Wind power generation and compressed air energy storage combined device and control method

Abstract

The invention provides a wind power generation and compressed air energy storage combined device and a control method, the wind power generation and compressed air energy storage combined device comprises a first clutch arranged on a fan shaft, an air compressor, an air storage tank and an expansion machine, and the first clutch is connected with the air compressor through a transmission mechanism to drive the air compressor to rotate; an output port of the air compressor is connected with an inlet of the air storage tank, an outlet of the air storage tank is connected with the expansion machine, the expansion machine is connected with the generator, and the generator is electrically connected with the power transmission and transformation device. By means of the scheme that the impeller directly drives the air compressor in idle time and the compressed air is used for generating electricity, wind power exceeding a threshold value can be fully utilized, and wind energy of the wind power predicted in idle time can be converted into compressed air energy to be stored; and the stored compressed air can be used for compensating the difference value between the wind power prediction and the actual production, so that the benefit of a wind field is improved, and the power grid peak valley control capability is improved.

Description

Technical Field

[0001] The present invention relates to the field of wind power generation, and in particular to a combined device of wind power generation and compressed air energy storage and a control method. Background Art

[0002] As the global demand for clean energy grows, wind power generation has been widely used as an important renewable energy generation method. However, in the process of wind power generation, affected by factors such as the environment, wind speed, and wind direction, the output power of the power generation fluctuates and changes, and has the characteristics of intermittence and volatility. When it is incorporated into the power system, it may cause problems such as grid frequency deviation, voltage fluctuation, and flicker, which brings great challenges to the stable operation of the power system.

[0003] On the other hand, compressed air energy storage technology has the advantages of large energy storage capacity, long energy storage cycle, and relatively low cost, which can smooth the imbalance between energy supply and demand to a certain extent. Therefore, combining wind power generation with compressed air energy storage technology is of great significance for making full use of wind energy resources and improving the stability of the power system. However, the existing new energy power stations and the configured energy storage power stations are basically arranged and constructed separately on the same site. Some combined devices basically have problems such as complex structure, low energy conversion efficiency, and low space utilization efficiency. Especially for wind power generation projects built in mountainous areas and at sea, site selection and site construction are difficult and the cost investment is large. Chinese patent document publication number CN202690327U records a compressed air energy storage wind turbine, and proposes a scheme to combine a wind turbine with compressed air, in which the compressed air is compressed and used as the wind source for the impeller when needed. The energy conversion efficiency of this scheme is low. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a combined device of wind power generation and compressed air energy storage, which can realize multiple working modes, make full use of wind energy, and dynamically adjust the working mode according to the needs of the power grid.

[0005] Another technical problem to be solved by the present invention is to provide a control method for a combined device of wind power generation and compressed air energy storage, which can dynamically adjust the working mode of the device according to the needs of the power grid to fully utilize wind energy and increase the overall power generation.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a combined device of wind power generation and compressed air energy storage, comprising a first clutch arranged on a fan shaft, an air compressor, an air storage tank and an expander, the first clutch being connected to the air compressor through a transmission mechanism to drive the air compressor to rotate; The output port of the air compressor is connected to the inlet port of the air storage tank, the outlet port of the air storage tank is connected to the expander, the expander is connected to the generator, and the generator is electrically connected to the power transmission and transformation device.

[0007] In a preferred embodiment, there are at least two air storage tanks, and the air compressor is connected to each air storage tank via a valve group; Under normal working conditions, the air compressor's inlet check valve is connected to the atmosphere, and the air compressor's exhaust check valve is connected to one of the air storage tanks; Under the boost condition, one air storage tank is connected to the intake check valve of the air compressor, and the other air storage tank is connected to the exhaust check valve of the air compressor.

[0008] In a preferred embodiment, the air storage tank is located inside the wind turbine tower.

[0009] In a preferred solution, a first heat exchanger is provided at the cylinder head of the air compressor, the first heat exchanger is connected to a heat storage tank, the heat storage tank is connected to a second heat exchanger, and the second heat exchanger is provided on the expander for heating the compressed air.

[0010] In a preferred solution, a second clutch is further provided between the transmission and the wind turbine generator.

