The article presents the results of the study of the nature of the change in the graph of the wall temperature dependence on the heat flux density. The results of these studies have shown that the double occurrence of intensification of the heat transfer process is characteristic of hydrocarbons and the latter does not depend on the direction of fluid movement and the position of the experimental tube.

As a result of the analysis of the graphs, it was established that, regardless of the values of the mass velocity, the course of the temperature curve changes several times and, in this case, the intensification of the heat exchange process occurs twice. The onset of the first improved heat transfer mode at lower values of the mass velocity corresponds to a lower value of the heat flux density. The onset of the second improved heat exchange in experiments with n-heptane during upward motion at different mass velocities corresponds to the same value of the heat flux density.

When analyzing experimental data obtained during the downward movement of n-heptane, it was established that heat transfer during the upward movement is accompanied by an additional sound effect – fluctuations in liquid pressure and wall temperature.

This study proposes a planar mirror-based method to enhance irradiance on photovoltaic (PV) modules, aiming to improve energy output efficiency through geometric-optical optimization. The dynamic effects of critical parameters – including mirror rotation angle (θ = 15°-85°), mirror-to-PV distance (r = 1-10 m), and reflective area (A = 1-5 m²) – on the spatial distribution of effective irradiance were systematically investigated. Experimental results demonstrate that under optimal configurations (θ = 75° ± 5°, r =3,2-4,1 m), an irradiance gain of approximately 12,7% is achievable. This work provides a reference framework for designing low-complexity reflective enhancement systems tailored to PV applications.

The production and accumulation of various organic wastes increases annually, posing a threat to humanity and the environment: wastes ending up in landfills produce climate-active gases and are filtered into soil and water basins. Anaerobic digestion is a well-known method of biological conversion of organic wastes from livestock complexes. Twostage anaerobic digestion (TAD) with the production of hydrogenand methane-containing biogas, respectively, in the first (dark fermentation) and second (methanogenic) reactors is a promising technology for more complete material and energy conversion of organic matter in wastes. Although TAD is not a new process, information on the process stability and effective operating conditions is limited and often contradictory. In this paper, the effect of carbon cloth as a biomass carrier material on the efficiency of thermophilic methanogenesis of the liquid fraction of dark fermentation effluent during the processing of a model of organic wastes from the agro-industrial complex during the system startup period was studied. The organic matter load in the dark fermentation (DF) reactor was constant (24 g VS/(l day)), while in the methanogenic anaerobic biofilters it was varied by changing the hydraulic retention time (HRT) accordingly from 1,6 to 3,2 days. The average COD content in the influent of anaerobic biofilters was 7400 mg COD/l. On average, the hydrogen production rate of 1,35 l/(l day) and the hydrogen yield of 56,2 ml/g VS were achieved at a hydrogen content in biogas of 47,9% and a pH in the DF reactor of 4,22. The carbon cloth contributed to an increase in the methane yield during the start-up period and made it possible to increase the volumetric methane yield by an average of 25% at steady-state modes at HRT of 3,2 and 2 days. At HRT of 1,6 days, the methane production rate was 70% higher in the reactor with the carbon cloth, however, both reactors operated unstably. It should be noted that anaerobic biofilters used the liquid fraction of dark fermentation effluent as an influent, which is a complex substrate due to its low pH.

Hydrogen energy is a promising area of energy sector. According to forecasts, global demand of hydrogen will increase six times and reach 700 million tons per year by 2050. At the same time, modern environmental policy imposes restrictions on industrial processes, including hydrogen production, which necessitates the transition from traditional methods of hydrogen production from hydrocarbons to low-carbon and carbon-free technologies. In this paper, a comparative analysis of traditional (steam methane reforming, coal gasification) and alternative (plasma methane pyrolysis, water electrolysis) hydrogen production technologies on a number of criteria (technological, physicochemical, environmental, energetic and economic), to determine the prospects for their use under low-carbon development strategy.

