Three OWEC Ocean Wave Energy Converter™ models were tested in a wave tank. The test was performed to observe mechanical and electrical responsitivity of working models under controlled hydrodynamic conditions. Models were placed near the middle of the tank and flotationally suspended in water with the buoys partially submerged and the rest of the structure totally submerged. Additional weights were distributed on module damper plates to achieve neutral buoyancy at preferred working depth. As each wave passed, the buoys were raised and lowered thus moving portions of linear electrical generators up and down within tubes. The tubes and other generator parts were maintained relatively stationary by the damper plates which strongly resisted vertical motion due to their placement at a depth where water particle movement from waves was essentially attenuated. The damper plates also countered structure tendency to drift off station. Motion of linear generators produced measurable electrical power from waves ranging 1" to 5" height. Although electrical outputs were slightly low for scale, waves that engaged the structure were only 30% of optimal design levels. The mechanisms of the apparatus functioned as intended and measurable electrical energy was generated from wave motion. This first test was valuable for successfully proving the concept and divulging considerations for subsequent OWEC design development.
While promising, wave tank tests also revealed meritorious deficiencies. Non-resonant buoy actuation delay was promoted by high center of buoyancy and lack of tangential surface resistance to water particle motion. This condition indicated deriving possibly improved wave following capability from partially submerged buoy shapes having low centers of buoyancy and maximal planar contact with the hydroface. Fully submerged, however, these configurations typically embody added mass forces. A most efficient hybrid buoy shape incorporates smooth laminar flow and maximal buoyancy within design parameters.
Whereas inclined reciprocation axes operated favorably to expand buoy capture distance by allowing simultaneous absorption of both the vertical force component of buoyancy and the horizontal time component of buoy/wave crest engagement with respect to wave procession, using buoy displacement for directly raising and lowering associated linear electrical generators caused wave-reciprocation frequency matching problems. Often, the time delay shortened or nullified reciprocation of the rods and associated generators due to their antiphasal movement with ambient wave fields. Although energy conversion was very direct, power generation was diminished during stroke reversal and start-up. Enhanced electrical output is obtained by relocating and improving generator components. The sacrifice of any peak value electrical outputs of the linear generator configuration should be acceptable in comparison to advantages of efficient output produced by a contemplated and proposed electromechanical assembly.
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