A novel photo-thermal-electric hybrid system comprising evacuated U-tube solar collector and inhomogeneous thermoelectric generator toward efficient and stable operation

Solar-driven thermoelectric generator is an enticing avenue for sustainable global electricity generation. Nevertheless, its broad adoption is impeded by two significant challenges: low efficiency and reliability. To address these challenges, a novel hybrid system that integrates angle-independent evacuated U-tube solar collector (EUSC) with inhomogeneous thermoelectric generator (ITEG) is first proposed in this paper. The power density of the hybrid system is predicted to be 26.1 W m−2 with an efficiency of 2.61% under AM 1.5, signaling considerable potential for performance enhancement. Extensive parametric studies demonstrate that raising the inlet water temperature for EUSC and the spatial inhomogeneity coefficient of ITEG, reducing external environmental temperatures and fluid flow rate within the EUSC, and optimizing the number and geometric characteristics of ITEG can improve the output performance. By optimizing the number of thermocouples in ITEG, the power density could reach 39 W m−2 when the spatial inhomogeneity coefficient of ITEG is 0.83. Gradient-based local sensitivity analyses further identify that the geometrical characteristics of ITEG and inlet water temperature of EUSC are, respectively, the most and least sensitive variables. These findings offer valuable insights into the intricate integration and operational mechanisms pivotal for achieving efficiency and stability in solar-driven thermoelectric generator power systems.