This thesis presents two wave energy converters (WECs), an oscillating surge wave energy converter and a heaving point absorber wave energy converter and a reverse osmosis desalination system which are numerically modeled and compared. The primary objective was to assess and contrast their performance in terms of Freshwater Production and Specific Energy Consumption (SEC) over a variety of realistic sea states, which are specified by significant wave heights (1–5 meters) and energy periods (5–9 seconds) incorporating a particular wave spectrum for irregular waves.

An open source MATLAB based solver was used to integrate hydrodynamic data from frequency-domain Boundary Element Method (BEM) solver into time-domain simulations. Both devices harnessed mechanical energy, which was then sent to the reverse osmosis unit via a hydraulic piston configuration. Power matrices displaying SEC, water production and permeate concentration were used to present the results, offering a direct comparison.

Results showed that the two devices differed significantly. Only in high-energy wave circumstances did the heaving device operate effectively, exhibiting low SEC of 2-4 kWh/m³ and significant freshwater output in certain sea states. However, in moderate or lower-energy seas, its efficiency significantly decreased. With SEC normally ranging from 2 to 4.5 kWh/m³ and consistently higher freshwater output, even in milder sea conditions, the oscillating surge device, on the other hand, showed more stable performance. According to the study, the oscillating surge device can provide desalinated water with salt concentrations below the threshold of 600 ppm suggested by the World Health Organization in the majority of sea states, whereas the heaving device often crosses this limit, with the exception of energetic wave conditions. These findings are in good alignment with previous studies on wave-powered desalination.

Limitations include the exclusion of operational issues such as membrane fouling or long-term system degradation, the assumption of linear interpolation for calculating intermediate sea states, and possible errors resulting from simplified models.

The use of complex interpolation techniques to improve accuracy, more simulations over multiple sea states, and experimental validation of results are some suggestions for future research. Additionally, combining environmental and economic evaluations will help in determining if larger-scale deployment of these wave-powered desalination systems is feasible. This study highlights oscillating surge devices as a strong option for sustainable freshwater generation and offers insightful information for enhancing wave energy desalination.