Search Results (37)

Current detection technologies of operation current in power systems primarily rely on electromagnetic induction principles and infrared thermal imaging. These methods suffer from inherent limitations such as dependence on external power supplies, susceptibility to interference in complex electromagnetic environments, and high equipment costs. Electrochromic materials, which can directly convert electrical signals into optical signals and enable self-sensing without external power, offer a novel technological pathway for condition monitoring of electrical equipment. However, existing electrochromic materials still face technical challenges in power equipment operating environments, including high response thresholds, poor environmental stability, and short cycle life. Based on the synergistic electrochromic effect of poly(3-hexylthiophene) (P3HT) and fluoran, this study develops a color-changing coating suitable for operating current sensing. Core–shell structured microcapsules with urea-formaldehyde resin as the wall material were prepared via in situ polymerization to effectively encapsulate the P3HT–fluoran composite core material. These microcapsules were uniformly dispersed in an epoxy acrylate/TMPTA ultraviolet-curable resin system to form a current-sensing coating with excellent adhesion and insulation properties. Test results show that the coating, applied on a busbar, undergoes a noticeable color change from red to white within 30 s when a current of 100 A passes through the busbar, with a color difference (ΔE) of 25.3. The coating exhibits adhesion strength exceeding 11.7 MPa, volume resistivity on the order of 10¹³ Ω·m, and a breakdown field strength higher than 85 kV/mm. After 100 cycles, ΔE remains stable, demonstrating good cyclic durability. This research provides a new visual sensing solution for high-current monitoring and shows broad application prospects in the field of power equipment operation status monitoring. Full article

Maintenance is crucial for the durability of the existing building stock and should be perceived as an opportunity to improve the built environment. The implementation of thermal retrofitting measures to the building’s envelope enhances global energy performance, which is economically and environmentally beneficial. Building-related energy consumption during the operation phase is key to tackling carbon neutrality and climate change. Introducing thermal retrofitting within the context of maintenance planning can be cost-optimizing, as it reveals the technical–economic synergy between building pathology and energy efficiency. Maintenance activities and energy demand throughout the building’s service life influence life-cycle costs (LCCs). Decision-making based on LCC awareness is an advantage for owners. This study discusses the impact of implementing an optimal retrofitting solution (ORS), according to different maintenance strategies, on the LCC of an existing single-family home. The ORS comprises the following measures: adding an external thermal insulation composite system (ETICS) to external walls, extruded polystyrene (XPS) panels to the roof, and replacing the existing windows with others with improved thermal performance. The three maintenance strategies involve different complexity levels, concerning the type, number and timing of activities. Moving beyond isolated assessments, this study develops an integrated framework that bridges based on two existing background methodologies, involving optimal thermal retrofitting and condition-based maintenance planning, which, combined with new research, enable the assessment of maintenance, energy and global LCC for a time horizon of 100 years. The evaluation of energy-related LCC is based on simulations. The results indicate that these costs represent the majority of the global LCC. The ORS has a considerable positive impact on energy and global LCC. Adopting a maintenance strategy characterized by fewer planned activities and an earlier schedule of replacement interventions, which determines the implementation of the retrofitting measures, is better in terms of LCC savings. Full article

Improving the energy efficiency of historic field stone masonry buildings often requires internal insulation, as external insulation is frequently restricted by heritage and architectural constraints. Internal insulation, however, alters the hygrothermal behavior of massive masonry walls and may increase moisture-related risks. This study assesses the hygrothermal performance of an internally insulated historic field stone masonry wall under past and projected future climatic conditions using long-term transient simulations. Coupled heat and moisture transfer simulations were performed with the DELPHIN software for an uninsulated reference wall and an internally insulated configuration. The analyses accounted for wind-driven rain, masonry heterogeneity, and variations in inner core composition. Past conditions were represented by a continuous 20-year measured climate dataset, while future conditions were evaluated using regional late-century climate projections (RCP2.6 and RCP8.5). Hygrothermal performance was evaluated based on moisture mass density, freeze–thaw exposure, and mold-relevant temperature–relative humidity conditions at predefined evaluation points within the wall. The results show that moisture accumulation develops gradually and cannot be reliably captured by short simulation periods. Internal insulation redistributes moisture-related risks within the wall rather than fundamentally altering the seasonal moisture regime. Freeze–thaw exposure occurs under all investigated climates, while mold-relevant humidity conditions persist at interior-adjacent locations. The findings demonstrate the importance of multi-year hygrothermal analyses when assessing moisture-related risks in internally insulated historic masonry walls. Full article

