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Estimates of the efficiency of solar installations in the Sun tracking mode presented in the literature are often ambiguous due to nonidentical comparison criteria and irradiation conditions. It is pro-posed to evaluate this characteristic systematically by two indicators - orientation and energy. The first is numerically equal to the current value of the cosine of the illumination angle of the receiving surface. And the second - the daily exposure of the tracking surface, attributed to the maximum value with ideal tracking of the Sun by a biaxial rotary device. Both indicators are calculated under the assumption of irradiation with three streams of solar energy in clear skies, which change during the day according to the model of the European Solar Radiation Atlas (ESRA). posed to evaluate this characteristic systematically by two indicators - orientation and energy. The first is numerically equal to the current value of the cosine of the illumination angle of the receiving surface. And the second - the daily exposure of the tracking surface, attributed to the maximum value with ideal tracking of the Sun by a biaxial rotary device. Both indicators are calculated under the assumption of irradiation with three streams of solar energy in clear skies, which change during the day according to the model of the European Solar Radiation Atlas (ESRA). The relationships between the fluxes of solar radiation at different atmospheric states are taken into account by the Linke turbidity factor. The unit of comparison of the efficiency of uniaxial tracking is the daily exposure of the surface the biax ial tracking device, the angle of illumination of which during the day is zero. Four variants of estimation of efficiency concerning direct and full streams of solar radiation at two variants of distribution of brightness of the sky - isotropic and non-isotropic in the Hay-Davies model approximation are considered. The simulation results are presented in tabular and graphical forms. [ABSTRACT FROM AUTHOR]

The relevance of this study is conditioned upon the need to establish the possibility of using artificial lighting to increase the productivity of cows with tethered maintenance. This paper is aimed at identifying the effect of adjustable lighting of the feed table with LED lamps on the dairy productivity of cows. The cowshed lighting was provided by the SmartAC (LRC) automatic control system. The research method was to analyse the dynamics of cow milk yield under controlled photoperiod conditions and the level of illumination of the room. Two groups of cows were formed: experimental cows were kept in an experimental cowshed with natural illumination of the feed table of 101±20.2 lx and artificial illumination of 202±19.9 lx, the control group was kept in a typical 2-row room for 100 heads, in which natural illumination feed table was 139±22.8 lx, artificial – 26±3.2 lx. The duration of the photoperiod was 16 hours, and the ratio between natural and artificial lighting depended on the astronomical length of the day. Milk productivity of cows was assessed according to the method of control milking. Milk yields were recorded one month before the installation of the experimental lighting system (in February) and for the next four months (from March to June). Before the installation of the experimental lighting system, the difference in milk yield of cows was not statistically significant. In the future, despite fluctuations in the amount of milk yield caused by feeding, the experimental group of cows exceeded the control group in terms of milk productivity. The advantage of the cows of the experimental group in terms of daily milk yield was from 2.3 kg in March to 5.8 kg (p<0.01) in May. During the period of maximum daylight hours (June), the effect of artificial lighting on the dairy productivity of cows was insignificant. It was noted that the increase in the preference of experimental cows for milk yield occurs over several months, and the positive impact of improved lighting of the feed bunk increases along with an increase in milk productivity on the farm. That is, the higher the feeding level, the greater the effect of lighting control. The obtained results were confirmed after the analysis of the productivity of analogue cows by age and lactation phase, selected from the experimental and control groups. The results of the study are of practical value for the improvement of lighting in cowsheds with tethered housing. [ABSTRACT FROM AUTHOR]

A comprehensive study on impact of active layer band gap and light illumination on the device performance has been analyzed for the FTO/TiO2/Cs2TiX6/CuSCN/Ag based Perovskite Solar Cell (PSC) using the Solar Cell Capacitance Simulator – 1 Dimension (SCAPS-1D) simulator. The present design strategy of the device for optimizing the short circuit current (JSC, mA/cm²), power conversion efficiency (PCE, %) through the absorbing layer band gap variation, and light illumination spectrum has been studied at the optimal thickness, device temperature, and defect density. The value of the different parameters used in the device simulation has been taken from the previous work. From this study, it was revealed that Cs2TiBr6, and Cs2TiF6 absorbing layer based PSC device has recorded maximum PCE at the 1.80 eV band gap, whereas, for the Cs2TiI6, Cs2TiCl6 absorbing layer based PSC device has achieved maximum PCE at the 1.60 eV band gap. On the other side, optimum PCE can be achieved at 400 nm wavelength on the light illumination for the Cs2TiBr6, Cs2TiCl6, and Cs2TiF6 absorbing layer based PSC. The Cs2TiCl6 absorbing layer based PSC device has recorded maximum PCE at 450 nm wavelength on the different light illumination. [ABSTRACT FROM AUTHOR]

