Search Results (87)

Photovoltaic–thermal (PVT) technology has attracted considerable attention for its ability to significantly improve solar energy conversion efficiency by simultaneously providing electricity and heat during the day. PVT technology serves a purpose in condensers and subcoolers for passive cooling in refrigeration systems at night. In our previous work, we proposed a switchable film-insulated photovoltaic–thermal–passive cooling (PVT-PC) module to address the structural incompatibility between diurnal and nocturnal modes. However, the performance of the proposed module strongly depends on two key design parameters: the structural height and the vacuum level of the air cushion. In this study, a numerical model of the proposed module is developed to examine the impact of design and meteorological parameters on its all-day performance. The results show that diurnal performance remains stable across different structural heights, while nocturnal passive cooling power shows strong dependence on vacuum level and structural height, achieving up to 103.73 W/m² at 10 mm height and 1500 Pa vacuum, which is comparable to unglazed PVT modules. Convective heat transfer enhancement, induced by changes in air cushion shape, is identified as the primary contributor to improved nocturnal cooling performance. Wind speed has minimal impact on electrical output but significantly enhances thermal efficiency and nocturnal convective cooling power, with a passive cooling power increase of up to 31.61%. In contrast, higher sky temperatures degrade nocturnal cooling performance due to diminished radiative exchange, despite improving diurnal thermal efficiency. These findings provide fundamental insights for optimizing the structural design and operational strategies of PVT-PC systems under varying environmental conditions. Full article

Accurate estimation of erupted lava volumes is essential for understanding volcanic processes, interpreting eruptive cycles, and assessing volcanic hazards. Traditional methods based on Mid-Infrared (MIR) satellite imagery require clear-sky conditions during eruptions and are prone to sensor saturation, limiting data availability. Here, we present an alternative approach based on the post-eruptive Thermal InfraRed (TIR) signal, using the recently proposed VRP_TIR method to quantify radiative energy loss during lava flow cooling. We identify thermally anomalous pixels in VIIRS I5 scenes (11.45 µm, 375 m resolution) using the TIRVolcH algorithm, this allowing the detection of subtle thermal anomalies throughout the cooling phase, and retrieve lava flow area by fitting theoretical cooling curves to observed VRP_TIR time series. Collating a dataset of 191 mafic eruptions that occurred between 2010 and 2025 at (i) Etna and Stromboli (Italy); (ii) Piton de la Fournaise (France); (iii) Bárðarbunga, Fagradalsfjall, and Sundhnúkagígar (Iceland); (iv) Kīlauea and Mauna Loa (United States); (v) Wolf, Fernandina, and Sierra Negra (Ecuador); (vi) Nyamuragira and Nyiragongo (DRC); (vii) Fogo (Cape Verde); and (viii) La Palma (Spain), we derive a new power-law equation describing mafic lava flow thickening as a function of time across five orders of magnitude (from 0.02 Mm³ to 5.5 km³). Finally, from knowledge of areas and episode durations, we estimate erupted volumes. The method is validated against 68 eruptions with known volumes, yielding high agreement (R² = 0.947; ρ = 0.96; MAPE = 28.60%), a negligible bias (MPE = −0.85%), and uncertainties within ±50%. Application to the February-March 2025 Etna eruption further corroborates the robustness of our workflow, from which we estimate a bulk erupted volume of 4.23 ± 2.12 × 10⁶ m³, in close agreement with preliminary estimates from independent data. Beyond volume estimation, we show that VRP_TIR cooling curves follow a consistent decay pattern that aligns with established theoretical thermal models, indicating a stable conductive regime during the cooling stage. This scale-invariant pattern suggests that crustal insulation and heat transfer across a solidifying boundary govern the thermal evolution of cooling basaltic flows. Full article

