One of the biggest problems of water with high concentrations of calcium is its susceptibility to causing scaling in industrial equipment (boilers, heat exchangers, pipes, reverse osmosis membranes, storage tanks, etc.). The purpose of this study was to evaluate a recently built filter press (EC) type electrocoagulation reactor and investigate the efficiency of water hardness removal. The electrocoagulation (EC) reactor has been evaluated in batch mode using electrodes of aluminum (Al) and connected to a direct current power supply in a monopolar way. To evaluate the performance of the reactor, a synthetic solution with a concentration similar to that of brackish water was used. A factorial design was applied to investigate the influence of the electrical potential applied to the electrocoagulation cell at the levels of 3, 5, 7, and 9 V, and initial calcium hardness of 540.2 and 914.60 mg/L CaCO₃ at room temperature in 60 treatment minutes. The results revealed that the electrical potential applied to the electrocoagulation cell was the most significant factor in hardness removal, within the experimental ranges studied. The results showed that electrocoagulation at an electric potential applied at 9 volts and an initial concentration of 7400 mg/L allowed a higher hardness removal efficiency (25.83%). the pH of the solution increased throughout the process. The energy consumption ranged between 4.43 and 42 kW.h/m³ depending on the conditions of the factors. It has been shown that during the treatment process a layer of dense and compact calcium carbonate precipitate is formed on the surface of the cathode.

This study provides a comprehensive overview of vertical-axis wind turbines (VAWTs) for emerging energy applications by combining a bibliometric analysis and a thematic mini-review. Scopus-indexed publications from 1979 to 2025 were analyzed using PRISMA guidelines and bibliometric tools (Bibliometrix, CiteSpace, and VOSviewer) to map global research trends, and a parallel mini-review distilled recent advances into five thematic areas: aerodynamic strategies, advanced materials, urban integration, hybrid systems, and floating offshore platforms. The results reveal that VAWT research output has surged since 2006, led by China with strong contributions from Europe and North America, and is concentrated in leading renewable energy journals. Dominant topics include computational fluid dynamics (CFD) simulations, performance optimization, wind–solar hybrid integration, and adaptation to turbulent urban environments. Technologically, active and passive aerodynamic innovations have boosted performance albeit with added complexity, remaining mostly at moderate technology readiness (TRL 3–5), while advanced composite materials are improving durability and fatigue life. Emerging applications in microgrids, building-integrated systems, and offshore floating platforms leverage VAWTs’ omnidirectional, low-noise operation, although challenges persist in scaling up, control integration, and long-term field validation. Overall, VAWTs are gaining relevance as a complement to conventional turbines in the sustainable energy transition, and this study’s integrated approach identifies critical gaps and high-priority research directions to accelerate VAWT development and help transition these turbines from niche prototypes to mainstream renewable solutions.

The aim of this bibliometric analysis was to evaluate the evolution of scientific research in hydrogen, focusing on green hydrogen production, storage, and utilization. Articles from prominent databases were analyzed, revealing a strong emphasis on sustainable hydrogen technologies through keywords like “hydrogen production”, “green hydrogen”, and “solar power generation”. Mature research areas include production methods and electrolysis, while emerging topics such as energy efficiency and policy are gaining traction. The most-cited papers, from Energy Conversion and Management to the International Journal of Hydrogen Energy, cover techno-economic assessments and case studies on deploying hydrogen technologies. Key findings highlight the variability of the Levelized Cost of Hydrogen (LCOH) across technologies and regions. Deep learning applications, including Fast Fourier Transform-based forecasting and explainable AI models, are transforming production optimization, while Life Cycle Assessment (LCA) emphasizes renewable energy’s role in reducing carbon intensity and resource consumption. Diverse strategies, such as fiscal incentives for wind energy and use of urban waste, underline the importance of local solutions. This analysis reflects the rapid growth of hydrogen research, driven by international collaboration and innovations in sustainable production, storage, and optimization. It is hoped that this paper will help to shed more light on the current and future understanding of green hydrogen.

