Gravity energy storage system

Abstract

To reduce power consumption when lifting a weight to an elevated position in a gravity energy storage system.SOLUTION: A gravity energy storage system 101 lifts a weight 10 from a low position to a high position during energy storage by winding a wire 12 connected to the weight 10 using a rotary machine 20. During power generation, it lowers the weight 10 from the high position to the low position, inputting rotation to the rotary machine 20, thereby operating the rotary machine 20 as a generator. A platform 30 for placing the weight 10 is provided at the low position. A lift device 32 equipped on the platform 30 operates at the timing when the rotary machine 20 begins winding the wire 12 during the energy storage, lifting the platform 30 using force from the pressure of the operating gas. The pressure of the operating gas increases by vaporizing the operating gas liquid through heat exchange with hot water generated from solar heat.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to gravity energy storage systems. [Background technology]

[0002] A gravity energy storage system is a system that uses a rotating machine to wind up a cable and lift a heavy object to a high place, converting the electrical energy supplied to the rotating machine into potential energy of the heavy object and storing it. The potential energy of the heavy object is converted back into electrical energy by lowering the heavy object from a high place to a low place while applying regenerative braking to the rotating machine.

[0003] To improve the energy storage efficiency of a gravity energy storage system, it is important to reduce the power consumed by the rotating machine when lifting a heavy object from a low place to a high place. One method for lifting a heavy object is to use a fluid pressure cylinder, as disclosed in Patent Document 1, for example. However, power is required to drive the fluid pressure cylinder, and replacing the means for lifting a heavy object with a fluid pressure cylinder does not solve the problem of how to reduce power consumption. Furthermore, there are limitations on the height to which a heavy object can be lifted with a fluid pressure cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-322777 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to reduce power consumption when a heavy object is lifted to a high place in a gravity energy storage system. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, a gravity energy storage system, during energy storage, lifts a heavy load from a first position to a second position higher than the first position by winding a wire connected to the heavy load with a rotating machine, and during power generation, lowers the heavy load from the second position to the first position, inputting rotation to the rotating machine, causing the rotating machine to operate as a generator.

[0007] The gravity energy storage system includes a platform located at a first position on which a weight is placed, and a lifting device that operates when the rotating machine starts to wind the wire during energy storage, and that lifts the platform by force exerted by the pressure of the working gas. The lifting device may be configured to operate only for a predetermined period of time from just before the rotating machine starts to wind the wire until just after the rotating machine starts to wind the wire. The lifting device may also be configured to lift the platform by a predetermined height before and after the rotating machine starts to wind the wire.

[0008] The gravity energy storage system includes a heat recovery device that recovers unused heat and a pressure generation device that increases the pressure of the working gas by using the recovered unused heat. The pressure generation device may be configured to increase the pressure of the working gas by vaporizing the liquid of the working gas by using the unused heat. The gravity energy storage system may further include a liquefaction device that recovers the vaporized working gas from the lift device and re-liquefies it.

[0009] The heat recovery device may be a solar water heater that produces hot water from unused solar heat, and the pressure generating device may be a heat exchanger that vaporizes the liquid working gas by heat exchange between the liquid working gas and hot water.If the gravity energy storage system includes a solar power generation device, during energy storage, electricity generated by the solar power generation device may be supplied to the rotating machine, and sunlight not used by the solar power generation device may be supplied to the solar water heater.

[0010] The lift device may be configured to discharge the working gas by utilizing the kinetic energy of the heavy object when the heavy object is lowered to the first position, and may be configured to operate as a gas damper that absorbs energy of a collision between the platform and the heavy object by the working gas when the heavy object is lowered to the first position. [Effects of the Invention]

