Amid persistent environmental pressures linked to energy dependence and structural inefficiencies, this study represents one of the first empirical attempts to concurrently investigate the effects of renewable energy, green technology, environmental taxes, economic growth, energy imports, and government effectiveness on greenhouse gas emissions (GHGE) using data updated through 2024 for Nigeria’s evolving economy. Using the “Autoregressive Distributed Lag” (ARDL) approach with “Granger causality” analysis, the results confirm a stable long-run association between the indicators. Renewable energy and energy imports indicate a negative correlation with GHGE in both the near and long term, supporting Nigeria’s low-carbon transition. Economic growth reduces emissions in the near term but shows no significant long-run effect. Environmental taxes exhibit a weak positive association with emissions, reflecting enforcement and institutional limitations, while green technology and government effectiveness show negative but insignificant impacts. The causality findings reveal unidirectional links from environmental taxes to emissions and from emissions to government effectiveness. The results highlight the importance of strengthening renewable energy, diversifying energy sources, and enhancing institutional capacity to achieve sustainable environmental outcomes in Nigeria.
The development of high-efficiency copper indium gallium diselenide (CIGS) solar cells is currently driven by a dual strategy of internal structural refinement and integration into multi-junction tandem architectures. This study aims to systematically analyze the key design and optimization strategies required to overcome the 33.7% Shockley–Queisser limit of single-junction devices. The results demonstrate that bandgap engineering, particularly through double-graded “notch” profiles, significantly enhances charge carrier collection and improves overall device performance, while alkali metal post-deposition treatments effectively reduce interface recombination losses. Furthermore, integrating CIGS with perovskite top cells in two-terminal (2T) and four-terminal (4T) configurations is a promising pathway to achieving efficiencies exceeding 30%. By combining advanced vacuum-based fabrication techniques, such as the three-stage co-evaporation process, with precise optical management, CIGS technology is positioned as a versatile candidate for both high-performance terrestrial and radiation-tolerant space applications.
Dispersion in porous media is a multiscale process that governs the distribution and mixing of fluids in the subsurface. In underground hydrogen storage, dispersion is particularly critical due to hydrogen’s low molecular weight and large density contrast relative to natural gas. In addition to this, cyclic operations amplify mixing and transport effects beyond what is typically observed during conventional gas injection and storage. The apparent mixing observed during storage arises from the combined influences of localized dispersion, heterogeneity-driven channeling, and gravity segregation. Distinguishing between local, echo, and transmission dispersion provides a start for understanding reversible and irreversible components of mixing, and for connecting localized processes with field-scale performance. This study develops a systematic method to quantify dispersion in hydrogen storage within depleted gas reservoirs by combining analytical solutions of the convective–diffusive equation with multidimensional numerical simulations. The approach translates concentration fields into effective dispersion coefficients using different methods for mixing-zone length analysis. This enables evaluation across different permeability distributions, anisotropies, and spatial correlation lengths. The method is applied under both linear and radial flow conditions, including cyclic injection and production, to capture the distinct roles of gravity segregation, heterogeneity, and boundary conditions. Across the studied cases, the effective dispersion coefficient increases from approximately 1.03 to 3.5 m2/day as the Dykstra–Parsons coefficient increases from 0.3 to 0.9. Gravity segregation significantly alters plume evolution, reducing effective mixing zone lengths and introducing asymmetric displacement behavior. Under cyclic radial injection–production, incomplete plume reversal leads to persistent concentration halos, indicating irreversible mixing. The ratio of echo to transmission dispersion further quantifies the degree of irreversibility in the system. This work establishes a quantitative framework for characterizing dispersive transport in hydrogen storage systems and provides a basis for evaluating storage performance and reversibility under realistic subsurface conditions.
