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Theoretical and experimental data on the concentrations of methane in different phase states in the porous structure of coals from the Donets Basin are reported. On the saturation of coal samples with methane, the natural conditions of the occurrence of methane in coal beds were simulated for the equilibrium coal–gas system. The amounts of methane dissolved in a solid matrix and adsorbed on the pore surfaces of coal matter were measured by broad-band NMR spectroscopy. The values obtained did not exceed 20% of the total methane absorbed by the sample in an equilibrium state at a pressure of 10 MPa. Sorbed methane was the predominant phase state only upon the opening of a high-pressure chamber after the emission of methane from filtration channels.

This paper presents a new more general formulation of the algorithms for reduced order eigenanalysis of selective modal analysis. This formulation, instead of assuming an initial separation of the state variables for the modes of interest into relevant and less relevant ones, uses approximations of the corresponding right and left eigenvectors in the form of reduced order subspaces. The advantage of the proposed formulation is that the reduced order subspaces are updated in each step of the iterative process. The performance of the generalized selective modal analysis is illustrated in a large scale power system.

Due to the adoption of EU Regulation No 517/2014, R404A is going to be banned in Europe in most of refrigeration applications, in which is typically used, due to its very high GWP value, 3943. In this paper an experimental comparison between R404A and R448A, a non-flammable alternative with GWP of 1390, is presented. The experimental tests are intended to simulate typical freezing and conservation temperatures and different condensing conditions. Despite cooling capacity of R448A is slightly below that of R404A, R448A energy consumption is even smaller; and R448A COP is higher than that obtained using R404A. Hence, it can be concluded that R448A could be an energy efficient alternative to R404A with a GWP reduction of 70%. Compressor discharge temperature remains at non-dangerous levels. The authors thankfully acknowledge "Ministerio de Educacion, Cultura y Deporte - Gobierno de Espana" (Grant Number FPU12/02841) for supporting this work through "Becas y Contratos de Formacion de Profesorado Universitario del Programa Nacional de Formacion de Recursos Humanos de Investigacion del ejercicio 2012".

An experiment system of tubes with one weakly covered end was established, and the outfield characteristics of fuel vapor explosions were studied through experiments. The results are as follows. After the rupture of the weakly covered end, three outfield overpressure peaks appeared due to the rupture of the weakly covered end (P1), the venting of the flame (P2), and external explosion (P3). The value of overpressure peaks showed a downward trend with an increase in distance, and the maximum overpressure was formed due to the external explosion. The value of overpressure peaks were related to the L/D ratio of the tube. With an increase in the L/D ratio, P1 and P3 in the near field showed an upward linear trend, while P2 and P3 in the far field showed a quadratic trend. In the case of the same L/D ratio, the maximum overpressure largely depended on the fuel volume fraction and external distance. The flame shape showed a changing process of jet flame - radial tension - mushroom cloud-shaped flame. The mushroom-shaped flame was formed mainly due to the Kelvin-Helmholtz instability and vortex effect, and the value of axial flame parameters were greater than those of radial ones. With an increase in the L/D ratio, the axial flame parameters showed an upward linear trend, the radial flame parameters showed a downward linear trend, and their ratio showed an upward linear trend.

This paper aims to reconsider prosumers’ role in the power markets in the early stages of their decentralization, accounting for rising self-supply trends, security threats, and economic and regulatory barriers. The development of prosumerism envisages finding the ratio between retail market sales under the feed-in tariff and the net billing mechanism. Within the methodology section, the indicator of prosumer efficiency for electricity generation (EUR/kWh) is proposed based on average consumption/production ratios and consumption/delivery incentives. To support household prosumers, the mentioned incentives on the renewable energy market consider the self-supply cost of electricity, the levelized cost of electricity for small-scale green energy facilities (solar photovoltaic and wind), and transaction costs. This paper evaluates prosumer efficiency under three consumption/production ratio scenarios for Ukrainian households (self-consumption of 40%, 20%, and 100% of green electricity annually generated by a household and selling the leftovers via the feed-in tariff) for 2023. The gradual movement from fixed tariffs for households toward market-based prices promotes the emergence of new related market players and their consolidation in the market. Participation in the organized power market segments is relevant for day-ahead market prices above 130 EUR/MWh, disregarding the households’ tariff rate. The low price caps inhibit the prosumer’s participation in the market, while the transition from the feed-in tariff to net billing significantly promotes their development only under high price caps.

