Thermal-mechanical-electrical energy conversion system based on Curie effect and soft-contact rotary triboelectric nanogenerator

Untapped thermal energy, especially low-grade heat below 373 K from various sources, namely ambient, industries residual, and non-concentrated solar energy, is abundant and widely accessible. Despite that, there are huge constraints to recycle this valuable low-grade heat using the existing technologies due to the variability of thermal energy output and the small temperature difference between the heat source and environment. Here, a thermal-mechanical-electrical energy conversion (TMEc) system based on the Curie effect and the soft-contact rotary triboelectric nanogenerator (TENG) is developed to recycle thermal energy in the mid-low temperature range. According to the phase transition mechanism between ferromagnetic and paramagnetic, disk-shaped ferromagnetic materials can realize stable rotation under external magnetic and thermal fields, thus activating the operation of TENGs and realizing the conversion of thermal energy and electrical energy. During the steady rotation process, an open-circuit voltage (V_OC) of 173 V and a short-circuit current (I_SC) of 1.32 µA are measured. We finally obtained a maximum power of 4.45 mW in the actual working conditions, and it successfully charged different capacitors. This work provides a new method for mid-low temperature energy harvesting and thermal energy transformation and broadens the application of TENG in the field of thermal energy recovery.