Submerged Cones Boost Wave Energy Device Efficiency

Wave energy, a promising source of clean electricity, faces a challenge: many devices do not naturally synchronize with ocean waves, leading to reduced power capture. To address this, researchers from ESPOL and Stevens Institute of Technology have devised a passive tuning method. This approach involves attaching submerged cones to the sides of a floating platform, which alter the system's motion by trapping water and helping it respond more effectively to changing sea conditions, particularly long ocean swells.

This innovative strategy offers a simpler alternative to complex active control systems. Instead of adding intricate mechanisms, the researchers leverage the natural interaction between the platform's structure and the surrounding water. The studied system uses the rolling motion of a floating barge; upside-down cones hanging below the water line increase the platform's apparent weight and add water resistance, thereby modifying its movement and improving its response to long waves.

To validate their concept, a 1:40 scale model was tested in a wave tank. Experiments compared a base case without cones to four configurations with cones of varying sizes and positions. The primary goal was to assess the impact on the platform's stability, natural roll period, wave response, and overall energy capture. The results demonstrated that the cones significantly altered the system's behavior.

Crucially, the passive tuning with cones more than doubled the device's natural roll period, enabling it to better match the rhythm of long swells. The tests also confirmed that the cones did not compromise the platform's stability while increasing water resistance, a key balance for efficient energy capture. The best-performing configuration achieved a Capture Width Ratio of 52% in regular waves and maintained efficiencies close to 21.5% in irregular waves, indicating effectiveness in realistic, unpredictable sea states.