[0011] In a preferred embodiment, in the air compressor, the first clutch is connected to a vertically arranged crankshaft through a transmission mechanism, and a plurality of cylinder heads are evenly distributed along the circumference of the crankshaft. The plurality of cylinder heads are located in the same layer or in different layers. The crankshaft is connected to the piston through a plurality of connecting rods, and the piston is slidably installed in a cylinder body of a cylinder head. An exhaust check valve and an intake check valve are provided at the end of the cylinder body.

[0012] In a preferred solution, the exhaust check valve is connected to the same pipeline and then connected to the air storage tank through a valve group; or the exhaust check valve is connected to another intake check valve to form a full series mode or a series-parallel combination mode for each cylinder head; The first clutch is arranged upstream of the transmission, and comprises a driving plate axially slidably connected to the fan shaft, a plurality of spline slide rails are arranged on the outer wall of the fan shaft, a corresponding slide groove is arranged on the inner wall of the driving plate, and a pushing device for controlling the clutch is also arranged on one side of the driving plate, and a friction clutch connection is formed between the driven plate rotatably supported and the driving plate; The driven plate is connected to the bevel gear set through a belt mechanism, and the bevel gear set is connected to the crankshaft.

[0013] A control method using the above-mentioned combined device of wind power generation and compressed air energy storage comprises the following steps: S1, first working mode: the first clutch is disconnected, the impeller drives the fan generator to rotate through the fan shaft and the transmission, and the fan generator generates electricity and transmits it to the power transmission device; Second working mode: the first clutch is engaged, the fan generator generates electricity and transmits it to the power transmission and transformation device; at the same time, the air compressor works to compress the air and send it into the air storage tank; The circulating pump of the heat storage tank is started to transport the heat exchange medium to the first heat exchanger for heat exchange, and the heat is stored in the heat storage tank; The third working mode: the first clutch is engaged and the air compressor works to compress the air and send it into the air storage tank, and the heat storage tank exchanges heat and stores it; The second clutch is disengaged and the fan generator does not work.

[0014] The fourth working mode: the air storage tank is connected to the expander, the expander drives the compressed air generator to rotate, and the compressed air generator generates electricity and transmits it to the power transmission and transformation device; S2. Switch to different working modes according to instructions.

[0015] In a preferred solution, the first working mode, the second working mode, the fourth working mode and the combination of the second working mode and the fourth working mode are switched according to the wind speed; According to the grid peak and frequency regulation instructions, switch to the third working mode or the first working mode, the second working mode, the fourth working mode and the combination of the second working mode and the fourth working mode.

[0016] In a preferred solution, in the second working mode and the third working mode, the normal working condition and the boost working condition are switched according to the pressure in the air storage tank; The normal working condition is that the air compressor directly compresses the atmosphere and sends it into the air storage tank. The normal working condition includes full series mode, series-parallel combination mode and full parallel mode. The boosting condition is that the air compressor further compresses the compressed air in one air storage tank and sends it to another air storage tank.

[0017] The present invention provides a combined device of wind power generation and compressed air energy storage and a control method. By utilizing an impeller to directly drive an air compressor during idle time and utilizing compressed air for power generation, wind power exceeding a threshold value can be fully utilized, and wind energy during idle time when wind power is predicted to be idle can be converted into compressed air energy for storage. The stored compressed air can be used to make up for the difference between wind power prediction and actual production, thereby improving the efficiency of the wind farm and the peak-valley control capability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0019] Figure 2 It is a structural schematic diagram of the air compressor part of the present invention.

[0020] Figure 3 It is a schematic diagram of the top structure of the air compressor of the present invention.

[0021] Figure 4 Flow chart of the control method of the present invention.

[0022] Figure 5 It is a schematic diagram of the wind farm-based control strategy of the present invention.

[0023] Figure 6 It is a schematic diagram of the control strategy based on power grid load of the present invention.