Aerogel-incorporated foam concrete has attracted significant attention in the construction sector owing to its light weight and superior thermal insulation properties. Nevertheless, its practical application in external wall insulation systems is hindered by the high cost of aerogel (AG) and the inherent trade-off between thermal efficiency and mechanical strength. To overcome these limitations, this study introduces a composite design that partially replaces AG with low-cost hollow glass microspheres (HGMs) and incorporates nano-silica (NS) as a strengthening agent. Foam concrete specimens with a constant dry density of 700 kg/m³ were fabricated with these additives. Through an orthogonal experimental approach, the synergistic effects of AG, HGMs, and NS on mechanical properties, porosity, water absorption, and durability were systematically evaluated. The results demonstrated that 4% AG content significantly reduced effective porosity by 33% and water absorption by 59%, while 4% HGM increased compressive and flexural strength by 13.5% and 19.7%, respectively. The addition of 2% NS further enhanced mechanical performance, yielding 25.9% and 21.6% improvements in compressive and flexural strength. The optimal formulation (A4H4N2) effectively balanced thermal insulation and mechanical properties, offering a viable strategy for producing cost-effective, high-performance foam concrete suitable for building envelope applications. Full article

This study focuses on the operational energy consumption of existing thermal power plant buildings in China’s hot-summer, cold-winter regions. Unlike conventional civil buildings, thermal power plant structures feature intense internal heat sources, large spatial dimensions, specialized ventilation requirements, and year-round industrial waste heat. Consequently, the energy consumption characteristics and energy-saving logic of their building envelopes remain understudied. This paper innovatively employs a combined experimental approach of field monitoring and energy consumption simulation to quantify the actual thermal performance of building envelopes (particularly exterior walls, doors, and windows) under current operating conditions, identifying key components for energy-saving retrofits of the main plant building envelope. Due to the fact that most thermal power plants were designed relatively early, their envelope structures generally have problems such as poor insulation performance and insufficient air tightness, resulting in severe energy loss under extreme weather conditions. An energy consumption simulation model was established using GBSEARE software. By focusing on heat transfer coefficients of exterior walls and windows as key parameters, a design scheme for energy-saving retrofits of building envelopes in thermal power plants located in hot-summer, cold-winter regions was proposed. The results show that there is a temperature gradient along the height direction inside the main plant, and the personnel activity area in the middle activity level of the steam engine room is the most unfavorable area of the thermal environment of the steam engine room. The heat transfer coefficient of the envelope structure does not meet the current code requirements. The over-standard rate of the exterior walls is 414.55%, and that of the exterior windows is 177.06%. An energy-saving renovation plan is proposed by adopting a composite color compression panel for the external wall, selecting 50 mm flame-retardant polystyrene EPS foam board for the heat preservation layer, adopting 6 high-transmittance Low-E + 12 air + 6 plastic double-cavity for the external windows, and adding movable shutter sunshade. The energy-saving rate of the building reached 55.32% after the renovation. This study provides guidance for energy-efficient retrofitting of existing thermal power plants and for establishing energy-efficient design standards and specifications for future new power plant construction. Full article

