AbstractThe possibility of using a graded-gap crystal as a protective coating of organic solar cells from harmful chemical and other external influences has been studied. On the basis of a quantum model for an electronic near-surface state with an Airy potential well, an expression is obtained that is radically different from the Tamm level, with the help of which the condition of light transparency of the graded-gap region is formulated, but with the implementation of protective properties due to a reduced band gap. It is assumed that the developed method is valid for both classical semiconductors and ionic materials. It was shown that graded-gap coatings have no electronic levels at a certain thickness and, therefore, do not absorb solar radiation; they are completely transparent and can also be used as encapsulating coatings for organic solar cells. Antireflection coatings based on MgF2–CaF2 composite materials are considered as an example of a graded-gap coating. Composite material MgF2–CaF2 is a homogeneous material with an ionic bond, so the coating based on it has graded-gap properties. Such coatings are antireflective and promising for encapsulation of organic solar cells. The increase in the transmission of a glass substrate with applied antireflection coatings is 1.68–2.27%, depending on the composition of the coating. After storage under normal conditions for 3 years (2018–2020) and climatic tests for 1 year (2021), the coatings retained their spectral–optical properties. The experiment showed that graded-gap coatings on organic solar cells are antireflective and protective from external influences.

AbstractA technology has been developed for manufacturing solar cells based on silicon doped with impurity atoms of rare-earth elements holmium and gadolinium. It has been established that at a concentration of doping with holmium and gadolinium of 1017 cm–3, the efficiency of solar cells increases on average by 15% relative to the control ones. An increase in the radiation resistance of solar cells based on silicon doped with rare earth elements holmium and gadolinium during irradiation with gamma quanta is shown. Rare-earth elements holmium and gadolinium, introduced into silicon during growth, are present in it in the form of various impurity precipitations and complexes, being electrically inactive, actively interacting with vacancies and residual impurities, reduce the concentration of optically active oxygen and carbon, increasing the thermal and radiation stability of the parameters of the original silicon.

AbstractThe performance, thermal parameters and drying kinetics of muskmelon are calculated in an indirect natural convection solar dryer (INCSD) and indirect forced convection solar dryer (IFCSD). The initial moisture content (MC) of muskmelon slices was 12.4156 kg/kg of db (db) and it declined to 0.1605 db in 15, 18 and 22 h in IFCSD, INCSD and open sun drying (OSD), respectively. The estimated collector and drying efficiencies (ηcl and ηdr) were 58.5 and 9.39% in INCSD and the same were 66.37 and 12.11% in IFCSD, respectively. The specific moisture extraction rate (SMER) was 0.544 and 0.6204 kg/kWh in INCSD and IFCSD, respectively. The Verma model was relevant to fit the drying characteristics of muskmelon in INCSD, IFCSD and OSD. The thermal parameters such as effective moisture diffusivity (Defm), surface transfer coefficients (hht and hmt) and activation energy (Eac) were also determined for both setups. The average increment of 13.45% on ηcl, 28.97% on ηdr, 14.04% on SMER, 24.08% on Defm, 55.36% on hht, 55.16% on hmt, and 24.83% on Eac were observed in IFCSD than INCSD. The Eac of muskmelon slices was 38.06 and 28.61 kJ/mol in INCSD and IFCSD, respectively. Uncertainty analysis was performed and error bars were included in all the plots.

AbstractThis work studies the influence of a mixed solar dryer with forced convection on the quality of cocoa beans. Data collection have been carried out during 6 days on a 10 kg sample. The dryer is based on a combination of direct and indirect models with forced convection for each. Its frame and its insulating part are made of wood and polystyrene respectively. The inner surface is covered with a thin layer of aluminum foil. A control and measuring device for air flow, temperature and humidity has been placed in the drying room. The direct solar part of the dryer allows the drying process to be accelerated, especially during the first drying phase. The proposed prototype dehydrated cocoa beans in two days with a moisture content that decreased from 53.4 to 4.6% for the beginning and the end of the drying process respectively, which validates the ISO 2451 standard. The drying process was conducted in an environment where the drying temperature and relative humidity were varying between 18 to 55°C and 28 to 80% respectively. Placing the same quantity of beans in the acceleration room, drying room and in the open air, for a quantity of water to be removed of about 5.07 kg of water, the water removal rates are about 0.32, 0.21 and 0.10 kg/h respectively for an effective daily average of 8 h. The drying efficiencies of the acceleration room and the drying room are 68 and 52% respectively, higher than those of the open air drying.

