Feasibility of Solar Tracking System for PV Panel in Sunbelt Region

In the study of the feasibility of solar tracking systems for crystalline silicon photovoltaic(PV)panels in hot and cold regions,it is argued recently that a tracking system is not necessary for sunbelt countries owing to the overheating that results from excessive exposure to solar irradiance.This conclusion has been formulated based on a mathematical model,which in turn is based on the assumption that the PV module temperature can be calculated using an empirical relation of this temperature to ambient temperature,available solar irradiance,and nominal operation cell temperature(NOCT).To support this conclusion,it is claimed that the mathematical model is validated experimentally.However,this assumption is vague and widely used in the literature.The objective of the present work is to reevaluate the above-mentioned assumption and to discuss the results deriving from it.It is shown experimentally in the present work that the above-mentioned assumption overestimates the PV module temperature.At a solar irradiance of 900 W/m2,ambient temperature of 25℃,and wind speed of 5 m/s,the measured PV module temperature is lower than the value calculated based on the mentioned assumption by 29.26%.

Fabrication and photoluminescence characteristics of novel red-emitting Ba_(2)LuNbO_(6):Eu^(3+)double-perovskite phosphors on near UV WLEDs

Red emitting phosphors play a significant role in accelerating the improvement of illumination quality for white light emitting diodes(WLEDs).In this work,by using solid-state reaction method,an efficient novel Ba_(2)LuNbO_(6):Eu^(3+)phosphor with double-perovskite structure was successfully prepared.Here,a series of Ba_(2)LuNbO_(6):Eu^(3+)red phosphors can be efficiently pumped by the near-ultraviolet(UV)light and then present high-brightness at orange emission(598 nm,~5D_(0)→~7 F_(1))and red emission(610 nm,~5D_(0)→~7 F_(2)).The ratio values of 610 to 598 nm in Ba_(2)LuNbO_(6):Eu^(3+)phosphors exceed 1 when the content of Eu^(3+)is larger than 0.4 mol,because the occupation of Eu^(3+)ions is changed from Lu^(3+)ions with symmetric sites to Ba^(2+)ions with asymmetric sites.Besides,the optimized concentration of Eu^(3+)at the~5D_(0)→~7 F_(2)transitions is obtained when x=1,indicating that there is non-concentration quenching in Ba_(2)LuNbO_(6):Eu^(3+)phosphors.Moreover,the CIE chromaticity coordinates of Ba_(2)LuNbO_(6):Eu^(3+)was calculated to be(0.587,0.361),the color purity was calculated to be 72.26%and internal quenching efficiency(IQE)was measured to be 67%.Finally,the thermal stability of Ba_(2)LuNbO_(6):Eu^(3+)phosphors was also studied.Our work demonstrates that the novel double-perovskite red-emitting Ba_(2)LuNbO_(6):Eu^(3+)phosphors are prospective red emitting elements for WLEDs applications.