A long-term self-sustaining energy harvesting device and method with optimized oscillating hydrofoil airfoil.

Abstract

This invention discloses a long-term self-sustaining energy harvesting device and method with optimized oscillating hydrofoil airfoil profile. The energy harvesting device includes multiple spaced-apart oscillating hydrofoil units arranged in an array. Each oscillating hydrofoil unit includes a hydrofoil shell and a triboelectric nanogenerator. Multiple triboelectric nanogenerators are arranged side-by-side and closely fitted together along the chord length of the airfoil shell. The size of each triboelectric nanogenerator varies with the thickness of the hydrofoil shell, ensuring that the upper and lower arc surfaces of each triboelectric nanogenerator are tangent to the inner wall of the hydrofoil shell. When the oscillating hydrofoil unit pitches or oscillates under the influence of tidal currents, its internal triboelectric nanogenerators capture mechanical energy in real time and generate electricity, replacing the traditional oscillating hydrofoil energy conversion device. This method is simpler in structure, easier to manufacture, lower in cost, and improves energy harvesting efficiency and self-sustainability.

Description

Technical Field

[0001] This invention relates to the field of energy harvesting technology, specifically to an oscillating hydrofoil-optimized long-term self-sustaining energy harvesting device and method. Background Technology

[0002] my country has a long coastline and numerous rivers and lakes, possessing considerable marine and hydropower resources. With the development of human society, the demand for energy is increasing, making the more comprehensive development of marine resources an inevitable trend. Tidal energy has advantages such as high energy density and wide distribution. It is a readily available, inexhaustible, and clean renewable energy source. Therefore, self-sustaining and long-term operational wave energy harvesting devices have become a research hotspot.

[0003] With the development of tidal energy technology in my country in recent years, many tidal energy units in my country have been successfully connected to the grid or used to supply power to islands. However, most of my country's tidal energy devices are horizontal axis type, which has poor start-up performance and is not very suitable for shallow waters, resulting in insufficient development of tidal resources. Generally, under the same sea conditions at the same depth, the sweeping area of ​​an oscillating hydrofoil is about three times that of a horizontal axis impeller. Oscillating hydrofoil technology for capturing tidal energy has obvious advantages in shallow waters and is particularly suitable for installation in shallow waters such as riverbeds and along the coast. Summary of the Invention

[0004] Given the poor start-up capability of current tidal energy devices and the low capture efficiency in nearshore shallow water areas, in order to develop and utilize the vast and abundant shallow sea tidal energy resources, this invention provides an oscillating hydrofoil-optimized long-term self-sustaining energy harvesting device and energy harvesting method. It can capture tidal energy under wave action in shallow water or riverbed areas and convert it into electrical energy, and can automatically operate for a long time.

[0005] The technical solution adopted in this invention is:

[0006] I. A Long-Term Self-Sustaining Energy Harvesting Device with Optimized Oscillating Hydrofoil Airfoil

[0007] It includes multiple oscillating hydrofoil units arranged at intervals, and the multiple oscillating hydrofoil units are distributed in an array; each oscillating hydrofoil unit includes a hydrofoil shell and a triboelectric nanogenerator, and multiple triboelectric nanogenerators are arranged in parallel along the chord length of the hydrofoil shell, and the upper and lower arc surfaces of each triboelectric nanogenerator are tangent to the inner wall of the hydrofoil shell.

[0008] The hydrofoil shell is in the NACA series airfoil shape. The hydrofoil shell has an upper surface and a lower surface, both of which are convex arc surfaces. The side of the hydrofoil shell that first contacts the tidal current is the leading edge, and the side that last contacts the tidal current is the trailing edge. The curvature of the upper surface is greater than that of the lower surface, and the maximum curvature is 15%-25% of the chord length. The radius of the inscribed circle of the leading edge is 1%-3% of the chord length. The maximum thickness of the hydrofoil shell is 12%-18% of the chord length. The location of the maximum thickness of the hydrofoil shell is 30%-40% of the chord length near the leading edge. At the trailing edge of the hydrofoil shell, the upper and lower surfaces are connected by a gradual change in passivation.