AbstractThis article discusses the issue of choosing the location and capacity of a photovoltaic (PV) plant in a rational way for the power supply of the designed capacity of the planned devices and equipment (office equipment, night/day lighting, and alarm systems) as part of the newly constructed building of the JSCB Uzpromstroybank branch in Nukus, the Republic of Karakalpakstan. Based on the climatic and actinometrical database for the city of Nukus (for the period 2005–2020), the natural and technical potential of renewable energy sources (solar energy) of the region is determined. The average hourly power consumption of the planned part of the facility is determined on the basis of the technical parameters of the installed electrical switchboard for power supply on working days is 48.3 kWh, connection to the network of part of the facility was provided through an 80 kVA battery. According to preliminary calculations, to compensate for this energy consumption, the possibility of installing a PV plant based on a 60.3 kW grid system, using the roof section of the building to the maximum. Six different scenarios of system operation using PV*SOL and PVsyst software products have also been developed, where one of the main criteria for choosing a rational solution is the replacement coefficient of traditional energy resources of at least 30%. From the considered scenarios, the most rational options for improving the reliability and stability of the power supply system of the selected part of the facility are determined, as well as rational indicators of the orientation and angle of inclination of PV panels to the horizon, the payback period, the required number of panels, the maximum reduction of CO2 emissions, and on the basis of these scenarios, the technical, economic, and environmental efficiency of the system are determined.

Abstract—The paper analyzes the potential use of porous ceramic materials as absorbers for hydrogen storage in the gaseous state and shows the prospect for the use of a steel reactor container filled with porous ceramic absorbers as an efficient hydrogen accumulator.

AbstractMainly for off-grid operation, two versions of maximum power point tracking controllers based on a bidirectional DC voltage matching converter have been developed, manufactured, and tested. The main difference between the developed circuits is the ability to power controllers, extreme power regulators of solar panels, both from accumulators and from the solar battery itself, which opens up wide possibilities for their application in niches associated with the production of products such as heat, cold, hydrogen, purified, or lifted water from a well, when electrical energy is not the final product and its accumulation is not required. In this case electrical energy is not an end product and its storage is not required and the battery rejection reduces the cost and simplifies the entire scheme for such plants. Plant lifetime can also be significantly widened. One of the proposed schemes also makes controller applications possible for multicomponent hybrid plants control, directing excess energy to production of useful byproducts. Experimental samples of controllers with a power output of 800–1000 W have been produced. Their full-scale comparative tests were carried out in parallel with foreign commercial battery controllers in the climatic condition of Moscow revealing an efficiency at the level of 93–96%, close to commercial analogs.

AbstractThe present research proposes a comprehensive model to estimate the optimum annual fixed mode tilt angle (\({{{{\beta }}}_{{{\text{opt}}}}}\)) as a function of all parameters that affect the intensity of solar irradiance incident on a tilted plane such as: latitude (\(\varnothing )\), diffuse fraction (\({{{{H}_{{\text{d}}}}} \mathord{\left/ {\vphantom {{{{H}_{{\text{d}}}}} {{{H}_{{\text{g}}}}}}} \right. \kern-0em} {{{H}_{{\text{g}}}}}}\)) and albedo (\({{\rho }_{{\text{g}}}}\)) by using the weighting functions. It is a useful tool in obtaining a weighted fit when estimating the unknown parameters in a model. The horizontal components of solar irradiation are obtained via SODA database platform based on a reliable-validated hourly time series satellite-derived data for 19 sites on the Middle East and North Africa region. The Klucher anisotropic sky-diffuse transposition model is adopted in order to estimate the global tilted solar irradiance, as it recommended for many sites in MENA region. A polynomial regression model, is proposed to estimate \({{\beta }_{{{\text{opt}}}}}\) as the product of all the above weighting functions and the latitude as \({{\beta }_{{{\text{opt}}}}} = \varnothing W\left( \varnothing \right)W\left( {\frac{{{{H}_{{\text{d}}}}}}{{{{H}_{{\text{g}}}}}},{{\rho }_{{\text{g}}}}} \right)\). The proposed model was validated using several statistical indicators and compared with other results obtained by other researchers for different sky and albedo conditions. The results proved the applicability and reliability of the proposed model, as the R-square index showed that 89% of the considered sites were greater than 0.98, and the MBE index showed that 84% of the locations were less than one. The difference between the results obtained by the propose model and the calculated ones was less than 2% error for all sites except for Sana’a (6%). Moreover, they showed the high potential of the proposed model for use in engineering design, eco-energetic analysis and optimum design processes.

