JP2024062090A - Tiltable backing plate type conveyor water turbine for tidal power generation - Google Patents

Abstract

To provide a water turbine that can generate power highly efficiently at low cost from a tidal current of a low velocity.SOLUTION: A tiltable backing plate type conveyor water turbine for tidal power generation takes tidal currents of a low velocity from a large-bore funnel-like water inlet and collectively leads the tidal currents of which speed is increased when the tidal currents pass through the funnel-like water inlet to a backing plate fitted to a conveyor to recover kinetic energy of the tidal currents as pressure energy, and transmits the pressure energy to a power generator for rotation energy of a spindle via a belt and a pulley or a chain and a sprocket, thereby readily generating power at low cost.SELECTED DRAWING: Figure 2

Description

The present invention relates to a highly efficient conveyor-type water turbine device for small-scale tidal power generation.

In order to realize a decarbonized society, it is desirable to increase the amount of electricity generated using natural energy, but there are few suitable locations for wind power generation in Japan, and there is also little room for the construction of large-scale hydroelectric power generation facilities using rivers. Therefore, it is hoped that electricity can be generated by utilizing marine energy, taking advantage of the characteristics of being an island nation, but unfortunately, the reality is that there are few locations with large tidal differences that are suitable for tidal power generation using the potential energy of seawater. Therefore, it is hoped that tidal power generation will be put into practical use in areas suitable for fast currents, mainly in the Seto Inland Sea and Kyushu region.
The characteristics of tidal currents are that changes in tidal motion are easy to predict, and that the direction of the current periodically changes by almost 180 degrees due to the ebb and flow of the tides. In addition, the motion of water particles below the surface attenuates depending on the depth of the water, and at a depth of half the wavelength, the motion of water particles is about 4% of that at the surface, so it can be considered that there is no effect from waves, and since the wavelength of wind waves commonly seen on the sea is several tens of meters, stable power generation is possible even in coastal areas where the water depth is relatively shallow, with almost no effect from waves.
Therefore, if a power generation device suitable for small-scale tidal current power generation that can generate electricity efficiently even with slow currents could be developed, then by installing a large number of such facilities in shallow waters, it would be possible to generate electricity steadily and at low cost nationwide, since Japan has a long coastline and the diversion times vary from region to region.
In Japan, where most of the major electricity consumption areas, such as urban and industrial regions, are concentrated along the coast, the construction of a network of small-scale tidal power generation facilities that can connect power generation facilities with electricity consumption areas over short distances is thought to be an effective means of solving social issues, not only from the perspective of realizing a decarbonized society, but also from the perspective of reducing social infrastructure costs and ensuring economic security.
In light of the above situation, there is a need for the development of inexpensive, highly efficient power-generating hydroelectric turbines for use in the slow-flowing tidal currents along the coast; however, the horizontal-axis propeller hydroelectric turbines commonly used for tidal power generation have low generating efficiency at low flow speeds, a complex mechanism, and high total generating costs.

In order to accommodate the fact that the direction of the tidal current changes periodically by approximately 180 degrees, horizontal-axis propeller turbines require the addition of a mechanism to rotate the turbine body by 180 degrees, and the manufacturing costs of the turbine body are high due to the complexity of the mechanism.

A propeller turbine is a reaction type turbine that uses the reaction force of the water flow received by the propeller to rotate the rotating shaft. In order to increase the amount of electricity generated, the propeller diameter needs to be increased so that more water flow can be received by the propeller. As the water thrust acting on the bearing section is also very large, the turbine structure and the pillars that secure the turbine need to be strong enough to withstand the strong water thrust, resulting in high costs.

Counter-rotating propeller turbines have been developed in an attempt to increase the generating efficiency of horizontal-axis propeller turbines, but while the total area of the propellers receiving the water flow is up to twice as large, losses due to turbulence generated between adjacent propellers must be taken into consideration, and the structure of not only the turbine section but also the generator section becomes complex, making it insufficient to reduce the total generating costs.

As a type of water turbine other than horizontal-axis propeller turbines, conveyor turbines have been devised for use in low-head waterways. However, conveyor turbines that use the flowing water of low-head waterways are based on the premise that multiple receiving plates protruding from a conveyor installed above the water surface receive the kinetic energy of the flowing water in a certain direction, rotate a sprocket or pulley via a conveyor chain or endless belt connected to the receiving plates, and generate electricity using the rotational force. They are not designed to use the conveyor body submerged in water to reduce the effects of waves, or to generate electricity in response to forward and reverse tidal currents. In addition, in the case of hydroelectric power generation using head, the flow speed is almost constant, so it is only necessary to pay attention to fluctuations in the amount of power generated due to changes in the water volume, but in the case of tidal power generation, the flow speed constantly changes due to tidal phenomena, so the challenge is how to capture as much kinetic energy as possible to ensure power generation even when the flow speed is low.

Conveyor water wheel JP2003-129932A

The present invention aims to provide a water turbine that can generate electricity efficiently and at low cost from low-velocity tidal currents.

The main feature of this invention is that it takes advantage of the large volume of water flow that is characteristic of tidal currents, takes in large volumes of tidal currents through a funnel-shaped intake and collects them at the conveyor receiving plate, maximizing the total pressure energy received by multiple conveyor receiving plates arranged in a vertical row, thereby increasing power generation efficiency.

The outer frame of the conveyor-type water turbine of the present invention has a straight tubular shape and is installed horizontally to the direction of the tidal flow, which has the advantage that it can generate electricity efficiently and continuously even when the direction of the tidal flow changes by almost 180 degrees between high tide and low tide.

