Study has been carried out a study by MARINTEK in SINTEF to verify and to optimize the iowep – Intentium Offshore Wave Energy Project. The study has been conducted by PhD Jørgen Hals, and by the use of the industry standard software WAMIT.
WAMIT is a frequency domain analysis software for analyzing wave interactions with offshore structures or vessels. Initially is was set up seven geometric variations to optimize the dimensions to the main float; 1. Basic, 2. Low, 3, High, 4. Narrow, 5. Wide, 6. Short, 7. Long. In the analysis it was considered five European wave energy locations with well known wave energy data:
Sem-REV test site in France
EMEC test site in UK
Off Lisbon in Portugal
Haltenbanken off Norway
Belmullet west of Ireland
The use of WAMIT implies linear hydrodynamic theory with some limitations, like inviscid fluid and linear machinery (PTO) forces. As in the current iowep-design, only the heave motion has been considered for power extraction. In a future extension, it could also be considered power extraction through the surge and pitch motion of the main float.
Wave spreading / wave crest length
It has been performed an analysis on the effect of wave spreading, or in other words the longcrestness of the waves. The Ratio of reduction in annual average power due to wave spreading, seems to be in the order of 3-18% depending on geometry and site.
Phase control
Finally, it has been performed an analysis on the effect of phase control of iowep. The Ratio of increase in annual average power due to phase control seems to be in the order of 1,4 to 2,2 times for resistive loading only, depending on geometry and site.
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Offshore WIND staff, January 11, 2012; Image: owep