[0011] According to one embodiment of the present disclosure, during power storage, the lift device operates when the rotating machine begins to wind the wire, and the platform on which the heavy load is placed is lifted by the force of the working gas pressure, thereby reducing the static friction force acting on the drive system including the rotating machine when the wire begins to be wound. By reducing the static friction force acting on the drive system, the amount of power consumed by the rotating machine during power storage is reduced. Meanwhile, while energy is required to operate the lift device, unused heat recovered by the heat recovery device is used to increase the pressure of the working gas that operates the lift device. Therefore, even when viewed as an entire gravity energy storage system, power consumption when lifting a heavy load to a high altitude is reduced. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a gravity energy storage system according to a first embodiment and operation in a storage mode. [Figure 2] FIG. 1 is a schematic diagram illustrating a configuration of a gravity energy storage system according to a first embodiment and operation in a storage mode. [Figure 3] FIG. 1 is a schematic diagram illustrating a configuration of a gravity energy storage system according to a first embodiment and operation in a storage mode. [Figure 4] FIG. 1 is a schematic diagram illustrating a configuration of a gravity energy storage system according to a first embodiment and an operation in a power generation mode. [Figure 5] FIG. 1 is a schematic diagram illustrating a configuration of a gravity energy storage system according to a first embodiment and an operation in a power generation mode. [Figure 6] FIG. 10 is a schematic diagram illustrating the configuration of a gravity energy storage system according to a second embodiment and its operation in a storage mode. [Figure 7]FIG. 10 is a schematic diagram illustrating the configuration of a gravity energy storage system according to a second embodiment and its operation in a storage mode. [Figure 8] FIG. 10 is a schematic diagram illustrating the configuration of a gravity energy storage system according to a second embodiment and its operation in a storage mode. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, gravity energy storage systems according to embodiments of the present disclosure will be described with reference to the drawings.

[0014] 1. First embodiment 1-1. Gravity Energy Storage System Configuration 1 to 5 schematically show the configuration of a gravity energy storage system 101 according to a first embodiment. The gravity energy storage system 101 is a system that converts electrical energy into potential energy of a heavy object 10 and stores the converted energy. The gravity energy storage system 101 has two operating modes: a storage mode in which electrical energy is converted into potential energy of the heavy object 10 and stored, and a power generation mode in which the potential energy of the heavy object 10 is reconverted into electrical energy. The operation of the gravity energy storage system 101 in the storage mode is shown in FIGS. 1 to 3, and the operation of the gravity energy storage system 101 in the power generation mode is shown in FIGS. 4 and 5.

[0015] First, the configuration of the gravity energy storage system 101 will be described with reference to FIG. 1. The gravity energy storage system 101 changes the position of a heavy load 10 between a first position and a second position that is higher than the first position. The height of the second position relative to the first position is several tens to several hundreds of meters. A wire 12 is used to move the heavy load 10 between the first position and the second position. The wire 12 is lowered from a pulley 22 provided vertically above the heavy load 10 and connected to the heavy load 10. The heavy load 10 moves up and down within a shaft 16 while suspended from the wire 12. The shaft 16 extends straight vertically upward from the first position to the second position. The shaft 16 functions, for example, as a windbreak. However, providing the shaft 16 is not necessarily required.

[0016] The heavy load 10 used in the gravity energy storage system 101 has a weight of, for example, several hundred kilograms to several tons. The material of the heavy load 10 can be, for example, concrete or metal. There are no particular limitations on the shape of the heavy load 10 as long as it is a shape that is stable when lifted by the wire 12. For example, the shape of the heavy load 10 may be a rectangular parallelepiped, a cylindrical shape, or a bell shape.

[0017] A rotating machine 20 is connected to the pulley 22. The rotating machine 20 functions as an electric motor when supplied with electric power, and functions as a generator when inputting rotation. In the gravity energy storage system 101, by making the rotating machine 20 function as an electric motor, the wire 12 can be wound up by the pulley 22, and the heavy load 10 connected to the wire 12 can be lifted to the second position. Conversely, by making the rotating machine 20 function as a generator, the wire 12 can be let out from the pulley 22 while applying regenerative braking, and the heavy load 10 can be lowered to the first position. A reducer (not shown) may be provided between the rotating machine 20 and the pulley 22.

[0018] Electric power for causing the rotating machine 20 to function as an electric motor is supplied from the solar power generation device 50. However, in addition to the electric power generated by the solar power generation device 50, electric power generated by natural energy other than sunlight or electric power supplied from the electric power grid may also be supplied to the rotating machine 20. Electric power generated by causing the rotating machine 20 to function as a generator may be supplied to the electric power grid, or may be supplied directly to consumers such as factories.

[0019] A platform 30 on which the heavy load 10 is placed is provided at the first position. The platform 30 is equipped with a lifting device 32. The lifting device 32 is a device that lifts the platform 30 by the pressure of working gas. The lifting device 32 extends vertically upward when high-pressure working gas is supplied thereto, and contracts vertically downward when the working gas is exhausted therefrom. An air cylinder that expands and contracts according to the pressure of the working gas is provided inside the lifting device 32, for example.

[0020] In the gravity energy storage system 101, unused heat is used to increase the pressure of the working gas. Unused heat is heat that is discarded without being used, and includes solar heat and waste heat from factories. When the working gas is in a liquid state, supplying unused heat causes the working gas to vaporize, greatly expanding its volume. By vaporizing the working gas using unused heat in this way and thereby increasing the pressure of the working gas, it becomes possible to lift the platform 30 without consuming electricity.

