


Vol 54, No 3 (2018)
- Year: 2018
- Articles: 14
- URL: https://journal-vniispk.ru/0003-701X/issue/view/8926
Direct Conversion of Solar Energy to Electricity
A Novel Auto-Scaling MPPT Algorithm based on Perturb and Observe Method for Photovoltaic Modules under Partial Shading Conditions
Abstract
Maximum Power Point Tracking (MPPT) controller is required in a solar photovoltaic (PV) system to deliver the maximum power to load from PV module. This paper proposes a novel stepped MPPT method to realize a simple MPPT controller, which can track the real maximum power point (RMPP) even under partial shading conditions. The proposed algorithm is started by scanning the characteristic curve of the PV modules to detect the global maximum power point and then the algorithm will be switched to the conventional P&O algorithm to track the true maximum power point. The obtained simulation results, using Power electronic simulation software (PSIM), are compared with those found using the P&O method to confirm the performance of our proposed MPPT method even under non-uniform solar irradiation.



Fractal Control of the Electron Spectrum of the Interfaces in Solar Elements Based on Covalent Semiconductors
Abstract
Based on a combination of the Madelung-Seitz and Phillips-Penn approaches, the effect of fractality of the interface on its electronic structure in a covalent semiconductor solar cell is considered. The possibility of pumping a local level from the region of recombination to the region of attachment and back is found. A number of applications are considered, in particular, a new mechanism of radiative degradation by lowering the fractality of the interface.



Solar Engineering Materials Science
Thin Semiconductor Films of Fullerene C70 Nanoaggregates on the Surface of a Plane Glass Substrate
Abstract
It was shown for the first time that, in the volume of an evaporating drop of a fullerene C70 solution in toluene located on the surface of a glass substrate, the self-organization of C70 molecules occurs and crystalline nC70 nanoaggregates of a spherical shape are synthesized. Films of nC70 nanoaggregates are deposited on a plane surface of a glass substrate. The physical mechanism of the self-organization of C70 molecules and the formation of large nC70 nanoaggregates are proposed, namely, Ostwald ripening, according to which relatively large nC70 nanoaggregates grow through smaller ones. The possibility of using thin films as solar transducers is discussed.



Solar Power Plants and Their Application
Heat Transfer Coefficient from the Sheet-Piped Light-Absorbing Panels of the Flat-Plate Solar Water-Heating Collectors to the Heat Transfer Fluid in Their Heat-Removing Channels
Abstract
It has been proposed to introduce a new parameter into the practice of the heat calculation and testing of the flat-plate solar water-heating collectors (FSWHCs)—the coefficient of heat transfer from the light-absorbing panel (LAP) to the heat transfer fluid in its internal heat-exchange channels (HECs) reduced to the unit area of the frontal surface of their cases. The mechanism of the formation of this parameter is studied, the design expression is derived, and a practical example of the calculation to define its value is performed. The structures of the flowing LAPs of a sheet-piped thin parallelepiped form are selected as the objects of the investigation. The reliability of the results of the investigations is proved by comparing the values of the specific (relative to the area unit of the frontal surface of the case) heating efficiency of the collector obtained based on the various formulas.



Exergy Analysis of Solar Still with Sand Heat Energy Storage
Abstract
This paper studies the experimental and exergy analysis of solar still with the sand heat energy storage system. The cumulative yield from solar still with and without energy storage material is found to be 3.3 and 1.89 kg/m2, respectively for 8-h operation. Results show that the exergy efficiency of the system is higher with the least water depth of 0.02 m (mw = 20 kg). Competitive analysis of second law efficiency shows that the exergy efficiency improves the system by 30% than conventional single slope solar still without any heat storage. The maximum exergy efficiency with energy storage material is found as 13.2% and it is less than the conventional solar still without any material inside the basin.



Features of the Design of a Self-Draining Solar Power Plant with an Active Element
Abstract
The calculation dependences for designing a self-draining solar power plant (SDSPP) with an active element in the form of a narrowing device of the Venturi tube are obtained. The calculation dependences for the transient modes in an SDSPP are analyzed from the point of view of the representations of the nonlinear nonequilibrium thermodynamics. It is shown that two steady operation modes of an SDSPP are possible: with and without a break of the jet. It is specified that both these modes merge when the consumption of the heat transfer fluid is equal to the critical value, for which the contraction ratio of the flow in the Venturi tube is defined, and differ when their values are higher than the critical value.



