KR102528431B1 - Energy harvester - Google Patents

Abstract

The present invention relates to an energy harvesting device, and more particularly, to an energy harvesting device formed of a dual structure of an upper plate and a lower plate and capable of harvesting noise and vibration energy corresponding to a low frequency by a fixed end connecting the upper plate and the lower plate. it's about
An energy harvesting device according to an embodiment of the present invention includes a lower plate, an upper plate disposed to face the lower plate, and a plurality of fixing ends having both ends connected to the upper plate and the lower plate, respectively, to fix the upper plate and the lower plate. can do.
According to the present invention, by forming a fixed end for fixing the upper and lower plates, a band gap can be formed in the ultra-low frequency band, and by forming a wave concentrating portion on the upper plate, branches are formed in the band gap formed in the ultra-low frequency band. It has the advantage of being able to harvest energy using low frequencies.

Description

Energy harvester {Energy harvester}

The present invention relates to an energy harvesting device, and more particularly, to an energy harvesting device formed of a dual structure of an upper plate and a lower plate and capable of harvesting noise and vibration energy corresponding to a low frequency by a fixed end connecting the upper plate and the lower plate. it's about

Energy harvesting (Energy havesting) technology is a field that obtains energy by using the surrounding environment, a technology that converts the surrounding energy into electrical energy usable for driving a circuit. This technology allows the circuit to operate without a battery or without battery charging using a separate power source, so that it can be used as a power source or auxiliary power source for various sensors and communication devices using the same, and thus has a fairly wide range of applications.

As an energy harvesting technology, a method of obtaining energy from light in a natural environment using a solar cell is most widely known. However, in the case of a solar cell, there is a problem in that the efficiency of obtainable energy is very low and the fields to which it can be applied are limited because the required area is large.

In order to solve this problem, recently, energy is obtained through various methods, such as a method of obtaining energy using vibration or temperature difference, and a method of obtaining energy by receiving an electromagnetic wave signal using a millimeter (mm) antenna. Research to obtain is in progress.

In particular, a vibration-type energy harvesting technology that converts kinetic energy due to vibration into electrical energy is being actively developed. In this regard, Korean Patent Registration No. 10-1053257 (August 1, 2011, energy harvester) discloses an energy harvester capable of enhancing power output by adjusting a frequency bandwidth to include a plurality of natural frequencies.

However, there is still a problem in that the conventional vibration-type energy harvesting technology has low efficiency in the case of vibration having a low frequency.

KR 10-1053257 B1

In order to solve the above problems, an object of the present invention is to provide an energy harvesting device having a band gap in an extremely low frequency band through a fixed end for fixing the upper and lower plates.

As an embodiment of the present invention, an energy harvesting device is provided.

An energy harvesting device according to an embodiment of the present invention includes a top plate; and a plurality of fixing ends having one end connected to the top plate to fix the top plate.

The energy harvesting device according to an embodiment of the present invention may further include a lower plate disposed to face the upper plate, and the fixing end extending in the direction of the lower plate to fix the upper plate and the lower plate. can

The energy harvesting device according to an embodiment of the present invention further includes a top plate disposed to face the top plate, and the fixing end extends in the direction of the top plate to fix the top plate and the top plate. can be characterized.

The energy harvesting device according to an embodiment of the present invention may be characterized in that a plurality of unit units composed of a part of the top plate and a part of the fixed end are formed periodically.

The energy harvesting device according to an embodiment of the present invention may be characterized in that a band gap is generated in each of the unit units within a certain frequency range.

In the energy harvesting device according to an embodiment of the present invention, the upper plate may further include a wave concentrating unit in which waves incident to the upper plate are focused.

In the energy harvesting device according to an embodiment of the present invention, the wave collecting unit may have a shape different from that of the upper plate.

The energy harvesting device according to an embodiment of the present invention may further include an energy conversion element disposed in the wave collecting unit to generate a voltage using the wave.

In the energy harvesting device according to an embodiment of the present invention, the upper plate may be a phonon crystal.

