The present disclosure relates to a device for generating power by using kinetic energy of a fluid, in particular to a power device capable of increasing low wind speed and low tidal current speed, which can be applied to low speed wind power generation and tidal current power generation. The present disclosure belongs to the technical field of power devices or electric generation devices.
The current wind power generation technology has poor performance at low wind speed, and can bring economic benefits only in windy regions having an annual mean wind speed larger than 6 meters per second (m/s). The tidal currents have low speed, which makes them difficult to be directly used for power generation in prior art. The so-called tidal power generation generally refers to a power generation achieved by driving a water turbine generator using a water level difference between high tide and low tide inside and outside the barrage, which has a low water head and a high power generation cost.
In natural environment, low speed wind occurs a lot more frequently than high speed wind in terms both of periods and regions. Taken China for example, it is estimated that the area of windy regions having an annual mean wind speed larger than 6 m/s is smaller than 8% of the total territorial area of China, while the area of windy regions having an annual mean wind speed of 3 m/s to 5 m/s is larger than 60% of the total territorial area of China. An annual mean cumulated time at a certain wind speed is estimated according to Rayleigh statistics. For the windy regions having the annual mean wind speed of 3 m/s to 5 m/s, a windy time at a wind speed of 3 m/s to 8 m/s is 5000 to 6000 hours every year, and a windy time at a wind speed larger than 10 m/s is 50 to 600 hours every year. The former accounts for 60% to 70% of the total time in one year, while the latter accounts for only 0.6% to 7% of the total time in one year.
Although the tidal current speed is much lower than the available wind speed, the energy density of the tidal current is substantially the same as that of the available wind energy because the density of water is much higher than that of the air. If the mean speed of the diurnal tide can reach 1.0 m/s to 1.5 m/s, it is estimated that the power generation cost by using the tidal current is lower than the power generation cost by using the offshore wind. The available amount of the tidal current energy resource is much more than that of the wind energy resource. Taken China as example, it is estimated that the tidal current energy resource is 70 times of the wind energy resource. Therefore, the researches of efficient low speed wind power generation and tidal current hydro power generation technologies have great economic and environmental benefits.
A power of a wind turbine is PM=CpP=½pACpW3, wherein Cp denotes a wind energy utilization coefficient, which is a parameter used to evaluate a performance of the wind turbine. A power of wind is P=½pAW3, wherein p denotes the density of air, A denotes a swept area of a wind wheel, and W denotes the wind speed. According to specialist overview (Renewable and Efficient Electric Power Systems, by Gilbert M. Masters, ISBN 0-471-28060-7, John Wiley&Sons Inc., Chapter 6, Wind Power Systems, p. 307-383) and researches (for example, Paraschivoiu, I., Wind Turbine Design With Emphasis on Darrieus Concept, Presses internationales Polytechnique, 2002, P. 148), a theoretic optimum value of Cp of a horizontal axis wind turbine is Cpmax≈0.59, and a theoretic optimum value of Cp of a vertical axis wind turbine is Cpmax≈0.64. However, the optimum performance achieved in prior art is that Cp. of the horizontal axis wind turbine is 0.45 and Cpmax, of the horizontal axis wind turbine is 0.35. Moreover, Cp=Cp(λ, Φ, θ), in other words, Cp is changed with the change of the tip speed ratio λ, the pitch angle Φ, and the yaw angle θ (wind direction). When λ is in a range of 4 to 6, Cp is Cpmax. One of disadvantages of the horizontal axis technology is that a value of Φ corresponding to its Cpmax is changed with the change of the wind speed or the wind direction. Therefore, a variable pitch control have to be performed to regulate the value of Φ, and a yaw control have to be performed to follow the wind direction, so as to achieve a performance approaching Cpmax during operation. The variable pitch control may improve a cost performance of a large-scale turbine; however, it will reduce a cost performance of a medium-scale turbine or a small-scale turbine to some extent. The smaller the turbine, the poor the cost performance. Therefore, the medium-scale turbine and the small-scale turbine are generally fixed-pitch types (i.e. stalled types), and their Cps at mean wind speeds smaller than rated wind speeds is
The essence of improving the wind turbine performance is to increase Cp. The inventors have recognized during the long term experiments, analyses, and researches that the low Cp of the vertical axis wind turbine may be due to the method for researching blades. The inventors have created methods for researching a strongly turbulent vertical axis flow field and for designing the blade, which are totally different from the airfoil design methods. After unremitting explorations, the inventors developed FW blades which are efficient at the low flow rate, and its Cpmax reaches 0.50 in the range of λ<2, which breaks through the technical bottleneck that vertical axis Cp is smaller than the horizontal axis Cp. Moreover, the blades are fixed-pitch efficient types, and Cp at a mean wind speed in a wind speed range of 2 m/s to 10 m/s is
An object of the present disclosure is to, in view of the disadvantage in prior art that the power generation efficiency is low at a low flow rate state, provides a power device capable of effectively increasing the utilization efficiency of the low flow rate fluid (hereafter abbreviated as a power device for increasing low flow rate) is provided, which can be applied to both of the wind power generation and the water power generation and also can supply power for other applications.
