AU2021101345A4

AU2021101345A4 - Multi-mode hybrid up-conversion vibration-type ambient energy harvester

Info

Publication number: AU2021101345A4
Application number: AU2021101345A
Authority: AU
Inventors: Chunhui GAO; Shiqiao GAO; Lei Jin; Zezhang LI; Haipeng Liu; Shigang PENG
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-03-16
Filing date: 2021-03-16
Publication date: 2021-05-13
Anticipated expiration: 2029-03-16

Abstract

The present disclosure belongs to the technical field of micro energy and vibration power generation, and discloses a multi-mode hybrid up-conversion vibration-type ambient energy 5 harvester. The energy harvester comprises a housing, an electromagnetic energy harvesting unit, a piezoelectric energy harvesting unit and an electrostatic energy harvesting unit, wherein a low-frequency vibration beam and a high-frequency beam are connected to the housing, and the low-frequency vibration beam is located above the high-frequency beam; the low-frequency vibration beam is connected with the electromagnetic energy harvesting unit, the piezoelectric 0 energy harvesting unit and the electrostatic energy harvesting unit share the high-frequency beam, the electrostatic energy harvesting unit is located on the bottommost layer of the housing, and the piezoelectric energy harvesting unit is located between the electromagnetic energy harvesting unit and the electrostatic energy harvesting unit. The energy harvesting structures of three different energy harvesting units, that is, an electrostatic energy harvesting unit, a 5 piezoelectric energy harvesting unit and an electromagnetic energy harvesting unit, are scientifically and reasonably arranged, so that the energy harvesting bandwidth can be effectively widened, the energy output level of the energy harvesting structures is improved, and the environment adaptability of the energy harvester is enhanced. 9 DRAWINGS 89 42 6 5 10 FIG. 1

Description

DRAWINGS

89 42 6

5

10

FIG. 1

MULTI-MODE HYBRID UP-CONVERSION VIBRATION-TYPE AMBIENT ENERGY HARVESTER

TECHNICAL FIELD The present disclosure belongs to the technical field of micro energy and vibration power generation, and particularly relates to a multi-mode hybrid up-conversion vibration-type ambient energy harvester.

BACKGROUND With the rapid development of MEMS and CMOS sensors and the rapid improvement of data processing capabilities, people have entered the era of Internet of Everything. Wireless sensor networks will be widely used in defense and military affairs, smart cities, intelligent manufacturing, automatic driving, environmental protection and other fields. A large number of low-power sensors are used in wireless sensor networks, which require less energy, and can work normally with tens or even a few microwatts. For those wireless sensor networks in unattended or closed environments, it is a problem to realize long-term independent power supply of sensors in the future. At present, the power supply of sensors still depends on the traditional chemical battery, which is large in size, limited in life, unable to be stored for a long time, and needs to be replaced regularly, resulting in a waste of a lot of labor costs. Chemical batteries cannot be monolithically integrated with MEMS sensors, which limits the application of chemical batteries in MEMS sensors. Therefore, the new power supply technology for supplying energy to a micro electro mechanical system and a low-power electronic device has become a key technical problem to be solved urgently. It is an effective way to solve the above problems to convert the ambient energy in the natural environment into electric energy to supply power to the sensor, which has practical significance and great economic benefits for promoting the application and development of wireless sensor networks. At the same time, it also promotes people to explore new ways of obtaining energy. At present, many ways to obtain limited electric energy from the ambient environment have been studied at home and abroad, mainly including solar cells, thermoelectric cells, wind turbines and so on. These power generation methods can effectively convert the energy in the natural environment into electric energy to supply power for low-power devices, but they are also limited by the ambient environment in practical applications. For example, solar cells and thermoelectric cells have strict requirements on the light and temperature in the working environment, and cannot work in a closed ambient environment. Wind turbines are large in size and have high requirements on wind speed, which limits their application to a great extent. Vibration in the ambient environment is in everywhere and at every time. Compared with solar energy, thermal energy and other energy sources, vibration energy is relatively large in energy density. In recent years, the research of vibration energy harvester which can convert the ambient vibration energy into electric energy has become a frontier hot spot, which is used to convert the vibration mechanical energy in the working environment of low-power electronic devices such as wireless sensors into electric energy and effectively collect the electric energy to supply power for low-power electronic devices such as wireless sensors or micro electro mechanical systems. At present, vibration energy harvesting methods include piezoelectric energy harvesting, electromagnetic energy harvesting and electrostatic energy harvesting. Because the prior art mostly uses separate energy harvesting methods, it is easy to cause the problem that it is insufficient to output voltage and current at the same time.

