An assessment of the energy efficiency of a hybrid solar-geothermal power plant is performed taking into account the geothermal resource of one of the productive well (TD4) and the direct normal irradiance at Tendaho geothermal site in Ethiopia. A thermodynamic model of a single-flash geothermal plant integrated with a parabolic trough concentrated solar power system is developed to estimate the energy production in a hybrid solar-geothermal power plant. In the hybrid power plant, the parabolic trough concentrated solar power system is employed to superheat the geothermal steam in order to gain more energy before it expands in the turbine. Thermodynamic analysis, based on the principles of mass and energy conservation, was performed to assess the efficiency of the hybrid power plant at the given conditions of Tendaho geothermal site. A figure of merit analysis was also employed to evaluate whether a hybrid power plant could produce more power than two stand-alone power plants namely the solar and geothermal power plants that constitute the hybrid power plant. Results showed that the hybrid power plant technically outperformed the two stand-alone power plants. By integrating the two energy resources, the hybrid power plant proved to generate 7158 kW of electricity which is larger than the sum of the two stand-alone power plants (geothermal and solar).

The article deals with the work of heat and power units of thermal power plants in the conditions of disaggregation of the heat load schedule. The purpose of the work is to increase the efficiency of operation of CHP units operating under the conditions of the zoned temperature schedule. To achieve the obtained results, mathematical modeling based on the methods of differential-exergetic and thermodynamic analysis; methods of material, energy and exergetic balances. Research has shown that in order to increase the efficiency the original method of splitting the temperature graph into three zones can be used, each of which is characterized by the method of regulation of heat supply, and to assess the effect of the minimum fuel consumption criterion can be used. The method of determining the equivalent design temperature, which takes into account the regime peculiarities of heat and power units in the form of a method of regulation of heat supply, is developed. Study has shown that three design points should be available when zoning the temperature schedule. Based on optimization calculations for standard sizes of heat and power units of a wide range of capacities, the calculations show that the optimal parameters of heat and power units in the conditions of zoning of the temperature schedule as a whole correspond to the standard values. In addition, it is shown that in each zone of the temperature schedule there is a saving of fuel, which can be from 3 to 30% depending on the type of power unit, its capacity and zone of the temperature schedule, and the annual fuel consumption of the heat and power units can be reduced by approximately 10%. It is shown that when conventional power units operate according to the zoned temperature schedule and in the first zone (quantitative regulation), preference should be given to power units with steam production. In the second zone (mixed regulation), the operation of power units with steam extraction and heat and power units is equivalent. In addition, in the third zone (qualitative regulation) preference should accrue to heat and power units.

In the article, on the basis of the theory of thermodynamic potentials, a study was made of the quasistatic Phillips and Carnot heat engines in which a comparative analysis was made of their work both for cycles with a working body, an ideal gas, and for cycles with a working body, real gas. On the basis of the conducted research, it was established that the existing formulation of the Carnot theorem is valid only for the working fluid “ideal gas”. In general, based on the above calculations, the Carnot theorem can be formulated, for example, like this: “The efficiency of a reversible heat engine is maximum, does not depend on the properties of the heat engine and is a function of the temperatures of only hot and cold tanks: η=1-ƒ(t₁,t₂), where ƒ(t₁,t₂) is a function only of the temperatures t₁ and t₂ of the hot and cold tanks. This formulation is valid only for working fluid ideal gas. In the case of using real gas as a working fluid, the efficiency of a heat engine, in addition to dependence on the temperatures of hot and cold tanks, is a function of the thermodynamic characteristics of the working fluid and the type of heat engine, and reaches its maximum value for this type of working fluid and engine type if there is reversibility the system under consideration».

The development of energy storage and storage systems is becoming a potential method for solving the problems of the global energy system. However, there are technical and non-technical barriers to the widespread distribution of energy storage devices. In this regard, it is necessary to identify innovative processes, mechanisms and systems that allow developments in the field of energy storage to contribute to solving the problems of the energy system, as well as to ensure industrial growth at the expense of companies engaged in the development of technologies. This article discusses current advances and trends in energy storage innovation. The scientific novelty of the article consists in a comprehensive review of the current state of affairs in this area and the determination of the main directions of development.

