Search Results (78)

The construction sector presently consumes about 40% of global energy and generates 36% of CO₂ emissions, making facade retrofits a priority for decarbonising buildings. This review clarifies how ventilated facades (VFs), wall assemblies that interpose a ventilated air cavity between outer cladding and the insulated structure, address that challenge. First, the paper categorises VFs by structural configuration, ventilation strategy and functional control into four principal families: double-skin, rainscreen, hybrid/adaptive and active–passive systems, with further extensions such as BIPV, PCM and green-wall integrations that couple energy generation or storage with envelope performance. Heat-transfer analysis shows that the cavity interrupts conductive paths, promotes buoyancy- or wind-driven convection, and curtails radiative exchange. Key design parameters, including cavity depth, vent-area ratio, airflow velocity and surface emissivity, govern this balance, while hybrid ventilation offers the most excellent peak-load mitigation with modest energy input. A synthesis of simulation and field studies indicates that properly detailed VFs reduce envelope cooling loads by 20–55% across diverse climates and cut winter heating demand by 10–20% when vents are seasonally managed or coupled with heat-recovery devices. These thermal benefits translate into steadier interior surface temperatures, lower radiant asymmetry and fewer drafts, thereby expanding the hours occupants remain within comfort bands without mechanical conditioning. Climate-responsive guidance emerges in tropical and arid regions, favouring highly ventilated, low-absorptance cladding; temperate and continental zones gain from adaptive vents, movable insulation or PCM layers; multi-skin adaptive facades promise balanced year-round savings by re-configuring in real time. Overall, the review demonstrates that VFs constitute a versatile, passive-plus platform for low-carbon buildings, simultaneously enhancing energy efficiency, durability and indoor comfort. Future advances in smart controls, bio-based materials and integrated energy-recovery systems are poised to unlock further performance gains and accelerate the sector’s transition to net-zero. Emerging multifunctional materials such as phase-change composites, nanostructured coatings, and perovskite-integrated systems also show promise in enhancing facade adaptability and energy responsiveness. Full article

In Saudi Arabia’s hot and arid climate, residential buildings account for over half of national electricity consumption, with cooling demands alone responsible for more than 70% of this use. This paper explores the hypothesis that contemporary villa designs are inherently inefficient and that current building regulations fall short of enabling adequate thermal performance. This issue is expected to become increasingly significant in the near future as external temperatures continue to rise. The study aims to assess whether passive design strategies rooted in both engineering and architectural principles can offer substantial reductions in cooling energy demand under current and future climatic conditions. A typical detached villa was simulated using IES-VE to test a range of passive measures, including optimized window-to-wall ratios, enhanced glazing configurations, varied envelope constructions, solar shading devices, and wind-tower-based natural ventilation. Parametric simulations were conducted under current climate data and extended to future weather scenarios. Unlike many prior studies, this work integrates these strategies holistically and evaluates their combined impact, rather than in isolation while assessing the impact of future weather in the region. The findings revealed that individual measures such as insulated ceilings and reduced window-to-wall ratios significantly lowered cooling loads. When applied in combination, these strategies achieved a 68% reduction in cooling energy use compared to the base-case villa. While full passive performance year-round remains unfeasible in such extreme conditions, the study demonstrates a clear pathway toward energy-efficient housing in the Gulf region. Full article

Outdoor structures, such as vehicles, buildings, and outdoor equipment, are prone to overheat due to prolonged exposure to solar irradiation, which could affect their service life or user experience. To address this urgent issue, we developed a climate-adaptive thermal management solution using zinc oxide (ZnO)/low-density polyethylene (LDPE) hybrid membranes. The cooling performance of the membrane was examined across different seasons, achieving maximum temperature reductions ($∆T$) of 12.55 °C in summer, 8.02 °C in autumn, and 2.90 °C in winter. Our results demonstrated that the material’s cooling efficiency varied with seasonal solar irradiance, showing quicker responsiveness in summer and reduced in winter, effectively preventing overcooling. Moreover, the enclosed specific volume (SV) was identified as another critical parameter affecting cooling performance. We established an empirical correlation between $∆T$ and SV to quantify passive cooling performance across different seasons. This standardized method for assessing the cooling effect enables comparison between different materials, which is essential for determining climate-adaptive thermal management. Notably, the ZnO/LDPE membranes exhibited stable and balanced performance year-round, highlighting their potential for substantial energy savings in outdoor applications. This research provided valuable insights for designing climate-adaptive passive cooling materials that optimize thermal management across seasonal variations while contributing to sustainable energy conservation. Full article

