Energies

Pyrolysis is a thermochemical conversion process producing biochar, gas, and bio-oil at high temperatures in an oxygen-free environment. Specific pyrolysis conditions enable a significant production of the aqueous phase of bio-oil, commonly known as wood vinegar. Wood vinegar contains organic compounds such as acetic acid and phenols derived from bio-oil. These compounds have herbicidal properties against weeds and biostimulant properties for plant growth. This study reveals the potential for efficient management of cranberry residues consisting of stems and leaves by producing wood vinegar through pyrolysis at 475 °C with a humidity level of 20%. Membrane separation of wood vinegar, using nanofiltration (NF) and reverse osmosis (RO) membranes, yielded phenols in the retentate and acetic acid in the permeate with respective yields of 44.7% with NF membrane and 45% with RO membrane. Biostimulation tests using 2% of the retentate showed significant germination rates for basil, sage, and parsley plants. Additionally, using 40 mL of the wood vinegar permeate (30 mL injected at the base and 10 mL sprayed on the leaves) resulted in leaf damage, measured by conductivity (leakage of electrolytes released by the leaves), of 62.3% and 20.5% respectively for quack grass and white clover, two weeds found in cranberry production. Full article

In the modern era, where the global energy sector is transforming to meet the decarbonization goal, cutting-edge information technology integration, artificial intelligence, and machine learning have emerged to boost energy conversion and management innovations. Incorporating artificial intelligence and machine learning into energy conversion, storage, and distribution fields presents exciting prospects for optimizing energy conversion processes and shaping national and global energy markets. This integration rapidly grows and demonstrates promising advancements and successful practical implementations. This paper comprehensively examines the current state of applying artificial intelligence and machine learning algorithms in energy conversion and management evaluation and optimization tasks. It highlights the latest developments and the most promising algorithms and assesses their merits and drawbacks, encompassing specific applications and relevant scenarios. Furthermore, the authors propose recommendations to emphasize the prioritization of acquiring real-world experimental and simulated data and adopting standardized, explicit reporting in research publications. This review paper includes details on data size, accuracy, error rates achieved, and comparisons of algorithm performance against established benchmarks. Full article

This paper analyses the energy poverty status in off-grid rural households and its underlying socioeconomic factors. Employing the Foster–Greer–Thorbecke Technique and Probit regression on data from 53 households, the study uncovers a diverse array of energy sources in use, including firewood, paraffin, LPG, candles, and generators. Despite this energy source diversity, the poverty line threshold, as measured by the per capita energy expenditure line (92.40 ZAR) (1 US Dollar = ZAR 18.20), reveals the prevalence of energy poverty. Approximately 15% of respondents are experiencing severe energy poverty and 22% are facing moderate vulnerability to energy poverty, while over 50% are not energy poor. This indicates that, although they may lack access to electricity, their energy usage and expenditure in other forms might still be sufficient to meet their basic energy needs. This distinction highlights the importance of assessing energy poverty, extending beyond a simplistic assessment of absolute poverty but taking into account the dynamic nature of income levels. Gender, household size, formal education, and social grants emerge as key indicators shaping the energy landscape in the area. The results clearly indicate that male-headed households and larger households are less susceptible to energy poverty, while increasing formal education and social grants increases the risk of households being exposed to energy poverty. These findings suggest that the problem of energy poverty in the area is uniquely linked to social, economic, and cultural issues. Therefore, interventions targeted at addressing energy poverty problems must address the underlying social, economic, and cultural factors. Full article

With the deployment of numerous innovative smart grid technologies in modern power systems, more real-time communication and control are required due to the complexity and proliferation of grid-connected systems, making a power system a typical cyber-physical system (CPS). However, these systems are also exposed to new cyber vulnerabilities. Therefore, understanding the intricate interplay between the cyber and physical domains and the potential effects on the power system of successful attacks is essential. For cybersecurity experimentation and impact analysis, developing a comprehensive testbed is needed. This paper presents a state-of-the-art Hybrid Physical Co-simulation SG testbed at FIU developed for in-depth studies on the impact of communication system latency and failures, physical events, and cyber-attacks on the grid. The Hybrid SGTB is designed to take full advantage of the benefits of both co-simulation-based and physical-based testbeds. Based on this testbed, various attack strategies are tested, including man-in-the-middle (MitM), denial-of-service (DoS), data manipulation (DM), and setting tampering (change) on various power system topologies to analyze their impacts on grid stability, power flow, and protection reliability. Our research, which is based on extensive testing on several testbeds, shows that using hybrid testbeds is justified as both practical and effective. Full article

