Usage of wind turbine systems that convert wind energy to electricity is expanding. The present inventor recognized that conventional systems are not suitable for more densely populated regions, are not effective in regions having lower average wind speeds, and are not visually appealing, quiet, and expandable. Accordingly, he devised, among other things, an exemplary vertical-axis wind turbine system that includes a novel wind turbine having cup-like blades that exhibit air-foil characteristics. The air-foil characteristics dramatically improve the efficiency of the turbine, not only making it effective at lower wind speeds than conventional wind turbines, but also more tolerant of extreme wind conditions. The exemplary system is compact and suitable for roof-top and water-surface installations. Additionally, the exemplary system includes a set of one or more hollow-bore field-wound electric generators, which are not only stackable, but selectively engageable based on measured wind speeds to provide full spectrum electrical generation.