This study highlights how the analysis of the long-term performance of solar reflective materials used both as roofing and flooring solutions to mitigate urban overheating has recently become more important. European and Italian legislations focus just on initial properties, but actual energy efficiency depends on durability over time. The objective is the development and the validation of characterization methodologies that consider performance degradation due to aging, providing reliable guidance for designers and policy makers. This study integrates standard thermophysical characterization methods with natural and accelerated aging protocols. Solar reflectance (SR) measurements can be performed by using ultraviolet-visible-near-infrared spectrophotometer, solar spectrum reflectometer and pyranometer/albedometer, while thermal emissivity can be measured with infrared emissometers. Natural aging was implemented at the Energy Efficiency Laboratory structure of the University of Modena and Reggio Emilia, operational since 2017. Accelerated methods include the standard protocol for surface soiling and an innovative method for biological growth. The analysis reveals significant degradations in SR, with reductions of between 10% and 40% after three years of natural exposure. Bituminous membranes show the most marked degradation, while ceramic materials present the best stability. Accelerated methods show interesting correlations with natural aging. The doubling of the standard accelerated cycle, designed on North American climatic conditions, is more representative of European climatic conditions characterized by greater air pollution. It must be recalled that evaluation based just on initial performance significantly underestimates long-term behaviour. The results suggest the need to update regulations by introducing requirements based on post-ageing performance. New materials design should be focus on durability by integrating into new materials both self-cleaning properties and improved stability over time. While, during design process, materials with certified long-term stability, analyzed through durability and degradation analysis should be considered in energy and economic assessments.

Repurposing deep abandoned oil and gas wells for advanced adiabatic compressed air energy storage (AA-CAES) has attracted increasing attention; however, reliable performance assessment is challenged by the complex thermal behaviour induced by the large aspect ratio of deep wells and the long-term interaction between the gas column and surrounding formations. In particular, simplified heat transfer assumptions commonly adopted in existing models may lead to non-negligible deviations in capacity and efficiency predictions. To address this issue, a coupled thermodynamic framework is established that accounts for gas column gravity effects, geothermal temperature gradients, and unsteady heat conduction in the surrounding rock. Different wellbore heat transfer boundary representations and operational strategies are systematically examined to clarify their influence on the thermal and energetic performance of deep-well AA-CAES systems. The analysis indicates that under low mass flow rate conditions, the extended wellbore length promotes effective heat exchange between the compressed air and the surrounding rock, restricting the average temperature variation along the wellbore and leading to compression and expansion processes that deviate markedly from ideal adiabatic behaviour. When a constant wall temperature boundary is employed to represent long-term formation heat transfer, the predicted storage capacity is reduced by 6.12% compared with conventional adiabatic assumptions. In addition, sliding-pressure operation exhibits superior adaptability to the thermal characteristics of deep wells, increasing the round-trip efficiency (RTE) from 48.82% to 60.99 relative to constant-pressure operation. At low flow rates, extended thermal relaxation further enhances heat dissipation, resulting in a modest increase in effective energy storage density (ESD). These results highlight the role of surrounding rock formations as a distributed thermal buffer and underscore the importance of incorporating realistic heat transfer modelling and appropriate operational strategies in the thermodynamic design of deep-well AA-CAES systems.

The combustion behavior of blended petroleum–biofuel mixtures has increasingly been investigated as interest grows in low-toxicity, biodegradable, and energy-dense biomass-derived fuels. Among higher alkanols, n-butanol is recognized for its favorable physicochemical properties and its compatibility with gasoline-range hydrocarbons (HC) such as iso-octane. In this context, a systematic evaluation of laminar flame propagation and instability characteristics is essential for understanding the combustion performance and operational safety of blended fuels. In the present study, the laminar burning velocity (LBV) and cellular instability of premixed iso-octane/n-butanol/air flames were quantified for a wide range of equivalence ratios (0.7–1.5) at an initial temperature of 423 K and ambient pressure. It was observed that the LBV increased consistently with the addition of n-butanol, whereas the Markstein length (L_b) decreased. Analysis of cellular structures revealed that diffusive-thermal instability strengthened monotonically as the equivalence ratio increased, resulting in more unstable flame propagation under fuel-rich conditions. In contrast, the hydrodynamic instability exhibited a non-monotonic trend, first intensifying and subsequently diminishing with increasing equivalence ratio. The critical Peclet number decreased continuously across the equivalence-ratio range, while the critical flame radius varied non-monotonically. The incorporation of n-butanol was found to enhance both diffusive-thermal and hydrodynamic instabilities and to reduce the critical Peclet number and critical flame radius. These findings underscore the need for careful control of combustion stability in practical applications involving iso-octane/n-butanol mixtures and provide fundamental insight into the flame-structure evolution associated with next-generation alternative fuels.