Terms in wind energy art are used to describe the technical solutions of the present disclosure, and the terms may be changed according to different applications in the embodiments. For example, for the application in water, “wind wheel” is changed to “water wheel”, and “wind speed” is changed to “current speed” etc., while the term “windshield” is still adopted.
In the present disclosure, the technical problem is solved by the following technical solution. A power device for increasing low flow rate includes a load-bearing body, a truss connected to the load-bearing body, and at least two wind wheels connected to the truss. The truss and the wind wheels constitute a vertically-constrained horizontal-revolute pair. The wind wheels are respectively distributed at two sides of a center vertical line of the truss. A windshield device is located between the wind wheels, and the wind wheels located at two sides of the windshield device have opposite rotation directions; or a windshield device is further disposed in the wind wheel; or a windshield device is further disposed between adjacent upper and lower wind wheels. The power of the wind wheel is controlled by regulating an azimuth or a wind-blocking area of the windshield device without increasing the swept area of the wind wheel, so as to achieve the increased Cp at low wind speed, thereby reducing the cost for utilizing the wind energy or the tidal energy.
The specific technical solution to achieve this object is as follows.
A power device for increasing low flow rate includes a load-bearing body, a truss connected to the load-bearing body, and at least two wind wheels connected to the truss. The wind wheel includes a wheel frame and a plurality of blades uniformly distributed at a periphery of the wheel frame. The truss and the wind wheels constitute a vertically-constrained horizontal-revolute pair. The wind wheels are respectively disposed at two sides of a center vertical line of the truss. The characteristic is that a windshield device is disposed between the wind wheels, the wind wheels located at two sides of the windshield device have opposite rotation directions, rotation directions of the wind wheels are set to allow a power output region of the blade to be located at a side adjacent to the windshield device, the truss is rotatably connected to the load-bearing body, and a rotation axis of the truss and rotation axes of the wind wheels are located in a same vertical plane.
Furthermore, the wheel frame of the wind wheel includes a spindle-containing wheel frame and a spindle-free wheel frame. When the wheel frame is the spindle-containing wheel frame, the wheel frame of the wind wheel comprise a spindle and cantilevers, one end of the cantilever is directly or indirectly connected to the spindle, and the other end of the cantilever is directly or indirectly connected to the blade. When the wheel frame is the spindle-free wheel frame, the wheel frame comprises cantilevers, one end of the cantilever is connected to the truss or a load via a bearing, and the other end of the cantilever is directly or indirectly connected to the blade. If the blade is connected to the cantilever via a baffle, the blade is indirectly connected to the cantilever. If the cantilever is connected to the spindle via a flange, the cantilever is indirectly connected to the spindle. It should be noted that the indirect connection is not limited thereto.
