At present, as the demand for electricity increases in all sectors, there is an urgent need to introduce alternative renewable energy sources into modern energy systems. Renewable energy sources, which consist of solar (photovoltaic, PV), wind and hydro power, are key alternative sources of green «energy.» energies. Thanks to scientific and technological progress, the cost of photovoltaic solar radiation converters is constantly decreasing at a high rate, which makes it possible to build solar power plants of sufficiently large capacity. In the coming decades, solar energy will become an incentive for the economic development of countries that have the maximum "solar" resource. The Republic of Tajikistan is one of these countries with a high potential for solar energy.

The article presents an analysis of the resources and potential of solar energy in the Republic of Tajikistan. The study of electromagnetic transients in networks with photovoltaic solar power plants is performed. The main equations, simulation model and calculations of transients are presented, taking into account changes in voltage on DC buses. An algorithm for controlling the system of automatic control of output parameters is proposed. The analysis of dynamic and static modes in parallel operation of a solar power plant with the grid is carried out. A block diagram and computer model is constructed in the MATLAB package together with Simulink and Power System Blockset.

The concept of mixed refrigerant fluids has emerged during the past few decades from 20th century due to its superior thermophysical properties as compared to base fluids. It is primarily used as coolants in heat transfer equipment such as heat exchangers and thermoelectric cooling systems. In the current study, an analysis of the physicalthermodynamic properties and the different parameters was performed by considering 10gms of mixed refrigerant of propane and ISO-butane at different compositions ratio. All results presented for simulations carried out at range temperature about 300-350K and a pressure range of 3MPa to 7MPa. They concluded from the result that as the temperature increases specific heat of mixed refrigerant decreases. Similarly, thermal conductivity increases with an increase in temperature for a mixed refrigerant at different compositions. Further, as the pressure is varied from 3MPa to 7MPa while keeping the temperature constant at 350K, the specific heat decreases by 5.2% as well as thermal conductivity follows the opposite trend and is increased by 6.9%.

Russia’s sources of electricity generation have been mainly from fossil fuels duel to the country’s abundant hydrocarbon resources, and nuclear power plants. The country has huge renewable energy potentials which are yet to be fully developed. This study evaluated the techno-economic potential of a PV/Wind/DG/Battery system for integration in Yekaterinburg and other rural areas around that enclave. The Hybrid Optimization of Multiple Energy Resources software was used in the simulation of the system, some financial metrics such as levelized cost of energy (LCOE) and the net present cost (NPC) were used in the analysis. Results from the monthly electricity generation indicate that a total of 75,469 kWh/year of electricity was produced from the hybrid system. The PV system produced 29,405 kWh/year representing 39% of the total electricity generated in a year. The wind system also produced 23,291 kWh/year which also represent 30.9% of the total electricity generated per annum, whiles the DG system produced some 22,773 kWh/year representing 30.1% of the total electricity generated by the hybrid system. An excess electricity of 2,353 kWh/year was generated which represents about 3.12% of the entire annual generated electricity. The system recorded an LCOE of 0.356 $/kWh, NPC of $255,478.80 and an operating cost (OC) of $9,409.72. The obtained results will be too expensive if implemented using the selected financial conditions. However, a sensitivity analysis conducted indicates that the cost of energy can be significantly reduced if some selected financial variables are changed.

Obtaining drinking water in areas where water resources (even contaminated or salty water) are completely lacking is an extremely important and complex problem. At the same time, there is always a certain amount of water vapor in the air present everywhere. The Earth's atmosphere contains a good amount of water vapor in addition to dry gases such as oxygen, nitrogen, carbon dioxide, etc. Water vapor constitutes 3% of the air mass by 4% in volume and the rest are dry gases.

However, known methods of obtaining fresh water from air vapors are extremely low-efficiency, difficult to implement and have not been widely used in practice in recent years.

At the same time, climatological studies indicate that the maximum amount of water vapor appears in the air at night, but the natural rate of their condensation is extremely low. Condensation efficiency can be significantly improved by artificial cooling techniques, which requires an external source of energy. There is a way to get the required energy from renewable sources (e.g. the sun) during the day and accumulate it for use during the night in refrigerated condensation systems.

