Helmholtz piezo-electric power generation

Experimental research of power generation using a piezoelectric device, in conjunction with a Helmholtz resonator, was conducted in a low-speed wind tunnel. RMS power levels on the order of 40 milliWatts were recorded for a single piezoelectric tab placed in the rectangular inlet of a Helmholtz resonator. For a freestream velocity of 5-90 ft/s, piezoelectric power production was maximized when the piezoelectric tab was placed at the bottom of the Helmholtz orifice, flush with the top surface of the wind tunnel and within a turbulent boundary layer. When the piezoelectric tab was attached on the cavity side of the orifice opening (i.e. not flush with the top surface of the wind tunnel), the piezo produced the second-highest RMS power. The production of power using this method shows the feasibility of someday using this as a clean, renewable, passive energy source. Flow visualization showed that the flow entered the sealed Helmholtz resonator near the downstream end of the orifice and exited at the upstream end, regardless of piezo orientation. The flow also oscillated upon entering the resonator, and the magnitude of the circulatory air increased with increasing velocity.