In a groundbreaking development for sustainable energy, researchers from the Laboratory of Nanoscience for Energy Technology (LNET) at EPFL’s School of Engineering have unveiled a revolutionary hydrovoltaic (HV) system. This innovative platform, reported in 2024, leverages the hydrovoltaic effect, where electricity is generated as fluid evaporates over a charged nanodevice surface. The system, developed by a team led by Giulia Tagliabue, promises power outputs that match or exceed existing technologies, with a unique advantage: it harnesses heat and light to control ion movement and electron flow, rather than merely boosting evaporation.
The LNET team’s platform features a hexagonal network of silicon nanopillars, creating channels for fluid evaporation. “Heat and light imbalances will always affect a hydrovoltaic device, but we have discovered how these can be leveraged to our advantage,” explains LNET researcher Tarique Anwar. Their research, published in Nature Communications, highlights a decoupled design with three layers dedicated to evaporation, ion transport, and electrical charge collection, allowing precise control over each step.
Harnessing a Natural Effect
Traditionally, heat and light are known to accelerate water evaporation. However, the EPFL researchers discovered that the increased energy production from their nanodevice was not solely due to evaporation. The silicon semiconductor nanodevice utilizes sunlight photons to excite electrons, while heat enhances negative surface charges. Simultaneously, heat-driven evaporation in a saltwater layer above the device causes ion shifts, creating charge separations that form an electric field. This field propels excited electrons through a circuit, generating electricity.
“Our work shows that due to this surface charge effect, the addition of solar light and heat can enhance energy production by a factor of 5. This natural effect has always existed, but we are the first to harness it,” Tagliabue says.
Continuous, Autonomous Power
The new system not only boasts impressive voltage and power density—1 V and 0.25 W/m2, respectively—but also offers continuous, autonomous electricity generation. “In HV devices, performance enhancement via heat and light inputs causes material degradation over time, especially in saltwater conditions. In contrast, our device’s nanopillars are coated with an oxide layer to ensure stable performance under heat and light, and to protect against unwanted chemical reactions,” Tagliabue explains.
The separation of the device into three layers enabled the team to develop a model to optimize power output by adjusting the nanopillar structure and salt concentration. They are now creating tools to probe these phenomena in real time, experimenting with heat and light input using a solar simulator.
The Future of Hydrovoltaic Technology
This innovation is expected to accelerate the development of hydrovoltaic devices, which hold significant potential for powering battery-free small sensor networks in environments rich in water, heat, and sunlight. Such applications include self-powered environmental monitoring systems, wearable technology, and internet-of-things devices.
As the world seeks sustainable energy solutions, the EPFL team’s breakthrough represents a promising step towards harnessing natural processes for continuous power generation. The implications for energy independence and environmental sustainability are profound, and further research will likely expand the capabilities and applications of this technology.
