Compressed air energy storage system based on point absorption type wave energy converter

Abstract

The invention discloses a compressed air energy storage system based on a point absorption type wave energy converter. The compressed air energy storage system comprises the point absorption type wave energy converter, a power takeoff transmission mechanism, a compression-expansion unit, a heat exchange system and an air storage system. 1, the point absorption type wave energy converter comprises a cylindrical floater with adjustable immersion depth; 2, the power takeoff transmission mechanism comprises a rack-gear mechanism and a crank-link mechanism; 3, the compression-expansion unit comprises reciprocating piston type compressor units and expansion machines, the number of the compressor units is four, compressors in each group are arranged in a horizontal central symmetry mode according to the number of 1 + 2N, and the expansion ratios of the expansion machines in all stages are the same; 4, the heat exchanger is a surface seawater heat exchanger and is used for increasing the inlet gas temperature of the next stage of expansion machine to the surface seawater temperature; and 5, the air storage system comprises a high-pressure air storage chamber and a low-pressure circulating air storage chamber, the high-pressure air storage chamber is used for storing high-pressure compressed air, and a working inlet and a working outlet of the low-pressure circulating air storage chamber are connected with an outlet of the last-stage expansion machine and an inlet of the compressor respectively, so that air flows in the closed circulating system all the time. According to the invention, high robustness of energy conversion under different wave conditions is realized by regulating and controlling the draught depth of the floater and the number of compressors of the compressor unit, and a high-efficiency energy storage scheme is expected to provide stable and relatively cheap power supply for coastal and offshore users.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to a compressed air energy storage system based on a point absorption wave energy converter. Background Technology

[0002] Compressed air energy storage (CASS) is a low-cost, flexible, and highly reliable large-scale energy storage solution. It primarily uses electrically driven compressors for energy storage, thus requiring a power generation followed by compression for renewable energy storage systems. Systems using electric compressors involve multiple energy conversion and dissipation stages. Therefore, to improve the round-trip efficiency of electric CASS systems, a series of thermal management measures, such as adiabatic compression and isothermal compression, are often employed to reduce heat loss, but this increases system complexity. The marine environment is harsher than onshore, placing higher demands on system self-sufficiency and maintainability. Therefore, utilizing wave energy to directly drive compressors without a power generation stage for CASS holds promise for a simpler, more reliable CASS system with slightly lower efficiency than conventional CASS systems but a lower levelized cost of electricity (LCOE).

[0003] Point-absorption wave energy converters possess advantages such as high conversion efficiency, small unit size, flexible design, and low construction cost. However, waves are unstable and discontinuous, and the constantly changing nature of waves makes it difficult for wave energy conversion systems with fixed characteristic parameters to achieve high energy efficiency. Currently, there are two main methods: structural optimization and power take-off control. Therefore, by adjusting the float's draft and load according to changes in wave conditions, the robustness of the wave energy converter to different wave conditions can be improved. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a compressed air energy storage system based on a point-absorbing wave energy converter. This system directly drives compressed air energy storage using wave energy, aiming to filter out high-frequency wave fluctuations through the energy storage stage, simplify the energy storage system structure, optimize power quality, and simultaneously solve the problem of low robustness of wave energy power generation devices when facing changing wave conditions.

[0005] The technical solution provided by this invention is as follows: A compressed air energy storage system based on a point-absorption wave energy converter includes a point-absorption wave energy converter, a power take-off (PTO) transmission mechanism, a compressor-expander unit, a heat exchanger, and a gas storage system. The point-absorption wave energy converter includes a cylindrical float with adjustable draft; the PTO transmission mechanism includes a rack-and-pinion mechanism and a crank-connecting rod mechanism; the compressor-expander unit includes a reciprocating piston compressor unit and an expander, with four compressor units arranged horizontally and symmetrically in a 1+2N configuration, and each expander having the same expansion ratio; the heat exchanger is a surface seawater heat exchanger; the gas storage system includes a high-pressure gas storage chamber and a low-pressure circulating gas storage chamber. The high-pressure gas storage chamber stores high-pressure compressed air, and the inlet and outlet of the low-pressure circulating gas storage chamber are connected to the outlet of the last-stage expander and the inlet of the compressor, respectively, ensuring that the air always circulates within a closed-loop system.

[0006] Furthermore, the float of the point absorption wave energy converter has a hollow structure inside, with the lower half directly connected to seawater through an opening, and the upper half being a cylindrical airbag whose volume can be changed.

[0007] Furthermore, the power take-off transmission structure includes a rack-and-pinion mechanism and a crank-connecting rod mechanism. The rack is located on the central axis of the cylindrical float, and its lower end is connected to the upper bottom surface of the float. The toothed side of the rack meshes with the gear.

[0008] Furthermore, the float oscillates under the action of waves, causing the rack to oscillate as well, thereby causing the gear to reciprocate.

[0009] Furthermore, the crank-connecting rod mechanism is mounted on both sides of the gear via a gear shaft.

[0010] Furthermore, the shafts at both ends of the crank that are connected to the gear shaft and the connecting rod respectively are unidirectional rotating shafts.

[0011] Furthermore, the compressor unit adopts a reciprocating piston compressor, with each group consisting of 1+2N compressors. The crank-connecting rod mechanism on each side is connected to two horizontally opposed compressor units via a bracket.

[0012] Furthermore, the heat exchange system employs a surface seawater heat exchanger, which is connected to the outlet of the previous stage expander and the inlet of the next stage expander.

[0013] Furthermore, the gas storage system includes a high-pressure gas storage chamber and a low-pressure circulating gas storage chamber.

[0014] Furthermore, the high-pressure gas storage chamber is used to store high-pressure air and drive the expander to generate electricity. The low-pressure circulating gas storage chamber receives the working air medium during the system startup phase and is used for air medium circulation during the system operation phase.

