Energy Harvesting 環境発電
The Internet of Things (IoT), which aims to create a more affluent society by using information obtained from wireless sensor terminals mounted on various objects, is attracting attention. However, the number of wireless sensor terminals is said to be as many as 10 trillion, making maintenance impossible and making battery replacement impossible. Environmental power generation is expected to be the power source for next-generation wireless sensor terminals. Environmental power generation is an effort to recover vibration, light, heat, and RF energy that has been discarded in the past, and high-power vibration power generation elements, solar cells, thermoelectric elements, and rectenna have been developed. In this research, we are fabricating and evaluating zero-energy devices that use the energy recovered by these power generation devices to drive electronics.
Event driven circuit イベントドリブン回路
Vibration is a promising energy source because it is abundant in the environment and can generate electricity even in dark places. We fabricated an electret vibration power generation device that generates electricity in the vibration range (acceleration < 1 G, frequency 200 Hz), where conventional piezoelectric and electromagnetic induction devices are unable to generate electricity, to drive a wireless sensor terminal. The energy consumption of the wireless sensor terminal was 1.2 mJ per operation, and wireless communication was successfully achieved once every 60 seconds when the vibration power generation device was used as the power source.
Battery-less sensor 電池レスセンサ
The output power of power-generating devices is increasing year by year, with vibration power-generating devices showing an output power of 100 µW/cm2. On the other hand, power consumption of LSIs is decreasing, and a timer IC can be driven with a power consumption of 60 nW. Based on this trend, by the 2020s, the output power of power generation devices will exceed the power consumption of LSIs, and it will be possible to drive LSIs with power generation devices. In this study, we confirmed the validity and appropriateness of the above idea by driving ICs with power-generating elements. Using the fact that the oscillation frequency of the ring oscillator depends on the supply voltage, we proposed a battery-less sensor that uses a power-generating element as the sensor and power source. This device can perform analog-to-digital conversion with pulse density modulation according to the output of the generator element.
S. Yamada, et al., IEEE Electron Device Lett., 2017