Vinasse is acidic, dark brown wastewater obtained as a residue from the alcohol distillation process, the main component of which is water, in addition to mineral nutrients and a high organic load. Electrocoagulation (EC) is a technology that generates coagulating substances in situ by oxidizing sacrificial anodes through an electric current applied to the electrodes. During the last decade, the electrocoagulation process has been intensively investigated in several reviews, due to its ease of operation, versatility, sustainability and low environmental impact. The objective of the present work has been to make a general review of the EC process, its principle, reaction mechanism and operating parameters involved in the electrocoagulation process. In this research, the PRISMA method was used for the analysis of articles from different databases such as Scopus, ScienceDirect and Google Scholar. This review collects numerous studies of the EC process in stillage wastewater treatment and makes a comparison between these experimental results mainly in terms of chemical oxygen demand removal. In addition, this review makes a comprehensive analysis of EC coupled to other processes, taking into account their operating parameters and stillage contaminant removal efficiency. The conclusion of this research points out that electrocoagulation coupled with other treatment processes is very necessary because it reduces energy consumption and increases the rate of pollutant removal from wastewater.

Hydrogen, as a clean energy source, has enormous potential in addressing global climate change and energy security challenges. This paper discusses different hydrogen production methodologies (steam methane reforming and water electrolysis), focusing on the electrolysis process as the most promising method for industrial-scale hydrogen generation. The review delved into three main electrolysis methods, including alkaline water electrolysis, proton exchange membrane electrolysis, and anion exchange membrane electrolysis cells. Also, the production of hydrogen as a by-product by means of membrane cells and mercury cells. The process of reforming natural gas (mainly methane) using steam is currently the predominant technique, comprising approximately 96% of the world’s hydrogen synthesis. However, it is carbon intensive and therefore not sustainable over time. Water, as a renewable resource, carbon-free and rich in hydrogen (11.11%), offers one of the best solutions to replace hydrogen production from fossil fuels by decomposing water. This article highlights the fundamental principles of electrolysis, recent membrane studies, and operating parameters for hydrogen production. The study also shows the amount of pollutant emissions (g of CO₂/g of H₂) associated with a hydrogen color attribute. The integration of water electrolysis with renewable energy sources constitutes an efficient and sustainable strategy in the production of green hydrogen, minimizing environmental impact and optimizing the use of clean energy resources.

This study presents a scientometric analysis of renewable energy applications in low-temperature regions, focusing on green hydrogen production, carbon storage, and emerging trends. Using bibliometric tools such as RStudio and VOSviewer, the research evaluates publication trends from 1988 to 2024, revealing an exponential growth in renewable energy studies post-2021, driven by global policies promoting carbon neutrality. Life cycle assessment (LCA) plays a crucial role in evaluating the environmental impact of energy systems, underscoring the need to integrate renewable sources for emission reduction. Hydrogen production via electrolysis has emerged as a key solution in decarbonizing hard-to-abate sectors, while carbon storage technologies, such as bioenergy with carbon capture and storage (BECCS), are gaining traction. Government policies, including carbon taxes, fossil fuel phase-out strategies, and renewable energy subsidies, significantly shape the energy transition in cold regions by incentivizing low-carbon alternatives. Multi-objective optimization techniques, leveraging artificial intelligence (AI) and machine learning, are expected to enhance decision-making processes, optimizing energy efficiency, reliability, and economic feasibility in renewable energy systems. Future research must address three critical challenges: (1) strengthening policy frameworks and financial incentives for large-scale renewable energy deployment, (2) advancing energy storage, hydrogen production, and hybrid energy systems, and (3) integrating multi-objective optimization approaches to enhance cost-effectiveness and resilience in extreme climates. It is expected that the research will contribute to the field of knowledge regarding renewable energy applications in low-temperature regions.