The ever-increasing demand for energy in remote areas and hard-to-reach territories requires sustainable and reliable solutions for electricity and heat supply. At the moment, there is a partial transition to decentralized energy production, which makes it possible to create local intelligent energy systems. These systems are located in close proximity to the consumption nodes, which increases the reliability of the power supply. The hybrid system presented in the study includes a gas turbine, wind turbines, solar panels, a fuel cell, and an electrolyzer. The system efficiently converts excess wind and solar energy into hydrogen during off-peak operating conditions and uses the resulting hydrogen in a gas turbine and fuel cell during periods of demand. The aim of the study is to develop a concept for creating a hydrogen neighborhood through the effective use of hydrogen technologies in the production of electricity as part of hybrid systems. The paper considers the strategy of electricity and heat supply in a neighborhood with a population of about 6,000 people. The strategies of electricity and heat supply are presented, taking into account the actual energy consumption indicators (hourly load schedules). The presented concept of hybrid technology development considers the use of Russian equipment during implementation. The presence of manufacturing plants producing the entire range of equipment for creating hybrid systems allows not only to implement pilot projects of residential districts, but also to develop a long-term program for the creation of such residential districts in remote areas of the Russian Federation.

The article describes the types of pipelines and methods of their installation. It has been established that it is advisable to use metal pipelines for transporting hydrocarbons and hydrogen. The possible types of corrosion of steel pipelines are described: soil corrosion, atmospheric corrosion, marine corrosion, chemical corrosion, stress corrosion cracking. The mechanism of hydrogen embrittlement of steel pipelines is studied. The methods of protection against corrosion of steel pipelines are presented, including electrochemical protection, organic and inorganic coatings. It has been established that inorganic silicate-enamel coating better protects pipelines from corrosion, since it has high chemical resistance and mechanical strength. Possible ways to increase the durability of silicate-enamel coating are described. The use of a single-layer enamel coating, as well as a decrease in the water content in the slip or the replacement of the slip enameling method with powder enameling reduces the hydrogen content in the silicate-enamel coating. Possible corrosion-resistant additives for silicate-enamel coating are shown.

The problems of changing the operating modes of the main technological equipment of compressor stations (CS) of the existing gas transmission system, as well as the degradation of the mechanical properties of the CS equipment material in the case of transportation of methane-hydrogen mixtures or hydrogen at elevated pressure, are considered. The features of operation of a centrifugal compressor during pipeline transportation of hydrogen-containing mixtures are considered. Due to the peculiarities of the physico-chemical properties of hydrogen, which lead to an increase in the flow rate, an increase in the rotational speed of the compressor rotor is required, which is limited by regulatory requirements. When used with hydrogen-containing mixtures, the risk of embrittlement of the rotor material increases. The results of tests to assess the resistance to hydrogen embrittlement of structural steels of different classes, which are characteristic materials of CS equipment, are presented. The main patterns of changes in strength, ductility, and crack resistance of steels at hydrogen concentrations from 5% to 100% and pressures of 10 MPa have been established. In a hydrogencontaining environment, high-strength steels are softened and strongly embrittled.

Coal-fired power generation accounts for 36% of the world’s thermal and electrical energy production in 2023. In the Russian Federation, coal-based generation is about 18%. In the long term, until 2050, coal will remain one of the main energy sources both in Russia and around the world, despite its decline in the global fuel balance compared to 2020 and an increase in the share of renewables.

Compared to natural gas and fuel oil, coal is the cheapest source of energy, while coal-fired thermal power plants, emitting nitrogen and sulfur oxides, greenhouse gases together with ash particles into the atmosphere, polluting underground water and resulting in soil degradation, are the least environmentally friendly of all traditional power plants.

