Abstract: Inventive systems (e.g., turbines) for harnessing hydroelectric energy are described. The turbines include: (1) a central longitudinal shaft configured to mount and to rotate on a central axis perpendicular to a direction of fluid flow; (2) a plurality of substantially circularly arcing blades designed to couple to the shaft, each of the substantially circularly arcing blades having defined at one end one or more blade apertures; and (3) a fastening sub-assembly including fasteners, the fastening sub-assembly used for coupling the circularly arcing blades to the shaft.

Abstract: Inventive systems (e.g., turbines) for harnessing hydroelectric energy are described. The turbines, includes: (1) a central longitudinal shaft configured to mount and to rotate on a central axis perpendicular to a direction of fluid flow; (2) a plurality of arcing blades coupled with the shaft, the blades extending radially outwardly from the shaft, and the blades including an airfoil cross-section along a substantial length of the blades; and (3) a hydrodynamic cap covering a location where the arcing blades couple with the shaft such that in an operating state of the turbine, presence of the hydrodynamic cap reduces an amount of bypass area, which is area outside a region that is swept by the arcing blades.