Floating photovoltaics (FPV) represent a rapidly expanding deployment pathway, offering land-use advantages and distinct thermal and optical conditions relative to ground-mounted systems. Inland FPV installations, however, are constrained by the limited surface area of water bodies, making configuration choice and area-use efficiency critical design parameters. Despite the emergence of various FPV geometries, such as gable east-west layouts and floating single-axis trackers, there remains a lack of comparative performance benchmarks to guide configuration selection. This study conducts a comprehensive evaluation of three bifacial FPV configurations, south-oriented fixed (S-bFPV), east-west gable (EW-bFPV), and horizontal-axis tracking (HAT-bFPV), under identical approximate to 1 MWp and Mediterranean climatic conditions. Long-term field measurements are combined with a calibrated thermal-electrical model implemented in the System Advisor Model (SAM) to assess annual and seasonal energy yield, thermal behavior, and energy density. Results show that the HAT-bFPV configuration yields 1967.44 MWh annually, outperforming the fixed system by 12% and reaching seasonal gains of up to 30%, whereas the EWbFPV layout produces 13.8% less energy. In contrast, energy density favors the EWbFPV design, achieving annually 2908.15 MWh/ha-44% and 37% higher than SbFPV and HAT-bFPV, respectively. All configurations exhibit similar performance ratios (similar to 0.90), while the HAT-bFPV system experiences higher array capture losses during summer. These benchmarks provide actionable insights for FPV design selection, highlighting the trade-offs among tracking performance, spatial efficiency, and thermal behavior under real operating conditions.
Against the backdrop of the deep integration of clean energy and hydrogen production via water electrolysis, this study proposes a swirl pulverized-coal and hydrogen co-firing burner featuring the capability for online, flexible adjustment of both inner and outer secondary air swirl intensities, aiming for achieving low-carbon operation and flexible combustion control. Recognizing that central hydrogen injection into the core high-temperature recirculation zone enhances ignition and flame stability, this study investigates four representative central hydrogen blending schemes: a single-tube jet (Case 2), a two-layer small-orifice axial jet (Case 3), a two-layer small-orifice outward-expanding jet (Case 4), and a scheme involving an altered injection position (Case 5). Under a fixed hydrogen blending ratio of 30%, numerical simulations were conducted to systematically compare the flow and combustion characteristics. Results show that central hydrogen doping significantly reshapes the recirculation zone: compared to pure pulverized coal combustion (Case 1), the recirculation zone diameter shrinks to 0.61-0.83 times its original size, the flame elongates, and the peak temperature rises by over 300 K. The two-layer small-orifice jet structure promotes rapid hydrogen-oxygen mixing, thereby accelerating the reaction rates and shifting the high-temperature zone upstream. Although hydrogen doping effectively reduces the oxygen concentration at the furnace outlet and enhances the overall burnout rate, it leads to a significant increase in NO x emissions, reaching a maximum of 910 ppm. Among the schemes, Case 5 demonstrates superior performance in terms of intensifying mixing, shortening flame length, and accelerating reaction rates, yet further optimization with low-NO x control strategies is still required.
Brazil is a global leader in the use of eucalypt for multiple purposes, including charcoal production for energy and metallurgical applications. However, the effects of irrigation regimes on charcoal quality in eucalypt genotypes grown under semiarid conditions remain poorly understood. This study evaluated the energy quality of charcoal produced from the wood of five eucalypt genotypes cultivated under two irrigation regimes (12 and 36 months) in the Brazilian semiarid region. Four trees per genotype were sampled at 11 years of age, and 5.0 cm-thick stem disks were collected at 0 (base), 20, 40, 60, and 80% of the commercial height (minimum diameter of 6.0 cm). Carbonization was performed under controlled laboratory conditions. Physical, chemical, and energy properties of the charcoal were determined, and the data were analyzed using ANOVA and principal component analysis (PCA). Gravimetric charcoal yield ranged from 37.7% to 41.2%, and higher heating value varied between 6784 and 6921 kcal kg-1. Bulk density (350-0.430 kg m-3) was significantly affected by irrigation, with higher values under the 12-month regime. Clones GG680 and GG702 demonstratedsuperior performance, combining high bulk and energy density with low specific consumption, making them suitable for energy and metallurgical uses. PCA indicated that fixed carbon content, higher heating value, and density were key variables for genotype selection. This study provides novel insights by explicitly linking genotypic performance with water management strategies under semiarid conditions, addressing a critical knowledge gap and providing technical support for sustainable forestry.
Solar air heaters (SAHs) are widely used in low-temperature thermal applications; however, the performance of solar air heaters is primarily governed by the effectiveness of heat exchange between the absorber surface and the airflow. In practical systems, this interaction is often weak due to limited momentum exchange in the near-wall region. This study experimentally evaluates the performance and integrated energy, exergy, economic, and environmental (4E) sustainability of a novel serpentine spring-ribbed solar air heater (SR-SAH) that integrates combined turbulence generation and curvature-induced flow redistribution to improve near-wall transport behaviour and air-surface thermal interaction. Three configurations-a smooth duct solar air heater (S-SAH), a serpentine channel solar air heater (SC-SAH), and the proposed SR-SAH-were evaluated through separate experimental runs under identical outdoor conditions, with the smooth configuration used as the reference case over a Reynolds number range of approximately 2.1 & times; 10 & sup3;-1.1 & times; 10(4). The SR-SAH achieved a maximum thermal efficiency of 80.2%, an exergy efficiency of 4.56%, and a thermo-hydraulic performance of about 70.1%. Compared with the smooth configuration, the proposed design improved thermal efficiency by approximately 28.6% while maintaining acceptable hydraulic penalties. Lifecycle indicators further showed reductions of about 40% in both energy and exergy payback periods, indicating improved sustainability performance. These results demonstrate that the hybrid rib-curvature configuration provides measurable improvement in thermal and sustainability performance compared with conventional smooth and serpentine solar air heaters. Further research should focus on detailed flow-field analysis, geometric optimization, and long-term operational evaluation to further improve the effectiveness of hybrid solar air heater designs.
A CFD simulation study of five industrial-scale flow field designs (hereinafter also referred to as layouts) in a high-temperature PEMWE reveals distinct performance and water-deficiency behavior. The results indicate a positive correlation between current density and water concentration, which strengthens as voltage increases. Critical quantitative thresholds are established: when the local correlation coefficient remains below 0.35, no significant water deficiency occurs; between 0.35 and 0.8, current density decreases almost linearly with decreasing water concentration; above 0.8, water concentration falls below 10%, indicating severe local depletion. At 1.7 V, the pin-type flow field achieves the best performance with the lowest correlation coefficient (0.92) among the designs, reflecting superior water-distribution uniformity. Although the pin-type layout maintains a current density of 3464.33 A/m & sup2; at 1.7 V-only 1.0% lower than that of the best-performing serpentine layout (3497.44 A/m & sup2;)-it provides substantially more uniform water distribution. This work establishes the first fine-scale, threshold-based diagnostic framework for local water deficiency in HT-PEMWE. By systematically comparing five industrial-scale layouts under identical high-temperature conditions, we quantify the performance-uniformity trade-off, providing actionable engineering guidance for stack-level flow-field selection.