[0024] In the figure: a first clutch 1, a transmission 2, a second clutch 3, a fan generator 4, a fan chamber 5, a first heat exchanger 6, an air compressor 7, a driven plate 701, a driving plate 702, a spline slide rail 703, a fan shaft 704, a pushing device 705, a transmission belt 706, a bevel gear set 707, a crankshaft 708, a connecting rod 709, a cylinder head 710, a first heat exchanger 711, an exhaust check valve 712, an intake check valve 713, a piston 714, a cylinder body 715, a transmission plate 716, a fan tower 8, a circulating pump 9, an air storage tank 10, a heat storage tank 11, a power transmission and transformation device 12, a second heat exchanger 13, an expander 14, and a compressed air generator 15. DETAILED DESCRIPTION

[0025] Embodiment 1: like Figures 1 to 3 In the invention, a combined device of wind power generation and compressed air energy storage includes a first clutch 1, an air compressor 7, an air storage tank 10 and an expander 14 arranged on a fan shaft 704, wherein the first clutch 1 is connected to the air compressor 7 through a transmission mechanism to drive the air compressor 7 to rotate; The output port of the air compressor 7 is connected to the inlet port of the air storage tank 10, the outlet of the air storage tank 10 is connected to the expander 14, the expander 14 is connected to the generator, and the generator is electrically connected to the power transmission and transformation device 12. With this structure, the comprehensive benefits of wind power generation and compressed air power generation are achieved.

[0026] The preferred solution is Figure 1 There are at least two air storage tanks 10, and the air compressor 7 is connected to each air storage tank 10 through a valve group; with this structure, the pressure in the air storage tank 10 can be further increased.

[0027] Under normal working conditions, the air intake check valve 713 of the air compressor 7 is connected to the atmosphere, and the air exhaust check valve 712 of the air compressor 7 is connected to one of the air storage tanks 10; Under the supercharging condition, one air storage tank 10 is connected to the intake check valve 713 of the air compressor 7, and the other air storage tank 10 is connected to the exhaust check valve 712 of the air compressor 7. With this solution, the compressed air in the air storage tank 10 meets the power generation requirements of the expander 14, and the storage space of the compressed air can be saved.

[0028] The preferred solution is Figure 1 In the figure, the air storage tank 10 is located in the wind turbine tower 8.

[0029] The preferred solution is Figure 1 In the embodiment, a first heat exchanger 6 is provided at the cylinder head 710 of the air compressor 7, the first heat exchanger 6 is connected to a heat storage tank 11, the heat storage tank 11 is connected to a second heat exchanger 13, and the second heat exchanger 13 is provided on an expander 14 for heating compressed air. With this structure, the efficiency of compressed air power generation can be further improved.

[0030] The preferred solution is Figure 1 In the embodiment, a second clutch 3 is further provided between the transmission 2 and the wind turbine generator 4. The second clutch 3 is used to disconnect the transmission between the transmission 2 and the wind turbine generator 4 so that the wind turbine generator 4 does not work under certain working conditions.

[0031] The preferred solution is Figure 2 In the air compressor 7, the first clutch 1 is connected to a vertically arranged crankshaft 708 through a transmission mechanism. A plurality of cylinder heads 710 are evenly distributed along the circumference of the crankshaft 708. The plurality of cylinder heads are located at the same layer. Figure 3 As shown in or not in the same layer, the crankshaft 708 is connected to the piston 714 through multiple connecting rods 709, and the piston 714 is slidably installed in a cylinder body 715 of a cylinder head 710. An exhaust check valve 712 and an intake check valve 713 are provided at the end of the cylinder body 715.

[0032] In the scheme where multiple cylinder heads are arranged in the same layer, the crankshaft 708 is connected to the connecting rod 709 of each cylinder head 710 via the transmission plate 716. The advantage of this scheme is that the degree of distortion of the crankshaft 708 can be reduced. The diameter of the crankshaft 708 is reduced.

[0033] The preferred solution is Figure 3 In the embodiment, the exhaust check valves 712 of all cylinder heads 710 are connected to the same pipeline and then connected to the air storage tank 10 through the valve group, which constitutes a full parallel mode. In this mode, the air compressor 7 obtains a larger flow rate; or the exhaust check valve 712 is connected to another intake check valve 713 to form a full series mode or a series-parallel combination mode for each cylinder head 710; Taking four cylinder heads 710 as an example, the exhaust check valve 712 of each cylinder head 710 is connected to another intake check valve 713 in turn, leaving only one intake check valve 713 for intake and one exhaust check valve 712 for exhaust, which constitutes a full series mode. In this mode, the air compressor 7 obtains a larger output pressure.

