Flywheel and flywheel energy storage system

Abstract

To provide a flywheel having a high energy density and a power storage system capable of achieving both an increase in stored energy and a weight reduction by adopting the flywheel.SOLUTION: A flywheel A includes a rotating shaft, a low-density disk portion 10, and a high-density outer edge portion 11. The low-density disk portion 10 is integrally supported by the rotation shaft, and the whole body of it is located to the rotation axis X side inside the inner peripheral surface of the high-density outer edge portion 11. The high-density outer edge portion 11 is integrally supported by the low-density disk portion 10 and the whole body of it is located outside the low-density disk portion 10. The rotation of the rotation shaft is transmitted to the high-density outer edge portion 11 via the low-density disk portion 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a flywheel and a flywheel power storage system. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known a flywheel power storage system that stores electrical energy as kinetic energy by rotating a flywheel (see, for example, Patent Document 1 below).

[0003] The flywheel used in a flywheel energy storage system is generally a disk made of one type of material with uniform density throughout, as in Patent Document 1 below, or a disk with an outer periphery made of a material with a lower density than the disk. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6323641 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional configuration, when attempting to rotate flywheels of the same size (volume) at the same rotational angular velocity, there is a problem in that sufficient mass energy density cannot be obtained.

[0006] In view of the above, an object of the present invention is to provide a flywheel having a high energy density, and an energy storage system that employs the flywheel to achieve both increased stored energy and reduced weight. [Means for solving the problem]

[0007] The present invention provides a flywheel for a flywheel energy storage system, comprising a rotating shaft, a low-density disk portion having a relatively low average density, and a high-density outer edge portion having an average density higher than that of the low-density disk portion, wherein the low-density disk portion is supported integrally with the rotating shaft and its entirety is located closer to the rotation axis than the inner surface of the high-density outer edge portion, and the high-density outer edge portion is supported integrally with the low-density disk portion and its entirety is located outside the low-density disk portion, and wherein rotation of the rotating shaft is transmitted to the high-density outer edge portion via the low-density disk portion.

[0008] Because the flywheel of the present invention is composed of a low-density disk portion and a high-density outer edge portion, when rotated at the same angular velocity with the same volume, it can achieve a higher mass energy density than conventional flywheels (which are made of a disk formed with a uniform density throughout from one type of material, or which have an outer edge portion around the outer periphery of a disk made from a material with a lower density than the disk).

[0009] In the flywheel of the present invention, when an improvement in mass energy density is to be obtained by 10% or more compared to a conventional flywheel using a disk formed of a single type of material with a uniform density throughout, the average density of the low-density disk portion is set to ρ i , radius R i , the average density of the high-density outer edge is ρ o , radius R o Then, R i / R o is between 0.4 and 1, and ρ i / ρ o should be set to 0.6 or less.

[0010] In the flywheel of the present invention, when an improvement in mass energy density is to be obtained by 50% or more compared with a conventional flywheel using a disk formed with a uniform density entirely from one kind of material, the average density of the low density disk portion is set to ρ i , radius is R i , the average density of the high-density outer edge is ρ o , radius is R o Then, R i / Ro is greater than or equal to 0.8 and less than 1, and ρ i / ρ o should be set to 0.1 or less.

[0011] When designing the flywheel, the average density of the low density disk portion is ρ i , radius R i , the average density of the high-density outer edge is ρ o , radius R o Then, R is set to increase the value Z defined by the following formula (1). i / R o and ρ i / ρ o The following points should be considered:

[0012]

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[0013] Equation (1) is the energy density ratio between the flywheel of the present invention and a conventional flywheel made of a disk formed to a uniform density throughout using a single type of material (hereinafter simply referred to as the conventional flywheel).

[0014] That is, formula (1) can be obtained as follows: From the relationship between the mass M, moment of inertia J, and energy E of the conventional flywheel, the energy density of the conventional flywheel is given by formula (2).

[0015]

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[0016] On the other hand, the mass M of the low density disk portion of the flywheel of the present invention i , moment of inertia is J i , energy is E i Relationship with

[0017]

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[0018] and the mass M of the low density disk portion of the flywheel of the present invention. o , moment of inertia is J o , energy is E o Relationship with

[0019]

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[0020]

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[0021] From equations (2) and (3), equation (4) can be obtained, which shows the energy density ratio between the flywheel of the present invention and the conventional flywheel. i / R o and ρ i / ρ o It is clear that the rotational angular velocity ω is independent of the rotational angular velocity ω.