[0009] The triboelectric nanogenerator includes multiple triboelectric nanogenerator units, a lithium battery, and a housing. The housing is a cylindrical hollow shell, and multiple triboelectric nanogenerator units and a lithium battery are encapsulated inside the housing. Each triboelectric nanogenerator unit is electrically connected to the lithium battery. The arc portion of the outer surface of each triboelectric nanogenerator unit is tightly fitted to the curved inner wall of the housing. The triboelectric nanogenerator units are stacked from top to bottom in ascending order of size, and each triboelectric nanogenerator unit is fixedly connected to the housing.

[0010] The triboelectric nanogenerator unit includes a power generation substrate and a set of cross rollers. The power generation substrate has an arc-shaped groove. A set of cross rollers is placed along the length of the arc-shaped inner wall of the arc-shaped groove of the power generation substrate. The set of cross rollers includes at least two rollers with different electronegativity materials attached to their surfaces.

[0011] The power generation substrates, each containing the cross rollers, are stacked one on top of the other, such that the side profile of the stacked power generation substrates is circular, and the arc of the arc groove of the power generation substrate at the bottom is smaller than that of the arc groove of the power generation substrate at the top.

[0012] The power generation substrate is mainly composed of a top layer, interdigitated electrodes and a bottom layer stacked tightly from top to bottom. Interdigitated electrodes are provided between the top layer and the bottom layer. The top layer is a nylon layer and the bottom layer is a polylactic acid layer.

[0013] The cross rollers include multiple rollers I and multiple rollers II. The rollers I and rollers II are arranged alternately and closely along the groove length on the arc-shaped inner wall of the arc groove of the power generation substrate. Both rollers I and rollers II are cylinders. The surface of roller I is coated with polytetrafluoroethylene, and the surface of roller II is coated with nylon.

[0014] Each power generation substrate of the triboelectric nanogenerator is electrically connected to the lithium battery via a diode bridge.

[0015] Each of the four corners of the hydrofoil shell is equipped with an anchor chain mooring. The anchor chain mooring is of the unstable type, and each oscillating hydrofoil unit is connected to the seabed or riverbed by the anchor chain mooring.

[0016] Several of the aforementioned oscillating hydrofoil units are arranged side by side in a row as a group of horizontal rows. Multiple groups of horizontal rows are arranged side by side in the same horizontal plane to form an array. The lateral spacing between each oscillating hydrofoil unit is 4-6 times the chord length, and the spacing between each group of horizontal rows is 0.25-0.3 times the chord length.

[0017] II. An Energy Harvesting Method Based on Oscillating Hydrofoil Airfoil Optimization for Long-Term Self-Sustaining Energy Harvesting Devices

[0018] The method includes the following steps:

[0019] 1) Multiple oscillating hydrofoil units are moored to the seabed or riverbed by anchor chains and then arranged in an array on the water surface;

[0020] 2) When subjected to tidal currents, the tidal currents cause each oscillating hydrofoil unit to pitch or sway on the water surface. The cross rollers in the triboelectric nanogenerators in each oscillating hydrofoil unit roll on the power generation substrate. The surfaces of roller I and roller II rub against each other, thereby generating surface charges. The surface of roller I generates positive charges, and the surface of roller II generates negative charges. The surface charges induce the top layer and interdigital electrodes of the power generation substrate through electrostatic induction, causing the top layer to generate positive charges and the interdigital electrodes to generate negative charges. Combined with the reciprocating changes in the relative positions of the top layer and interdigital electrodes with the cross rollers, electrons are driven to reciprocate in the circuit, thereby generating an alternating current signal.

[0021] 3) The AC signal described in step 2 is converted into a DC signal by a diode bridge and then transmitted to the lithium battery to charge it.

