Techno-economic indicators of renewable (solar and wind) and non-renewable energy sources are systematized, taking into account the interval of their uncertainty for the conditions of the countries of the Commonwealth of Independent States (CIS). The main attention was paid to Russia and the countries of Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan), where there are the most favorable conditions for the development of solar and wind energy. A comparison of renewable and non-renewable energy sources by the criterion of the cost of generated electricity has been made. It is shown that the payment for greenhouse gas emissions increases the competitiveness of solar and wind power plants in the energy markets. Under favorable conditions for renewable energy, solar and wind installations in some areas can produce cheap electricity at a cost of 3–5 cents/(kW×h). With such values, they can be competitive without additional measures to stimulate their implementation. Using the mathematical model REM-2 (Renewable Energy Model), energy sources of different types were compared taking into account system effects. The power supply system consists of photovoltaic converters, wind turbines that enable the possibility of short-term accumulation of electricity and power consumption from a backup power source. Modeling of photoelectric converters and wind turbines operating modes was performed by time (hours) for different values of solar radiation arrival and wind speed. The optimal ratios between electricity production by photovoltaic converters and wind turbines, as well as the optimal level of electricity consumption from the network under different climatic and economic conditions, were determined. The economic efficiency of joint use of solar and wind energy in the CIS countries, primarily in Russia (with the exception of the northern regions) and the countries of Central Asia, is shown.

Nowadays the world energy system faces numerous transitions and shifts of the existing socio-technical regimes towards higher sustainability. Along with it, the sustainable transitions are often being postponed, slowed down or rejected to avoid negative externalities that could threaten the system stability. In this study, we aim to reach the deeper understanding of the externalities of energy transitions and the vulnerability of energy systems under the influence of negative externalities caused by sustainable energy transitions. Using the Externality theory (Baumol, Oates), Sociotechnical transition theory (Geels), as well as Energy sustainability Trilemma Method for the evaluation of the sustainability of energy systems we argue that such externalities need to be treated (internalized, avoided) by special policy measures other than common (classical) ways which may cause slowing down of sustainability transitions and make extra barriers for them. Transitions to more clean and low-carbon energy systems using energy technologies such as solar, wind, small hydro, biomass, waste management, e-vehicles are in the scope of this paper. It classifies the wide range of policy methods (classical and new) being applied separately and simultaneously, and analyses their application in energy policies designing aimed to combat negative externalities of energy sustainability transitions worldwide, so they might be minimized by properly tailored energy policy in each particular case.

The use of orthogonal components (OS) is the main direction of determining information parameters in microprocessor relay protection and automation of electric power systems. Most of the measuring devices used in modern protection and automation devices can be implemented using known operating systems. Digital non-recursive frequency filters based on discrete Fourier transform are used for OS selection. The main disadvantage of these filters is their low performance that exceeds the period of industrial frequency. For the construction of high-speed measuring devices, this time of establishing the true output signal is often unacceptable. The article proposes to form the equivalent signal OS in microprocessor defenses based on the values of the cosine and sine axes of the main harmonic formed using a discrete Fourier transform, by multiplying them by a correction factor, which is a function of the values of the input signal amplitude and its main harmonic. The proposed algorithm for generating OS input signals in microprocessor defenses is characterized by high performance in transient modes and has wide functionality. A block diagram of an OS equivalent signal generator has been developed, all blocks of which can be implemented according to known schemes on a microelectronic and microprocessor element base. The OS shaper model is implemented in the MatLab-Simulink dynamic modeling environment. The model functioning was checked using two types of test actions, viz. a sinusoidal signal with a frequency of 50 Hz (idealized action) and a signal close to the real secondary current of a short-circuit current transformer. As a result of the performed calculations, a significant (up to two times) in the speed of the proposed method of OS formation in comparison with the formers based on the discrete Fourier transform, frequency properties of both formers being identical.

The analysis of the environmental component of the processes of natural gas burning in atmospheric burners of domestic gas stoves has been carried out. The computational and experimental studies of the harmful substances formation by combustion of natural gas have been performed. The chemical equilibrium of the NO–O₂–NO₂ system was considered. The thermodynamic analysis of transformation of the system during a process of natural gas (methane-air mixture) combustion has been tested. Despite an essential (sometimes – by the order(s)) difference between the thermodynamically equilibrium concentration of the nitrogen oxides [NO_x]_eq and the local, actually measured values [NO_x] = [NO] + [NO₂], the [NO]_eq values could be served as the qualitative indicators of actual values of [NO_x] concentrations. In the combustion processes natural gas and other fuels combustion at high temperatures [NO] >> [NO₂] for both equilibrium and measured concentrations. By moderate and low local temperatures up to 600 K the equilibrium concentration [NO₂]_eq → [NO]_eq in order of magnitude. Under some compositions of burning mixture the correlation could be set as [NO₂] >> [NO], resulting in great danger for the human health. With regard to the formation of particularly toxic NO₂ effluents observed in some cases, an influence of the reaction temperature and the composition of the combustible mixture on the possibility of nitrogen dioxide formation in the combustion products have been analyzed. A methodology for the experimental study of the harmful emissions formation has been proposed while the computerized firing rig has been developed for studying the combustion of hydrocarbon gases in burners of household stoves. An influence of the coefficient of primary air excess on the СО, NO, NO₂ formation has been revealed and the possibility of appearance the emissions of a high concentration of nitrogen dioxide has been demonstrated. 

