Session: 09-05-04 Wave Energy: Power Take Off Systems

Submission Number: 180216

Analytical Insights Into Power Take-Off Integration in ADWEC: A Passively Tuned Roll-Harvesting Wave Energy Converter 

Low-energy wave environments are often overlooked for wave energy conversion because efficient operation requires systems capable of tuning their natural frequencies to match long-period, low-amplitude waves. The Adaptive Wave Energy Converter (ADWEC) was developed to address this challenge by harvesting energy from roll motion. The system consists of a floating barge equipped with suspended cone-shaped structures that passively modify the effective roll inertia through entrained-flow motion, allowing the natural roll frequency of the device to adapt to local sea states without active control. Mechanical power results previously reported from a proof-of-concept prototype were promising; however, the analysis assumed rigid-body motion of the entire system.

This work provides analytical insights into the integration of a simplified power take-off (PTO) model into ADWEC, allowing relative motion between the cones and the barge. A linearized analytical formulation is developed using an equivalent single-degree-of-freedom representation that captures the dominant hydrodynamics, including restoring, inertial, and damping effects. The model is calibrated with experimental data obtained from a 1:40-scale prototype, tested at the Davidson Laboratory to reproduce the hydrodynamic roll response in the absence of PTO. A predictive PTO representation is then introduced as a linear spring-damper element acting on the relative motion to estimate energy-extraction trends.

The results show that properly tuned PTO damping can broaden the operating bandwidth and enhance energy-conversion efficiency under moderate sea conditions. The analytical framework provides an early-stage wave-to-wire tool that links validated hydrodynamic behavior with preliminary PTO design, guiding future experimental and numerical developments toward a fully integrated roll-harvesting WEC.

Presenting Author: Muhammad Hajj Stevens Institute of Technology

Presenting Author Biography: Prof. Muhammad R. Hajj is the George Meade Bond Professor of Ocean Engineering, Chair of the Department of Civil, Environmental and Ocean Engineering, and Director of the Davidson Laboratory at Stevens Institute of Technology. His research spans nonlinear dynamics, fluid mechanics, structural dynamics, and fluid-structure interactions, with applications in aero- and hydro-elasticity, ship hydrodynamics, biomimetically inspired air and underwater vehicles, and energy harvesting. Before joining Stevens in 2018, he was the J. Byron Maupin Professor of Engineering at Virginia Tech, where he also directed the NSF-funded I/UCRC Center for Energy Harvesting Materials and Systems. He earned his B.E. from the American University of Beirut and his M.S. and Ph.D. from the University of Texas at Austin; he is a Fellow of the Engineering Mechanics Institute and has advised 32 Ph.D. students and co-authored more than 170 journal publications.

Authors:

Ruben J. Paredes ESPOL Polytechnic University
David Plaza Stevens Institute of Technology
Jose R. Marin-Lopez ESPOL Polytechnic University
Jia Mi Stevens Institute of Technology
Raju Datla Stevens Institute of Technology
Muhammad Hajj Stevens Institute of Technology