Search Results (360)

This study employs a multi-method, high-precision research approach to evaluate the thermal comfort performance of a window-based direct evaporative cooling (DEC) air conditioning system installed in a university dormitory building (50 rooms) in Beijing. To compensate for the insufficiency of single-day test data, the study was conducted continuously for 30 days from 1 June to 30 June 2026 (00:00–23:59 daily). Eight calibrated sensor sets were deployed in each of the 50 rooms (that is, eight fixed sensor sets per room × 50 rooms = 400 synchronously logged spatial measurement points, each integrating a fixed SHT35 temperature/humidity sensor with a matched hot-wire anemometer probe; this unusually dense, building-scale simultaneous deployment is uncommon in previous dormitory studies), recording data simultaneously across all rooms throughout the test period with the DEC units continuously operating. The research integrates field physical measurement data, standardized subjective questionnaire surveys (200 within-person paired questionnaires, each pairing a student’s retrospective recall of the pre-DEC condition with an in situ vote collected during DEC operation), and advanced computational thermophysiological modeling results based on the frameworks of ISO 7730–2021 and ASHRAE Standard 55–2023. Environmental parameters, including dry-bulb temperature (Ta), relative humidity (RH), and air velocity (Va), were monitored at eight spatially distributed points per room with a 10 Hz sampling frequency and a one-hour median resolution. The mean radiant temperature (Tr) was approximated as equal to Ta due to the absence of globe temperature measurements, and this simplification is discussed as a limitation. Simultaneously, through a single-session questionnaire (June 24–30) compliant with ISO 10551 and the Appendix B requirements of ANSI/ASHRAE Standard 55, which paired each respondent’s retrospective recall of the early-June pre-DEC (non-cooled) condition with a concurrent vote collected during DEC operation—a recalled-pre/concurrent-post design rather than two separate real-time pre-/post-intervention surveys—data on clothing ensembles, activity levels, and subjective thermal sensation votes (TSV) were collected. The acquired data were input into a customized simulation platform developed in the Fortran language (which was debugged and cross-validated against the ISO 7730/ASHRAE Standard 55 reference implementation to within 0.01 PMV scale units), which employs the Fanger two-node thermoregulation model to accurately calculate and predict the predicted mean vote (PMV), predicted percentage of dissatisfied (PPD) occupants, new effective temperature (ET*), and standard effective temperature (SET*). The results indicate that the DEC unit achieved a stable outlet temperature reduction of Δt = 3.87 °C (inlet temperature 31.72 °C, outlet temperature 27.85 °C), with an average wet-bulb air temperature of 18.66 °C and an average outlet relative humidity of 58.3% (inlet RH: 42.1%), confirming the expected humidifying effect of direct evaporative cooling while maintaining an average indoor relative humidity of 42.07%—a result particularly relevant to Beijing’s dry-to-semi-humid summer environment, where evaporative cooling is thermodynamically favorable. Because no DEC-off baseline period was monitored, the measured indoor conditions are reported as observational associations with DEC operation rather than as effects attributable exclusively to the unit; the pre-DEC satisfaction level was recalled retrospectively within the same single session and is therefore subject to recall/contrast bias; and all energy-saving figures are theoretical nameplate estimates rather than metered energy consumption. Full article

Modelling of geothermal heat pump systems rarely integrates detailed surface and subsurface components. Simplifications such as neglecting the geothermal gradient, the different geological units intersected by the systems, and/or variable building loads, are common across current modeling approaches. These simplifications are particularly problematic for deep systems (e.g., >1 km). A new approach is presented to model a well doublet or a deep borehole heat exchanger (DBHE) with several heat pumps, which combines a comprehensive subsurface numerical model with codes capable of handling variable heat demand throughout the year. Groundwater flow and heat transfer are simulated with the subsurface model. Operating flow rates and number of activated heat pumps are adjusted during the simulation according to their efficiency and demand at a given time. Simulated heat production is constrained by technical and safety criteria to reflect realistic building conditions. The codes allow the simulation of cases in which the geothermal system is designed to partly meet demand, while maximizing its contribution. The thermal power production and electric consumption of the system are calculated. An illustrative example is provided for a sedimentary basin with a low geothermal gradient (~23.5 °C/km) using the Bécancour area in eastern Canada. Full article

