# Enhancing Wind Energy Harvesting Using Passive Turbulence Control Devices
###### Abstract
Results showed that the effective wind speed region was integrated with the galloping wind speed region, forming a single region with a high-power output of the harvester. [PERSON] et al. [37] developed a highly flexible galloping piezoelectric energy harvester and optimized the design of the whole system by considering aspect ratio, support system, initial tension, and other factors. [PERSON] et al. [38] studied the effects of roughness location and surface coverage on vibration by the passive turbulence control (PTC) method with surface roughness selective distribution, and the range of \(Re\) was 3.0 \(\times\) 10\({}^{4}\) < \(Re\) < 1.2 \(\times\) 10\({}^{5}\). The results showed that 16\({}^{\circ}\) roughness coverage is effective in the range inducing the reduced vortex-induced vibration (VIV), enhanced VIV, or galloping. [PERSON] et al. [39] theoretically studied a galloping energy harvester with a bluff body of the triangular cross-section using the quasi-steady state approximation method to model the aerodynamic load. They concluded that the maximum power was obtained when the lateral displacement was the smallest with the change in load resistance. On the other hand, [PERSON] and [PERSON] et al. [40; 41] established a quasi-steady state vibration model of a piezoelectric cantilever beam under the condition of small deflection vibration. In addition, they applied the frequency domain analysis method to solve the electromechanical coupling equation by Laplace transform (for a linear system), and put forward the concepts of electric damping and electric stiffness. [PERSON] et al. [42] studied the influence of different cross-section shapes and mechanical parameters of the harvester on the energy harvesting efficiency by establishing a single-degree-of-freedom (SDOF) model, and they theoretically analyzed the potential possibility of galloping energy harvesting. [PERSON] et al. [43; 44; 45] solved a fluid-mechanical-electrical coupling model of flow-induced vibration energy harvesting systems using a concentrated parameter method and the quasi-steady state theory. [PERSON] and [PERSON] [46; 47] developed a harvester in which an equilateral triangular cross-section of the resistive fluid is connected to two piezoelectric cantilevers. When the wind speed is 4.92 m/s, the maximum power can reach 53 mW. [PERSON] and [PERSON] et al. [48; 49; 50] used wind tunnel experiment tests and circuit simulations to derive explicitly the analytical solution of steady-state mechanical and electrical responses of galloping-based energy harvesters with the synchronized switch harvesting on inductor (SSHI) interface. However, the above research of vibration energy harvesting mostly uses a pure resistive load circuit and seldom involves high strength electromechanical coupling of complex nonlinear load circuits. In many cases, strong and weak coupling exist side by side, such as in AC circuits, high-speed motors, elevators, wireless sensors, and some high-strength detection devices. Energy harvesting technologies can be used in conjunction with working sensors or other microelectronic devices. Recently, some researchers have explored the strong and weak coupling effects based on galloping energy harvesting. [PERSON] et al. [51] analyzed the maximum output power of a piezoelectric energy harvester. They proposed that the total power limit could be obtained by tuning the energy harvesting circuit, and they defined three different types of coupling strength by analyzing the closed expression between the mechanical damping and the effective electromechanical coupling coefficient. [PERSON] and [PERSON] [52] studied the optimal output power of system rectifier piezoelectric devices. They proposed design guidelines for devices with a large coupling coefficient and quality factor. In addition, [PERSON] et al. [53] studied the maximum possible power of the harvester with an R-L (resistive load and inductor) circuit interface.