[0022]

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[0023] Formula (1) is based on formula (4). Therefore, the value Z of the energy density ratio can be obtained from formula (1). In this way, by using formula (1), a desired energy density ratio can be easily calculated.

[0024] As is clear from this, when designing the flywheel of the present invention, the R i / R o and the above ρ i / ρ o It is preferable to determine:

[0025] Furthermore, when designing the flywheel of the present invention, the variable R i / R o and the variable ρ i / ρ o It is preferable to visually search for an area where the value Z increases by using a matrix table in which the value Z is recorded at the intersections of R and i / R o The values ​​of are arranged vertically. i / ρ o The value of R i / R o and ρ i / ρ o The energy density ratio value Z calculated by equation (1) is recorded at the intersection point with the value of

[0026] By using the matrix table, R i / R o and ρ i / ρ o Therefore, it is possible to very easily and quickly present multiple combination candidates of R i / R o and the above ρ i / ρ o It can be determined that:

[0027] That is, if you want to improve the mass energy density by 10% or more compared to a conventional flywheel, you can use the matrix table shown in Figure 12 to find R i / R o is between 0.4 and 1, and ρ i / ρ o It can be easily determined that R should be 0.6 or less, and when an improvement in mass energy density of 50% or more is to be obtained compared to a conventional flywheel, by using the above matrix table, R i / R o is greater than or equal to 0.8 and less than 1, and ρ i / ρ o It can be easily determined that should be 0.1 or less.

[0028] In the flywheel of the present invention, it is preferable that the low-density disk portion is formed from any one of carbon fiber plastic, silicon carbide fiber reinforced plastic, and light metal, or is formed by selectively combining a plurality of the above materials.

[0029] In the flywheel of the present invention, the high density outer edge portion is preferably formed from any one of heavy metals, carbon fiber plastics having heavy metals embedded therein, and silicon carbide fiber reinforced plastics having heavy metals embedded therein.

[0030] In this case, the heavy metal embedded in the carbon fiber plastic or the heavy metal embedded in the silicon carbide fiber reinforced plastic may be in the form of powder, wire, or pieces arranged in a circular equiangular symmetry.

[0031] Of these, it is preferable that the heavy metal pieces arranged in circumferential equiangular symmetry have a shape that protrudes toward the rotation axis of the high-density outer edge portion.

[0032] The present invention also provides a flywheel energy storage system comprising a generator motor, a rotating shaft arranged coaxially with an input / output shaft of the generator motor, and a flywheel arranged on the rotating shaft, wherein the flywheel comprises a rotating shaft, a low-density disk portion having a relatively low average density, and a high-density outer edge portion having an average density higher than that of the low-density disk portion, the low-density disk portion being supported by the rotating shaft and entirely located on the rotation axis side of the inner circumferential surface of the high-density outer edge portion, the high-density outer edge portion being supported integrally with the low-density disk portion and entirely located outside the low-density disk portion, and wherein rotation of the rotating shaft is transmitted to the high-density outer edge portion via the low-density disk portion.

[0033] The flywheel energy storage system of the present invention includes a flywheel with a high mass energy density. Therefore, by using a lightweight flywheel, the weight of the entire flywheel energy storage system can be reduced, and a highly efficient flywheel energy storage system can be provided. [Brief description of the drawings]

