This review of the current literature highlights the barriers present within cavities and their contribution to heat dissipation and cooling of various activities. This study shows a set of factors that affect the function of the obstacle (shape, length, size, thickness, and location of the obstacles). The variation in boundary conditions between obstacles and cavity walls has opened up broad horizons for scientific research in the field of heat transfer (HT) and fluid flow. Despite significant progress, research gaps remain. Most previous studies have focused on simple shaped obstacles within cavities with uniform boundaries. There is a distinct lack of studies exploring the effect of complex such as U/L/H shapes or orientable obstacles within complex cavities or under dynamic conditions such as non-uniform heating or varying magnetic fields. It was found that the Nusselt number increased by 15.56% depending on the shape of the internal obstacle, which gives an advantage to some obstacle shapes over others and highlights the importance of choosing the obstacle and cavity shape so that the best HT is obtained. This study is the first to compare simple and complex shapes of obstacles, and this is the innovative point of this review.

This study presents the development and performance evaluation of a photoelectrochemical (PEC) cell designed for sustainable hydrogen production, emphasizing a cost-effective and reproducible approach to clean energy generation. The PEC system was fabricated using an n-type TiO$_2$ photoanode and Pt cathode in an aqueous Na$_2$SO$_4$ electrolyte (0.5 M), operating under simulated solar irradiation of 100 mW/cm$^2$ (AM 1.5 G) within a controlled temperature range of 25–45 ℃. Experimental testing demonstrated that the system sustained hydrogen evolution through an automated electrolyte refilling and pump control mechanism, achieving 51% H$_2$ saturation within an average of 2.8 seconds over 172 activation cycles, indicating responsive system logic. However, prolonged operation led to efficiency decline, with pump activation time extending to 833 seconds and only 56% hydrogen recovery, signifying material and control degradation. The temperature monitoring subsystem malfunctioned, registering persistent –127 ℃ readings, which impeded accurate thermal regulation and safety evaluation. Sensor drift and inconsistent pump actuation were also observed, reflecting calibration deficiencies. Three operational phases were identified—initial instability (0–300 s), stabilization (300–600 s), and performance degradation ($\geq$800 s). Overall, while the PEC system demonstrates promising short-term hydrogen generation efficiency under defined light and electrolyte conditions, long-term stability remains constrained by electrode durability, thermal control accuracy, and system integration challenges, requiring further optimization for sustained hydrogen production.

Carbon dioxide emissions from power plants and industrial producers are a major driver of global warming, leading to rising temperatures and numerous adverse impacts on ecosystems and human life. In response, various strategies have been developed to mitigate greenhouse gas emissions. This review paper examines the three main stages of energy conversion for carbon dioxide capture: pre-combustion, oxy-fuel combustion, and post-combustion, with particular emphasis on the latter. Several capture techniques have been explored, including chemical and physical absorption, membranes, adsorption on porous materials, and cryogenic freezing. Among these, membrane-based methods have attracted significant attention due to their advantages in energy efficiency, operational simplicity, and potential integration with hybrid systems. Comparing the efficiency of different capture technologies, membranes achieve 85–90% efficiency at a lower cost (\$25–45/ton CO$_2$), while deep cooling technology boasts high purity ($>$99%) but comes at the cost of high energy consumption ($>$3.5 GJ/ton CO$_2$). Absorption technology, on the other hand, ranges between 90–95% efficiency at a cost of \$40–60/ton CO$_2$. Membranes have been successfully combined with absorption, desorption, and cryogenic processes to achieve higher purity in CO$_2$ capture. This study reviews twenty research papers on membrane technology, focusing on hybrid membrane systems and their performance. Carbon capture and storage (CCS) is widely recognized as a key strategy for achieving climate goals by reducing carbon emissions from thermal energy production and industrial processes, while also enabling the net removal of CO$_2$ from the atmosphere.

This research examines The Electron Energy Distribution Function (EEDF) of electrons in plasma discharge for (CHF$_3$-He) gas combinations. The Fortran programming language was used to solve the Boltzmann equation. A two-term approximation was used to solve the Boltzmann transport equation for both pure gases and mixtures. Using this method of solution, the electron energy distribution function was computed, and electric transport parameters were evaluated with range of E/N varying from (10–600) Td. The electron energy distribution function of the CHF$_3$-He gas mixture is nearly Maxwellian at E/N values (10–20) Td, the distribution function is non-Maxwellian when E/N is raising. Also, the energy values of the mixtures largely depend on the transport energy between electron and molecule through collisions. In compared to mixtures, Helium gas has a high energy characteristic. At higher helium ratios, the mean electron energy to mixture is increasing. The mean electron energy in a gas mixture (35% CHF$_3$ + 65% He) and the behavior variation in electron mobility at this ratio both have larger values than other ratios.

