Hydraulic power generation device and power generation method

Abstract

The present invention appropriately generates power while suppressing costs. A hydraulic power generation device according to the present disclosure comprises: an impeller that is provided with a blade part having an outer diameter-side blade angle of 25°-90°; a shaft that is connected to the impeller and rotates in accordance with the rotation of the impeller; and a generator that is connected to the shaft and converts kinetic energy generated by the rotation of the shaft into electric energy.

Description

Hydraulic power generation device and power generation method

[0001] The present disclosure relates to a hydraulic power generation device and a power generation method.

[0002] Hydraulic power generation devices are known. A hydraulic power generation device uses the potential energy of water to rotate a waterwheel, and converts the rotational energy of a rotating shaft connected to the waterwheel into electrical energy by a generator having a rotor connected to the rotating shaft.

[0003] For example, Patent Document 1 below discloses a splitter runner of a Francis turbine that can suppress cavitation generated on the surface of a long blade due to the flow of water in the vicinity of the end portion on the flow path outlet side of the short blade of a hydraulic power generation device.

[0004] Japanese Patent Application Laid-Open No. 2009-127554

[0005] However, the Francis turbine described in Patent Document 1 above had problems with the manufacturing cost of the product, such as the need to manufacture it by machining with a high-precision machine tool. Therefore, in small-scale hydropower generation with a power generation amount of, for example, 10,000 kW or less, it is required to generate power appropriately while reducing costs.

[0006] In view of the above problems, an object of the present disclosure is to provide a hydraulic power generation device and a power generation method that can generate power appropriately while suppressing costs.

[0007] The hydraulic power generation device according to the present disclosure includes an impeller having blade roots with an outer diameter side blade angle of 25° or more and 90° or less, a shaft connected to the impeller and rotating with the rotation of the impeller, and a generator connected to the shaft and converting the kinetic energy due to the rotation of the shaft into electrical energy.

[0008] The power generation method according to the present disclosure is a power generation method using the hydraulic power generation device, and includes a step of supplying water to the impeller and a step of rotating a rotor of the generator connected to the shaft by rotating the shaft as the impeller rotates.

[0009] According to this disclosure, it is possible to provide a hydroelectric power generation device and a power generation method that can generate electricity appropriately while keeping costs down.

[0010] Figure 1 is a diagram illustrating the outline of the hydroelectric power generation system according to this disclosure. Figure 2 is a diagram showing an example of the configuration of the hydroelectric power generation system according to this disclosure. Figure 3 is a diagram showing an example of the structure around the impeller according to this disclosure. Figure 4A is a diagram showing an example of the structure of the impeller blades according to this disclosure. Figure 4B is a diagram showing an example of the structure of the impeller blades according to this disclosure. Figure 5 is a diagram showing the relationship between the blade lengths of the main blades and splitter blades of the impeller according to this disclosure. Figure 6 is a diagram showing a first example of the cutting range of the main blades of the impeller according to this disclosure. Figure 7 is a diagram showing a second example of the cutting range of the main blades of the impeller according to this disclosure. Figure 8 is a diagram showing an example of the placement of the flywheel in the hydroelectric power generation system according to this disclosure. Figure 9 is a diagram showing an example of the operation of the hydroelectric power generation system according to this disclosure during normal operation and load shedding. Figure 10 is a diagram showing an example of the placement of the shims in the hydroelectric power generation system according to this disclosure. Figure 11 is a diagram showing an example of the application location of the insulating coating in the hydroelectric power generation system according to this disclosure. Figure 12 shows an example of a divided bearing casing of a hydroelectric power generation device according to the present disclosure.

[0011] Embodiments of this disclosure will be described in detail below with reference to the drawings. However, the embodiments described below will not limit this disclosure.

[0012] (Overview of the hydroelectric power generation device) First, the hydroelectric power generation device 100 related to this disclosure will be explained using Figure 1. Figure 1 is a diagram illustrating the overview of the hydroelectric power generation device related to this disclosure. As shown in Figure 1, the hydroelectric power generation device 100 related to this disclosure is installed inside a container 1 located next to a waterway R, such as a river, drainage from a building 5 which may be a factory or office building, a water receiving line to a factory or office building, or cooling water for air conditioning equipment in a factory or office building. The hydroelectric power generation device 100 is not limited to being installed inside a container 1, but may also be installed inside a building 5 such as a factory or office building. This can contribute to the realization of a ZEB (Zero Energy Building) in which the annual balance of primary energy consumed in the building 5 is zero.

[0013] The hydroelectric power generation device 100 generates electricity by using the potential energy of water taken from agricultural water channels, industrial water channels used in the aforementioned factories, or water and sewage systems to rotate a water turbine, converting the potential energy into kinetic energy from the rotation of the water turbine, and then using a rotating shaft connected to the water turbine to rotate a generator. In addition, the water distribution route through which water from rivers or other water channels leads to the hydroelectric power generation device 100 may be equipped with a mechanism to prevent the inflow of fallen leaves from plants, driftwood, aquatic organisms, etc.

[0014] As shown in Figure 1, water taken in from the intake WI in the waterway R is supplied to the hydroelectric power generation device 100 through the pipeline WP1 and the like. After rotating the turbine of the hydroelectric power generation device 100, the water is returned to the waterway R through the pipeline WP2 and the discharge port WO connected to the waterway R. Note that the arrangement and structure of the pipelines and other components that supply water to the hydroelectric power generation device 100 are not limited to those shown in Figure 1, and may be any other arrangement or structure.

[0015] Furthermore, the effective head, which determines the amount of kinetic energy generated by the water turbine, is the total pressure difference of the water directly in front of the turbine and directly behind it. This is calculated by subtracting the flow loss in the pipeline from the static head, which is the difference in water level when the turbine is stopped in the discharge channel. However, the flow loss in the pipeline changes depending on the water flow rate, and therefore changes depending on the operating conditions of the water turbine.

[0016] Here, the hydroelectric power generation device 100 is preferably a small hydroelectric power generation device with a power generation capacity of 10,000 kW or less, for example, but the size and power generation capacity of the hydroelectric power generation device 100 can be arbitrary.

[0017] Such a hydroelectric power generation device 100 is required to generate electricity appropriately while keeping costs down. The hydroelectric power generation device 100 according to this embodiment is able to generate electricity appropriately while keeping costs down because the impeller 130 has a structure that will be described below.

