Search

The issue of composing a layout of a photovoltaic system is associated with solving the issue of optimizing the tilt angle of the module relative to the horizon and cardinal points in order to maximize the solar radiation flux at its receiving surface. The efficiency of the photovoltaic module functioning is inherently related to the conditions of its illumination, which are determined by their spatial orientation and mutual placement (technological interval between the rows of modules). Partial shading is one of the main reasons for the decrease in the photovoltaic system efficiency. A lot of research in the field of photovoltaic module shading is aimed at studying its electrical characteristics and practically does not consider the joint solution of the issues of their geometric and spatial placement. The purpose of the study is to analyze the impact of the technological interval between the rows of photovoltaic modules in the limited area on the efficiency of their functioning, taking into account the spatial orientation of their receiving surfaces and the size of the area allocated for their installation. The formulation and solution of the issue of determining the layout of the photovoltaic system modules, which ensures the maximum total efficiency of the functioning of the modules, makes it possible to obtain the highest level of electrical energy generation per 1 m2 of modules with the optimal area occupied by them. The analysis of the options for filling modules (for various cases of their spatial orientation) of the photovoltaic system located in the limited area (constant area and shape of the area for their placement) showed that an increase in the number of rows does not always give an increase in electric power generation proportional to the area of modules put into operation due to deterioration of their illumination conditions and it can even lead to a decrease in the utilized solar energy resource below the similar value obtained on the receiving surface that is horizontal to Earth's surface. [ABSTRACT FROM AUTHOR]

A nonstationary numerical procedure and program for determining the heating temperature through flat "transparent screens" (TSs) of solar power plants have been developed. The developed procedure makes possible to consider volume absorption of incident and self-radiation of TSs. The program is verified according to mean equilibrium heating temperatures for the glass under a stationary mode of operation. We obtained that under a TS thickness up to 10 mm, the difference between mean equilibrium temperatures is lower than 0.1%. We reveal that a temperature drop in TSs of solar power plants even for glass with a thickness up to 5 mm and if the receiver is heated up to 60°С is not higher than 0.5–0.7°С. We obtain the same gradients in the numerical models for TSs with surface absorptance and heat spectrum emission, but the difference between absolute temperatures can run up to 6°C. The procedure and the program with volume absorption and emission in TSs can be used in nonstationary heat models for solar collectors and energy efficient windows and under heating 1D semi-transparent bodies by solar or laser radiation. [ABSTRACT FROM AUTHOR]

The information on the various parameters of solar radiation should be sufficient, relevant, accessible from the point of view of design, optimization, and justification of the parameters of photovoltaic installations in the place of its proposed location. However, in spite of the large number of sources of actinometrical information, certain difficulties arise when conducting solar engineering calculations associated with database limitations, the large distance from the considered geographical point, or the laboriousness of the research that are needed to be carried out. The purpose of the study is to analyze the available data on the solar energy resource for a set geographic point (46.8° N, 40.6 E), obtained by the indirect method for assessing the parameters of solar radiation using data from ground-based metrological stations; indirect method for assessing the parameters of solar radiation using satellite measurements; calculated method for determining the intensity of solar radiation; and experimental study of the characteristics of solar radiation. The analysis showed that not all approaches provide data on the direct and diffused components of solar radiation. In addition, the availability of hourly values of solar radiation is very important, because only they make it possible to predict the mode of operation of a photovoltaic installation and coordinate its mode of operation with the load schedule of the consumer. The deviation between the data of various sources of actinometrical information can reach 53.0% for hourly values, 58.1% for daily values, 43.1% for monthly values, and 39.1% for annual values, and can significantly affect solar engineer calculations for the choice of parameters of the photovoltaic installation equipment or make great adjustments to the issues of justifying the economic efficiency and feasibility of photovoltaic installation application. [ABSTRACT FROM AUTHOR]

The problem of deposition of dust particles with sizes of large wavelengths of the photoactive part of solar radiation on solar batteries (SBs) is considered. Under the assumption that dust particles in the air do not collide and are deposited on the SB in one layer, formulas are obtained to determine the area of shading of the SB by dust particles in time. These dependences also take into account the size of dust particles, their concentration in air, the angle of incidence of sunlight and the angle of inclination of the SB to the horizon. It is shown that the shading area changes in time mainly linearly, but also has a nonlinear daytime component, which depends on the angle of incidence of sunlight on the SB. The influence of the angle of incidence of the rays on the shading is already noticeable at angles of more than 200. The formulas obtained make it possible to estimate the dynamics of shading of the SB by solid particles of dust and to estimate the frequency of its cleaning from dust (at a given power loss). So, even with standard levels of concentration of dust particles with dimensions of 2.5 and 10 microns and an admissible drop in power of the SB by 5%, the frequency of the SBs cleaning is only about 30 days. The results of the study show that when determining the optimal angle of inclination of the SB, it is necessary to take into account the dust factor. The obtained dependences can also be used to assess the dustiness of flat transparent enclosures of solar installations. [ABSTRACT FROM AUTHOR]