The building heat demand and the energy system capacity are usually designed independently in solar heating systems for rural houses in cold regions. This leads to oversized system capacity and a lack of collaborative design between the building side and the energy system side. To address these issues, a building–PVT collaborative passive–active design framework was proposed for a typical rural house in Lanzhou, Gansu Province, China. First, a dynamic building thermal model was developed in EnergyPlus. Four typical building configurations, including a baseline house, an insulated house, a sunspace house, and a sunspace house with an intelligent thermal curtain, were established. The hourly heating demand over 8760 h was obtained for each configuration. Then, the hourly building heating demand was used as the unified boundary condition to develop a dynamic PVT heating system model in MATLAB. The responses of the PVT collector area, thermal storage tank volume, and auxiliary heater capacity to building heat demand were analyzed. A CSR was further proposed to establish a quantitative relationship between building heating load reduction and PVT system capacity reduction. Finally, a collaborative multi-objective optimization was carried out using the NSGA-II with the objectives of maximizing the SF and minimizing the LCC. The TOPSIS was adopted to determine the optimal compromise solution. The results show that the integrated passive design combining a sunspace with an intelligent thermal curtain reduces the annual heating energy consumption by 44.0% compared with the baseline house. The reduction in building heat demand simultaneously decreases the required PVT system capacity. The PVT collector area, thermal storage tank volume, and auxiliary heater capacity decrease by 44.14%, 27.55%, and 25.78%, respectively. This indicates that passive building energy-saving measures significantly change the design boundary of the energy system. The proposed CSR effectively quantifies the capacity substitution effect of building-side energy saving on the PVT heating system, and the integrated passive design achieves the highest overall CSR. The multi-objective optimization generates a uniformly distributed Pareto front. The optimal compromise solution achieves an SF of 86.41% with an LCC of 8.34 × 10⁴ CNY. The recommended configuration includes a 50 mm insulation layer, a 40 m² sunspace, a 12.62 m² PVT collector area, and a 1.23 m³ thermal storage tank. Compared with the initial design, the optimized configuration significantly improves solar energy utilization while maintaining a low LCC and further reducing the required auxiliary heater capacity. This study establishes a collaborative analysis framework between building heat demand and PVT system capacity. A quantitative mapping method between building heating load and system capacity is proposed. The framework enables integrated optimization of building thermal design and energy system capacity configuration. The proposed method provides a new theoretical approach and practical guidance for the design of solar heating systems for rural houses in cold regions. Full article

Against the backdrop of accelerating transitions to sustainable energy systems, the optimal operation of microgrids and the high-efficiency integration of renewable energy face growing technical challenges, which highlight the necessity of tapping into flexible multi-energy resources to the fullest extent. Aiming at low-carbon microgrid systems with electro-thermal demands, this paper proposes a sustainable dispatch strategy that actively integrates waste heat recovery and building thermal inertia. First, a refined mathematical model of a Hybrid Energy Storage System (HESS) is developed, considering waste heat recovery processes from the electrolyzer and the fuel cell. Second, an optimal dispatch model considering the HESS and building thermal inertia (BTI) is constructed, the PMV index is adopted to quantify the adjustable margin of user thermal demand, and the objective function accounts for multiple economic and environmental indices, including energy procurement costs, equipment maintenance costs, and carbon emission trading costs. Case studies show that this strategy can effectively enhance the regulation flexibility of the system, significantly reducing comprehensive operational costs by up to 51.6% and improving local renewable energy accommodation while ensuring environmental sustainability and low-carbon operation. Full article