AbstractThe present study concentrates on the exploration of solar irradiance in the Thar desert at eight selected locations, including Bhadla and Dhirubhai Ambani solar parks. For this, we first perform daily, weekly, and monthly solar irradiance prediction using five time-series models, namely AR, MA, ARMA, ARIMA, and seasonal ARIMA (SARIMA). The dataset of necessity includes hourly solar irradiance values of 21 yr (2001–2021) from NASA’s power project. As these time series models turn out to be inadequate to capture seasonality across temporal resolution, we additionally implement the window sliding ARIMA (WSARIMA) and LSTM to incorporate possible nonlinearity and seasonality in the dataset. Based on the three standard indicators, namely RMSE, MAPE, and MAE, we observe that LSTM outperforms other models at daily and weekly time resolution, whereas ARMA turns out to be the best on monthly dataset. The emanated results suggest that all locations reveal a high potential for harnessing solar power. The present analysis, therefore, enables solar irradiance exploration in the Thar desert through different time series models.

AbstractThe major challenges in solar photovoltaic (PV) penetration into the grid are maintaining quantity and quality of power at transmission and distribution network because of variable solar insolation levels, harmonics due to solar inverters, sudden increase or decrease in load on distribution network, etc. In the Indian context, solar energy penetration into the grid is still limited to rooftop and small-scale generation feeding power into the distribution grid typically at 440 V or 11 kV. The only energy penetration at the transmission level of 220 kV is developed and installed by Power grid corporation of India in Hyderabad, India. Thus, the integration of solar photovoltaic systems in terms of power quantity and quality at the transmission and distribution level is still a major challenge in the Indian subcontinent which has brought ample opportunities for power quality engineers and researchers to comprehensively deal with issues related to quantity and quality of power supplied by solar PV technologies into the grid. The paper attempts to review existing status of Solar PV grid-connected applications from a qualitative and quantitative perspective and also comment upon its prospects with an emphasis on solar energy potential, installations done so far and expected quality of power in the grid- tied solar PV systems.

Abstract—Changeability of the energy input from renewable sources, as well as climate change, accelerating by the day, dictate the need to study the latest climate changes in the country in order to examine the possibilities of using electricity generating installations and systems based on renewable energy sources, as well as for agro–climatic purposes in this territory. The first part of the research presents the results of studying the dynamics of changes in weather and climatic conditions in the territory of the Republic of Uzbekistan, the Fergana Valley in particular, during the period of 2005–2021 by means of collecting and processing climatic data obtained from nine weather stations located in the valley and suitable for scientific research purposes. It was revealed that during the period of 2005–2021, the maximum change in the average annual temperature in the areas of Fergana oblast was 1.58°C and the number of days with an average ambient temperature above +25°C varied between 100 and 121 days; direct beam solar radiation increased significantly; there was also a sharp drop in wind speed and the number of days with dust storm and drifting dust; and the amount of precipitation in the region in recent years was significantly less than in 2005. Due to the fact that the level of warming in the valley affects the generation capacity of crystalline silicon photovoltaic modules (PVMs), in order to predict their production capacities with the least error, it is necessary to prepare the most accurate source data on climatic and actinometrical parameters for their performance evaluation and survey works in the applicable part of the region.

