From Plant Transpiration to Hydrovoltaics: Distributed Energy Harvesting Driven by Water Evaporation

Abstract

Water evaporation is one of the most powerful and widely distributed energy fluxes on Earth, yet it remains largely untapped for direct electricity generation. Plants harness evaporation through transpiration, where capillary flow and sustained negative pressure drive long-range water transport without moving parts. Inspired by this natural hydraulic engine, transpiration-inspired hydrovoltaics (TIH) have emerged as solid-state material platforms that convert evaporationdriven water transport into electrical output via interfacial electrokinetic processes. In this review, we introduce a unified physical framework for TIH by explicitly linking the physics of plant transpiration to evaporation-driven electricity harvesting in engineered porous media. We summarize the governing principles of water ascent in trees, including capillarity, water-potential gradients and cohesion-tension stability, and map these concepts onto synthetic TIH architectures built from hydrophilic micro-and nanofluidic networks. We critically assess proposed electricitygeneration mechanisms for TIH, including classical streaming potentials, pseudo-streaming in conductive porous networks and ionovoltaic coupling in semiconducting channels. We synthesize how geometry, pore microarchitecture, surface chemistry, electrical conductivity and environmental conditions such as humidity, temperature and airflow collectively regulate device performance. By benchmarking TIH against decades of quantitative insight from plant hydraulics, we distill key trade-offs, unresolved mechanistic questions, and actionable opportunities to achieve robust, scalable evaporation-driven power generation and self-powered sensing, positioning TIH as a compelling platform for distributed energy harvesting at the water-energy nexus.