[0021] In the gravity energy storage system 101, the working gas that operates the lift device 32 is stored in a liquid state in a storage tank 34. The working gas is a gas that has a boiling point near room temperature, such as alcohol, ammonia, or ether. In other words, a gas that can be easily controlled between a gaseous and liquid state is used as the working gas. The storage tank 34 is connected to the lift device 32, and the liquid working gas is supplied from the storage tank 34 to the lift device 32.

[0022] A heat exchanger 40 is provided between the storage tank 34 and the lift device 32. Hot water produced by a solar water heater 42 is supplied to the heat exchanger 40. That is, in this embodiment, solar heat is used as unused heat. The solar water heater 42 can be considered a heat recovery device that recovers unused heat. The temperature of the hot water supplied to the heat exchanger 40 can be indirectly adjusted by adjusting the flow rate with a pump 44. The solar water heater 42 can be installed in combination with a solar power generation device 50. Specifically, sunlight is received by the solar power generation device 50, and the thermal energy of the sunlight not used for power generation can be used by the solar water heater 42 to produce hot water.

[0023] The liquid working gas supplied from the storage tank 34 is heat exchanged with hot water in the heat exchanger 40. The temperature of the hot water supplied to the heat exchanger 40 is adjusted to a temperature above the boiling point of the working gas. Therefore, the liquid working gas is vaporized in the heat exchanger 40, and the gasified working gas is supplied to the lift device 32. The heat exchanger 40 can be considered as a pressure generating device that increases the pressure of the working gas using the recovered unused heat. A supply valve (not shown) is provided between the heat exchanger 40 and the lift device 32. The timing at which the lift device 32 lifts the platform 30 can be controlled by the timing at which the supply valve is opened to supply the working gas to the lift device 32.

[0024] A return pipe is connected to the lift device 32 for returning the working gas to the storage tank 34. A buffer tank 36 is provided on the return pipe. The working gas discharged from the lift device 32 is temporarily stored in the buffer tank 36. As described above, the working gas used in the gravity energy storage system 101 has a boiling point near room temperature. Therefore, the working gas stored in the buffer tank 36 liquefies when the outside temperature drops, for example, at night. The liquefied working gas is pressure-fed to the storage tank 34 by a pump 38. Note that in areas where the outside temperature is high even at night and the working gas does not liquefy in the buffer tank 36, a compressor can be provided instead of the pump 38. The buffer tank 36, or the buffer tank 36 and the compressor, can be considered as a liquefaction device that recovers the vaporized working gas from the lift device 32 and re-liquefies it.

[0025] 1-2. Operation in power generation mode Next, the operation of the gravity energy storage system 101 in the energy storage mode will be described with reference to Figures 1 to 3. As shown in Figure 1, the position of the heavy load 10 when the lift device 32 is retracted and the platform 30 is lowered to the lowest position is the first position. In the energy storage mode, the electric power generated by the solar power generation device 50 is supplied to the rotating machine 20, and the rotating machine 20 is caused to wind up the wire 12, thereby lifting the heavy load 10 in the first position.

[0026] The lifting device 32 operates in conjunction with the timing at which the rotating machine 20 starts to wind the wire 12. Specifically, the lifting device 32 starts to operate immediately before the rotating machine 20 starts to wind the wire 12, and stops immediately after the rotating machine 20 starts to wind the wire 12. The operating time of the lifting device 32 during this time is limited to a predetermined time (e.g., several seconds to several tens of seconds). Alternatively, the lifting device 32 may be operated so as to push up the platform 30 by a predetermined height (e.g., several tens of centimeters to several meters). In either case, in the power storage mode, the rotating machine 20 starts to wind up the wire 12 while the lifting device 32 operates to push up the heavy load 10 together with the platform 30.

[0027] In this way, in the power storage mode, the lift device 32 operates at the same time that the rotating machine 20 starts to wind the wire 12, thereby reducing the static friction force acting on the drive system including the rotating machine 20 and the pulley 22 when winding the wire 12 begins. In other words, when the rotating machine 20 starts to move, the heavy load 10 has already been moved by the lift device 32, so the static friction force acting on the drive system that is influenced by the weight of the heavy load 10 is reduced. By reducing the static friction force acting on the drive system, the amount of power consumed by the rotating machine 20 during power storage is reduced. Meanwhile, solar heat recovered by the solar hot water heater 42 is used as energy to increase the pressure of the working gas that operates the lift device 32, so power consumption when lifting the heavy load 10 to a high place is reduced even when viewed as the gravity power storage system 101 as a whole.