AbstractIn this article it were analyzing the hydrodynamic processes occurring in the working chamber of the solar air heater collector with a submersible air pipe absorber, developed in a new type designed to obtain thermal energy from solar energy, including the mode of movement of air, the formation of boundary layers of air flow in pipes, heating surface structures, methods for calculating basic physical. Also, the issues of air flow boundary layers formation, boundary layers discontinuity detection, and air movement formation that occur under laminar or turbulent flow conditions are revealed as a result of changes in air flow movement patterns. Based on the results obtained directly in the Reynolds number (Re) 1000–5000 range of these thermal and hydrodynamic processes, a mathematical and immersion model was developed. In the research work, the concave dimensions of the air pipe including the relationship between the length of the concave step t and the height of the concave h were determined in general, taking into account the formation of air flow movements and the break points of the boundary layers when choosing the most optimal indicators of t/h.

AbstractToday, the ever-growing demand for renewable energy resources urgently needs to develop reliable electrochemical energy storage systems. The rechargeable batteries have attracted huge attention as an essential part of energy storage systems and thus further research in this field is extremely important. Although traditional lithium-ion batteries (LIBs) have a wide range of applications, they still face a number of challenges associated with the high cost, safety, transportation, aging effect and sensitivity to temperature. To meet these demands, it is essential to pave the path toward post lithium-ion batteries. Aluminum-ion batteries (AIBs), which are considered as potential candidates for the next generation batteries, have gained much attention due to their low cost, safety, low dendrite formation, and long cycle life. In addition to being the third most abundant element in the Earth’s crust, aluminum is also cheap and has a high volumetric capacity of 8046 mAh cm–3. This review discusses the development of high-performance electrode materials for AIBs. Additionally, an overview of some challenges related to the utilization of electrode and electrolyte materials in AIBs has been provided.

AbstractLow temperature drying or withering is the first step in tea processing after the tea leaves are harvested. The process of tea withering was conducted in a newly developed laboratory scaled withering trough coupled with a corrugated solar air heater during the months October and November 2019. The maximum withering air temperature was 32°C. The average relative humidity of the withering air was 80%. After 7 h of withering at an air temperature 27°C, the tea leaves attained around 60% moisture content. The average thermal efficiencies of the corrugated solar air heater for October and November 2019 were 63.15 and 56.06% at average solar radiations of 891 and 772 W/m2 respectively. The overall efficiency of the withering trough was estimated as 40.98% with a specific energy consumption of 1.76 kWh/kg. Among the seven drying models used for fitting the withering characteristics, the Two-term model gave the best fit with R2 value of 0.9977 at 32°C. The activation energy was 104.05 kJ/mol.

AbstractA lot of papers are dedicated to the analysis of the optimal tilt angles of radiation receiving surfaces of solar installations. But typically, high-latitude Arctic zones are not considered. In addition, the output dependence on the receiving surface tilt in the vicinity of output maximum routinely is weak. On the example of the territory of the Russian Federation, characterized by a large range of latitudes, the calculation of optimal tilt angles of photovoltaic panels and differences from the maximum output in case of deviations from these angles is performed. It is shown that the zone of a 3% decrease in output from the maximum is about 15°. The analysis of methods for optimal angle calculations showed that within this zone the near-optimal tilt angle can be determined by most known formulas, including retrieved expression or as an angle that is 12° less than the latitude. Complex formulas, in particular cubic approximations, in high latitudes can give underestimated values of the optimal angle.

AbstractThis article describes the features of the operation of an autonomous trench-type gabled solar greenhouse functioning on the basis of alternative energy sources. The positive aspects of the use of an autonomous solar greenhouse with a small area of more than 100 m2 in small-scale farms are presented. The method of long-term high-quality storage of a lemon harvest grown in the designed solar greenhouse is described for the mountainous conditions of the Kashkadarya oblast. Calculations are given to determine the technical and economic efficiency of using an autonomous trench-type solar greenhouse for small-scale farms. Marketing of citrus fruits was carried out in the domestic market of Uzbekistan, on the basis of which it can be said that in the 6th year of operation, when selling lemons in summer, the net profit will be about ~70 million soms. This profit was obtained when selling 1750 kg of lemons stored according to the proposed method from mid-November to July.