Continuous monitoring of Activities of daily living (ADLs) requires sensing systems that are privacy-preserving, low-power, and robust to environmental variation. Ambient sensing technologies provide an alternative to RGB video and wearable devices, but individual sensing modalities exhibit characteristic limitations. Sparse mmWave radar provides strong motion sensitivity but limited posture detail, low-resolution thermal sensing preserves posture-related spatial information, and smart plug telemetry captures only appliance-mediated behavioural interaction. To address these limitations, this paper proposes a layered multimodal ambient-sensing framework comprising a sparse-track 24-GHz FMCW radar, a $32\times 24$ low-resolution thermal sensor, and a Moko smart plug. It experimentally evaluates a radar–thermal HAR branch together with a separate smart plug appliance-recognition branch. The framework proposes three streams to enable continuous non-wearable monitoring while maintaining redundancy and reduced privacy exposure for intelligent-building and ambient assisted living environments. Radar and thermal streams are jointly evaluated on binary motion and four-class posture and activity recognition tasks collected across multiple environmental configurations using recording-grouped cross-validation, while the appliance stream is evaluated using per-plug telemetry from residential-grade appliances. The radar–thermal streams use a single-subject, fixed-placement dataset of binary-motion windows and four-class posture and motion windows collected across six furniture configurations. The separate intrusive load monitoring stream utilises smart plugs to classify appliances. Regarding binary motion recognition, radar $(F_{1,\mathrm{Transformer}}=0.882\pm 0.034)$ and thermal $(F_{1,\mathrm{XGBoost}}=0.870\pm 0.069)$ pipelines achieved similar macro F1 performance. On the four-class posture and activity recognition task, thermal features $(F_{1,\mathrm{thermal}}=0.775\pm 0.053)$ substantially outperformed radar $(F_{1,\mathrm{radar}}=0.609\pm 0.110)$. Weighted late fusion produced only modest descriptive gains. Separately, smart plug telemetry demonstrated strong appliance recognition performance using lightweight tree-based models suitable for constrained edge deployment. The results support a scoped redundancy argument. Sparse track-level radar carries gross motion, while low-resolution thermal sensing carries posture. The smart plug appliance monitoring extends the framework toward appliance-mediated instrumental activity of daily living (IADL) monitoring, with lightweight tree-based models achieving strong recognition performance under constrained edge deployment conditions. The findings support a layered multimodal sensing architecture for privacy-preserving ADL monitoring, where radar contributes motion-sensitive coverage, thermal sensing contributes posture-aware spatial context, and smart plug telemetry contributes appliance-level behavioural evidence within intelligent healthcare and ambient assisted living environments. Full article

This paper presents a critical review of surface protection strategies for refurbished hydropower components, with emphasis on the manufacturing and materials-processing logic that links damage mechanisms, substrate condition, deposition route, microstructure, and service performance. The literature indicates that cavitation erosion, sediment abrasion, corrosion, and their synergistic interactions are intensified by flexible and off-design hydropower operation, making refurbishment decisions increasingly surface-sensitive rather than purely bulk-material problems. Thermal spray and laser cladding remain the dominant industrially relevant routes, while cold spray and emerging multi-principal-element, high-entropy, and Fe-based amorphous systems expand the design space for lower heat input, better defect control, and improved cavitation resistance. Across the considered studies, the most consistent conclusion is that hardness alone is not a reliable selection criterion; porosity, interfacial integrity, crack susceptibility, residual stress, and the ability to accommodate local deformation govern real durability. Chemical pre-treatments, sealants, and hybrid finishing routes appear less mature as standalone hydropower solutions, but are important enablers for substrate activation, coating densification, and corrosion mitigation. Therefore, the review proposes a refurbishment-oriented framework in which route selection is based on the initial damage state of the component, the admissible thermal load on the substrate, the required build-up thickness, and the expected cavitation/slurry/corrosion regime. Full article

Femtosecond laser writing (FLW) enables mask-free three-dimensional photonic integration in transparent materials and offers a flexible route for prototyping glass-based photonic circuits. Here, we present a monolithic fabrication approach that combines femtosecond laser waveguide writing, femtosecond laser-induced chemical etching (FLICE), laser ablation, and metallization to realize reconfigurable photonic circuits in borosilicate glass. The process is implemented in a CAD-to-device workflow that allows optical, mechanical, and electrical structures to be co-designed and fabricated within the same substrate. A stress-assisted waveguide-writing regime is developed in borosilicate glass, enabling single-scan fabrication of optical waveguides, directional couplers, and Mach–Zehnder interferometers at writing speeds of 30 mm/s. The fabricated devices demonstrate stable guiding, directional coupling, and interferometric operation, providing a practical basis for implementing reconfigurable photonic building blocks in this material platform. FLICE is then used to fabricate suspended glass microbridges incorporating femtosecond-laser-written waveguides and integrated resistive microheaters. These structures act as thermally isolated thermo-optic phase shifters and enable a full 2π phase shift with an electrical power consumption of approximately 17 mW. The results demonstrate the feasibility of combining FLW and FLICE within a single borosilicate glass substrate to monolithically integrate passive photonic circuits with actively tunable thermo-optic phase shifters. This work establishes a laser-based fabrication route for reconfigurable three-dimensional photonic circuits in glass and provides a basis for future optimization toward larger programmable photonic systems. Full article

