The paper considers the main trends in the development of the world market of solar photovoltaics over the past few years. It is shown that the industry is a very rapidly evolving one among the branches of renewable energy and modern industries as a whole. It is obvious that the prime cost of the of solar energy being produced is rapidly approaching the price of electricity generated by traditional methods at nuclear power plants and thermal power plants. The aspects of the development of the efficiency of modern research solar cells made of various materials using innovative technological solutions based on the data provided by the National Laboratory for Renewable Energy (NREL, USA) in 2017 are noted. For the convenience of analysis, the research solar cells are divided into four technological groups. The advantages and disadvantages of solar cells, including the specific features of their production and prospects for development are considered separately for each group; the maximum efficiency for the year 2017 is estimated. A possible alternative to the future development of modern high-performance single-transition solar cells is the use of fundamentally new materials based on nanoheteroepitaxial structures with quantum dots. The possibilities of absorption (processing) by such structures of both short-wave radiation and long-wave part of the solar radiation spectrum for the purpose of generation of electric energy by increasing the efficiency of solar cells on their basis have been demonstrated. The optimal materials for their production and the principles of action of high-performance solar cells on their basis have been considered. The prospects of manufacturing nanoheteroepitaxial structures with quantum dots by liquid-phase epitaxy with pulse cooling of the substrate have been substantiated.

The use of wind turbines to create wind energy is one of the main alternatives to the traditional technologies of power generation. The exclusion of combustion products emissions at thermal power plants that operate on hydrocarbon fuel, as well as the exclusion of the fuel component of the cost of electricity generation makes the wind power technology very attractive. However, the rigor of the operation requirements of wind turbines as part of power systems, low density of the flow of primary energy source and the lack of control of it, low utilization of installed capacity, limited operating life, shutdowns in the conditions of squally gusts of wind and ice formation, large areas of alienated land, the impact of noise and infrasonic vibrations and the problems of utilization of large-size structural elements and foundations require a comprehensive analysis of conditions of wind turbines application. Despite the absence of desert areas and of restrictions on the construction of ultra-high structures the analysis of natural and climatic conditions of Belarus demonstrates favorable natural and landscape conditions for the development of wind power generation. The principal task is to choose the location of wind power plants with due regard to environmental requirements, temperature and humidity conditions, terrain and geological features of the location. The results of calculations of the wind flow conditions showed the preference for the joint application of the Weibull and Rayleigh functions that provide the confidence interval of the approximation of the wind speed function, while the terrain specific features make it possible to expect to obtain higher values of the established capacity utilization factor. The development of a distributed energy generation accompanied by Smart Grid technology wide use over electric networks (which would provide new opportunities for consumers and make it possible to eliminate the monopoly of powerful power plants and to reduce burden of basic costs of big power production) ought to be considered as obvious prospect of wind power plants application.

A new Simulink model of a photovoltaic cell has been proposed. The model is focused on the use of a standard SimPowerSystems library with power engineering elements from the MatLab/Simulink software package. The model allows altering the values of solar irradiance, photovoltaic cell temperature and load resistance. The results of the model application are the calculated values of voltages and currents at the photovoltaic cell output. The Simulink model that has been developed implements the known dependence of the photovoltaic cell volt-ampere characteristic by using both standard MatLab/Simulink blocks and special electric SimPowerSystems library blocks. The model is characterized by the fact that the series and parallel resistance of the photovoltaic cell are made in the form of resistors from the SimPowerSystems library. The main calculation algorithm is implemented programmatically by using the “C” programming language. To increase the algorithm stability to algebraic cycles the restrictions parameters are introduced. A new technique of calculating the photovoltaic cell model parameters based on experimental data has been proposed. The technique includes the preparation of a system of equations with experimental values of the photovoltaic cell voltages and currents. Experimental tests have been carried out for the photovoltaic module OSP XTP 250 under different solar irradiance values. The tests showed that the relative error of the Simulink model that has been developed does not exceed 12 %. The Simulink model makes it possible to build photovoltaic modules and then to build schemes of photovoltaic power plants as a part of power supply systems. Due to the latter it is possible to simulate the electricity consumers’ work, weather conditions, and the presence of shadows or pollution on the surface of photovoltaic modules. Also, one can carry out a simulation of increasing failures in power plant photovoltaic modules, e.g. simulating of modules efficiency reducing because of their degradation, or simulating of modules series resistance increasing because of the photovoltaic cell internal contacts deterioration. The Simulink model that has been developed can be used both at the design stage and at the stage of photoelectric power plants operation.