AbstractTo make the solar air heater model more competitive in the commercial space heating and dryer market, it necessitates the need for improvement in its thermal efficiency. This paper evaluates the possibility of enhancing the thermo-hydraulic efficiency of a solar energy-based air heater by modifying the geometry into an artificial roughed parabolic rib-shaped collector. The thermal performance of a modified geometry was analyzed using a 3D CFD model using thermal simulation software, SolidWorks Flow Simulation. The parabolic roughness profile parameters (roughness height (e) and pitch (P) are optimized by providing simulation runs for various values of e = 0.5 mm, e = 1 mm, e = 1.5 mm, e = 2 mm and pitch P = 15 mm and P = 20 mm. Performance optimization of the solar air heater is achieved at e = 1 mm and P = 15 mm at Reynolds number 3900. An experimental investigation of the proposed CFD model was also done to compare the actual results with the CFD results. Various experimental investigations done by relating heat transfer and friction factor have been reported for the comparative study of the thermal performance of various solar air heater ducts. At roughness height e = 1 mm, the optimum rib performance is observed. The experiment results are in line with the simulation results, with a minor deviation of 6.35%.

AbstractThe study is devoted to the development of a model for the analysis of current–voltage characteristics (CVCs) of perovskite based solar cells. Using the high-level programming language Python, programs have been developed for the theoretical calculation of the CVCs of perovskite based solar cells using the one- and two-diode models. The calculation results are compared with the experimental data on the CVCs of a perovskite solar cell consisting of an electron-conducting layer (n-type) SnO2 and SNO2–KCl. It has been established that the mathematical two-diode model most adequately reproduces the CVCs of perovskite based solar cells, especially under conditions of lower illumination. The developed program can be used to calculate and predict the CVCs for more efficient control of the output parameters of perovskite based solar cells.

AbstractPhotovoltaic (PV) modules may not experience uniform solar irradiation due to partial shading caused by the shadows of trees, passing clouds, or nearby buildings, resulting in a loss of energy. A robust real-time monitoring system and fault detection technique are highly critical to increasing the reliability of the PV system. This research focuses on developing real-time fault and partial shading detection techniques using Mamdani fuzzy logic for PV systems. The method has a minimal level of complexity and a high rate of fault identification. Multiple shading scenarios and open circuit fault were analyzed. Several rules have been developed in Mamdani fuzzy logic, which distinguishes between different cases. All case studies were verified through simulations and validated by establishing an experimental setup. From the simulation and experimental results, it has been demonstrated that the proposed technique has an excellent performance in detecting partial shading and fault.

AbstractWe have obtained ITO films on glass substrates by an advanced CVD method in a quasi-closed volume at normal atmospheric pressure without the participation of a carrier gas. To elucidate the dependence of the properties of ITO films on the substrate temperature and the SnO2/In2O3 ratio, the growth was carried out in the temperature range of 170–500°С by thermal decomposition of vapors of alcohol solutions of indium chloride and tin chloride, taken in various ratios. The modes were set by controlling the temperatures of the substrate and evaporator, to which aqueous or alcoholic solutions of indium and tin chlorides are supplied, as well as the ratio of the solution components and the solution supply rate. In this case, the film growth rate was about 0.5–1.0 μm/h, which is several times higher than in the case of spray pyrolysis under similar conditions. The thicknesses of the ITO films were determined using an MII-4 interference microscope, as well as from the transmission spectrum; the results showed that the films have a thickness of ~3 μm. The dependence of the resistivity of ITO films on the substrate temperature is presented, and it is shown that the resistivity of films obtained at substrate temperatures of 240–260°C has a sufficiently low resistivity acceptable for use in solar cells. The X-ray diffraction spectrum of ITO films was identified in comparison with the map 00-006-0416 (In2O3, cubic) from the Joint Committee on Powder Diffraction Standard (JCPDS) database. The average lattice constant calculated according to this scheme was a = 10.1273 Å, which is larger compared to the lattice parameter of 10.1195 Å for pure In2O3, which indicates the presence of Sn, which changes the behavior of oxygen ions.