Hybrid tribo-thermoelectric generator for effectively harvesting thermal energy activated by the shape memory alloy

Highlights: • A thermally driven shape memory alloy-wire based hybrid generator (SW-HG), which can generate the triboelectricity, is proposed. • The forces rotating by phase change of shape memory alloy-wire was theoretically analyzed with torque and fulcrum. • Various tests were conducted depending on the temperature to confirm the characteristics of the SW-HC during rotation. • This SW-HG was simulated as a monitoring sensor based on the electrical output according to the temperature. Thermal energy is generated from all equipment during operation. Likewise, thermal energy exists everywhere and dissipates uselessly. It is necessary to transform thermal energy into renewable electrical energy by utilizing materials and devices exhibiting unique features of thermal properties. Shape memory alloys (SMAs) consisting of a compound of nickel (Ni) and titanium (Ti), operate based on unique thermomechanical properties, such as shape memory effect (SME) and superelastic effect (SE). Due to these two effects, SMAs are possible to be deformed and recovered by external heat. One-dimensional SMA wire (SW) can effectively harvest wasted thermal energy by the phase change in SMA from a wrinkled state to a straight state in order to generate continuously rotating energy with two sheaves. In this paper, we propose a thermally-driven SMA-wire based hybrid generator (SW-HG), including a disk-TENG and thermoelectric generator (TEG) which lead to generate a high voltage and large current, respectively. In addition, the operation principle of rotating by the deformation and the recovery of the SW at the phase-change temperature are systematically investigated as well as analyzed using two theoretical models. The unique thermomechanical behavior of the SW-HG is applied to commercial vehicles using output signals for the real-time temperature monitoring inside the engine room. Considering these unique features of SW, the SW-HG is expected to be dependable devices for IoT applications as well as can effectively convert surrounding wasted heat energy into reusable electrical energy in real life.