Urban thermal environments, characterized by the interplay between indoor and outdoor conditions, pose growing challenges in high-density coastal cities. This study proposes a multi-scale, integrative framework that couples a satellite-derived land surface temperature (LST) analysis with microscale building performance simulations to holistically evaluate the high-density urban thermal environment in subtropical climates. The results reveal that compact, high-density morphologies reduce outdoor heat stress (UTCI) through self-shading but lead to significantly higher cooling loads, energy use intensity (EUI), and poorer daylight autonomy (DA) due to restricted ventilation and limited sky exposure. In contrast, more open, vegetation-rich forms improve ventilation and reduce indoor energy demand, yet exhibit higher UTCI values in exposed areas and increased lighting energy use in poorly oriented spaces. This study also proposes actionable design strategies, including optimal building spacing (≥15 m), façade orientation (30–60° offset from west), SVF regulation (0.4–0.6), and the integration of vertical greenery to balance solar access, ventilation, and shading. These findings offer evidence-based guidance for embedding morphological performance metrics into planning policies and building design codes. This work advances the integration of outdoor and indoor performance evaluation and supports climate-adaptive urban form design through quantitative, policy-relevant insights. Full article

Urban green spaces are crucial for regulating microclimates and enhancing human comfort. The study, conducted at Jiyang College of Zhejiang A&F University, investigates the effects of plant communities with diverse canopy structures on campus microclimates and thermal comfort in summer and winter. Data on air temperature (AT), relative humidity (RH), wind speed (WS), and light intensity (LI) were collected over three consecutive sunny days in both summer and winter. Concurrently, plant community structural characteristics, including three-dimensional green biomass (3DGB), canopy density (CD), and sky-view factor (SVF), were measured and analyzed. Quantitative relationships between these plant characteristics and microclimate/thermal comfort indices were evaluated using statistical analyses. The results indicate that, in summer, plant communities produced significant cooling (daily average AT reduced by 2.3 °C) and humidifying effects, and decreased the daily maximum thermal humidity index (THI) by 1 °C compared to control areas without vegetation. In winter, the moderation of temperature and humidity was present but less pronounced, and no statistically significant temperature difference was observed. Communities with larger 3DGB, higher CD, and lower SVF provided more effective shading and improved microclimatic regulation. A regression analysis identified AT as the primary factor influencing outdoor thermal comfort across both seasons. Planting configurations such as “Tree-Shrub-Herb” and “Tree-Small Tree”, as well as the use of broad-crowned shade trees, were shown to be effective in optimizing microclimate and outdoor comfort. Overall, enhancing the vegetation structure may address outdoor thermal comfort requirements in campus environments throughout the year. Full article

This research aims to estimate long-term aerosol radiative effects by combining radiation and Aerosol Optical Depth (AOD) observations in Barcelona, Spain. Aerosol Radiative Forcing and Aerosol Forcing Efficiency (ARF and AFE) were estimated by combining shortwave radiation measurements from a SolRad-Net CM-21 pyranometer (level 1.5) and AERONET AOD (level 2), using the direct method. The shortwave AFE was derived from the slope between net solar radiation and AOD at 440, 675, 879, and 1020 nm, and the ARF was computed by multiplying the AFE by AOD at six solar zenith angles (20°, 30°, 40°, 50°, 60°, and 70°). Clear-sky conditions were selected from all-skies days by a quadratic fitting. The aerosol was classified to investigate the forcing contributions from each aerosol type. The aerosol classification was based on Pace and Toledano’s thresholds from AOD vs. Ångström Exponent (AE). The GRASP inversions were performed by combined AOD, radiation, Degree of Linear Polarization (DoLP) by zenith angles from the polarized sun–sky–lunar photometer and the elastic signal from the UPC-ACTRIS lidar system. The long-term AFE and ARF are both negative, with an increasing tendency (in absolute value) of +24% (AFE) and +40% (ARF) in 14 years. The yearly AFE varied from −331 to −10 Wm⁻²τ⁻¹, and the ARF varied from −64 to −2 Wm⁻², associated with an AOD (440 nm) from 0.016 to 0.690. The three types of aerosols on clear-sky days are mixed aerosols (61%), desert dust (10%), and urban/industrial-biomass burning aerosols (29%). Combined with Gobbi’s method, this classification clustered the aerosols into four groups by AE analysis (two coarse- and two fine-mode aerosols). Then, the contribution of the aerosol types to the ARF showed that the desert dust forcing had the largest cooling effect in Barcelona (−61.5 to −37.4 Wm⁻²), followed by urban/industrial-biomass burning aerosols (−40.4 to −20.4 Wm⁻²) and mixed aerosols (−31.8 and −24.0 Wm⁻²). Regarding the comparison among Generalized Retrieval of Atmosphere and Surface Properties (GRASP) inversions, AERONET inversions, and direct method estimations, the AFE and ARF had some differences owing to their definitions in the algorithms. The DoLP, used as GRASP input, decreased the ARF overestimation for high AOD. Full article

