Fixed photovoltaic systems suffer from reduced irradiance capture and temperature-induced efficiency losses. This study presents the design, experimental evaluation, and numerical modeling of a water-cooled single-axis tracking photovoltaic-thermal system under tropical climate conditions. The system integrates east-west solar tracking with rear-surface water cooling to improve irradiance capture, regulate photovoltaic temperature, and recover useful heat. Outdoor experiments were conducted using a fixed photovoltaic panel as the reference system, and a semi-empirical model was developed and validated using independent test days. Results showed that the tracking system improved irradiance capture, with off-peak irradiance gain reaching 34.6%. The tracking photovoltaic-thermal system maintained surface temperatures within 38.6-60.5 degrees C under irradiance levels of 91.75-1090 W/m2. The system achieved peak electrical, thermal, and gross combined efficiencies of 11.9%, 70.42%, and 82.22%, respectively. After deducting the 5 W cooling-pump demand, the peak combined efficiency remained 76.72%. Second-law analysis showed a peak exergy efficiency of 12.82% and maximum entropy generation rate of 0.244 W/K. Model validation showed strong outlet water temperature prediction, with root mean square error below 0.08 degrees C, mean absolute percentage error below 0.20%, and coefficient of determination above 0.96. Combined efficiency was predicted with root mean square error of 1.48-3.62% and mean absolute percentage error of 1.90-4.58%. Break-even analysis showed that the additional electricity generation required to recover the added tracking and cooling cost decreased from 293.09 kWh/year at a 5-year recovery period to 94.28 kWh/year at a 25-year recovery period. The corresponding net carbon dioxide mitigation decreased from 211.48 to 64.37 kg CO2e/year over the same period. These results confirm that integrating singleaxis tracking with rear-surface water cooling improves photovoltaic-thermal performance under variable tropical outdoor conditions.
The low thermal conductivity of phase change materials (<0.5 W∕m K) restricts heat spreading and limits thermal regulation. Fins can alleviate this by providing conductive pathways, but achieving enhanced thermal performance without adding significant BTMS mass remains a key design challenge. This study develops and optimizes a fin-enhanced PCM BTMS for a cylindrical 18650 cell using paraffin RT-44HC and evaluates fin topology effects under 5C discharge. Three conventional fin types (longitudinal, circular, and pin fins) are first compared, and two hybrid fin concepts are then proposed based on the observed heat-transfer mechanisms. A transient three-dimensional CFD model is established in ANSYS Fluent using the enthalpy-porosity method with buoyancy effects and is validated against experiments. Results show that fin geometry remains decisive even at equal mass. Relative to PCM-only cooling, mean temperature reduction reaches 8.07°C (longitudinal), 10.52°C (circular), and 11.49°C (pin fins), and the time to reach 45°C increases from 250 s to 575–900 s depending on fin type. Among hybrid designs, the circular-pin configuration yields the lowest temperatures and best uniformity, maintaining a maximum surface temperature difference below 1°C and promoting more uniform melting. Parametric optimization identifies an optimal pin diameter of 2 mm and an optimal number of pin fins at 204 based on thermal performance index results. At the thermal control point, the optimized hybrid design reduces thermal resistance by up to 2 K/W relative to PCM-only, lowers maximum temperature by up to 16.56°C, and extends operation within the optimal temperature limit by up to 1175 s.
The aviation sector is essential for global connectivity and economic growth but remains one of the most difficult industries to decarbonize due to its reliance on energy-dense liquid fuels and the anticipated increase in both carbon dioxide (CO2) and non-CO2 climate impacts. As the industry pursues net-zero emissions by 2050, Sustainable Aviation Fuels (SAFs) have emerged as the most practical near- and medium-term decarbonization pathway because they are compatible with existing aircraft and fuel infrastructure. However, uncertainties persist regarding the sustainability, scalability, economic viability, and long-term climate benefits of different SAF production routes. This review provides a comprehensive assessment of SAFs by integrating feedstock availability, conversion technologies, fuel properties, life-cycle greenhouse gas (GHG) emissions, techno-economic performance, and future deployment prospects within a unified sustainability framework. Major SAF pathways, including Oil-to-Jet (OTJ), Gas-to-Jet (GTJ), Alcohol-to-Jet (ATJ), and Sugar-to-Jet (STJ), are critically evaluated, with particular focus on ASTM D7566-certified fuels such as Fischer–Tropsch Synthetic Paraffinic Kerosene (FT-SPK), Hydroprocessed Esters and Fatty Acids (HEFA-SPK), and Hydroprocessed Algae-Based Fuels (HC-HEFA). Comparative analysis reveals significant differences in feedstock requirements, process efficiencies, production costs, fuel composition, and scalability. Life-cycle assessment (LCA) studies indicate GHG emission reductions ranging from 60% to over 100% relative to conventional jet fuel, with FT-SPK and FT-SPK/A offering the highest mitigation potential. Feedstock cultivation, resource extraction, and fuel conversion are identified as the most emission-intensive stages, underscoring the need for upstream process optimization. The review further examines critical barriers to large-scale SAF deployment, including feedstock scarcity, supply variability, high energy and hydrogen requirements, infrastructure constraints, and high production costs. While HEFA dominates current commercialization, scalable aviation decarbonization will require accelerated deployment of FT, ATJ, and Power-to-Liquid (PtL) pathways, supported by technological innovation, sustainable feedstock expansion, and enabling policies.
Biodegradation of phenol from wastewater coupled with biohydrogen production using immobilized microalgae is a promising approach to produce green energy. This study investigated the environmental impacts and energy performance of dark fermentative biohydrogen production in phenol-containing wastewater using immobilized microalgae-alginate beads. A life cycle assessment was conducted with cradle-to-gate mode via using the global ReCiPe 2016 v1.1 method at both midpoint and endpoint levels in SimaPro 9.3.0.2. The results revealed that the production process of biohydrogen was the primary contributor to all environmental impacts, which was mainly due to the high electricity consumption. In contrast, microalgae cultivation and harvesting had minimal environmental impacts, suggesting that this stage required low inputs in terms of energy, chemicals and water. Similar trends were also observed in both normalized midpoint impacts and endpoint impacts, in which supporting the reliability of discovered environmental hotspots. Nevertheless, the net energy ratio (NER) attained was 1.33, indicating a net energy gain and supporting the energy efficiency amidst overall production processes. In addition, the reuse of immobilized microalgae-alginate beads and utilization of phenol-containing wastewater as feedstock for dark fermentation could greatly reduce the amount of chemicals input and energy demand. The findings highlighted by combining treatment of phenol with biohydrogen production using immobilized microalgae-alginate beads could promote both green energy production as well as sustainable method for wastewater treatment simultaneously.
This study addresses the challenge of improving the mechanical and durability properties of lightweight concrete made with waste plant-based aggregates, specifically oil palm shell (OPS) species dura and tenera, which inherently exhibit low strength and durability due to absorption and weak aggregate-matrix bonding. The objective is to explore surface modification techniques—grout-treated soaking (TS) and treated spray coating (TSC)—applied with different water-to-cementitious (w/c) ratios (0.7, 0.9, and 1.1) in a wet grout binder to enhance these properties. Experimental investigations compare raw and surface-modified LWPA concretes by evaluating compressive strength, splitting tensile resistance, flexural durability, elastic modulus, porosity, and rapid chloride penetration test (RCPT) results. The surface treatments lead to a modest increase in specimen density, while significant enhancements in slump values are observed, with treated spray coating and soaking aggregates showing nearly 40