[0028] 2, after the lift device 32 is extended to its maximum height and the heavy load 10 is released from the platform 30, the heavy load 10 is lifted only by the force of the rotating machine 20 winding up the wire 12. During this time, the electrical energy supplied to the rotating machine 20 is converted into potential energy of the heavy load 10.

[0029] Then, as shown in Figure 3, when the heavy load 10 reaches its maximum height, i.e., the second position, the rotating machine 20 stops. When the heavy load 10 is in the second position, the rotation of the pulley 22 is mechanically stopped by a brake device or a locking device. When the heavy load 10 is in the second position, the potential energy is at its maximum. Unlike electrical energy, potential energy does not decrease naturally. The gravity energy storage system 101 can store energy for a long period of time by keeping the heavy load 10 in the second position.

[0030] 1-3. Operation in power generation mode Next, operation of the gravity energy storage system 101 in the power generation mode will be described with reference to Figs. 4 and 5. As shown in Fig. 4, in the power generation mode, the heavy load 10 is lowered from the second position to the first position. During this time, the rotation of the pulley 22 caused by the descent of the heavy load 10 is input to the rotating machine 20, causing the rotating machine 20 to operate as a generator. By operating the rotating machine 20 as a generator, a regenerative braking force is generated, and the heavy load 10 descends at a limited speed. During this time, the potential energy of the heavy load 10 is converted into electrical energy by the rotating machine 20 as a generator.

[0031] Then, as shown in FIG. 5, the heavy load 10 eventually lands on the platform 30. Even just before the heavy load 10 lands on the platform 30, the heavy load 10 has a vertically downward velocity. Therefore, the heavy load 10 collides with the platform 30, but the energy of the collision is absorbed by the working gas in the lift device 32. In other words, the lift device 32 operates as a gas damper, thereby mitigating the impact of the heavy load 10 when it lands on the platform 30. The lift device 32 also uses the weight of the heavy load 10 to discharge the working gas therein. A discharge valve (not shown) is provided between the lift device 32 and the buffer tank 36. The discharge valve is opened when the heavy load 10 lands on the platform 30, thereby discharging the working gas while absorbing the impact of the collision. Discharging the working gas therein causes the lift device 32 to contract, and the heavy load 10 returns to the first position, which is its initial position.

[0032] 2. Second embodiment 6 to 8 schematically show the configuration of a gravity energy storage system 102 according to the second embodiment. The gravity energy storage system 102 also has two operation modes: a storage mode in which electrical energy is converted into potential energy of the heavy load 10 and stored, and a power generation mode in which the potential energy of the heavy load 10 is reconverted into electrical energy. 6 to 8 show the operation of the gravity energy storage system 102 in the storage mode. In each figure, elements common to those in the gravity energy storage system 101 according to the first embodiment are denoted by the same reference numerals.

[0033] The gravity storage system 101 according to the first embodiment differs from the gravity storage system 102 according to the second embodiment in that the gravity storage system 102 can store multiple heavy loads 10A, 10B, and 10C in the second position. In the initial state of the storage mode, as shown in FIG. 6 , the lift device 32 is retracted and the platform 30 is lowered to the lowest position. In this state, the first heavy load 10A is placed on the platform 30. Then, as described in the first embodiment, in the storage mode, the lift device 32 is activated to push up the heavy load 10A together with the platform 30, while the rotating machine 20 starts winding the wire 12.

[0034] As shown in Figure 7, after the lifting device 32 is extended to its maximum height and the heavy load 10A is released from the platform 30, the heavy load 10A is lifted only by the force of the rotating machine 20 winding up the wire 12. During this time, the electrical energy supplied to the rotating machine 20 is converted into potential energy of the heavy load 10A. After the heavy load 10A is released from the platform 30, the working gas is discharged from the lifting device 32, and the platform 30 is lowered to a position where the next heavy load 10B can be placed.

[0035] As shown in Figure 8, when the heavy load 10A reaches its maximum height, i.e., the second position, the rotating machine 20 stops. At the second position, the heavy load 10A is detached from the wire 12, and the detached heavy load 10A is transported to a storage location. Meanwhile, at the first position, the next heavy load 10B is placed on the platform 30. By rotating the rotating machine 20 in the reverse direction, the wire 12 is lowered and connected to the heavy load 10B at the first position. Once the wire 12 is connected to the heavy load 10B, the lifting device 32 is operated again, and while the lifting device 32 and the platform 30 push up the heavy load 10B, the rotating machine 20 starts winding the wire 12.

