Liquid Solid Electricity Generators Based On Bulk Effect

Harvesting water kinetic energy meets the urgent demand in clean and sustainable energy for modern society and also is an active response for carbon-neutrality.The droplet-based electricity generator(DEG)has been demonstrated for effectively transform water kinetic energy into electricity with instantaneous power density up to50.1 W/m~2,breaking the output performance bottleneck of liquid-solid electricity generators.In spite of the breakthrough in the output performance,the working mechanism of DEG still needs a deep exploration.In addition,it is challenging to achieve an ultra-high output performance and to dramatically simplify pre-charging process simultaneously in this condition of the reported pre-charging methods,continuous droplet impingement or electrowetting.Hypothesize that the target of high output performance with a simplified pre-charging process is realized,the universality of DEG is still unclear,which greatly influences its application.Here,on the basis of working principle of DEG,we reveal the mechanism of charge transfer and coupling between the liquid and solid materials.And the corresponding equivalent circuit model is constructed for reflecting such coupling effect between physical variables and surface charge density of materials.After the mechanism exploration,we propose a strategy that simultaneously achieve high output performance and a simplified pre-charging process by designing dielectric materials,architecture,droplet hydrodynamics and external circuit matching to engender proper and fast charge transfer.The performance of DEG achieves a new record through such systematical design.Moreover,as for the universality of DEG,we develop a single electrode droplet-based electricity generator that breaks through the limit of material selection and operating location,unfolding a new dimension for water kinetic energy harvesting on the solid-liquid interface.The main contents and results are presented as follows:1.From the perspective of working principle,we reveal the charge transfer in bulk effect,analyze the impact of physical variables in the output performance of DEG as well as construct the equivalent circuit model to reflect that the output of the generator is controlled by the surface charge density of dielectric material.The impact in output performance which is originated from the variables in DEG is coupling.We extract the coupling result V_G to the circuit model for revealing the essence of the whole electricity generation.The model indicates that the output performance of generator is directly related with the surface charges that are determined by the dielectric material,the dielectric layer thickness,and the ion concentration in droplets.2.From the perspective of electricity output,we propose a systematical strategy for dramatically boosting the output performance of DEG and simplifying the pre-charging process.Due to the coupling between physical variables and output performance of DEG,designing DEG with high output performance needs to systematically consider dielectric materials,architecture,droplet hydrodynamics and external circuit matching.Moreover,an appropriate dielectric layer thickness can endow DEG not only excellent output performance but a simplified pre-charging process.With the proposed strategy,the generator reaches almost 80%of the stable output after around 30-time droplet impingements within 10 seconds.And its instantaneous power density and average power density per pulse are achieved up to 2030 W/m~2 and 357 W/m~2 in liquid-solid electricity generators to date.3.From the perspective of liquid universality in DEG,we develop a volume effect electricity generator(VEEG)based on water column,verifying that bulk effect also can be applied in water column kinetic energy harvesting,rather than limited in droplet.A constrained water column in VEEG is designed to replace the discrete droplet in DEG.The novel internal electrode design in VEEG enables a directional charge flow in the bulk water.Therefore,the output performance is dramatically boosted in comparison with the interfacial effect electricity generator.10 cm length water column can output the voltage and current up to 904 V and 509?A,respectively.And the instantaneous output power can be 118.1 m W under the external load resistance?2 M?.VEEG can generate the output voltage without the restrictions of water sources.Moreover,VEEG is also applicable for arrayed application.Array-based VEEGs could enhance the power output comparing to single VEEG and provide new possibilities of electricity generation with water columns.4.From the perspective of solid materials universality in DEG,we report a single electrode droplet-based electricity generator(SE-DEG)that allows converting water droplet kinetic energy into electricity power on any surfaces.The fabrication of SE-DEG is finished merely by locating an electrode on the top surface of a solid material.As an impinging water droplet spreads on the solid surfaces and contacts the electrode,SE-DEGs can effectively convert water kinetic energy into electricity power.Different polarity of solid surface charge corresponds to different voltage,current and the transferred charge in SE-DEG.Moreover,the output performance of SE-DEG is demonstrated to be enhanced with the optimized frequency,falling height and size of droplet.SE-DEG successfully harvests water kinetic energy based on different surfaces in different places,whatever flat or irregular,artificial or natural,indoors or outdoors,representing a new dimension in ability to harvest abundant hydrodynamic energy everywhere.