[0018] (Configuration of the hydroelectric power generation device) Next, the configuration of the hydroelectric power generation device 100 according to the present disclosure will be described with reference to Figure 2. Figure 2 is a diagram showing an example of the configuration of the hydroelectric power generation device according to the present disclosure. The hydroelectric power generation device 100 according to this embodiment is a Francis turbine type hydroelectric power generation device. As shown in Figure 2, the hydroelectric power generation device 100 according to the present disclosure comprises a supply pipe 110, a casing 120, an impeller 130, a discharge pipe 140, a shaft 150, a bearing 160, a bearing casing 170, a coupling 180, and a generator 190. These configurations will be described in order below.

[0019] As shown in Figure 2, the direction parallel to the axial direction of the shaft 150 is defined as the X direction, the direction perpendicular to the X direction is defined as the Y direction, and the direction perpendicular to both the X and Y directions is defined as the Z direction. In this embodiment, the X and Y directions are aligned horizontally and the Z direction is aligned vertically, but it is not limited to this.

[0020] (Supply Piping) The supply piping 110 is connected to the water inlet 121, which is the water inlet to the casing 120 (in this example, the front casing 120A described later) that houses the impeller 130, and is a pipe that supplies water to the impeller 130. The supply piping 110 may be equipped with an inlet solenoid valve 111, which will be described later, in the middle of the pipe, and is configured to allow adjustment of the amount of water supplied to the impeller 130. One end of the supply piping 110 is connected to a pipe WP1 or the like that is connected to the intake WI of the waterway R described above, and the other end is connected to the water inlet 121 of the front casing 120A.

[0021] (Casing) The casing 120 is a container into which water is supplied and which houses the impeller 130. The shape of the casing 120 may be arbitrary, but in this embodiment, the casing 120 includes a front casing 120A and a rear casing 120B.

[0022] (Front Casing) The front casing 120A is part of the container that houses the impeller 130. The front casing 120A includes a water inlet 121 connected to the supply piping 110 described above, a water outlet 122 connected to the discharge piping 140 described later, a flow path 123 through which water flows, and a flange 124 connected to the rear casing 120B. The flow path 123 is a flow path through which the water inlet 121 and water outlet 122 are formed, and which carries water introduced from the water inlet 121 to the water outlet 122. The shape of the flow path 123 can be arbitrary, but in this embodiment, the flow path 123 is composed of a first flow path 123a and a second flow path 123b. The first flow path 123a has a shape in which the flow path extends in a spiral shape, and the water inlet 121 is formed at one end of the spiral flow path. The first flow channel section 123a has a spiral-shaped flow channel, and the other end of the channel is connected to the second flow channel section 123b. The second flow channel section 123b is a flow channel (space) that extends in the X direction and communicates with the first flow channel section 123a. The second flow channel section 123b has openings at both the end on the X direction side and the end on the opposite side of the X direction. The second flow channel section 123b has a water outlet section 122 formed at the other end (the end on the opposite side of the X direction). A flange section 124 is formed around one of the openings (the opening on the X direction side) of the second flow channel section 123b, and the flange section 124 contacts the rear casing 120B, thereby closing the opening on one side of the second flow channel section 123b.

[0023] The front casing 120A may be formed from an aluminum alloy, for example, using die casting. In this embodiment, it is preferable to use a casing for the compressor of a turbocharger as the front casing 120A. Using a casing for the compressor of a turbocharger as the front casing 120A can reduce costs. The turbocharger referred to here may be a turbocharger for a vehicle or ship engine, or a turbocharger for a generator engine. Furthermore, "repurposing" here is not limited to using the same part as is, but also includes modifying it to a shape suitable for hydroelectric power generation through processing or other means.

[0024] (Rear Casing) The rear casing 120B is part of the container provided on the back side of the front casing 120A. The side opposite to the X direction is considered the front, and the side in the X direction is considered the back. The rear casing 120B contacts the flange portion 124 of the front casing 120A and closes the opening on the X direction (back side) of the first flow path portion 123a. The rear casing 120B may be made of, for example, stainless steel.

[0025] (Impeller) The impeller 130 is a turbine that rotates by hydraulic power. That is, the impeller 130 rotates when water is applied to the turbine, thereby rotating the rotor of the generator 190 connected to the shaft 150 connected to the impeller 130. The impeller 130 is housed inside the casing 120. In this embodiment, the impeller 130 is provided in the second flow path section 123b of the front casing 120A with its axial direction aligned with the X direction. More specifically, the impeller 130 has a blade section 136, which will be described later, on one side, and is provided in the second flow path section 123b such that the side with the blade section 136 is located on the front side (opposite to the X direction) and the side without the blade section 136 is located on the back side (X direction side).

[0026] The structure of the impeller 130 will be described later. Any impeller 130 can be used as long as it has the structure described later, but it is preferable to use an impeller that is repurposed from the compressor of a turbocharger. In other words, the impeller 130 may be formed in a shape similar to that of the impeller part of the compressor of a turbocharger. The name impeller 130 means a blade wheel, but in this embodiment, since water is used as the working fluid, it can be said to be a water turbine. By using a water turbine that corresponds to the compressor part of a mass-produced turbocharger, the manufacturing cost of the water turbine can be reduced. The impeller 130 may also be made of, for example, an aluminum alloy.

[0027] (Discharge piping) The discharge piping 140 is a pipe that discharges the water flow that has passed through the impeller 130. One end of the discharge piping 140 is connected to the water outlet 122 of the front casing 120A, and the other end is connected to a pipe WP2 or the like that is connected to the discharge port WO of the waterway R mentioned above. Therefore, the water flow that has passed through the impeller 130 is returned to the waterway R, for example, through the discharge piping 140.

[0028] (Shaft) The shaft 150 is a rotating shaft connected to the impeller 130 and rotates in conjunction with the rotation of the impeller 130. The shaft 150 is provided so that its axial direction is aligned with the X direction, and the impeller 130 is attached to the end opposite to the X direction. That is, the shaft 150 connects the impeller 130 and the generator 190, and the rotation of the impeller 130 rotates the rotor of the generator 190. The shaft 150 is fastened to the rotor of the generator 190 by, for example, a coupling 180 which will be described later. In addition, a speed increaser may be provided on the impeller 130 side of the shaft 150 where the coupling 180 is provided, if necessary, to convert the rotational speed transmitted from the impeller 130 at high speed using a planetary gear mechanism or the like, thereby increasing the power generation efficiency of the generator 190. The rotational speed of the shaft 150 may be measured by a rotation sensor.