The extensive deployment of Modular Multilevel Converters (MMCs) in AC/DC systems can lead to complex resonance issues. Impedance modeling forms the foundation for analyzing the stability of interconnected system. Existing investigations primarily address resonance concerns on the AC side of MMC. In the process of impedance modeling, the DC system is generally approximated as an ideal voltage source, thereby neglecting its dynamic impact on the impedance characteristic of MMC. Such simplification may result in inaccuracies within stability analysis findings. Based on the multi-harmonic linearization method, this paper introduces an impedance modeling approach that takes into account the characteristics of the DC port. Taking DC voltage control as a case study, the impedance model for the AC side of the MMC is established. The results of programming calculation and simulation measurement of sequence impedance are mutually verified. Finally, the MMC impedance responses determined by different DC port characteristics are analyzed. Significant alterations in MMC impedance characteristics are introduced by DC side resistance and capacitance, which may result in negative damping effects and a decrease in system stability margins. The DC side inductance has a relatively minor impact on MMC impedance responses. The analysis results show that the sequence impedance model of MMC considering DC port characteristics can improve the accuracy of stability analysis results. Full article

High Voltage Direct Current power links are usually designed to adopt, on a continuous basis or during emergency operations, two grounding plants using the soil or seawater as a link–current return path. Such DCs flowing into the ground can cause problems, of which one of the most important is the increased risk of the corrosion of metallic structures in the area. Normally, the simplest mitigation technique is to keep an adequate distance between the main grounding plants and any metallic structure that can be corroded. Normally, such distances are not less than 5 km. However, there are situations where this approach cannot be applied, for example due to geographical constraints. In this paper, we describe and analyze the behavior of a mitigation technique that can be adopted when the HV pole cable is laid closer than the recommended distance to the main ground electrode. This paper is focused on the minimization of deleterious effects on the cable’s metallic sheath and its earthing points, distributed along it by means of sheath segmentation. The suggested approach appears well-suited to substantially diminishing the current flowing through the sheath of an HVDC power cable. In the segmented scenario, the sheath’s power dissipation is less than one-hundredth of that in the typical continuous configuration. Full article

In the face of the traditional fossil fuel energy crisis, solar energy stands out as a green, clean, and renewable energy source. Solar photovoltaic tracking technology is an effective solution to this problem. This article delves into the sustainable development of solar photovoltaic tracking technology, analyzing its current state, limiting factors, and future trends. The adjustment of solar panel orientation using solar tracking technology to maximize energy generation efficiency has been widely implemented in various fields, including solar power plants. Currently, limiting factors for this technology include energy generation efficiency, costs, and the complexity of various environmental conditions. In terms of sustainable development, this article emphasizes the importance of photovoltaic materials and manufacturing innovation, energy efficiency improvements, as well as the integration of smart and digital technologies. Future trends include higher precision, broader applications, and lower costs. Solar photovoltaic tracking technology will play a pivotal role in global energy production, fostering the realization of a clean and sustainable energy future. Full article

The management of wastewater from soilless tomato cultivation poses a technological and economic challenge. Given the above, the aim of this study was to determine the treatment efficiency of wastewater from soilless tomato cultivation in a bio-electrochemical reactor under conditions of direct electric current flow. The treatment efficiency was tested in three time variants of wastewater exposure to the electric current: V1—24 h exposure phase; V2—12 h exposure phase/12 h no exposure phase; and V3—12 h no exposure phase/12 h exposure phase. Experiments were conducted with two organic substrates, sodium acetate and acetic acid, at the C/N ratio of 1.25, with a direct current intensity of 1.25 A·m⁻² and hydraulic retention time of 24 h. The study results show the feasibility of achieving a satisfactory technological effect in a bio-electrochemical reactor without the need for electric current flow throughout the 24 h treatment cycle. From the energy consumption and technological standpoints, the most viable approach, ensuring 90.4 ± 1.6% and 94.9 ± 0.7% efficiencies of nitrogen and phosphorus removal, respectively, turned out to be feeding the reactor with sodium acetate and wastewater exposure to the electric current flow only during the first 12 h of the treatment cycle. The scope of the conducted research justifies its continuation in order to determine the optimal time for supplying electricity to the bio-electrochemical reactor and the impact of the C/N value on the nitrogen and COD effluent concentrations. Full article

