Abstract
The focus of this study is to investigate co-located offshore wind-wave systems to enhance the robustness and technoeconomic viability of Marine Renewable Energy (MRE) projects on the NC coast by modeling and assessing shared mooring systems. A portfolio optimization model is developed, and analyses are conducted to assess the number and type of MRE devices/designs considering site-dependent technology and transmission system costs. The study also aims at investigating the potential constraints on the number of wind turbines per site location accounting for curtailment and maximum physical limits within the spatial marine area of the energy collection system of the portfolio. The comprehensive approach proposed in the study facilitates an in-depth economic assessment of the systems' performance under extreme conditions. To determine extreme ocean conditions expected to recur with a 100-year frequency, Extreme Value Analysis (EVA), a statistical technique used to extrapolate existing data, is performed on the NC coast. Using data from the WAVEWATCH III model covering the period from January 2009 to December 2013, combinations of different wind speeds, significant wave heights, and wave periods are considered in the analyses. Next, ANSYS-AQWA is employed to develop a numerical model and simulate the interaction of waves with floating wave point absorbers and the corresponding mooring line forces under extreme ocean conditions. The focus is on the Sandia National Laboratories two-body floating point absorber RM3 device, given the availability of documented information. Environmental loadings are assessed using the Joint North Sea Wave Project (JONSWAP) wave spectrum. The water depth considered for the purpose of this analysis is 40 m, which can be deemed suitable for both fixed-bottom offshore wind turbines (OWTs) and the RM3 device. A recommended distance of 10 times the rotor diameter between OWTs is utilized in the analyses in order to avoid wake effects. Several mooring scopes, in accordance with fixed-bottom offshore wind turbines with rated power of 5 – 18 MW required spacing are considered in the analyses. The impact of different mooring scopes on required RM3 device mooring line length and diameter, meeting ultimate limit states requirements, is determined and the cost of the mooring system in different mooring scopes is estimated. Two different configurations are considered in the analyses: one in which three wave energy converters share an anchoring point, and the second in which six wave energy converters share an anchoring point. Finally, the total power produced by WECs in these shared anchoring configurations is determined, providing insights into the economic feasibility of co-located systems in different regions of the NC coast.