New paradigms of water‐enabled electrical energy generation

Nanotechnology‐inspired small‐sized water‐enabled electricity generation (WEG) has sparked widespread research interest, especially when applied as an electricity source for off‐grid low‐power electronic equipment and systems. Currently, WEG encompasses a wide range of physical phenomena, generator structures, and power generation environments. However, a systematic framework to clearly describe the connections and differences between these technologies is unavailable. In this review, a comprehensive overview of generator technologies and the typical mechanisms for harvesting water energy is provided. Considering the different roles of water in WEG processes, the related technologies are presented as two different scenarios. Moreover, a detailed analysis of the electrical potential formation in each WEG process is presented, and their similarities and differences are elucidated. Furthermore, a comprehensive compilation of advanced generator architectures and system designs based on hydrological cycle processes is presented, along with their respective energy efficiencies. These nanotechnology‐inspired small‐sized WEG devices show considerable potential for applications in the Internet of Things ecosystem (i.e., microelectronic devices, integrated circuits, and smart clothing). Finally, the prospects and future challenges of WEG devices are also summarized.