CN103856149B - A kind of integrated hybird environment energy collecting device - Google Patents

Abstract

The invention discloses an integrated mixed environment energy collection device, which comprises a plane square spiral rectifying antenna, a thin-film solar cell and a permanent magnet sheet. The planar square spiral rectenna includes a microstrip receiving antenna and a broadband rectifying and boosting circuit. The thin-film solar cells are directly attached to the upper and lower surfaces of the microstrip receiving antenna. The PCB board of the microstrip receiving antenna is hollow, and the permanent magnet sheet is located in the hollow position In the middle, and connected with the double-layer PCB board in four directions through non-metallic springs. The invention can collect radio frequency electromagnetic wave energy, solar energy and mechanical vibration energy at the same time, has the characteristics of low cost, small size, portability, and wide application environment, and can be applied to wireless sensor networks, RFID and other low-power electronic devices in various environments In order to get rid of the shackles of the battery.

Description

An integrated hybrid environment energy harvesting device

technical field

The invention belongs to the field of environmental energy collection, and in particular relates to an integrated mixed environmental energy collection device.

Background technique

Solar energy, radio frequency electromagnetic wave energy, and mechanical vibration energy are three ubiquitous environmental energy sources. The typical power of a solar cell illuminated by sunlight is on the order of mW. A typical thin-film solar cell receives 50-100 mW/cm ² of energy under direct sunlight. On cloudy days or indoors, the received power will drop to the μW level. Thin-film solar cells, such as hydrogenated amorphous silicon, typically have a conversion efficiency of 10-20% for light energy. Thin-film solar cells need to reduce material and manufacturing costs while improving conversion efficiency, which is the main challenge in the research and development of third-generation solar cells. In addition to efforts to research and develop low-cost and high-efficiency solar cells, efforts are also being made to improve the maximum power point tracking capability of low-power DC/DC converter systems to optimize the performance of solar harvesting systems.

The average power level of radio frequency electromagnetic waves in the environment is significantly lower compared to solar energy. The measurement results show that the maximum average power of radio frequency electromagnetic waves in the environment is 0.1-1 μW/cm ² . Since many low-power sensors operate in a wireless environment, this means they can be powered by harvesting radio-frequency electromagnetic wave energy, which requires the use of antennas. These antennas can not only be used in wireless communication, but also can be used to harvest radio frequency electromagnetic wave energy to power itself. In recent years, radio frequency wireless energy transmission has attracted more and more attention, and rectenna is one of the key technologies. The rectenna is composed of a receiving antenna, a filter circuit and a rectifier circuit. It receives electromagnetic waves in the environment and converts the received electromagnetic waves into DC power output. At present, there are mainly three forms of receiving antennas in rectennas: single-stage sub-antenna, dipole antenna and microstrip antenna. Microstrip antennas have been widely used in the design of receiving antennas in rectennas in recent years because of their small size, light weight, large receiving area, flexible polarization, convenient array formation, easy integration, and easy processing.

There are piezoelectric and electromagnetic induction working methods for mechanical vibration energy harvesting, both of which can obtain energy output from microwatts to milliwatts. The vibration energy harvester developed on the principle of electromagnetic induction has various structures and simple process, and can obtain a larger current than the piezoelectric energy harvester. The main problem of the electromagnetic induction energy harvester is that the power density is limited by the size of the permanent magnet, the number of coil turns and the process, and the output voltage is low, which requires a special voltage conversion circuit. Although electromagnetic induction energy harvesters have these inherent defects, with the advancement of technological conditions and the emergence of new electromagnetic energy conversion structures, in recent years, extensive research work has been carried out on vibration energy harvesting at home and abroad. This type of energy harvesting Device research has made great progress, and mature commercial products have emerged.

Common RFID antennas are mostly in the shape of a planar ring or a planar spiral, and the central area of the antenna is empty and has not been used. Therefore, it is considered to fix a permanent magnet sheet with a non-metallic spring in the center of the antenna. When the antenna vibrates, the permanent magnet sheet moves up and down, back and forth, left and right, and the spiral antenna loop cuts the magnetic induction line to generate a low-frequency alternating current. Magnetic induction phenomenon.