Biosourced materials made of a combination of raw earth and fibers are attracting increasing interest for low-carbon construction due to their reduced environmental impact and good thermal and hygric performance. This study investigates several soil–fiber composites selected and formulated at different densities to assess their thermal conductivity, enabling the selection of two complementary materials: a structural earthen mix and a lightweight insulating mix. Experimental measurements were taken under controlled conditions and used to characterize heat and moisture fluxes, and numerical calculations were carried out to evaluate the performance of single and double-layer wall configurations. The results showed that an increase in thermal gradients accelerates vapor migration and alters the internal distribution of moisture. The evaluation of wall configurations demonstrated that placing the earthen insulating layer externally optimizes thermal fluxes and eliminates condensation risks at the interface between materials, while internal insulation can be sensitive to hygrothermal gradients and prone to moisture accumulation. The combined experimental–numerical approach provides new insights into high-performance designs of bio-based earthen envelopes, establishing guidelines for minimizing moisture-related risks in low-carbon building systems. Full article

At present, phosphogypsum, as an industrial by-product, is a solid waste in phosphoric acid production, and its accumulation has caused serious environmental pollution. Furthermore, due to the insufficient insulation properties of traditional wall materials, the issue of a rising proportion of building energy consumption in total social energy consumption has become increasingly pressing. The study investigated vitrified beads as a light aggregate and phosphogypsum, mineral powder, and quicklime as an inorganic composite cementitious system to prepare the phosphogypsum-based lightweight thermal insulation material. The effect mechanism of the initial material ratio on the mechanical properties and micro-morphology of insulation materials was studied by macroscale mechanical property testing, X-ray diffraction, and scanning electron microscopy. Meanwhile, in order to meet the performance indexes specified in relevant standards, insulation materials were modified by adding sulfate aluminate cement, basalt fibers, and a waterproof agent to improve the strength, toughness, and water resistance. Based on the single-factor experimental design, the optimal dosage of various admixtures was obtained. The results indicated that the optimal properties of the sample were achieved when the binder–bead ratio was 1:4, the water–binder ratio was 1.6, the dosage of hydroxypropyl methylcellulose was 0.1%, and the solid content of waterborne acrylic emulsion was 24%. The optimal dosages of cement and fibers were 8% and 0.9%, respectively. The cement hydration products and gypsum crystals lapped through each other, filling the pores in the matrix and increasing the strength of the sample. In addition, the fibers could form a disordered network structure inside the matrix, disperse external force, weaken the stress concentration at the tip of internal cracks, and significantly improve the toughness of the modified sample. By incorporating 2.0% paraffin emulsion in the mortar and spraying 5 dilutions of sodium methyl silicate on the external surface, dense protective layers were formed both inside and outside the modified sample. The water absorption rate reduced from 30.27% to 23.30%, and the water resistance was increased to satisfy the specified requirement for the insulation material. Full article

This study investigates the use of thermally activated composite panels (TACP) as an energy-efficient retrofitting solution for existing buildings. By utilizing low-grade heat sources, TACP offers significant energy efficiency and carbon emission reduction. To address the challenges posed by high embodied carbon, exterior envelope delamination, and fire safety risks associated with conventional insulation materials, three TACP configurations were proposed: external insulation with externally embedded pipes (EE-TACP), external insulation with internally embedded pipes (EI-TACP), and internal insulation with internally embedded pipes (II-TACP). These were proposed for adapting TACP-walls to the diverse climate zones of Gansu Province. To clarify the thermal performance, energy-saving potential, and reduction effect on conventional insulation thickness of TACP-walls under different climatic conditions and heat source temperatures, dynamic heat transfer models of the TACP-wall were developed and validated. Three energy-saving rate (ε) indicators were introduced to analyze the dynamic thermal behavior in typical cities across the three climate zones of Gansu Province. A comparison was made among the three configurations in terms of instantaneous thermal response characteristics, cumulative internal surface heat load, and ε, relative to both non-insulated walls (NI-walls) and conventional insulated energy-saving walls (CE-walls). The results demonstrate that the application of TACP-walls significantly enhances thermal performance under all three climatic conditions. Irrespective of operating conditions, the ε remains essentially constant corresponding to the four insulation thicknesses, indicating that traditional thickness can be drastically curtailed. EE-TACP, EI-TACP, and II-TACP achieve pronounced ε values of 7.57/7.97/7.50 relative to NI-wall and CE-wall at inlet temperatures of 28–36 °C. Among the three configurations, EI-TACP performs most prominently across all climate zones. The findings provide a valuable reference for the application and optimization of thermally activated technology in energy-efficient retrofits of existing buildings. Full article

