Materials on the work and achievements of the outstanding Russian scientist Viktor Vasilyevich Elistratov are presented. The main scientific achievements of Professor V.V. Elistratov: on the basis of his methodology for justifying parameters and under his leadership, working projects for the construction of wind power plants (WPP), solar power plants (SPP), small hydroelectric power plants (HPP), reconstruction of small HPPs, as well as power complexes of WPP-HPP, WPP-SPP, WPP-DPP for power supply to consumers in different regions of Russia, remote from centralized networks, were developed; Based on them, a new paradigm for the development of autonomous energy has been formulated - the creation of distributed generation using energy complexes based on traditional and renewable energy sources with intelligent energy distribution and storage systems.

Increasing the thermal efficiency of solar air heaters is critical to the efficient use of energy. This article discusses the issues of research and parametric optimization of convective heat transfer under conditions of turbulent flow in the working chamber of a solar air heater with the absorption of sunlight by the absorber and the air flow from the combustion air ducts. Heat transfer processes and pressure losses are also analyzed and the optimal geometry and location of the air pipeline is determined. In addition, depending on the Reynolds numerical value, it was found that the recommended thermohydraulic coefficient of the concave piping has a higher operating efficiency compared to the solar air heaters given in the research paper. In addition, special attention is paid to the optimal placement of concave ducts; the optimal distances between the ducts are selected. The issues of increasing its heat-transfer capacity are solved by shading the placement of concave ducts. The result is an increase in the performance of the device by increasing the heat transfer coefficient of the collector of a solar air heater with a concave air absorber. For this purpose, the motion of concave tubular absorbers with different geometric arrangements was studied. Also in this article, the heat balance equation was developed to determine the optimal geometric arrangement of air ducts and the reliability of the results was confirmed. In accordance with the simulation carried out, the placement of a concave tube in the form of a checkerboard on the surface of the absorber is calculated perpendicular to the air flow, parallel to the air flow and in the form of a flat air tube.

Agricultural waste, called biomass, is of great interest as a renewable energy source. The purpose of this work was to determine the optimal RR values of the solid digestate when applying a new approach to the intensification of anaerobic conversion, providing a high quality biogas yield. This approach includes solid digestate recirculation and pretreatment a mixture of raw waste and solid digestate in a vortex layer apparatus. For this, the operation of an experimental biogas plant without recirculation and with recirculation was considered, starting from very low RR values, from 0.034 to 1, to ensure a high methane production rate (MPR) and methane yield (MY). From the point of view of MPR and MY, the recirculation ratios of 0.034 and 0.071 look the most attractive, however, with a recirculation ratio of 0.5, the content of hydrogen sulfide de-creased to 14 ppm with a simultaneous increase in MPR by 12% compared to the control.

Transesterification of biomass without pre-extraction is considered as a process for obtaining biodiesel. The transesterification reaction was carried out in the presence of ethyl alcohol and sulfuric acid. The fatty acid composition of the obtained sample was analyzed. The main identified fatty acids were unsaturated fatty acids C18:2 (31.86%) C18:1 (12.79%). The main saturated fatty acid is palmitic acid with 16:0 (12.46%). The characteristics of biodiesel (iodine number, cetane number, density, highest heat of combustion) were calculated, which are consistent with the literature data.

The work is devoted to a comprehensive study of the plant bioelectrochemical systems (BES) properties, including both electrogenic characteristics and monitoring of gas composition changes in the near-electrode areas, as well as photosynthetic, biochemical and morphological parameters of the resulting plant products. Tomatoes and three different growing systems were selected as a test object - using panoponics technology, peat substrate and sodpodzolic sandy loam soil. The BES voltage using a nutrient solution was 35-180 mV, peat – 160-430 mV, soil – 160- 590 mV, depending on the stage of plant development. The carbon dioxide content in the near-electrode areas of the BES was increased on average by more than 5 times. An increase in the amount of hydrogen content by 40% compared to air in peat-based BES was discovered. The presence of compounds with m/z=56 and m/z=64 in the gas component of the near-electrode areas has been identified. It was shown that tomatoes grown in BES with soil had better photosynthetic characteristics and higher yields. Prospects for the use of BES lie in the field of renewable energy, autonomous automated agricultural production and smart agriculture.

                A variant of a hydrogen battery based on electrochemical systems has been studied. Nickel was used as the base, as a material with a greater tendency to absorb hydrogen. Ni_x-В_y-H(D)_z, composites have been synthesized electrochemically, in which, with an increase in the boron content, the solubility of the incorporated hydrogen improves. Boron is a trap for hydrogen atoms in Ni-B electrochemical composites.

                The analysis of data related to the study of the internal friction of pure boron filaments is carried out. The presence of low-temperature peaks of internal friction of boron filaments is shown. The nature of the temperature dependence of internal friction for boron and the temperature dependence of hydrogen extraction from Nix-By-Hz electrochemical systems are compared. The presence of relaxation vibrations in structures containing boron causes the free flow of hydrogen from these systems at room temperature. An increase in the concentration of boron in the system should lead to an increase in the magnitude of the peak of internal friction and to its displacement to a region of lower temperatures, unlike pure nickel.

