Long-term power degradation testing of piezoelectric vibration energy harvesters for low-frequency applications

Abstract

Piezoelectric energy harvesters represent a viable and well-proven solution to convert ambient vibrations into useful electric power within a number of modern life applications. Whilst a large amount of studies has focused on improving power output from these devices, relatively little research has been directed to investigate how these devices degrade over time and the effect this has on long-term power generation. This paper, therefore, aims to experimentally investigate how piezoelectric vibration energy harvesters degrade during long-term operation in realistic harvesting conditions. The harvesters tested are unimorph cantilevers based on three of the most commonly used piezoelectric options: polyvinylidene fluoride (PVDF), Macro Fiber Composite (MFC), and Quick Pack (QP). Testing was carried out under single-frequency excitation (10–40 Hz) of 1g amplitude for three million vibration cycles. Our results show that the natural frequency and the optimum load resistance of the harvesters may vary during prolonged operation. Importantly, a larger cumulative variation in natural frequency and optimum load resistance yields a larger variation in power output, thereby linking the variation in power to the variation of the mechanical and/or electrical properties of the harvesters. Comparing the average power values over the testing period we found that increasing the tip mass does not necessarily improve the average power output, suggesting that a larger tip mass may exacerbate the degradation of the mechanical and/or electrical properties of the harvester. This was particularly evident for the stiffest QP harvesters which showed the highest signs of power degradation; nevertheless, QP harvesters still managed to demonstrate the highest power density values. When cost consideration is taken into account in the assessment, PVDF harvesters managed to demonstrate the highest power density to cost ratio.

Planform geometry effects of piezoelectric wind energy harvesting composite inverted flags

“…In these cases, batteries can be replaced with energy harvesting modules which convert ambient energy into electric power [11][12][13][14][15]. Ambient energies that can be harvested from the environment include kinetic energy from wind [16][17][18], waves [19], water flows [20][21][22] and ambient vibration [23][24][25][26][27], thermal energy in the form of temperature variations in space or time [27][28][29], solar radiant energy [30], electromagnetic energy from radio and television broadcasting [31], chemical energy from salinity or other concentration gradients [32], and combinations thereof such as wind and wave [33], wind and vibration [34,35], wind and solar [36,37] and vibration and solar [38].…”

Mechanical Durability Assessment of an Energy-Harvesting Piezoelectric Inverted Flag

“…In fact, micro-cracks have been seen in several studies, e.g., [25,26], and their existence is always an indication of degradation. Later, Hirst et al [27] experimentally measured the long-term operation performance of piezoelectric vibration energy harvesters made from three of the most used piezoelectric materials, including PVDF, MFC, and Quick Pack, for low-frequency applications. They showed that higher cumulative variations in natural frequency and optimum load resistance lead to degradation in the mechanical and electrical properties of the harvesters.…”

Design, modeling, and analysis of piezoelectric energy harvesters

“…[159], if the acceleration level is below 6 m/s 2 , the voltage degradation is negligible, as shown in Ref. [160] compared the fatigue behavior of PVDF, MFC, and PZT materials for three different tip mass ratios. The power output made from these materials over the cyclic load is shown in Fig.…”

“…The power output made from these materials over the cyclic load is shown in Fig. 1-37 [160]. PVDF does not demonstrate power reduction due to the fatigue, while there is a power reduction for the MFC and PZT.…”

“…1-37. The voltage degradation for three different tip mass ratios for (a) PVDF, (b) MFC, and (c) Quick Pack made of PZT [160]. 68 Fig.…”