A vertical turbine system comprising includes a turbine having a vertical rotational shaft, a pair of oppositely disposed circular frame members radially affixed to the shaft, and a plurality of vanes having a generally rectangular profile, each vane rotatably affixed to the circular frame members at the ends of its leading edge, with rotation of the vanes about the leading edge limited to a maximum of about 40° to about 80°. A generator is operatively connected to one end of the shaft for converting rotational energy of the shaft into electrical energy, the lower end of the shaft is affixed to a ground surface, and the generator is maintained in a generally stationary position as the turbine rotates about the shaft. The vertical turbine system can be adapted for wind or water use.