Designing of DC-DC converters with optimal parameters is a challenging task.

The theoretical part of the paper shows a schematic circuit of the power part of the bridge DC-DC converters under consideration, and describes the operating principle of the power part of the DC-DC converter with a series resonant inverter for solar power plants. With the help of timing diagrams, the features of the symmetrical and asymmetrical control of the power transistors of the converter are explained, and the characteristics that allow comparing the two control methods are explained.

To DC-DC converter control, there are many analogue controllers on serial chips, but they are intended only for implementing symmetrical control. Thus the paper proposes the scheme of algorithm of the asymmetrical transistors control in a series resonant inverter in the form of a virtual model in Matlab-Simulink environment. A few foreign studies currently describe an asymmetrical control method, with only current waveforms of the resonant circuit and control voltages on the gates of the converter’s MOSFET transistors, as well as a block diagram of the control system. Therefore, the algorithm of asymmetrical control described in this paper is original, and the results of the research are new in comparison with existing world practices.

The experimental part of the paper presents the simulation results (transient, steady-state, external characteristics, dependencies for converter’s efficiency). The obtained characteristics agree with the results of theoretical calculations shown in previous papers of the authors. 

The paper describes and demonstrates the electro-thermal de-icing system using the thermal conductivity effect in solids and designed to remove snow and ice from the front surface of the solar panel both at low temperatures (below zero degrees centigrades) and heavy mixed precipitations. We show the known and being developed alternative approaches for cleaning the operating surface of solar panels from ice and snow and considered the significant need for the proposed system application. The location and functions of key components of the presented de-icing system are practically optimized to increase the efficiency in case of precipitation fallout on its front surface. The design of the multilayer structure of de-icing system is shown and described in details. We present a computer simulation model with building graphs with showing the efficiency of the proposed electro-thermal system in various environmental conditions. We also demonstrate the successful experimental field testing data of operating electro-thermal de-icing system of solar panel in South Ural climatic conditions. We also show that the electro-thermal de-icing system of solar panel powered from batteries, may increase the time of uninterrupted operation of solar panel during the mixed precipitations.

The article provides information on the volumes, markets and manufacturers of the wind power industry. The statistics on the total installed wind power in the period from 2012 to 2016 are considered – according to the results of the analysis at the end of 2016, the world wind power reached the value of 500 GW. The rating of the countries is based on the installed wind capacity, where China has been the leader for the last few years. A global analysis of continental regions based on installed wind power for 2000-2015 is presented. On the example of the leading countries in the field of wind power as the successful practices of implementing wind energy projects, the concept of “public energy” and how citizens (individuals) can own and manage local wind power facilities are considered. As the statistics have shown, public energy projects can become a link in the local infrastructure and contribute to the overall economic development of the territory, while foreign or foreign investors are less likely to successfully implement wind energy projects compared to unified citizens. It is worth noting that such public energy infrastructure projects generate more tax revenue for the region than projects that are created at the regional or country level. The risks and possible ways of their reduction are indicated in the development of wind power projects and in the following operation of the facilities. The influence of the created projects in the field of wind energy on the number of jobs in the regions is described. The most optimal levers and instruments that can involve states as an incentive for the use of renewable energy sources are considered.

The paper studies the features of biomass energy use and presents the main directions of biogas application. It is shown the connection between the main indicators of biogas quality and the possibility of its use in various technological processes. The relevance of improving the quality of biomethane used for synthesis of high purity hydrogen is substantiated. The classification of the methods for separation and purification of methane-containing gas mixtures is given, their advantages and disadvantages are analyzed. Comparative characteristics of the presented methods for cleaning quality, specific energy costs, and design features are given. A method of short cycle free adsorption for bio-gas purification is proposed as the most economically feasible for small capacity plants. The main types of industrial adsorbents are considered. The dependence of sorption properties on the effective pore diameters of sorbent materials is shown. The distinctive features of adsorption in microporous structures are noted. The most significant of these features is the high value of the adsorption energy in comparison with adsorption materials having larger pores in the structure. Among microporous adsorbents, zeolites are identified as the most promising. The adsorption properties of synthetic and natural zeolites are analyzed. The theoretical bases of the adsorption purification processes are considered, the adsorption competition of the main macrocomponents of the gas mixture being cleaned is evaluated. The scheme of the experimental installation and the process of separation and purification of biogas using natural zeolite as an adsorbent are described. The results of application of a natural zeolite for the production of high purity biomethane due to purification from water vapor, hydrogen sulphide and adsorption of carbon dioxide are presented. The conversion of biomethane to hydrogen was noted as the most promising direction of biomass energy use, the advantages of using natural zeolites for obtaining high purity biomethane are shown.

Interaction of the intermetallic compound CeCo3 with hydrogen (pressure of 25 atm) and ammonia (pressure of 6– 8 atm) is investigated at temperatures of 20–450 ºC: the composition of products is established, formation conditions of the hydride and nitride phases are determined. Dependence of a direction of intermetallide reaction with the ammonia, passing in presence of NH₄Cl (10 wt. % from quantity of intermetallic compound) as activator, from temperature is shown. Formation of hydride phase CeCo₃H₄ is established at hydrogenation of the intermetallide CeCo₃ with both hydrogen and ammonia at heating to 100 ºC. The treatment of an initial alloy with ammonia at temperatures to 250 ºC also ends by formation of tetrahydride CeCo₃H₄. Ammonia use as hydrogenating agent in such conditions leads to dispergation of an initial alloy that it is confirmed by increase in a specific surface area of a product with 5.7 to 18.4 m²/g at hydrogenation temperature of 100 and 250 ºC accordingly. At that calculated average size of particles makes ~1 and ~0.3 micron accordingly. The value of a specific surface area of the product received after carrying out of 5 cycles sorption-desorption at use of hydrogen made only 0.3 m²/g, that testifies to clear advantages of ammonia application for dispergation. In the conditions of the further temperature treatment (300–350 ºC) ammonia causes amorphization of an alloy. It is established, that at intermetallide heating in ammonia atmosphere in temperature area of 400–450 ºC the mixture of products (CeH_x, CeN, Ce₂Co₁₇H_x, Co) is formed according to data of the X-ray analysis. The availability of intermetallide use as working substance in the metal hydride accumulator of hydrogen working at temperatures up to 150 ºC is considered. The hydrogen accumulator based on CeCo3 will have the good operating characteristics: relatively low temperature of hydrogen desorption, acceptable hydrogen capacity, easy to charge and relatively low cost.