This study introduces a new framework, PACBDHTE, designed to evaluate materials for fusion reactor applications. To provide an integrated assessment that encompasses radiation damage, hydrogen behavior, transmutation effects, and material erosion within a unified evaluation scheme. The methodology includes evaluation Displacement per Atom (DPA) calculations, hydrogen retention analysis, transmutation assessments, and erosion rate determinations. The results identified SiC and WC-Be are strong candidates due to their exceptional hydrogen retention capabilities. Tungsten-based materials are competitive, but careful consideration is needed for 316L stainless steel due to lower hydrogen retention. additionally, Cu(I)-functionalized metal–organic frameworks (MOFs), such as Cu(I)-MFU-4l, show promising selectivity for hydrogen isotope separation which can support more efficient fusion fuel-cycle management. Overall, the findings highlight erosion rates are critical for material longevity, emphasizing the need for continuous monitoring. Overall, the study contributes to safe and efficient fusion energy technology.

Mini hydropower plants (MHPs) play a vital role in providing sustainable electricity to off-grid rural communities in Indonesia. This study optimizes the hydraulic performance of the penstock system for the Way Melesom MHP in Pesisir Barat, Lampung. Using a conservative design discharge of 0.822 m³/s, derived from the F.J. Mock rainfall–runoff model and Flow Duration Curve (Q₇₀) analysis, hydraulic modeling was conducted using the Darcy–Weisbach and Hazen–Williams equations for four pipe diameters (DN400–DN700). The results show that increasing the pipe diameter reduces headloss and increases net head and power output, with diminishing efficiency gains beyond DN600. The DN600 configuration achieves an optimal balance—yielding a velocity of 2.91 m/s, headloss of 3.45 m, and a net head of 61.81 m, corresponding to an estimated output of 0.45 MW (2.76 GWh/year). This capacity can supply electricity to approximately 2,300 rural households, or up to 3,000 customers (450 VA each), supporting 10–12 small villages under an off-grid distribution network. The analysis confirms that DN600 provides the best technical–economic trade-off, recovering 95% of the gross head (65.26 m) with 90% hydraulic efficiency. The study highlights the importance of integrating hydrological, hydraulic, and energy modeling for optimizing closed-conduit systems in small-scale hydropower, ensuring both engineering efficiency and sustainable rural electrification.

Integration of renewable energy and waste heat resources could effectively reduce emissions and the production cost in methane production power plants. The objective of this study is to conduct a technoeconomic analysis of an Iraqi methanol production facility using a combination of energy resources of waste gas from Al-Fallujah white cement factory, solar and wind energy. It is hypothesized that the carbon dioxide present in the flue gas could be extracted using solar and wind turbine energy in a carbon capture unit in the hydrogen plant. Methanol fuel is then produced in the methanol plant from the combined sources. The amount of energy and the number of solar panels or wind turbines (WT) needed to supply this energy requirement were estimated using the Engineering Equation Solver (EES), and then the environmental impact of the methanol plant was assessed. The efficiencies of renewable energy PV, WT, methanol plants, and methanol fuel were predicted as 21%, 35%, 16.26%, and 58.72%, respectively. The electrolyzers’ efficiency was 78.2% at their ideal density of 2.2 kA/m$^2$. With a production capacity of 34,530 million tons of methanol, the total cost to operate the plant for 30 years for each of the PV plants and WT was found to be \$9.46 billion and \$5.291 billion, respectively. This translates to 0.4131 \$/kg methane for the PV plant and 0.2413 \$/kg methane for the wind power plant. In terms of the environment, there is a daily 3,894 tons of collected CO$_2$ emissions and 3,306 tons of mitigation. The results show that the current facility can compete with facilities that produce clean synthetic fuel.

Given the extreme scarcity of water in arid regions, innovative solutions are essential to provide potable water. Among these solutions, solar desalination technology stands out, using sunlight to evaporate saltwater and then condense it to convert it into fresh water. However, conventional solar desalination systems face challenges related to production efficiency, which is affected by factors such as solar radiation intensity, wind speed, and temperature. This research aims to improve the efficiency of these systems using mesh cotton. Studies have shown that mesh cotton absorbs more sunlight, increasing the evaporation rate, while wood acts as a thermal insulator and enhances the system's efficiency. The experiment revealed a 37% increase in water production from the improved distillate. The conventional system produced 1,300 ml of distilled water per day, while the improved system produced 1,742 ml per day. These improvements indicate that the use of readily available materials can significantly improve the efficiency of solar desalination systems, helping address water scarcity in arid regions.