The effects of the design and optimization of trapezoidal channels and baffles on the net power density of proton-exchange membrane fuel cells (PEMFCs) are studied. The significant effects of the length of upper and lower sides of the trapezoidal cross section and the number and position of baffles on the net power density of PEMFC have been investigated. It is found that at the same flow rate, changing the effective contact surface between the flow channel and the gas diffusion layer can tremendously improve the current density of fuel cells; moreover, the performance of a PEMFC based on the addition of a baffle can be further improved. The results show that the trapezoidal cross-sectional flow channel with baffles has higher efficiency and better overall performance compared with a basic straight flow channel. In addition, the response surface was used to optimize the trapezoidal cross-sectional flow channel by considering the power loss of output power and the flow rate. The optimal result was obtained with an upper side length of 1.234 mm, a lower side length of 1.8 mm, and a baffle from the entrance at 9.5 mm, increasing the net power density by 4.347%.

Currently, the application of triboelectric nanogenerators (TENGs) in energy harvesting and self-powered sensors has garnered widespread attention. Developing TENGs with excellent electrical performance, good resilience, and durability remains a challenging task. In this study, we proposed a porous graphene–Ecoflex triboelectric nanogenerator (PGE-TENG). Using a sacrificial sugar templating method, few-layer graphene (FLG) was thoroughly mixed with Ecoflex to prepare a flexible porous sponge. By combining the conductive sponge with conductive silver fiber fabric, a TENG with mechanical, conductive, energy harvesting, and pressure-sensitive properties was fabricated. To improve the output performance, the optimized PGE-TENG, achieved by systematically controlling the mass ratio of FLG to Ecoflex, exhibited a 220% enhancement in frictional–electrical performance compared to the non-optimized TENG. Furthermore, the instantaneous power density of the PGE-TENG reached 174 mW m⁻². Thus, it can power small electronic devices and serve as a pressure sensor to respond to pressure signals. Importantly, the PGE-TENG exhibited over 19 times higher resilience and over 5 times higher pressure resistance compared to the non-optimized TENG, with good stability during continuous pressing and long-term use. This study demonstrated a low-cost and simple method for preparing high-performance TENGs; through the use of Internet of Things (IoT) technology, the single-electrode mode PGE-TENGs can be integrated into real-time control switch systems for smart homes, enabling the identification of trigger signals for smart home modules (e.g., lamps, doors, fans, and humidifiers) and controlling their operating status. This advancement provided valuable insights into the development of TENG devices in smart sensing applications.

Composite materials are increasingly used in wind blade because of their superior mechanical properties such as high strength-to-weight and stiffness-to-weight ratio. This paper presents vibration and damping analysis of fiberreinforced composite wind turbine blade with viscoelastic damping treatment. The finite element method based on full layerwise displacement theory was employed to analyze the damping, natural frequency, and modal loss factor of composite shell structure. The lamination angle was considered in mathematical modeling. The curved geometry, transverse shear, and normal strains were exactly considered in present layerwise shell model, which can depict the zig-zag in-plane and out-of-plane displacements. The frequency response functions of curved composite shell structure and wind blade were calculated. The results show that the damping ratio of viscoelastic layer is found to be very sensitive to determination of magnitude of composite structures. The frequency response functions with variety of thickness of damping layer were investigated. Moreover, the natural frequency, modal loss factor, and mode shapes of composite fiber reinforced wind blade with viscoelastic damping control were calculated.