**5. Conclusions**

In this research an OWC wave energy converting system was installed and combined to an offshore template structure for a wind turbine system as a subsystem for power generation. The theoretical results showed that though the converting efficiency in open sea conditions is not very high, it is workable and the efficiency can also be raised by 70% through addition of a front gate. Some substantial conclusions from the study are listed as follows:


Therefore, according to this study for an OWC wave converter installed in an open sea situation, an OWC device with smaller outlet orifice and smaller height of the chamber relative to the water depth will have better performance in terms of the air-velocity and the pneumatic power converted from the wave power. Furthermore, if a gate-opening is allowed at the front side of the chamber (usually in the prevailing direction of the wave propagation), a ratio of gate-opening reaching 45% may give a grea<sup>t</sup> upgrade for the conversion efficiency.

It is noticed that the highest average power obtained in the system is 0.48 MW. When compared to the main structure, established for a wind turbine system of 5 MW power generation, the associated wave energy converting system may produce about 10% of the power obtained from the main system. For a sub-system, the results are quiet encouraging. However, in order to effectively increase the efficiency of ocean energy extraction and avoid negative impacts on the original structure and the environment, there are still many issues to be considered, hopefully to increase the efficiency of energy use and enhance the feasibility of sustainable development.

**Author Contributions:** Conceptualization, H.H.L.; methodology, H.H.L. and G.-F.C.; software, G.-F.C.; validation, G.-F.C., H.-Y.H. and H.H.L.; formal analysis, G.-F.C.; resources, H.H.L.; writing— original draft preparation, G.-F.C. and H.H.L.; writing—review and editing, H.H.L.; supervision, H.H.L.; project administration H.H.L.; funding acquisition, H.H.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study has been financially supported in part by the Ministry of Science and Technology (MOST), Taiwan as indicated in the acknowledgements.

**Institutional Review Board Statement:** Not applicable for studies not involving humans or animals. **Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** This research has been financially supported in part by the Ministry of Science and Technology (MOST), Taiwan under grants "MOST 108-2221-E-110-025-MY2".

**Conflicts of Interest:** The authors declare no conflict of interest.