[0022] The beneficial effects of this invention are:

[0023] 1. A triboelectric nanogenerator is used to convert the tidal energy captured by the oscillating hydrofoil turbine, replacing the previous complex energy conversion device. This makes production simpler, lower in cost, and simpler in structure.

[0024] 2. The traditional hydrofoil structure has been optimized, improving the hydrofoil's energy capture efficiency.

[0025] 3. The oscillating hydrofoil unit is fixed by anchor chains, which can improve the self-sufficiency of the energy harvesting device, reduce maintenance frequency, and lower costs.

[0026] 4. Each oscillating hydrofoil unit is arranged in an array to enhance the positive influence between the oscillating hydrofoil units, which can improve the energy capture efficiency of each other. Attached Figure Description

[0027] Figure 1 This is the overall design drawing of the oscillating hydrofoil unit.

[0028] Figure 2 This is a schematic diagram of the overall design of a triboelectric nanogenerator.

[0029] Figure 3 This is a front view of a triboelectric nanogenerator.

[0030] Figure 4 This is a schematic diagram showing the breakdown of a triboelectric nanogenerator.

[0031] Figure 5 This is a schematic diagram illustrating the power generation principle of a triboelectric nanogenerator.

[0032] Figure 6 This is a schematic diagram of the distribution of the oscillating hydrofoil unit array.

[0033] In the diagram: 1. Hydrofoil shell, 2. Triboelectric nanogenerator, 3. Anchor chain mooring, 4. Shell, 5. Cross rollers, 6. Power generation substrate, 7. Roller I, 8. Roller II, 9. Interdigitated electrode, 10. Top layer, 11. Bottom layer, 12. Lithium battery, 13. Diode bridge. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] This invention includes multiple spaced-apart oscillating hydrofoil units, which are arranged in an array; the overall design diagram of the oscillating hydrofoil units is shown below. Figure 1 As shown, each oscillating hydrofoil unit includes a hydrofoil shell 1 and a triboelectric nanogenerator 2. Multiple triboelectric nanogenerators 2 are arranged in parallel along the chord length of the hydrofoil shell 1. The size of each triboelectric nanogenerator 2 varies with the thickness of the hydrofoil shell 1, such that the upper and lower arc surfaces of each triboelectric nanogenerator 2 are tangent to the inner wall of the hydrofoil shell 1.

[0036] The hydrofoil shell 1 is a NACA series airfoil, which is a column with a spindle-shaped cross-section. The hydrofoil shell 1 has an upper surface and a lower surface, both of which are convex arc surfaces. The side of the hydrofoil shell (1) that first contacts the tidal current is the leading edge, and the side of the hydrofoil shell (1) that last contacts the tidal current is the trailing edge. The curvature of the upper surface is greater than that of the lower surface, and the maximum curvature is 15%-25% of the chord length. The curvature of the airfoil affects the separation point and reattachment point of the fluid, which can obtain more lift at low speeds. A larger curvature usually causes the fluid to generate greater acceleration on the airfoil surface, thereby increasing lift. The radius of the inscribed circle of the leading edge is 1%-3% of the chord length. A smaller radius helps to enhance the leading edge vortex, increase lift, and help maintain flow adhesion. The maximum thickness of the hydrofoil shell 1 is 12%-18% of the chord length. A larger thickness will increase structural strength and lift. However, it will relatively increase drag. At low speeds, a larger thickness will increase lift. A thicker airfoil helps to delay separation and maintain attached flow. The maximum thickness of the hydrofoil shell 1 is located at 30%-40% of the chord length along the airfoil chord near the leading edge. A forward maximum thickness can increase lift performance. At the trailing edge of the hydrofoil shell 1, the upper and lower surfaces are connected by a gradual change to achieve a blunt transition. Compared with the NACA series airfoils, the trailing edge of the hydrofoil shell 1 is blunter or smoother to reduce the degree of water flow separation and allow the water flow to leave the airfoil surface smoothly. A smooth trailing edge can reduce the generation of turbulence and reduce the intensity of vortices, thereby reducing drag and increasing lift. A blunt trailing edge helps to delay separation and reduce instability. The gradual change allows the water flow to gradually adapt to the shape of the trailing edge, making the water flow more stable when leaving the airfoil surface, thereby reducing vortex loss and improving energy capture efficiency.