Solar Energy Concentrators
Modeling and Calculation of Optical-Geometric Characteristics of a Solar Concentrator with Flat Fresnel Mirrors
Abstract
The basic characteristics of a concentrator, such as the number of reflectors, their coordinates and orientation, the degree of concentration, and others are determined with the use of the optical-geometric approach depending on the configuration parameters of the concentrator. Based on the presented formulas and numerical results, it is possible to determine the parameters of an arbitrary configuration of a linear-focus concentrator with flat Fresnel reflectors located on a parabolic base. The specific features of the distribution of the energy density over the receiver are determined. The paths of solar beams in the system and formation features of the transverse focal lines of the concentrated optical radiation are graphically analyzed for the case of the exact orientation of the concentrator on the Sun.



Consideration of the Impact of the Environmental Conditions when Designing Heat-Receiving Systems of the Solar Cylindrical Parabolic Modules
Abstract
The aerohydrodynamic and heat exchange characteristics in the cylindrical heat receiver of a solar cylindrical parabolic concentrating module are investigated. The mathematical model is based on the Navier- Stokes equation system for a laminar flow in a channel. The model is implemented using the control volume method. The created computer algorithm allows carrying out parametric studies and revealing the most rational geometric, dynamic, and power parameters of the process. The proposed model describes the general physical outlines of the heat exchange in a cylindrical heat receiver which allows estimating the influence of the environment—wind velocity, ambient temperature, etc.—on it.



Renewable Energy Sources
Thermal Regime in Combined Cultivation Constructions
Abstract
The basic methods of mathematical modeling for thermal engineering calculations of a solar greenhouse in combination with geothermal waters are outlined. The experimental studies and theoretical calculations of the mathematical model are compared. The energy efficiency of the combined use of solar thermal energy and geothermal waters to create a microclimate in the cultivation facilities in the regions of Turkmenistan is generalized. The economic priorities of increasing the volume of agricultural products and the environmental benefits from the use of thermal water in greenhouses in Turkmenistan are given.



Experience and Possibilities of Using Energy Resources of Water Reservoirs for a Complex Purpose Located in an Arid Zone. Part II
Abstract
This paper shows the dependence of the energy indicators of advanced HPSs at reservoirs built for a complex purpose that are located in an arid zone on the genesis of feeding rivers, hydrological regimes, and water use. It reveals the possibility of increasing the reliability of the electric power supply of the reservoirs and prospective hydroelectric power stations (HPSs) in them by wind power plants (WPPs) using the wind energy in the zone of the reservoirs.



Solar Power Plants
Effect of Inlet Air Humidity on Performance of Solar Hybrid Combined Cycle Power Plant
Abstract
The hybridization of conventional power plants by integrating renewable energy technologies is gaining attention in the recent past. These hybrid power plants perform better than conventional power plants and also have less detrimental effects on environment. In the presented research work a solar central receiver is integrated with a conventional gas turbine power plant with a bottoming steam Rankine cycle. The effect of specific humidity of air entering the compressor is on the performance of the power plant is studied. The humidification of air can be done in two ways viz. heating-humidification and cooling-humidification. The performance of the power plant for the afore mentioned processes are compared and it is found that the efficiency of the plant improved by 1% through heating-humidification of air.



Solar Photoelectric Power Station of Maidanak Observatory and the Power Efficiency of Astronomical Telescopes
Abstract
The features of designing, creating, and operating a solar photoelectric power station (PhEPS) for a 10 kW high-altitude observatory Maidanak (Uzbekistan Academy of Sciences) introduced into operation in 2016 to secure continuous and efficient operation and remotely control astronomical telescopes are presented in the paper. Problems regarding a highly efficient modification and features for controlling a Zeiss-1000 astronomical telescope in order to significantly decrease its power consumption are also studied.



Economy and Ecology of Heliotechnics
Photovoltaic Power Supply Unit for the Basic Stations of Cellular Companies
Abstract
The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered.



Erratum