Climate adaptation in high-density cities requires equitable access to cooling and habitat benefits from blue–green infrastructure (BGI). However, the critical thresholds where human activity overwhelms these services remain unknown. Taking Shenzhen as a case study, we quantified habitat quality using the InVEST model and divided the urban landscape into low-, medium-, and high-quality zones. After screening significant drivers via multiple linear regression, we compared six machine learning algorithms and selected XGBoost (for low- and medium-quality zones) and LightGBM (for high-quality zones) with Optuna-tuned hyperparameters, then applied SHAP dependence analysis to identify nonlinear, threshold-driven responses. We identify a systemic thermal threshold of 23.7 °C. Above this temperature, BGI cooling efficiency decouples from habitat quality. We also quantify actionable intervention windows. Low-quality habitats—dominated by dense residential areas—collapse when building density exceeds 0.7 or road density exceeds 0.009. Medium-quality habitats offer a balance window (core area > 2844 m², building density < 0.361) that enables incidental nature contact during daily travel. High-quality refugia require a core area > 8600 m² with near-zero disturbance. These thresholds expose a stark green inequity: socioeconomically vulnerable groups in low-quality zones are systematically disconnected from cooling services. We translate these findings into a tiered spatial intervention framework—restoration, accessibility enhancement, and strict protection—to advance climate-resilient and socially equitable urban planning. Full article

Inorganic thermal-insulation mortars can effectively reduce the energy consumption and carbon emissions of both existing and new buildings while maintaining the thermal stability of building envelopes. Compared with conventional mortars, these materials exhibit more pronounced multiscale coupling during curing, and their microstructural evolution and macroscopic properties are highly sensitive to environmental variables, particularly temperature, humidity, and ionic concentration. This review systematically summarizes the effects of high-temperature curing, high-humidity curing, artificially introduced ions, and special curing regimes on the mechanical properties, durability, thermal conductivity, and fire resistance of inorganic thermal-insulation mortars. The reviewed studies indicate that hydration, geopolymerization, and CO₂-curing reactions can all promote microstructural densification and thus enhance mechanical performance and durability. Elevated temperature and humidity generally accelerate reaction kinetics, intensify internal hydration, and facilitate the generation and deposition of gel products, thereby refining the pore structure and improving strength development. However, the same densification process may also increase the continuity of the solid phase and form more effective heat-transfer pathways, which is unfavorable for thermal-insulation performance. Mildly alkaline curing environments can further stimulate binder reactions and improve matrix compactness, although excessive ionic activity may negatively affect pore stability and long-term performance. Among the coupled curing conditions, wet–dry cycling appears to provide a more favorable balance between mechanical-property development and pore-structure preservation, because periodic humidity gradients can enhance strength formation, stabilize the interfacial transition zone, and reduce cracking sensitivity. Overall, the effect of curing on inorganic thermal-insulation mortars is governed by the competition and balance between reaction enhancement, pore-structure evolution, and interfacial stabilization. Future curing design should therefore focus on system-dependent optimization to achieve a rational balance among mechanical performance, thermal insulation, and fire resistance. Full article