In the above-described technical solutions, a windshield device can be disposed in the wind wheel. A horizontal size of the windshield device is smaller than a diameter of the wind wheel. A vertical size of the windshield device is smaller than a height of the wind wheel.
The truss includes a plurality of cross beams, a plurality of upright columns to support the plurality of cross beams, and optionally, a plurality of inclined struts. When the truss includes more than two cross beams, a truss structure having a plurality of rows of cross beams in a vertical direction is constituted. A windshield device is further disposed between upper and lower wind wheels in two adjacent rows.
A structure of the windshield device includes a windshield device formed by a sheet or a column, and a windshield device formed by a combination of a sheet and a column. A sealed hollow cavity is defined in the windshield device. A shape of the windshield device includes a planar plate, a curved plate, an arc-shaped plate, a triangular prism formed by planar plates, by curved plates, by arc-shaped plates, by two curved plates and one planar plate, by two planar plates and one curved plates, a half-cylinder, a trapezoidal prism, a cylinder, a cylindroid, and a column having a sinuous surface. However, the shape of the windshield device is not limited thereto.
A power control of the wind wheel can be achieved by regulating an azimuth or a wind-blocking area of the windshield device. Or a wind rudder is further provided to follow the wind direction to avoid an oscillation caused by varied wind direction during regulating the windshield.
A placement manner of the load-bearing body comprises placing on ground, placing under water, floating on water surface, standing on water bottom while protruding out from water surface, and floating in air.
When the load-bearing body is placed on ground or under water, the load-bearing body comprises a tower standing on the ground, or comprises a base located under the water and a tower fixedly connected to the base, a top of the tower is connected to the truss, the wind wheels are connected to the truss, and the windshield devices are connected to the truss; or a windshield device is further disposed in the wind wheel.
When the load-bearing body floats on water surface, the load-bearing body comprises a plurality of buoys and a horizontal frame fixedly connected onto the buoys, a bottom surface of the horizontal frame is connected to the truss, the wind wheels are connected to the truss, and the windshield devices are connected to the truss, thereby obtaining a water turbine; or the load-bearing body comprises a plurality of buoys, a horizontal frame fixedly connected onto the buoys, and a tower standing on the horizontal frame, a top of the tower is connected to the truss, the wind wheels are connected to the truss, and the windshield devices are connected to the truss, thereby obtaining a wind turbine; or a complete of the water turbine is connected to a bottom of the horizontal frame of the wind turbine, thereby obtaining a wind and water dually-useful turbine; or the windshield device is further disposed in the wind wheel of the water turbine, the wind turbine, or the wind and water dually-useful turbine.
When the load-bearing body stands on water bottom while protrudes out from water surface, the load-bearing body comprises a plurality of pillars standing in water and a horizontal frame fixedly connected to portions of the pillars protruded out from the water surface, a bottom surface of the horizontal frame is connected to the truss, the wind wheels are connected to the truss, and the windshield devices are connected to the truss, thereby obtaining a water turbine; or the load-bearing body comprises a plurality of pillars standing in water, a horizontal frame fixedly connected to portions of the pillars protruded out from the water surface, and a tower standing on the horizontal frame, a top of the tower is connected to the truss, the wind wheels are connected to the truss, and the windshield devices are connected to the truss, thereby obtaining a wind turbine; or a complete of the water turbine is connected to a bottom of the horizontal frame of the wind turbine, thereby obtaining a wind and water dually-useful turbine; or the windshield device is further disposed in the wind wheel of the water turbine, the wind turbine, or the wind and water dually-useful turbine.
When the load-bearing body floats in air, the load-bearing body comprises a floater floating in the air and a rope-like member tied to the floater; the truss is connected to the rope-like member, the wind wheels are connected to the truss, and the windshield devices are connected to the truss, thereby obtaining a wind turbine floating in the air; or the windshield device is further disposed in the wind wheel; the wind turbine is anchored on ground or a building on the ground via an anchor cable.
