Abstract

Utilizing the kinetic energy of a flowing river for irrigation could be tracked back to Hellenistic and Roman periods. In modern days, hydroelectric plants are built for harvesting the kinetic energy of the flowing river. However, a large investment is required in the hydroelectric plants for maximizing the power output. Here we present a low-cost and scalable TENG (triboelectric nanogenerators) based energy harvesting water wheel (ww-TENG). The water wheel works in a sliding freestanding TENG mode which generates power from the charges flow induced by contact electrification and electrostatic induction. A conformal fluorine coated carbon paper (f-CP) was employed to form the alternate electrodes. The deposited fluorine layer provides the benefits of high affinity to attract electrons as well as hydrophobicity for water repelling. The carbon paper offers a high electrical conductivity and rough structure to form a superhydrophobic property. These features enables a large charge induction and fast water/TENG separation for maximizing the power output of the energy harvesting water wheel. A lab-scale water wheel (diameter 10 cm and width 2.5 cm) is fabricated and a maximum 5.3 μW output power was measured under 50 MΩ resistance at a linear flow velocity of 2.6 m/s. The ww-TENG was employed for charging a 10 μF capacitor to 16 V and lighting up a commercial LED light bulb. As a comparison, an electromagnetic generator (EMG) could only charge the capacitor to 2.7 V with the same period of time. The EMG obtains a high power output at low load resistance case (< 100 kΩ) while the ww-TENG generates high power when the load resistance is large (> 10 MΩ). The present ww-TENG shows great potential for harvesting the kinetic energy from flowing river and targets for the applications with large load resistance like electrostatic systems.