Estimation of Stress in the Inner Framework Structure of a Single Heaving Buoy Wave Energy Converter

Abstract

This paper details a method for strain measurements in the inner framework structure of the single heaving buoy wave energy converter (WEC). This type of the WEC consists of a linear direct drive generator placed on the seafloor and connected to the floating buoy through the connection line. The study focuses on estimation of stress in the inner framework structure of the WEC using strain measurements in the material. Stress in ocean structures is as important as maximum stress. The offshore experiment took place at the Lysekil research site a few kilometers from the Swedish west coast. Stresses had the maximum value when the translator hit an end stop. Interesting observations were made: compressive stress occurred in the framework crossbar at a sea state of 1.32-m waves, but both compressive and tensile stresses occurred at a sea state of 3.2-m waves. A computational procedure employs good results. Error estimation is calculated and represented. This work is a step that may influence future design of wave energy devices in terms of the material aspect, survivability in a hard wave climate, and cost-effective renewable energies.