The current study included experimental results for economical method to get a potable water, especially in areas without any the water source, such as the desert by using the air humidity condensing technique through vapor compression refrigeration -photovoltaic system. The results of the experimental study showed that the compression refrigeration – photovoltaic model produces about than 6.5 liters of freshwater per day, while consuming 0.7 kW*h/l of energy.

The results are ten times higher than the efficiency of natural (convective) water extraction processes and have lower energy costs than for obtaining fresh water by thermal distillation of 0.72 kWh/l from seawater.

The role of nuclear energy in environmental problems solving is substantiated. The energy sources with the lowest emission of CO₂ are given accounting the emission throughout the whole life cycle of the energy source (hydroelectric, nuclear and wind power plants). The advantage nuclear power plants possess over these energy sources is substantiated. The data on the state of nuclear energy at present are given. The general problems are formulated of up-todate nuclear energy using the overwhelming majority of thermal neutron reactors. The requirements to promising nuclear energy of the XXI century are summarized. The information is provided on the GIF – the Generation IV International Forum which was created in 2001. Two main ways of spent nuclear fuel (SNF) treatment are described. The single-phase cycle, the so-called open nuclear fuel cycle, implies the single use of nuclear fuel and the subsequent storage of it as waste products. The recycling of nuclear fuel is called closed fuel cycle and implies the return of unutilized uranium and accumulated plutonium into the cycle. The possibility of application of fast neutron reactors with sodium coolant as a part of the fourth generation nuclear energy systems in solving the problems of fuel supply and minimizing of the radioactive waste amount has been assessed. The data are given on the two-component structure of power system with thermal and fast neutron reactors combined by the closed fuel cycle which can provide the solution of general problems of the nuclear energy such as SNF accumulation and radioactive waste treatment, and supply the cardinal increase of the natural uranium use efficiency. The results of the analysis of the impact of nuclear power plants with BN-600 and BN-800 reactors on the environment and personnel are summarized. The possible variants of layout of fast neutron reactors with sodium coolant are presented. The advantage of pool type is substantiated from the point of view of safety increase. Given are the main characteristics of the BN-1200 reactor which ensure safety, low-waste operation, absence of limitations on raw material supplies for a long period of time. The design features of fast sodium reactors which ensure its high safety for personnel and environment are described.

It is emphasized the absolute need of ensuring the safety of personnel and the public when using nuclear energy. The importance of creation of effective protection against ionizing radiation is substantiated. It is shown the significance of the optimization principle being one of the basic principles of radiation safety, in designing the composition of biological protection. The requirements for the materials used for the construction of protection are given. It is substantiated the relevance of studies of the local minerals properties in order to estimate the possibility of their use as part of the biological protection of nuclear facilities (NIAE) constructed in different countries. Given are the main directions of research of the radiation protection optimization which are carried out by specialists of the «Nuclear Power Plants and RES» department of UrFU. One of these directions is the computational and experimental study and optimization of the composition of radiation protective materials which are adapted to the specific isotopic composition of radioactive contaminants in the NIAE systems. As an example, the article presents the results of computational and experimental studies of the properties of basalts from the deposits of the Republic of Egypt in order to estimate the possibility of their use in building materials for construction of protection against ionizing radiation.

The origin of the studied basalt samples is described. The characteristics of basalt (the form of basalt bed, arrangement of stratums, their dimensions) of different deposits of Egypt are presented. The equipment and the technique of chemical analysis of the basalt samples are described. The results of the analysis of chemical composition and spectrometric analysis of the specific activities of natural radioactive impurities (thorium, potassium-40, radium) in basalt samples are presented. The equipment and the technique of experimental study of the basalt samples radiation protective characteristics are described. The substantiation is given for the choice of radioactive isotopes for the experimental investigation of the basalt samples. The results of mass attenuation coefficients determination for the samples of basalt and lead (as a reference material) with the help of scintillating detector NaI(Tl) are given. The results of experimental studies of linear and mass attenuation coefficients of γ-radiation of Cs-137, Co-60 and Eu-152 isotopes by basalt samples are presented. The experimental data are compared with the calculated ones obtained with XCOM program.

