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In this paper, the implementation of a simulation model for studying the effect of cross-bonding of metallic sheaths and/or non-magnetic armor of single-core medium voltage cables in the same circuit is discussed. With the use of single-core cables, the resistive losses due to the induced circulating currents in cable sheaths or armors causes an increase of cable temperature that reduces its ampacity. In addition, the risk of electric shock due to induced voltages may be present if a person is exposed to the armor/sheath at the unbounded end. For this reason, special bonding techniques are used to significantly reduce these currents. The authors have implemented a model that could be used to help optimize the cross-bonding configuration for single-core cables employed in high-current industrial applications. The model has been experimentally validated thanks to actual data from a medium-voltage underground line.

Although hydrothermal carbonization of biomass components is known to be mainly governed by reaction temperature, consistent reports on the effect and statistical significance of process conditions on hydrochar properties are still lacking. The objective of this research was to determine the importance and significance of reaction temperature, retention time and solid load on the properties of hydrochar produced from an industrial lignocellulosic sludge residue. According to the results, reaction temperature and retention time had a statistically significant effect on hydrochar ash content, solid yield, carbon content, O/C-ratio, energy densification and energy yield as reactor solid load was statistically insignificant for all acquired models within the design range. Although statistically significant, the effect of retention time was 3-7 times lower than that of reaction temperature. Predicted dry ash-free solid yields of attained hydrochar decreased to approximately 40% due to the dissolution of biomass components at higher reaction temperatures, as respective oxygen contents were comparable to subbituminous coal. Significant increases in the carbon contents of hydrochar led to predicted energy densification ratios of 1-1.5 with respective energy yields of 60-100%. Estimated theoretical energy requirements of carbonization were dependent on the literature method used and mainly controlled by reaction temperature and reactor solid load. The attained results enable future prediction of hydrochar properties from this feedstock and help to understand the effect of process conditions on hydrothermal treatment of lignocellulosic biomass.

Artículos en revistas This work develops a stochastic optimization model for the creation of a bidding strategy for a generator in an energy call option auction similar to Brazil's, i.e., where the bidder can offer both the premium and the strike price. The objective of the model is to maximize the bidder's competitiveness while ensuring that the project's target rate of return is achieved with a given probability, for example 95%. The problem's complexity is compounded by uncertainties in fuel supply and the need to switch between fuels. The generators face the conundrum of bidding a single strike price to cover the expenses generated by using multiple types of fuels. We address the problem of finding bidding strategies which, taking into account uncertainty in fuel supply and risk constraints, set the combination of strike price and option premium that ensure a desired risk-adjusted return for greenfield dual-fuel thermal plants. info:eu-repo/semantics/publishedVersion

The adoption of solar systems has witnessed a remarkable growth rate in recent years, driven by increasing awareness of renewable energy and declining costs of solar technology. Solar systems offer several advantages, including abundant energy source, reduced carbon emissions, and potential cost savings. However, they also face challenges such as intermittency, limited energy storage capacity, and grid integration issues. By incorporating hydrogen in smart grids, these drawbacks can be addressed as hydrogen can serve as a means of energy storage, allowing excess solar energy to be stored as hydrogen and utilized during periods of low solar generation. Hydrogen-incorporated smart grids thus provide a complementary solution to enhance the reliability, stability, and scalability of solar systems, facilitating their integration into the broader energy landscape. Consequently, this chapter aims to provide a comprehensive review of green hydrogen-integrated sector-coupled smart grids and presents prospects for future advancements. The background and significance of hydrogen integration within smart grid systems are established. The fundamentals of hydrogen integration, including its role as an energy carrier and its integration within smart grid systems, are explored. The concept of sector coupling in smart grids is examined, emphasizing the interconnection of different energy sectors and the importance of achieving energy system integration. Existing green hydrogen-incorporated smart grid projects are reviewed, and experiences gathered from successful implementations are analyzed. Technological advancements, such as emerging green hydrogen production and storage technologies, are discussed along with smart grid control and management systems for efficient green hydrogen utilization. Economic and environmental considerations are evaluated, encompassing cost analysis, evaluation of environmental impacts, and identification of economic incentives. Future prospects and research directions are explored, aiming to identify key challenges, address gaps, and highlight areas for further investigation. Overall, through this comprehensive review and exploration of future prospects, a deeper understanding of hydrogen-integrated sector-coupled smart grids and their potential for advancing sustainable energy systems can be achieved.

