A Fundamental Study Of Mini-Turbine Blades For Urban Applications

Abstract

Urban environments contain high densities of wind energy that are inaccessible to large wind turbines of the classical "windmill" design. By exploring small-scale vertical-axis wind turbines (VAWTs), wind energy can possibly be harvested from the constrained spaces within cities. A thorough and detailed investigation of offset pitch angle, relative blade size, camber, thickness, and sweepback angle for straight blades was done in a wind tunnel. Mini-turbines with chordlength to diameter ratios (c/D) equivalent to commercial VAWTs do not operate at the small scales of mini-turbines. On the other hand, mini-turbines with large c/D produce the most power. The standard NACA 0015 straight blade with zero offset pitch angle produces the highest coefficient of power, CP. Adding sweepback reduces CP but improves self-starting capability. Other unconventional designs and numerical models are investigated. Although the design and behavior of large-scale VAWTs has been documented in previous literature, mini-turbines show significantly different properties which indicate promise for practical application in the urban environment.