According to the present invention, by forming a fixed end for fixing the upper and lower plates, there is an advantage in that a band gap can be formed in the ultra-low frequency band.

In addition, there is an advantage in that energy can be harvested using a low frequency by generating a branch in a band gap formed in an extremely low frequency band by forming a wave concentrating part on the upper plate.

Effects obtainable in the present disclosure are not limited to the effects mentioned above, and other effects not mentioned may be clearly understood by those skilled in the art from the description below. will be.

1 is a perspective view of an energy harvesting device according to an embodiment of the present invention.
2 is a perspective view of an energy harvesting device according to another embodiment of the present invention.
3 is an exemplary view of a unit body of an energy harvesting device according to an embodiment of the present invention.
4 is a diagram for explaining a band gap generated in a conventional energy harvesting device without a fixed end.
5 is a diagram for explaining a band gap generated in an energy harvesting device having a fixed end according to an embodiment of the present invention.
6 is an exploded view of an energy harvesting device according to another embodiment of the present invention.
7 is a diagram for explaining the principle of a wave concentrating unit of an energy harvesting device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice with reference to the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

The terms used in this specification will be briefly described, and the present invention will be described in detail.

The terms used in the present invention have been selected from general terms that are currently widely used as much as possible while considering the functions in the present invention, but these may vary depending on the intention of a person skilled in the art or precedent, the emergence of new technologies, and the like. In addition, in a specific case, there is also a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, not simply the name of the term.

When it is said that a certain part "includes" a certain component throughout the specification, it means that it may further include other components, not excluding other components unless otherwise stated. In addition, terms such as “~unit” and “module” described in the specification refer to a unit that processes at least one function or operation, and may be implemented as hardware or software or a combination of hardware and software. In addition, when a part is said to be "connected" to another part throughout the specification, this includes not only the case of being "directly connected" but also the case of being connected "through another element therebetween".

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view of an energy harvesting device according to an embodiment of the present invention.

Referring to FIG. 1 , an energy harvesting device according to an embodiment of the present invention includes an upper plate 100 and a fixed end 310, or includes an upper plate 100, a lower plate 200 and a fixed end 310. can be configured to include

The upper plate 100 and the lower plate 200 may be made of a single metal layer or a plurality of metal layers.

In addition, it is preferable that the upper plate 100 and the lower plate 200 are manufactured using stainless steel, but are not limited thereto, and copper (Cu), zinc (Zn), magnesium (Mg), aluminum (Al), iron ( Fe), tin (Sn), nickel (Ni) or bronze may be made of any one or more materials.

Depending on the embodiment, the lower plate 200 may be disposed to face the upper plate 100 .

Depending on the embodiment, the upper plate 100 may be a sonicator crystal.

At this time, the phononic crystal refers to an engineered artifact in which unit cells are periodically arranged, and means to have a wave singular phenomenon that does not exist in the natural world. The propagation direction of elastic waves can be controlled by using a phonon crystal.

One end of the fixing end 310 may be connected to the top plate 100 to fix the top plate 100 . Also, according to the embodiment, the fixing end 310 may extend in the direction of the lower plate 200 to fix the upper plate 100 and the lower plate 200 .

Depending on the embodiment, the fixing end 310 may be composed of an elastic body having a spring shape made of ferrous material. However, it is not limited thereto, and may be made of a material such as rubber, silicone, or latex, or may have a spiral, ball, pillar, or sponge shape.

Regarding the material and shape of the fixed end 310, various modifications are possible as long as the upper plate 100 and the lower plate 200 are fixed to move the band gap to the ultra-low frequency band.

The principle of generating the band gap and the movement of the band gap to the ultra-low frequency band by the fixing ends 310 and 320 will be described with reference to FIGS. 4 and 5 below.

2 is a perspective view of an energy harvesting device according to another embodiment of the present invention.

Referring to FIG. 2 , the energy harvesting device according to an embodiment of the present invention may further include a top plate 400 .

The top plate 400 is disposed to face the top plate 100, and at this time, the fixing end 320 extends in the direction of the top plate 400 to fix the top plate 100 and the top plate 400.

