Vertical axis wind turbine-driven seawater desalination: aerodynamic analysis, techno-economic and environmental assessment, and multi-objective optimisation

This thesis presents a comprehensive investigation into the development and optimisation of a novel, sustainable solution for off-grid water desalination, driven by vertical axis wind turbines (VAWTs). The investigation examines the performance limitations of VAWTs, specifically their self-starting capability in low-wind conditions. This investigation uses high-fidelity CFD modelling to analyse the aerodynamic impact of novel flatback and J-shape aerofoil modifications. The findings identify an optimised configuration with enhanced self-starting capability, making the turbine more effective in low-wind environments and suitable for off-grid desalination applications. Building upon this VAWT technology, the research proposes and evaluates a battery-free desalination system. This system integrates the VAWT with a compressed air energy storage (CAES) unit to directly drive a reverse osmosis (RO) process, eliminating the need for costly and short-lived batteries. A detailed simulation model demonstrates the technical and economic feasibility of the VAWT-CAES-RO system, establishing its potential as a robust and cost-effective method for freshwater production, achieving a levelised cost of water (LCOW) as low as 1.39 US$/m³. The final phase of this research develops a framework for the system's design by integrating multi-objective optimisation with a life cycle assessment (LCA). This approach balances three key objectives: annual water production, LCOW, and global warming potential (GWP). By employing surrogate modelling and the NSGA-II algorithm, the study evaluates the complex trade-offs between economic cost and environmental impact, showing that a GWP-prioritised configuration can reduce the carbon footprint to 0.70 kg CO₂ eq/m³. This thesis spans the full scope of development, from fundamental CFD analysis and system modelling to comprehensive economic and environmental assessments. This novel, off-grid water system provides a technically proven, cost-assessed, and environmentally-aware solution to global water scarcity, supporting the UN Sustainable Development Goals for clean water and energy.