A new method for approximate numerical calculation of the temperature field and heat losses by convection and radiation (Q) of a two-layer cylindrical heat accumulator (HA) with symmetrical boundary conditions is presented and its software implementation is given. We estimate the accuracy of an approximate solution with a known analytical solution for the case with convective heat losses only and with a constant heat transfer coefficient and we reveal that the error of the approximate method starts to exceed 1% when Fo > 2 or when the HA temperature is already less than a half of the HA initial temperature (90°C). It is shown that under permissible heat loss of 10% for 10 h for a HA with R = 0.2 m, the thermal insulation thickness should be about of 5 cm, and the relative heat loss depends greatly on the HA volume. It is important to investigate the effect of thermal insulation emissivity under a small insulation thickness: if thermal insulation thickness is higher than 2 cm, its influence is only of about 5–6%. [ABSTRACT FROM AUTHOR]

The purpose of the study is to substantiate the parameters and operation mode of the photovoltaic installation as part of the power supply system of real agricultural enterprise in order to reduce the cost of paying for electric energy. The object of research is the system of intra-workshop lighting of two departments of the baking mill in the Rostov oblast. Placing photovoltaic modules on the inclined part of the industrial building's roof of the mill compartments, having an inclination angle of 10° relative to the horizon measuring 39 × 10 m and oriented by the wide side strictly to the South. Three options for the layout of the solar power installation with photovoltaic panels were considered: option 1– maximum power supply to the consumer from the solar power plant in the summer (30 modules); option 2–generation mode without the use of electric energy storage devices; option 3–14 modules and the presence of an electric energy storage system. Specific capital investments in the third option increased by 40% in comparison with the second option, although the installed capacity of the installation increased only by 27.2%. The increase in the power of solar installation to 5.4 kW requires specific costs 2.5 times greater than for the second option. The calculation results allow us to highlight the lowest value of the prime cost of generated electric energy, obtained for the second option, which is 4.33 rubles/(kW h). Thus, the use of photovoltaic installations on industrial building roofs of agricultural facilities makes it possible to reduce the payment for each kW h of consumed electrical energy almost by 2.5 times. [ABSTRACT FROM AUTHOR]

Low-potential solar plants, including flat-plate water-heating collectors (FSWHC), are complex systems in terms of heat engineering. A problem in the development of both stationary and non-stationary heat engineering FSWHC models is to specify convective heat exchange in SWHC channels. This paper considers the features and conditions of convective heat transfer in SWHC channels to water. It is shown that the water flow hydrodynamic and thermal stabilization sections in FSWHCs and at potential speeds of their heat carriers reach only 10 to 13 cm in length and the convective heat exchange in SWHCs can be calculated at a constant value of Nu. It is found that the differences in temperature between the walls of a SWHC channel and between the wall and the liquid will not exceed 10 and 5°C, respectively. These conditions make mixed free and forced convection in SWHC channels possible. Since the heat mainly comes from the upper walls of the channel, this determines the need for pilot studies to determine the distribution of temperature on the walls and in the liquid along the channel length and the difference in temperature between them. The heat exchange in SWHC channels can be heavily affected by free convection. An important issue when elaborating design models of heat exchange in SWHCs is the possibility of applying the convective heat exchange formulas used for plates to the walls of SWHC channels. [ABSTRACT FROM AUTHOR]

To evaluate the possibility of obtaining the maximum of electric power generation at a preset point of time by varying the spatial orientation of photovoltaic modules, its effect on the amount of utilized solar radiation was studied. The experiment was conducted by the example of Zernograd, Rostov oblast, Russia, with specially designed research equipment. The analysis of input of solar radiation to surfaces with different spatial orientation revealed that, owing to different combinations of spatial placement of the receiving site with respect to cardinal directions and the horizon line, it is possible to shift the maximum of power takeoff with photovoltaic modules relative to midday to the morning and evening time about by 4.5 h. [ABSTRACT FROM AUTHOR]

In designing generating solar-engineering devices, the first priority is the predesign study of the potential of local resources of solar energy at the places where they may be located. Currently, actinometric information is obtained in several ways. They include direct measurement of solar-radiation characteristics at meteorological stations or from satellites and analytical methods for calculating intensity of solar radiation. Despite the significant number of sources of actinometric information, it seems impossible to evaluate the potential of incoming solar energy in the region, to substantiate the composition and parameters of solar-power-plant equipment, and to predict its operation at the initial stage. Using the example of the town of Kamyshin in Volgograd oblast, the sufficiency of required actinometric information is analyzed for further solar-engineering calculations and the data accuracy and limits of their applicability are estimated. [ABSTRACT FROM AUTHOR]