The European Union’s climate policy aims to reduce greenhouse gas emissions by 55% by 2030 and to achieve climate neutrality by 2050. One of the instruments for achieving these climate goals is the development of offshore wind energy. Unfortunately, Poland, as one of the few European Union countries with access to the sea, does not have offshore wind farms yet. The purpose of this article is to determine the importance of offshore wind energy for the development of Poland based on the example of two sea regions: the West Pomeranian and Pomeranian Voivodeships. This article uses the input–output method to determine the economic effects of offshore wind power. The region’s share in the supply chain was determined based on the location of the offshore wind energy sector. A comparative analysis with the Saint-Brieuc offshore wind farm in France made it possible to show the differences between the studied locations. The supply chain share of the regions surveyed was 2.28% and 6.00% in the CAPEX phase and 5.98% and 8.23% in the OPEX phase. The annual average global value in the CAPEX phase at the country level was EUR 2793 million, and at the regional level, EUR 243 million and EUR 663 million. In the OPEX phase, the corresponding values are EUR 2106 million, EUR 223 million and EUR 663 million. The average annual employment in the CAPEX phase at the national level amounted to 26,323 jobs and at the regional level, 1953 and 5804. In the OPEX phase, employment amounted to 4790, 558 and 751 jobs, respectively. On the other hand, the average annual value added in the CAPEX phase at the national level was EUR 1221 million, and at the regional level, it was EUR 106 million and EUR 290 million. In the OPEX phase, it was EUR 920 million, EUR 97 million and EUR 239 million, respectively. While not all of the findings are conclusive, in general, the domestic offshore wind industry has weaker economic linkages and lower wage levels than the location adopted for comparison. It uses more labour-intensive economic sectors with lower OPEX value added. The results of the analyses presented in this paper are of crucial importance not only for Poland, as their advantage is the possibility to present, from an economic point of view, the profitability of this type of investment in general. Full article

Gas diffusion layers (GDLs) in high-temperature, high-humidity, and high-electric-potential environments can be affected by the carbon corrosion and degradation of Polytetrafluoroethylene (PTFE) network structures, resulting in reduced reliability and hydrophobicity. By using cyclic voltammetry and offline characterization, a high-potential scanning of 1–1.5 V is applied to the GDL in the three-electrode system, considering the role of gradient graphitization degree and pore size structure in corrosion. Accelerating the electrochemical corrosion process of carbon and PTFE allows the identification of corrosion location, extent, and determinants. The results indicate that after 800 cycles of high-potential triangulation scanning, the graphitization of gas diffusion base has the most significant impact on the GDL’s durability. On the other hand, the durability of the GDL’s microporous layer is influenced by its small pore size structure rather than its graphitization degree. Furthermore, the corrosion process of GDLs with a small pore size structure tends to be relatively slow, providing a basis for GDL selection and durability prediction. Full article

During the water injection development process of highly deviated wells in low-permeability reservoirs, the water flooding distance between different layers of the same oil and water well is different due to the deviation of the well. In addition, the heterogeneity of low-permeability reservoirs is strong, and the water absorption capacity between layers is very different. This results in poor effectiveness of commonly used layered injection methods. Some highly deviated wells have premature water breakthroughs after layered water injection, which affects the development effect of the water flooding reservoirs. Therefore, based on the analysis and research of the existing layered injection allocation method and sand body connectivity evaluation method, considering the influence of sand body connectivity, the real displacement distance of highly deviated wells, reservoir physical properties, and other factors, a new methodology for determination of layered injection allocation in highly deviated wells drilled in low-permeability reservoirs is proposed. In this method, the vertical superposition and lateral contact relationship of a single sand body are determined using three methods: sand body configuration identification, seepage unit identification, and single sand body boundary identification. The connectivity coefficient, transition coefficient, and connectivity degree coefficient are introduced to quantitatively evaluate the connectivity of sand bodies and judge the connectivity relationship between single sand bodies. The correlation formula is obtained using the linear regression of the fracture length and ground fluid volume, and the real displacement distance of each layer in highly deviated wells is obtained. The calculation formula of the layered injection allocation is established by analyzing the important factors affecting the layered injection allocation, and a reasonable layered injection allocation is obtained. The calculation parameters of this method are fully considered, the required parameters are easy to obtain, and the practicability is strong. It can provide a method reference for the policy adjustment of layered water injection technology in similar water injection development reservoirs. Full article