[0034] [Figure 1] FIG. 2 is a perspective view showing a flywheel according to the first and second embodiments. [Diagram 2] FIG. 11 is a perspective view showing a flywheel according to a third embodiment. [Diagram 3] FIG. 11 is an explanatory cross-sectional view of a flywheel according to a third embodiment. [Figure 4] FIG. 11 is an explanatory cross-sectional view of a flywheel according to a fourth embodiment. [Diagram 5] FIG. 13 is an explanatory cross-sectional view of a flywheel according to a fifth embodiment. [Figure 6] FIG. 13 is an explanatory cross-sectional view of a flywheel according to a sixth, seventh and eighth embodiment. [Figure 7] FIG. 13 is an explanatory cross-sectional view of a flywheel according to a ninth embodiment. [Figure 8] FIG. 13 is a diagram illustrating a schematic configuration of a high-density outer edge portion of a flywheel according to a ninth embodiment. [Figure 9] FIG. 13 is a diagram showing the shape of a metal piece in a flywheel according to a ninth embodiment. [Figure 10] FIG. 13 is an explanatory cross-sectional view showing a modification of a portion of the flywheel according to the ninth embodiment. [Figure 11] FIG. 1 is an explanatory cross-sectional view showing a configuration of a flywheel electricity storage system. [Figure 12] FIG. 13 is a diagram showing an example of a matrix table. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The embodiments of the present invention will be described with reference to the drawings. Flywheels A and B of the first and second embodiments will be described with reference to Fig. 1. The flywheel A of the first embodiment includes a cylindrical low-density disk portion 10 and a cylindrical high-density outer edge portion 11.

[0036] The low density disk portion 10 and the high density outer edge portion 11 have the same thickness dimension t oThe high density outer peripheral portion 11 is integrally provided on the outer periphery of the low density disk portion 10. The high density outer peripheral portion 11 and the low density disk portion 10 are aligned with each other on a rotation axis x which is their center.

[0037] In the flywheel A of the first embodiment, the low-density disk portion 10 has a radius R i is 12cm, average mass density ρ i is 1.6g / cm 3 The high-density outer edge portion 11 is formed of a carbon fiber reinforced plastic (CFRP) having a radius R o is 15cm, average mass density ρ o is 19.25g / cm 3 The thickness dimension t o is formed at 20cm.

[0038] The low-density disk portion 10 may be made of a material other than carbon fiber reinforced plastic (CFRP), such as silicon carbide fiber reinforced plastic (SiCFRP).

[0039] According to the flywheel A of the first embodiment, the value Z of the energy density ratio calculated by the following formula (1) is 1.51, which is a 51% improvement in energy density compared to the conventional flywheel.

[0040]

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[0041] The flywheel B of the second embodiment includes a cylindrical low-density disk portion 20 and a cylindrical high-density outer edge portion 21, similar to the flywheel A of the first embodiment.

[0042] The low density disk portion 20 has a radius R i is 13cm, average mass density ρ i is 1.6g / cm 3 The high density outer edge portion 21 is formed of a carbon fiber reinforced plastic (CFRP) having a radius R o is 15cm, average mass density ρo is 14.2g / cm 3 The thickness dimension t o is 20cm.

[0043] According to the flywheel B of the second embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.49, which is 49% higher in energy density than the conventional flywheel.

[0044] Next, a flywheel C according to a third embodiment will be described. As shown in Figs. 2 and 3, the flywheel C according to the third embodiment includes a disk-shaped low-density disk portion 30 and a cylindrical high-density outer peripheral portion 31. The thickness dimension t i is the thickness dimension t of the high density outer edge portion 31 o Less than.

[0045] The low density disk portion 30 has a thickness dimension t i is 3 cm, radius R i is 13.5cm, average mass density ρ i is 4.5g / cm 3 The high density outer edge portion 31 is formed of titanium having a thickness dimension t o is 20cm, radius R o is 15cm, average mass density ρ o is 19.25g / cm 3 The material is a high melting point metal, such as tungsten.

[0046] According to the flywheel C of the third embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.68, which is a 68% improvement in energy density compared to the conventional flywheel.

[0047] Next, a flywheel D of a fourth embodiment will be described. As shown in FIG. 4, the flywheel D of the fourth embodiment includes a disk-shaped low-density disk portion 40 and a cylindrical high-density outer edge portion 41. The low-density disk portion 40 is composed of a titanium disk 401 and a pair of carbon fiber reinforced plastic disks 402 that sandwich the titanium disk 401. The high-density outer edge portion 41 is provided on the outer periphery of the low-density disk portion 40.

[0048] The titanium disk 401 has a thickness dimension t i1 is 3 cm, radius R i is 13cm, average mass density ρ i1 is 4.5g / cm 3 The carbon fiber reinforced plastic disk 402 has a thickness dimension t i2 is 8.5cm, radius R i is 13cm, average mass density ρ i2 is 1.6g / cm 3 It is.

