Direct-drive ocean wave-powered batch reverse osmosis

Abstract: Ocean waves provide a consistent, reliable source of clean energy making them a viable energy source for desalination. Ocean wave energy is useful to coastal communities, especially island nations. However, large capital costs render current wave-powered desalination technologies economically infeasible. This work presents a high efficiency configuration for ocean wave energy powering batch reverse osmosis. The proposed system uses seawater as the working fluid in a hydro-mechanical wave energy converter and replaces the reverse osmosis high-pressure pump with a hydraulic converter for direct-drive coupling. This allows for minimal intermediary power conversions, fewer components, and higher efficiencies. The concept was analyzed with MATLAB to model the transient energy dynamics of the wave energy converter, power take-off system, and desalination load. The fully hydro-mechanical coupling, incorporating energy recovery, could achieve an SEC and LCOW as low as 2.30 kWh/m3 and $1.96, respectively, for different sea states. The results were validated at the sub-system level against existing literature on wave energy models and previous work completed on batch reverse osmosis models, as this system was the first to combine these two technologies. SEC and LCOW values were validated by comparing to known and predicted values for various types of RO systems.