Given that the stock of coal gangue is increasing annually, and especially considering the problem of resource utilization after the spontaneous combustion of coal gangue accumulations with large thickness, the post-spontaneous combustion of coal gangue (SC coal gangue) from Yangquan, Shanxi, was selected as a research object. After crushing and screening, SC coal gangue was used as a coarse and fine aggregate, and through concrete mix design and a trial mix of concrete and mix ratio adjustment, concrete of strength grade C20 was obtained. Through experiments, the strength, elastic modulus, frost resistance, carbonation depth and other performance indicators of the concrete were measured. Using the SC coal gangue concrete, a 20 mm thick SC coal gangue panel was designed and manufactured. Through experimental tests, the bearing capacity, hanging force, impact resistance, impermeability and other properties of the board met the requirements of the relevant standards for building wallboard. For the SC coal gangue panel composite rock wool, its heat transfer coefficient decreased by 34.0%, air sound insulation was $\ge 45 \mathrm{d}\mathrm{B}$, and the self-weight of the external wallboard was reduced by 37.5%, so the related performance was better than the requirements of the current standard. The research results have been successfully applied to an office building project in Shanxi, China. Using SC coal gangue to make the external wallboard of the building, the reduction and recycling of solid waste are realized. In addition, the production of wall panels has been industrialized, thereby improving the construction efficiency. Full article

This study empirically verified the effect of solar radiation on the building envelope, with particular emphasis on the generated surface temperature. A model of a cellular concrete block wall with ETICS (External Thermal Insulation Composite System) was constructed with varying insulation-plaster configurations, followed by tests in a “sun chamber” aging chamber and numerical analyses. The measurement results were compared with those from the numerical simulations, taking into account the thermal properties of the materials used and the radiation exposure conditions. The purpose of the study was to determine to what extent different types of plasters and insulation materials affect the heating of the façades. Computer simulations confirmed the direction of energy flow and the gradual heating of successive layers. Furthermore, the differences between the material variants were consistent with the experimental observations. By modeling perfectly uniform conditions, the numerical analysis allowed us to limit the impact of radiation variability, resulting in results with reduced error. Full article

The study aimed to investigate the thermal storage potential of oak tree bark as a natural and easily accessible material and to examine the possibility of incorporating this raw material into external prefabricated walls. The U-values of oak tree bark were compared with mineral wool (MW), which is a standardized and well-known insulating material. Oak tree bark, a residual material, is mainly used as an energy source. However, in light of actual green policies at the European Union (EU) level, raw wood and its components, e.g., bark, should be used for long-lasting products and not as an energy source. According to the Croatian Technical Regulation on the Rational Use of Energy and Thermal Insulation in Buildings, the maximum U-value for external walls in Croatia is 0.30 W/m²K. Here presented test results show that the U-values of the experimental wall compositions were 0.22 W/m²K for the wall with mineral wool (MW) and 0.29 W/m²K for the wall with oak tree bark. Despite mineral wool having a thermal conductivity (λ, W/mK) 53% lower than the experimental tree bark, walls with bark fulfill the national insulation requirements; therefore, they present an alternative and sustainable insulation option. Furthermore, the Blower door test (n50 value) of the bungalow was measured to be 3.75 h^−1, proving the potential of tree bark as an alternative eco-friendly insulation material in exterior walls. However, further investigations are necessary in order to create and optimize the panel, its thickness, density, adhesive technology, the size of bark particles, production parameters, etc., as these influence properties of the final product to be placed on the market. Full article

