Research progress of power generation device driven by water evaporation

The increasing demand for energy in modern human society requires new energy production technologies. Due to the large amount of untapped energy in the environment, collecting electrical energy from clean and renewable resources is considered a promising solution to the growing energy crisis. Various environmental energy conversion technologies, such as solar cells, thermoelectric batteries, piezoelectric nanogenerators, friction nanogenerators, electret nanogenerators, and even moisture-driven generators have been developed to generate electricity. However, these devices require external stimuli, such as sunlight, thermal gradients, or pressure or humidity gradients, and are always accompanied by loss of electrical, thermal, and mechanical energy during the conversion process. Ideally, efficient energy conversion methods are driven by natural processes, such as evaporation without mechanical movement or any by-product pollutants. Since the 21st century, based on the mechanisms of electrostatic induction, flow potential phonon coupling, Coulomb drag, dynamic electric double layer, chemical penetration, etc., people have discovered a series of new power generation methods and expanded the available forms of water energy. However, most of these new energy conversion effects can only provide millivolt-level voltage output, which limits their practical application. Although the output voltage of electrostatic induction, chemical penetration, dynamic double layer and other effects has achieved a breakthrough of volt level or even 100 volt level, their output is pulsed or intermittent, and it cannot supply power continuously and stably. In practical applications, continuous energy supply is important for energy-consuming equipment. Until 2017, the team led by Professor Jun Zhou and Professor Wanlin Guo had made significant progress in the field of water-vapor-driven generators. They used cheap carbon black materials to evaporate water and produced a continuous continuity of about 1 V at room temperature, and more than 100 h of voltage. They called it "water evaporation power generation effect". Subsequently, a large number of power generation devices based on water evaporation emerged. The material was no longer limited to the carbon black that was just used. Oxides and composite materials were also widely used by people. The power generation increased from less than 0.1 mu W to more than a dozen mu W. These power generation devices based on water evaporation convert the heat energy absorbed from the environment into electrical energy during the evaporation process. They have the characteristics of simple structure, low cost, easy amplification, and large voltage output. They are a green and non-polluting new technology, and the process is driven spontaneously. It does not require external energy input, which highlights the possibility of using water in the environment as an energy source, and has the potential to be used as an energy harvesting device and self-powered sensor. This paper summarizes the research status of water evaporative power generation devices in recent years, gives a systematic overview of its materials, device configuration, power generation performance, etc., highlights the current ambiguity of the generator system, and makes future development directions prediction.