This paper examines the impact of the urban context on the energy performance of a residential building in Athens. Current and future weather files were modified to consider the urban heat island, the overshadowing of adjacent buildings, and the modification of wind speed due to the effects of urban canyons. Dynamic thermal simulations were carried out using the modified weather files. The results indicate that there was a change in heating and cooling demand in comparison to using typical weather files; heating was reduced, but cooling was increased with a total increase in energy demand. There was variation due to height, while overshadowing impacts energy demand significantly. The modified weather analysis also indicates that there are periods in the year that cooling and heating are negligible. During these periods, passive strategies can be used to maintain good internal air quality if occupants are informed how to use their windows and shading devices according to prevailing weather conditions. A method of achieving this occupant-centric operation of the building is described, and the results of an intervention study are discussed. It shows that internal environmental quality can be improved by occupant actions based on forecast weather conditions to direct them. Full article

This paper presents the research and numerical modeling of heat flow through a textile heat sink (THS). The aim of this research is to create a numerical model of a THS that not only simulates the thermal behavior of knitted fabrics, which are used to construct a THS, but also serves as a predictive tool for the heat flow coming from different devices, thus increasing thermal management safety. By integrating modeling tools with textile engineering, this study contributes valuable insights to the development of effective passive cooling solutions for textronics applications, e.g., in thermal management in the military or air space sectors. THS is a support tool for multilayer insulation (MLI) blankets in space satellites, used to maintain the insulation performance of MLI to retain the extremely low temperature of satellite sensors or fuel tanks. The textile radiator made of spacer knitted 3D fabric consists of monofilament yarns covered with aluminum. THS samples were made on the HD 6/20-65 EL machine of Karl Mayer, with the calibration number E12. Numerical modeling was performed using ANSYS software. The numerical simulations of the temperature gradient presented the heat flow for source temperatures of 50 °C and 70 °C for different values of air velocity. Full article

Passive radiation cooling technology, as a new zero-energy refrigeration technology method, has received widespread attention in recent years. However, due to differences in the testing devices used by different teams, it becomes difficult to directly compare the cooling performance of the respective prepared materials. This study combines experimental and theoretical methods to explore the impact of testing equipment and sample size on the results of the radiative cooling capacity evaluation. The research results show that when evaluating the cooling performance of materials in thermal insulation chambers, if the sample diameter is equal to or larger than 10 cm, at a sample diameter ≥ 10 cm in insulated chambers, cooling capacity stabilizes at ~25 °C (daytime) and ~28 °C (nighttime), with <2% variation across larger sizes. The evaluation of cooling capacity is not affected by the structure of the test equipment or the size of the material. However, variations in sample placement depth will always have a significant impact on the evaluation results, so a uniform placement depth needs to be specified. In addition, when using an open device to evaluate the cooling performance of materials, if the sample diameter is greater than or equal to 10 cm and the foam pad thickness is greater than or equal to 8 cm, foam pad thickness ≥ 8 cm in open devices reduces thermal interference by 89%, enabling consistent evaluations. The measured value of the cooling capacity is also not affected by the structure and material size of the test device. This study provides a basis for the standardization of radiant cooling testing, thereby promoting the practical application of radiant cooling technology. Full article

Thermal technologies that effectively deliver thermal stimulation through skin-integrated systems and enable temperature perception via the activation of cutaneous thermoreceptors are key to enhancing immersive experiences in virtual and augmented reality (VR/AR) through multisensory engagement. However, recent advancements and commercial adoption have predominantly focused on haptic rather than thermal technology. This review provides an overview of recent advancements in wearable thermal devices (WTDs) designed to reconstruct artificial thermal sensations for VR/AR applications. It examines key thermal stimulation parameters, including stimulation area, magnitude, and duration, with a focus on thermal perception mechanisms and thermoreceptor distribution in the skin. Input power requirements for surpassing thermal perception thresholds are discussed based on analytical modeling. Material choices for WTDs, including metal nanowires, carbon nanotubes, liquid metals, thermoelectric devices, and passive cooling elements, are introduced. The functionalities, device designs, operation modes, fabrication processes, and electrical and mechanical properties of various WTDs are analyzed. Representative applications illustrate how flexible, thin WTDs enable immersive VR/AR experiences through spatiotemporal, programmable stimulation. A concluding section summarizes key challenges and future opportunities in advancing skin–integrated VR/AR systems. Full article

This paper offers an in-depth overview of the trade-off between thermal performance and assembly cost in state-of-the-art power modules (PMs). Since the development of the PM technological process is still in its infancy, PMs are typically designed and prototyped in order to evaluate their electrical/thermal characteristics. The numerical investigation conducted here aims to analyze the impact of design choices (e.g., assembly materials and dimensions, cooling system efficiency) on the thermal resistance (R_TH, [K/W]), thermal time constant (τ, [s]), and overall cost (PM_cost, [$]) of semiconductor devices integrated in both single- and double-sided cooled PMs, without any need for prototyping stages. The influence of the thicknesses of the copper and ceramic layers is explored, since they play a relevant role in defining the thermal ratings, as well as the electrical and mechanical characteristics, of the assemblies. The benefits deriving from thicker layers are then weighed against the cost of materials, and figures of merit are defined to evaluate the trade-offs between cost and thermal behavior. The impact of two cooling solutions—passive heatsink and forced liquid—is also taken into account. Full article

