Self-powered siphon rain gauge based on triboelectric nanogenerators

Rainfall measurement is of great significance to agriculture, weather forecasting and water resource management, while rain energy harvesting is a desirable solution to energy demand of wireless sensor networks of rainfall information. In this work, a novel self-powered siphon rain gauge (SR) integrating with a siphon unit, a sensing unit and an energy harvesting unit is proposed, which can simultaneously measure rainfall information and capture rain energy. In the siphon unit, a siphon structure is used to periodically automatically trigger and stop siphon events. In the sensing unit, a liquid-solid multi-tube triboelectric nanogenerator (TENG) is proposed for the first time to detect rainfall information by a multi-tube synergistic sensing strategy. In the energy harvesting unit, a rotary TENG excited by the siphon emptying event is utilized to generate electricity by a rainwater potential energy collection-based generation strategy. After optimization design, the water level resolution of the multi-tube TENG is around 2.5 times higher than that of traditional single-tube TENG, resulting in a rainfall resolution of 20.45 & mu;m of SR. Besides, the rotary TENG successfully converts random, disordered, high-entropy raindrops energy into regular, ordered, low-entropy fluid mechanical energy. It can finally help the SR achieve a power density of 97.2 & mu;W/m2, which is nearly 2.5 times higher than that of liquid-solid contact TENG using the traditional instantaneous impact-based generation strategy. The proposed selfpowered SR not only obtains an excellent real-time rainfall sensing capability, but also has remarkable rain energy harvesting ability. Therefore, this SR has great potential for extensive applications in the hydrology and meteorology fields.