The paper presents the results of the development of a methodology for a comprehensive assessment of the system's efficiency, which includes solar collectors, a heat storage tank, a ground heat accumulator, and a building heating system. The model of non-stationary heat exchange makes it possible to determine the area and the number of solar collectors and the volume of a seasonal (ground) heat accumulator for various climatic conditions, types of solar engineering equipment, types of heating systems in the building, providing the necessary temperature characteristics of the building. We have obtained analytical expressions for a seasonal change in solar radiation and ambient temperatures typical for a sharply continental climate, and have made a numerical study of the time of use of the accumulated energy for a building with a heated area of 70 m² . For a 500 m³ ground heat accumulator with a maximum heating temperature (90 °C), the stored energy is shown to be sufficient for heating the building with a warm floor system for more than 100 days. The paper submits the data confirming expediency of use of solar systems of heat supply with the ground heat accumulator for the severe climatic conditions characteristic of the Ural region of Russia. The use of ground heat accumulators is a simple and low-cost method of transferring solar energy in time (from summer to winter), which allows us to significantly reduce the cost of organic fuel for heating the premises during the heating season. The greatest efficiency of use of the energy accumulated in the ground is achieved when applying low temperature heating systems (underfloor heating, air heating). This technique is quite universal and can be used for any grounds and accumulative environments that differ from the natural ground by thermal physical characteristics (talcochlorite, talcomagnesite, salt compositions, etc.), as well as for other types of thermal loads, such as maintaining a favorable temperature regime in swimming pools and agricultural structures of enclosed soil.

We consider the possibility of improving the heat supply system in Chelyabinsk through the introduction of heat pump technology for the disposal of low-grade waste heat. The paper analyzes the problems of the heat supply system in Russia. The majority of consumers in large cities of the central Russia are supplied with heat energy through the centralized heat supply system. This approach is largely outdated and inapplicable to the modern energy system. We propose the method for increasing the efficiency of centralized heating using heat pumps. This paper makes the evaluation of the effectiveness of the use of this method, namely performs a calculation study, the final result of which is estimation of efficiency of low-grade waste heat utilization in the Chelyabinsk heat supply system. For this purpose, we have previously analyzed the sources of information on the ways of utilization of waste thermal energy, the principles of the heat pumps operation, and the classification of urban sources of waste heat. The first stage of this study is the development of a calculation technique that makes it possible to estimate at varying initial parameters of the heat supply system objects. The developed technique allows estimating the efficiency of using heat pumps for each category of municipal sources of waste heat energy: energy (CHP, boilers, heating networks) and non-energy (residential, public and production facilities) ones. The second stage is the application of this technique to Chelyabinsk. As a starting point for this stage, we take the data which characterize the climatic features, energy parameters of the sources of centralized heating supply, as well as data on the population, economy and industrial facilities in Chelyabinsk. The result of the study is the numerical value of the efficiency of waste heat utilization in Chelyabinsk.

The sensors for detection of toxic and chemical warfare agents (CWA) should be sensitive to low concentrations of gases – considerably lower than ones immediately dangerous to life or health concentrations. The paper shortly discusses classical CWAs and toxic industrial sensors; makes a comparison between nuclear weapons and chemical agents and a toxicity comparison between real gases and simulants. Moreover, the paper analyzes the simulants for testing the sensor devices and semiconductor gas sensor' technique; shows sensitivity change with dimethyl methylphosphonate (DMMP) gas concentration for sensor made of SnO₂. The MoO₃, NiO, Al₂O₃, In₂O₃, Pt, ZnO and ZrO₂ additives are reported to exhibit enhanced sensitivity to dimethyl methylphosphonate (DMMP), and Al2O3, In2O3, ZrO₂ and ZnO additives – to exhibit enhanced sensitivity to dipropyleneglycol methylethylene (DPGME). SnO2 devices with ZrO₂ and ZnO additives exhibit high sensitivity to acetonitrile. The sensors made from Co-doped SnO₂ films demonstrate sensitivity to CWAs such as sarin and yperite. We performed the measurements at the operating temperature of 210 ºC, and found that the sensor exposed comparatively greater concentration of target gas (200 ppm sarin and 100 ppm yperite) and the SnO₂ <Co> sensor was sensitive to yperite starting from 25 ppm. Furthermore, the sensitivities to 50 ppm and 12.5 ppm sarin were found. The paper presents the results of our studies on tin oxide/ multiwall carbon nanotube film nanocomposite sensors of PG, dimethylformamide (DMF) and formaldehyde (FA) using hydrothermal synthesis and sol-gel methods. The investigations of response/recovery characteristics in the 50–300 ^oC operating temperature range reveal that the optimal operating temperature for the PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times, was 200–220 ºC. A sensor response dependence on gas concentration in all cases was linear. We measured the minimal PG, DMF and FA gas concentrations at which the perceptible signal was registered.