Because a single environmental energy is limited, such as a single radio frequency electromagnetic wave energy or mechanical vibration energy often cannot meet the energy supply requirements of wireless electronic equipment; The energy harvested by the battery will be significantly reduced, so a hybrid energy harvesting system is required to power wireless electronic devices. Combining thin-film solar cells and antennas will neither reduce the efficiency of thin-film solar cells nor reduce the radiation efficiency of antennas. This idea was first proposed in 1994 in the study of the energy supply of American spacecraft, and it was obtained in later research. further development. The invention integrates thin-film solar cells, vibration energy collectors and microstrip receiving antennas, so that the three energy-collecting modules can work simultaneously or individually, and the three energy conversion efficiencies will not interfere with each other. It effectively solves the energy supply problem of low-power wireless electronic devices when they work in various environments.

Contents of the invention

The purpose of the present invention is to provide an integrated mixed environment energy harvesting device, which can realize the energy supply of low-power electronic equipment such as wireless sensor network and RFID in various environments, so as to get rid of the shackles of batteries. The invention has low cost, small size, portability and is suitable for large-scale application.

In order to solve the above technical problems, the concrete technical scheme that the present invention adopts is as follows:

An integrated mixed environment energy harvesting device is characterized in that it includes: a plane square spiral rectenna, a thin-film solar cell and a permanent magnet sheet; the thin-film solar cell is covered on a hollow square ring-shaped double-layer PCB; the permanent magnet sheet is located on the The hollow position is connected to the double-layer PCB board in four directions through non-metallic elastic parts; the size of the permanent magnet sheet is smaller than the hollow size; the planar square spiral rectenna includes a microstrip receiving antenna and a broadband connected to the microstrip receiving antenna Composed of a rectifier boost circuit; the microstrip receiving antenna is a planar square spiral microstrip line, which is composed of a copper layer attached to the top layer of the PCB; the copper layer at the bottom of the PCB is the ground plane; the operating frequency of the microstrip receiving antenna is 2.4-2.5GHz ;

The broadband rectifier boost circuit is composed of diode D1, diode D2, capacitor C1, capacitor C2 and inductor L1; capacitor C1 and inductor L1 are connected in parallel to form a parallel element, one end of the parallel element is connected to the input end of the broadband rectifier boost circuit, and the other end is connected to the diode The anode of D1 and the cathode of diode D2; the cathode of diode D1 is grounded, the anode of diode D2 is connected to one end of capacitor C2 and then connected to the output end, and the other end of capacitor C2 is grounded; the capacitance of capacitor C1 is 1-10nF, and the capacitance of capacitor C2 is greater than 1μF; Since the capacitance of capacitor C1 is relatively small, it has a large capacitive reactance to the low-frequency alternating current generated by electromagnetic induction. Therefore, a suitable inductor L1 is connected in parallel with capacitor C1 to widen the working bandwidth and realize rectification and boosting of low-frequency signals.

Diode D1 and diode D2 are Schottky diodes; inductor L1 is a chip stack inductor.

The permanent magnet sheet is cylindrical. The elastic component is a non-metallic spring.

Working process of the present invention is as follows:

The microstrip receiving antenna is designed in a planar square spiral shape. The microstrip receiving antenna is composed of a double-layer metal dielectric plate. The antenna of the microstrip line structure is realized by the top copper layer, and the bottom copper layer is the ground plane. The center of the microstrip receiving antenna is hollow, and the dielectric board is a ring structure, that is, the whole board is hollow. Because the 2.45GHz ambient radio frequency electromagnetic wave energy is the strongest, the designed microstrip receiving antenna works at a center frequency of 2.45GHz. Firstly, the size of the microstrip receiving antenna is estimated according to the working frequency band of the microstrip receiving antenna, the dielectric constant of the medium, the thickness and other parameters, and then the layout of the microstrip receiving antenna is obtained through the ADS simulation optimization of Agilent, and the microstrip is made according to the scale of the layout Receive the actual antenna, then test and improve the actual object, and finally get the required microstrip receiving antenna.

