China’s “dual carbon” strategy advocates for a green, environmentally friendly, and low-carbon lifestyle, which relies on the continuous development and innovation of green energy technologies. As China vigorously develops renewable energy, the recovery and reuse of micro-energy such as magnetic energy in the real environment has attracted the attention of many researchers.
The School of Underwater Acoustic Engineering at Harbin Engineering University, along with the “Marine Magnetic Sensors and Detection” innovation development team, led by young teacher and associate professor Chu Zhaoqiang, has designed a new structure for a weak magnetic energy harvester. This device allows IoT sensors to avoid the tedious manual operations of battery replacement and maintenance, achieving “self-powered” operation under weak magnetic conditions, with an output power approximately 120% higher than that of traditional magnetic energy harvesting structures. Recently, the academic paper titled “Significantly Enhanced Weak Magnetic Energy Recovery Performance in Two-Ends-Clamped Magnetic-Force-Electric Harvesting Devices” was published online in the internationally renowned journal Advanced Energy Materials.
Recovery and Reuse of Micro-Energy in the Environment
“The Internet of Everything” is an important engine for creating an intelligent world and has spurred the rapid development of IoT technology. Currently, one of the major challenges in developing IoT is finding self-sustaining energy technologies for sensor communication nodes to support the construction of large-scale, distributed sensor networks.
In response to this technical challenge, various fields in China are actively planning to find solutions. The 2021 National Key R&D Program “Intelligent Sensors” focused on the self-sustaining energy acquisition technology from the human body for multi-parameter biological sensors in wireless scenarios; the 2022 National Key R&D Program “Intelligent Sensors” proposed project guidelines for self-sustaining magnetic field-sensitive components and sensors for distributed sensors in power network status perception; the 2022 National Natural Science Foundation also included research on micro-piezoelectric vibration harvesting technology for aerospace applications in its guidelines.
It can be said that developing distributed energy harvesting technologies to recover and reuse micro-energy in the environment is of great importance, responding to the national energy-saving and emission reduction strategy and aiding in achieving carbon peak.
In the recovery and utilization of environmental micro-energy, among the many collectable energy sources such as vibration energy, radiation energy, and near-field electromagnetic energy, the stray magnetic energy generated by power cables, industrial machinery, and household appliances has attracted researchers’ attention due to its fixed frequency and wide distribution, leading to higher efficiency than low-frequency energy sources like wind energy. Especially in the context of building smart grids, the online monitoring and fault diagnosis of transmission line status parameters urgently require energy harvesting from overhead cables to construct a sustainable self-sustaining sensor network.
Just like the beautiful new world depicted in the novel “The Three-Body Problem”, where cups can self-heat without a power source or battery, and flying cars can fly continuously without batteries, all powered by wireless power fields generated by microwaves or other forms of electromagnetic oscillation. This technology is similar to what is currently used for wireless charging of mobile phones. Initially, people’s attention was also drawn to traditional inductive power devices. However, this technology has prominent issues such as large size, inconvenient installation, and difficulty withstanding short bursts of high current.
Thus, researchers began to study a harvesting device that converts magnetic energy into mechanical energy and then into electrical energy (MME), which is expected to become a new option for low-frequency magnetic field energy harvesting.
Chu Zhaoqiang introduced that this new type of harvesting device utilizes the magnetic torque effect and magnetic hysteresis expansion effect, and then converts mechanical energy to electrical energy using the piezoelectric effect. Its advantages include not requiring the closed magnetic circuit needed for inductive power devices, as well as achieving higher efficiency in energy conversion and better tolerance for strong current pulses.
New Methods for Low-Field Energy Harvesting
Chu Zhaoqiang has been involved in energy harvesting technology from vibrations and magnetic fields since 2016. From 2016 to 2021, he focused on research related to materials and devices based on traditional cantilever beam resonant structures. This is a type of energy harvester structure with one end fixed and the other end free, with a mass block (magnet) added at the free end. This structure provides driving torque from the magnetic mass block at the free end, contributing over 90% of the equivalent mass. In this case, to maintain the resonant frequency of the resonator at 50 Hertz (Hz), it is difficult to enhance the magnetic-force coupling performance simply by increasing the mass of the magnet at the free end. This is why most current research on cantilever beam magnetic-mechanical-electrical devices is limited to energy harvesting from strong magnetic fields, specifically those greater than 5 Oe. The World Health Organization indicates that the safety threshold for public exposure to 50/60 Hz alternating magnetic fields is 1 Oe, and the stray magnetic fields in the environment are generally below this reference value. Therefore, it is also necessary to explore new principles and methods suitable for low-field energy harvesting.
Based on the idea of “how to reduce the equivalent mass of the magnetic mass block at the free end in magnetic-mechanical-electrical harvesting devices”, Chu Zhaoqiang boldly innovated and proposed a design concept of a two-ends-clamped beam. This design fixes both ends of the magnetic-mechanical-electrical harvesting device, adopting a second-order vibration mode, which reduces the kinetic energy of the central magnetic mass block, thereby decreasing its contribution to the equivalent mass of the resonant system, significantly improving the system’s output performance under 50 Hz weak field conditions while increasing the volume of the magnet.
Experiments show that under the same excitation conditions in a weak magnetic environment, this energy harvester can output more than twice the electrical energy of traditional cantilever beam structures in the same unit of time, fully enabling sensors without installed batteries to operate normally and communicate with mobile terminal devices.
Chu Zhaoqiang stated: “In scientific research, a small, even inconspicuous design method often plays a key role. However, the source of this method must be based on long-term research and reflection.”
Future Applications in Underwater Small Biomimetic Platforms
“Currently, this technology for energy harvesting from magnetic fields still has certain limitations in application; science always solves one problem but brings many new ones,” Chu Zhaoqiang told the Science and Technology Daily reporter. In the future, he will mainly consider further optimizing the material and geometric parameter design of the two-ends-clamped magnetic-mechanical-electrical harvesting devices to increase the adaptable magnetic field range and miniaturization for developing self-sustaining magnetic field-sensitive components, as well as smart sensing for power grid transmission and distribution topology relationship identification.
Chu Zhaoqiang also mentioned that the team will leverage the unique advantages of Harbin Engineering University in ship and marine research to conduct in-depth studies on wireless power technologies based on ultrasound and magnetic fields for small underwater biomimetic platforms such as underwater robotic fish and unmanned underwater vehicles. This will not only address the energy “harvesting” problem for small biomimetic platforms but also solve the energy “supply” problem.
Further Reading:
“Thermoelectric Energy Harvesting and Other Zero-Emission Thermal Power Generation – 2022 Edition”
“Triboelectric Energy Harvesting and Sensing (TENG) – 2020 Edition”
“Thermoelectric Cooling, Heating, and Energy Harvesting – 2021 Edition”
“Energy Harvesting Technologies from Micro-Watts to Giga-Watts and Market Opportunities – 2020 Edition”
“Battery-Free Electronics: Market Impact on IoT, 6G, Medical, and Wearable Technologies – 2021 Edition”