In the USA, EU and other industrially developed countries, the coal ash utilization level is more than 60%. In Russia, the beneficial use of the coal ash is about 19% of the volume of its production. This is due to the use of wet coal ash removal systems at power plants and the storage of the coal ash in the form of an ash and slag mixture and, in general, the lack of the comprehensive approach in the field of coal ash handling problem. The largest countries producing coal combustion by-products are China, India, Europe and the USA. In India, coal ash utilization is 100%, in China – 60%. In 15 countries of the European Union (EU-15), the highest level of the coal ash use makes 120%; this figure means that more coal combustion by-products are processed than produced. In different countries, the coal ash is mainly used in the production of cement and concrete, which primarily applies to siliceous ash. Calcareous ash is mainly used both for backfilling of the worked-out mines and as a binder, given its hydraulic properties. Every year, coal-fired thermal power plants and boiler houses in Russia generate 19-25 million tons of the coal ash, and this figure is growing every year. Today, above 1,5 billion tons of the coal ash have been accumulated in the disposal sites of thermal power plants. About 2/3 of all the ash dumps are close to the design filling or are already overflowing. The problem of eliminating objects of accumulated environmental damage, which are coal ash dumps, can be only solved by implementing large-scale projects for the comprehensive coal ash processing in order to receive the in-demand products. The article presents the author’s proposals for improving the regulatory framework to increase the coal ash utilization level, which concern strategic industry planning, the development of new standards for the coal ash processing products, adjusting existing standards in terms of terminology, and finalizing other regulatory legal acts. The article shows an incentive mechanism in order to raise the interest of the ash producers in increasing the coal ash utilization volumes to achieve key indicators regarding the coal ash use in the amount of 50% by 2035 as specified in the Energy Strategy of Russia until 2035. An algorithm of actions is proposed for the implementation of an integrated approach in the field of the coal ash handling to maximize the coal ash usage in the production processes of the Russian enterprises.

The article provides an overview of the natural prerequisites for the formation and use of renewable energy resources in the region: seas (waves, currents, tides), rivers, thermal groundwater. It is shown that the resources of the Arctic seas are not suitable for development in the foreseeable future due to ice content and low tide height. The resources of the Pacific seas may be available for development with global warming to average annual atmospheric temperatures on the sea coasts above 0 0C. Damless power plants are the most environmentally safe. Renewable energy of rivers is promising for expanding the base of «green» energy in mountainous areas. Significant seasonal fluctuations in flow make large areas of reservoirs corresponding to the capacity of hydroelectric power plants necessary. At the same time, the areas of valley taliks – oases of life in the region of continuous cryolithozone – are flooded, and the conditions for the reproduction of fish resources in the lower pools are negatively changing. The current global warming may lead to an increase in the energy resource of rivers by 2050 by approximately 14%.

The energy of underground waters with temperatures above 70 0C, Anadyr and Khatyr artesian basins are promising for ensuring the operation of local binary power plants. Climate warming does not affect the characteristics of thermal waters.

The article provides data on climate changes on the planet and their consequences. The natural and anthropogenic factors influencing climate change are analyzed. The issues related to the influence of natural engineering systems (NES) on environmental pollution are considered. Wind farms and buildings and structures made of cross laminated timber (CLT) are considered as NES. The application of integrated environmental indicators for the assessment of environmental pollution during the life cycle of NES is considered.

The article is dedicated to the 80th anniversary of the Doctor of Technical Sciences, Professor, Academician of the Russian Academy of Sciences Fedorov Mikhail Petrovich.

The article reflects the results of historical analysis of the formation and development of bioenergy at the St. Petersburg Polytechnic University (SPbPU). The key stages of the scientific direction’s evolution are considered, from the first studies in bioenergy to the current state, as well as the role of the university in the development of bioenergy technologies. Special attention is given to the contributions of SPbPU scientists in the study and utilization of renewable energy sources, such as biogas, biohydrogen, and biomass. Based on the analysis of archival materials and scientific publications, the major achievements and trends in the development of bioenergy at the university are identified, along with the impact of these studies on the advancement of Russian and global science in this field. The work aims to systematize the scientific legacy of SPbPU in the field of bioenergy and assess the university’s significance in shaping an interdisciplinary approach to solving energy and environmental challenges.