Broadband rectifier boost circuit, for high-frequency electromagnetic wave signals, the inductor L1 can be regarded as an open circuit, when the input terminal voltage is 1V, when the upper is positive and the lower is negative; the diode D1 is turned on, the input voltage charges the capacitor C1, and the voltage polarity is left positive and right right Negative, the peak voltage of capacitor C1 can reach 1V; when the input terminal voltage is negative and positive, diode D1 is cut off, diode D2 is turned on, the input terminal voltage and capacitor C1 charge capacitor C2, the voltage polarity is positive and negative, and capacitor C2 The peak voltage can reach 2V. It can be seen that the output voltage is twice the input voltage, achieving the purpose of rectification and boosting. Since the capacitance value of capacitor C1 is 1-10nF, which is relatively small, the capacitive reactance of low-frequency signals generated by electromagnetic induction is very large. Therefore, an appropriate inductor L1 is connected in parallel at both ends of capacitor C1 to reduce reactance, widen the working bandwidth, and realize effective detection of low-frequency signals. Rectifier boost. Capacitor C2 should use an energy storage capacitor with a capacitance greater than 1 μF. Compared with the traditional rectifying and boosting circuit, the rectifying and boosting circuit takes into account the simultaneous rectification of low-frequency and high-frequency signals without increasing the layout size, effectively improving the bandwidth, and can achieve a wide frequency range from 20Hz-2.5GHz Work with range.

Direct conjugate matching is used between the broadband rectifier boost circuit and the microstrip receiving antenna. The traditional method is to use an impedance matching network between the rectifier boost circuit and the microstrip receiving antenna. This method will reduce the conversion efficiency of wireless energy . Direct conjugate matching can not only reduce the complexity of fabrication, but also suppress the re-radiation of high-order harmonics and improve conversion efficiency. Direct conjugate matching directly connects the diode and the microstrip receiving antenna on the PCB design, but the position of the welding point is the best position obtained through electromagnetic simulation optimization.

The permanent magnet sheet is located in the hollow position of the microstrip receiving antenna. When the hybrid environment energy harvesting device vibrates, the permanent magnet sheet can vibrate up and down relative to the microstrip receiving antenna, which is equivalent to the coil cutting the magnetic induction line, so that in the loop of the microstrip receiving antenna A low-frequency alternating current is generated, and a DC output is obtained after rectification. Since the frequency of the alternating current generated on the microstrip receiving antenna is very low, and the permanent magnet sheets and springs are non-metallic, it will hardly affect the effect of the microstrip receiving antenna to collect high-frequency electromagnetic wave signals.

The thin-film solar cell is directly pasted on the upper and lower surfaces of the microstrip receiving antenna. The selected amorphous silicon thin-film solar cell consists of a thin-film solar cell layer and two upper and lower glass substrate layers. The total thickness is the same as an A4 paper The thickness is about the same, the thickness is 50-150μm. The conversion efficiency of thin-film solar cells is 10-20%, and the energy received under direct sunlight is 50-100mW/cm ² , and the received power will drop to μW level in cloudy days or indoors. Thin-film solar cells can directly output direct current under light, which is very convenient to use.

The present invention has beneficial effects

In the present invention, the thin-film solar cell is directly pasted on the upper and lower surfaces of the microstrip receiving antenna, and the permanent magnet sheet is fixed in the hollow position of the microstrip receiving antenna so that it generates electricity magnetically when vibrating, without increasing the size of the environmental energy collection device. The collection of three different environmental energies: radio frequency electromagnetic wave energy, solar energy and mechanical vibration energy is integrated; through the coordinated design of the three energy collection modules, it is realized that according to different environmental conditions, the three energy collection modules can work at the same time or can be single work, the three energy conversion efficiencies will not interfere with each other; by connecting a suitable inductance L1 in parallel with the capacitor C1, the commonly used high-frequency rectification and boosting circuit is improved, the working bandwidth is widened, and the high-frequency electromagnetic wave and electromagnetic induction can be simultaneously controlled. The low frequency signal is rectified and boosted.

Description of drawings

Fig. 1 is a schematic block diagram of the present invention.

Fig. 2 is a top view of the present invention;

Fig. 3 is the sectional view of the center of the present invention;

Figure 4 is a cross-sectional view near the feeding edge of the microstrip receiving antenna;

Fig. 5 is a schematic diagram of a broadband rectifying and boosting circuit of the present invention.

In the figure: 1 thin-film solar cell, 2 polytetrafluoroethylene FR4, 3 microstrip receiving antenna, 4 non-metallic elastic parts, 5 permanent magnet sheet, 6 via hole, 7 feeder, 8 ground plane.

Detailed ways

As shown in Figure 1, an integrated mixed environment energy collection device of the present invention is composed of a thin-film solar cell, a microstrip receiving antenna, a broadband rectification and boosting circuit, and a vibration energy collection module. The output of the microstrip receiving antenna and the vibration energy collection module is connected to the broadband rectification and boosting circuit, the output of the broadband rectification and boosting circuit is connected to the power management module of the subsequent stage, and the output of the thin-film solar cell is directly connected to the power management module of the subsequent stage, and finally The first-level power management module outputs stable DC power.