[0049] The average mass density ρ of the low-density disk portion 40 consisting of the titanium disk 401 and a pair of carbon fiber reinforced plastic disks 402 i is 4.5×(3 / 20)+1.6×(17 / 20)=1.6g / cm 3 It is.

[0050] The high density outer edge portion 41 has a thickness dimension t o is 20cm, radius R o is 15cm, average mass density ρ o is 19.25g / cm 3 The material is a high melting point metal, such as tungsten.

[0051] According to the flywheel D of the fourth embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.51, which is a 51% improvement in energy density compared to the conventional flywheel.

[0052] Next, a flywheel E of a fifth embodiment will be described. As shown in FIG. 5, the flywheel E of the fifth embodiment includes a cylindrical low-density disk portion 50 and a cylindrical high-density outer edge portion 51, similar to the flywheel A of the first embodiment. The low-density disk portion 50 and the high-density outer edge portion 51 have the same thickness and a dimension t o is 20cm.

[0053] The low density disk portion 50 has a radius R i is 13cm, average mass density ρ i is 1.6g / cm 3 The high-density outer edge portion 51 is formed of a carbon fiber reinforced plastic (CFRP) having a radius R o is 15cm, average mass density ρ o is 13.82g / cm 3 The material used is metal fiber reinforced plastic (MFRP), which is reinforced by winding a bundle of 5μm diameter W fine wires in the circumferential direction.

[0054] According to the flywheel E of the fifth embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.49, which is 49% higher in energy density than the conventional flywheel.

[0055] Next, flywheels F, G, H according to sixth, seventh and eighth embodiments will be described with reference to FIG.

[0056] The flywheel F of the sixth embodiment includes a hollow low-density disk portion 60 and a cylindrical high-density outer edge portion 61.

[0057] The low-density disk portion 60 is composed of two disks 601 that face each other in the axial direction with a gap 602 therebetween. Each of the disks 601 that compose the low-density disk portion 60 has a thickness dimension t i is 2 cm, radius R i is 13.5cm, average mass density ρ i2 is 1.6g / cm 3 It is made of carbon fiber reinforced plastic (CFRP).

[0058] The average mass density ρ of the low density disk portion 60 formed by the two disks 602 i is 1.6×((2+2) / 20)=0.32g / cm 3 It is.

[0059] The dense outer edge 61 has a radius R o is 15cm, average mass density ρ o is 5.84g / cm 3 It is made of ultra-hard metal microfiber reinforced plastic (MFRP). o The length is 20 cm. The ultra-hard metal microfiber reinforced plastic (MFRP) is reinforced by wrapping a 10 μm diameter piano microfiber bundle in the circumferential direction.

[0060] According to the flywheel F of the sixth embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.62, which is a 62% increase in energy density compared to the conventional flywheel.

[0061] In the flywheel F of the sixth embodiment, the positions of both disks 601 of the low-density disk section 60 are not limited to the positions shown in FIG. 6, as long as they are housed inside the high-density outer edge section 61. For example, although not shown, the distance between both disks 601 may be closer than that shown in FIG. 6. In the sixth embodiment, the thickness dimension t i In the example shown, two disks 602 with a thickness of 2 cm are used. i Alternatively, three or more small disks may be used to form the low density disk portion 60.

[0062] The flywheel G of the seventh embodiment is composed of a low-density disk portion 70 made of the same material and structure as the sixth embodiment, and a high-density outer edge portion 71 having the same shape and dimensions as the sixth embodiment but made of a different material.

[0063] The low-density disk portion 70 is the same as the low-density disk portion 60 of the sixth embodiment, and therefore its average mass density ρ i is 1.6×((2+2) / 20)=0.32g / cm3 It is.

[0064] The high density outer edge portion 71 of the seventh embodiment is made of plastic (CMFRP resin) reinforced with carbon fiber (CF) and ultra-hard metal fine fiber (MF). The CMFRP resin used for the high density outer edge portion 71 is reinforced by winding a composite bundle of W fine wires and carbon fiber wires (both with a diameter of about 5 to 10 μm) in the circumferential direction. The average mass density ρ o is 6.84g / cm 3 It is.

[0065] According to the flywheel G of the seventh embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.64, and the energy density is improved by 64% compared to the conventional flywheel. Note that, as the CMFRP resin used for the high-density outer edge portion 71, ultra-hard metal fine wires such as piano wires may be used instead of the W fine wires.