Two to five blades are uniformly distributed at the periphery of the wheel frame, thereby obtaining a two-blade wind wheel, a three-blade wind wheel, a four-blade wind wheel, and a five-blade wind wheel, respectively. The blade is FW blade having a high efficiency at low flow rate. A number of the wind wheels disposed at two sides of a rotation axis of the truss are the same, and the wind wheels are symmetrically located at the two sides of the rotation axis of the truss.
The wheel frame has a multi-row structure. The cantilevers of the wheel frame are arranged in rows. Each blade has a plurality of sections. A number of the sections is corresponding to a number of the rows of the cantilevers. Each section of the blade is disposed at ends of the corresponding cantilevers located in the adjacent rows.
For the water turbine, the following technical solutions are further provided. The wheel frame is connected to a buoyancy-producing gas cabin. A shape of the gas cabin is a cylindrical shape, a conical shape, or a spherical crown shape. When the load-bearing body floats on the water surface, the load-bearing bodies are connected via the horizontal frames, thereby forming a floating water turbine set. The load-bearing body is shared by the water turbine and the wind turbine. A rotatable connection portion of the wheel frame with the load-bearing body is disposed above the water surface. The load-bearing body further include a load-bearing member which has been established on the water, for example, a bridge, a wharf trestle bridge, a hydrologic station trestle bridge, a floating island, a lighthouse, an aquaculture buoyancy tank, and so on.
The present disclosure has following beneficial effects as compared to the prior art.
1) The windshield device allows the incoming wind to pass through a region between its outer edge and the adjacent blade, which sharply increases the flux density of the wind passing through this region, thereby inevitably increasing the speed of the wind passing through this region (Bernoulli principle), while the setting of rotation direction allows the power output region of the blade to be established at the vicinity of this region; the two aspects have a combined effect that the windshield device increases the speed of wind passing through the power output region of the blade (the increase is significant especially for low speed wind), thereby increasing the power of the wind wheel without increasing the swept area and the weight of the wind wheel, thus solving the problem in the prior art, and significantly increasing the Cp at low wind speed.
2) The design that the rotation axis of the truss and the rotation of axes of the wind wheels are in the same vertical plane not only increases the Cp at low wind speed, but can automatically follow the wind direction to allows the upright column to keep away from the flowing path of the wind.
3) The power control can be achieved by regulating the azimuth and the wind-blocking area of the windshield device, thereby solving the problem in the prior art that the power control is difficult to be performed in the conventional vertical axis turbine. The power control in the prior art is achieved by regulating rotational components, which has a high cost. The windshield device in the present disclosure is not a rotational component, thereby having a low control cost, therefore, the economic performance is much higher than the prior art when applied to a turbine having a low rated wind speed or a small-scale turbine.
4) The gas inflation design for the enclosed hollow cavity in the windshield can produce buoyancy, thereby reducing the rotation resistance of the water wheel and the truss, which is favorable to the further increase of the Cp at low flow rate.
5) The windshield device fixedly connected to the upper and lower cross beams also has a function of referencing the rigidity of the truss.
6) By using the FW blade which is effective at low flow rate developed by the inventor, the operation is effective without the pitch varying system, and the Cp is significantly increased.
7) When the buoys is used to bear load, the building of the underwater foundation can be saved, and the effect is that the cost is reduced, the turbine can be anchored by an anchor chain or moved by a tugboat according to water conditions, which is convenient and flexible.
8) When the rotatable connection portions of the wheel frames with the load-bearing body are disposed above the water surface, the resistances of the dynamic seals of the rotatable connection portions can be reduced (since water-tightness is required, a dynamic seal in water is harder than that in air), which is advantageous to increase the Cp, moreover, the loads (for example, electric generators, gearboxes, clutches, and other components) can be disposed above the water surface, thereby avoiding the issues about water-tightness.
9) The design combing the water turbine and the wind turbine can share the load-bearing body to decrease the cost, and is very suitable for sea wind and tidal current power generation.
10) The cost for utilizing low speed wind is significantly reduced, thereby having the characteristic (i.e. high performance and low cost) of the advanced technology.