[0034] Taking four cylinder heads 710 as an example, the cylinder heads 710 are divided into two groups. In each group, the exhaust check valve 712 of one cylinder head 710 is connected to the intake check valve 713 of another cylinder head 710. In each group, there is an intake check valve 713 for intake and an exhaust check valve 712 for exhaust, which constitutes a series-parallel combination mode. In this mode, the flow and pressure are balanced.

[0035] The first clutch 1 is arranged upstream of the transmission 2, and comprises a driving disc 702 axially slidably connected to the fan shaft 704, a plurality of spline rails 703 are arranged on the outer wall of the fan shaft 704, a corresponding slide groove is arranged on the inner wall of the driving disc 702, the spline rails 703 and the slide groove constitute a torque transmission structure, a pushing device 705 for controlling the clutch is also arranged on one side of the driving disc 702, and a friction clutch connection is formed between the driven disc 701 rotatably supported and the driving disc 702; Preferably, there are two ways to set the push device 705. One is that the push device 705 uses a cylinder or an electric push rod. The push device 705 pushes the axial displacement of the active disk 702, so that the active disk 702 and the driven disk 701 form a friction transmission pair. A tension spring is provided on one side of the active disk 702 to disengage the friction between the active disk 702 and the driven disk 701. The advantages of this solution are simple structure, high reliability, and flexible clutch. The other is to open a "C"-shaped groove on the back of the active disk 702, and set a ball head at the end of the push device 705. The push device 705 is symmetrically set with 2 to 3 balls, and the ball heads are slidably connected in the "C"-shaped groove to achieve axial movement of the driving disk 702.

[0036] like Figure 2 As shown in , the driven plate 701 is connected to the bevel gear set 707 through a belt mechanism, and the bevel gear set 707 is connected to the crankshaft 708, driving the crankshaft 708 to rotate, thereby driving each piston 714 to reciprocate.

[0037] Embodiment 2: like Figure 4 As shown in , a control method using the above-mentioned combined device of wind power generation and compressed air energy storage includes the following steps: S1, first working mode: the first clutch 1 is disconnected, the impeller drives the fan generator 4 to rotate through the fan shaft 704 and the transmission 2, and the fan generator 4 generates electricity and transmits it to the power transmission and transformation device 12; The second working mode: the first clutch 1 is engaged, the fan generator 4 generates electricity and transmits it to the power transmission and transformation device 12; at the same time, the air compressor 7 works to compress the air and then sends it into the air storage tank 10; The circulation pump 9 of the heat storage tank 11 is started to transport the heat exchange medium to the first heat exchanger 6 for heat exchange, and store the heat in the heat storage tank 11; in this mode, higher production efficiency can be achieved.

[0038] The third working mode: the first clutch 1 is engaged with the air compressor 7 to work and compress the air and send it into the air storage tank 10, and the heat storage tank 11 exchanges heat and stores it; The second clutch 3 is disconnected, and the wind turbine generator 4 does not work. In this mode, when the wind power forecast is less than the actual power generation, the excess power is difficult to be incorporated into the power grid. Therefore, it is more efficient to adjust it in the form of energy storage than to waste it.

[0039] The fourth working mode: the air storage tank 10 is connected to the expander 14, the expander 14 drives the compressed air generator 15 to rotate, and the compressed air generator 15 generates electricity and transmits it to the power transmission and transformation device 12; when the wind power forecast is greater than the actual power generation and there is a shortage of power supply in the power grid, the expander 14 is started to supplement more power generation to avoid affecting the power grid.

[0040] S2. Switch to different working modes according to instructions.

[0041] In the preferred solution, the first working mode, the second working mode, the fourth working mode and the combination of the second working mode and the fourth working mode are switched according to the wind speed; taking wind speed control as an example, when the wind speed reaches 5 m / s, the second working mode is activated to increase the compressed air reserve and make full use of wind energy. In this state, the fourth working mode can also be synchronously activated to make up for the difference between the predicted power generation and the actual power generation.

