The near shore oscillating water column (OWC) wave energy plant at Vizhinjam, India had twin 1 m Well's turbines and 1 m linked guide vane impulse turbines as power modules. Performance analysis of the observed records during operation yield significant insight on the dimensioning of the turbine with respect to the caisson. A cycle by cycle analysis of energy capture clearly identifies stalling behavior of the Well's turbine. Similarly, the performance degradation of the linked guide vane due to mechanical problems could be identified. Such analysis is possible as the electrical machine is an induction generator and the moment of inertia of the system is relatively small. It is clear that optimum dimensioning of the turbine is a must with an OWC based wave energy plant.
The Japanese wave energy plant at Sakata port and the Indian wave energy plant at Vizhinjam are the oldest examples of near shore oscillating water column (OWC) based wave energy plants. The results of the Sakata plant has been well documented (Takahashi, 1992, Ojima 1983). The full capacity of the plant could not be fully captured as the turbine size (1.337 m) was smaller than the best theoretical value (Nakata et al, 1991). In contrast, the Indian wave energy plant was initially commissioned with a 2 m Well's turbine, but showed significant no load losses (Ravindran, 1997). Here we present an in depth analysis of the performance results of the Indian wave energy plant.
The caisson of the plant had an opening width of 10 m and a water plane area of 67.5 m2. The best hydrodynamic efficiency (based on model studies) can be attained using a turbine diameter of 2 m (Koola, 1990).