[0037] The overall design diagram of the triboelectric nanogenerator is as follows: Figure 2 As shown, the front view is as follows Figure 3 As shown, the triboelectric nanogenerator 2 includes multiple triboelectric nanogenerator units, a lithium battery 12, and a housing 4. The housing 4 is a cylindrical hollow shell made of polymethyl methacrylate. Multiple triboelectric nanogenerator units and lithium batteries 12 are encapsulated inside the housing 4. Each triboelectric nanogenerator unit and lithium battery 12 are electrically connected. The arc portion of the outer surface of each triboelectric nanogenerator unit is tightly fitted to the curved inner wall of the housing 4. The triboelectric nanogenerator units are stacked from top to bottom in ascending order of size. Each triboelectric nanogenerator unit is fixedly connected to the housing 4.

[0038] The triboelectric nanogenerator unit has a cross-roller structure, including a power generation substrate 6 and a set of cross rollers 5. The power generation substrate 6 has an arc-shaped groove. A set of cross rollers 5 are placed along the length of the arc-shaped inner wall of the groove, allowing them to roll on the power generation substrate 6. Each set of cross rollers 5 includes at least two rollers with different electronegativity materials attached to their surfaces. A schematic diagram of the triboelectric nanogenerator is shown below. Figure 4As shown, the power generation substrates 6, each with a cross roller 5, are stacked one on top of the other, so that the side profile of the stacked power generation substrates 6 is circular. The arc of the arc groove of the power generation substrate 6 at the bottom is smaller than the arc of the arc groove of the power generation substrate 6 at the top.

[0039] More specifically, the power generation substrate 6 is mainly composed of a top layer 10, interdigitated electrodes 9 and a bottom layer 11 stacked tightly from top to bottom. Interdigitated electrodes 9 are disposed between the top layer 10 and the bottom layer 11. The top layer 10 is a thin layer of nylon and the bottom layer 11 is a thin layer of polylactic acid. The thickness of the top layer 10, interdigitated electrodes 9 and bottom layer 11 is 10-15 mm.

[0040] The cross rollers 5 include multiple rollers I7 and multiple rollers II8. Rollers I7 and II8 are arranged alternately and closely along the groove length on the arc-shaped inner wall of the arc groove of the power generation substrate 6. Rollers I7 and II8 are both cylinders with a diameter of 30mm and are made of acrylic material. Roller I7 has a 60μm thick polytetrafluoroethylene film attached to its surface, and roller II8 has a 60μm thick nylon film attached to its surface. The interdigitated electrode 9 is made of copper and is cut from copper. To avoid charge cancellation, the width of the interdigitated electrode 9 is 30mm.

[0041] Each power generation substrate 6 of the triboelectric nanogenerator unit is electrically connected to the lithium battery 12 via a diode bridge 13, which converts the AC signal generated by the power generation substrate 6 into a DC signal.

[0042] An anchor chain mooring 3 is installed at the lower part of each of the four corners of the hydrofoil shell 1. The anchor chain mooring 3 is a type of anchor chain without stops and is made of anchor chain steel. Each oscillating hydrofoil unit is connected to the seabed or riverbed by anchor chain through the anchor chain mooring 3.