At this time, the top plate 400 may be made of a single metal layer or a plurality of metal layers, and it is preferable to be made of stainless steel, but it is not limited thereto, and copper (Cu), zinc (Zn), magnesium ( Mg), aluminum (Al), iron (Fe), tin (Sn), nickel (Ni), or may be made of any one or more materials of bronze.

3 is an exemplary view of a unit body of an energy harvesting device according to an embodiment of the present invention.

Referring to FIG. 3 , the energy harvesting device according to an embodiment of the present invention may be characterized in that a plurality of unit units composed of a part of the top plate 100 and parts of the fixed ends 310 and 320 are formed periodically. At this time, the periodic formation of a plurality of units means including the formation of a plurality of units continuously.

For example, as shown in FIG. 3(a), in one unit body, a portion of the top plate 100 having a circular hole formed therein and 1/4 of the pillar-shaped fixed ends 310 and 320 are of the unit body. It can be specified as being formed at each corner.

Alternatively, as shown in FIG. 3 (b), a portion of the top plate 100 without a circular hole inside and 1/4 of the pillar-shaped fixed ends 310 and 320 are formed at each corner of the unit body. The unit of can be specified.

According to the embodiment, as shown in FIG. 3(c), a part of the top plate 100 without a circular hole inside and a fixed end 310, 320 having a column shape are formed in the center of the unit body, and one unit body may be specified.

Regarding the shape of one unit constituting the energy harvesting device according to the present invention, the shapes of FIGS. 3(a) to 3(c) described above should be understood as illustrative, but not limited thereto.

Depending on the embodiment, a band gap may be generated in each unit within a certain frequency range.

4 is a diagram for explaining a band gap generated in a conventional energy harvesting device without fixed ends 310 and 320, and FIG. 5 is an energy harvesting device with fixed ends 310 and 320 according to an embodiment of the present invention. It is a diagram for explaining the band gap generated in the device.

The band gap is one of the typical wave singular phenomena of acoustic crystals that do not allow waves of a specific frequency band to pass through. The energy level or energy difference between the top of the higher energy band and the bottom of the lowest space band.

FIG. 4(a) is a schematic diagram of a state in which each unit unit is connected by a spring in an energy harvesting device without fixed ends 310 and 320.

If the structure of the upper plate 100 is assumed to be an infinite mass-spring chain, the equation of motion for the n-th unit body is as shown in Equation 1 below.

은 질량,

은 스프링 상수,

,

,

은 각각 n-1번째, n번째, n+1번째 단위체의 변위를 의미한다.here,

silver mass,

is the spring constant,

,

,

Means the displacement of the n-1th, nth, and n+1th units, respectively.

Since the upper plate 100 has a structure in which units of the same shape are repeated, according to the Bloch wave, the wave function of each unit unit can be expressed as in Equation 2 below.

는 초기 파동이 입사할 때의 진폭,

와

는 각각 파동의 주파수 및 파수,

는 시간,

는 단위체 사이의 간격이다.here,

is the amplitude at which the initial wave is incident,

and

are the frequency and wavenumber of the wave respectively,

time,

is the spacing between the units.

The wave functions of the n-1th and n+1th units in Equation 2 can be expressed as the wavefunctions of the nth unit as shown in Equation 3 below.

Substituting the wave function of the n-th unit body in Equation 2 and the wave functions of the n-1th and n+1-th unit bodies in Equation 3 into the motion equation of Equation 1, and arranging the equation, the wave function as shown in Equation 4 below The variance equation can be derived.

로 나누고, 각 단위체의 고유진동수를(

)를

으로 정의하고,

는

로 정의하면 하기 수학식 5가 도출된다.In order to normalize Equation 3 above,

Divided by , and the natural frequency of each unit (

)cast

defined as,

Is

When defined as Equation 5 below is derived.

