The Laboratory of Nanoscience and Energy Technology (LNET) at the School of Engineering of the Ecole Polytechnique Fédérale de Lausanne in Switzerland recently developed an experimental nanopower generation device that can continuously generate a stable current using the evaporation process of seawater. This device uses silicon semiconductors as its core and achieves autonomous power generation by regulating the movement of ions and electrons and driving the evaporation of seawater with the help of light and heat. Researchers say this mechanism is expected to open up new paths for eco-friendly energy harvesting technology. Relevant results have been published in the journal Nature Communications.
In their paper, Giulia Tagliabue, the leader of the research team, and Tarique Anwar, a researcher, proposed a "unified physical and experimental framework" for evaporation-driven hydrovoltaic systems. The key lies in separating and accurately controlling the interface process. The interface process here refers to the interaction between different phase states such as solid, liquid, liquid gas, etc. The research team hopes to use this framework to convert the evaporation process into electrical energy output more efficiently with the participation of sunlight and heat energy.
This technology builds on LNET's previous research into the "hydrovoltaic effect." The so-called hydrovoltaic effect means that when liquid flows through the surface of charged nanodevices, it can induce the generation of electrical energy. The new device further uses the tiny gaps between the hexagonally arranged silicon nanopillars to promote liquid evaporation and guide the movement of ions in seawater in the process. The researchers pointed out that heat and light will always affect the performance of hydrovoltaic devices, and their breakthrough this time is to convert these originally unavoidable effects into performance advantages for the first time, using inexhaustible and relatively environmentally friendly seawater as the energy medium.
An important conceptual breakthrough in the research was that the team discovered that the enhanced power generation was not simply the result of evaporation itself. Because the device uses silicon semiconductor material, heat increases the negative charge on the semiconductor surface, while sunlight stimulates electronic activity within it. In other words, evaporation, thermal effects and light effects are not independent of each other, but form a synergistic effect in the device to jointly promote the improvement of power generation efficiency.
According to the research team, the gain brought about by this surface charge effect is quite significant. By introducing sunlight and heat, the energy output of the device can be increased by up to five times. Tagliabue said this natural effect has always existed, but they are the first researchers to actually exploit it.
From the structural design point of view, this evaporation power generation device adopts a three-layer architecture, corresponding to the three independent processes of evaporation, ion transport and charge collection. The top is the evaporation surface layer, the middle layer is responsible for ion conduction, and the bottom is the dielectric silicon nanopillar array. Such a layered design not only helps researchers gradually analyze and calibrate the process and results of each stage, but also further improves the overall power generation performance of the device and more clearly reveals how heat and light induce charge generation and promote ion migration.
In addition to power generation capabilities, this technology also offers clear advantages in terms of durability. The researchers pointed out that heat and light can cause the hydrovoltaic mechanism to degrade, and corrosion problems in high-salt environments can exacerbate this process. However, the surface of the silicon nanopillars in the device is covered with an oxide coating that remains stable under light and heat, thereby avoiding unnecessary chemical reactions and improving the reliability of the device in seawater environments.
The research team said that if subsequent iterations go well, this type of hydrovoltaic device is expected to provide continuous, автономную power support for various small, battery-free sensor networks in the future, as long as sunlight, heat and water are available to operate. Potential application scenarios include environmental monitoring systems, Internet of Things devices, and current and future wearable technologies. Researchers believe that if a mobile and nearly “free” way to obtain electricity can be put into practical use, the social value it will bring will be immeasurable.