We investigated the interaction of alloy of composition 80 at. % of Ti + 20 at. % of Fe (Ti₈₀Fe₂₀) with ammonia under pressure of 0.6 ÷ 0.8 MPa at the temperatures 100 ÷ 500 ºC: the phase transformations in the Ti₈₀Fe₂₀–NH₃ system were defined; the composition of products was established; the formation conditions of the hydride and nitride phases were found; the formation temperatures of the hydride phases with the greatest possible content of hydrogen for use of alloy in the metal hydride accumulators of hydrogen were determined. The study shows the dependence of the reaction direction of alloy with ammonia, taking place in presence of NH₄Cl (the 10 wt. % of alloy quantity) as activator, on temperature. One of the products of the reaction, which is carried out at 100 ºC, is the hydride phase of composition Ti₄FeH_8.3. With further a slight increase in temperature of reaction, this phase decomposes on hydride phases of the titanium and of the intermetallic compound TiFe. At interaction temperature of 200 ºC and above, insignificant amount of nitrogen is introduced into a metal lattice of hydride of an intermetallide of TiFeH_-2 with formation of the phase TiFeH_-2N_x. At temperature of 350 ºC and above, the titanium nitride TiN appears as a part of reaction product. The interaction of alloy and ammonia at 500 ºC leads to mixture of titanium nitride and metallic - Fe. The sharp increase in a specific surface area of reaction products at increase in process temperature from 250 ºC to 400 ºC (from 0.2 m ² /g to 46.4 m² /g) is shown to demonstrate the formation of mixture of high-disperse powders. The metal hydride accumulator of hydrogen on the basis of the studied alloy can work in a temperature range of room temperature to 600 ºC and allocate up to 3 wt. % of hydrogen.

We have developed the stand for the practical hydrogen power engineering course. This stand consists of hydrogen-air fuel cell, electronic system control, control of functional parameters and hydrogen source based on metal hydride cylinder. The specially manufactured 40 W stack is used in the stand as a fuel cell consisting of 22 membraneelectrode assemblies (MEA). We have investigated the current-voltage characteristics of the stack. Hydrogen fluxes of more than 0.7 l/min are shown to be required for the efficient operation of the fuel cell used in the stand 30 W under a current load of 3 A. We have studied the distribution of the temperature of the stack outer surface at different load currents, and establish that the maximum temperature does not exceed 45 ºC at the operating working load used in the stand. The paper describes the station hydrogen refueling metal hydride cylinders in detail. The station allows one to refuel metal-hydride cylinders with different form factors and volumes from 50 ml to 15 l. The connecting elements of the station withstand pressure drops from 0.1 Pa up to 1.5 MPa. The hydrides of La0.9Се0.1Ni5 and La_0.8Се_0.2Ni₅ alloys are used as a source of hydrogen. We have studied the P–C dependences cycles of hydrogen absorption and desorption for La_0.9Ce_0.1Ni₅ and La_0.8Ce_0.2Ni₅ alloys utilizing in metal hydride cylinders at temperatures of 25 ºC and 45 ºC. The paper gives a description of hydrogen filling procedure of these cylinders in detail. The developed stand allows one in real time to measure and stabilize the temperature of the fuel cell for two sensors with the edge and in the center of the fuel cell; to control the temperature of the metal hydride cylinder; to measure voltage and current on the fuel cell, and current through a connected external load irrespective of the internal electronic load of the stand; to measure the hydrogen flow. This stand can be applied to demonstrate the work of alternative energy sources, as well as for the training of personnel working in the field of energy.

