Cold thermal energy storage supports sustainable cooling by allowing cold production and use to occur at different times, but slow solidification can restrict charging within available operating periods. This study investigates the effects of metal foam, hybrid nanoparticles, and radiative heat transfer on solidification in an enclosure with a circular cold wall and three radial fins, aiming to identify which measures most effectively shorten charging time. A transient finite element model was solved using the Galerkin method and implicit time discretization. The nanoparticle suspension was represented as a homogeneous medium, and variations in porosity, nanoparticle volume fraction, and the radiation parameter were examined through temperature distributions, solid fraction evolution, and complete solidification time. Reducing the porosity from 1 to 0.95 shortened the solidification time by approximately 81.9%. Nanoparticle addition and modeled radiative heat transfer yielded reductions of 6.54% and 8.94%, respectively, in their corresponding comparisons. Applying all three measures reduced the complete solidification time from 7742.8 to 1276.14 s, corresponding to a reduction of approximately 83.52%. Within the investigated comparisons, foam incorporation produced the largest reduction in complete solidification time, while nanoparticle addition and modeled radiative transfer produced smaller reductions. These findings identify the modifications that most strongly affect charging time in the studied enclosure and inform the selection of heat transfer measures for phase change storage in sustainable cooling applications.

Renovating hospital support buildings requires balancing reductions in fossil-fuel use against capital expenditure and operational constraints. This study examines the energy and investment trade-offs among renovation scenarios for an existing hospital support building. An annual energy model was reconstructed from available engineering estimates for the Technical-Economic Block (TEB) of the University Clinical Centre of the Republic of Srpska in Banja Luka. Envelope renovation, boiler replacement and solar thermal installation were combined into seven scenarios. Primary-energy savings, operational CO$_2$ reductions, investment and fuel-cost savings were compared. Preference Selection Index (PSI) rankings were calculated using four criteria and a reduced two-criterion formulation, followed by an analysis of alternative investment weights. The three-measure package achieved the largest estimated primary-energy savings, at 1.813 GWh/year, and ranked first under both PSI formulations. However, boiler replacement alone ranked first when energy savings and investment received equal weights. Envelope renovation combined with boiler replacement retained 98.1% of the three-measure package’s energy savings at 12.9% lower investment. Adding solar thermal required a further 322,337 Bosnia and Herzegovina convertible marks (BAMs) and produced estimated annual fuel-cost savings of 4,409 BAM, giving an incremental simple payback of 73.1 years. Estimated operational CO$_2$ reductions reached 454.5 tonnes/year using a conversion factor inferred from the source scenario data. These findings distinguish maximum energy savings from investment preference and marginal financial returns. The assessment supports preliminary renovation comparisons, while its absolute estimates remain conditional on verification of the baseline and engineering inputs.

Nitrogen oxide emissions from gas turbines at natural gas compressor stations pose a local environmental challenge to the sustainable operation of energy infrastructure. This study assesses nitrogen oxide dispersion around the Marand natural gas compressor station in northwestern Iran to identify candidate areas for ambient monitoring. Stack measurements from three natural gas-fired turbines were compiled to characterize nitric oxide (NO), nitrogen dioxide (NO$_2$), and total nitrogen oxides (NO$_x$). Meteorological data were processed using American Meteorological Society/Environmental Protection Agency Regulatory Model Improvement Committee Meteorological Preprocessor (AERMET), and dispersion was simulated using the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD). Maximum 1-hour and 24-hour concentrations were compared together with their receptor coordinates and occurrence times. The predicted maximum 1-hour concentrations of NO, NO$_2$, and NO$_x$ were 90.50, 5.07, and 91.72 μg/m$^3$, respectively; the corresponding maximum 24-hour concentrations were 11.56, 0.88, and 11.71 μg/m$^3$. The hourly peak receptors were closely grouped, whereas the daily NO$_2$ and NO$_x$ peak receptors were approximately 0.70 km from their respective hourly peak locations. The NO peak receptor remained unchanged between averaging periods. These results indicate that selecting monitoring locations from an hourly maximum alone may overlook locations associated with the highest daily concentrations. Joint interpretation of peak magnitude, location, and timing identifies candidate monitoring areas and provides information relevant to the environmental management and sustainable operation of natural gas transmission infrastructure.

Effective thermal management is essential for the reliable operation of lithium-ion batteries (LIBs) in electric vehicles (EVs) and other energy storage applications. In cylindrical cells, anisotropic thermal conductivity makes it difficult to maintain a uniform internal temperature, particularly under air-cooling conditions. This study investigates the effects of annular cooling fins with different radius distributions on the thermal performance and internal temperature uniformity of a cylindrical LIB. A three-dimensional transient electrochemical–thermal model was developed in COMSOL Multiphysics, coupling a one-dimensional pseudo-two-dimensional (P2D) electrochemical model with heat transfer and airflow simulations. Five annular fin configurations were evaluated against a finless design under forced-air cooling conditions. The numerical model was validated against published experimental measurements of cell voltage and surface temperature. The results showed that all fin configurations reduced the maximum cell temperature and internal temperature difference compared with the finless design. The uniform-radius configuration produced the lowest maximum temperature, whereas the increasing-radius configuration achieved the most uniform internal temperature distribution. Compared with the uniform-radius configuration, the increasing-radius design reduced the average maximum intra-cell temperature difference by 5.8%, fin material consumption by 37.5%, and airflow pressure drop by approximately 15%. These findings indicate that the distribution of annular fin radii plays an important role in balancing heat dissipation, internal temperature uniformity, and aerodynamic resistance. The study provides a practical basis for the design of air-cooled thermal management systems for cylindrical LIBs.