Existing software tools including Capytaine, wecOptTool, and WEC-Sim were used to examine and perform low-order optimization of the hydrodynamics and power performance of a Marson-type device. The device is a segmented nominally circular float that can be divided along variable radial or azimuthal intervals, resulting in configurations suitable for variety of deployment situations (affixed to existing structure vs. free-floating) and requiring a varying number of power-take-offs and power aggregation strategies. The initial objectives of this study were to employ wecOptTool to understand the hydrodynamic power capture potential of different device configurations in a variety of common offshore and nearshore sea-states to identify promising subsets of device configurations, specifically viable numbers of radial and azimuthal sections and overall device size. Once identified, the second aim of this study was to explore low-level models of power-take-off and control strategies for the viable configurations within WEC-Sim: this allowed hydrodynamic and other non-linearities to be included and, after iteration in wecOptTool, arrive at component level models. The goal of this project was not necessarily to converge on an optimal design for each sea state, but to examine trends in performance due to varied design parameters that will help narrow the potential design and market/application space for future, detailed development.

This project had a number of challenges that limited the success of the project. These challenges were primarily due to the challenges in modeling the dynamics of the attenuator WEC directly in WecOptTool. Impedance models were created using WEC-Sim, but these still presented challenges when analyzing in WecOptTool. A final set of batch runs of WEC-Sim simulations provided opportunity for additional analysis. Despite the challenges and limitations of the analysis completed, a number of valuable conclusions could still be made. A floating version of the Marson WEC showed potential as compared to a traditional point absorber of similar dimension, especially for bimodal seas, but efficient PTO design is vital to ensuring success. Further, since the heave modes seemed to dominate the power extraction, it is unlikely that more than 3 floats provides significant benefits. The Marson WEC will also present an opportunity to test and improve the co-design and system identification process for similar WECs involving kinematic chains. Through this project, some valuable design insights regarding the Marson WEC have been achieved, and relevant design challenges have been made clear for the modeling team to improve upon.

This project was supported during RFTS 10.