China’s "double carbon" strategy advocates a green, environmentally friendly and low-carbon lifestyle, which depends on the continuous development and innovation of green energy technology. At the moment when China is vigorously developing renewable energy, the recovery and reuse of micro-energy in real environment such as magnetic energy has attracted the attention of many researchers.

　　Chu Zhaoqiang, a young teacher and associate professor of the Underwater Acoustic Engineering College of Harbin Engineering University and the "Marine Magnetic Sensor and Detection" team of the Innovation and Development Base, has researched and designed a new structure of weak magnetic energy collector, which can make the sensor of the Internet of Things avoid all kinds of manual and tedious operations such as battery replacement and maintenance, and realize "self-power generation" under weak magnetic conditions, and its output power is about 120% higher than that of the traditional structure. Recently, the research academic paper "Significantly enhanced weak magnetic energy recovery performance in magnetic-mechanical-electric energy capture devices with two ends clamped" was published online in the internationally renowned journal Advanced Energy Materials in the field of energy materials.

　　Recovery and reuse of micro-energy in the environment

　　"Internet of Everything" is an important engine to build an intelligent world, and it also gives birth to the rapid development of Internet of Things technology. At present, a major challenge in developing the Internet of Things is to find the self-powered technology of sensor communication nodes to support the construction of large-scale and distributed sensor networks.

　　In view of this technical challenge, many fields in China are actively planning ways to solve it. In 2021, the national key R&D plan "Smart Sensor" focused on the problem of self-powered access to the network for multi-parameter biosensors of human body in wireless scenes, and put forward the self-powered technology for obtaining energy from human body. In 2022, the national key R&D plan "Smart Sensor" focused on the problem of power supply and network access of distributed sensors with state awareness in distribution network, and proposed the project guide of magnetoelectric coupling self-powered magnetic field sensitive components and sensors; In 2022, the National Natural Science Foundation of China also included the micro piezoelectric vibration energy harvesting technology for aerospace into the scope of the guide.

　　It can be said that the development of distributed energy acquisition technology to realize the recycling of micro-energy in the environment is of great value, and it is also an effective measure to respond to the national energy conservation and emission reduction strategy and help peak carbon dioxide emissions.

　　For the recycling of environmental micro-energy, among many collectable energy sources, such as vibration energy, radiation energy and near-field electromagnetic energy, stray magnetic energy generated by power cables, industrial machinery and household appliances has been paid more attention by researchers because of its fixed frequency and wide distribution, which is more efficient than low-frequency energy such as wind energy. Especially in the context of building smart grid, it is urgent to capture energy from overhead cables and build a sustainable self-powered sensor network for on-line monitoring and fault diagnosis of transmission line state parameters.

　　Just like the beautiful new world described in the novel "Three-body", the cup can heat itself without power supply and battery, but the flying car in the air can fly without battery, and there will never be no electricity, all because the power supply uses microwave or other forms of electromagnetic vibration to generate electricity and form a wireless power supply field. This technology is actually the technology currently used for wireless charging of mobile phones. At first, people also turned their attention to this traditional coil induction power taking device. However, this technology has some outstanding problems, such as large volume, inconvenient installation and difficult to withstand short-term heavy current impact.

　　Therefore, people began to study an energy harvesting device that converts magnetic energy into mechanical energy and then into electrical energy (MME). This technology is expected to become a new choice for the next generation of low-frequency magnetic field energy collection.

　　According to Chu Zhaoqiang, this new type of energy harvesting device uses the magnetic torque effect and hysteresis expansion effect, and then uses the piezoelectric effect to realize the conversion between mechanical energy and electrical energy. Its advantage is that it does not need the closed magnetic circuit required by the coil induction device, and it can achieve higher efficiency of energy conversion and higher tolerance to strong current pulses.

　　A new method for low-field energy collection

　　Chu Zhaoqiang began to contact vibration and magnetic field energy collection technology in 2016. From 2016 to 2021, we have been committed to the research of materials and devices based on the traditional cantilever resonant structure. This is an energy collector structure with one end fixed and the other end free, and a mass (magnet) is attached to the free end. This structure provides the driving torque by the free-end magnetic mass, and at the same time contributes more than 90% equivalent mass. In this case, if the resonant frequency of the resonator is to be kept constant at 50 Hz, it is difficult to enhance the magnetic-mechanical coupling performance simply by increasing the mass of the free-end magnet. It is precisely for this reason that most of the cantilever magnetic-mechanical-electrical devices studied at present are only limited to the energy collection of strong magnetic fields, that is, magnetic fields greater than 5 Oe. The World Health Organization points out that the safety threshold of 50/60Hz alternating magnetic field accessible to the public is 1Oe, and the magnitude of stray magnetic field in the environment is generally lower than this reference value. Therefore, it is necessary to explore new principles and methods suitable for low-field energy collection.

　　Based on the thinking of "how to reduce the equivalent mass of free-end magnetic mass block by magnetic-mechanical-electric energy harvesting devices", Chu Zhaoqiang boldly innovated and put forward a design idea of clamping beams at both ends. This design makes both ends of the magnetic-mechanical-electric energy harvesting device fixed, and adopts a second-order vibration mode, which reduces the kinetic energy of the central magnetic mass, thus reducing its contribution to the equivalent mass of the resonant system, and greatly improving the output performance of the system under the condition of increasing the magnet volume.

　　Experiments show that under the same excitation condition in weak magnetic environment, the energy collector can output more than twice as much electric energy as the traditional cantilever structure in the same unit time, which can completely make the sensor without battery work normally and communicate with the mobile phone terminal.

　　Chu Zhaoqiang said: "In scientific research, it is often a small or even inconspicuous design method that plays a key role. But the source of this method must be based on long-term research and thinking. "

　　Future or used in underwater small bionic platform

　　"At present, this energy collection technology for magnetic field still has some limitations in application. Science always solves a problem and brings many new problems." Chu Zhaoqiang told the Science and Technology Daily reporter that in the future, he will mainly consider further optimizing the parameter design of magnetic-mechanical-electric energy harvesting devices clamped at both ends in terms of materials and geometry, further realizing the integration of increasing the adaptive magnetic field variation range and miniaturization, and providing key technologies for the development of self-powered magnetic field sensitive components, intelligent sensing of power grid transmission and transformation, and topological relationship identification of distribution power network.

　　Chu Zhaoqiang also said that the team will combine the advantages of Harbin Engineering University’s marine scientific research to deeply study the wireless energy supply technology based on ultrasound and magnetic field for small underwater bionic platforms such as underwater robotic fish and unmanned underwater vehicles, which can not only solve the problem of energy "taking" of small bionic platforms, but also solve the problem of energy "supply".

　　Chu Zhaoqiang’s team of "Marine Magnetic Sensors and Detection" in the Underwater Acoustic College of Harbin Engineering University and the Innovation and Development Base was established in 2017 and has been growing continuously. Aiming at the basic theory, key technologies and engineering applications of multi-sensor detection of underwater targets, the team has comprehensively carried out technical research on basic magnetic materials, magnetic sensor development, underwater information perception and processing.

　　Reporter Li Liyun correspondent Huo Ping

Source: Science and Technology Daily