Wind energy harvesting based on fluttering double-flag type triboelectric nanogenerators

The efficient harvesting of ambient wind energy is regarded as a potential solution to the problem of power supply for wireless sensor network nodes. This paper proposes a fluttering double-flag type triboelectric nano-generator (FD-TENG) for ambient wind energy harvesting. Two thin fluorinated ethylene propylene films with evaporated Ag electrodes on the surface were fixed back-to-back with a certain gap length. Under the action of ambient wind, the flutter contact between the two films formed a fully flexible TENG with a contact separation mode. The electrical output characteristics of the FD-TENG were measured at different wind speeds. The effects of different design parameters, including the material used, sizes of the flags, and gap length between two flags, on the peak-to-peak power and root mean square (RMS) power of the FD-TENG were analyzed. For the FD-TENG with flag size of 110mm x 60mm, the power density could reach 600 mW/m(2) (peak-to-peak power density) and 10 mW/m(2) (RMS power density). Compared with the power density of some typical flag-type TENGs in the literature, the proposed FD-TENG has a superior power generation performance. There is an optimal gap length, at which the highest power density value is obtained. The charging characteristics of different numbers of FD-TENGs connected in parallel to the load capacitance under specific wind speeds were tested, and its reliability was verified through more than 16,000 cycles of contact tests. An array-type FD-TENG, composed of several identical FD-TENGs, is designed to drive a temperature/humidity sensor in an actual environment. It is shown that the FD-TENG has the potential to solve the power supply problem in wireless sensor network nodes.