The work is to research the dielectric characteristics of vegetable-based oil during cyclic temperature aging and to determine the parameters necessary for monitoring the state of the oil, and to develop a method for diagnosing an insulating liquid. The research technique included measuring the dielectric constant of the oil and the tangent of dielectric loss for oil that underwent cyclic temperature oxidation. Thermal oxidation consisted in cyclic heating and natural cooling of the sample during the day without exposure to light. This was done to simulate changes of the temperature in the tank of the power transformer with a changing load schedule during the day. For comparison, the dielectric constant of the base sunflower oil was measured, which was stored in a glass container at room temperature without exposure to light. The results showed that the dielectric constant of vegetable-based oil increases linearly in the oxidation process. The increase in permittivity is associated with an increase in the number of polar molecules as a result of the formation of secondary oxidation products. Under the influence of temperature, the chemical composition of the oil changes and the primary oxidation products — hydroperoxides — are formed. Vegetable-based oil oxidation products do not form a precipitate. Instead, the oil begins to thicken and polymerize. The developed method of diagnosing of an insulating liquid is to determine a coefficient proportional to the growth rate of the number of polar molecules in oil. The results show that monitoring only the tangent of dielectric losses does not give information of the state of vegetable-based oil and is not always an indicator of oxidative processes in oil. The thermal oxidation process has a steady effect on the dielectric constant, which indicates changes of the oil as a result of polymerization.

In this article, a mathematical simulation of a double pipe heat exchanger is carried out, having the longitudinal rectangular fins with the dimension of (2*3*1000) mm, mounted on the outer surface of the inner tube of the heat exchanger. In this paper, the advantage of using of that type of fins and its effect on the effectiveness of the heat exchanger are studied with the help of the computer program. The carried out research allowsmaking the calculation to find the optimum design parameters of heat exchangers. The outer tube diameter is (34.1mm) while the inner tube diameter is (16.05mm). The tubes wall thickness is (1.5mm) and the model length was (1 m). The hot water is flowing through the inner tube in parallel with the cold water that passing the outer tube. The hot and cold water temperature at the inlet is (75°C & 30°C) respectively. The mass flow rate inside the central pipe is (0.1 kg/s) while the annular pipe carrying (0.3 kg/s). In the present work, the program ANSYS Workbench 15.0 was used to find out the results of heat transfer as well as the behavior of liquids inside the heat exchangers.

This article will help to consider the problem of thermodynamic optimization of heat power equipment. Solving this issue will allow to increase the energy efficiency of thermal systems by reducing the cost of energy resources. There is a large number of methods for studying power plants, and we will combine two of them: the exergy method and the pinch method. Exergy analysis of thermal systems shows quantitative and qualitative characteristics of efficiency. The pinch method allows us to solve specific design problems to optimize the parameters of heat power facilities. The pinch analysis is based on enthalpy, which does not take into account the heat potential. We propose to conduct a pinch analysis of thermal energy sources using exergy, which can better assess the potential of heat fluxes and show the dependence of the energy of heat fluxes on the ambient temperature. The article provides an exergy analysis of a direct-flow boiler PP2650-255 GM using the pinch method. The results of our work show that in order to increase the energy efficiency of the boiler, it is possible to change the area of the heating surfaces of the economizer and air heater. Thus, exergy pinch analysis is an effective method for increasing the energy efficiency of heat power equipment.

In the event of accidents in power systems associated with a reduction in frequency in order to prevent the complete repayment of the energy district and accelerate the elimination of the accident, frequency division automatics (FDA) are used. Existing technical solutions for the implementation of the FDA do not always provide a balance of the generated and consumed power under the action of the FDA, since the current circuit-mode situation is not taken into account. The aim of this work is to develop effective algorithms for the functioning of adaptive FDA, which allocates power units of a power plant to a balanced load of an isolated energy district, taking into account the current circuit-mode situation. To achieve this goal, we use the method of structural and parametric synthesis of emergency control algorithms, which consists in creating a composite algorithmic model of adaptive FDA. The result of this work is the developed algorithmic model of an adaptive FDA of a power plant, consisting of input and processing algorithms for input analog signals of a FDA, algorithms for input and processing of input discrete signals of a FDA, algorithms for generating start-up organs of a FDA, algorithms for allocating a power plant to a balanced load of a power district. The proposed algorithm for the functioning of adaptive FDA is universal and allows you to automatically allocate power units of a power plant to a balanced load of an isolated energy district, regardless of the type of accident and its cause, the configuration of the electrical network and the values of electricity generation and consumption, as well as the current circuit-mode situation.

This article provides a comparative analysis of unsteady gas dynamics and instantaneous local heat transfer of pulsating flows in the intake and exhaust systems of reciprocating internal combustion engines in the case of a turbo-compressor installed without it and based on the results of experimental studies. Experimental studies were carried out on full-scale laboratory stands under the conditions of gas-dynamic nonstationarity. The article provides an original method for determining the instantaneous values of the local heat transfer coefficient in pipes, and describes the procedure for conducting experiments. It has been established that the presence of a turbo compressor in the gas-air system of a piston engine leads to significant differences in the patterns of changes in the gas-dynamic and heat exchange characteristics of pulsating flows. The obtained new data can be used to improve engineering methods for calculating the quality indicators of gas exchange processes, to refine the working processes of the engine when installing a turbocharger, as well as to develop advanced gas-air ICE systems with turbocharging.