[0029] (Bearing) The bearing 160 rotatably supports the shaft 150. The bearing 160 may be, for example, a radial bearing that rotates while supporting the vertical load on the shaft 150. As shown in Figure 2, the bearing 160 may include, for example, a first bearing 160A provided near the point where the shaft 150 connects to the impeller 130, a second bearing 160B provided at the end of the central portion of the shaft 150 on the impeller 130 side, and a third bearing 160C provided at the end of the central portion of the shaft 150 on the coupling 180 side.

[0030] (Bearing Casing) The bearing casing 170 is a housing that accommodates the portion of the shaft 150 where the bearing 160 is installed. That is, the bearing casing 170 is installed connected to the generator 190 side of the rear casing 120B. The bearing casing 170 may be made of, for example, stainless steel. The structure of the bearing casing 170 will be described in detail later.

[0031] (Coupling) The coupling 180 is a fastening mechanism that connects the shaft 150 and the generator 190. The coupling 180 may be a disc coupling that generates axial force in the bolt by tightening the nut and transmits torque through frictional force between it and the connected hub, washer, disc, etc. Since torque is transmitted by friction, the disc coupling has no backlash between the drive shaft and the driven shaft, has high torsional rigidity and can be used without lubrication.

[0032] (Generator) The generator 190 converts kinetic energy from the rotation of the rotor into electrical energy. The generator 190 may be, for example, an alternator, which is a generator used in automobiles. An alternator is a permanent magnet synchronous generator in which a coil is the armature and a permanent magnet is the field. In a permanent magnet synchronous generator, one of the coils or permanent magnets is the rotor and the other is the stator, and by moving the distance between the coil and the permanent magnet closer or further away, the magnetic flux density passing through the coil is changed, generating an electric current in the coil by electromagnetic induction and converting kinetic energy into electrical energy. By using a general-purpose alternator for automobiles as the generator 190, the manufacturing cost of the hydroelectric power generation device 100 can be reduced.

[0033] As described above, with the configuration of the hydroelectric power generation device 100, when air is used as the working fluid, the impeller 130 for the turbocharger is reversed by the water flow, and electricity is generated by rotating the generator 190 via the shaft 150 connected to the impeller 130. Therefore, it is possible to provide a hydroelectric power generation device 100 that can generate electricity stably while keeping costs down.

[0034] (Regarding the structure around the impeller) Next, an example of the structure around the impeller 130 according to this disclosure will be explained using Figure 3. Figure 3 is a diagram showing an example of the structure around the impeller according to this disclosure. As shown in Figure 3, a lock nut 10, a thrust ring 20, a ring sleeve 30, and a shaft 150 may be provided around the impeller 130 according to this disclosure. These components will be explained in order below.

[0035] As shown in Figure 3, the impeller 130 may have a shape similar to that of the compressor of the turbocharger. That is, by supplying a water flow from the air outlet side of the turbocharger's compressor, the turbocharger's compressor is rotated in the opposite direction compared to when air is used as the working fluid. This rotates the rotor of the generator 190 connected by the shaft 150, thereby generating electricity.

[0036] The lock nut 10 is a component that fastens the impeller 130 and the shaft 150. The lock nut 10 may be a nut that prevents loosening due to vibration. The lock nut 10 may have an anti-loosening effect that utilizes a wedge, eccentricity, friction with the shaft, etc.

[0037] The thrust ring 20 is a ring-shaped member that receives the thrust load applied to the shaft 150. The thrust ring 20 may be formed by using a bearing alloy on a rounded surface.

[0038] The ring sleeve 30 is a component that connects the shaft 150 and the impeller 130. The ring sleeve 30 is a ring-shaped sleeve that fits into the shaft hole of the impeller 130.

[0039] As shown in Figure 3, when air is used as the working fluid for the turbocharger's impeller 130, air is drawn in from the direction indicated by arrow AI in Figure 3 and discharged in the direction indicated by arrow AO in Figure 3. When used as a water turbine, conversely, water is supplied from the direction indicated by arrow WI in Figure 3 to rotate the impeller 130 and discharge the water flow in the direction indicated by arrow WO in Figure 3. In other words, the turbocharger's impeller 130 is being rotated in the reverse direction.

[0040] (Regarding the structure of the impeller blades) Next, the structure of the blades of the impeller 130 according to the present disclosure will be described using Figures 4A and 4B. Figures 4A and 4B are diagrams showing examples of the structure of the impeller blades according to the present disclosure. Figure 4A is a schematic side view of the impeller 130, and Figure 4B is a schematic front view of the impeller 130. Figure 4B is a schematic diagram showing only a part of the blade portion provided on the impeller 130. As shown in Figure 4A, the impeller 130 according to the present disclosure has a base portion 131 and a blade portion 136.

[0041] (Base) The base 131 is a columnar member whose axial direction is aligned with the X direction. More specifically, in this embodiment, the base 131 has a circular cross-section when viewed from the X direction, and its diameter decreases as it moves away from the X direction. Therefore, the side surface 131a of the base 131 is inclined radially inward of the impeller 130 (base 131) as it moves away from the X direction. Here, radial direction refers to the radial direction when the central axis of the impeller 130 (base 131) is considered as the axial direction.

[0042] (Blade section) The blade section 136 is a wing member provided on the side surface 131a of the base section 131. As shown in Figures 4A and 4B, multiple blade sections 136 are provided on the side surface 131a, extending in the circumferential direction of the base section 131. Here, the circumferential direction refers to the circumferential direction when the central axis of the impeller 130 (base section 131) is considered as the axial direction.

[0043] Hereinafter, the end portion on the X-direction side (the end portion on the side where water flows in) of the blade portion 136 is defined as the end portion 136a, and the end portion on the side opposite to the X direction of the blade portion 136 (the end portion on the side where water flows out) is defined as the end portion 136b. Also, the base end portion on the radially inner side of the blade portion 136 is defined as the lower edge portion 136c, and the tip end portion on the radially outer side of the blade portion 136 is defined as the upper edge portion 136d. That is, in this case, the blade portion 136 has a wing shape that rises upward in the radial direction from the lower edge portion 136c to the upper edge portion 136d, with the lower edge portion 136c connected to the side surface 131a of the base portion 131. Further, the blade portion 136 extends in the direction opposite to the X direction from the end portion 136a to the end portion 136b on the side surface 131a of the base portion 131.