SUMMARY In view of the problems existing in the prior art, the present disclosure provides a multi-mode hybrid up-conversion vibration-type ambient environment energy harvester, in which the energy harvesting structures of three different energy harvesting units, that is, an electrostatic energy harvesting unit, a piezoelectric energy harvesting unit and an electromagnetic energy harvesting unit, are scientifically and reasonably arranged, so that the energy harvesting bandwidth can be effectively widened, the energy output level of the energy harvesting structures is improved, and the environment adaptability of the energy harvester is enhanced. According to the basic scheme of the present disclosure, a multi-mode hybrid up-conversion vibration-type ambient environment energy harvester comprises a housing, an electromagnetic energy harvesting unit, a piezoelectric energy harvesting unit and an electrostatic energy harvesting unit, wherein a low-frequency vibration beam and a high-frequency beam are connected to the housing, and the low-frequency vibration beam is located above the high-frequency beam; the low-frequency vibration beam is connected with the electromagnetic energy harvesting unit, the piezoelectric energy harvesting unit and the electrostatic energy harvesting unit share the high-frequency beam, the electrostatic energy harvesting unit is located on the bottommost layer of the housing, and the piezoelectric energy harvesting unit is located between the electromagnetic energy harvesting unit and the electrostatic energy harvesting unit. Further, the electromagnetic energy harvesting unit comprises a magnetic mass block and a coil, the magnetic mass block is connected to the free end of the low-frequency vibration beam, and the coil is provided on the inner wall of the housing. Further, the magnetic mass block is a rectangular magnet. Further, the coil adopts a multilayer planar structure. Further, the electrostatic energy harvesting unit comprises a lower electrode, an electret film and an upper electrode, the lower electrode is fixed on the bottom surface of the housing, the electret film is provided on the surface of the lower electrode, and the upper electrode is provided on the lower surface of the high-frequency beam. Further, an insulating film is provided between the upper electrode and the piezoelectric energy harvesting unit. Further, the electret film is adhered to the surface of the lower electrode through a double-sided conductive adhesive. Further, the piezoelectric energy harvesting unit comprises a piezoelectric plate, and the piezoelectric plate is provided on the upper surface of the high-frequency beam. Compared with the prior art, the present disclosure has the following beneficial effects. 1. In order to effectively convert ambient vibration energy into electric energy, multiple energy conversion modes are combined to complete the collection of ambient vibration energy at the same time, and the ambient vibration energy conversion can be completed to the greatest extent. Using piezoelectric-electromagnetic-electrostatic hybrid energy harvester can effectively expand bandwidth, reduce energy harvesting frequency, improve energy harvesting efficiency, and realize efficient multi-mode energy conversion. Because the ambient vibration is mostly low-frequency vibration and the frequency variation range is wide, the vibration frequency of the energy harvesting structure is effectively reduced and the bandwidth of the energy harvesting structure is increased. 2. The present disclosure constitutes an up-conversion structure, which can effectively utilize the ambient low-frequency vibration energy and enhance the environmental adaptability of the energy harvesting structure. 3. The low-frequency vibrating beam realizes nonlinear vibration due to the interaction of electromagnetic induction between magnets and coils, which can effectively widen the low-frequency energy harvesting bandwidth. 4. In the present disclosure, magnets are used as magnetic mass blocks of low-frequency vibrating beams, which collide with high-frequency beams during vibration to generate high-frequency vibration, thus realizing high-efficiency energy conversion under the condition of high-frequency vibration of piezoelectric materials. 5. The piezoelectric-electromagnetic-electrostatic hybrid energy harvester provided by the present disclosure can effectively make up for the deficiency of the single energy harvesting mode, achieve the simultaneous output of higher voltage and higher current, and is more conducive to charging rechargeable batteries or super-capacitors. 6. In the limited space, a piezoelectric plate and an electret are used to harvest energy together, and at the same time, electromagnetic induction between a magnet and a coil is used to harvest energy, thus realizing various energy harvesting modes in the limited space, which can effectively improve energy harvesting efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural schematic diagram provided by an embodiment of a multi-mode hybrid up-conversion vibration-type ambient energy harvester according to the present disclosure.