Abstract Water transport control is the major issue of direct methanol fuel cell. High water flow rates through the fuel cell imply extra water feeding at the anode and flooding at the cathode. In the present work, water transport and flooding in the direct methanol fuel cell are investigated through both experimental and modeling analyses and an interpretation of such phenomena is proposed. The model is validated on the experimental data of two different fuel cells in an extensive range of operating conditions. The analysis elucidates that water transport through the cathode diffusion layer is determined by vapor diffusion, slightly affected by current density, and by liquid water permeation proportional to current density, that occurs when liquid pressure in the electrode exceeds a threshold value. To simulate the effects of cathode diffusion layer flooding two mechanisms must be considered simultaneously: superficial pore obstruction, proportional to liquid water concentration in cathode channel, and bulk pore obstruction, proportional to liquid water permeation. The modeling analysis proposes the correlations to reproduce the effects of cathode flooding and permits to discuss the onset and magnitude of such phenomenon and the influence of micro-porous layer.

Capítulos en libros This paper proposes a simplified approach to design power system stabilizers (PSSs) aimed at damping low frequency inter-area oscillations when only limited information of the power system is available. The proposed method uses a simplified two-machine test system and a robust-PSS-design method based on eigenvalue sensitivities. The proposed approach has been used to evaluate the contribution of a number of PSSs installed in Spanish generators to the damping of 0.15 Hz inter-area mode of the European system. info:eu-repo/semantics/publishedVersion

The extensive abandonment of agricultural lands in the Mediterranean basin has led to large landscapes being dominated by early-successional species, characterized by high flammability and an increasing fire risk. This fact promotes fire occurrence and places ecosystems in a state of arrested succession. In this work, we assessed the effectiveness of several restoration actions in redirecting these ecosystems toward more resilient communities dominated by resprouting species. These actions included the mechanical clearing of early-successional species, the plantation of resprouting species, and the combination of both treatments. For 13 years, we assessed shifts in the successional trajectory and ecosystem flammability by changes in: species composition, species richness, ecosystem evenness, the natural colonization of resprouting species, total biomass and proportion of dead biomass. We observed that the plantation and clearing combination was a suitable strategy to promote resilience. Species richness increased as well as the presence of the resprouting species introduced by planting. The natural colonization of the resprouting species was also enhanced. These changes in the successional trajectory were accompanied by a possible reduction of fire risk by reducing dead fuel proportion. These findings are relevant for the management of Mediterranean basin areas, but also suggest new tools for redirecting systems in fire-prone areas worldwide.

Abstract Fodder for feeding pork and poultry requires a large amount of cultivated and processed agricultural crops, which are often related to greenhouse gas emissions from land-use change (LUC). Given the rapid growth in meat production in Brazil for domestic consumption and international export, the link between LUC emissions and consumption of pork and poultry meat is central to evaluating the role of Brazilian meat production and the implications for international climate policies. In this paper, we first estimate LUC emissions from soybean production destined to feed pork and poultry in Brazil during the period 2008–2012. Second, we allocate such emissions to domestic and international consumption of pork and poultry meat. Concerning international consumption, Brazilian export of meat to 189 countries is evaluated. Although the majority of the LUC emissions from soybean production are tied to the domestic consumption, 17% and 39% of the emissions embodied in Brazilian pork and poultry, respectively, are exported to other countries. The most prominent destinations of Brazilian pork and poultry in terms of embodied LUC emissions are Eastern Europe, Asia and South America. In the case of pork, the fluxes of emissions from Brazil to Ukraine (1.28 Mt CO2-eq) and Russia (1.18 Mt CO2-eq) are particularly large. In the case of poultry, the largest transfers of embodied emissions are from Brazil to developing countries and especially the Middle East. These results are relevant to environmental policies and international agreements aimed at achieving the sustainability of Brazil's meat sector.