Performance evaluation of a novel photo-thermal-electric hybrid system

Abstract

Solar thermal power systems are promising electricity generation technology; however, their thermal efficiency is low due to the installed tilt angles and heat losses of solar collectors. Herein, a novel photo-thermal-electric hybrid system that integrates a tilt angle-independent and efficient evacuated U-tube solar collector with a thermally regenerative electrochemical cycle is theoretically conceptualized to evaluate its effectiveness. By developing a mathematical model, analytical expressions for performance indicators as well as the conditions delivering electricity of the hybrid system are deduced. Regardless of tilt angle, calculations indicate that the power density, energy efficiency and exergy efficiency can reach 82.99 W m−2, 8.30 % and 7.61 %, respectively. The hybrid system is less efficient than common silicon photovoltaic cells but is more efficient than some photovoltaic/thermal systems. Exhaustive parametric studies reveal that decreasing thermally regenerative electrochemical cycle internal resistance, ambient temperature or liquid flow rate in evacuated U-tube solar collector and increasing temperature coefficient or evacuated U-tube solar collector inlet temperature can enhance the hybrid system performance. Gradient-based local sensitivity analyses identify that the internal resistance and temperature coefficient of the electrochemical cycle are, respectively, the most and least sensitive variables. A practical case study predicts the hybrid system performance under local weather conditions.