[0042] According to the grid peak-shaving and frequency-regulating instructions, switch to the third working mode or the combination of the first working mode, the second working mode, the fourth working mode, and the second working mode and the fourth working mode. The grid peak-shaving and frequency-regulating instructions are partly derived from the previous wind power and even power generation forecasts. However, due to the difficulty in predicting wind resources, it is difficult to ensure that the actual production power generation is consistent with the predicted power generation. When there is an excess or deficiency, it is necessary to compensate by switching the working mode. The compressed air energy storage in the scheme of the present invention can compensate for the inconsistent wind power forecast more flexibly. Among them, the third working mode is to deal with the situation where the actual power generation exceeds the power generation predicted based on wind power. At this time, when the fan is idle, it can fully perform air compression. The combination of the first working mode, the second working mode, the fourth working mode, the second working mode and the fourth working mode is used to deal with the situation where the actual power generation is insufficient relative to the power generation predicted based on wind power, so as to make up for the insufficient power generation. The scheme of the present invention has a low comprehensive cost and high durability, and can greatly reduce the capacity configuration of electrochemical energy storage.

[0043] In the preferred solution, in the second working mode and the third working mode, the normal working condition and the boost working condition are switched according to the pressure in the air storage tank 10; The normal working condition is that the air compressor 7 directly compresses the atmosphere and sends it into the air storage tank 10. The normal working condition includes a full series mode, a series-parallel combination mode and a full parallel mode; The boosting condition is that the air compressor 7 further compresses the compressed air in one air storage tank 10 and sends it to another air storage tank 10.

[0044] Embodiment 3: like Figure 5 As shown in , the wind farm adopting the present invention can effectively make up for the error in wind power prediction. According to the wind power advance prediction curve, the wind power real-time monitoring curve is compared, and the energy storage charging and discharging strategy is formulated in real time according to the difference between the two. When the real-time power is surplus, the wind turbine is controlled to switch to the third working mode for compressed air energy storage. When the real-time power is insufficient, the wind turbine is controlled to switch to the second working mode, the fourth working mode, and the combination of the second working mode and the fourth working mode so that compressed air participates in power generation and releases energy.

[0045] Embodiment 4: like Figure 6As shown in , the power grid using the present invention can dynamically compensate for fluctuations during peak and valley periods of electricity consumption, compare and monitor the power generation and power grid load demand in real time, and formulate energy storage charging and discharging strategies in real time according to the difference between the two. When the power consumption is low, the power grid load demand is less than the real-time power generation, and the fan is controlled to switch to the third working mode for compressed air energy storage. When the power consumption is at peak, the power grid load demand is greater than the real-time power generation, and the fan is controlled to switch to the second working mode, the fourth working mode, and the combination of the second working mode and the fourth working mode so that compressed air participates in power generation and releases energy.

[0046] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A combined device of wind power generation and compressed air energy storage, characterized in that: It comprises a first clutch (1) arranged on a fan shaft (704), an air compressor (7), an air storage tank (10) and an expander (14); the first clutch (1) is connected to the air compressor (7) via a transmission mechanism to drive the air compressor (7) to rotate; The output port of the air compressor (7) is connected to the inlet port of the air storage tank (10), the outlet port of the air storage tank (10) is connected to the expander (14), the expander (14) is connected to the generator, and the generator is electrically connected to the power transmission and transformation device (12).

2. The combined device of wind power generation and compressed air energy storage according to claim 1 is characterized in that: There are at least two air storage tanks (10), and the air compressor (7) is connected to each air storage tank (10) via a valve group; Under normal working conditions, the air intake check valve (713) of the air compressor (7) is connected to the atmosphere, and the air exhaust check valve (712) of the air compressor (7) is connected to one of the air storage tanks (10); Under the boosting condition, one air storage tank (10) is connected to the air intake check valve (713) of the air compressor (7), and the other air storage tank (10) is connected to the air exhaust check valve (712) of the air compressor (7).

3. The combined device of wind power generation and compressed air energy storage according to claim 1 or 2, characterized in that: The air storage tank (10) is located inside the wind turbine tower (8).