Investigating the urban heat island (UHI) effect and its driving factors is crucial for supporting future climate mitigation actions and human adaptation strategies. Due to the unique climatic characteristics and vulnerable ecological environment of arid and semi-arid regions, it is valuable to detect the UHI effect in cities in these regions, which have not been fully explored yet. Utilizing moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (LST) data from 2010 to 2020, this study quantified the summer, winter, and annual diurnal mean surface urban heat island intensity (SUHII) of 30 cities in the arid and semi-arid regions of northern China and comprehensively investigated the spatio-temporal patterns and drivers of UHI. The results showed that the annual mean daytime SUHII had a significant decreasing trend, and the nighttime SUHII had an increasing trend for these cities between 2010 and 2020. The nighttime SUHII was stronger than the daytime SUHII, and some cities exhibited surface urban cool island (SUCI) phenomena during daytime, especially in winter. It was also found that cities at higher latitudes experienced higher daytime SUHII throughout the year, and that it was more pronounced in winter. The driving factor analysis revealed that daytime SUHII was primarily influenced by the urban area size (UAS), total precipitation (TP), and the differences in white sky albedo (ΔWSA), enhanced vegetation index (ΔEVI), and normalized difference moisture index (ΔNDMI) between urban and suburban areas. Nighttime SUHII was mainly correlated with ΔWSA, ΔEVI, ΔNDMI, and the differences in elevation (ΔDEM) between urban and suburban areas. This indicated that the background climate was a potential driver for the spatial pattern of UHI in this region. As for the nightlight difference between urban and sub-urban areas (ΔNTL), no correlation was observed with neither daytime SUHII nor nighttime SUHII. These findings are promising in providing theoretical support and scientific guidance for formulating sustainable development strategies and mitigating the UHI effects of cities in the arid and semi-arid regions. Full article

Urban green spaces play a crucial role in mitigating the effects of urban microclimates. This study quantitatively explored how the spatial structural parameters of plant communities regulate microclimates during the hot summer in Zhuji City, Zhejiang Province. Field measurements and ENVI-met simulations were conducted to evaluate the microclimatic effects of different plant communities, including broadleaf and coniferous tree communities. Microclimatic variables, such as air temperature, relative humidity, and solar radiation, were analyzed. The results revealed that spatial structural parameters, such as Acanopy/H, sky view factor (SVF), and canopy density, significantly affected temperature reduction and humidity increase. Among these, the canopy-to-height ratio (Acanopy/H) was a promising potential factor influencing cooling. Simulations revealed that with a constant tree height, cooling and humidification benefits increased as Acanopy/H increased. However, with a constant canopy area, these benefits were greater when Acanopy/H ratio decreased. This study emphasizes the importance of spatial structural parameters in optimizing summer microclimatic regulation, providing key insights into urban green space design to enhance thermal comfort. These findings can guide the planning of climate-resilient plant landscapes in subtropical cities. Full article

Within the Clean Sky 2 regional project, a hybrid environmental control system has been conceived that combines the classical bleed air approach with a vapor cycle cooling in the recirculation air. To protect partners’ IP, a functional mock-up (FMU) model of the hybrid ECS was provided describing the system behavior. This model was interfaced with a zonal model of a 100-passenger regional aircraft cabin to investigate comfort and air quality conditions within the cabin. The interfacing reveals that some optimization of the control algorithm is possible for the hybrid ECS, while some operational points already perform as intended. Hence, the coupled simulation approach, at an early design stage, already shows the strengths and weaknesses of the system conception. Recommendations from the simulation study can subsequently be incorporated into the design before a physical demonstrator is produced. Full article

