In the past few years, IoT devices have grown at an incredible rate, bringing great convenience to human life. For IoT devices deployed in specific locations, although the device itself has a power-saving design, it is difficult to replace the battery in the deployment location. Therefore, the development of battery-free IoT devices that can obtain power from external energy sources has become a research and development direction actively invested in the world.
At present, the external energy used by battery-free IoT devices can be roughly divided into solar energy, temperature difference, vibration, and wireless energy transmission. With a dedicated energy management chip, it can provide appropriate energy for IoT devices. Among the aforementioned various environmental energy sources, solar power generation is currently the most mature. In addition to the advantages of easy acquisition of light energy, it also has the characteristics of higher power density and greater energy availability. Although the energy available for temperature difference power generation is relatively low, it is suitable for the sensing of human physiological signals. The energy source ultimately depends on the application mode and scenario.
Po-hung Chen, a professor at the Institute of Electronics of National Chiao Tung University, said that a sensor device that uses a battery-free design must not only adopt a low-power design, but also a sensor device that transmits less data and has a short time. Only in this way it can be charged by solar energy and temperature difference most of the time, and detect and store data in a low power consumption state, and use high power to transmit data in a very short time when the criteria are met.
Store energy at ordinary times and send data at important moments
Battery-free IoT devices have a wide range of applications. Take logistics management as an example. If the warehouse’s own lighting equipment provides enough light sources, and the label of the item adopts a corresponding design, it usually records the storage status and content information of the product by absorbing energy. It also stores excess energy. When the energy is sufficient, complete product information can be sent to the server, which helps to greatly improve the efficiency of logistics management and delivery speed.
In addition, in order to grasp the health status of kidney dialysis patients, there is also a research and development team that integrates sensing components with flexible circuit boards, which can be attached to the patient''s arm. In this way, only a wristband with wireless charging function can be used to collect the patient''s health status, which will greatly help the follow-up precision treatment and bring more diverse imagination to smart medical care.
Po-hung Chen pointed out that in the past, due to technical limitations, to ensure that the patient’s health detection device can operate 24 hours a day, either the built-in battery will cause the product to be too large, or the device must be recharged regularly, even if there is now a small mobile power supply to be used, but it still makes the patient feel very inconvenient. Now that the sensor components are integrated with the flexible circuit board, the patient can hardly feel the existance of the detection device. Even with the wireless charging function of the bracelet, it will not affect daily life, and can smoothly collect more than 24 hours of physiological information. It is of great help to improve the life of patients with kidney dialysis.
In addition to battery-free design, energy harvesting technology can also be used with rechargeable batteries to achieve a hybrid power supply architecture. The Internet of Things devices can usually operate through external energy and charge the battery. When the external energy is insufficient, it can be powered by the internal battery, which can also effectively extend the battery life. Although the aforementioned cases are still in the technical verification stage, if commercial applications can be introduced in the future, the power supply problem of IoT devices will be solved, and the scope of IoT applications is expected to be expanded to create a better intelligent life for mankind.