipe IV, which connects the outlet of the expander 24 to the high-temperature inlet of the condenser 2.

[0026] The expander 24 has its drive shaft A connected to one end of the first automatic clutch 8, the other end of the first automatic clutch 8 connected to one end of drive shaft B, the other end of drive shaft B connected to drive shaft C via a first universal joint 31, and both ends of drive shaft C connected to one end of the second automatic clutch 9 and the third automatic clutch 7 respectively; the other end of the third automatic clutch 7 connected to drive shaft E via a third universal joint 30, and the other end of drive shaft E connected to the energy storage device 6; the mechanical energy output by the expander 24 is received by the energy storage device 6 via drive shafts A, B, C, and E, and converted into elastic potential energy for storage. The mechanical energy stored in the energy storage device 6 is received by the synchronous generator 10 via drive shafts E, C, and D to generate a variable frequency and variable voltage three-phase current. The other end of the second automatic clutch 9 is connected to one end of drive shaft D via a second universal joint 32, and the other end of drive shaft D is connected to the synchronous generator 10. The constant current power supply 11 is connected to the excitation winding of the synchronous generator 10, causing the rotor of the synchronous generator 10 to rotate and generate three-phase AC power. The rectifier 12 is connected to the slip differential motor 14, and the slip differential motor 14 is coaxially connected to the variable frequency generator 15. The variable frequency generator 15 generates three-phase AC power at a frequency of 50Hz and connects it to the transformer 16. The transformer 16 boosts the three-phase current to 380V and connects it to the power grid 17.

[0027] In this invention, each automatic clutch is installed between two drive shafts, serving to transmit power and control the connection or disconnection between the drive shafts. When the automatic clutch is engaged, the rotation of one drive shaft transmits power to the other, causing that drive shaft to begin rotating. When the automatic clutch disengages, it stops the rotation of that drive shaft. In this invention, each universal joint enables power transmission between two mutually perpendicular drive shafts, ensuring their instantaneous angular velocities remain constant. It allows the included angle between connected parts to vary within a certain range, accommodating high-speed movement of the drive shafts. In this invention, the energy storage device 6 consists of a fixed housing and a torque spring connected to the transmission shaft E. When the transmission shaft E rotates, the torque spring is twisted, causing deformation of its cross-section, converting rotational kinetic energy into elastic potential energy. The stored elastic potential energy can be released by restoring the deformation, and the released elastic potential energy can then be converted into rotational kinetic energy.

[0028] In this invention, all butterfly valves, automatic clutches, and water pumps are also connected to the controller 13. By controlling the opening and closing of valves, the start and stop of water pumps, and the states of rectifier 14 and transformer 11, different functions are achieved. During peak electricity demand, power generation and grid connection are performed; during off-peak electricity demand, mechanical energy storage is implemented; and when there is insufficient residual heat during fluctuations, the stored mechanical energy is used for power generation and grid connection.

[0029] When using fluctuating waste heat for grid-connected power generation, all butterfly valves are in the open state; the first automatic clutch 8 and the second automatic clutch 9 are in the engaged state; and the third automatic clutch 7 is in the disengaged state. The grid-connected power generation process is as follows: Fluctuating waste heat passes through the ORC system: the fluctuating waste heat exchanges heat with the working fluid on the high-temperature side of the evaporator 18, causing the working fluid to become steam; the steam enters the expander 24, and outputs mechanical energy during expansion and pressure reduction; cooling water from the cooling tower 3 enters the low-temperature side of the condenser 2, and the exhaust steam generated by the expander 24 is condensed into liquid state on the high-temperature side of the condenser 2; the mechanical energy output from the expander 24 by the ORC system travels through drive shaft A to drive shaft B, and then through the first universal joint 31 from drive shaft B to drive shaft C, and then through the second universal joint 32 from drive shaft C to drive shaft D, where it is received by the synchronous generator 10 and generates a variable frequency and variable voltage three-phase current; the generated three-phase current is converted into DC power by the rectifier 12 to drive the slip differential motor 14, which in turn drives the variable frequency generator 15 to rotate and generate three-phase current; the three-phase current is then regulated by the transformer 16 and connected to the grid 17, achieving grid-connected power generation.