[0066] The flywheel H of the eighth embodiment is composed of a low-density disk portion 80 made of the same material and structure as the sixth embodiment, and a high-density outer edge portion 81 that has the same shape and dimensions as the sixth embodiment but is made of a different material.

[0067] The low-density disk portion 80 is the same as the low-density disk portion 60 of the sixth embodiment, and therefore its average mass density ρ i is 1.6×((2+2) / 20)=0.32g / cm 3 It is.

[0068] The high density outer edge portion 81 of the eighth embodiment is formed from a CFRP:M material, which is a solid in which plastic (epoxy resin) with ultra-hard metal M powder dispersed therein is reinforced with carbon fiber (CF).

[0069] The cemented carbide M powder is made of W powder (density ρ o2 =19.25g / cm 3 , particle size 0.7μm, filling rate V f2 =0.25). The plastic is epoxy resin (density ρ o3 =1.15g / cm 3) Carbon fiber has a density of ρ o1 =1.80g / cm 3 , wire diameter 5~10μm, filling rate V f1 =0.45, and is reinforced by winding carbon fiber bundles in the circumferential direction. In this configuration, the average mass density ρ o is 6.84g / cm 3 It becomes.

[0070] According to the flywheel H of the eighth embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.62, and the energy density is improved by 62% compared to the conventional flywheel. In the CFRP:M material used for the high-density outer peripheral portion 81, fine powder of another metal may be used instead of W powder.

[0071] Next, a flywheel I of the ninth embodiment will be described. As shown in Fig. 7 and Fig. 8, the flywheel I of the ninth embodiment is composed of a low-density disk portion 90 made of the same material and structure as the sixth embodiment, and a high-density outer edge portion 91 having the same shape and dimensions as the sixth embodiment.

[0072] Since the low-density disk portion 90 is the same as the low-density disk portion 60 of the sixth embodiment, its average mass density ρ i is 1.6×((2+2) / 20)=0.32g / cm 3 It is.

[0073] The high-density outer edge portion 91 in the flywheel I of the ninth embodiment is formed into a cylindrical shape from carbon fiber reinforced plastic (CFRP), and embedded therein are a plurality of metal pieces 911 that are arranged equiangularly symmetrically around the circumference with a predetermined distance between each other in the circumferential direction.

[0074] All of the metal pieces 911 have the same shape, are made of heavy metal, and are provided in a position such that the tip of the protruding shape faces the rotation axis so as to protrude toward the rotation axis.

[0075] The metal piece 911 has an average mass density ρ o1 is 14.2g / cm3 and the filling rate V f1 is 0.25, and the average mass density ρ of the plastic epoxy resin is o2 is 1.15g / cm 3 Therefore, the average mass density ρ of the high-density outer edge 91 in this configuration is o is 4.41g / cm 3 It becomes.

[0076] According to the flywheel I of the ninth embodiment, the value Z of the energy density ratio calculated by the formula (1) is 1.57, which is a 57% improvement in energy density compared to the conventional flywheel.

[0077] As shown in Fig. 9, metal pieces 911 can be selectively used in various shapes (metal pieces 911, 911a to 911f in Fig. 9). In this case, metal pieces of the same shape are used for the high-density outer edge portion 91, and whichever shape of metal piece 911, 911a to 911f is used, the tip of the protruding shape (the end on the side shown at the top in the figure) is directed toward the rotation axis.

[0078] In addition to having a shape having a length along the rotation axis as shown in Figure 7, the metal piece 911 may also be arranged in a multiple number of metal pieces 911 of short length at intervals in the direction along the rotation axis as shown in Figure 10.

[0079] The flywheels described in the above embodiments can be suitably used in a flywheel power storage system. That is, as shown in Fig. 11, a flywheel power storage system 100 includes a generator motor unit 101 and a flywheel unit 102.

[0080] The flywheel unit 102 includes a flywheel 102a and a housing 102b that houses the flywheel 102a. The flywheel 102a is provided on a rotating shaft 102c and rotates integrally with the rotating shaft 102c.

[0081] The rotating shaft 102c is connected to the input / output shaft 101a of the generator motor unit 101. The rotating shaft 102c of the flywheel 102 is rotatably supported by a pair of bearings 102d provided in the housing 102b.

