The MBARI-WEC: a power source for ocean sensing

Abstract

Interest in wave energy converters to provide autonomous power to various ocean-bound systems, such as autonomous underwater vehicles, sensor systems, and even aquaculture farms, has grown in recent years. The Monterey Bay Aquarium Research Institute has developed and deployed a small two-body point absorber wave energy device suitable to such needs. This paper provides a description of the system to support future open-source access to the device and further the general development of similar wave energy systems. Additionally, to support future control design and system modification efforts, a set of hydrodynamic models are presented and cross-compared. To test the viability of using a linear frequency-domain admittance model for controller tuning, the linear model is compared against four WEC-Sim models of increasing complexity. The linear frequency-domain model is found to be generally adequate for capturing system dynamics, as the model agreement is good and the degree of nonlinearity introduced in the WEC-Sim models is generally less than 2.5%.

Wave Energy Converter Power Take-Off Modeling and Validation From Experimental Bench Tests

“…As expected, a weak dependence on hydraulic pressure is exhibited. electromagnetic torque, as shown in (1). The friction torque present in the motor τ (em) fr can be modeled as the superposition of the Coulomb and viscous damping (a similar approach has been used for the rod friction model in Section III-C) [2], [13]:…”

“…An ongoing study is focused on improving predictive modeling capabilities for the WEC and potentially making changes to the design to improve performance. The previous work regarding the MBARI-WEC [1] presented two different numerical models of the full MBARI-WEC system, accounting for hydrodynamic, PTO, and mooring dynamics, where the PTO is considered as a simplified black-box model. As part of this project, a new numerical PTO model to better describe the complex nonlinear dynamics of the PTO system is being developed.…”

Design Proposal and Feasibility Analysis for a Near-Surface Wave-Powered Profiling Float

“…In [13], the authors report an operational two-body WEC similar to the design presented here in that it employs a surface-tracking element and a sub-sea heave-plate connected with a compliant tether. Our work differs from this approach by virtue of the surface-tracking element being necessarily submerged.…”