Driven by rapid urbanisation and global climate change, the increasing frequency and intensity of the Urban Heat Island effect poses significant risks to the health and well-being of urban dwellers across the world. To combat extreme heat and ensure a safe level of thermal comfort for urban residents, innovative and sustainable technologies, such as green infrastructure and cool roof coatings, have been incorporated into building design and urban planning. This study aims to evaluate and compare the effectiveness of six different cool roof coating brands in reducing surface temperatures under the harsh and fast-changing climate conditions in Melbourne, Australia. A pilot-sized experimental cool roof was installed on the rooftop of an existing office building to monitor surface temperature variations using a thermal infrared camera, accompanied by a statistical analysis to evaluate potential surface temperature reductions under varying weather and sky conditions. The results of this study show that the application of cool roof coatings reduced the surface temperature by at least 8.7 °C and up to 34.2 °C, corresponding to reductions of 13.2% and 53.6% from the maximum surface temperature, respectively. When comparing the six cool roof paint brands, it was observed that Brand 4 demonstrated the best performance, reducing the surface temperature to a minimum value of 34.3 °C (45.5% reduction) when the maximum surface temperature was 62.9 °C. On the other hand, Brand 5 showed the least effective performance but still achieved a reduction of 15.8 °C (25.1% reduction). This study highlights the potential of cool roof coatings as an effective urban heat mitigation strategy by lowering building surface temperatures. Alongside other urban heat mitigation strategies, such as green roofs and green walls, cool roof coatings offer a viable solution for buildings. Full article

Urban streets are critical public spaces that significantly influence the thermal comfort of city dwellers. However, the issue of summer thermal discomfort in severely cold regions has been largely overlooked. This study focuses on Youth Street in Shenyang, a city in a severely cold region, to explore the impact of various street spaces and vegetation layouts on the thermal environment and comfort using ENVI-met modeling and correlation analysis. The study varied the aspect ratio (AR) of the street, street tree species, and plant spacing across 60 scenarios and simulated thermal comfort over a 10-h period on a typical summer day. Results show that air temperature (Ta), mean radiant temperature (Tmrt) and sky view factor (SVF) are positively correlated with physiologically equivalent temperature (PET). Street trees effectively reduce Ta, increase RH and lower wind speed (WS), but plant spacing has minimal impact on WS. Higher AR values lead to greater improvements in pedestrian thermal comfort. Specifically, the highest heat mitigation rate (HMR) is observed at low AR (9.87% at AR = 0.5 and 9.94% at AR = 1.0), while it is lower at high AR (8.16% at AR = 2.0). Conversely, larger plant spacing of street trees diminishes the effectiveness of thermal comfort improvements. The improvement effect of plant spacing is more pronounced in street spaces with smaller AR. In these spaces, closer plant spacing significantly enhances thermal comfort by providing more shade and reducing Ta and Tmrt. However, in street spaces with higher AR, overly dense plant configurations can reduce WS and limit the cooling effect of ventilation, thereby diminishing overall heat mitigation ability. Conclusions suggest that urban planners should consider both street space and vegetation layouts to optimize thermal comfort. For urban main streets in severely cold regions, an AR of 1:1 with deciduous broadleaf trees and hedges planted at 6 m spacing is recommended. In high-AR streets, dense plant configurations should be avoided. This study provides valuable insights for improving the thermal comfort and sustainable design of urban street spaces, supporting new construction and development in similar climate environments. Full article

Climate change continues to exacerbate water scarcity by altering global weather patterns and intensifying extreme climatic events. This review examines the potential of atmospheric water generation technologies to mitigate water scarcity under such conditions. By leveraging a multidisciplinary approach, we review advancements in fog harvesting, sorption-based systems, membrane technologies, radiative sky cooling, and cloud seeding. A special emphasis is placed on passive systems utilizing renewable energy to address challenges of high energy demands. Predictive tools such as machine learning, climate models, and geographic information systems are explored to optimize atmospheric water generation deployment under shifting climatic conditions. This review article outlines critical innovations in materials, economic considerations, and policy frameworks required for atmospheric water generation to transition from niche to mainstream water solutions. These findings aim to inform sustainable strategies for tackling water scarcity in the context of global climate challenges. Full article

