Abstract
A six degree of freedom (6DOF) point-absorber wave energy converter (WEC) called LUPA is being developed at Oregon State University. This research focused on analyzing a full- scale LUPA, called LUPA20, to answer the following questions: 1) How does a full-scale WEC perform due to various factors; 2) What are the implications of using a mooring system attached to a WEC; 3) How does a mooring system affect the “optimal” power take-off (PTO) damping coefficient; 4) How does a WEC affect the incoming waves? One of the first parts of this research consisted of conducting an exhaustive power take-off (PTO) damping coefficient search to obtain the “optimal” PTO damping coefficients of LUPA20. Those “optimal” PTO damping coefficients were used to determine the energy production of LUPA20. The results indicate that LUPA20 has an approximate power rating of 96 KW when analyzing the average power results of time domain simulations using a certain range of sea states. To develop a comprehensive LUPA20 model, a mid-water float mooring setup was implemented into the LUPA20 time domain simulations. Simulations were run using various extreme sea states to determine the effects mooring lines might have on LUPA20. The power results indicate the mooring lines have a relatively large effect on the power production. This is evident in the 4.7% difference between the peak power values and the 6.9% difference between the average power values. A PTO damping coefficient sensitivity study was conducted to determine whether the “optimal” PTO damping coefficient change when mooring lines are implemented. The PTO damping coefficient sensitivity study indicated mooring lines do not have a significant effect on the “optimal” PTO damping coefficient. As well as understanding the effects mooring lines have on WEC performance, understanding the effects LUPA20 has on the incoming waves was also studied. A transmission coefficient (K_t) analysis was conducted to determine how much energy LUPA20 is absorbing from the incoming waves. The minimum K_t is 0.84, which indicates LUPA20 can absorb a maximum of approximately 16% of the incoming wave energy.