Model validation and improved PTO modeling of a field-deployed wave energy converter with tethered heave plate

Rigorous incremental testing and validation are essential to advancing wave energy converter (WEC) technology. Although laboratory wave tank testing remains common, it poses challenges in scaling hydrodynamic responses and power take-off (PTO) dynamics. These issues are more pronounced for WECs with tethered heave plates due to complex interactions between the structure, tether, heave plate, and PTO; all of which often exceed tank depth and scaling limits. Field testing enables full-system evaluation but introduces practical limitations, including environmental variability, limited sensing, and measurement uncertainty. A knowledge gap remains in how to overcome these limitations to extract meaningful insights and validate WEC numerical models using field test data. Moreover, full-scale PTOs exhibit significant nonlinearities, such as generator inertia, internal losses, and inefficiencies across the full energy conversion chain, that are not captured in current PTO models. This highlights the need for improved modeling techniques to realistically estimate useful power and energy output. This study uses a field-deployed WEC with a tethered heave plate to demonstrate how combining statistical and spectral analyses enables comprehensive insight and validation of WEC models using field data. It also advances PTO modeling by incorporating generator inertia and fitting a parametric relationship between shaft speed and useful power based on PTO dynamometer test data. This approach predicted power and energy within 9% of field measurements, whereas conventional models overestimated these output by up to a factor of 3. The improved PTO modeling yields more realistic levelized cost of energy (LCOE) estimates to better guide future full-scale WEC development.