A novel humidity resisting and wind direction adapting flag-type triboelectric nanogenerator for wind energy harvesting and speed sensing

Wind energy harvesting from ambient environment by TENG is highly desirable for powering the wireless sensing system. However, humid environment and variable wind direction deteriorate the output performance of the most demonstrated TENG-based wind energy harvesters. In this work, a humidity resisting and wind direction adapting flag-type TENG is to be proposed and investigated. The flag-type TENG consists of two carbon coated polyethylene terephthalate membranes and one strip of poly tetra fluoroethylene membrane with their edges sealed up. Thus, the triboelectric layers are isolated from the air and the electrical performance is independent of the relative humidity. Parametric studies are conducted to evaluate the influence of geometrical parameters of the flag-type TENG on the flutter behavior and the resulting energy output. It is interesting to find that a pair of flag type TENGs with a certain gap distance can contact with each other due to the wind speed variation and pressure difference between the internal and external flow areas. The power density is increased by 40 times compared with the only one flag-type TENG. In addition, the flag-type TENG can harvest wind energy from arbitrary directions without equipping other extra mechanisms. It can also serve as a self-powered wind speed and direction sensor. Therefore, the present flag-type TENG has a great potential to apply for ambient wind energy harvesting, self-powered wind speed and direction sensing in harsh natural conditions.