This study aims to analyze the zero-voltage-switching (ZVS) region of a Triple-Active-Bridge (TAB) converter with five degrees of freedom. A TAB converter is an isolated converter derived from a dual-active-bridge (DAB) converter and composed of three full bridges (FBs) coupled to three winding transformers. To reduce the switching loss of the 12 active switches that compose 3 FBs, the ZVS operation is essential. However, owing to the numerous operation modes derived by five-phase shift ratios, ZVS analysis is complicated, particularly in the time domain. Therefore, this study presents the ZVS analysis model of the TAB converter based on the generalized harmonic approximation (GHA). Through the GHA of a TAB converter, the proposed model consists of unified formulas applicable to all operating ranges of the converter. Unified formulas consider all parameters, such as series inductance, port voltage, parasitic capacitance, transformer voltage, and turn ratio. In the proposed model, the ZVS area is confirmed using five-phase ratios with voltage modulation ratios as variables and verified using MATLAB and experiments. Full article

The application of 5G-based communication for pilot protection in a distribution network with distributed generators is becoming increasingly widespread, but the existence of a 5G communication transmission data delay adversely affects the rapidity and reliability of the pilot protection based on the principle of the traditional dynamic time warping distance (DTW) algorithm. Therefore, to address this problem, and according to the difference in fault currents between distributed generators and synchronous machines, a new scheme of pilot protection based on the principle of an improved DTW is proposed. The scheme firstly performs cosine transform on the fault current sequence, and then it normalizes the DTW value. Finally, the proposed scheme is verified via simulation. The simulation results show that, compared with the traditional DTW, the proposed algorithm has better anti-delay characteristics and a stronger anti-interference ability, and the scheme can quickly and reliably identify in-zone and out-of-area faults with strong noise resistance. Further, the action times for a single-phase ground fault, two-phase ground fault, two-phase-to-phase fault, and three-phase short-circuit fault were reduced by 2.9 ms, 4.54 ms, 5.81 ms, and 5.89 ms, respectively. In addition, it is also sui for a distribution network with a high wind and photovoltaic penetration rate. Full article

The randomness of the power supply side and the load side of comprehensive energy systems is increasingly prominent. It is very difficult to meet demand through traditional planning methods. To solve this problem, this paper explores the coordinated planning of a power system under uncertain characteristics using the multilinear Monte Carlo method. The uncertain characteristic model and probability density function of the system’s power supply side and load side are established. Taking the optimal operating cost and the maximum wind power consumption as the system planning objectives, a system coordination planning scheme is established, and it is solved by multilinear Monte Carlo simulation. The superiority of this method is verified by taking the modified IEEE 39-bus test system as an example. This method can provide a reference for system planning. Full article

In the current framework of energy transition, renewable energy production has gained a renewed relevance. A set of 75 papers was selected from the existing literature and critically analyzed to understand the main inputs and tools used to calculate solar energy and derive theoretical photovoltaic production based on geographic information systems (GISs). A heterogeneous scenario for solar energy estimation emerged from the analysis, with a prevalence of 2.5D tools—mainly ArcGIS and QGIS—whose calculation is refined chiefly by inputting weather data from databases. On the other hand, despite some minor changes, the formula for calculating the photovoltaic potential is widely acknowledged and includes solar energy, exploitable surface, performance ratio, and panel efficiency. While sectorial studies—targeting a specific component of the calculation—are sound, the comprehensive ones are generally problematic due to excessive simplification of some parts. Moreover, validation is often lacking or, when present, only partial. The research on the topic is in constant evolution, increasingly moving towards purely 3D models and refining the estimation to include the time component—both in terms of life cycle and variations between days and seasons. Full article