[0030] When using mechanical energy storage for power generation and grid connection, all butterfly valves are closed; the first automatic clutch 8 is disengaged; and the second automatic clutch 9 and the third automatic clutch 7 are engaged. The mechanical energy stored in the energy storage device 6 is released and transmitted from drive shaft E to drive shaft C via the third universal joint 30. Then, the mechanical energy is transmitted from drive shaft C to drive shaft D via the second universal joint 32 and received by the synchronous generator 10 to generate a variable frequency and voltage three-phase current. The generated three-phase current is converted into DC power by the rectifier 12 to drive the slip differential motor 14, which in turn drives the variable frequency generator 15 to rotate and generate three-phase current. The three-phase current is then regulated by the transformer 16 and connected to the power grid 17 to achieve power generation and grid connection.

[0031] During mechanical energy storage, all butterfly valves are in the open state; the first automatic clutch 8 and the third automatic clutch 7 are in the engaged state; and the second automatic clutch 9 is in the disengaged state. Fluctuating waste heat passes through the ORC system: the fluctuating waste heat exchanges heat with the working fluid on the high-temperature side of the evaporator 18, causing the working fluid to become steam; the steam enters the expander 24, and outputs mechanical energy during expansion and pressure reduction; cooling water from the cooling tower 3 enters the low-temperature side of the condenser 2, and the exhaust steam generated by the expander 24 is condensed to a liquid state on the high-temperature side of the condenser 2; the mechanical energy output from the expander 24 by the ORC system travels through drive shaft A to drive shaft B, and then through the third universal joint 30 from drive shaft B to drive shaft E. Afterward, the mechanical energy is received by the energy storage device and converted into elastic potential energy for storage.

[0032] Example:

[0033] During peak electricity consumption periods, peak power generation is achieved. When using fluctuating waste heat for grid-connected power generation, all butterfly valves are open; the first and second automatic clutches 8 and 9 are engaged; and the third automatic clutch 7 is disengaged. Fluctuating waste heat with a temperature of 60-110℃ exchanges heat with the working fluid (such as R600, R142b, or R245fa) through the evaporator 18, causing the working fluid to become steam and reducing the temperature of the fluctuating waste heat. The steam enters the expander 24, where it expands, reduces pressure, and cools down while simultaneously outputting mechanical work. Subsequently, the working fluid flows through the condenser 2 and exchanges heat with approximately 20℃ cooling water from the cooling tower 1, condensing the working fluid into a liquid state while simultaneously increasing the temperature of the condensate. The output mechanical work is received by the synchronous generator 10 via drive shafts A, B, C, and D. The rotor of the synchronous generator 10 is embedded with an excitation winding. During operation, a constant current power supply 11 is connected to generate a magnetic field, which rotates and cuts the magnetic field generated by the rotating magnetic field generated by the stator winding, generating a variable frequency and variable voltage three-phase current. The generated three-phase current is converted into direct current by rectifier 12. The slip-ring motor 14 can be connected to different amounts of direct current from rectifier 12 to change its speed. The coaxial inverter generator 15 can generate three-phase current of different frequencies at different speeds. The slip-ring motor 14 drives the coaxial inverter generator 15 to generate a 50Hz three-phase current. During this process, controller 13 needs to control the magnitude of the direct current generated by rectifier 12 to ensure that the speed of slip-ring motor 14 can meet the requirements of inverter generator 15 to generate a 50Hz three-phase current. The three-phase current is regulated to 380V by transformer 16 under the action of controller 13. Transformer 16 is then connected to grid 9 to achieve power generation and grid connection.

[0034] During periods of low electricity demand, residual heat is used for mechanical energy storage; all butterfly valves are in the open state; the first and third automatic clutches 8 and 7 are engaged; and the second automatic clutch 9 is disengaged. The mechanical energy output by the expander 24 is transmitted through drive shafts A and B to drive shaft E, where it is received by the energy storage device and converted into elastic potential energy for storage.

[0035] When electricity supply is tight and residual heat is insufficient, all butterfly valves are closed; the first automatic clutch 8 is disengaged; and the second and third automatic clutches 9 and 7 are engaged. The stored elastic potential energy can drive a synchronous generator to generate electricity and connect to the grid via drive shafts E and C to drive shaft D.