[0082] The flywheel 102a may have the configuration shown in each of the above-described embodiments (any of flywheels A, B, C, D, E, F, G, H, or I). The storage energy can be easily increased by increasing the thickness or diameter of the flywheel 102a.

[0083] Since the flywheel 102a has the configuration shown in each of the above-mentioned embodiments, it has a high energy density and is lighter than a conventional flywheel, so that the flywheel electricity storage system 100 can be constructed to be lighter.

[0084] Furthermore, by reducing the weight of the flywheel 102a, the energy density at the system level can be improved compared to conventional flywheel power storage systems. [Industrial Applicability]

[0085] The present invention provides a flywheel that can obtain high mass energy density, and a flywheel energy storage system that stores electrical energy as kinetic energy by rotating the flywheel, thereby providing a device that is suitable for storing and utilizing surplus electricity. [Explanation of symbols]

[0086] 100…Flywheel energy storage system 101... Generator motor 101a... Input / Output axis 102c…Rotating shaft A, B, C, D, E, F, G, H, I, 102a…Flywheel 10,20,30,40,50,60,70,80,90...Low density disc section 11,21,31,41,51,61,71,81,91…High density outer edge 911,911a,911b,911c,911d,911e,911f…plain film

Claims

1. A flywheel of a flywheel power storage system, A rotating shaft, a low density disk portion having a relatively low average density, and a high density outer edge portion having a higher average density than the low density disk portion, the low-density disk portion is supported integrally by the rotating shaft, and the entire low-density disk portion is located closer to the rotation axis than the inner circumferential surface of the high-density outer edge portion; the high density outer edge portion is integrally supported by the low density disk portion and is entirely located outside the low density disk portion; A flywheel characterized in that the rotation of the rotating shaft is transmitted to the high density outer edge portion via the low density disk portion.

2. 2. The flywheel of claim 1, The average density of the low density disk portion is ρ i , radius is R i , the average density of the high-density outer edge is ρ o , radius is R o Then, R i / R o is 0.4 or more and less than 1, and ρ i / ρ o is 0.001 or more and 0.6 or less.

3. 2. The flywheel of claim 1, The average density of the low density disk portion is ρ i , radius is R i , the average density of the high-density outer edge is ρ o , radius is R o Then, R i / R o is 0.8 or more and less than 1, and ρ i / ρ o is 0.001 or more and 0.1 or less.

4. 2. The flywheel of claim 1, The flywheel is characterized in that the low-density disk portion is formed from any one of carbon fiber plastic, silicon carbide fiber reinforced plastic, and light metal, or is formed by selectively combining a plurality of the materials.

5. 2. The flywheel of claim 1, A flywheel characterized in that the high-density outer edge portion is formed from any one of a heavy metal, a carbon fiber plastic having a heavy metal embedded therein, and a silicon carbide fiber reinforced plastic having a heavy metal embedded therein.

6. 6. The flywheel of claim 5, The heavy metal used in the high density outer edge portion is ultra-high strength steel, or a high melting point metal, or a high melting point metal alloy.

7. 6. The flywheel of claim 5, A flywheel characterized in that the heavy metal embedded in the carbon fiber plastic or the heavy metal embedded in the silicon carbide fiber reinforced plastic is in the form of powder, wire, or pieces arranged in a circumferentially equiangular symmetry.

8. 8. The flywheel of claim 7, A flywheel characterized in that the heavy metal pieces arranged in circumferential equiangular symmetry are shaped to protrude toward the rotation axis of the high-density outer edge portion.

9. A flywheel power storage system including a generator motor, a rotating shaft provided coaxially with an input / output shaft of the generator motor, and a flywheel provided on the rotating shaft, The flywheel includes a rotating shaft, a low-density disk portion having a relatively low average density, and a high-density outer peripheral portion having an average density higher than that of the low-density disk portion, the low-density disk portion is supported by the rotating shaft and is entirely located on the rotation axis side relative to an inner circumferential surface of the high-density outer edge portion, the high density outer edge portion is integrally supported by the low density disk portion and is entirely located outside the low density disk portion; A flywheel power storage system characterized in that rotation of a rotating shaft is transmitted to the high density outer edge portion via the low density disk portion.

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