Wave Energy Converter Cone-Cylinder Buoy Dimension Optimization using Backpropagation Neural Network and Genetic Algorithm Method

Abstract

Wave energy converter (WEC) technology is currently being explored as one of most promising renewable energy sources. Heaving point absorber is the most used type of WEC because it has a shape that easily adapts to wave conditions. The unreliability in extreme weather and dependence on buoy size caused WEC technology to be underutilized. Research to utilize shape changes is needed to reduce WEC dependence on buoy size. The purpose of this research is to design a WEC buoy showing maximum power absorbed with the minimum value of volume and comparing it with the existing buoy shape such as the basic cone-cylinder and bullet shape. The research begins by determining the variant of dimensions for the cone-cylinder buoy head cylinder height with the value of 0.40, 0.55, 0.70, 0.85, 1.00, and 1.15 in meters and cone concavity diameter with the value of 3.20, 3.90, 4.60, 5.30, 6.00, 6.70, 7.40, and 8.10 in meters. The Simulation process will use Ansys AQWA software with heaving motion values as output to calculate the absorbed power. The optimization process uses the Backpropagation Neural Network (BPNN) method followed by the Genetic Algorithm (GA) on MATLAB software. The optimized parameters will be simulated to validate the prediction of GA. For the buoy volume BPNN training, the best setting is 2 hidden layers, 5 nodes, Log-Sigmoid activation function, 70% training ratio, 15% validating ratio, and 15% testing ratio with 4.59E-09 mean squared error (MSE). For the buoy power absorbed BPNN training, the best setting is using 4 hidden layers, 5 nodes, Tan-Sigmoid activation function, 70% training ratio, 15% validating ratio, and 15% testing ratio with 5.95E-25 MSE. For GA the best setting is generating 500 chromosomes with using weight 0.5. The result of GA is 1150 mm of cylinder height and 7146.10 mm of cone concavity diameter, simulation shows 12.8503 m3 of volume and 3379.00 Watt of power absorbed.