Performance Comparison of Laser and Ultrasonic Sensors for Water-Level Monitoring in Wind Turbine Towers: System Development and Experimental Validation

Water accumulation inside wind turbine towers threatens structural integrity and operational safety. This study developed an IoT-based water depth monitoring and automatic drainage system and evaluated the performance of laser (VL53L0X) and ultrasonic (HC-SR04) sensors for tower sump water depth measurement. Laboratory experiments investigated the effects of sensor-to-wall distance (10–150 mm) and water depth (10–350 mm) on measurement accuracy. The ultrasonic sensor is susceptible to side-wall interference within 100 mm due to its broad beam angle, while the laser sensor exhibits significant underestimation in shallow water below 100 mm due to optical penetration. In dynamic drainage tests, the ultrasonic sensor achieved complete water removal (<1 mm residual), whereas the standalone laser sensor left 55 mm of residual water. This limitation was mitigated by an opaque floating reflector, which enabled the laser sensor to achieve complete drainage. The developed system offers a cost-effective solution for unmanned tower sump monitoring, contributing to enhanced safety of wind turbine structures.