를 0부터

까지 변형시키면서 대응되는

를 그린 그래프이다.Figure 4 (c) is the expression of Equation 4

from 0

Corresponding while transforming to

is a graph drawn by

가 0일 때는

이고,

가

일때는

이 된다. 즉, 도 3(a)에 도시된 바와 같이 고정단(310, 320)이 없는 구조를 갖는 에너지 수확장치에서는 주파수가 2.0보다 큰 파동이 입사한 경우 파동이 진행할 수 없는 밴드갭이 형성된다.in Equation 4

is 0

ego,

go

at times

becomes That is, in the energy harvesting device having a structure without fixed ends 310 and 320 as shown in FIG. 3 (a), when a wave having a frequency greater than 2.0 is incident, a band gap is formed in which the wave cannot propagate.

FIG. 5(a) is a schematic diagram of a state in which each unit unit is additionally connected to the fixed ends 310 and 320 by a spring in the energy harvesting device without the fixed ends 310 and 320 of FIG. 4(a).

Similarly, in the energy harvesting device having the fixed ends 310 and 320, when the structure of the top plate 100 is assumed to be an infinite mass-spring chain, the equation of motion for the nth unit body is as shown in Equation 6 below.

) 효과가 추가적으로 나타나는 점에서 차이점을 갖는다.3(b) and 4(b), the equation of motion in the energy harvesting device with fixed ends 310 and 320 is different from the equation of motion in the energy harvesting device without fixed ends 310 and 320. The parts are the same, and the springs connected to the fixed ends 310 and 320 (

) has a difference in that the effect appears additionally.

Since the same structure is repeated in the energy harvesting device having the fixed ends 310 and 320, according to Bloch's theorem, the wave function of each unit body can be expressed as Equation 7 below.

Similarly, by substituting the wave function of each unit in Equation 7 into the equation of motion of Equation 6, and arranging, the wave dispersion equation of Equation 8 below can be derived.

When Equation 8 is normalized, the wave dispersion equation shown in Equation 9 below appears.

은

를 나타낸다.here,

silver

indicates

에 대해

의 값이

만큼 증가한다.That is, compared to the energy harvesting device without the fixed ends 310 and 320, the wave dispersion equation of the energy harvesting device with the fixed ends 310 and 320 has the same wave number.

About

the value of

increase as much as

를 0부터

까지 변형시키면서 대응되는

를 그래프로 도시한 것이다.5(c) shows Equation 9

from 0

Corresponding while transforming to

is shown graphically.

가 0일 때는

이고,

가

일때는

이 되므로, 도 4(c)에 도시된 바와 같이 고정단(310, 320)이 있는 에너지 수확장치에서는 밴드 갭이

만큼 평행이동하여 극저주파 대역에 밴드 갭이 생성되는 것이다.in Equation 9

is 0

ego,

go

at times

Therefore, as shown in FIG. 4 (c), in the energy harvesting device having fixed ends 310 and 320, the band gap is

By moving in parallel by the amount of time, a band gap is created in the ultra-low frequency band.

이고, 차단대역(stop band)이

인 반면, 고정단(310, 320)이 있는 경우에는 통과대역이

이고 차단대역이

,

이다.That is, when there are no fixed ends 310 and 320, the pass band is

, and the stop band is

On the other hand, when there are fixed ends 310 and 320, the pass band is

and the cut-off band is

,

am.

6 is an exploded view of an energy harvesting device according to another embodiment of the present invention.

Referring to FIG. 6 , in the energy harvesting device according to an embodiment of the present invention, the top plate 100 may further include a wave concentrating unit 110 in which waves incident on the top plate 100 are focused. .

Depending on the embodiment, the wave concentrating part 110 may have a shape different from that of the upper plate 100 . That is, the wave concentrating unit 110 may mean any one unit having a different shape among a plurality of units constituting the upper plate 100 .

For example, as shown in FIG. 6 (a), the wave concentrating unit 110 has a shape that is not fixed to the lower plate 200 or the upper plate 400 by the fixing ends 310 and 320, thereby fixing It may have a different shape from the upper plate 100 fixed to the lower plate 200 or the upper plate 400 by the steps 310 and 320.