                In the presence of boron, the hydrogen permeability of nickel is reduced, since tensile stresses occur in the vicinity of the substitution impurity of a small atomic radius – boron embedded in the FCC lattice of nickel. Hydrogen accumulates near boron to a greater extent than near nickel. The interaction potential of a hydrogen atom with an impurity trap, a boron atom, is estimated at 0.42 eV.

The influence of boron concentration on the structure of nickel-boron-hydrogen composites is substantiated. An increase in the concentration of the alloying component boron in nickel increases the dispersion, leads to the alignment of the surface profile and the formation of structures of the nanoscale range.

                The results of studies of the kinetics of hydrogen desorption from Ni-B electrochemical composites are presented. The hydrogen content in Ni_x-B_y-H_z samples (9 at. % boron), measured by the vacuum extraction method, was 600 cm³ /100 g, which is significantly higher than the corresponding value for electrochemical nickel ~100 cm³ /100 g.

                The spectra of thermal desorption of deuterium from Ni–B composites pre-implanted with various doses of deuterium ions at T~100 K have been studied. It has been established that the structure of the deuterium thermal desorption spectrum is a function of the implantation dose. The deuterium content for nickel corresponds to the ratio Ni:D = 1:1, and for the composite Ni₉₅B₅ [Ni₉₅:B₅] :D = 1:1,25. For nickel, a clearly defined peak is formed with a maximum temperature of 325 K. For the Ni–B composite, the thermal desorption spectrum has a blurred peak with a maximum temperature of 325 K and a deuterium desorption region in the temperature range of 250-500 K.

The article reflects the history of the development of energy-efficient technologies that allow the use of renewable energy sources in the heat supply systems of buildings. A number of significant events for this direction are described in chronological order, priority ways to improve the efficiency of power generating equipment are indicated. The need for scientific understanding in the historical aspect of the development and formation of heat pump (cooling) systems is due not only to the increased interest in this field of science and technology, but also to the results of a comparative analysis of general trends in world development and the identification of specific features of the development of research, taking into account the characteristics of their evolutionary, ethnic, geographical , natural and climatic conditions. The authors carried out a statistical analysis of the Russian scientific citation database with an advanced search for "heat pump systems", "heat pump", "air heat pump". The number of scientific publications, including patents, for the period from 1900 to 2022 is revealed. The author's vision of further prospects for the development of built-in heat pump technologies for space heating in Russia is also presented.

The development of net-zero emission fuels is a priority area of modern research due to the imminent reduction of fossil fuel reserves and environmental problems caused by their combustion. One of the promising fuels is hydrogen, which has a high heat of combustion and forms water as the only product of combustion. Recently, methods of hydrogen production by microorganisms, which use directly the solar energy or utilize the organic waste during fermentation, have been intensively developed and applied. In this review, the basic principles of the main light-dependent (biophotolysis, photofermentation) and light-independent (dark fermentation and microbial electrolysis) methods of biological hydrogen production are discussed. Particular attention is paid to the advantages and disadvantages of these methods, the possibility of combining them into a single system, as well as various strategies for improving biohydrogen production aimed at transition from laboratory research to full-scale application.

The main research problems reflecting the process of obtaining modern electrochemical coatings are considered, the directions of step-by-step study of the parameters of the electrochemical process in order to obtain the most important physical and mechanical properties of coatings are shown. It is shown that, in the process of synthesis of coatings with specified properties using differentially correlated and variable parameters (applied electrolyte compositions, electrolysis modes, and the nature of boron-containing reducing agent), it is possible to synthesize Ni-B composites that differ in their boron content and related physical and mechanical characteristics. The Ni-B electrochemical system made it possible to demonstrate the possibilities of regulating and controlling the coating by composition and properties, to determine the technological parameters of the processes for obtaining composites with the required operational properties necessary for wide application in various industries.

It is shown that the plane-parallel motion of a gas in a potential field is described using shock adiabatics, and if the stationary gas flow in the field is accompanied by compression, then the entropy increases. The reverse process of gas expansion in a potential field is accompanied by a decrease in entropy. This explains the low efficiency of centrifugal gas compressors and the high efficiency of turbines (expanders) with radial gas motion in the field of a non-inertial (rotating) reference frame. The excessive conversion of internal gas energy into kinetic energy during centripetal motion in a vortex can explain the stability of natural vortices, such as tornadoes, cyclones and cosmic jets.

The article analyzes materials on water-soluble gases (VGGS), their physico-chemical parameters, territorial distribution and saturation intensity, taking into account the depth of immersion within Azerbaijan, in particular, the South Caspian mega base. The high industrial suitability of the VRG was particularly noted. Despite the fact that Azerbaijan has large reserves of oil and especially gas, they still tend to be depleted. At the same time, the ENEMY can play the role of an environmentally very clean and turning from an alternative to the main fuel.