The article deals with the problems of the PV plants operation in the low voltage network (LVN), namely the influence of PV generation on bus voltages and stability of network, as well as disconnecting the inverters from network in order to avoid overvoltages. The operating of PV inverter tied to LVN is considered on the framework of the reduced two-bus equivalent circuit. One bus of this circuit describes the inverter which is connected to the step-up transformer via short line and second one is the equivalent representation of LVN. The reduced two-bus circuit in contrast to the multi-bus schemes has exact solutions for power flows between PV plant and network. The analytical solutions obtained for this model allows us to determine the voltage stability region, the disconnecting conditions from the network (islanding), the dependence of the bus voltages on the levels of generation and load. On the base of this model, the monitoring data for power and output voltages of three-phase Growatt 30 kW inverter were analyzed. The inverter is tied to LVN by a relatively short line segment with known parameters which is typical for private and small industrial photovoltaic systems. The stable operation of PV plant in the network depends on the ratio of generation and consumption levels at the bus on the plant side, as well as on the capacity of the connecting line. Under analyzing of an overvoltage in the inverter bus appearing due to large solar radiation, one should take into account the limited inverter’s possibility to reduce the output power by changing the operating point on the curve “voltagepower”. The article performs the optimization calculations which determine the parameters characterizing the inverter and line capacity. The developed method for analyzing monitoring data of modern inverters can be a useful tool in solving problems of PV plant equipment diagnostics, as well as of predicting the electricity amount supplied to the network.

Algae biomass is considered as an alternative raw material for the production of biofuels. The search for new types of raw materials, including high-energy types of microalgae, remains relevant, since the share of motor fuels in the structure of the global fuel and energy balance remains consistently high (about 35%), and the price of oil is characterized by high volatility. The authors have considered the advantages of microalgae as sources of raw materials for fuel production. Biochemical and thermochemical conversion are proposed as technologies for their processing. This paper presents the results of the study of the pyrolysis of the biomass of clonal culture of blue-green microalgae / cyanobacterium Arthrospira platensis rsemsu 1/02-P from the collection of the Research Laboratory of Renewable Energy Sources of the Lomonosov Moscow State University. An experiment to study the process of pyrolysis of microalgae biomass was carried out at the experimental facility of the Institute of High Temperatures RAS in pure nitrogen grade 6.0 to create an oxygen-free environment with a linear heating rate of 10 ºС / min from room temperature to 1000 ºС. The whole process of pyrolysis proceeded in the field of endothermy. The specific amounts of solid residue, pyrolysis liquid and gaseous products were experimentally determined. As a result of the pyrolysis of microalgae biomass weighing 15 g, the following products were obtained: 1) coal has the mass of the solid residue is 2.68 g, or 17.7% of the initial mass of the microalgae (while 9.3% of the initial mass of the microalgae remained in the reactor); 2) pyrolysis liquid – weight 3.3 g, or 21.9% of the initial weight; 3) non-condensable pyrolysis gases – weight 1.15 l. The specific volumetric gas yield (the amount of gas released from 1 kg of the starting material) was 0.076 Nm³ / kg.
The analysis of the composition and specific volume yield of non-condensable pyrolysis gases formed in the process of pyrolysis, depending on temperature. It is shown that with increasing temperature, the proportion of highcalorie components of the gas mixture (hydrogen, methane and carbon monoxide) increases. The calorific value of the mixture of these gases has been estimated.

The suitability of hydrogen as an energy management solution in a run-of-river hydropower plant inCentral Italyis evaluated from a life-cycle perspective. Hydrogen production at off-peak hours via electrolysis is considered, as well as potential hydrogen storage in metal hydrides followed by hydrogen use at peak hours for power generation using fuel cell technology. Hydropower generation and hydrogen production are identified as the subsystems contributing most to the nine evaluated impact categories (e.g., global warming, abiotic depletion and cumulative energy demand). The renewable hydrogen produced shows a more favourable life-cycle environmental and energy performance than conventional hydrogen generated via steam methane reforming. Furthermore, when enlarging the system with hydrogen use for power generation, the renewable electricity product shows a better life-cycle profile than conventional electricity for the Italian electrical grid. Overall, under life-cycle aspects, hydrogen is found to be a suitable energy solution in hydropower plants both as a hydrogen product itself (e.g., for transportation) and as a feedstock for subsequent power generation at peak hours.