When mixed organic waste is used for hydrogen production by dark fermentation, the microbial community which is most adapted to actual biopolymer composition of the substrate, is auto-selected. In this research, 6 substrates simulating different biopolymers (proteins, fats, carbohydrates) and their mixtures were used to enrich hydrogenproducing bacteria adapted to these substrates from non-pretreated activated sludge. Phylum Firmicutes dominated in the microbial community (67-100%) regardless of the substrate used, as was shown by high-throughput sequencing. Microbial diversity was low when using carbohydrate-rich substrates, and microbial community was mainly represented by Ruminococcus (26-90%) and Thermoanaerobacterium (6-67%). Dark fermentation of fats and proteins was characterized by higher microbial diversity. Thermoanaerobacterium (21%), Thermobrachium (19%), Tepidiphilus (16%) and Acetomicrobium (14%) dominated when using fats, while Thermobrachium (34%), Acetomicrobium (16%) and Clostridium sensu stricto 7 (12%) dominated when using proteins as substrate. Different microbial communities and substrates resulted in diverse process performance and metabolic pathway. Dark fermentation of starch achieved the maximum hydrogen yield of 138 ml/g volatile solids with 60.4 % hydrogen content in biogas. The dominance of genus Ruminococcus was supposed to be responsible for the highest hydrogen production. Minor amounts of methane from proteins and fats were produced by Methanothermobacter and Methanosarcina. The hydrogenotrophic pathway was slightly more predominant methane formation route than the others considered based upon to the stable ¹³C isotope analysis.

The article discusses the features of the main characteristics of wind speed in the territory of the Syunik marz of the Republic of Armenia; the statistical characteristics of the wind are obtained. For analysis, we used the data of the Hydrometservice of the Republic of Armenia for a period of 50 years and more (1966-2018) at 7 weather stations. An analysis of the spatial change in the characteristics of the wind speed showed a variety due to the roughness of the terrain, where the terrain has a great influence on the distribution of wind speed characteristics.

Based on the statistical analyses, the norms of monthly and annual wind speeds are determined; the spatial and temporal variability of their studied characteristics is analyzed. To calculate the annual value of the wind speed of unexplored areas, correlation dependencies between the value of wind speed and elevation are obtained. Built a map of the distribution of the annual value of the wind speed.

The performed analysis of the spatial variation of the velocity characteristics wind regime showed a variety due to the ruggedness areas where the relief has a great influence on the distribution wind speed characteristics. Average annual wind speed at the study area ranges from 1.1 to 7.7 m/s: the largest average wind speeds are observed at Sisian and Vorotan passes, especially in summer, the lowest average wind speeds are in Meghri, especially in autumn and winter. The wind speed increases with height. Vertical the gradient of the average annual wind speed in the lower zone is –0.25 m/s / 100 m, and in the upper zone - 0.75 m/s / 100 m. On the territory of Syunik the diurnal variation of the wind speed is well pronounced, and the annual variation differs ambiguous patterns. In Syunik marz, the wind speed is during the day it grows in the daytime and maximum in the warm afternoon time, and from midnight to early morning, the wind speed decreases and reaches a minimum.

To assess the dynamics of changes in wind speed, three periods were allocated (1966-1985, 1986-2000, 2001-2018). Both by months and by year there is a non-uniform dynamics of changes in the average values of the speed wind.

The results can be used in planning the development of wind energy in the Syunik marz, the development of wind energy cadasters of territories, climate services for sectors of the economy, adjustment of building standards.

In the lithosphere of the planet is a large amount of hydrogen associated with other chemical elements. When extracted for industrial use and when interacting with atmospheric oxygen, these compounds form water. A typical example of such substances is hydrocarbon compounds, widely used in modern energy as fuel. The resulting water vapors are an additional source of fresh water extracted from geological formations. However, the lack of technology to capture these fumes now leads to additional hydration of the atmosphere, which contributes to the development of the planet's greenhouse effect.