Urban heat islands (UHIs) increase urban warming and reduce outdoor thermal comfort due to changing surface characteristics and climate change. This study investigates the role of green walls (GWs) in mitigating UHI, improving outdoor thermal comfort, and reducing carbon emissions under current and future (2050) scenarios. Focusing on Via della Consolata, Turin, Italy, the study combines remote sensing for UHI detection and numerical simulations for thermal analysis during seasonal extremes. The results show that GWs slightly reduce air temperatures, with a maximum decrease of 1.6 °C in winter (2050), and have cooling effects on mean radiant temperature (up to 2.27 °C) during peak summer solar radiation. GWs also improve outdoor comfort, reducing the Universal Thermal Climate Index by 0.55 °C in the summer of 2050. The energy analysis shows that summer carbon emission intensity is reduced by 31%, despite winter heating demand increasing emissions by 45%. The study highlights the potential of GWs in urban climate adaptation, particularly in dense urban environments with low sky view factors. Seasonal optimization is crucial to balance cooling and heating energy demand. As cities face rising temperatures and heat waves, the integration of GWs offers a sustainable strategy to improve microclimate, reduce carbon emissions, and mitigate the effects of UHI. Full article

This study conducted field measurements to explore the effects of street spatial structure on micrometeorological condition and air quality on both hot and cool days in Taipei City. Six street canyons with an aspect ratio of one, but varied in street orientation, street width, sky view factor, and number of planting strips, were selected for observations. In this case study, it was observed that, as well as the meso-scale phenomena, the local and micro-scale (street canyon structure) had influences on street air temperature, mean radiant temperature, and wind velocity. However, the local and micro-scales only had minor effects on relative humidity for both hot and cool days. Shade effect on temperature by street trees was observed; this effect could cause 2 degrees drop on mean radiant temperature and about 0.5 degree drop on air temperature. Our analyses and field measurements also revealed that, in some cases, concentrations of PM_2.5 and PM₁₀ were found to be correlated with local street canopy structure; however, in some cases, the meso-scale process was found to be the dominant factor. We also found that concentrations of CO and O₃ were inversely correlated in the street canyon. The findings of this study provide introductory scientific data and guidelines for urban street designers to improve thermal comfort and air quality. Full article

Long-wave radiation cooling plays a pivotal role in building thermal design. Utilizing a steady-state method to determine surface heat transfer coefficients across diverse climates can result in discrepancies between the designed and actual cooling performance of a building’s envelope. To evaluate the influence of climate and surface emissivity on building heat transfer during summer, the numerical simulation method was employed to calculate the summer long-wave radiation for nine typical residential buildings across various climate regions. This study assesses the applicable meteorological conditions and distribution range of sky radiation technology. The findings indicate that buildings can effectively dissipate heat through sky radiation when the outdoor relative humidity is below 60% and the summer temperature difference exceeds 12 °C. Analysis of meteorological characteristics across different zones reveals a positive correlation between temperature deviations and sky radiative cooling potential, thereby identifying suitable climate zones for the implementation of sky radiative cooling technology. Full article

Energy consumption in buildings with large, glazed facades rises markedly in the summer, driven by cooling demands that vary with structural characteristics and external climate conditions. This study is unique in examining daily cooling needs in lightweight and heavyweight constructions, utilizing meteorological data from 782 summer days in Debrecen, Hungary. Unlike standard approaches, which often overlook localized meteorological variables, this analysis focuses on actual “clear sky” scenarios across distinct summer day types: normal, hot, and torrid. The findings indicate that orientation and construction type significantly affect cooling demands, with east-facing rooms demanding up to 14.2% more cooling in lightweight structures and up to 35.8% in heavyweight structures during peak hours (8 a.m. to 4 p.m.). This study reveals that for west-facing facades, extending use beyond 4 p.m. markedly increases energy loads. Furthermore, the cooling demand peak for heavyweight buildings occurs later in the day, driven by their higher thermal capacity. These insights underscore the importance of aligning HVAC system design with operational schedules and building orientation, offering data-driven strategies to enhance energy efficiency in buildings with diverse thermal and solar exposure profiles. Full article