The synergistic combination of Nafion and sulfonated graphene oxide (GOsulf) in nanocomposite membranes emerged as a promising strategy for advancing proton exchange membrane fuel cell (PEMFC) technology. In the pursuit of elucidating the effect of GOsulf introduction on transport properties and electrochemical performance of Nafion, this work provides a systematic study combining swelling tests, water release tests, ¹H NMR characterization, and Electrochemical Impedance Spectroscopy (EIS) investigation. The incorporation of organomodified GO nanolayers alters the distribution of water molecules within the hydrophilic domains of Nafion and produces a considerable increase in the “bound-water” fraction. This increases its water retention capability while ensuring very high diffusivity even under high temperatures, i.e., 1.5 × 10⁻⁵ cm² s⁻¹ at 130 °C. These peculiar features enable Naf-GOsulf to successfully operate under a dehydrating environment, yielding a proton conductivity of 44.9 mS cm⁻¹ at 30% RH. Full article

Despite the presence of relatively high insolation, solar photovoltaic water pumping (SWP) is rarely used for water provision in Malawi. Current methods of water abstraction are labour-intensive and have low discharge rates. A stakeholder analysis was carried out to evaluate the role, responsibilities, and challenges faced by individuals, communities, and organisations involved in developing SWP systems. Analysis of data collected via semi-structured interviews with stakeholders from government departments, public and private organisations, entrepreneurs, non-governmental organisations, and microfinance organisations shows that the national government should provide an enabling environment for other actors to deliver SWP projects. Further, this study reveals diverse interlinked challenges in delivering sustainable water and energy services related to policies, monitoring, coordination, financing, human resources, information and awareness, stakeholder malfeasance, political interference, and flawed community management. The impacts of these challenges result in inadequate water service provision resulting from access inequality, non-functionality, substandard installations, reliance on donations, substandard renewable energy products, and slow technology uptake. The results of this study imply that, given appropriate finance and management frameworks, effective coordination, enforcement of product and installation standards, and awareness and sensitisation of communities to SWP, significantly improved access to drinking and irrigation water for the rural population of Malawi and other countries in sub-Saharan Africa can be achieved. Full article

The global charcoal trade is steadily growing, with high-income countries importing significant quantities of this material from regions where its production is often associated with severe environmental issues, including forest overexploitation, illegal logging, and environmental pollution. Promoting local charcoal production in high-income countries is crucial to addressing these challenges. In this study, we have chosen to focus on the European context, specifically emphasizing Italy as a case study. Our study aimed to comprehensively compare five distinct charcoal production systems, including both traditional and modern solutions, with a specific focus on evaluating the quality of the resulting charcoal. Additionally, improvements were evaluated to enhance production efficiency. Traditional systems cannot satisfy production requests, resulting in inefficiencies in manpower, costs, times, and yield. Conversely, recent innovations consider mobile and stationary kiln prototypes. Mobile kilns offer flexibility and cost savings but require operator expertise, limit automation, and have long cycles. In contrast, stationary systems operate continuously, increasing productivity and efficiency, despite higher investment costs. Notably, charcoal quality showed minimal differences. These findings highlighted the potential of new technologies to enhance efficiency, reduce cost and environmental impact, and promote sustainable charcoal production. Full article

This document presents a study of thermal inertia in the subsoil adjacent to the Civil Engineering laboratory of the Technological Institute of Sonora (ITSON) in the south of Sonora, Mexico, in service of the development of a solution proposal of a ground-coupled air heat exchanger for the cooling months. The research was divided into three phases: first, the monitoring of temperature in 10 layers of the ground; second, the analysis of thermal ground properties; and last, the design and simulation of a ground-coupled air heat exchanger. The objectives were to determine the variation in the thermal inertia of the soil with depth and over time and to determine the optimum depth for a ground-coupled heat exchanger system. The second objective was to develop a design proposal for a ground-coupled heat exchanger for the university laboratory. We found that the optimum depth is 3.0 m in a soil with high-compressibility clay with 21% humidity and 0.152 W/mK of thermal conductivity. However, the proposed design identified the best depth for the cooling system as 3 m considering a ground-coupled heat exchanger for a volume of 222.2 m³, corresponding to the volume of the classrooms of the building. With this design, the approach was to reduce the temperature by at least 10 °C on the hottest day (41 °C) of the year studied. We concluded that with this kind of system, the climate of the building studied could reduce the thermal load of active AC systems and reduce the energy load by 59%. Full article