[0044] (Outer diameter side wing angle) As shown in FIG. 4B, the wing angle on the outer diameter side of the blade portion 136 is defined as the outer diameter side wing angle θa. In this case, the outer diameter side wing angle θa is preferably 25° or more and 90° or less, and more preferably 45° or more and 80° or less. By setting the outer diameter side wing angle θa within this range, while improving the power generation efficiency and appropriately generating power, for example, an impeller for a turbocharger can be appropriately diverted, so that the cost can be suppressed. The outer diameter side wing angle θa is the angle formed by the tangent line L1a of the blade portion 136 and the tangent line L2a of the base portion 131 as viewed from the X direction (the axial direction of the impeller 130). The tangent line L1a refers to the tangent line at the location of the end portion 136a on the X-direction side of the lower edge portion 136c of the blade portion 136. The tangent line L2a refers to the tangent line at the intersection of the outer peripheral surface 131b at the end portion on the X-direction side of the base portion 131 with the tangent line L1a.

[0045] (Inner diameter side wing angle) As shown in FIG. 4B, the wing angle on the inner diameter side of the blade part 136 is defined as the inner diameter side wing angle θb. In this case, the inner diameter side wing angle θb may be smaller than the outer diameter side wing angle θa. By setting the inner diameter side wing angle θb within this range, it is possible to suppress the decrease in the outlet area of water and thus suppress the decrease in power generation efficiency. At the same time, for example, an impeller for a turbocharger can be appropriately diverted, so that the cost can be suppressed. The inner diameter side wing angle θb is the angle formed by the tangent line L1b of the blade part 136 and the tangent line L2b of the base part 131 as viewed from the X direction (axial direction of the impeller 130). The tangent line L1b refers to the tangent line at the position of the end part 136b on the side opposite to the X direction of the lower edge part 136c of the blade part 136. The tangent line L2b refers to the tangent line at the intersection point of the outer peripheral surface 131b of the base part 131 and the tangent line L1b.

[0046] (Opening area) Let the inlet area A1 indicating the size of the water inlet of the impeller 130 be expressed by the following formula (1), and let the outlet area A2 indicating the size of the water outlet of the impeller 130 be expressed by the following formula (2). The inlet area A1 and the outlet area A2 can be said to be index values geometrically indicating the sizes of the water inlet and outlet.

[0047] A1 = π × D1 × F1... (1) A2 = π × D2 ２ / 4... (2)

[0048] As shown in FIG. 4A, D1 refers to the outer diameter of the impeller 130 at the end on the X direction side (the diameter of the circle connecting the end parts 136a of the respective blade parts 136), and D2 refers to the outer diameter of the impeller 130 at the end on the side opposite to the X direction (the diameter of the circle connecting the end parts 136b of the respective blade parts 136 (main blades 132 described later) that protrude the farthest to the side opposite to the X direction). Also, F1 refers to the height of the blade part 136 at the end part 136a (the length from the lower edge part 136c to the upper edge part 136d at the end part 136a).

[0049] In this case, the inlet area A1 may be smaller than the outlet area A2. By setting the relationship between the inlet area A1 and the outlet area A2 in this way, it is possible to suppress the decrease in the outlet area of water and thus suppress the decrease in power generation efficiency. At the same time, for example, an impeller for a turbocharger can be appropriately diverted, so that the cost can be suppressed.

[0050] The inlet area B1, which indicates the size of the water inlet of the impeller 130, is given by the following equation (3), and the outlet area B2, which indicates the size of the water outlet of the impeller 130, is given by the following equation (4). The inlet area B1 and outlet area B2 can be said to be index values ​​that show the size of the water inlet and outlet, taking into account the width of the blade portion 136.

[0051] B1=S1×F1×Z1...(3) B2=S2×F2×Z1...(4)

[0052] As shown in Figure 4A, F1 refers to the height of the blade portion 136 at end 136a (the length from the lower edge 136c to the upper edge 136d at end 136a), and F2 refers to the height of the blade portion 136 at end 136b (the length from the lower edge 136c to the upper edge 136d at end 136b). Also, as shown in Figure 4B, S1 refers to the distance between adjacent blade portions 136 at end 136a, and S2 refers to the distance between adjacent blade portions 136 at end 136b. Furthermore, Z1 refers to the total number of blade portions 136.

[0053] In this case, the inlet area B1 can be smaller than the outlet area B2. This relationship between the inlet area B1 and the outlet area B2 prevents the water outlet area from becoming too small, thereby suppressing a decrease in power generation efficiency, while also allowing for the appropriate reuse of components such as turbocharger impellers, thus reducing costs.

[0054] (Outer diameter) It is preferable that the outer diameter D1 of the impeller 130 on the water inlet side (X direction side) is larger than the outer diameter D2 of the water outlet side (opposite to the X direction). It is also preferable that the outer diameter (the diameter of the circle connecting the upper edges 136d of the blade portion 136) of the impeller 130 gradually decreases as it moves toward the opposite side of the X direction. This suppresses a decrease in power generation efficiency and allows for the appropriate reuse of an impeller, for example, from a turbocharger, thereby reducing costs.

[0055] (Main blades and splitter blades) The blade section 136 preferably comprises a plurality of main blades 132 and a splitter blade 134 provided between the main blades 132 which are adjacent to each other. The splitter blade 134 is shorter in length than the main blades 132. The splitter blade 134 is formed from the middle of the flow path formed between the main blades 132 to the water inlet. In other words, the main blades 132 and the splitter blade 134 have the water inlet end 136a (first end) at the same position in the X direction (axial direction of the impeller 130), and the splitter blade 134 has the water outlet end 136b (second end) at a position in the X direction that is closer to the X direction (towards end 136a) than the position of the end 136b of the main blade 132. In other words, the splitter blade 134 has its end portion 136b positioned further back than the main blade 132, dividing the airflow path formed between the main blade 132 and the adjacent main blade 132. By providing the splitter blade 134, the throat area can be increased.

[0056] Next, the relationship between the blade lengths of the main blade 132 and the splitter blade 134 of the impeller according to this disclosure will be explained using Figure 5. Figure 5 is a diagram showing the relationship between the blade lengths of the main blade and the splitter blade of the impeller according to this disclosure. As shown in configuration C1 of Figure 5, the splitter blade 134 is shorter in length than the main blade 132, so if the length of the main blade 132 is Ll and the length of the splitter blade 134 is Ls, then L1 > Ls. Note that the length is the length from end 136a to end 136b, as described above.

