Presented study demonstrates the application of actual technologies and tools for the development of a large scale axial flux electricity generator. (1) Background: The specifics of its application – run-of-river site – predefine design requirements, close to wind turbine generator. An extensive study of available solutions is used as a start point for further concept development; (2) Methods: A step based methodology is defined for concept parameters assessment and feasibility study. It demonstrates the advantages of virtual prototyping when assessing various design parameters; (3) Results: Several simulations over built different virtual prototypes provide sufficient information to elaborate an improved design concept. Major result is a ready for detailed design concept, with defined major parameters and studied work behavior; (4) Conclusions: The major outcome is the presentation of the application of virtual prototyping in assessment of large structures, where physical prototyping is expensive and time consuming approach. Application of virtual prototyping at very early product development stage is an effective way to undertake efficient solutions towards the concept of the product.