Against the background of diminishing traditional energy sources, increasing negative impact on the environment, also due to some energy sectors, as well as the growing threat of extreme increase in the waste on a global scale, SRES have a serious potential to play the role of one of the key methods to achieve a sustainable balance, without any harm to the economic development. In practice, if assumed that the total population of the Earth is 7 billion people, at least 5 million tons of waste is generated on a daily basis (not counting the industrial ones). Of them, circa 2 million tons are non-recyclable, but these could be transformed into energy. Modern technologies offer up to 50% conversion of the source materials into usable free energy––i.e. there is a potential for the generation of approximately 1 million МW/h per day, or at least 300–350 TW/h per annum. This amounts to the whole electricity consumption of 5–10 small developed countries likeBulgaria,Slovenia, etc. The improvement and implementation of the SRES technologies will require significant expenses for scientific research and development. A part of these expenses can be covered by the general provision of incentives for alternative energy sources, another part should be provided by external sources, including funding from the central budgets, grants, as part of public-private partnerships, etc. The offered article examines the economics of the SRES, and all related factors, including their role and place in the energy sector, significance for the protection of the environment and for the achievement of the sustainable development goals (SDGs), adopted within the UN. An attempt is made to develop the existing and to offer new criteria for a more accurate and universal definition of the SRES. The objective of the article is not to claim to be an universal and exhaustive study of all aspects, related to the nature and use of the SRES, but it is rather an attempt to systematize and carry out a comparative analysis of the main problems, related to the SRES, as well as to draw the attention and stir a wider discussion on a topic, which––according to the authors––undeservedly fails to be sufficiently incorporated into the studies and research, related to the alternative energy development. Special attention is drawn to the opportunities provided by waste-to-hydrogen solutions alongside with other waste-to-energy approaches. Authors are also introducing for the first time the notion of “double-green-solution” as a specific feature of the waste-to-energy solutions. The article may be of interest to economists, investors and practitioners.

The paper discusses the benefits of processing pyrite concentrates using a new technology that uses roasting in an atmosphere of water vapor. There are various technologies for the processing of pyrite concentrates containing precious and non-ferrous metals, Au, Ag, Cu and other elements. These technologies often have such disadvantages as undesirable release of sulfur dioxide into the environment, incomplete extraction of useful metals.
The optimal modes of technological processes, such as firing temperature, the ratio of steam and solid phases, the duration of the process, the size of the particles, etc. are given. Special attention was paid to the desulfurization of pyrite concentrate with the prevention of the release of sulfur dioxide into the atmosphere, and its transfer into the phase of solid elemental sulfur or sodium sulfide.
The developed technology makes it possible to obtain an iron cinder, and with subsequent magnetic separation and reduction in a hydrogen atmosphere to obtain iron in the form of a sponge–a high-quality product for smelting steel or cast iron.
The proposed technology provides a closed loop cycle and waste-free with minimal environmental pollution. The technology was tested in a pilot laboratory setup using concentrates from the Kajaran deposit inArmenia.

The article deals with model/test experiments on laser thermal hardening with the registration of the dynamics of the material surface modification in real time using a laser projection microscope (monitor) in the geometry of “pump-probe”. Hardening of materials by laser radiation, as well as dimensional processing compared to traditional methods is much more environmentally friendly because it happens very quickly and almost without emissions of harmful substances. And the possibility of observing the surface at the time of the hardening process can improve the quality of processed products. With the help of a laser projection microscope, it is possible to detect the moment of appearance of the transition region arising from the interaction of laser radiation with matter, to monitor the dynamics of its expansion, to register the appearance of the thermal front, the melting front, oxide fronts which is relevant in the heat treatment processes. A large number of publications are devoted to such methods and their modifications which confirms the importance and effectiveness of diagnostic methods using laser projection microscope to study various dynamic processes in the interaction of laser radiation with matter. In this work, the modernization of laser projection microscope with inclusion in the probing channel of optical harness is carried out. The basic physical principles of the obtained system and the existing problems, as well as the prospects of their overcoming in various conditions of specific processes of laser thermal hardening, including the use of computer simulation to find the optimal optical circuits and modes, are revealed. Depth-of-field problems are discussed for the resulting image through an optical fiber/optical bundle when recording such dynamic processes and how to overcome them by choosing the appropriate optical scheme. The analysis is also carried out on the basis of computer modeling. These issues are important in the implementation of various thermal hardening regimes in experiments with single-and multi-beam radiation of a power laser affecting the object at the appropriate setting of the laser monitor in the probing channel.

