Integrated Design for Wave Energy Converter Farms: Assessing Plant, Control, Layout, and Site Selection Coupling in the Presence of Irregular Waves

TL;DR

The paper addresses the inadequacy of single-domain WEC farm designs by advocating an integrated design framework based on control co-design (CCD) that couples plant geometry, layout, and PTO control with site and wave type considerations. It employs a frequency-domain model of multiple heaving cylinder WECs, irregular waves via the JONSWAP spectrum, and MS-based hydrodynamic coefficients to explore how plant, control, and layout interact under realistic sea states, using the objective $p_v$ (average power per unit volume) over $n_{yr}=30$ years. Key findings show strong cross-domain couplings: optimal geometry and PTO parameters shift with site and wave climate, layout interacts with control, and irregular waves dampen array interactions (q-factor) compared to regular waves, underscoring the need for integrated optimization. The work provides high-level guidelines for moving toward truly integrated WEC farm design, with implications for site selection, wave-state modeling, and multi-domain optimization in practice.

Abstract

A promising direction towards reducing the levelized cost of energy for wave energy converter (WEC) farms is to improve their performance. WEC design studies generally focus on a single design domain (e.g., geometry, control, or layout) to improve the farm's performance under simplifying assumptions, such as regular waves. This strategy, however, has resulted in design recommendations that are impractical or limited in scope because WEC farms are complex systems that exhibit strong coupling among geometry, control, and layout domains. In addition, the location of the candidate site, which has a large impact on the performance of the farm, is often overlooked. Motivated by some of the limitations observed in WEC literature, this study uses an integrated design framework, based on simultaneous control co-design (CCD) principles, to discuss the impact of site selection and wave type on WEC farm design. Interactions among plant, control, and layout are also investigated and discussed using a wide range of simulations and optimization studies. All of the studies were conducted using frequency-domain heaving cylinder WEC devices within a farm with a linear reactive controller in the presence of irregular probabilistic waves. The results provide high-level guidelines to help the WEC design community move toward an integrated design perspective.

Figures (7)

• Figure 1: Capacity factor of a single WEC with a prescribed design. The rated power is calculated as the maximum weighted power from the West Coast simulation and is used in the East Coast simulation (which results in a lower capacity factor and, thus, lower economic competitiveness of the WEC for the East Coast).
• Figure 2: Optimized layout from the concurrent plant and layout optimization study for West and East costs. Green circles are drawn in scale based on the optimized radius of the WEC devices. The orange circles, also drawn in scale, indicate a safety distance constraint imposed to allow maintenance ships to pass.
• Figure 3: Smoothing effect appearing in the q-factor calculation for a range of WEC farm layouts for unidirectional irregular waves.
• Figure 4: Optimal plant and control variables for regular waves.
• Figure 5: Power landscape in terms of layout for regular and irregular wave types for two WECs with prescribed design and control parameters.