**8. Conclusions**

The main goal of this research work is to understand if there are ways to produce more energy in an offshore wind power station. For this, we studied the possibility of co-localized wind and tidal energy. The possibility of placing piezoelectric materials in the structure was also studied. The costs of this type of technology are quite high and, therefore, the possibility of joining several technologies is a way to reduce the costs of installing these technologies separately and, consequently, we produce more energy. To achieve that, an intensive study of all technologies was made.

First, a viable location was chosen for the installation of the project. There is an offshore wind station on Póvoa de Varzim, and because of that, the location chosen was there. Then, the atmospheric conditions were studied. Subsequently, the necessary items for the proposed infrastructure were chosen. The proposed structure was designed in the software used. The structure designed and simulated to study the co-location of the two types of energy was composed of two types of turbines: AR 1500 Tidal turbine and Vestas V164-8.0 Wind Turbine. Finally, the results obtained after some simulations using the software were discussed.

Through the simulations, we managed to produce a high amount of energy through the installed turbines. As it was calculated, the wind turbine produces a greater amount of energy than the tidal turbine. This is due to the fact that the size of the wind turbine is relatively larger because, for the same turbine dimensions, the tidal turbine can produce a significantly greater amount of energy.

The project proved that it is possible to produce approximately 12.5 GWh of energy annually, more or less enough to supply 10 thousand homes. However, the installation of piezoelectric materials did not prove to be viable as it is an expensive technology and does not produce a large amount of energy. Furthermore, these materials would be exposed to critical atmospheric conditions, which would lead to regular maintenance that is not justifiable.

Green energies are quite expensive energies, and offshore energy is no exception. The biggest disadvantage of this project is undoubtedly the high costs of all components as well as installation and maintenance. The fact that we only performed the simulation for a wind turbine and a tidal turbine helps to increase the project costs. An offshore wind farm pays off if the number of installed turbines is higher because it greatly increases the energy produced, and costs do not increase as much with the increase in turbines.

In conclusion, the project presented is very expensive but a very promising project due to the fact that the technologies used are innovative and produce a large amount of clean energy.

In this study, it was assumed that the platform of the WindFloat project also supports a tidal turbine. The tidal turbine used is a turbine that is supposed to be on the bottom, supported by a structure of its own. A study on whether it would be possible to adapt this turbine to the proposed project and whether the floating platform would be able to support the weight of this turbine will have to be carried out.

A major problem with these facilities is the environmental impact. A study on the impact that the project would have at an environmental level also needs to be carried out.

As for piezoelectric materials, a study on these is also effective. This technology will be a good solution if a piezoelectric material is found that is capable of withstanding difficult atmospheric conditions and capable of being more efficient than the materials proposed in this project.

Lastly and most importantly, a detailed economic analysis would have to be carried out. Most of these projects are quite expensive and do not have detailed budgets available, which leads to great difficulty in projecting a correct budget.

**Author Contributions:** Conceptualisation: J.P.N.T. and R.A.M.L.; Software: A.S.D.J.; Methodology: J.P.N.T. and A.S.D.J.; Investigation: J.P.N.T., A.S.D.J. and R.A.M.L.; Formal analysis: J.P.N.T.; writing: A.S.D.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported in part by FCT/MCTES through national funds and in part by cofounded EU funds under Project UIDB/50008/2020. This work was also supported by FCT under the research grant UI/BD/151091/2021.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

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