In this article, the authors reviewed a new technology to prevent the formation of asphalt-resin-paraffin deposits by the thermal method of electrothermal impact on the oil wellbore shaft using a wind-electric installation as an autonomous power source. The advantage of this thermal stimulation technique lies in its continuous nature, which will allow keeping the clear opening of the tubing constant. The scheme of the autonomous system for down-hole electric heating of oil is presented. A tubular or induction heater can serve as an electric heating element placed in the well. The heating element of the system can be used in the wells exploited by freeflow, gas lift and mechanized methods, while its installation does not require an overhaul. The paraffin oil saturation temperature and temperature distribution over the depth of the well were defined. The amount of heat, which must be transferred to the oil mixture in the tubing in order to ensure effective operation of the well, taking into account the dynamic state of the system, is calculated. The optimal depth of the heating element's location in the well and its power was determined. The calculation of the required power for wind-electric installation to maintain the set temperature in the wellbore was performed. Having conducted the studies, it was revealed that in order to prevent the asphalt-resin-paraffin deposits formation on the tubing walls of oil wells, it is expedient to use the in-line heater, which maintains the average steady-state temperature along the wellbore and at the wellhead above the initial crystallization point of the asphaltresin-paraffin deposits. The application of the developed electrothermal system is relevant in the conditions of formation of asphalt-resin-paraffin deposits in the wellbore shaft at the fields, which do not have a connection to the centralized power grid.

The main criterions to assess the quality of operation of distribution electrical grids are considered. It is shown that in power supply companies as early as at the pre-design formation of the strategy of modernization and reconstruction of electrical grids, it is necessary to choose the optimal measures for each mainline with a clear sequence of implementation of the selected measures in the electrical grid taking into account prospects of its development. A mathematical model of the classification of mainlines of distribution electrical grids has been developed according to the state of their operation, viz. successful operation, strenuous operation and unacceptable operation. On the basis of this model an algorithm for a choice of the optimal technical measures for the reconstruction of mainlines has been formed depending on their state: for mainlines in the strenuous state it is possible to replace the wire of the section or an installation of a battery of statistical capacitors at the remote transformer substations; for mainlines in the unacceptable state, in accordance with the results of an expert assessment of possible measures taking into account the electrical grid development, the prospects of increase of the load, the construction of unloading points, the connection to the distributed generation electrical grid, a decision is being made to replace the wire section, to transform a part or the whole electrical grid to higher voltage level. This allows formalizing the procedure for the choice and implementation the outlined measures as early as at the stage of pre-design formation of the modernization and reconstruction strategy so to provide an efficient use of funds for the reconstruction and technical retooling of distribution electrical grids in order to improve the quality of their operation. The mathematical model and the algorithm for the choice of the optimal technical measure for the reconstruction of the mainline taking into account the prospects for development that had been developed was tested during the development of the optimal strategy for the development of 6–10 kV distribution electrical grids in the Western region of Ukraine.

