# Research and Development of a Large-Scale Axial-Flux Generator for Hydrokinetic Power System
## 5 Conclusions  
The main purpose of this paper has been to present the application of virtual prototyping in the assessment of large structures, for which physical prototyping is an expensive and time-consuming approach. It has also presented the strengths of virtual prototyping in the evaluation of design parameters and their influence on searched-for performance. Finally, but not least, it has presented a good sample of the applied scientific approach to a real engineering problematics area that is also very real--green energy harvesting. Next, conclusions are outlined that specifically resulted from the presented study:  
* A large-scale, axial-flux, permanent magnet generator concept was developed with a specific application for a hydrokinetic run-of-river system--a min 10 MW power plant.
* The examined final concept also showed consistent efficiency, even at a mechanical power input increased up to 18 MW.
* The final design concept variant showed \(\approx\)96% efficiency at 10 MW in mechanical power input and \(\approx\)92%--at 18 MW. These values are indicative, and they are a basis for the further development of a detailed design.
* A feasibility study was performed that showed a good perspective on obtaining a viable design solution, marking some critical points. It serves as a good reference point for further design development that will include the specifics of the system and its application.
* A structured approach to assessing electrical machines was demonstrated, using 15 simulations over 9 virtual models (mock-ups), in which the physical model was a challenging and overly expensive alternative. Important design parameters for axial electrical machines were assessed--air gaps, coil thickness, and the number of rotor disks--through dynamic simulations of the developed virtual prototypes.
* Further, the ability of numerical simulations to evaluate relatively easy physical parameters like an electromagnetic field, power loss, torque, etc. is an advantage that enables an engineering analysis of the concept and facilitates its further development. This approach was also demonstrated in this study, presenting its applicability in similar research studies.  
Conceptualization, G.D.T. and K.H.K.; methodology, K.H.K.; software, B.N.Z.; validation, G.D.T. and K.H.K.; formal analysis, G.D.T.; investigation, K.H.K.; resources, B.N.Z.; data curation, B.N.Z.; writing--original draft preparation, K.H.K. and B.N.Z.; writing--review and editing, G.D.T.; visualization, B.N.Z.; supervision, G.D.T.; project administration, G.D.T.; funding acquisition, K.H.K. All authors have read and agreed to the published version of the manuscript.  
This study was financed by the European Union-Next Generation EU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project No BG-RRP-2.004-0005, and by the project KII-06-H47/8 \"Research of innovative AXial induction high-efficiency MOTOrs with squirrel-cage rotor of a new generation for electric vehicles-AxMoto\".  
Not applicable.  
The data presented in this study are available upon request from the corresponding author. The data are not publicly available due to relations with public funding specifics.