Hybrid solar-wind-ocean thermal system for zero-energy buildings: Optimization and performance analysis in Australian coastal cities

Growing global demand for sustainable and reliable energy systems has intensified interest in renewable multigeneration technologies for buildings, particularly in coastal regions where multiple energy resources are simultaneously available. In this study, a hybrid solar–wind–ocean thermal energy system is proposed and comprehensively assessed as an integrated solution for supplying electricity, heating, and cooling to buildings, while also producing hydrogen and oxygen as valuable by-products. Building energy demand was estimated using a detailed simulation platform, and system performance was evaluated through thermodynamic analysis coupled with a two-stage optimization framework. In the first stage, an artificial neural network integrated with a genetic algorithm was employed for global optimization. In the second stage, response surface methodology was used to refine the optimal region identified in the first stage and to examine the interaction effects of the most influential operating parameters. The optimized system achieved an exergy efficiency of 59.83% and a total cost rate of 99.04 $/h, showing improved performance relative to the initial global optimization stage. The results demonstrate that the proposed hybrid configuration can provide a balanced and resilient renewable energy supply while significantly reducing reliance on conventional energy sources. Among the investigated coastal climates, Melbourne showed the most favorable overall performance due to its stronger renewable energy potential. The findings further indicate that the system is capable of meeting annual building demands for electricity, heating, and cooling while also generating surplus hydrogen and oxygen, underscoring its potential to support sustainable and zero-energy building strategies. In addition, by displacing conventional electricity generation, the proposed system can avoid approximately 2078 tons of CO2 emissions annually in Melbourne, highlighting its environmental advantages and its potential contribution to cleaner coastal energy systems.