Power output evaluation of a wearable electrically series connected photovoltaic-thermoelectric hybrid device for all-day power generation

A novel wearable electrically series connected photovoltaic-thermoelectric (PV-TE) hybrid device, as promising candidates for achieving wearable self-powered electronics, is developed in this paper. The thermodynamic model for human skin's superficial tissues and hybrid device is established based on steady-state heat transfer to evaluate its power output. Results show that when the temperature difference of PV cell under daytime is in the range of 8 K, the electrically series connection strategy is conductive to decreasing sensitivity of power output to PV cell temperature. Configuring the number of thermocouples with 22 pairs, width of TE leg with 20 mm, thickness of TE leg in the range of 1 mm–2.2 mm, thickness of flexible substrate with 2 mm and inclusive angle with 168^⸰ can maximize the all-day power output. For most hybrid device worn on arm, an electric resistance ratio setting of 1.9 is capable of maximizing power output. Choosing a flexible substrate with thermal conductivity equal to 2 Wm⁻¹K⁻¹ is more favorable for enhancing the power output. The blood perfusion of biological tissues and contact thermal resistance between human skin and flexible substrate have great influence on power generation performance of the hybrid device and must be taken into account.