DETAILED DESCRIPTION In order to make the purpose, the technical scheme and the advantage of the present disclosure clearer, the present disclosure will be further described in detail with reference to the embodiment hereinafter. It should be understood that the specific embodiments described herein are only used to explain the present disclosure, and are not used to limit the present disclosure. The application principle of the present disclosure will be further described with reference to the attached drawings and specific embodiments. The reference numerals in the attached drawings of the specification comprise: housing 1, low-frequency vibration beam 2, high-frequency beam 3, fixing bolt 4, electromagnetic energy harvesting unit 5, magnetic mass block 6, coil 7, piezoelectric energy harvesting unit 8, piezoelectric plate 9, electrostatic energy harvesting unit 10, electret film 11. The embodiment is based on the multi-mode hybrid up-conversion vibration-type ambient energy harvester shown in FIG. 1, which comprises a housing 1, an electromagnetic energy harvesting unit 5, a piezoelectric energy harvesting unit 8 and an electrostatic energy harvesting unit 10. The left side of the housing 1 is connected with a low-frequency vibration beam 2 and a high-frequency beam 3 through a fixing bolt 4, and the low-frequency vibration beam 2 is located above the high-frequency beam 3. The low-frequency vibration beam 2 is connected with an electromagnetic energy harvesting unit 5. The electromagnetic energy harvesting unit 5 comprises a magnetic mass block 6 and a coil 7 provided on the magnetic mass block 6. The magnetic mass block 6 is a rectangular magnet 6. The magnetic mass block 6 is connected to the free end of the low-frequency vibration beam 2. The coil 7 adopts a multilayer planar structure, and the coil 7 with the multilayer planar structure is provided on the inner wall of the housing 1. The rectangular magnet 6 is used as the magnetic mass block 6 of the low-frequency vibration beam 2, which collides with the high-frequency beam 3 in the low-frequency vibration so that the high-frequency beam 3 generates high-frequency vibration. The rectangular magnet 6 can reduce the inherent frequency of the low-frequency vibration beam 2, and at the same time provide a variable magnetic field for the electromagnetic vibration energy harvesting unit. The piezoelectric energy harvesting unit 8 and the electrostatic energy harvesting unit 10 share the high-frequency beam 3. The electrostatic energy harvesting unit 10 is located on the bottommost layer of the housing 1, and the piezoelectric energy harvesting unit 8 is located between the electromagnetic energy harvesting unit 5 and the electrostatic energy harvesting unit 10. Specifically, the piezoelectric energy harvesting unit 8 comprises a piezoelectric plate 9. The piezoelectric plate 9 is made of piezoelectric ceramic material, and the piezoelectric plate 9 is adhered to the upper surface of the high-frequency beam 3. The electrostatic energy harvesting unit 10 comprises a lower electrode, an electret film 11 and an upper electrode. The lower electrode is fixed on the bottom surface of the housing 1. The electret film 11 is adhered to the surface of the lower electrode through a double-sided conductive adhesive. The upper electrode is adhered to the lower surface of the high-frequency beam 3. In order to avoid mutual interference between the output voltages of the piezoelectric energy harvesting unit 8 and the electrostatic energy harvesting unit 10, the upper electrode of the electrostatic energy harvesting unit 10 is isolated from the piezoelectric energy harvesting unit 8 by an insulating film. The present disclosure is used for converting vibration mechanical energy in the working environment of low-power electronic devices such as wireless sensors into electric energy and effectively collecting the electric energy to supply power for low-power electronic devices such as wireless sensors or micro electro mechanical systems. According to the energy harvesting mechanism of three different energy harvesting units, that is, an electrostatic energy harvesting unit, a piezoelectric energy harvesting unit and an electromagnetic energy harvesting unit, based on the up-conversion structure, the three different energy harvesting structures are scientifically and reasonably arranged without increasing the volume of a single electret electrostatic energy harvesting unit 10, so as to improve the overall energy harvesting efficiency of the energy harvester. In this scheme, the frequency of a vibration beam used for energy conversion is increased by the up-conversion structure. In this scheme, the inherent frequency of the high-frequency beam 3 with a piezoelectric plate is higher, but the environmental frequency is lower. The low-frequency vibration beam 2 is used to strike the high-frequency beam 3, the high-frequency beam 3 generates free vibration with higher frequency, thus increasing the frequency so that the piezoelectric energy harvesting unit 8 obtains higher energy output. The output of the electrostatic energy harvesting unit 10 and the piezoelectric energy harvesting unit 8 has the characteristics of large voltage and small current, while the output of the electromagnetic energy harvesting unit 5 has the characteristics of small voltage and large current. The energy harvester based on the vibration structure (whether it is an electrostatic energy harvester, a piezoelectric energy harvester or an electromagnetic energy harvester) depends on the vibration unit. Therefore, combining the electrostatic energy harvester 10, the piezoelectric energy harvester 8 and the electromagnetic energy harvester 5 on the basis of the same vibration unit can obtain both large voltage and large current without increasing the volume. Each energy harvester has complementary advantages and improves the overall energy harvesting efficiency of the energy harvester. Introducing an up-conversion structure based on a linear vibration structure can not only reduce the environmental sensitive frequency of the multi-mode hybrid up-conversion vibration energy harvester, but also widen the energy harvesting frequency band of the multi-mode hybrid up-conversion vibration energy harvester. The above is only a preferred embodiment of the present disclosure, rather than limit the present disclosure. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