Improving the efficiency of converting solar radiation energy into electricity by solar cells is the main task of solar energy. And the modern interest in the design and operation of photovoltaic batteries based on solar cells leads to the evaluation of their main performance characteristics. To control the quality and efficiency of a solar cell in production or in the laboratory, it is necessary to accurately measure its volt-ampere characteristic, which is the main source of information about the parameters and characteristics of the solar cell, such as efficiency, maximum power, short circuit current, no-load voltage, current and voltage at maximum power, form factor, etc. When designing photovoltaic batteries of large areas, ground or space applications, there are difficulties in determining the various losses, such as switching of photocells, their non-identity, uneven temperature and illumination of photovoltaic batteries. Usually these losses are taken into account by introducing various coefficients into the mathematical model. Experimental studies in the direction of more accurate determination of all kinds of losses in photovoltaic batteries lead to non-payback and complicate the conduct of such experimental studies. For the design and testing of large-area photovoltaic batteries, the authors propose an approach that is based on the construction of volt-ampere characteristics of photovoltaic batteries. The proposed approach allows to determine the free-ampere characteristics of an individual solar cell or groups of photovoltaic converters, to obtain models at different levels of illumination and temperature with the characteristic parameters of photovoltaic batteries of any area. The authors conducted an experimental confirmation of the proposed method, as well as a comparison with other experimental studies. The method identifies the transition coefficients of the mathematical model, as well as the features of the proposed approach. Bibl. 6, Fig. 2. [ABSTRACT FROM AUTHOR]

The problem of natural forests conservation is relevant in the Ukrainian steppe zone where the forest ecosystems develop in the unfavorable conditions of geographic mismatch; therefore, they suffer as a result of any environmental changes. The hypothesis of susceptibility of tree leaves’ metabolism even to slight changes of climatic parameters was tested. The study was conducted in more than 75 years-old natural mixed forest located on the right bank of the Samara river. The chlorophyll (Chl) content, and catalase (CAT), benzidine-peroxidase (BPOD) and guaiacol-peroxidase (GPOD) activities in leaves of autochthonous maple species (Acer platanoides L.) and adventive acacia species (Robinia pseudoacacia L.) were investigated on the lower (52 m above see level, a.s.l.), middle (74 m a.s.l.) and upper (96 m a.s.l.) coastal slope altitude. In maple leaves decreasing chlorophyll amount on the middle and upper plots (8.8% and 19.5% compared with the lower plot) together with Chla/Chlb ratio decrease (from 4.7 on the lower to 4.4 on the middle and 4.0 on the upper plots) was found. Chlorophyll content in acacia leaves decreased only on the upper plot (by 8.5% compared to the lower one), and Chla/Chlb ratio on the lower and upper plots reached 5.1. In maple leaves the increase in altitude was accompanied by the decrease in BPOD activity (by 26% and 63% on the middle and upper plots, accordingly), and GPOD and CAT (accordingly, by 31% and 37% on the upper plots compared to the lower plots). High correlation coefficients of light, temperature and humidity with activity of CAT (respectively, r = –0.98; r = –0.85; r = 0.83), BPOD (r = –0.96; r = –0.93; r = 0.90) and GPOD (r = –0.98; r = –0.82; r = 0.82) were estimated in A. platanoides leaves. Sharp decline in GPOD activity in R. pseudoacacia leaves was revealed on the upper plot (by 95% compared to the lower one), whereas BPOD activity increased by 47% on the middle plot but decreased by 74% on the upper one compared to the lower plot, and CAT activity on the middle and upper plots exceeded 4.3-fold and 1.8-fold the activity on the lower plot. In R. pseudoacacia leaves high correlation of light, temperature and humidity was found with GPOD activity (respectively, r = –0.99; r = –0.82; r = 0.82), whereas correlation with the light level was significant only for BPOD (r = –0.84), and no significant correlation was recorded for CAT activity. Results of the study confirm high sensibility of photosynthetic and antioxidant processes in leaves of both tree species to microclimate changes, which is defined as a conventional enhancement of aridity traits when moving upwards on the slope. It is suggested that the level of correlation between enzyme activity and microclimate and lighting parameters can serve as a marker of tree species adaptation to the slope altitude-associated changes of the local environmental factors in the natural forest.