Natural electricity production from soil-air water exchange: A wide and untapped energy

The exchange of water between soil and air is a ubiquitous natural phenomenon. Evaporation and condensation are the two main processes that extract or release energy from the environment. However, due to the low energy density and complex interface of soil, the associated energy has long been overlooked and under-exploited. Here we demonstrate that the energy can be converted into electricity in situ through the hydrovoltaic effect within the soil itself. The soil-based hydrovoltaic electricity generators exhibit excellent reproducibility and stability, demonstrating the potential for scalable integration. A series voltage of over 13.4 V was achieved, placing it in the top five of integrated devices reported to date. By designing an integrated module suitable for amplifying natural electricity from both soil evaporation and soil condensation process, a parallel current of up to 18.62 μA (0.06 m²) was obtained. The availability of soil demonstrates the great potential of the soil-based electricity generators. This finding demonstrates a green and sustainable technology for electricity generation, and points to possible biogeochemical processes due to the hydrovoltaic effect of soil.