The construction sector is responsible for approximately 38% of global CO₂ emissions, driven primarily by energy demand for thermal comfort. This research evaluated the implementation of a Passive Climate Control System (PCCS) based on circular economy principles. This system acts as a thermal buffer composed of recycled PET bottles filled with 500 mL of water and a reflective coating, installed on the roof slab. Through a case–control study in Veracruz, Mexico, hygrothermal performance was monitored for ten months. The results demonstrated the superiority of the PCCS over the conventional slab: in autumn–winter, temperature fluctuations were reduced by 26.7%, while in spring–summer, the maximum temperature was limited by 1.3 °C during the daytime peak. Fractal analysis confirmed that the PCCS promotes a homogeneous thermal distribution (Fd ≤ 1.255), maintaining internal conditions within the comfort zone. The implementation of this PCCS, based on waste valorization, is a robust and sustainable solution that offers a viable alternative to active climate control. It promotes hygrothermal comfort and reduces energy consumption, aligning with the objectives of Clean Technology and building efficiency. Full article

Outdoor public spaces are important built-environment settings that support health, social interaction, psychological restoration, and everyday urban life. In cold-region cities, however, winter conditions such as low temperature, snow and ice, short daylight, reduced vegetation, low solar altitude, and declining outdoor activity substantially weaken their usability, attractiveness, and vitality. Existing studies have mainly addressed these problems through thermal comfort, microclimate adaptation, snow safety, and physical environmental optimization, but they provide limited explanation of how users visually perceive winter spaces, allocate attention, and form subsequent spatial interpretations, perceptual evaluations, and behavioral intentions. To address this gap, this conceptual article develops a built-environment framework for explaining winter visual perception mechanisms and proposes an agenda for future eye-tracking-based validation. Through conceptual synthesis across cold-region public-space research, outdoor thermal comfort, environmental psychology, landscape visual perception, eye-tracking studies, public-space behavior, and architectural and built-environment design, the study conceptualizes winter public spaces as seasonal perceptual environments. It identifies five categories of winter visual stimuli: surface-related, vegetation-related, building interface-related, lighting-related, and activity-related stimuli. The framework clarifies how visual attention may serve as an observable mediating process between winter visual stimuli and inferred spatial interpretation, perceptual evaluation, and behavioral intention. Rather than empirically confirming these relationships, the article formulates a testable conceptual model and future validation agenda that should be examined through eye-tracking, behavioral observation, subjective evaluation, and environmental measurements. For architectural and built-environment research, the framework provides a theoretical basis for evaluating and optimizing façades, ground-floor interfaces, entrances, canopies, semi-outdoor spaces, path boundaries, lighting systems, vegetation configuration, and winter activity nodes. Full article

This study presents a comparative evaluation of geopolymer foams incorporating either commercially available shape-stabilized phase change materials (PCMs) or laboratory-developed diatomite–paraffin PCM granules with controlled particle size fractions ranging from <1.6 mm to >2.5 mm. All PCM variants were incorporated at a constant dosage of 7.5 wt.% to isolate the influence of PCM type on the properties of the resulting composites. The commercial materials comprised PX-4, PX15, and PX20 (Rubitherm Technologies GmbH), whereas the laboratory-developed PCM consisted of paraffin immobilized within a porous diatomite matrix to produce granular shape-stabilized composites. The experimental program included the determination of bulk density, total porosity, pore size distribution, thermal conductivity (λ), thermal resistance (R), specific heat capacity (Cp), and compressive strength. The pore structure was characterized by mercury intrusion porosimetry (MIP), while the morphology and dispersion of PCM particles within the geopolymer matrix were investigated using scanning electron microscopy (SEM). All mixtures were produced using the same alkali-activated matrix and identical curing conditions, with the PCM content maintained at 7.5 wt.%. The results demonstrated that the type of PCM significantly affected the microstructure and thermophysical performance of the geopolymer foams. The laboratory-developed diatomite–paraffin PCM provided the most favorable thermal insulation performance, exhibiting the lowest thermal conductivity (0.095 W/m·K) together with the highest thermal resistance (0.278 m²·K/W). In contrast, the commercial PX15 and PX20 materials exhibited the highest specific heat capacities (1.740 and 1.778 kJ/kg·K, respectively), indicating superior thermal energy storage capability. In addition, the estimated production cost of the laboratory-developed PCM (2.5–4.0 EUR/kg) was substantially lower than that of the commercial PX materials (approximately 20 EUR/kg), highlighting its potential as a cost-effective alternative for sustainable, energy-efficient building materials. These findings demonstrate that both commercial and laboratory-developed PCM systems can effectively enhance the functionality of geopolymer foams, although they provide different balances between thermal insulation, heat storage capacity, and production cost. Full article