There are many renewable energy sources available, especially wind energy, but it is not being fully utilized. In the wind energy industry, Wind Power Potential (WPP) is essential since it is critical to the development, operation, and optimization of wind power plants. WPP plays a significant role in the wind energy project life cycle, impacting site selection, project viability, technology choices, and ultimate success. This means that specific WPP for certain places need to be determined for development in wind industry.The goal of this study is to conduct a statistical comparison and analysis of the efficacy of various numerical methods, including the method of moments (MoM), the energy pattern factor method (EPFM), the maximum likelihood method (MLM), the energy density method (EDM), the energy pattern factor method of Sathyajith (EPFMS), Rayleigh's distribution (Rayl), and the novel energy pattern factor method (NEPFM). These methods are compared for different sites of Andhra Pradesh India. The NEPFM is considered the most effective approach for assessing the wind energy density in the regions of Visakhapatnam, Amaravati, and Tirupati. Conversely, the MLM (Modified Logarithmic Model) technique has demonstrated superior performance in evaluating the wind energy potential specifically for the Rajamahendravaram site. The Rayleigh distribution, also known as Rayl., was utilized as the primary approach for calculating the probability density of the geographical sites of Visakhapatnam, Rajamahendravaram, and Amaravati. Additionally, the energy pattern factor method was employed to analyze the site of Tirupati. The Rayleigh distribution is found to be the most suitable statistical model for estimating the cumulative density of site locations in Visakhapatnam and Amaravati. Similarly, the innovative energy pattern factor technique is recommended for analyzing the cumulative density of site locations in Rajamahendravaram and Tirupati.

One of the major goals of engine designers is the reduction of fuel consumption and pollutant emissions while keeping or even improving engine performance. In recent years, different technical issues have been investigated and incorporated into internal combustion engines in order to fulfill these requirements. Most are related to the combustion process since it is responsible for both fuel consumption and pollutant emissions. Additionally, the most critical operating points for an engine are both the starting and the warming up periods (the time the engine takes to reach its nominal temperature, generally between 80°C and 90°C), since at these points fuel consumption and pollutant emissions are larger than at any other points. Thus, reducing the warm-up period can be crucial to fulfill new demands and regulations. This period depends strongly on the engine cooling system and the different strategies used to control and regulate coolant flow and temperature. In the present work, the influences of different engine cooling system configurations on the warm-up period of a Diesel engine are studied. The first part of the work focuses on the modeling of a baseline engine cooling system and the tests performed to adjust and validate the model. Once the model was validated, different modifications of the engine coolant system were simulated. From the modelled results, the most favourable condition was selected in order to check on the test bench the reduction achieved in engine warm-up time and to quantify the benefits obtained in terms of engine fuel consumption and pollutant emissions under the New European Driving Cycle (NEDC). The results show that one of the selected configurations reduced the warm-up period by approximately 159 s when compared with the baseline configuration. As a consequence, important reductions in fuel consumption and pollutant emissions (HC and CO) were obtained.

Access to reliable and affordable energy is vital for sustainable development. In the off-grid areas of developing countries, decentralized energy solutions have received increasing attention due to their contributions to reducing poverty. However, most of the rural population in many developing countries still has little or no access to modern energy technologies. This paper assesses the factors that determine the successes and failures of decentralized energy solutions based on local harmonized case studies from heterogeneous contexts from Asia, sub-Saharan Africa, and South America. The case studies were analyzed through the coupled lenses of energy transition and the Water–Energy–Food Security (WEF) Nexus. The findings indicate that access to modern decentralized energy solutions has not resulted in complete energy transitions due to various tradeoffs with the other domains of the WEF Nexus. On the other hand, the case studies point at the potential for improvements in food security, incomes, health, the empowerment of women, and resource conservation when synergies between decentralized energy solutions and other components of the WEF Nexus are present.