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This study designed and optimized the system parameters for a photovoltaic thermal system (PV/thermal system) combined with reflectors. Moreover, it discussed the gain of electrical efficiency and thermal efficiency on the system after adding two reflectors on each of the south and north sides, and adjusting the water circulation system. As the rising angle and position of the sun varies each season, in order to make this study more rigorous, experiments were conducted in four seasons of a year. The Taguchi orthogonal array was used for experimental planning, and the optimal parameters were analyzed for electrical efficiency and thermal efficiency. The analysis of variance was conducted to examine the influential parameters, and principal component analysis was used to calculate the principal component point of each experiment. The results were employed to construct a response surface methodology model. Finally, the steepest descent method was applied to obtain the optimal parameters. The reflector theory was applied to calculate the gain of solar radiation amount after installing the reflector. Moreover, the gain was inputted into the simulation software TRNSYS to simulate the electrical power output and the water temperature in the water storage tank. The confirmatory experiments of the four seasons found that the electrical energy after installing the reflector increased by 0.117-0.183 kWh, and the thermal energy increased by 1.7-2.6 • C. The experiment confirmed that the prediction error was <4 %.Keywords Photovoltaic/thermal (PV/T) · Reflector · Taguchi method · Analysis of variance (ANOVA) · Principal component analysis (PCA) · Response surface methodology (RSM) · Steepest descent method (SDM) · Transient system simulation tool (TRNSYS) List of symbolsP Total generated electrical energy during the day (kWh) G Total solar radiation energy during the day (J/m 2 ) A Module dimension (m 2 ) V m PV voltage at maximum power point (V) I m PV current at maximum power point (A) Q Total generated thermal energy during the day (J) V Water mass flow rate (kg/s) C p Water specific heat (4.18 kJ/kg • C) T f Water final temperature ( • C) T i Water initial temperature ( • C) A r1_a Actual receivable area of upper reflector (m 2 ) W 1 Upper plate width (m) W 1 Upper plate reflect to module width (m) L 1 Upper plate reflect to module height (m) L 1 Upper plate height (m) A r1 Reflection area of upper reflector (m 2 ) 123 J Intell Manuf θ Included angle between reflector and azimuth ( • C) A r2_a Actual receivable area of lower reflector (m 2 ) W 2 Lower plate width (m) W 2 Lower plate reflect to module width (m) L 2 Lower plate height (m) L 2 Lower plate reflect to module height (m) A r 2Reflection area of lower reflector (m 2 ) G r1_c Reflection solar radiation of upper plate (J/m 2 ) G r1Receiving solar radiation of upper reflector (J/m 2 ) L 1Upper plate reflect to module lengthen width (m) G r2_c Reflection solar radiation of lower plate (J/m 2 ) G r2Receiving solar radiation of lower reflector (J/m 2 )

This study attempted to optimize the manufacturing process of polyethylene terephthalate (PET) and titanium dioxide-containing (TiO 2 ) composite fibers. The composite fiber is made by the melt spinning processing method, and has the characteristics of the high strength of PET and the sterilization function of TiO 2 . To obtain the optimal processing parameters, this study applied the Taguchi method in planning the research experiment, and set one parameter of two levels and seven parameters of three levels using the L 18 orthogonal array. The flow equation was used to design a cooling air system for the manufacturing, and the results showed that using one parameter of two levels can give a stable air pressure to cool the fiber to obtain the characteristics of excellent quality. Finally, field emission scanning electron microscope (FE-SEM) was used to observe the distribution of TiO 2 particles in the PET fiber produced in the experiment, in order to verify the experimental effectiveness. This study used principal component analysis combined with the gray relational method to obtain the optimal parameters of the experiment, because the former has the advantage of data simplicity, while the latter can determine the factors influencing power ranking. Confirmation experiments were conducted to test the quality characteristics, and found that the properties of the fiber produced with the optimal parameters showed improvements.

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