**5. Conclusions and Future Works**

The development of improved installation and maintenance procedures for technologies that harness energy from ocean currents is a promising research field that needs to be studied in detail in order to achieve a successful future commercialization of these technologies. In this paper, we have explained the procedures for manual and automated installation and maintenance maneuvers for gravity-based first generation TECs, and have also carried out an economic-financial evaluation in order to highlight the merits of automated installation and maintenance maneuvers for tidal energy technologies. Some of the potential benefits that the use of these maneuvers could provide are the following: (i) an increase in the competitiveness of these technologies; (ii) a reduction in human resources and the number and duration of installation and maintenance operations; (iii) the use of cheaper general purpose ships instead of high cost special vessels for maintenance operations; and (iv) a higher project profitability, among others. We have conducted a numerical case study of a TEF in the Alderney Race (UK). This farm comprises 42 TECs of 1.2 MW, and the study was carried out with the objective of determining the economic-financial viability of the project when employing either automated or manual installation and maintenance maneuvers. After applying the economic-financial procedure explained throughout this paper to the case study, we attained results indicating that the project would, in both cases, obtain a good profitability and can consequently recommend investment from both accounting and financial points of view, since the benefits produced from the first year are good. We have additionally discovered that the profitability is even greater when employing devices capable of performing automated maneuvers. The aforementioned results also indicate that the variables that have the greatest influence on the profitability of the project are, in the case of both types of maneuvers, the AEP, the price of energy and the interest rate. Finally, having attained the results of the case study, we can conclude that the economic-financial methodology employed is useful as regards modeling different renewable energy projects, as is also the case of the manual and automated installation and maintenance procedures for first generation TECs presented in this work. This methodology additionally has an advantage in that it could, with minor adaptations, be used for other kinds of offshore renewable energy projects and TEC designs. Our future research will be focused on the application of this model to other offshore renewable energy projects.

**Author Contributions:** E.S., R.M. and J.A.S. conceived, designed and performed the proposed methodology and the case study. Additionally, E.S., R.M. and J.A.S. analyzed the data and participated in writing the paper.

**Funding:** This research has been supported by the Spanish Ministerio de Economía y Competitividad under Research Grants DPI2014-53499-R.

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

*Energies* **2019**, *12*, 2464