This paper reviews the measurement challenges associated with 3D scanning techniques in civil engineering, exploring the practical aspects of scanning buildings and complex surfaces through various case studies. The paper details the conventional use of Terrestrial Laser Scanning (TLS) for reconstructing the technical documentation of a hall. Then it describes an unconventional application of this technique for measuring an External Thermal Insulation Composite System (ETICS) wall, aimed at detecting microdeformations caused by environmental factors controlled within a climatic chamber. Subsequently, the measurements of the insulated wall were repeated using a metrological grade laser scanner. The numerical data were analysed with inspection engineering methods. The deformation maps and displacements of selected reference points were compared. This approach yielded qualitative and quantitative results. The qualitative results, i.e., the distribution of deformations in the form of a map, turned out to be consistent. However, quantitative results show a significant discrepancy in extreme cases of up to 70%. Full article

Timber–concrete composite (TCC) systems join the positive aspects of engineered wood products (good seismftaic behaviour, low thermal conductivity, environmental sustainability, good behaviour under fire if appropriately designed) with those of concrete (high thermal inertia, durability, excellent fire resistance). TCC facades are typically composed of an internal insulated timber-frame wall and an external concrete slab, separated by a ventilated air cavity. However, there is very limited knowledge concerning the performance of TCC facades, especially concerning their thermal behaviour. The present paper deals with the development and optimization of a 2D Computational Fluid Dynamic (CFD) model for the analysis of TCC ventilated façades’ thermal behaviour. The model is calibrated and validated against experimental data collected during the annual monitoring of a real TCC ventilated envelope in the north of Italy. Also, a new solver algorithm is developed to significantly speed up the simulation (i.e., 45 times faster simulation at an error below 3.5 °C compared to a typical CFD solver). The final model can be used for the time-efficient analysis (simulation time of approximately 23 min for a full day in real-time) and the optimization of the thermal performance of TCC ventilated facades, as well as other ventilated facades with external massive cladding. Our simulation strategy partially avoids the expensive and time-consuming construction of mock-ups, or the use of comparably slow (conventional) CFD solvers that are less suitable for optimization studies. Full article

Saudi Arabia faces significant challenges in managing the rising energy consumption in buildings driven largely by its hot climatic conditions. As a result, retrofitting building facades to enhance energy efficiency has become a critical strategy. This study assesses the effectiveness of various façade retrofit strategies in reducing cooling electricity consumption using a real-time case study in Dhahran, Saudi Arabia. The strategies explored include external wall upgrades, window replacements, and installation of shading devices. Each strategy was evaluated individually, considering the reduction in heat gains, cooling load, and payback period as key performance indicators. To further maximize energy efficiency, these strategies were also analyzed in combination using the genetic algorithm optimization method, yielding 224 possible facade configurations. The optimal solution included the use of an External Thermal Insulation Composite System (ETCIS) in walls, louvers in windows, and low-emissivity coating with Argon gas-filled glazing, achieving a cooling energy reduction of approximately 16% and a payback period of 14.8 years. This study provides several recommendations for improving the efficiency of retrofitting building façades in hot climatic conditions. Full article

This article emphasizes the significance of understanding the actual thermal properties of thermal insulation materials, which are crucial for avoiding errors in building design and estimating heat losses within the energy balance. The aim of this study was to analyse the thermal parameters of selected thermal insulation materials, particularly in the context of their stability after a period of storage under specific conditions. The materials chosen for this study include commonly used construction insulations such as polystyrene and mineral wool, as well as modern options like rigid foam composites. Experimental studies were conducted, including the determination of the thermal conductivity coefficient λ, as well as numerical analyses and analytical calculations of heat flow through a double-layer external wall with a window. The numerical analyses were performed using the TRISCO software version 12.0w, based on the finite element method (FEM). A macrostructural analysis of the investigated materials was also performed. The findings indicated that improper storage conditions adversely affect the thermal properties of insulation materials. Specifically, storing materials outdoors led to a deterioration in insulating properties, with an average reduction of about 4% for the standard materials and as much as 19% for the tested composite material. Insufficient understanding of the true thermal properties of insulation materials can result in incorrect insulation layer thickness, degrading the fundamental thermal parameters of external walls. This, in turn, increases heat loss through major building surfaces, raises heating costs, and indirectly contributes to greenhouse gas emissions. Full article