[0015] Furthermore, the input air medium during the system startup phase needs to be dried first. Beneficial effects

[0016] This invention provides a compressed air energy storage system based on a point absorption wave energy converter, which has the following beneficial effects: (1) The present invention absorbs wave energy through a float of a point-absorbing wave energy converter, and connects to a reciprocating piston compressor through a rack-gear and crank-connecting rod mechanism to convert wave energy into reciprocating mechanical energy, compress air and store it in a high-pressure air storage chamber, thereby realizing the rational utilization and storage of wave energy.

[0017] (2) In this invention, the draft of the float and the number of compressors put into operation can be adjusted according to the actual wave conditions, thereby improving the efficiency and robustness of energy conversion.

[0018] (3) In this invention, by setting two sets of crank-connecting rod mechanisms on both sides of the gear, connecting each set of crank-connecting rod mechanisms to two sets of horizontally opposed compressor units, and using unidirectional bearings on the rotating shafts at both ends of the crank, the system can achieve uninterrupted compressed air energy storage, thereby improving energy storage efficiency and speed.

[0019] (4) In this invention, the number of compressors in each compressor group is variable 1+2N and arranged in a centrally symmetrical manner, so that the force is balanced under any number of working compressors, ensuring the stable operation of the device.

[0020] (5) In this invention, the surface seawater is used as a stable heat source to expand compressed air at room temperature, which solves the problem of difficulty in obtaining heat source under offshore conditions and simplifies the complexity of heat exchange system.

[0021] (6) In this invention, the input air during the system startup phase is dried and pretreated, and a closed-loop air storage system is used to optimize the working conditions of the expander and improve the system's operational stability. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a system schematic diagram of the present invention.

[0024] Figure 2 This is a schematic diagram of the wave energy converter-power take-off unit structure of the present invention.

[0025] Figure 3 This is a side view of the wave energy converter-power take-off unit structure of the present invention.

[0026] Figure 4 This is a schematic diagram of the float structure of the point absorption wave energy converter of the present invention.

[0027] Figure 5 This is a schematic diagram of the compressor unit support structure of the present invention.

[0028] Figure 6 This is a schematic diagram of the symmetrical central compressor support structure of the present invention.

[0029] Figure 7 This is a schematic diagram of the cross-shaped support structure of the present invention.

[0030] Figure 8 This is a schematic diagram of the rectangular base structure of the present invention.

Claims

1. A compressed air energy storage system based on a point-absorption wave energy converter, characterized in that: The system includes a point-absorption wave energy converter, a power take-off (PTO) transmission mechanism, a compressor-expander unit, a heat exchange system, and a gas storage system. The point-absorption wave energy converter includes a cylindrical float with adjustable draft. The PTO transmission mechanism includes a rack-and-pinion mechanism and a crank-connecting rod mechanism. The compressor-expander unit includes a reciprocating piston compressor unit and four compressor units, each arranged horizontally and symmetrically in a 1+2N configuration. Each stage of the expander has the same expansion ratio. The heat exchanger is a surface seawater heat exchanger. The gas storage system includes a high-pressure gas storage chamber and a low-pressure circulating gas storage chamber. The high-pressure gas storage chamber stores high-pressure compressed air, and the working inlet and outlet of the low-pressure circulating gas storage chamber are connected to the outlet of the last-stage expander and the inlet of the compressor, respectively, ensuring that air always circulates within a closed-loop system.

2. The point absorption wave energy converter according to claim 1, characterized in that, The lower half of the float is a cavity that connects to the seawater through a connecting hole, while the upper half of the float is an air bladder that isolates the seawater. By increasing or decreasing the volume of the air bladder, the displacement volume of the float can be adjusted, thereby changing the draft of the float and thus obtaining a better unsteady wave-induced response.

3. The power take-off transmission mechanism according to claim 1, characterized in that, The float is connected to the crank-connecting rod mechanism via a rack and pinion mechanism. Two sets of the crank-connecting rod mechanism are symmetrically arranged on both sides of the gear shaft, corresponding to the wave energy conversion process during the rising and falling phases of the float, respectively.

4. The crank-connecting rod mechanism according to claim 3, characterized in that, The crankshafts at both ends of each crank-connecting rod mechanism are unidirectional shafts. When the float rises or falls, one set is under compressor load while the other set is unloaded.

5. The reciprocating piston compressor unit according to claim 1, characterized in that, Each compressor unit is connected to the crank-connecting rod mechanism via a bracket. One crank-connecting rod mechanism connects two horizontally opposed compressor units. The two compressor units compress air in the first and second half of the crank rotation, respectively, to achieve continuous and uninterrupted operation.

6. The compressor unit according to claim 5, characterized in that, Each compressor group consists of 1+2N compressors arranged symmetrically at the center, with 1 compressor located at the center of symmetry and 2N compressors located around it. This ensures that the compressors are evenly distributed under any number of working compressors, guaranteeing that the compressors working can complete the compression process synchronously.

7. The compressor unit according to claim 6, characterized in that, The number of compressors operating simultaneously can be adjusted according to changes in the wave conditions.

8. The heat exchange system according to claim 1, characterized in that, A surface seawater heat exchanger is used to increase the inlet temperature of the downstream expander by using readily available surface seawater as a stable heat source.

9. The low-pressure circulating gas storage chamber according to claim 1, characterized in that, It has a start-up inlet, a working inlet, and a working outlet. The start-up inlet is used to store pre-dried air during the system startup phase. The working inlet and working outlet are connected to the outlet of the last-stage expander and the inlet of the compressor, respectively. The circulating working medium during the working phase is the dried air stored during the startup phase.

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