Vol 54, No 4 (2018)

The paper presents the results of an experimental study of the efficiency of the integrated controllers of PWM and MPPT PV/batteries, which are part of an autonomous photovoltaic power plant. The dependences of the efficiency on the hourly sums of solar radiation are represented, which can be used to calculate the productivity of autonomous photovoltaic systems with an hourly integration step. The operational features of the controllers during low-level periods of solar radiation are considered.

The paper considers the influence of the insolation level on the electric power quality indicators and efficiency of a grid-tie inverter operating as part of a grid-connected photovoltaic power plant. Over the course of a year, data were recorded for Moscow on incoming solar radiation and the grid-tie inverter input and output capacity provided by a 1 kW grid-connected photovoltaic power plant. The insolation threshold values for a Solar River 1100 TL inverter are experimentally established, corresponding to both the beginning and end of stable inverter operation, as well as the required phase angle value for the electric energy supplied to the grid.

Studies are carried out on the morphology of the surface and photovoltaic characteristics of a thinfilm Au–Zn_xCd_1–xS–Mo structural injection photodetector with a wide photosensitivity range in the ultraviolet and visible radiation spectral regions. The composition of Zn_xCd_1–xS film in the Au–Zn_xCd_1–xS–Mo structure with a wide photosensitivity spectrum in the ultraviolet and visible spectrum, where x on the surface varies from 0.22 to 0.24, is studied. The mechanism of current transport is investigated, and the main electrophysical parameters of the semiconducting materials are determined. The use of Zn_xCd_1–xS film with a variable band gap in the thin-film heterojunction solar cells, where they are used as the buffer layer, will provide an opportunity to increase the photosensitivity of the structure in the short-wave region of the radiation spectrum, increase the value of the built-in potential, short-circuit current and value of the open-circuit voltage of the structure.

This paper deals with a AlGaAs/GaAs p-i-n quantum well solar cell. The doped region are based on AlGaAs semiconductor while the intrinsic region “I” contain multi quantum well (MQW) system AlGaAs/GaAs. A semi-analytical model in the intrinsic region and numerical drift-diffusion model in doped regions are combined to extract the total current density of the cell versus voltage. The current-voltage (J-V) characteristics are generated for the AM1.5 solar spectrum. The effect of the Aluminum molar fraction x (Al_xGa_1–xAs), the number, the width, the depth of the wells and barriers in the “i” layer and the doping densities on the electrical outputs of the solar cell are also presented. The optimized solar cell reached a conversion efficiency of 28.72% with a short circuit current density of 36.9 mA/cm² and an open circuit voltage of 0.97 V.

The annual supply of total solar irradiation (SI) to the surface of a randomly oriented photovoltaic panel (PVP) is considered; on this basis, the optimal horizontal tilt for seasonal or annual use is found. A flow diagram is proposed for determining the global total irradiation (GTI) on the surface of PVPs installed in variously oriented positions. Surkhandarya region is considered as an example. The actinometric findings obtained from the Sherabad station, as well as the PVP test results, are provided.

A one-dimensional nonstationary three-element distributed thermal model of a flat-plate collector with allowance for time variation of the temperatures through the “thickness” of the elements and along the length of the solar collector (SC) has been developed and software-implemented. The main data in this model consist of the thermophysical and overall parameters of the collector elements, heat carrier inlet velocity, solar radiation density, and ambient and sky temperature. To decrease the calculation variants, the variation ranges of mass flow of the heat carrier and its flow velocity were estimated for the characteristic parameters of the heat-removal channels of flat-plate SCs. It has been found that the specific mass flows of water in flat-plate SCs are 2.5–10 g/(s m²), and the water flow velocity is 0.0005–0.002 m/s. It is shown that the instantaneous efficiency coefficient and temperature of the heat carrier can fall outside stationary values within 1–3 h. However, the daily efficiency coefficients of the SC do not fall outside the stationary values even within a day. The developed flat-plate SC model can be used to estimate the influence of the thermophysical and overall parameters of the elements, as well as the parameters of the environment, on its thermophysical characteristics when developing flat-plate SCs and methods for experimentally determining their characteristics.

The module of parabolic-cylindrical composite mirror concentrating system (MCS) is created with an optimal aperture angle (U) and relevant optimal size of the focal spot provided by flat mirror elements with the optimal size.

The main ways of improving the performance efficiency of solar energy (SE) use in hot water supply systems (HWSSs) are discussed. It is established that the environmental characteristics of flat-plate solar water heating collectors (FPSWHCs) for heating water in HWSSs depend on the water heating temperature in these systems.