A Hybridized Triboelectric–Electromagnetic Water Wave Energy Harvester Based on a Magnetic Sphere

Blue energy harvested from ocean waves is an important and promising renewable energy source for sustainable development of our society. Triboelectric nanogenerators (TENGs) and electromagnetic energy harvesters (EMGs) both are considered promising approaches for harvesting blue energy. In this work, a hybridized triboelectric-electromagnetic water wave energy harvester (WWEH) based on a magnetic sphere is presented. A freely rolling magnetic sphere senses the water motion to drive the friction object sliding on a solid surface for TENG back and forth. At the same time, two coils transform the motion of the magnetic sphere into electricity according to the electromagnetic induction effect. For harvesting the blue energy from any direction, the electrodes of the TENG are specified as the Tai Chi shape, the effective of which is analyzed and demonstrated. Based on a series of experimental comparisons, the two friction layers and the two coils are specified to be connected in parallel and in series, respectively. A paper-based supercapacitor of ∼1 mF is fabricated to store the generated energy. The WWEH is placed on a buoy to test in Lake Lanier. During 162 s, the supercapacitor can be charged to 1.84 V, the electric energy storage in it is about 1.64 mJ. This work demonstrates that the WWEH can be successfully used for driving distributed, self-powered sensors for environmental monitoring.