In the exemplary drawings, F1 represents a windshield device located between right and left wind wheels, F2 represents a windshield device located in a wind wheel, F3 represents a windshield device located between upper and lower wind wheels, a shadowing surface represents a windshield surface.
The present disclosure will now be described in detail with referent to the embodiments and the accompany drawings. Loads in the embodiments are represented with electric generators as example. However, it is not limited to the examples disclosed in the present disclosure. F1 to F3 denote windshield devices, in which different numerals indicate different types of the windshield devices.
As shown in
A water turbine in this embodiment is shown in
A wind turbine in this embodiment is shown in
A wind turbine in this embodiment is shown in
A wind turbine in this embodiment is shown in
A water turbine in this embodiment is shown in
A wind turbine in this embodiment is shown in
Only some of various shapes of the windshield are illustrated in the above-described embodiments. Other shapes (four of which are shown in
Further features of the present disclosure are described as below.
Rotation directions of the wind wheels located at two sides of the windshield device F1 are set to allow a power output region of the blade to be located at a side adjacent to the windshield. The power output region refers to an azimuth region within which the blade can output power. An attack angle of the blade is varied in 360 degrees during the rotation. However, the blade can output power only at the azimuth in several tens of degrees, but cannot output power at the other azimuth angles due to the stall. The rotation axis of the truss and the rotation axes of the wind wheels are in a same vertical plane. The numbers of the wind wheels located at two sides of the rotation axis of the truss are the same, and the wind wheels are symmetrically located at the two sides of the rotation axis of the truss, which are embodied in all embodiments as descried above.
The windshield device can have further functions. For example, in the water turbines in Embodiments 1, 2, and 6, the windshields have enclosed hollow cavity structures. The buoyancy produced by filling gas into the hollow cavity can reduce the rotation resistances of the water wheels and the trusses. For example, for the wind turbine in the Embodiment 7, the buoyancy produced by filling hydrogen or helium gas into the gasbag of the windshield can reduce the loads of the floater. For example, the windshield devices F1 in Embodiments 1 and 4 have reinforcement effects on rigidities of the trusses.
For the windshield device F2 disposed in the wind turbine without the spindle, the windshield is non-rotatable and has an asymmetrical shape with respect to the wheel axis; therefore, an interference effect on the flow field in the wind wheel can be achieved by regulating the azimuth and the shape of the windshield, which is embodied in the Embodiment 3.
By using the FW blade having a high efficiency at low flow rate as shown in
By disposing the rotatable connection portions of the wheel frames with the load-bearing body above the water surface and disposing the load-bearing frame adjacent to the water surface, no component with dynamic seal needs to be disposed underwater, as embodied in Embodiments 2 and 6. The effect is that it is advantageous to improve performance and easy to maintain, thereby reducing the cost, and the water current at the water surface having a high speed (as compared to that deep down under water) can be fully utilized, which is advantageous to increase the Cp.
By using buoys to load bear, the building of underwater foundation is saved, as embodied in Embodiments 2 and 5. The effect is that the cost is reduced, the turbine can be anchored by an anchor chain or moved by a tugboat according to water conditions, which is convenient and flexible.
In addition to the above-described embodiments, the present disclosure can also include other implementation manners. For example, the water turbines in the Embodiment 2 and the wind turbines in the Embodiment 5 can share the same set of the buoys H and the horizontal frame 7, thereby forming a wind and water dually-useful turbine. For example, a wind rudder (shown with broken lines on the central portion of the upper cross beam in
In summary, in the present disclosure, the Cp at low wind speed (flow rate) is significantly increased, and its utilization cost is reduced, thereby having the characteristic (i.e. high performance and low cost) of the advanced technology. Not only resourceful tidal current, ocean current, river current, and gentle wind can be used to generate electricity, but other use patterns of the low flow rate fluid can be also developed.
Number | Date | Country | Kind |
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201711186506.6 | Nov 2017 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2018/116733 | 11/21/2018 | WO | 00 |