Active fog harvesting: Performance enhancement via mechanical vibration

• The effects of mechanical vibrations on fog harvesting were experimentally investigated. • Tests used flow velocities of 1 and 4 m/s, vibrations at 5, 50, and 150 Hz, and input power 1–5 W. • Periodic vibrations increased water collection at both flow velocities. • Periodic vibrations enhanced collection using 90 % less energy than continuous vibration. • Mechanical vibration can improve or reduce water collection. Fog harvesting using metal wire meshes has gained wide application due to their low cost, availability, and mechanical durability. Nevertheless, their relatively low collection efficiency has motivated ongoing research aimed at enhancing performance. The present study explores the use of mechanical vibration to promote droplet removal and thereby increase overall water collection efficiency. The effects of mechanical vibration were experimentally examined under two operational scenarios: continuous and periodic. In the first scenario, continuous vibrations at various frequencies and input powers were applied to fog-collecting mesh under two distinct flow velocities. The results showed that efficiency improvements occurred only under specific conditions, while in other cases, performance declined due to excessive droplet re-entrainment, limited formation of new droplets, and clogging of the mesh surface. To address these limitations, a second scenario was implemented using a periodic vibration strategy, consisting of activation intervals separated by pauses. The second scenario, applied under the most favorable conditions identified in the continuous vibration tests, yielded substantial improvements (enhancing water collection efficiency by up to 19.7 % at low flow velocity and 21 % at high velocity). These findings demonstrate that carefully tuned vibration parameters, including frequency, input power, and duty cycle, can significantly enhance fog harvesting performance by improving drainage, reducing water retention, mitigating re-entrainment, and increasing energy efficiency.