To determine the results of the transmission of electrical energy through the power line from the source to the consumer, it is necessary to have accurate information about the parameters of such line. Determining these parameters for operating lines with a minimum error is quite a laborious process. But if a researcher is interested only in voltages and currents at the end and at the beginning of a homogeneous section of a three-wire transmission line, then it is sufficient to use the theory of multipoles. In particular, the theory of eight-poles. The article presents the method of experimental determination of the longitudinal and transverse parameters of the studied transmission line. The study used the methods of natural experiment using an appropriate fleet of electrical devices, and methods of indirect measurement of the desired parameters. The experiment consists of six stages; on the basis of the obtained data, it becomes possible to determine the numerical values of the main parameters of the studied section of power transmission lines, with which it is possible to establish a quantitative relationship between the input and output characteristics of electrical energy. In addition, the described method, in principle, can be applied to the analysis of active eight-terminal networks of a similar design. This means that the proposed methodology can provide a comprehensive analysis of the studied object and will help to identify the parameters of an overhead power line at the construction stage or for its connection to the consumer. The article presents the experimental setup scheme, describes the experimental methods, and estimates the error of the calculation results.

The purpose of the work is to reduce losses and increase energy saving in electric networks. To achieve this goal, a multilevel topology of the electrical network and an asynchronous method for transferring electrical energy between nodes including a load, energy sources, energy storage devices connected in an appropriate manner are proposed. It is shown by the mathematical method that this network topology allows using energy storage devices controlled appropriately and using tele-information technologies to optimize the balance of electric energy in the network, achieving equality of the generated and consumed electricity. Such a network topology and a method of transmitting electrical energy can be the basis of digital technologies in the energy sector (ENERNET).

The relevance of the research problem is chose of effective technology of strike protection wire monitoring in span with use of technical system of analysis of technical condition of strike protection wire of 110 kV voltage power line for complex assessment of the impact of both external climatic factors from wind and ice loads and the magnitude of the thermal elongation of the strike protection wire with influence of current during de-icing process. Analysis of the strike protection wire mode and their limiting values of mechanical strength allow evaluation of the effectiveness of events of prevent of accidents and reduce the undersupply of electricity to the end consumers. Visualization of the operative parameters of the strike protection wire in the span of the overhead power line will allow reduce the time to make decisions on the prevention of accidents of lines. Algorithm of monitoring of operative parameters of wires of overhead power lines base on information of longitudinal and transverse angles received from sensors installed directly on the strike protection wire.

The urgency of the problem lies in the formation of mathematical models of electromechanical converters corresponding to the objects of study with high accuracy. An experimental-analytical assessment of transient modes of a DC motor based on an installation for the study of electrical machines has been carried out. Based on the results obtained, an approximation of transient process graphs was carried out using the least squares method and an approximate polynomial of the corresponding order was selected with the closest imminence to the dynamic properties of the object under study.

In the electric power industry of Russia and abroad, special attention is paid to the problem of an increase in the number of accidents caused by damage to high-voltage insulators in high-voltage equipment. An analysis of emergencies at substations and open switchgears [1- 2, 4] was carried out, which showed that in most cases the causes of damage to high-voltage insulators are natural aging in an applied electric field, overvoltage, and the presence of initial defects in the manufacture of high-voltage insulators. Based on this fact, we developed various methods of non-contact diagnostics of high-voltage insulators in order to identify defects at an early stage of their development. Particular attention was paid to the method of partial discharges because the characteristics of partial discharges provide information on the parameters of defects. The article describes a set of non-contact methods for remote diagnostics of high-voltage insulators; a two-channel method for remote diagnostics of the operating state of high-voltage insulators, based on the registration of partial discharges by electromagnetic and acoustic sensors; a device that allows visual inspection and the search for faulty high-voltage equipment; remote non-contact method for recording electric fields of high tension of industrial frequency, as well as their spatial orientation based on the electro-optical effect. We developed a mock-up of a portable diagnostic device for implementing research methods for high-voltage dielectric elements to diagnose their technical condition using the described complex of non-contact methods. The measuring device as part of a portable diagnostic device consists of a set of sensors for collecting diagnostic information detected by electromagnetic, acoustic and electro-optical sensors and a voltage phase signal applied to the studied highvoltage insulator. The simultaneous use of several sensors at once made it possible to increase the accuracy of localization of partial discharges in high-voltage insulators. Visualization of diagnostic results is possible at the control room in the form of amplitude-phase, frequencyphase and amplitude-frequency diagrams of the distribution of characteristics of partial discharges and on a portable device in the form of radiation intensity from the selected sensor. A portable diagnostic device made it possible in laboratory conditions to study electrophysical processes in various dielectric materials and products under the influence of strong alternating electric fields. A study was made of the features of defects on the rod and the terminal-terminal contact, a diagram of the electrophysical processes accompanying the emission of partial discharges was constructed, and the causes of their occurrence were established.