Conventional heating and cooling systems are energy-intensive, relying on compressor-driven processes. The dwindling supply of fossil fuels necessitates the development of self-powered alternatives. Triboelectric nanogenerators (TENGs) offer a promising solution, converting various mechanical energies (wind, waves, water droplets) into electricity. While TENGs have shown potential in various applications, their application in self-powered temperature control is relatively recent. Ferroelectric materials, exhibiting electrothermal effects, are suitable for temperature regulation when coupled with high-voltage sources like TENGs. Previous research has demonstrated the feasibility of TENG-based electrocaloric refrigeration, but challenges remain in improving TENG voltage output and the performance of ferroelectric ceramics. This research aims to address these challenges by developing a novel self-powered temperature control system with enhanced energy harvesting and temperature variation capabilities.

Extensive research exists on electromechanical transducers and electrocaloric materials. Mishchenko et al. demonstrated a large electrocaloric effect in PbZrxTi1−xO3 thin films. Lead-free ferroelectric ceramics are being explored for environmental reasons. Previous work by Li et al. first proposed using TENGs and PST ceramics for self-powered electrocaloric refrigeration, achieving a cooling power of 4.2 W under a specific electric field. However, limitations in TENG voltage output and the electrocaloric performance of existing materials prompted the current study. This work aims to improve upon previous limitations by optimizing the TENG design for higher voltage output and enhancing the electrocaloric properties of the ferroelectric ceramic.

This study designed a self-powered temperature-changing system (SPT 1.0) incorporating a rotary disc-shaped FEP-rabbit fur TENG and an array of 0.15PT-0.85PST ferroelectric ceramic chips. The TENG's design uses a wind cup to drive the rotation of a rabbit fur-coated rotor against a FEP film stator, generating a high-voltage output. The 0.15PT-0.85PST ceramic was synthesized and its electrothermal properties were optimized through quenching. The system's operation involves harvesting wind energy to rotate the TENG, generating a high-voltage electric field that induces the electrothermal effect in the ceramic chips, resulting in a temperature change in an insulated cup. The system's performance was evaluated by measuring the temperature change and time required for cooling and heating. An optimized version (SPT 2.0) was created by increasing the number of ceramic chips and incorporating cooling components. The 0.15PT-0.85PST ceramics' crystal structure, microstructure, and electrocaloric properties were characterized using XRD, Raman spectroscopy, and SEM analysis. Hysteresis loops were measured to determine the polarization properties at various temperatures.

The fabricated FEP-rabbit fur TENG achieved a maximum open-circuit voltage of 6913 V, a maximum short-circuit current of 85 μA, and a maximum transferred charge of 1.3 μC. The 0.15PT-0.85PST ferroelectric ceramic exhibited an optimized electrothermal effect (ΔTmax) of 1.574 K and an energy harvesting density of 0.542 J/cm³. The SPT 1.0 system achieved a temperature change of 0.49 K in an insulated cup (300K) within 276 s, representing a 31% reduction in cooling/heating time and an 81% improvement in temperature variation compared to prior work. The SPT 2.0, with improvements in design and materials, achieved heating and cooling temperature changes of 1.19 K and 0.93 K, respectively. Characterization of the 0.15PT-0.85PST ceramic revealed a stable crystal structure with good microstructure even after quenching. The hysteresis loops demonstrated high polarization at room temperature, confirming the material's suitability for electrothermal applications. The grain size of the ceramics increased linearly with the quenching time, suggesting a relationship between processing and material properties.

The results demonstrate the successful integration of a high-voltage output TENG and optimized ferroelectric ceramic to create a self-powered temperature control system. The significant improvements in temperature change and response time compared to previous studies highlight the effectiveness of the proposed design and material selection. The achievement of substantial temperature variations (over 1 K) with a relatively small number of ceramic chips demonstrates the scalability and efficiency of the system. The successful operation of the system validates the potential for commercial application, addressing the need for energy-efficient cooling and heating solutions. The application in agricultural settings showcases the potential of using ambient energy for climate control in various sectors.

This research successfully developed a self-powered temperature control system utilizing wind energy, demonstrating significant improvements in both temperature change and response time compared to previous technologies. The optimization of the TENG and ferroelectric ceramic resulted in a highly efficient and scalable system with substantial potential for commercialization in various applications, including agricultural climate control and other areas requiring energy-efficient temperature regulation. Future research could focus on further optimizing the system's efficiency, exploring alternative energy harvesting mechanisms, and investigating the application of this technology in diverse contexts.

The current system's performance is dependent on wind availability. Further research is needed to explore the use of alternative energy sources or energy storage mechanisms to address this limitation. The long-term durability and stability of the TENG and ferroelectric ceramic under continuous operation also need further investigation. The study focuses on a specific application in agricultural greenhouses; broader applicability across different environmental conditions and applications should be explored.