The article presents a mathematical simulation of the electromagnetically excited generator of reciprocating type, which resulted in an equivalent circuit diagram, a magnetic circuit design of the generator and some expressions describing the electromagnetic processes in the electromagnetically excited generator of reciprocating type. The nonlinear mathematical model of the electromagnetically excited generator of reciprocating type has been developed. In order of the experimental verification of the adequacy of the mathematical model of the reciprocating electric generator, as well as of the validity of the assumptions made, a breadboard sample of the reciprocating electric generator has been made consisting of a fixed part in the form of two U-shaped magnetic cores and a moving part representing an H-shaped magnetic cores. There is focused operating winding on both the U-shaped magnetic cores. The N-shaped magnetic core is coiled with excitation winding which is connected to a DC power source. In a breadboard sample of the reciprocating electric generator a drive motor of 100 W with an amplitude of reciprocating oscillations of the moving part equal to 16 mm, and a frequency of oscillations adjustable in the range from 5 to 50 Hz is used in order to simulate a free-piston engine. The main characteristics of the generator (viz., idle speed and external characteristics) have been experimentally obtained. Comparison of experimental and calculated results demonstrated their discrepancy of no more than 4 %; therefore, the nonlinear mathematical model reflects the characteristics of the generator of longitudinal type with a high degree of adequacy.

In industrial heat-technological installations for accelerated hydration of concrete, which are the main element of the thermal power system of enterprises of concrete products, the modes of heat treatment and the organization of heat supply to the product processed in them are due to the required temperature distribution in the volume of the concrete body, providing a given product quality. In order to optimize the processes occurring in such thermal device, a nonstationary mathematical model of the hardening process of the concrete product subjected to heat treatment has been developed, which allows calculating the spatial distribution of its volume temperature and degree of hydration of the active part of the cement clinker. The proposed model is based on the use of a non-stationary three-dimensional heat equation that takes into account the internal heat release due to the exothermic reaction in a concrete body and determines the degree of its hydration and hardening. For a given mode of heat treatment with the use of the finite volume method, numerical simulation of the hardening process of a symmetric concrete object of cubic shape is performed. In the selected points of the object under study, depending on the time of heat treatment, the rates of temperature change and the degree of hydration were calculated and their analysis was carried out. When analyzing the graphs of the temperature change rate, the characteristic inflections consistent with the given thermal mode of the heater were revealed. By a given mode of heat treatment of the form of “temperature rise – isothermal exposure – temperature decrease” in the selected points of the object there is an increase in temperature compared with the specified maximum temperatures of isothermal exposure, which is associated with the exothermic effect of the hydration reaction. A temperature shift relative to the specified thermal mode of the heater due to the non-equilibrium of the concrete hardening process is observed. The proposed mathematical model allows determining the time of reaching a preset temperature for any point of the internal space of the product subjected to heat treatment that can be used in the when designing of new and modernizing of existing thermal technological installations of accelerated hydration of concrete, as well as systems for automated control of the concrete hardening process in these devices. The results obtained during the study are in satisfactory agreement with the experimental data of other authors.

Currently, about 90–95% of generic controllers use the PID algorithm to generate control actions, while 64% of the PID controllers are used in single-circuit automatic control systems. Most of industries (power industry among them) use hundreds of automatic control systems. The quality of their work is the basis of economic efficiency of technical processes, ensuring safety, reliability, durability and environmental friendliness of both technological equipment and automation equipment. There are different modifications of PID-controller structure implementation. In practice the ideal PID controller with a filter and the classic PID regulator (serial connection of the ideal PI controller and the real PD regulator as the direct action elements) are widely used. The problem of choosing a rational structure and a method of parametric optimization of PID controllers, which provide the best direct indicatives of the quality in the development of the main effects in single-circuit automatic control systems, becomes urgent. However, only for the classical PID controllers, which are widely used at present, there are more than three hundred methods for adjusting the three parameters of the optimal dynamic adjustment, as well as the ballast time constant. This results in arising a problem of substantiation of the best structure and method of parametric optimization of classical PID regulators. As a basic option, one of the simplest and most obvious one, viz. the method of automated adjustment of the controller in the Simulink MatLab environment had been chosen, which was compared with the method of full compensation in general for objects with a transfer function in the form of an inertial link with a conditional delay. Two variants of control action realization on the basis of the structural scheme of the optimal regulator developed by the Belarusian national technical University were also offered. In contrast with the classic PID controller, the optimal controller has one parameter of dynamic adjustment setting. The results of simulation of transients at basic perturbations confirmed that the best direct indicatives of the quality are provided with an optimal regulator, which makes it possible to recommend it for wide implementation instead of the classic PID controllers.