Energy Harvesting by Using Piezoelectric Flag behind CCylinders in Side by Side Arrangement

Abstract

Since the start of last half century people working on the power production and researchers in energy sector have started paying serious attentions towards the harms of power production from traditional methods such as burning of fuel, coal and oil. During these years, non-traditional ways of producing power such as from renewable energy sources like sun, wind, water etc. have gained a lot of attention due to its environment friendly procedure, less or no pollution, less cost, availability in excess and green nature of energy. The purpose of this study is the energy harvesting using piezoelectric eel behind two cylinders in side by side arrangement. The improvement in power generation by vibrations caused by vortices is studied by performing a series of water-tunnel experiments. Two side by side cylinders in a staggered arrangement, with varied center-to-center gaps are placed in the water tunnel with the fluid flowing uniformly and electrical power is obtained using the vibrating behaviour of the piezoelectric eel caused by vortices in the downstream region. The poor and optimal coupling of different flapping modes with wake flow is observed in the experimental results. It is also demonstrated that the streamwise distance between the fixed end of piezoelectric eel and the line joining the centers of the staggered cylinders, and the center-to-center gap between cylinders have a significant effect on the flapping frequency and amplitudee, resulting variation of the output power of piezoelectric eel. The experiments are carried out for cylinder diameter, 𝐷 = 25 𝑚𝑚 and flag length, 𝐿 = 60 𝑚𝑚 resulting 𝐿/𝐷 = 2.4. Different cases with varying 𝑁/𝐷 values from 1.00 to 2.00 for different values of 𝐺𝑥 from 2.0 to 4.0 were tested. The comparison of flapping and amplitude response at each point for all cases is made to understand the effects of system’s variable parameters on the results and their trends. The power generated at each point was mainly focused for all cases and their comparative study to find optimal configuration. For the low given fluid speed and the cylinder arrangement with 𝑁/𝐷 = 1.00 − 1.25, the continues oscillations and higher output power persisting for a wide range 𝐺𝑥 = 2.0 – 4.0 was oberved, which makes its application in the real-life systems feasible, as air and water usually flow at lower speeds. It is observed that the output power increases with the increase in streamwise gap between cylinders and eel till 𝐺𝑥 = 4.0, higher values were obtained at 𝐺𝑥 = 3.5 − 4.0 for the velocityy, 𝑈∞ = 0.31 𝑚/𝑠, with 𝑁/𝐷 = 1.00 − 1.25. The power generated by these configurations ranges from 5.15 𝜇𝑊 to 5.50 𝜇𝑊. Hence, the stated configurations with 𝑁/𝐷 = viii 1.00 − 1.25 gives a significant advantage over other arrangements as a vibration source of energy harvesting from the flowing water, and the generated power would gradually increase with the streamwise distance. The harvested power comes totally from the renewable sources of energy, does not have any harmful effect on the environment, atmosphere or ecosystem, and can replace small trickle charge and chemical batteries for powering micro electromechanical sensors like the sensors used for structural health monitoring in the remote areas. All in all, this study makes an effective contribution to the field of energy harvesting from striking vortices by setting the streamwise distance and center-to-center distance gap the staggered cylinderical bluff bodies