[0057] Furthermore, as shown in configuration C2 of Figure 5, the impeller 130 may be configured such that the end portion 136b of the main blade 132 is cut off, for example, compared to an impeller for a turbocharger. This allows the length of the main blade 132 to be shortened, thereby increasing the outlet area and further improving power generation efficiency. In this case, as shown in configuration C2 of Figure 5, it is preferable that the length L of the main blade 132 after cutting satisfies Ll > L > Ls. The cutting range of the main blade 132 can be either the range extending from the upper edge 136d to the lower edge 136c (complete cutting) or the range from the upper edge 136d to the area between the upper edge 136d and the lower edge 136c (cutting only on the tip side).

[0058] Specifically, using Figure 6, a first example of the cutting range of the main blade 132 of the impeller 130 according to this disclosure will be described. Figure 6 is a diagram showing a first example of the cutting range of the main blade of the impeller according to this disclosure. As shown by the hatching in Figure 6, the portion of the main blade 132 that overlaps with the splitter blade 134 on the water flow outlet side may be completely cut off. That is, the blade length of the main blade 132 may be set to be approximately the same as the blade length of the splitter blade 134. Note that in Figure 6, only the cutting range of one main blade 132 is shown as an example, but the other main blades 132 may be cut off in the same way. This makes it possible to widen the outlet area of ​​the impeller 130.

[0059] Furthermore, the tip side (front end) of the main blade 132 may be cut off. Specifically, a second example of the cutting range of the main blade 132 of the impeller 130 according to this disclosure will be explained using Figure 7. Figure 7 is a diagram showing a second example of the cutting range of the main blade of the impeller according to this disclosure. As shown by the hatching in Figure 7, the tip side of the part of the main blade 132 that overlaps with the splitter blade 134 on the water flow outlet side, in other words, the opposite side of the root of the main blade 132 may be cut off. Note that in Figure 7, only the cutting range of one main blade 132 is shown as an example, but other main blades 132 may be cut off in the same way. If only the tip side of the main blade 132 is cut off, the water flow toward the axis side of the impeller 130 is more easily maintained, so the performance at partial load, which is an operation other than the design point of the impeller 130, is less likely to be adversely affected. Note that at partial load, the water flow tends to be biased toward the outer circumference, which may cause a decrease in efficiency due to leakage flow at the blade tip, but this can be suppressed.

[0060] As a result, although the blade angle of the main blade 132 on the water flow outlet side of the turbocharger impeller 130 is small, the outlet area of ​​the impeller 130 can be increased by cutting off the portion of the main blade 132 that overlaps with the splitter blade 134. This makes it possible to operate in regions with high water flow rates and high power generation output. In other words, the power generation output per unit volume of the hydroelectric power generation device 100 can be increased.

[0061] (Effects) The hydroelectric power generation device 100 according to this embodiment is equipped with an impeller 130 having the structure described above. Therefore, according to this embodiment, costs can be reduced by reusing the impeller for the turbocharger compressor while generating power appropriately.

[0062] (Regarding the placement of the flywheel) The hydroelectric power generation device 100 may have a flywheel 195. Figure 8 is a diagram showing an example of the placement of the flywheel in the hydroelectric power generation device according to the present disclosure. As shown in Figure 8, the flywheel 195 may be provided, for example, at both ends of the shaft 150. More specifically, the flywheel 195 may be provided on the central side of the shaft 150 where the coupling 180 of the shaft 150 is provided, between the first bearing 160A and the second bearing 160B of the shaft 150.

[0063] The flywheel 195 is an inertial body through which the axis of rotation passes at the center of gravity, and adds a moment of inertia to the axis of rotation. By adding a moment of inertia to the shaft 150 with the flywheel 195, even if the rotational speed of the shaft 150 changes significantly in a short period of time, the change in the rotational speed of the shaft 150 can be made gradual.

[0064] Furthermore, the turbocharger's impeller 130 is designed with a very small moment of inertia to improve responsiveness. Therefore, when the turbocharger's compressor is used as a water turbine, the rotational speed will fluctuate significantly in response to load changes on the water turbine, potentially preventing stable operation under normal conditions. In addition, if the water flow supplied to the impeller 130 is cut off in the event of a malfunction, the rotational speed of the impeller 130 will increase significantly, potentially damaging the impeller 130.

[0065] As described above, by providing the flywheel 195, an inertia moment can be added to the rotating shaft, which suppresses significant fluctuations in rotational speed when the water flow supply to the hydroelectric power generator 100 is interrupted. Therefore, even when the water flow supplied to the impeller 130 is interrupted at high speed, the increase in the rotational speed of the shaft 150 can be suppressed.

[0066] Furthermore, by attaching the flywheel 195 and increasing the moment of inertia of the shaft 150, short-period fluctuations in rotational speed can be suppressed. In addition, by installing the flywheel 195 on the outside side rather than inside the casing 120 in which the impeller 130 is housed, disc friction losses caused by the rotation of the flywheel 195 in water can be reduced.

[0067] (Regarding control of water supply) The hydroelectric power generation device 100 may have a configuration that allows control of the amount of water supplied to the impeller 130. Figure 9 is a diagram showing an example of the operation of the hydroelectric power generation device according to the present disclosure during normal operation and load shedding. Figure 9 schematically shows the relationship between the impeller 130, the supply pipe 110, the bypass pipe 115, the discharge pipe 140, and other components of the hydroelectric power generation device 100 according to the present disclosure.

[0068] The supply piping 110 is provided with an inlet solenoid valve 111 on the side before it connects to the water inlet 121 of the front casing 120A housing the impeller 130. The inlet solenoid valve 111 may be a solenoid valve, which includes a solenoid section comprising a coil, a yoke, a movable core, and a fixed core, and a valve section comprising a disc that opens and closes the flow path and an orifice that serves as a valve seat. When current is passed through the coil, the fixed core and the movable core are magnetized, and the magnetic force between them drives the movable core, opening and closing the orifice of the valve section and controlling the fluid flow. In other words, the amount of water supplied to the impeller 130 can be controlled by controlling the inlet solenoid valve 111 provided in the supply piping 110. However, a sudden change in the water volume would cause an impact on the valve section, so it is necessary to suppress a sudden increase in the water volume.

[0069] The bypass piping 115 is provided with a bypass solenoid valve 112 and a throttling mechanism 113. The bypass solenoid valve 112 may be a pressure reducing valve, and adjusts the pressure on the outlet side, i.e., the secondary side, by balancing the upward and downward forces of the force of an adjustment spring and the force of the secondary pressure on the outlet side, via a diaphragm provided at the boundary between the inlet side and the outlet side of the water flow.

