Performance of a modified built-middle photovoltaic-thermocatalytic Trombe wall system by fins

Abstract

The photovoltaic-thermocatalytic Trombe wall is attracting attention due to the ability to generate electricity, heat and purify indoor air, while it has the disadvantages of low electrical and degradation performance. Also the overall performance evaluation method of multi-functional Trombe walls still needs to be further improved. To fill these gaps, a modified built-middle photovoltaic-thermocatalytic Trombe wall by vertical fins was proposed in this study. Based on the first and second laws of thermodynamics, the effects of fins spacing and fins height under different solar radiation intensities on the performance were investigated by numerical simulation method. In addition, the performance of this modified system was compared with other relevant systems. The results reveal that the existence of an optimal fins spacing or fins height can maximize the thermal efficiency. The narrower fins spacing and higher fins can enhance electrical efficiency and degradation rate. Without sacrificing or even improving thermal performance, the presence of fins with suitable structural parameters leads to higher electrical and purification performance. Compared with the system with no fins, when the solar radiation intensity is 400 W/m2 and 800 W/m2 respectively, the thermal efficiency, electrical efficiency, degradation rate, and overall exergy efficiency gain relative enhancements of 1.81 % and 2.71 %, 2.47 % and 5.18 %, 2.27 times and 2.19 times, and 3.53 % and 6.67 %; and the overall exergy efficiency reaches 12.26 % and 12.20 % at the fins spacing of 31.25 mm and fins height of 30 mm. The introduction of exergy concept provides an effective way for overall performance evaluation of multi-functional Trombe walls with different grades of energies (products). The obtained thermal exergy and electrical exergy dominate the overall exergy efficiency, and the diffusion exergy accounts for a negligible proportion due to the relatively low concentration of pollutant. In comparison with other relevant systems, the modified system shows the best comprehensive utilization of solar energy, and has great application potential. This study provides a new direction for the performance improvement and assessment of multi-functional Trombe wall systems.