Among the inter-connected devices, even if the mobile phone needs to be charged every day, it will not cause much trouble. However, even if the batteries of other nearly 100 billion devices only need to be replaced once a month or a year, because they may be located in remote places (such as the environmental detector is placed in the farming, forestry, fishery and pasture area), the battery replacement is time-consuming and difficult, causing a huge labor and cost burden. In view of this, in certain applications where the power demand is not too large, battery-free systems are expected.
Solar energy and temperature difference power generation have the potential for application
How to implement a battery-free system? For chip design, solar energy, temperature difference power generation, vibration power generation, radio frequency (RF) energy transmission and other energy harvesting/energy transmission technologies are all feasible methods. Regarding these technologies, many related papers have been published at international conferences in recent years.
Po-Hung Chen, a professor at the Institute of Electronics of National Chiao Tung University, pointed out, “Among these technologies, solar power and temperature difference power generation are favored because of the relatively high power density and the large amount of energy that can be provided per unit area, so they have more potential for application.” Among various battery-free system technologies, temperature difference power generation is more suitable for the sensing of human physiological signals. However, the current temperature difference power generation energy is still lower than that of solar energy, and solar energy is relatively easy to obtain, so the design of battery-free system is still mainly based on solar power generation.
In recent years, Po-Hung Chen’s research team has been committed to the development of power integrated circuits, energy harvesting circuits, wireless power transmission circuits, low-power power integrated circuits, etc., to develop innovative circuit technologies and system architectures that can integrate technologies into IoT devices, wearable devices, biomedical electronic devices, and improve device energy efficiency and battery life.
Low-power sensing device is suitable for battery-free design
The application of battery-free system is mainly to focus on the sensing device with a small number of transmission data and short time. For example, a device may only need 1 milli-second in an hour to transmit data with a large amount of power, and at other times it only performs low-power detection and data storage, so a battery-free system can use most of the time to store energy, and prepare power supply for the milli-second of data transmission. Currently, there are no related products on the market, but it is generally believed that the possibility of this application is extremely high.
Po-Hung Chen pointed out, "More and more companies are developing event-driven systems. The overall average power consumption is not high. They can integrate technologies such as solar power and temperature difference power generation, etc. to create a battery-free system." In terms of application, logistics management, positioning for people and items, merchandise management, etc., these are all scenarios that a battery-free system can play.
The specific application scale is not large, and the market has not yet formed
As a whole, most IoT device products on the market still adopt higher power designs. Few products can meet the conditions of sleep for 99% of the time and start-up of 1% of the time. Therefore, battery-free systems are still useless. “The techniques feasible, but it still needs the cooperation of other links in the industry chain to promote the development of battery-free system applications.” Po-Hung Chen said.
Another reason why battery-free systems cannot be quickly commercialized is that power chips for specific applications need to be specially designed. However, the scale of demand in each niche market is not large, which is not in line with the cost-effectiveness of development. Most companies even understand the benefits of the battery-free system and the needs of the future, but they are still not moving forward.
Po-Hung Chen ''''''''s team has many cooperation projects with the industry, mostly related to smart power management. As for the design of battery-free systems, it belongs to the advanced research of the laboratory. It is still being invested and its research results have achieved a leading position in the world. It is expected that battery-free systems can be commercialized soon, and so that can solve the big trouble of replacing the batteries of hundreds of billions of IoT devices once and for all.