Self-levelling Platform Concept for a Winch-based, Single Point Absorbing, Wave Energy Converter

Abstract: This report covers a bachelor thesis project to design a concept for a levelling system to a point absorbing wave energy converter that uses a winch with a chain, which has restricted capabilities to bending and thus requires a system which compensates for this. First of all, a literature study was made to see if there were any technologies that could be used, and also a wide search for information about the wave conditions in the Baltic sea were performed to find what requirements would be necessary for the concept to be able to withstand the conditions faced there. Following this, several brainstorming sessions were had to get ideas for different types of constructions that could solve the problem. After multiple ideas had been conceptualized, they were rated in a Pugh matrix with five different criteria which were: 1. mechanical complexity 2. complexity of required motion control 3. complexity of the structure 4. amount of potential critical weak points 5. mass of the system and lastly 6. how symmetrical it could be made. The concept that was deemed most viable out of all them is a cradle that holds the winch-drum and is controlled by a motor to compensate for one angular shift, and this is paired with a mooring system that limits the yawing motion of the entire buoy and thus removes the need for the compensation of that angle. This concept was then modelled in Solid Edge and following this; a stress analysis was made to determine the forces that would act upon the system. These were then used to determine whether the system would live up to the requirements or not with fatigue calculations. Lastly a list of recommended future work is presented.