[0043] A schematic diagram of the distribution of the oscillating hydrofoil unit array is shown below. Figure 6 As shown, several oscillating hydrofoil units are arranged side by side in a row, forming a group of horizontal rows. Multiple groups of horizontal rows are arranged longitudinally on the same horizontal plane to form an array, which can mutually enhance the energy capture efficiency of each oscillating hydrofoil unit. The lateral spacing between each oscillating hydrofoil unit is 4-6 times the chord length to minimize the influence of the trailing edge vortex of the oscillating hydrofoil unit in front on the energy capture efficiency of the oscillating hydrofoil unit behind during oscillation. The spacing between each group of horizontal rows is 0.25-0.3 times the chord length to maximize the effect of the airfoil effect on the energy capture efficiency of the oscillating hydrofoil unit.

[0044] An energy harvesting method based on the above-mentioned oscillating hydrofoil airfoil optimization long-term self-sustaining energy harvesting device is presented, and the power generation principle diagram of the triboelectric nanogenerator is shown below. Figure 5 As shown, the method includes the following steps:

[0045] 1) In the sea or river, multiple oscillating hydrofoil units are fixed to the seabed or riverbed by anchor chains 3, forming an array distribution on the water surface; preferably, they are arranged below the water surface, near the water surface.

[0046] 2) When subjected to tidal currents, the tidal currents cause each oscillating hydrofoil unit to pitch or sway on the water surface. The cross rollers 5 in the triboelectric nanogenerator 2 of each oscillating hydrofoil unit roll on the power generation substrate 6. The surfaces of rollers I 7 and II 8 rub against each other, thereby generating surface charges. More specifically, the surface of roller I 7 generates positive charges, and the surface of roller II 8 generates negative charges. The surface charges induce the top layer 10 and interdigital electrodes 9 of the power generation substrate 6 through electrostatic induction, causing the top layer 10 to generate positive charges and the interdigital electrodes 9 to generate negative charges. Combined with the reciprocating changes in the relative positions of the top layer 10 and interdigital electrodes 9 with the cross rollers 5, electrons are driven to move back and forth in the circuit, thereby generating an alternating current signal, realizing the process of capturing mechanical energy and converting mechanical energy into electrical energy.

[0047] 3) The AC signal is converted into a DC signal by the diode bridge 13 and then transmitted to the lithium battery 12 to charge the lithium battery 12. The converted electrical energy is collected and stored.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the method of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil, characterized in that: It includes multiple oscillating hydrofoil units arranged at intervals, and the multiple oscillating hydrofoil units are arranged in an array; each of the oscillating hydrofoil units includes a hydrofoil shell (1) and a triboelectric nanogenerator (2), and multiple triboelectric nanogenerators (2) are arranged in parallel along the chord length of the hydrofoil shell (1), and the upper and lower arc surfaces of each of the triboelectric nanogenerators (2) are tangent to the inner wall of the hydrofoil shell (1); The hydrofoil shell (1) is in the shape of a NACA series airfoil. The hydrofoil shell (1) has an upper surface and a lower surface, both of which are convex arc surfaces. The side of the hydrofoil shell (1) that first contacts the tidal current is the leading edge, and the side of the hydrofoil shell (1) that last contacts the tidal current is the trailing edge. The curvature of the upper surface is greater than that of the lower surface and the maximum curvature is 15%-25% of the chord length. The radius of the inscribed circle of the leading edge is 1%-3% of the chord length. The maximum thickness of the hydrofoil shell (1) is 12%-18% of the chord length. The maximum thickness of the hydrofoil shell (1) is located at 30%-40% of the chord length near the leading edge. At the trailing edge of the hydrofoil shell (1), the upper surface and the lower surface are connected by a gradual change for passivation.

2. The long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil according to claim 1, characterized in that: The triboelectric nanogenerator (2) includes multiple triboelectric nanogenerator units, a lithium battery (12), and a shell (4). The shell (4) is a cylindrical hollow shell. Multiple triboelectric nanogenerator units and a lithium battery (12) are encapsulated inside the shell (4). Each triboelectric nanogenerator unit and the lithium battery (12) are electrically connected. The arc portion of the outer surface of each triboelectric nanogenerator unit is tightly fitted to the curved inner wall of the shell (4). Each triboelectric nanogenerator unit is stacked from top to bottom in ascending order. Each triboelectric nanogenerator unit is fixedly connected to the shell (4).