4. The combined device of wind power generation and compressed air energy storage according to claim 3 is characterized in that: A first heat exchanger (6) is provided at the cylinder head (710) of the air compressor (7). The first heat exchanger (6) is connected to a heat storage tank (11). The heat storage tank (11) is connected to a second heat exchanger (13). The second heat exchanger (13) is provided on an expander (14) and is used to heat compressed air.

5. The combined device of wind power generation and compressed air energy storage according to any one of claims 1, 2 and 4, characterized in that: A second clutch (3) is also provided between the transmission (2) and the wind turbine generator (4).

6. The combined device of wind power generation and compressed air energy storage according to claim 5 is characterized in that: In the air compressor (7), the first clutch (1) is connected to a vertically arranged crankshaft (708) through a transmission mechanism. A plurality of cylinder heads (710) are evenly distributed along the circumference of the crankshaft (708). The plurality of cylinder heads are located in the same layer or in different layers. The crankshaft (708) is connected to a piston (714) through a plurality of connecting rods (709). The piston (714) is slidably mounted in a cylinder body (715) of a cylinder head (710). An exhaust check valve (712) and an intake check valve (713) are provided at the end of the cylinder body (715).

7. The combined device of wind power generation and compressed air energy storage according to claim 6 is characterized in that: Exhaust check valve (712) are connected to the same pipeline and then connected to the air storage tank (10) through a valve group; or the exhaust check valve (712) is connected to another intake check valve (713) to form each cylinder head (710) in a full series mode or a series-parallel combination mode; The first clutch (1) is arranged upstream of the transmission (2), and comprises a driving disc (702) axially slidably connected to the fan shaft (704), a plurality of spline slide rails (703) are arranged on the outer wall of the fan shaft (704), a corresponding slide groove is arranged on the inner wall of the driving disc (702), and a pushing device (705) for controlling the clutch is also arranged on one side of the driving disc (702), and a friction clutch connection is formed between the driven disc (701) and the driving disc (702) which are rotatably supported; The driven plate (701) is connected to a bevel gear set (707) via a belt mechanism, and the bevel gear set (707) is connected to a crankshaft (708).

8. A control method for a combined wind power generation and compressed air energy storage device according to any one of claims 1 to 7, characterized in that The following steps are involved: S1, first working mode: the first clutch (1) is disconnected, the impeller drives the fan generator (4) to rotate via the fan shaft (704) and the transmission (2), and the fan generator (4) generates electricity and transmits it to the power transmission device (12); Second working mode: the first clutch (1) is engaged, the fan generator (4) generates electricity and transmits it to the power transmission and transformation device (12); at the same time, the air compressor (7) works to compress the air and then transmits it to the air storage tank (10); The circulation pump (9) of the heat storage tank (11) is started to transport the heat exchange medium to the first heat exchanger (6) for heat exchange, and store the heat in the heat storage tank (11); The third working mode: the first clutch (1) engages the air compressor (7) to work and compress the air and send it into the air storage tank (10), and the heat storage tank (11) exchanges heat and stores the air; The second clutch (3) is disconnected and the fan generator (4) does not work. Fourth working mode: the air storage tank (10) is connected to the expander (14), the expander (14) drives the compressed air generator (15) to rotate, and the compressed air generator (15) generates electricity and transmits it to the power transmission and transformation device (12); S2. Switch to different working modes according to instructions.

9. The control method of the combined device of wind power generation and compressed air energy storage according to claim 8 is characterized by: Switching between the first working mode, the second working mode, the fourth working mode and the combination of the second working mode and the fourth working mode according to the wind speed; According to the grid peak and frequency regulation instructions, switch to the third working mode or the first working mode, the second working mode, the fourth working mode and the combination of the second working mode and the fourth working mode.

10. The control method of the combined device of wind power generation and compressed air energy storage according to claim 8 is characterized by: In the third working mode, the normal working condition and the boost working condition are switched according to the pressure in the air storage tank (10); The normal working condition is that the air compressor (7) directly compresses the atmosphere and then sends it into the air storage tank (10). The normal working condition includes a full series mode, a series-parallel combination mode, and a full parallel mode. The boosting condition is that the air compressor (7) further compresses the compressed air in one air storage tank (10) and then sends it to another air storage tank (10).

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