The double-layer metal printed circuit board PCB is used as the manufacturing process, and the cross-sectional view of the PCB board is shown in Figure 4. As can be seen from the cross-sectional diagram, the microstrip receiving antenna has 3 layers, excluding the thin-film solar cell layer, the top layer and the bottom layer are made of copper, and the copper layer on the top layer is used as the microstrip receiving antenna to receive radiation signals in different frequency bands. Different; the bottom copper layer is the ground plane; the material of the middle layer is polytetrafluoroethylene FR4 as the medium. This constitutes a microstrip receiving antenna.

From the schematic diagram of the broadband rectifier boost circuit in Figure 5, the broadband rectifier boost circuit is composed of diode D1, diode D2, capacitor C1, capacitor C2, and inductor L1. Capacitor C1 and inductor L1 are connected in parallel to form a parallel element, and one end of the parallel element It is the input end of the broadband rectifier boost circuit, the other end of the parallel element is connected to the anode of the diode D1 and the cathode of the diode D2, the cathode of the diode D1 is grounded, the anode of the diode D2 is connected to one end of the capacitor C2 and then connected to the output end, and the other end of the capacitor C2 One end is grounded. Capacitor C1 and capacitor C2 use SMD capacitors with very low leakage. Capacitor C2 should use energy storage capacitors with a capacitance greater than 1 μF. Diode D1 and diode D2 use Schottky diodes, model HSMS-2852. Inductor L1 uses SMD stack layer inductance.

Both the microstrip receiving antenna and the broadband rectifying and boosting circuit are implemented with a microstrip line structure, and their physical dimensions are all obtained after calculation and simulation optimization by Agilent's ADS software. The medium of the double-layer PCB board is polytetrafluoroethylene FR4. The dielectric thickness is 1.6mm and the dielectric constant is 4.28.

Commonly used amorphous silicon thin-film solar cells are pasted on the front and back surfaces of the microstrip receiving antenna, as shown in Figure 3 and Figure 4. Thin-film solar cells can directly output direct current under light. In order to increase the output voltage, all thin-film solar cells are connected in series, and the output terminals are connected to a power management module.

Considering that the metal will affect the radiation field of the microstrip receiving antenna, the permanent magnet sheet is chosen to be non-metallic. The permanent magnet sheet has a certain weight, and is fixed in the hollow in the center of the microstrip receiving antenna by four non-metallic springs, as shown in Figure 2. When there is shaking, the permanent magnet sheet will vibrate up and down or back and forth with respect to the plane of the microstrip receiving antenna. The voltage circuit obtains a DC output.

Claims (3)

1. An integrated mixed environment energy harvesting device is characterized in that comprising: a plane square spiral rectenna, a thin-film solar cell and a permanent magnet sheet; a thin-film solar cell is covered on a hollow square annular double-layer PCB; the permanent magnet sheet Located in the hollow position of the square ring-shaped double-layer PCB board, and connected with the double-layer PCB board in four directions through non-metallic elastic parts; the size of the permanent magnet sheet is smaller than the hollow size; the planar square spiral rectenna includes a microstrip receiving The antenna is composed of a broadband rectifier boost circuit connected to the microstrip receiving antenna; the microstrip receiving antenna is a planar square spiral microstrip line, which is composed of a copper layer attached to the top layer of the PCB; the copper layer at the bottom of the PCB is the ground plane; the microstrip Working frequency with receiving antenna is 2.4-2.5GHz; The broadband rectifier boost circuit is composed of diode D1, diode D2, capacitor C1, capacitor C2 and inductor L1; capacitor C1 and inductor L1 are connected in parallel to form a parallel element, one end of the parallel element is connected to the input end of the broadband rectifier boost circuit, and the other end is connected to the diode The anode of D1 and the cathode of diode D2; the cathode of diode D1 is grounded, the anode of diode D2 is connected to one end of capacitor C2 and then connected to the output end, and the other end of capacitor C2 is grounded; the capacitance of capacitor C1 is 1-10nF, and the capacitance of capacitor C2 is greater than 1μF. 2 . The integrated hybrid environment energy harvesting device according to claim 1 , wherein the permanent magnet sheet is cylindrical. 3 . 3 . The integrated hybrid environment energy harvesting device according to claim 1 , wherein the elastic member is a non-metallic spring. 4 .