[0070] Furthermore, the bypass pipe 115 may be designed such that, after the water flow has passed through it, a pressure reduction equivalent to the pressure loss when the water flow passed through the impeller 130 occurs. Specifically, the diameter of the bypass pipe 115 may be set to be smaller than the diameter of the supply pipe 110. This increases the pipe friction loss when the water flow passes through the bypass pipe 115, thus increasing the pressure loss. By reducing the diameter of the bypass pipe 115, the amount of pressure reduction due to the bypass solenoid valve 112 and the throttling mechanism 113 can be suppressed, thereby reducing costs.

[0071] The throttling mechanism 113 may be implemented by a concentric orifice or a porous orifice. A concentric orifice is a disc-shaped orifice plate formed so that the throttling hole is located at the center of the pipe, while a porous orifice is a disc-shaped orifice plate with multiple throttling holes formed therein. By passing fluid through the throttling holes, the pressure of the fluid on the upstream and downstream sides is adjusted. Specifically, the throttling mechanism 113 reduces the pressure of the water flow on the downstream side by causing pressure loss through the orifice plate.

[0072] The discharge pipe 140 is connected to one end of the bypass pipe 115. That is, the water flow that passes through the bypass pipe 115 is supplied to the supply pipe 110. As described above, since the difference in pressure loss between the water flow passing through the impeller 130 and the water flow passing through the bypass pipe 115 is eliminated, it is possible to prevent the pressure of the water flow returning from the bypass pipe 115 to the supply pipe 110 from becoming excessive when the water flow passes through the bypass pipe 115. Therefore, the impact on the supply pipe 110 caused by the water flow from the bypass pipe 115 can be reduced.

[0073] Furthermore, the inlet solenoid valve 111 and the bypass solenoid valve 112 described above may be connected to a control device that controls the power supplied to the coil.

[0074] The control device includes a control unit equipped with a CPU (Central Processing Unit) and an MPU (Micro Processing Unit), a storage unit which includes a main memory device implemented by semiconductor memory elements such as RAM (Random Access Memory), ROM (Read Only Memory), and flash memory, and an auxiliary storage device implemented by a hard disk or SSD (Solid State Drive), and executes various processes such as controlling the opening and closing of the inlet solenoid valve 111 and the bypass solenoid valve 112 by executing a program stored in the storage unit.

[0075] As described above, with this configuration, when the inlet solenoid valve 111 is shut off, the amount of water that reaches the inlet solenoid valve 111 of the supply pipe 110 can be reduced by diverting the water flow to the bypass pipe 115. Therefore, by providing the bypass pipe 115 to divert water when the valve is shut off, the flow rate fluctuation can be reduced, and the intensity of the impact caused by the water flow at the inlet solenoid valve 111 can be suppressed. In addition, since the difference in pressure loss between the water flow passing through the impeller 130 and the water flow passing through the bypass pipe 115 is eliminated, the impact when the water flow returns from the bypass pipe 115 to the supply pipe 110 after passing through the bypass pipe 115 can be suppressed.

[0076] (Method for shutting off the water flow supply) Next, the method for shutting off the water flow supply to the impeller 130 of the hydroelectric power generation apparatus according to this disclosure will be explained using Figure 9 described above.

[0077] First, the inlet solenoid valve 111 installed in the supply pipe 110 is closed. Next, the bypass solenoid valve 112 installed in the bypass pipe 115 is opened. As a result, the water flow that was flowing through the supply pipe 110 flows into the bypass pipe 115 and out into the discharge pipe 140 connected to the end of the bypass pipe 115. Therefore, even if the inlet solenoid valve 111 of the supply pipe 110 is shut off, the amount of water that hits the valve part of the inlet solenoid valve 111 can be reduced.

[0078] Therefore, the impact on the valve section of the inlet solenoid valve 111 caused by the sudden fluctuation in water flow rate when the water flow to the impeller 130 is cut off can be mitigated. Also, as described above, since the pressure loss in the bypass piping 115 is about the same as the pressure loss when passing through the impeller 130, the pressure of the water flow after passing through the impeller 130 is about the same as the pressure of the water flow after passing through the bypass piping 115. As a result, the impact on the supply piping 110 caused by the water flow supplied from the bypass piping 115 to the supply piping 110 can be suppressed.

[0079] (Regarding the placement of shims) The hydroelectric power generation device 100 may be equipped with shims 135. Figure 10 is a diagram showing an example of the placement of shims in the hydroelectric power generation device according to the present disclosure. As shown in Figure 10, the hydroelectric power generation device 100 according to the present disclosure has shims 135 provided between the impeller 130 and the shaft 150. This configuration will be described below.

[0080] The shim 135 is a component used for adjusting the height between it and the generator 190, adjusting the gap at the end of the shaft 150, and so on. The shim 135 may be a shim ring, which is a ring-shaped spacer, or a laminate shim whose plate thickness can be easily changed. From the viewpoint of corrosion prevention, the shim 135 may be made of iron, hardened steel, stainless steel, brass, copper, aluminum, or the like.

[0081] When the impeller 130 and the shaft 150 are integrated into a single structure, or when the impeller 130 and the casing 120 are assembled with extremely precise dimensional tolerances, overall adjustment machining is required to control the dimensions in the radial thrust direction (X-axis direction). However, as described above, by adopting a configuration in which a shim 135 is placed between the impeller 130 and the shaft 150, overall adjustment machining can be eliminated.

[0082] As a result, by inserting a shim 135 between the impeller 130 and the shaft 150, if dimensional adjustments are needed during assembly, rework is unnecessary, and dimensional adjustments can be made simply by adjusting the thickness of the shim 135.

[0083] (Regarding the application locations of the insulating coating) In the hydroelectric power generation device 100, it is preferable to make the parts that come into contact with water insulated, except for the impeller 130 and the front casing 131A. For example, it is preferable to form an insulating coating on the parts of the parts other than the impeller 130 and the front casing 131A that come into contact with water. Figure 11 is a diagram showing an example of the application locations of the insulating coating in the hydroelectric power generation device according to this disclosure. For example, the insulating coating may be applied to the parts indicated by the arrows in Figure 11. Note that the parts indicated by the arrows in Figure 11 are just examples and do not limit the parts to which the insulating coating is applied. The parts to which the insulating coating is applied can be said to be parts that come into contact with water, that is, wetted parts.