The authors proposed a model for estimating the heat balance and energy efficiency of a bioreactor that makes possible for a small-sized reactor operating on a relatively low-energy substrate to determine the critical volume, under which the existing climatic conditions allow year-round fully autonomous operation of the digester, as well as for evaluation the potential energy efficiency of such a bioreactor (output commodity heat). For the numerical characteristics of the climatic zone, it is proposed to use the average annual temperature and/or the “degree-day of the heating period” (DDHP) indicator common in construction heat engineering; the DDHP value more adequately characterizing the unevenness of the average monthly temperature distribution, i.e. degree of climate continentality. At the same time, the value of the critical volume of the bioreactor, at which year-round autonomous operation of the digester operating on the municipal sewage sludge, is possible, varies from 7.5 (Vladikavkaz, DDHP = 3410) to 17.0 m3 (Tomsk, DDHP = 6938), i. e. increases almost in proportion to the degree-day of the heating period. It should be noted that when using a substrate with a high biogas yield, e. g., pig manure (a biogas yield of 40 g/kg is adopted), the critical volume in all cases is less than 1 m3. Such results are relevant only for relatively low-energy raw materials. The nature of changes in the output of commodity heat, depending on the volume of the bioreactor and climatic conditions, is quite expectable, viz. the amount of heat that is useful for business interests is higher, the higher is the reactor volume and the milder is the climate. However, when the reactor volume is less than 5 m3, the non-linearity of the graphs is much higher, i. e. for a designer of especially small bioreactors, it seems mandatory to carry out such calculations. The obtained numerical values can be useful both for the designer of bioreactors and for the customer of the project when evaluating the economic efficiency of the planned new innovations.

The results of a numerical study of the gas-dynamic and power characteristics of the exhaust compartment of low-pressure cylinder, including the last stage with a blade of 1100 mm length and the exhaust path, in terms of their interaction are presented. Numerical models of exhaust compartment variants, including steam extraction in front of last stage diaphragm, two steam suctions from the interring gap with a dehumidification chamber, above-band leakages, steam injection from the dehumidification chamber into the diffuser channel have been developed. The flow in each computational subdomain is described by the complete system of non-stationary Reynolds – Favre equations averaged by Navier – Stokes. Turbulent effects are described with the SST Menter model in the stage, and with the modified Spalart – Allmaras turbulence model in the path. The integration of system of equations was carried out using an author’s software package. The calculated subdomains were approximated by hexagonal grids. The solver used an implicit difference TVD-scheme of finite volumes of the 2^nd order of accuracy based on the solution of the Riemann problem. A variant of the algorithm based on splitting the computational process for multiprocessor platforms was used in the calculation. The model of stage used an averaging the mass, momentum and energy fluxes in the circumferential direction in the interstage gap. One channel of the diaphragm with a pre-connected fragment, as well as one channel of the working ring and the flow in the branch pipe were calculated. Parameters were exchanged between the stage and the branch pipe on the basis of mass flow averaging. The calculations were based on a table model of wet steam in the approximation of equilibrium condensation. The variants of improvement of the flow part of the exhaust compartment were considered. A study of the operation of the compartment options for the nominal mode of the K-220-44-2M turbine of the Loviisa nuclear power plant was performed. The effectiveness of lowering the cap of the collecting chamber, controlling the flow using sheet ribs above the diffuser shell, expanding the collecting chamber in the plane of the horizontal connector, and ensuring the release of excess steam from the moisture removal chamber through the tangential slots in the lower half of the convex shell of the diffuser were analyzed.

The article discusses the heat exchange of radiation of bunches of round finned tubes with the environment and the exhaust shaft. The system of equations describing the entire set of primary processes that make up the radiation heat exchange of finned bundles is very complex mathematically; therefore, the calculations of radiant heat transfer are usually based on a number of simplifying assumptions with a involuntarily distortion of the real physical picture. The main methods for calculating radiation used in engineering practice, viz. calculation by the average angular coefficient and the zonal method are briefly considered. A refined zonal method for calculating the radiant component of the heat flow of a horizontal bunch of finned tubes with an exhaust shaft is proposed. An experimental study of single-row bunches of finned tubes with different annular steps S₁ (64 and 70 mm) was carried out for small Reynolds numbers Re = 130–720 in a wide range of the determining temperature at the beam inlet (16–83 °C). The aluminum finning of the bunch tube had the following parameters: screw finning diameter d = 0.0568 m; diameter of the tube at the base d₀ = 0.0264 m; height, step and average fin thickness, respectively, h = 0.0152 m, s = 0.00243 m and Δ = 0.00055 m. Air movement in the bunch was carried out by gravitational traction created by a rectangular exhaust shaft. The experimental bunch was installed above the shaft, and the air was preheated before entering the shaft, which allowed expanding the temperature range of the air at the entrance to the bunch. It was found that incorrect accounting for a bunch reemission with an exhaust shaft when calculating single-row finned bunches causes a decrease in convective heat transfer by 7–25 %.