The article calculates potentially effective for photobiological processes density light fluxes arc tube sodium lamps (HPS) and 250 watt Light Emitting Diode (LED) lamps 46 watts. The concept of light utilization for photobiological reactions is proposed to evaluate the energy component of the light spectrum suitable for optimal activation of plant photoreceptor systems that control the shaping process by changing the orientation of the biological system in space at an early stage of development in order to achieve maximum photosynthetic response. The calculations used the experimentally obtained values of the absorption coefficients of the leaf of Cucumis sativus L. Based on the data on the linear dimensions of the leaf of the plant and the dependence of the absorption spectrum on the age of the plant, as well as the action spectra of photobiological reactions (photosynthesis, dissipation of excess energy as heat, phototropic reaction, chlorophyll, photomorphogenesis) and emission spectra of light sources, we have calculated the mass of accumulated carbohydrates at an early stage of development Cucumis sativus L. In order to test the reliability methods of analytical evaluation, an experimental study of the effect of radiation data illuminators was carried out. For HPS 250, the weight of carbohydrates and the dry weight of the plant were0.24 g and0.20 g, respectively, for LED 46, the weight of carbohydrates and dry weight of the plant were0.05 g and0.05 g, respectively. The proposed system for assessing the efficiency of the spectrum and the intensity of radiation by the linear parameters of a plant is an intelligent basis for creating an energy-efficient system for automatically controlling LED lighting of a greenhouse with feedback on a measured parameter of a plant.

The article considers and analyzes an important stage in the development of laser systems for metal vapor from the point of view of biomedical applications. Since the advent of the first generation of domestic medical facilities with pulsed lasers on metal vapors, in particular, copper vapors (LSM), which were created in the FSUE “Research and Production Enterprise ‘Istok’”, not much time has passed. Now similar studies are widely developed and include a variety of uses, for instance, in oncology for treatment with photodynamic therapy (PDT), angioplasty of intravascular destruction of atherosclerotic lesions, dermatology and cosmetology for the treatment of facial skin defects, as well as otorhinolaryngology, gynecology, proctology, urology, and others. In that cases, doctors use the Yantar-2Fand Yakhroma-2 installations, developed on the basis of the “Kurs” LPM with radiation wavelengths λ = 510.6 nm and 578 nm and the average radiation power P_rad = 5–10 W and tunable in wavelengths in the range of λ = 620–670 nm. Laser radiation is delivered to the affected area of a bio-object using a flexible light-guide cable with a diameter of 400, 600 or 800 μm fiber, which is one of the most convenient medical instruments. A compact and air-cooled medical installation of the new generation “Yakhroma-Med” based on the pulsed LPM “Kulon” with an average radiation power at the output of the light-guide cable P_rad = 1–3 W uses in dermatology and cosmetology (together with the Lebedev Physics Institute of the Russian Academy of Sciences). Today, YakhromaMed is the leader in non-ablative technologies and is optimal for removing vascular, pigmented and unstained skin defects, treating acne and smoothing wrinkles. It is used in more than 100 clinics in Russia and abroad. Moreover, for scientific and practical medicine in the field of oncology, low-intensity laser therapy and surgery, dermatology and cosmetology, etc., a compact air-cooled industrial multifunctional high-intensity medical unit “Kulon-Med” (similar to Yakhroma-Med) based on two pulsed lasers was developed: LM “Kulon” with an average radiation power P_rad = 10 W and LVRK with radiation tunable in wavelengths in the range λ = 620–750 nm and radiation power P_rad = 1–3 W (together with Ltd. NPP VELIT, Kurchatov Institute and the Hertzen Hermitage Research and Development Institute). The laser radiation is transported using four flexible light-guide cables with a conductive quartz fiber diameter of 400 and 600 μm, which makes it possible to perform a therapeutic and prophylactic procedure simultaneously in several rooms. Medical facilities of this class have been put in many medical institutions.
This report on the use of CVL in medicine says only about the developments in theMoscow region.