[0084] Specifically, when the impeller 130 is operated in reverse for hydroelectric power generation, there are parts that come into contact with water, so it is necessary to prevent corrosion. For this reason, the wetted parts of the rear casing 120B, the shaft 150, and the discharge piping 140 may be coated with zinc plating or resin for insulation.

[0085] The insulating coating may be made of zinc plating, resin, or engineering plastics such as polyvinyl chloride (PVC), polycarbonate, CFRP (Carbon Fiber Reinforced Plastics), or PEEK (Polyetheretherketone). This prevents corrosion of the wetted parts of the rear casing 120B, the shaft 150, and the discharge piping 140.

[0086] Alternatively, an insulating sleeve may be sandwiched between the stainless steel shaft 150 and the aluminum alloy impeller 130. This prevents corrosion of the aluminum alloy impeller 130 by blocking electrical conductivity between the aluminum alloy impeller 130 and the stainless steel shaft 150.

[0087] Furthermore, an insulating washer may be installed between the lock nut 10 that tightens the impeller 130 and the impeller 130. This prevents corrosion of the aluminum alloy impeller 130 by blocking electrical conductivity between the aluminum alloy impeller 130 and the stainless steel lock nut 10.

[0088] An insulating washer may be placed between the rear casing 120B and the front casing 120A and fastened with insulating bolts. This prevents corrosion of the front casing 120A, which is made of aluminum alloy, by blocking electrical conductivity between the front casing 120A, which is made of aluminum alloy, and the rear casing 120B, which is made of stainless steel.

[0089] (Regarding the structure of the bearing casing) The bearing casing 170 of the hydroelectric power generation device 100 may be composed of one component, but it is preferable that it be composed of two or more components. Figure 12 is a diagram showing an example of how the bearing casing of the hydroelectric power generation device according to the present disclosure is divided. As shown in Figure 12, the bearing casing 170 of this example comprises a first bearing casing 170A and a second bearing casing 170B. That is, the bearing casing 170 has a structure that can be divided into a shaft seal side and a bearing side.

[0090] The first bearing casing 170A is a container that houses the portion of the shaft 150 where the shaft seal is provided. The first bearing casing 170A contains the first bearing 160A and the shaft seal. The shaft seal may be a gland packing or a mechanical seal.

[0091] The second bearing casing 170B is a container that houses the area where the second bearing 160B and the third bearing 160C of the shaft 150 are installed. In other words, the second bearing 160B and the third bearing 160C that support the shaft 150 are provided inside the second bearing casing 170B.

[0092] If the bearing casing 170 were a single, integrated unit, it would be necessary to house the shaft seal, bearing 160, sleeve, etc., within it. In contrast, by adopting a segmented structure for the bearing casing 170, the bearing 160 can be installed from either end of the second bearing casing 170B. Furthermore, the reference point for centering the shaft 150 can be set on the bearing casing 170, thereby reducing the centering man-hours.

[0093] Furthermore, by using a bolted connection structure between the first bearing casing 170A and the second bearing casing 170B, any misalignment between the bearing casing 170 and the generator 190 or impeller 130 can be adjusted using the bolt's clearance. In addition, by dividing the bearing casing 170, it becomes possible to eliminate the need to incorporate custom-made parts.

[0094] For example, a shaft seal such as a gland packing to prevent water from flowing from the casing 120 to the bearing casing 170, and the bearing 160 may be installed separately directly on the bearing casing 170. However, if the bearing casing 170 is not divided, it would be necessary to lengthen the shaft 150 or to make all the parts special. By dividing the bearing casing 170 into a first bearing casing 170A and a second bearing casing 170B, these measures become unnecessary, and costs can be reduced.

[0095] (Configuration and Effects) The hydroelectric power generation device 100 according to the first embodiment includes an impeller 130 having blades 136 with an outer diameter side blade angle of 25° or more and 90° or less, a shaft 150 connected to the impeller 130 and rotating in conjunction with the rotation of the impeller 130, and a generator 190 connected to the shaft 150 and converting the kinetic energy due to the rotation of the shaft 150 into electrical energy.

[0096] This configuration allows for an increase in power output per unit volume. Furthermore, by reversing the rotation of the compressor of a mass-produced turbocharger to generate power, the manufacturing cost of the hydroelectric power generation device 100 can be reduced. This also allows for a reduction in the cost per unit output. Therefore, it is possible to provide a hydroelectric power generation device 100 that can generate power efficiently while keeping costs down.

[0097] The hydroelectric power generation apparatus 100 according to the second embodiment is the same as the hydroelectric power generation apparatus 100 according to the first embodiment, wherein the blade portion 136 of the impeller 130 has a plurality of main blades 132 and splitter blades 134 that are arranged between the main blades 132 and are shorter than the main blades 132.

[0098] This configuration allows for increased power output per unit volume, enabling efficient power generation while keeping costs down.

[0099] The hydroelectric power generation apparatus 100 according to the third embodiment is the same as the hydroelectric power generation apparatus 100 according to the second embodiment, wherein the main blade 132 and the splitter blade 134 have the same position at the first end (end 136a) on the water inlet side in the axial direction (X direction) of the impeller 130. The splitter blade 134 has the second end (end 136b) on the water outlet side positioned closer to the first end than the second end (end 136b) of the main blade 132 in the axial direction (X direction) of the impeller.

[0100] This configuration allows for a larger outlet area, thereby increasing power output per unit volume. Therefore, it is possible to generate power efficiently while keeping costs down.

[0101] The hydroelectric power generation apparatus 100 according to the fourth embodiment is a hydroelectric power generation apparatus 100 according to any of the first to third embodiments, wherein the impeller 130 has an outer diameter on the water inlet side that is larger than the outer diameter on the water outlet side.

[0102] This configuration allows for efficient power generation while keeping costs more effectively under control.

[0103] The hydroelectric power generation device 100 according to the fifth embodiment is a hydroelectric power generation device 100 according to any of the first to fourth embodiments, further comprising a flywheel 195 provided on the shaft 150 and adding an inertia moment to the rotational motion of the shaft 150.

[0104] This configuration makes it possible to suppress significant fluctuations in the rotational speed of the hydroelectric power generation device 100 when the load is shedding. Therefore, even when the water flow supplied to the impeller 130 is cut off at high speed, the increase in the rotational speed of the shaft 150 can be suppressed. In addition, the moment of inertia of the shaft 150 can be increased, and short-period fluctuations in rotational speed can be suppressed. Thus, it is possible to provide a hydroelectric power generation device 100 that can increase the power output per unit volume and operate stably while keeping costs down.

