Abstract
Using ocean wave energy to power saltwater desalination through reverse osmosis (RO) relies on a power take-off (PTO) capable of converting highly variable power to relatively smooth pressurized flow for compatibility with conventional RO systems. In addition to limits in pressure, RO membrane operation guidelines specify a rate of change in pressure less than 70 kPa per second. With a hydraulic PTO, the system requires large volumes of expensive accumulators to meet these constraints. This work introduces several hydraulic PTO architectures and uses coupled numerical models of a wave energy converter (WEC) and the PTO to compare the total accumulator volume required. This study finds that adding a resistive-capacitive network to the baseline parallel-type architecture reduces the required accumulator volume by 48%, adding an active throttling valve gives a 55% reduction, and a series-type architecture requires 75% less volume. It is also shown that meeting the constraint on rate of change in pressure requires an order of magnitude more volume than when it is neglected. This suggests that further work is needed to understand the consequences of pressure variation on RO components and justify this constraint.