Furthermore, there are funnel-shaped intake/suction pipes equipped with tilting shutters at both ends of the conveyor frame. During intake operation, the upstream shutter is closed by the pressure energy of the tidal current, and the large amount of intake water is directed to the receiving plate section on the inlet side of the forward-rotating conveyor, causing the receiving plate to stand up. Even a slow-flowing tidal current is accelerated as it passes through the intake, making it possible to generate electricity. As a result, there are more suitable locations for power generation, and the generators can be operated for longer hours, which is expected to increase the total amount of power generated.

The inner frame inside the outer frame supports the conveyor body and blocks the flow of tidal currents between the carrying conveyor and the return conveyor, creating an independent waterway. This allows the kinetic energy of the taken-in tidal current to be concentrated and guided to the receiving plate of the carrying conveyor, allowing it to be efficiently recovered as pressure energy.

In addition, when water is passing through, the downstream shutter is open, and the unused kinetic energy of the tidal current released from the conveyor is discharged through an inverted funnel-shaped suction pipe, which allows the water to be recovered as a pressure difference, thereby increasing power generation efficiency.

Furthermore, by gradually reducing the frame cross-sectional area of the conveyor storage section from the upstream section to the downstream section along the flow direction of the tidal current, negative pressure can be generated on the back surfaces of multiple receiving plate sections, maximizing the pressure energy that can be recovered from the tidal current.

In addition, by making the receiving plate reversible, the projected cross-sectional area of the receiving plate when it returns toward the intake port can be reduced, thereby reducing the water resistance, thereby maximizing the pressure energy that the conveyor turbine recovers from the tidal current.

The pressure energy recovered from the tide by the conveyor turbine's backing plate is transmitted to the generator as rotational energy via a chain and sprocket or belt and pulley.

FIG. 1 is a block diagram of an apparatus according to the present invention. This diagram shows the position of the receiving plate and shutter depending on the direction of the tidal current. This is a three-view drawing of the water intake/suction pipe and the outer frame connected together.

Figure 1 is a diagram of the device according to the present invention, showing the relative positions of the conveyor outer frame top plate, conveyor section, conveyor inner frame section, conveyor outer frame section, water intake/suction pipe, and stand, as well as the main components.

Figure 2 shows the position of the receiving plate and shutter depending on the direction of the tidal current. It also shows that the direction of rotation of the conveyor main shaft does not change even if the direction of the tidal current changes by approximately 180 degrees, and that the conveyor receiving plate rises up due to the pressure energy of the concentrated tidal current.

Figure 3 is a three-sided view of the outer frame of the device of the present invention, showing the shape for taking in more of the tidal current and directing it to the conveyor receiving plate. The cross-sectional area of the intake port, the projected cross-sectional area of the receiving plate when standing and lying down, and the shutter mounting angle, etc., are to be determined arbitrarily, taking into consideration the constraints imposed by the location where the device of the present invention is installed and the energy loss due to friction between the tidal current and the frame.

A practical embodiment for implementing the device of the present invention will be shown through a comparison with an existing small-scale hydroelectric power generation facility.
The main specifications of the Tsuru-no-yu Hydroelectric Power Plant, which was completed in October 2021 in Senboku City, Akita Prefecture, are as follows.
Flow rate Q: 1.05 m3/sec at maximum output Effective head H: 23.48 m
Flow velocity V: Approximately 21.45 m/sec (calculated)
Overall power generation efficiency: 0.82 (calculated)
Output kW: 199KW
The relationship between output kW, available head H, and flow rate Q is expressed as output kW = 9.8 x H x Q x total generating efficiency K, so it can be seen that the theoretical maximum output that can be obtained from the available water potential energy at the intake of the Tsuru-no-yu Hydroelectric Power Plant is approximately 242 kW, and the total generating efficiency K is approximately 0.82.
Next, assuming that the main specifications of the device of the present invention are as follows, the theoretical maximum output that can be obtained from the available kinetic energy of the taken tidal current is approximately 192 kW.
Tidal current velocity V: 2m/sec. Effective head H: 0.204m (calculated backwards from the tidal current velocity)
Intake cross-sectional area S: 48 m2 (length 6 m x width 8 m)
Cross-sectional area of receiving plate s: 2 m2 (length 2 m x width 1 m)
Flow rate Q: 96 m3/sec (V x S)
Total power generation efficiency K: 1 (assumed)
Theoretical maximum output: approx. 192KW
Furthermore, because there are significant structural differences between the Tsuru-no-yu hydroelectric power station used for comparison and the device of the present invention, it is believed that there is also a large difference in the overall power generation efficiency. However, because the flow rate of the tidal current is large, the required total output can be obtained by making the device of the present invention larger to increase the amount of tidal current that can be taken, or by installing multiple devices of the present invention in the vicinity.

Stable power generation is possible even from low-speed tidal currents, and since no special mechanisms need to be added to deal with the tidal current's periodic 180-degree changes in flow direction, low-cost, highly efficient small-scale tidal power generation can be achieved. In addition, by farming multiple units of this device in suitable locations, the ground-side power receiving and transmitting related equipment can be consolidated and enlarged, further reducing the total power generation costs.

1 Outer frame top plate
2 Connecting plate
3. Bearings
4 Bearing fixing bolts
5 Frame fixing bolt
6 Support plate
7. Wheels
8. Spindle
9 Sprockets or pulleys
10 Chain or Belt
11 Driven shaft
12 Inner frame
13 Running rail
14 Outer frame
15 Intake and draft pipe
16 Shutter
17 Shutter axis
18 Mounting stand
19 Anchor bolts for fixing the mounting base

Claims (2)

A two-shaft conveyor turbine for tidal power generation, characterized by having multiple tiltable support plates. A turbine frame characterized by its shape that takes in large volumes of tidal water, concentrates it on the receiving plate of the conveyor turbine, and guides it to maximize the pressure energy generated on the receiving plate.

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