The building sector is a major contributor to resource consumption, energy use, and greenhouse gas emissions. Sustainable architecture offers a solution, leveraging Building Energy Modeling (BEM) for early-stage design optimization. This study explores the use of genetic algorithms for optimizing sustainable design strategies holistically. A comprehensive analysis and optimization model was developed using genetic algorithms to individually optimize various sustainable strategies. The optimized strategies were then applied to a pre-existing building in Kabul City, a region facing significant environmental challenges. To enhance accuracy, this study integrated energy simulations with Computational Fluid Dynamics (CFD). This research combines genetic algorithms with energy simulation and CFD analysis to optimize building design for a specific climate. Furthermore, it validates the optimized strategies through a real-world case study building. Optimizing the Window-to-Wall Ratio (WWR) and shading devices based on solar exposure significantly improved the building’s energy performance. South (S)-facing single windows and specific combinations of opposing and adjacent windows emerged as optimal configurations. The strategic optimization of building component materials led to substantial energy savings: a 58.6% reduction in window energy loss, 78.3% in wall loss, and 69.5% in roof loss. Additionally, the optimized pre-existing building achieved a 48.1% reduction in cooling demand, a 97.5% reduction in heating demand, and an overall energy reduction of 84.4%. Improved natural ventilation and controlled solar gain led to a 72.2% reduction in peak-month CO₂ emissions. While this study focused on applicable passive design strategies, the integration of advanced technologies like Phase Change Materials (PCMs), kinetic shading devices, and renewable energy systems can further improve building performance and contribute to achieving net-zero buildings. Full article

The performance of photovoltaic (PV) cells is significantly influenced by their operating temperature. While conventional active cooling methods are limited by economic feasibility, passive cooling strategies often face challenges related to insufficient heat dissipation capacity. This study presents a bio-inspired evaporative heat sink, modeled on the transpiration and water transport mechanisms of plant leaves, which leverages porous media flow and heat transfer. The device uses capillary pressure, generated through the evaporation of the cooling medium under sunlight, to maintain continuous coolant flow, thereby achieving effective cooling. An experimental setup was developed to validate the device’s performance under a heat flux density of 1200 W/m², resulting in a maximum temperature reduction of 5 °C. This study also investigated the effects of porous medium thickness and porosity on thermal performance. The results showed that increasing the thickness of the porous medium reduces cooling efficiency due to reduced fluid flow. In contrast, the effect of porosity was temperature-dependent: at evaporation temperatures below 67 °C, a porosity of 0.4 provided better cooling, while at higher temperatures, a porosity of 0.6 was more effective. These findings confirm the feasibility of the proposed device and provide valuable insights into optimizing porous media properties to enhance the passive cooling of photovoltaic cells. Full article

An efficient cooling system is necessary for the reliability and safety of modern microchips for a longer life. As microchips become smaller and more powerful, the heat flux generated by these chips per unit area also rises sharply. Traditional cooling techniques are inadequate to meet the recent cooling requirements of microchips. To meet the current cooling demand of microelectromechanical systems (MEMS) devices and microchips, microchannel heat sink (MCHS) technology is the latest invention, one that can dissipate a significant amount of heat because of its high surface area to volume ratio. This study provides a concise summary of the design, material selection, and performance parameters of the MCHSs that have been developed over the last few decades. The limitations and challenges associated with the different techniques employed by researchers over time to enhance the thermal efficiency of microchannel heat sinks are discussed. The effects on the thermal enhancement factor, Nusselt number, and pressure drop at different Reynold numbers in passive techniques (flow obstruction) i.e., ribs, grooves, dimples, and cavities change in the curvature of MCHSs, are discussed. This study also discusses the increase in heat transfer using nanofluids and how a change in coolant type also significantly affects the thermal performance of MCHSs by obstructing flow. This study provides trends and useful guidelines for researchers to design more effective MCHSs to keep up with the cooling demands of power electronics. Full article