[0105] The hydroelectric power generation apparatus 100 according to the sixth embodiment is a hydroelectric power generation apparatus 100 according to any of the first to fifth embodiments, further comprising: a supply pipe 110 for supplying water to an impeller 130; a discharge pipe 140 for discharging water that has passed through the impeller 130; a front casing 120A that houses the side of the impeller 130 on which the blade portion 136 is provided; and a rear casing 120B connected to the front casing 120A and provided on the back side of the impeller 130.

[0106] This configuration allows for efficient power generation while keeping costs appropriately low.

[0107] The hydroelectric power generation apparatus 100 according to the seventh embodiment is the hydroelectric power generation apparatus 100 according to the sixth embodiment, further comprising: a bypass pipe 115 having one end connected to a supply pipe 110 and the other end connected to a discharge pipe 140; a bypass solenoid valve 112 provided in the bypass pipe 115 for controlling the amount of water passing through the bypass pipe 115; a throttling mechanism 113 provided on the downstream side of the water flow at the location where the bypass solenoid valve 112 is provided in the bypass pipe 115 for adjusting the pressure before and after the passage of the water flow; and an inlet solenoid valve 111 provided in the supply pipe 110 for controlling the amount of water to the impeller 130.

[0108] This configuration makes it possible to mitigate the impact on the valve section of the inlet solenoid valve 111 caused by sudden fluctuations in water flow when the water flow to the impeller 130 is cut off. It also reduces the impact on the supply pipe 110 caused by the water flow supplied from the bypass pipe 115 to the supply pipe 110. Therefore, it is possible to provide a hydroelectric power generation device 100 that can increase the power output per unit volume and operate stably while keeping costs down.

[0109] The hydroelectric power generation apparatus 100 according to the eighth embodiment is the hydroelectric power generation apparatus 100 according to the sixth or seventh embodiment, and comprises an insulating coating provided on the wetted parts of the rear casing 120B, shaft 150, and discharge piping 140, an insulating sleeve provided between the shaft 150 and the impeller 130, an insulating washer provided between the nut that fastens the impeller 130 and the impeller 130, an insulating washer provided between the front casing 120A and the rear casing 120B, and insulating bolts that fasten the front casing 120A and the rear casing 120B.

[0110] This configuration prevents corrosion of the aluminum alloy component by blocking electrical conductivity between the aluminum alloy component and the stainless steel component. Therefore, it is possible to provide a hydroelectric power generation device 100 that can increase power output per unit volume and operate stably while keeping costs down.

[0111] A power generation method using a hydroelectric power generation device 100 according to the ninth embodiment is a power generation method using a hydroelectric power generation device 100 according to any of the first to eighth embodiments, and includes the steps of supplying water to an impeller 130 and rotating a shaft 150 in conjunction with the rotation of the impeller 130, thereby rotating the rotor of a generator 190 connected to the shaft 150.

[0112] This configuration allows for an increase in power output per unit volume. Furthermore, it enables a reduction in cost per unit output. Therefore, it is possible to provide a power generation method using a hydroelectric power generation device 100 that can increase power output per unit volume and operate stably while keeping costs down.

[0113] Although embodiments of the present disclosure have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above.

[0114] 1 Container 10 Lock Nut 20 Thrust Ring 30 Ring Sleeve 100 Hydroelectric Power Plant 110 Supply Piping 111 Inlet Solenoid Valve 112 Bypass Solenoid Valve 113 Throttle Mechanism 115 Bypass Piping 120 Casing 120A Front Casing 120B Rear Casing 130 Impeller 131 Base 132 Main Blade 134 Splitter Blade 135 Shim 136 Blade Section 140 Discharge Piping 150 Shaft 160 Bearing 160A First Bearing 160B Second Bearing 160C Third Bearing 180 Coupling 190 Generator 195 Flywheel

Claims

1. A hydroelectric power generation device comprising: an impeller having blades with an outer diameter side blade angle of 25° or more and 90° or less; a shaft connected to the impeller and rotating in conjunction with the rotation of the impeller; and a generator connected to the shaft and converting the kinetic energy due to the rotation of the shaft into electrical energy.

2. The hydroelectric power generation apparatus according to claim 1, wherein the impeller blades have a plurality of main blades and splitter blades disposed between the main blades and shorter than the main blades.

3. The hydroelectric power generation apparatus according to claim 2, wherein the first end of the main blade and the splitter blade on the water inlet side is located at the same position in the axial direction of the impeller, and the second end of the splitter blade on the water outlet side is located closer to the first end than the second end of the main blade in the axial direction of the impeller.

4. The impeller has an outer diameter on the water inlet side that is larger than the outer diameter on the water outlet side, according to any one of claims 1 to 3.

5. A hydroelectric power generation apparatus according to any one of claims 1 to 3, further comprising a flywheel provided on the shaft for adding a moment of inertia to the rotational motion of the shaft.

6. A hydroelectric power generation apparatus according to any one of claims 1 to 3, further comprising: a supply pipe for supplying water to the impeller; a discharge pipe for discharging water that has passed through the impeller; a front casing for housing the side of the impeller on which the blade portion is provided; and a rear casing connected to the front casing and provided on the back side of the impeller.

7. The hydroelectric power generation apparatus according to claim 6, further comprising: a bypass pipe having one end connected to the supply pipe and the other end connected to the discharge pipe; a bypass solenoid valve provided in the bypass pipe for controlling the amount of water passing through the bypass pipe; a throttling mechanism provided on the downstream side of the water flow at the location where the bypass solenoid valve is provided in the bypass pipe for adjusting the pressure before and after the passage of the water flow; and an inlet solenoid valve provided in the supply pipe for controlling the amount of water to the impeller.

8. A hydroelectric power generation apparatus according to claim 6, comprising: an insulating coating provided on the wetted parts of the rear casing, the shaft, and the discharge piping; an insulating sleeve provided between the shaft and the impeller; an insulating washer provided between a nut for tightening the impeller and the impeller; an insulating washer provided between the rear casing and the front casing; and insulating bolts for fastening the rear casing and the front casing.

9. A method for generating electricity using a hydroelectric power generation apparatus according to any one of claims 1 to 3, comprising the steps of: supplying water to the impeller; and rotating the shaft in conjunction with the rotation of the impeller, thereby rotating the rotor of the generator connected to the shaft.

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