• Energy Research

Abstract The annual variation of global (total) solar radiation measured over four (4) years (1995–1998) at Ilorin (8°32′N, 4°34′E) was studied and the bio-effects of the variation is herein reported. The weekly averages of the solar radiation flux were obtained and plotted. The profile of the weekly averages of the insolation shows two notable “wells” corresponding to the harmattan dry season and the rainy season. It was deduced that the duration of the seasons was directly proportional to the sizes of the “wells”, while the depths of the “wells” correspond to the severity of the causes of the “wells”. The fall and rise rates of the depth of the edges of the wells are inversely proportional to the ecological effects of the variation of the radiation. The rates of decrease and increase of the radiation flux affect the depths of the “wells” and were found to be rapid and shallow for the “Harmattan Well”, and gentle and deep for the “Rain Well”. The width (duration), rate of change and depth of the “Harmattan Well” bring about stress for both animals and plants.

Abstract The annual variation of global (total) solar radiation measured over four (4) years (1995–1998) at Ilorin (8°32′N, 4°34′E) was studied and the bio-effects of the variation is herein reported. The weekly averages of the solar radiation flux were obtained and plotted. The profile of the weekly averages of the insolation shows two notable “wells” corresponding to the harmattan dry season and the rainy season. It was deduced that the duration of the seasons was directly proportional to the sizes of the “wells”, while the depths of the “wells” correspond to the severity of the causes of the “wells”. The fall and rise rates of the depth of the edges of the wells are inversely proportional to the ecological effects of the variation of the radiation. The rates of decrease and increase of the radiation flux affect the depths of the “wells” and were found to be rapid and shallow for the “Harmattan Well”, and gentle and deep for the “Rain Well”. The width (duration), rate of change and depth of the “Harmattan Well” bring about stress for both animals and plants.

The relatively low energy conversion efficiency of dye-sensitized solar cells (DSSCs) is a key challenge hindering the commercialization of the solar cell. The photochemical performance of the dye used as a photosensitizer for the DSSC greatly determines the efficiency of the solar cell. This study demonstrates the suitability of dye extracted from rosella (Hibiscus sabdariffa L.) flowers as a photosensitizer for a DSSC. The natural dye was extracted using the acid water extraction method and was characterized using FTIR spectroscopy and UV–vis spectrophotometry. The absorption spectra of the dye were examined to determine the aptness of the dye as a photosensitizer in DSSCs. The IR absorption spectra of the extracted dye confirmed both amine and hydroxyl compounds as functional groups in the natural dye, which established the suitability of the dye as a photosensitizer in DSSCs.The UV-vis absorption spectra of the natural dye within the visible region illustrate that the aqueous extract from rosella flowers has stable absorption of visible light, thus validating the natural dye as a good candidate for photosensitizer in a DSSC. The fabricated DSSC delivered a short-circuit current of 5 ?A and an open-circuit voltage of 0.637 V.

The relatively low energy conversion efficiency of dye-sensitized solar cells (DSSCs) is a key challenge hindering the commercialization of the solar cell. The photochemical performance of the dye used as a photosensitizer for the DSSC greatly determines the efficiency of the solar cell. This study demonstrates the suitability of dye extracted from rosella (Hibiscus sabdariffa L.) flowers as a photosensitizer for a DSSC. The natural dye was extracted using the acid water extraction method and was characterized using FTIR spectroscopy and UV–vis spectrophotometry. The absorption spectra of the dye were examined to determine the aptness of the dye as a photosensitizer in DSSCs. The IR absorption spectra of the extracted dye confirmed both amine and hydroxyl compounds as functional groups in the natural dye, which established the suitability of the dye as a photosensitizer in DSSCs.The UV-vis absorption spectra of the natural dye within the visible region illustrate that the aqueous extract from rosella flowers has stable absorption of visible light, thus validating the natural dye as a good candidate for photosensitizer in a DSSC. The fabricated DSSC delivered a short-circuit current of 5 ?A and an open-circuit voltage of 0.637 V.

Abstract This study investigates the impact of the seasonal Harmattan aerosol loading on PV module efficiency at a station in Southwest Nigeria. To this end, a simple, open-source, cost effective electronic load I-V curve tracer was developed to compare the I-V characteristics of a pair of horizontally positioned 80 W monocrystalline modules for the duration of the Harmattan period. The control module was regularly cleaned manually and the other module left to accumulate the Harmattan dust deposits. In order to obtain the modules’ characteristic parameters, an Arduino-based pulse width modulation (pwm) duty cycle was implemented to vary simultaneously, the gate-source voltages, VGS, of two power metal-oxide semiconductor field-effect transistors (MOSFETs) acting as fast variable loads for the modules. Experimental results acquired from the prototype circuit demonstrate that this method provides a more accurate approach and faster response than the resistive load tracer method. The prototype instrument was able to measure and reproduce characteristic curves that are obtainable from the more expensive branded products. Resulting curves depict reduction in the short circuit current, ISC, the current at maximum power, IMP, the power output, PMP and the efficiency, η of the dusty module by more than 18% in comparison with the control module over the measurement period.

Abstract This study investigates the impact of the seasonal Harmattan aerosol loading on PV module efficiency at a station in Southwest Nigeria. To this end, a simple, open-source, cost effective electronic load I-V curve tracer was developed to compare the I-V characteristics of a pair of horizontally positioned 80 W monocrystalline modules for the duration of the Harmattan period. The control module was regularly cleaned manually and the other module left to accumulate the Harmattan dust deposits. In order to obtain the modules’ characteristic parameters, an Arduino-based pulse width modulation (pwm) duty cycle was implemented to vary simultaneously, the gate-source voltages, VGS, of two power metal-oxide semiconductor field-effect transistors (MOSFETs) acting as fast variable loads for the modules. Experimental results acquired from the prototype circuit demonstrate that this method provides a more accurate approach and faster response than the resistive load tracer method. The prototype instrument was able to measure and reproduce characteristic curves that are obtainable from the more expensive branded products. Resulting curves depict reduction in the short circuit current, ISC, the current at maximum power, IMP, the power output, PMP and the efficiency, η of the dusty module by more than 18% in comparison with the control module over the measurement period.