Air renewal rate is an important parameter for both indoor air quality and thermal comfort. However, to improve indoor thermal comfort, the air renewal rate to be used, in general, will depend on the outdoor air temperature values. This article presents the modelling of indoor air quality and thermal comfort for occupants of a passive building subject to a climate with warm conditions. The ventilation and shading strategies implemented for the interior spaces are then considered, as well as the use of an underground space for storing cooled air. The indoor air quality is evaluated using the carbon dioxide concentration, and thermal comfort is evaluated using the Predicted Mean Vote index. The geometry of the passive building, with complex topology, is generated using a numerical model. The simulation is performed by Building Thermal Response software, considering the building’s geometry and materials, ventilation, and occupancy, among others. The building studied is a circular auditorium. The auditorium is divided into four semi-circular auditoriums and a central circular space, with vertical glazed windows and horizontal shading devices on its entire outer surface. Typical summer conditions existing in a Mediterranean-type environment were considered. In this work, two cases were simulated: in Case 1, the occupation is verified in the central space and the four semi-circular auditoriums and all spaces are considered as one; in Case 2, the occupation is verified only in each semi-circular auditorium and each one works independently. For both cases, three strategies were applied: A, without shading and geothermal devices; B, with a geothermal device and without a shading device; and C, with both shading and geothermal devices. The airflow rate contributes to improving indoor air quality throughout the day and thermal comfort for occupants, especially in the morning. The geothermal and shading devices improve the thermal comfort level, mainly in the afternoon. Full article

The use of wide band gap (WBG) semiconductor switches in power converters is increasing day by day due to their superior chemical and physical properties, such as electrical field strength, drift speed, and thermal conductivity. These new-generation power switches offer advantages over traditional induction cooker systems, such as fast and environmentally friendly heating. The size of passive components can be reduced, and the decreasing inductance value of induction coils and capacitors with low ESR (equivalent series resistance) values contributes to total efficiency. Other design parameters, such as passive components with lower values, heatsinks with low volumes, cooling fans with low power, and induction coils with fewer turns, can offset the cost of WBG power devices. High-frequency operation can also be effective in heating non-ferromagnetic materials like aluminum and copper, making them suitable for heating these types of pans without complex induction coil and power converter designs. However, the use of these new generation power switches necessitates a re-examination of induction coil design. High switching frequency leads to a high resonance frequency in the power converter, which requires lower-value passive components compared to conventional cookers. The most important component is the induction coil, which requires fewer turns and magnetic cores. This study examines the induction heating equivalent circuit, discusses the general structure and design parameters of the induction coil, and performs FEM (finite element method) analyses using Ansys Maxwell. The results show that the induction coil inductance value in new-generation cookers decreases by 80% compared to traditional cookers, and the number of windings and magnetic cores decreases by 50%. These analyses, performed for high-power applications, are also performed for low-power applications. While the inductance value of the induction coil is 90 μH at low frequencies, it is reduced to the range of 5 μH to 20 μH at high frequencies. The number of windings is reduced by half or a quarter. The new-generation cooker system experimentally verifies the coil design based on the parameters derived from the analysis. Full article

Air-source heat pumps (ASHPs), as an active device, are widely used in building heating and cooling processes. However, in severe cold regions, they face reduced heating efficiency and frosting problems in winter. This paper proposes a new heating solution by coupling an ASHP with passive heating systems. It combines an ASHP with passive sunrooms and heat storage systems for heating. Through software simulations and mathematical modeling, the new scheme is compared and analyzed against traditional ASHP solutions to explore the performance of this scheme in rural houses in severe cold regions of China during winter. According to simulation and calculation analysis, on the coldest day of winter, the coupling scheme can provide approximately 99.41 kWh of heat to the indoors, which exceeds the 86.67 kWh required to maintain an indoor temperature of 20 °C. The system’s power consumption is 36.96 kWh, which is 66.88% lower than that of traditional heat pump heating. The study shows that the coupling system of an ASHP and passive heating has a good heating effect in severe cold regions. For the situation of insufficient solar energy at night, the design of phase-change materials and heat storage media can meet heating needs throughout the day. Full article

To mitigate greenhouse gas emissions responsible for global warming and climate change, governments have undertaken concerted efforts and established goals to restructure production and consumption patterns within the current global economy. The construction sector, which in Europe has significant energy use and related greenhouse gas emissions, recognizes adopting passive heating and cooling systems for buildings as a viable solution. The revival of vernacular passive solar strategies emerges as opportune within this context. Through dynamic simulations, this study aims to analyze and quantify the potential contribution of glazed balconies, a traditional passive heating system, to improve contemporary constructions’ thermal behavior and comfort conditions in mild temperate climates, such as in northern Portugal. Results indicate that this system can significantly enhance a building’s energy efficiency, reducing energy needs for heating and cooling by up to 47% while extending periods of thermal comfort indoors by nearly 900 h per year compared to buildings with non-glazed balconies. Proper use of natural ventilation and shading devices is essential to ensure optimal system performance and prevent overheating. This research underscores the potential of glazed balconies as a sustainable solution for enhancing contemporary buildings’ thermal-energy performance and comfort, contributing to the transition towards carbon-neutral constructions. Full article