 

 

The paper is devoted to the investigation of hydrogen production from magnesium oxidation in aqueous salt solutions under low temperature conditions. This study determines the solution compositions suitable for effective low-temperature magnesium oxidation with hydrogen production, and the reaction rate dependence on temperature. A number of experiments were conducted using various solution compositions. The obtained experimental results can be very useful when developing a hydrogen production system. The experimental data obtained demonstrate that at temperature of 0ºC magnesium conversion for MgCl₂ solution is equal to 94,5%, for AlCl₃ – 84,5%; at –20 ºC for MgCl₂ – 32,5%, for AlCl₃ – 65,1%; at –40ºC for AlCl₃ – 85,2%. Moreover the paper demonstrates that oxidation of magnesium powder in some aqueous solutions provides hydrogen production with high hydrogen yields even at low temperatures. The results of this study can be used for designing power supply systems which can operate in Arctic regions and provide electricity supply to drones (at 6,000 m above the sea level, T_ambient = –24 ºC).

 

 

Current commercial technologies of hydrogen generation have drawbacks. Vast amount of harmful byproducts are evolved, e. g. carbon dioxide (for example, steam reforming of natural gas process) or electricity source is demanded (water electrolysis process). The paper presents a hydrogen fueling station based on developed technology of hydrothermal oxidation of commercially available aluminum powder. Continuous mode reactor is filled in with predetermined ratio aluminum powder / water mixture and withdrawn with reaction products: steam-hydrogen mixture and aluminum hydroxide. Aluminum powder reacts with water at temperature 300-320 ºС and pressure 11-13 MPa. High amount of heat released by oxidation (15,3 MJ/kg aluminum) is used to drive turbine and for electricity generation. This energy is used to power the hydrogen compressor, pumps and control systems. Thus this hydrogen fueling station is fully autonomous, independent from outside power systems and could be located far from power supply networks. Hydrogen generated meets grade A demands (99,99% H2) and could be used in fuel cell without cleaning. Aluminum hydroxide (boehmite) is valuable high demand product. Parameters of aluminum powder driven fueling station with capacity of 200 kg of hydrogen per day is shown.

The formation of soot particles during the combustion of hydrocarbon fuel relates to the incomplete combustion. The degree of chemical unburnt can reach 10–15%. The paper studies the soot extinction in hydrocarbon flames. Soot particles can reveal itself as a homogeneous structure or contain multiple functional groups bound to the carbon skeleton. The presence of molecules and their fragments or other chemical bonds in the substance was determined by Fourier Transform Infrared Spectrometer FTIR-1201. Spectrograms of analyzed samples were recorded in the range of 4000 cm^-1 to 400 cm^-1. Strong absorption in a wide spectral range of 4000 cm^-1 to 500 cm^-1 is typical to the soot samples of saturated hydrocarbons. Radiation absorption by radicals С = С, СН, СН₂, СН₃ in a spectral range of 3000 cm^-1 to 1000 cm^-1 and hydroxyl OH-group in a spectral range of 3600 cm-1 to 3200 cm-1 is typical to the soot samples of aromatics. The paper detects some nanostructures as С60 (ν = 1430 cm^-1) and С70 (ν = 1460 cm^-1). Carbon nano-tubes grown by catalytic methane as defect-free structure have high transparency. Strong absorption lines by С = С, СН, СН₂, СН₃ were observed in the range of 1800 cm^-1 to 1000 cm^-1. Soot particles are the main radiator in the IR-region which determines flame’s emission ability. During thermal exposure (afterburning), active centers were identified in the soot particles ensemble, along with their location and the nature of their structure. Soot particles with more developed surface have a shorter induction time of reacting with oxygen in the air and are more active. The induction time of active centers in highly disperse soot is much higher.

 

 

In this study, we evaluate the potential of using Gen5 (1.4 m² ) KAI PECVD reactors, originally designed for production of double-junction thin film silicon (micromorph) modules, for manufacturing of high-efficiency silicon heterojunction (Si-HJ) solar cells. It is shown that Gen5 KAI PECVD reactors can provide an excellent uniformity of optical and electrical properties of hydrogenated amorphous silicon layers across entire surface of a 110 130 cm² wafer carrier. Surface passivation with low surface recombination velocity (< 4 cm/s) is achieved on n-type FZ c-Si wafers. First part of the study was conducted on the pilot line at the R&D Center TFTE LLC (Ioffe Institute, St. Petersburg, Russia), where Si-HJ solar cells, with a mean efficiency over 21,5%, were made. Further, these results were transferred on the production line of the Hevel LLC factory, where cells with mean efficiency over 21,5% are produced using commercial 6-inch n-type CZ c-Si wafers and Gen5 KAI PECVD reactors. The potential to reach the efficiency above 22% and solar panels with output power over 300 Watt is also demonstrated.