To explore the optimized operating strategies coupling floor cooling with cold storage for thermal active systems (TABSs), effects of operating time on indoor thermal environment, cold storage capacity, energy use and running cost were studied. Simulations were conducted based on an actual office building equipped with floor cooling. To take full advantage of the TABS and off-peak electricity, four operating cases with nighttime floor cold storage were proposed, namely C₁ (2:00–8:00), which operated only during the off-peak hours, C₂ (2:00–10:00), C₃ (2:00–12:00), and C₄ (2:00–14:00), which operated during the off-peak and flat hours. A simulation case of C₀ operating during daytime (7:00–17:00) was also proposed. Simulation results show that the C₁ and C₂ conditions with shorter operating hours result in higher indoor temperatures, which cannot ensure indoor thermal comfort. The PMV index in C₃ and C₄ conditions can be kept between −1 and 1, which meets the thermal comfort demand of Grade II. Considering that the operating duration of C₃ is the same as the occupied hours, the cold storage capacity, cooling loss, cooling supply and release process, etc., of this case are further analyzed based on data of a typical day. The floor and ceiling slabs store most of the cooling energy (72.7%) during the night; inner walls also store part of the cooling energy (23.3%) and cooling loss during cold storage accounts for approximately 3.1%. During working hours, the cooling energy released is lower than the cooling load, which makes indoor temperatures increase continuously. Compared with case C₀, case C₃ has same power use while saving 2.8% of running costs. Case C₄ provides a higher level of thermal comfort, while saving 0.9% of costs with a 1.5% increment in electricity use. This study provides detailed data about cold storage strategies coupling with floor cooling in TABS, which can be used to save running cost. Full article

Green walls, as part of nature-based solutions, have been implemented in urban environments, enhancing energy efficiency, thermal regulation, biodiversity, environmental quality, and human well-being. Despite these benefits, green walls’ environmental performance across their life cycle is reported inconsistently in the literature, limiting robust comparisons and evidence-based decision-making in the built environment. This review synthesizes current knowledge on the environmental performance of green walls, living wall systems, and active living walls, including systems that improve indoor air quality and enable water reuse. A systematic literature review was conducted following PRISMA guidelines using the databases ScienceDirect, Scopus, and Google Scholar. The results show that methodology gaps in life cycle assessment (LCA) studies of living wall systems restrict their applicability for evidence-based design and specification. Future research should integrate embodied and operational impacts in scenario-based and sensitivity analyses considering plant selection, irrigation strategies, maintenance regimes, replacement rates and service-life assumptions. More focus should be given to tropical cities to understand the impact of climate, water demand, vegetation performance. and maintenance intensity. These improvements would lead to more comparable, context-sensitive, and design-oriented LCA evidence for sustainable building applications. Full article

This study comparatively examines the effects of different active and passive energy strategies on energy performance, carbon emission reduction, economic feasibility, and thermal comfort potential in a university building in Ankara. This study uses a university building with 8760 h of recorded operational electricity consumption data as a real-world reference case and evaluates different retrofit strategies through dynamic building energy simulations. Simulation results were evaluated not only in terms of total energy consumption but also in terms of operational carbon emissions, levelized cost of energy (LCOE/LCOSE), and the potential for improving indoor temperature stability through passive design strategies. The results show that PV system integration provides the highest energy and carbon reduction performance by reducing the net grid electricity consumption by 89.76%. Among passive systems, the Trombe wall scenario provided the highest energy savings and the lowest LCOSE value. PCM application stood out in terms of indoor temperature stability potential, while the green roof system contributed to temperature control, especially during the summer. In addition, an economic sensitivity analysis based on the discount rate was carried out to reveal the strengths and weaknesses of the proposed strategies in terms of sustainable building design. The study contributes to the comparative analysis of active and passive retrofit strategies in university buildings by offering an integrated and multi-dimensional evaluation approach supported by real operational data. Full article