Alternatively, as shown in FIG. 6(b), in the upper plate 100 in which a plurality of units having circular holes formed therein are periodically formed, circular holes are not formed inside the shape of the wave concentrating part 110. It will be possible to have a difference from the shape of the top plate 100 by forming it as a non-unit unit.

An energy harvesting device according to an embodiment of the present invention may further include an energy conversion device.

The energy conversion element is disposed in the wave collecting unit 110 and generates a voltage using a wave. At this time, the energy conversion element means a configuration having an effect of generating a voltage when deformed by stress, and a piezo element (piezoelectric element) may be applied as a representative example.

When a piezo element is used, a monomorph type in which a piezoelectric element is disposed on only one side of the wave collecting unit 110 may be used, or a bimorph type in which a piezoelectric element is respectively disposed on both sides of the wave collecting unit 110 may be used.

Also, according to an embodiment, the wave concentrating unit 110 may be formed at only one point or at a plurality of points of the upper plate 100 .

7 is a diagram for explaining the principle of the wave concentrating unit 110 of the energy harvesting device according to an embodiment of the present invention.

FIG. 7(a) shows a frequency band that can be obtained from phononic crystals when the shapes of a plurality of units forming the top plate 100 are all the same, and FIG. 6(b) shows a plurality of units forming the top plate 100. It is a frequency band that can be obtained from phononic crystals when any one of them is different in shape.

As shown in FIG. 7(b), when the shape of any one of the units constituting the upper plate 100 is designed differently (ie, when the wave concentrating part 110 is formed on the upper plate 100) Since the periodicity between the units is locally destroyed, branches (i.e. defect bands) are generated in the band gap.

At this time, when a wave having a frequency corresponding to the branch is applied to the upper plate 100, the energy harvesting performance is ultimately improved because the wave energy is localized near the wave focusing unit 110.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention. do.

100: top plate
110: wave focusing unit
200: lower plate
310, 320: fixed end
400: top plate

Claims (13)

top plate; and
One end is connected to the top plate to include a plurality of fixing ends for fixing the top plate,
An energy harvesting device, characterized in that a plurality of units composed of a part of the upper plate and a part of the fixed end are formed periodically.
According to claim 1,
Further comprising a lower plate disposed to face the upper plate,
The energy harvesting device, characterized in that the fixing end extends in the direction of the lower plate to fix the upper plate and the lower plate.
According to claim 1,
Further comprising a top plate disposed to face the top plate,
The energy harvesting device, characterized in that the fixing end extends in the direction of the top plate to fix the top plate and the top plate.
delete According to any one of claims 1 to 3,
Energy harvesting device, characterized in that a band gap is generated in each unit within a certain frequency range.
top plate; and
One end is connected to the top plate and includes a plurality of fixing ends for fixing the top plate,
The top plate,
The energy harvesting device further comprises a wave concentrating unit in which the waves incident on the upper plate are focused.
According to claim 6,
Further comprising a lower plate disposed to face the upper plate,
The energy harvesting device, characterized in that the fixing end extends in the direction of the lower plate to fix the upper plate and the lower plate.
According to claim 6,
Further comprising a top plate disposed to face the top plate,
The energy harvesting device, characterized in that the fixing end extends in the direction of the top plate to fix the top plate and the top plate.
According to any one of claims 6 to 8,
The wave collecting unit,
Energy harvesting device characterized in that it has a different shape from the unit constituting the upper plate.
According to any one of claims 6 to 8
The energy harvesting device further includes an energy conversion element disposed in the wave concentrating unit to generate a voltage using the wave.
top plate; and
One end is connected to the top plate and includes a plurality of fixing ends for fixing the top plate,
The top plate,
An energy harvesting device characterized in that it is a sonic crystal.
According to claim 11,
Further comprising a lower plate disposed to face the upper plate,
The energy harvesting device, characterized in that the fixing end extends in the direction of the lower plate to fix the upper plate and the lower plate.
According to claim 11,
Further comprising a top plate disposed to face the top plate,
The energy harvesting device, characterized in that the fixing end extends in the direction of the top plate to fix the top plate and the top plate.

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