Claims WHAT IS CLAIMED IS:

1. A multi-mode hybrid up-conversion vibration-type environment energy harvester, comprising a housing (1), an electromagnetic energy harvesting unit (5), a piezoelectric energy harvesting unit (8) and an electrostatic energy harvesting unit (10), wherein a low-frequency vibration beam (2) and a high-frequency beam (3) are connected to the housing (1), and the low-frequency vibration beam (2) is located above the high-frequency beam (3); the low-frequency vibration beam (2) is connected with the electromagnetic energy harvesting unit (5), the piezoelectric energy harvesting unit (8) and the electrostatic energy harvesting unit (10) share the high-frequency beam (3), the electrostatic energy harvesting unit (10) is located on the bottommost layer of the housing (1), and the piezoelectric energy harvesting unit (8) is located between the electromagnetic energy harvesting unit (5) and the electrostatic energy harvesting unit (10).

2. The multi-mode hybrid up-conversion vibration-type ambient energy harvester according to claim 1, wherein the electromagnetic energy harvesting unit (5) comprises a magnetic mass block (6) and a coil (7), the magnetic mass block (6) is connected to the free end of the low-frequency vibration beam (2), and the coil (7) is provided on the inner wall of the housing

(1);

wherein the magnetic mass block (6) is a rectangular magnet;

wherein the coil (7) adopts a multilayer planar structure.

3. The multi-mode hybrid up-conversion vibration-type ambient energy harvester according to any one of claims 1-2, wherein the electrostatic energy harvesting unit (10) comprises a lower electrode, an electret film (11) and an upper electrode, the lower electrode is fixed on the bottom surface of the housing (1), the electret film (11) is provided on the surface of the lower electrode, and the upper electrode is provided on the lower surface of the high-frequency beam (3).

4. The multi-mode hybrid up-conversion vibration-type ambient energy harvester according to claim 3, wherein an insulating film is provided between the upper electrode and the piezoelectric energy harvesting unit (8);

wherein the electret film (11) is adhered to the surface of the lower electrode through a double-sided conductive adhesive.

5. The multi-mode hybrid up-conversion vibration-type ambient energy harvester according to any one of claims 1-2, wherein the piezoelectric energy harvesting unit (8) comprises a piezoelectric plate (9), and the piezoelectric plate (9) is provided on the upper surface of the high-frequency beam (3).

FIG. 1 DRAWINGS