Experimental investigation of energy harvesting from swirling flows using a piezoelectric film transducer

• Published in: Energy conversion and management 2018-09, Vol.171, p.1405-1415
• Main Authors: Stamatellou, Antiopi-Malvina, Kalfas, Anestis I.
• Format: Article
• Language: English
• Subjects: Aerodynamics; Air flow; Alternative energy; Eddies; Electric potential; Energy efficiency; Energy harvesting; Fast Fourier transformations; Fluid dynamics; Fluid flow; Load resistance; Optimization; Piezoelectricity; Pressure; Pressure sensors; Resonant frequencies; Reynolds number; Static pressure; Swirling; Transducers; Turbulent flow; Vibration; Vibration mode; Voltage
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2018.06.081

•Air swirler instead of blunt body used to produce flow field for energy harvesting.•Innovative test rig designed and successfully tested with piezoelectric film transducers.•Improved correlation of output voltage to the static pressure with modified transducer length.•The transducer output was fed to a rectifying circuit and monitored at various fan speeds.•A maximum power output of 3 μW was recorded for a collection time cycle of 20 s. This paper presents the results of energy harvesting experiments with piezoelectric film transducers placed in swirling air flow. The turbulent flow was created by a centrifugal fan –swirler plate arrangement. The air flow field created had a Reynolds number of 15,000–130,000 and a swirl number of 0.3–0.4. The mounting mode of the piezoelectric film transducer allows for varying the position and orientation of the piezoelectric transducer to optimize energy harvesting. First, the output of the piezo-film was monitored by an oscilloscope. Static pressure was concurrently measured using a fast piezo-resistive pressure sensor. Fast Fourier Transformation (FFT) was performed to the output signals in order to understand the interaction of the piezo-film with the turbulent eddies. The mechanical vibration modes were recorded by a camera. Finally, a voltage rectifying circuit board was connected to the piezo-film transducer and the voltage output was monitored in various fan frequencies. The average power output was monitored by measuring the voltage across a load resistance. A configuration of the piezo-film with a rectangular plastic attachment was also tested in order to decrease the eigenfrequency of the piezo-film. The longer piezo-film demonstrated shorter harvesting time cycle and thus increased power output. The optimum performance of the harvester was achieved at the lower mean flow velocities and reached the levels of 3 μW.