In the work on the basis of the analysis of combustion reactions, stoichiometric air energy fuels (petrol, diesel, gaseous fuels, wood) and artificial, converted from biomass and coal fuels (ethanol, methanol, butanol, and so on), and also hydrogen fuel. Compare the relative air consumption and water vapors emissions in combustion products.

The process determined by the properties of constructional materials of modern achievements of engine (1400° С) defines ratios of excess air for different types of fuels, the real consumption of the air, fuel and water vapor emissions.

Theoretically, the high consumption of atmospheric air using hydrogen and gas fuel is shown, the lowest in traditional motor fuels (gasoline, diesel).

The useful use of organic fuel and hydrogen oxidation products for fresh water is justified - the development of technologies to efficiently extract water vapor from gas combustion products (oxidation) of energy fuels can contribute to the creation of an additional large source of fresh water commensurate with other natural sources and will contribute to the energy and environmental efficiency of traditional energy facilities.

The information presented in the work of technique analysis is universal and can be used in the analysis of any existing or newly created fuel compositions.

The research area is electric drives for agricultural vehicles. Often, small farms use transport that is not commensurate with needs, as a rule, for personal movement, transportation of small cargoes, heavy equipment or products, the same vehicle is used, purchased on the principle of transportation of the possible heaviest cargo, even if it is is extremely rare. It is proposed to use an electric vehicle powered by rechargeable batteries for personal movement and transportation of small loads. The article describes the battery charging system, which was developed and implemented on the basis of an experimental model of the Oka-E electric vehicle. This system is exclusive, since the proposed voltage level of storage batteries does not correspond to well-known foreign and domestic counterparts and is combined with the installed electronic-conversion equipment available on the Russian market. A kinematic diagram for an electric vehicle for agricultural purposes was developed and calculated, according to which the gasoline engine was dismantled and a standard asynchronous electric motor was installed, connected to the clutch unit and the original gearbox. A new control system for the frequency-converting device has been developed and manufactured, while maintaining the controls familiar to the driver. An algorithm for charging traction batteries has been determined, an electrical circuit of a charger for batteries of an electric vehicle has been developed. Their capacity was calculated in accordance with the technical parameters of the electric vehicle. Comparison of rechargeable batteries and their selection is made. Experimental research on charging a storage battery with the developed charger has been carried out, sea trials have been carried out. The main advantages of the proposed electric vehicle are low operating costs associated with cheap maintenance of the mechanical part, a high degree of reliability of the power unit and electronic conversion devices, low cost of electricity, which can be obtained from its own solar power plant or centralized power supply using the night tariff. The main consumers can be farmers, livestock specialists, agronomists, postmen and other employees.

Vibrations of equipment and pipelines are an existing factor determining the power plants’ elements and pipelines failure. About half of all disturbances in the operation of pipelines are caused precisely by vibration. One of the reasons for its appearance is the interaction of the transported flow with the walls of the pipeline. In this case a device that dampens vibration, or preventing it may be a solution. The swirl inserts considered in this work for pipelines with a two-phase flow prevent the occurrence of vibration due to a more uniform distribution of phases along the cross section and length of the pipe. The experimental inserts were modeled in the SolidWorks CAD software package for 3d printing, as well as for preliminary tests in the field of computer modeling. Computer simulation of a single-phase fluid flow was performed using the Flow Simulation module. The result of the work is an insert for testing on a hydrodynamic bench created on a 3D printer. According to the results that will be subsequently obtained experimentally at the stand, it will be possible to judge the efficiency of the vortex, the probability of the current tearing off the insert wall and the resulting resistance, which is also important for a pipeline with two-phase media due to interphase transitions.

Modeling of inserts with various groove guides was performed. Using a 3D printer, prototypes were printed, with the help of which a primary analysis of the effectiveness of an insert with a specific geometry on an experimental bench is possible.