[0036] By repeating the above operation, the multiple heavy loads 10A, 10B, and 10C are stored in the storage area at the second location. According to the gravity energy storage system 102, by storing the multiple heavy loads 10A, 10B, and 10C in the storage area at the second location, it is possible to store a larger amount of energy for a longer period of time. In the power generation mode, the heavy loads 10A, 10B, and 10C are lowered one by one in the reverse order of the power storage mode.

[0037] Furthermore, in gravity energy storage system 102, lift device 32 operates when rotating machine 20 starts to wind wire 12 during energy storage, and platform 30 is lifted by the force of the pressure of the working gas, so that, similar to gravity energy storage system 101, power consumption when lifting heavy objects 10A, 10B, and 10C to a high place is reduced.

[0038] 3. Other embodiments In each of the above embodiments, the lift device 32 is operated by utilizing the increase in pressure that occurs when the liquid working gas vaporizes. Alternatively, unused heat may be supplied to a working gas that is already in a gaseous state to thermally expand the working gas, thereby operating the lift device 32. The working gas to be thermally expanded may be a gas with a low specific heat, such as air, oxygen, or carbon dioxide.

[0039] In the second embodiment, the wire 12 is repeatedly raised and lowered to lift the multiple heavy loads 10A, 10B, and 10C to the second position. Alternatively, an endless wire that goes around like a ropeway may be rotated by the rotating machine 20. In the power storage mode, the heavy loads 10A, 10B, and 10C may be hung from an endless wire driven by the rotating machine 20 and continuously transported from the first position to the second position. In the power generation mode, the heavy loads 10A, 10B, and 10C may be hung from an endless wire and continuously transported from the second position to the first position while a regenerative braking force is applied by the rotating machine 20. [Explanation of symbols]

[0040] 10, 10A, 10B, 10C heavy objects 12 wire 20 Rotating Machine 22 Pulley 30 units 32 Lifting device 34 Storage Tank 36 Buffer Tank 42 Solar water heater 40 Heat exchanger 50 Solar power generation equipment 101, 102 Gravity Energy Storage System

Claims

1. a gravity energy storage system in which, during energy storage, a wire connected to a heavy object is wound by a rotating machine, thereby lifting the heavy object from a first position to a second position higher than the first position, and, during power generation, the heavy object is lowered from the second position to the first position, and rotation is input to the rotating machine, causing the rotating machine to operate as a generator, a platform provided at the first position on which the heavy object is placed; a lift device that operates when the rotating machine starts to wind the wire during power storage and lifts the platform by the force exerted by the pressure of the working gas; a heat recovery device that recovers unused heat; a pressure generating device that increases the pressure of the working gas by the recovered unused heat. A gravity energy storage system.

2. 2. The gravity energy storage system of claim 1, The lifting device is configured to operate only for a predetermined time period from just before the rotating machine starts to wind the wire until just after the rotating machine starts to wind the wire. A gravity energy storage system.

3. 2. The gravity energy storage system of claim 1, The lift device is configured to lift the platform by a predetermined height before and after the rotating machine starts winding the wire. A gravity energy storage system.

4. The gravity energy storage system according to any one of claims 1 to 3, The pressure generating device is configured to increase the pressure of the working gas by vaporizing the liquid of the working gas using the unused heat. A gravity energy storage system.

5. The gravity energy storage system according to claim 4, The heat recovery device includes a solar water heater that produces hot water from solar heat, which is the unused heat, The pressure generating device includes a heat exchanger that vaporizes the liquid working gas by heat exchange between the liquid working gas and the hot water. A gravity energy storage system.

6. 6. The gravity energy storage system according to claim 5, Further equipped with a solar power generation device, During power storage, the power generated by the solar power generation device is supplied to the rotating machine, and the sunlight not used by the solar power generation device is supplied to the solar water heater. A gravity energy storage system.

7. The gravity energy storage system according to claim 4, The lifting device further includes a liquefaction device that recovers the vaporized working gas from the lifting device and re-liquefies the gas. A gravity energy storage system.

8. The gravity energy storage system according to claim 4, The lift device is configured to discharge the working gas by utilizing the kinetic energy of the heavy object when the heavy object is lowered to the first position. A gravity energy storage system.

9. The gravity energy storage system according to claim 4, The lift device is configured to operate as a gas damper that absorbs the energy of a collision between the platform and the heavy object by the working gas when the heavy object is lowered to the first position. A gravity energy storage system.

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