[0036] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit of the present invention, and these modifications are all within the protection scope of the present invention.

Claims

1. A constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat, comprising a water tank (20), a synchronous generator (10), a constant current power supply (11), a rectifier (12), a slip-ring motor (14), a variable-frequency generator (15), an energy storage device (6), and an ORC system composed of a cooling tower (3), a condenser (2), an expander (24), and an evaporator (18), wherein the rectifier (12) is connected to a controller (13); characterized in that, The cooling tower (3) and the low-temperature side of the condenser (2) are connected by a pipeline to form a loop; a butterfly valve (4) is provided on the pipeline between the low-temperature side outlet of the condenser (2) and the inlet of the cooling tower (3); a first water pump (28) and a first butterfly valve (5) are connected sequentially from the outlet of the cooling tower (3) to the low-temperature side inlet of the condenser (2); a second water pump (29) and a second butterfly valve (25) are connected sequentially on pipeline I from the high-temperature side outlet of the condenser (2) to the low-temperature side inlet of the evaporator (18); the water storage tank (20) is connected in series on pipeline II, one end of pipeline II is connected to the high-temperature side inlet of the evaporator (18), and the other end of pipeline II is connected to the waste heat inlet pipe; both ends of the water storage tank (20) are respectively equipped with There is a butterfly valve; a third water pump (27) and a third butterfly valve (22) are sequentially installed on the pipe III connecting the high-temperature side outlet of the evaporator (18) to the waste heat return water pipe; the low-temperature side outlet of the evaporator (18) is connected to the inlet of the expander (24) through a pipe, on which a butterfly valve is installed; the condensate generated on the high-temperature side of the condenser (2) is heated to steam state through pipe I and the low-temperature side of the evaporator (18) and enters the expander (24); the exhaust steam discharged from the outlet of the expander (24) is condensed to liquid state; the cooling tower (3) provides cooling capacity to the condenser (2); a fourth water pump (26) and a fourth butterfly valve (1) are sequentially installed on the pipe IV connecting the outlet of the expander (24) to the high-temperature side inlet of the condenser (2); The expansion machine (24) has its drive shaft A connected to one end of the first automatic clutch (8), the other end of the first automatic clutch (8) connected to one end of the drive shaft B, the other end of the drive shaft B connected to the drive shaft C via the first universal joint (31), the two ends of the drive shaft C connected to one end of the second automatic clutch (9) and the third automatic clutch (7) respectively; the other end of the third automatic clutch (7) connected to the drive shaft E via the third universal joint (30), the other end of the drive shaft E connected to the energy storage device (6); the other end of the second automatic clutch (9) connected to one end of the drive shaft D via the second universal joint (32), the other end of the drive shaft D connected to the synchronous generator (10); The constant current power supply (11) is connected to the excitation winding of the synchronous generator (10), so that the rotor of the synchronous generator (10) rotates to generate three-phase AC power; the rectifier (12) is connected to the slip differential motor (14), the slip differential motor (14) is coaxially connected to the variable frequency generator (15), the variable frequency generator (15) generates three-phase AC power at a frequency of 50Hz and connects to the transformer (16), the transformer (16) boosts the three-phase current to 380V and connects it to the power grid (17).

2. The constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat according to claim 1, characterized in that, The controller (13) is connected to the rectifier (12), and the controller (13) is used to control the rectifier (12) to achieve a specific amount of DC-DC conversion.

3. The constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat according to claim 2, characterized in that, The rectifier (12) converts the alternating current generated by the synchronous generator (10) into a specific amount of direct current to drive the slip motor (14) to reach the required speed.

4. The constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat according to claim 1, characterized in that, The mechanical energy output by the expander (24) is received by the energy storage device (6) via the drive shafts A, B, C and E, and is converted into elastic potential energy and stored.

5. The constant-frequency power generation and mechanical energy storage peak-shaving system under fluctuating waste heat according to claim 1, characterized in that, The mechanical energy stored in the energy storage device (6) is received by the synchronous generator (10) via the drive shafts E, C and D and generates a variable frequency and variable voltage three-phase current.

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