3. The long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil according to claim 2, characterized in that: The triboelectric nanogenerator unit includes a generator substrate (6) and a set of cross rollers (5). The generator substrate (6) has an arc-shaped groove. A set of cross rollers (5) is placed along the length of the arc-shaped inner wall of the arc-shaped groove of the generator substrate (6). The set of cross rollers (5) includes at least two rollers with different electronegativity materials attached to their surfaces. Each power generation substrate (6) with the cross rollers (5) is stacked on top of each other, so that the side profile of the stacked power generation substrates (6) is circular, and the arc of the arc groove of the power generation substrate (6) at the bottom is smaller than the arc of the arc groove of the power generation substrate (6) at the top.

4. The long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil according to claim 3, characterized in that: The power generation substrate (6) is mainly composed of a top layer (10), interdigitated electrodes (9) and a bottom layer (11) stacked from top to bottom. The interdigitated electrodes (9) are arranged between the top layer (10) and the bottom layer (11). The top layer (10) is a nylon layer and the bottom layer (11) is a polylactic acid layer.

5. The long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil according to claim 3, characterized in that: The cross rollers (5) include multiple rollers I (7) and multiple rollers II (8). The rollers I (7) and rollers II (8) are arranged alternately and closely along the groove length on the arc-shaped inner wall of the arc groove of the power generation substrate (6). Both rollers I (7) and rollers II (8) are cylindrical. The surface of rollers I (7) is coated with polytetrafluoroethylene, and the surface of rollers II (8) is coated with nylon.

6. The long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil according to claim 3, characterized in that: Each power generation substrate (6) of the triboelectric nanogenerator and the lithium battery (12) are electrically connected via a diode bridge (13).

7. The long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil according to claim 1, characterized in that: An anchor chain mooring (3) is provided at the lower part of each of the four corners of the hydrofoil shell (1). The anchor chain mooring (3) is of the type of unstoppable anchor chain. Each oscillating hydrofoil unit is connected to the seabed or riverbed by the anchor chain mooring (3).

8. The long-term self-sustaining energy harvesting device with optimized oscillating hydrofoil airfoil according to claim 1, characterized in that: Several of the aforementioned oscillating hydrofoil units are arranged side by side in a row as a group of horizontal rows. Multiple groups of horizontal rows are arranged side by side in the same horizontal plane to form an array. The lateral spacing between each oscillating hydrofoil unit is 4-6 times the chord length, and the spacing between each group of horizontal rows is 0.25-0.3 times the chord length.

9. An energy harvesting method based on the oscillating hydrofoil airfoil optimized long-term self-sustaining energy harvesting device according to any one of claims 1-8, characterized in that: The method includes the following steps: 1) Multiple oscillating hydrofoil units are moored (3) to the seabed or riverbed and fixed in an array on the water surface; 2) When passing through the tidal current, the tidal current causes each oscillating hydrofoil unit to sway or roll on the water surface. The cross rollers (5) in the triboelectric nanogenerator (2) in each oscillating hydrofoil unit roll on the power generation substrate (6). The surfaces of roller I (7) and roller II (8) rub against each other, thereby generating surface charges. The surface of roller I (7) generates positive charges, and the surface of roller II (8) generates negative charges. The surface charges are induced by the electrostatic induction effect with the top layer (10) and interdigital electrodes (9) of the power generation substrate (6), so that the top layer (10) generates positive charges and the interdigital electrodes (9) generate negative charges. Combined with the reciprocating change of the relative positions of the top layer (10) and interdigital electrodes (9) and the cross rollers (5), electrons are driven to move back and forth in the circuit, thereby forming an alternating current signal. 3) The AC signal described in step 2 is converted into a DC signal by the diode bridge (13) and then transmitted to the lithium battery (12) to charge the lithium battery (12).

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