Progress in hydrogen energy and promising directions for its modern development are closely related to the development of fuel cells, including solid oxide fuel cells, and solid state membranes for hydrogen, oxygen and synthesis gas production. A necessary condition for fabrication the economically competitive devices in this area is the use of cheap electrode materials combining high electrochemical activity and long-term stability. Ln₂NiO_4+δ oxides with the Ruddlesden–Popper layered structure with a high mixed ion-electron conductivity and moderate values of the coefficients of thermal expansion are promising materials for the development of oxygen-conducting membranes and cathodes of intermediate-temperature solid oxide fuel cells. The paper studies the structure, electrical conductivity, oxygen mobility and electrochemical properties of Ln_2-xCa_xNiO_4+δ (Ln = La, Pr, Nd; x = 0; 0.3) in order to determine the factors that have the most significant effect on the electrochemical activity of electrodes and their stability. We have found that doping with calcium leads to stabilization of the structure and an increase in the electrical conductivity of materials. However, addition of calcium decreases the electrochemical activity of the electrodes in varying degrees depending on the nature of the lanthanide. There is no direct interrelation of such a decrease of activity with either the electrical properties or the interstitial oxygen content. We have revealed correlation of the polarization resistance of electrodes between characteristics of oxygen transfer in the electrode material (self-diffusion coefficient, surface exchange constant). Using the C¹⁸O₂ SSITKA method, the total oxygen mobility in the doped materials is shown to fall due to a decrease in the content of highly mobile interstitial oxygen and hampering of the cooperative oxygen transport mechanism. In the case of La_1.7Ca_0.3NiO_4+δ , this leads to the appearance of a slow diffusion channel and a substantial decrease in the total diffusion coefficient value which leads to a sharp increase in the polarization resistance of the electrodes. This phenomenon is not observed in materials with praseodymium and neodymium. The electrodes based on Pr_1. La_1.7Ca_0.3NiO_4+δ and Nd_1.7 La_1.7Ca_0.3NiO_4+δ, developed in this work, have an acceptable level of the electrochemical activity along with a high electrical conductivity and increased stability in comparison with undoped compositions and can be recommended for use as cathodes for intermediate temperature fuel cells.

The paper compares catalytic properties of spinel mixed oxides of Co₃O₄ and NiCo₂O₄, that we synthesized, as possible catalysts for the oxygen reduction reaction in an alkaline medium. This reaction is one of the most important in the development of alternative energy sources with high specific characteristics – metal-air batteries and fuel cells. One of the reagents in such systems is oxygen; another necessary component can be a metal (Zn, Li, etc.) or hydrogen. We have employed the method of comparing catalytic activity for catalysts deposited on flat electrodes and have tried to achieve the sufficient adhesion in order to use the samples as electrodes. The Co3O4 catalyst was obtained on the substrate by hydrothermal method from a solution containing 0.1 M Co(NO₃)₂ and 0.4 M urea. The synthesis of NiCo₂O₄ was carried out electrochemically from a solution containing 0.01 M Ni(NO₃)₂ and 0.02 M Co(NO₃)₂. Sample characterization was carried out with X-ray analysis; electrochemical characteristics were obtained using cyclic voltammetry in 1 M NaOH solution. The paper finds out that catalytically active sites are formed on the electrode surface with a layer of the corresponding oxide during the cathodic polarization. Formation of one center during the electrode reaction corresponds to a twoelectron transfer. Total number of the active sites can be determined from the amount of electricity. Surface coverage was determined from the amount of electricity as a function of the potential calculated from the cathodic branch of the voltammogram curve. We carried out the calculation by the method of numerical integration using the trapezoidal rule in the Excel package. Based on the calculations performed, the form and parameters of the isotherm of the surface filling with active sites as a function of the electrode potential were established. The filling of the surface with active sites is shown for the first time to take place in accordance with the Frumkin–Temkin isotherm. We calculated the isotherm parameters, the density of the sites on the surface, and the effective distance between them. Most centers were obtained for an electrode with a layer of NiCo₂O₄ – 2.27∙10¹⁷ cm^-2 . The original technique is of interest for comparing the catalytic activity of electrodes from various materials.

The paper gives brief information about the corrosion-aggressive sulfur compounds in the pulverized coal boiler path. Sulfur dioxide (SO₂) and sulfuric anhydride (SO₃) are formed when coal burns with increased sulfur content. As the combustion products move along the convective shaft of the boiler, their temperature decreases and reaches the values of the beginning of condensation of sulfurous anhydride and sulfuric anhydride. The paper describes an economical and simple experiment that allows us to determine the measures how reduce low-temperature corrosion of low-temperature heating surfaces (LTHS). In the study of methods for increasing energy performance and improving the environmental efficiency of equipment and on the basis of analysis the results of industrial tests of various ways to reduce sulfur oxide emissions from the burning of non-projected brown coal species, some methods have been evaluated and scientifically grounded technical proposals have been prepared to achieve the minimum possible concentrations of sulfur oxides in emissions with flue gases into the atmospheric air. At the same time, a number of important legal acts containing a set of measures to switch to the principles of the best available technologies and the development of an information and technical handbook on the best available technologies (“Combustion of fuels in large installations for energy production”) have been taken into account for power facilities. In addition, some measures aimed at improving the reliability and efficiency of the operation of the STPP of boilers of thermal power plants have been identified in terms of environmental and economic feasibility.