Transparent Envelope Research Articles

Effects of non-uniform perforated solar screen on daylighting and visual comfort performance

Perforated solar screens are extensively utilized as a shading solution for fully glazed buildings and transparent envelope systems. While uniform perforated solar screens have been traditionally employed, the growing trend towards non-uniform screens highlights their potential to enhance architectural aesthetics through varied perforation patterns on building facades. However, the effects of non-uniform screens in daylighting performance have been rarely investigated. This study aims to assess the effects of non-uniform perforated solar screens on daylighting performance, encompassing daylight availability, uniformity, and annual glare probabilities. A comparative analysis was conducted using simulation studies for eight distinct non-uniform perforation patterns against a uniform perforation scenario. Orthogonal experiment and data envelopment analysis were employed to identify the influential factors and evaluate the overall performance. The results suggest that non-uniform perforated solar screens with specific perforation patterns significantly outperform uniform screens in terms of daylighting performance, at equal perforation ratios. Specifically, two non-uniform prototypes, namely (h) periphery-center and (f) bottom-top, demonstrated exceptional performance. Furthermore, the perforation pattern was identified as the most significant geometrical factor affecting the overall performance of daylighting and glare discomfort. The results of this study may inform the design of perforation patterns to enhance daylighting performance in non-uniformly perforated solar screens. The novelty of this research lies in establishing a framework for evaluating the influence of non-uniform perforation patterns on indoor daylighting and visual comfort.

Influence of Transparent Envelope Parameters on Office Building Energy Use Intensity in the Different Thermal Climate Regions of China

The role of the transparent envelope in energy savings is crucial as it accounts for a significant proportion of the total energy loss (between 30 and 40%). This paper focuses on the identification of reasonable parameters for the transparent envelope in different climatic regions. To achieve this goal, typical urban office buildings from four different climatic regions are used as research objects. A total of 1600 scenarios were simulated to investigate the variation of energy use intensity, including transparent envelope parameters, meteorological parameters and different types of glazing. The results show that for south-facing transparent envelope facades, type D glazing is the most energy efficient in severe cold regions, type C in colder regions and type B in the other two climatic regions. No solar shading is required in the very cold region. Horizontal shading can be an effective method for saving energy in colder climates, while comprehensive shading can be beneficial in other regions. Deep shading is particularly energy efficient if it meets lighting requirements. For example, in Guangzhou, energy savings of 13.46%, 15.47%, 7.01% and 7.02% can be achieved in the east, west, south and north directions, respectively, using B-type glazing and a comprehensive shading depth of 900 mm.

Multi-objective optimization for the daylighting and thermal comfort performance of elevated subway station buildings in cold climate zone of China

The rapid development of urban rail transit brings about the rapid growth of elevated subway station buildings, while the demand for comfortable waiting environments on the passenger platforms is also increasing. Due to the fact that elevated stations generally have a transparent envelope, there is a contradiction between daylighting, heating, and air conditioning. Therefore, multi-objective optimization design is essential. This article selects the cold regions of northern China as the research object. A field investigation was carried out, and Tianjin University Town Station was found to be a typical station in cold climate zone of China. A prototypical model was built based on it using Grasshopper in Rhino. Sensitivity analysis was used to screen key independent variables, and strength Pareto evolutionary algorithm II was used to optimize the daylighting and thermal comfort performance for the elevated subway station buildings. Two optimization processes, step-by-step and one-step, were used to obtain the non-dominated solution set, and the optimal solution was obtained by technique for order preference by similarity to an ideal solution analysis. The suggested values for the design variables of the prototypical model are also displayed. Reducing the skylight's window-to-wall ratio helps improve daylighting and thermal comfort. Besides, the one-step optimization method has higher efficiency and can obtain better results. The findings proposed here can guide the development of elevated subway station buildings in north China and other areas with similar conditions.

New solar radiation transmittance models of transparent envelope based on spectral splitting and their influence on building heat gain

Climate change and the energy crisis have led to increasing attention to building energy efficiency worldwide, and transparent envelopes are more critical as a weak link in building energy efficiency. However, there is a lack of quantitative research on the spectral transmittance properties of transparent envelopes. In this paper, the spectral transmittance of transparent envelopes is quantitatively studied using the controlled variable method. The transmittance calculation formula in the existing standard is modified. Firstly, five types of transparent envelopes commonly used are selected, and their transmittance to the full solar spectrum is studied to establish a transmittance model for different wavelengths. The study also focuses on the 300 nm–1100nm waveband and establishes a solar radiation transmittance benchmark model (SRTB model) based on single-pane clear glass. Secondly, the solar radiation transmittance at different wavelengths is tested by considering both the glass material and the inclination angle, and a solar radiation transmittance modified model (SRTM model) that can be modified to the SRTB model is established. Thirdly, the variation between the incident angle and transmittance is investigated, and the solar radiation transmittance-incident angle model (SRT - IA model) is developed. The results show that deviations between the fixed transmittance and SRT - IA model can reach a maximum of more than 10% for incident angles of less than 60°. Finally, the variation in radiation heat gain due to the SRT - IA model and fixed transmittance is compared in China based on typical meteorological year data. The research conclusion can provide a more precise assessment of the building heat gain from transparent envelopes and then evaluate the building energy consumption reasonably, and provide a theoretical basis for the full-spectrum utilization efficiency of solar radiation.

Assessment of the Incentive Rate to Favor the Energy Retrofit of Public Buildings: A Comprehensive Approach for an Italian University Facility

The Renovation Wave for Europe highlighted the role of the public building stock for which Directive 2012/27/EU has set an annual renewal rate of 3%, which should rise to reach the goal of decarbonization by 2050. In this paper, the energy retrofit of an educational building—at the academic level—in Southern Italy was investigated. The aim was to evaluate the incentive share, which could accelerate the energy efficiency process, to achieve a cost-effective nZEB. The results show that the highest incentive rate is required for interventions on the opaque building envelope, which are also those that allow the least energy savings. An incentive rate of about 45% for the energy efficiency of the transparent envelope is necessary to reduce the payback time by about 7 years. The efficiency of the plants and the installation of a PV system are energetically and economically convenient even without forms of economic incentive. Finally, if the building is brought to high energy standards—a primary energy saving of 46% and energy class A3—an incentive rate of 40% is required to repay the intervention in about 10 years.

Application of CPMV* for improving the indoor thermal environment under global solar radiation

The impacts of solar radiation on indoor thermal comfort are growing with the popularity of curtain walls in modern constructions. In order to accurately assess indoor thermal comfort under global solar radiation, a previous study proposed a corrected predicted mean vote with global solar radiation (CPMV*) and validated the model in summer. To further investigate the year-round applicability of the model, field experiments were conducted in transparent envelope buildings in winter, and 1098 valid thermal responses were obtained. The results indicate that CPMV* fits well with the thermal sensation vote, and it has important applications in guiding the design of indoor thermal environments and the operation of ventilation and air conditioning systems throughout the year. Besides, the predicted percentage dissatisfied with global solar radiation and the percentage unacceptable are proven to be feasible in evaluating the thermal acceptability of buildings with solar radiation. Based on CPMV*, we can calculate the indoor thermal comfort zone matching various solar radiation intensities and reasonably regulate the actual operation of the heating, ventilation and air conditioning systems. The indoor thermal environment exposed to solar radiation would be significantly improved by these findings.

A review and prospect on research progress of adjustable transparent envelope

A review and prospect on research progress of adjustable transparent envelope

Experimental Analysis of Evacuation Pressure and Gas Flow Rate in Structured-Core Transparent Vacuum Insulation Panels

The notion that modern buildings should strive to be net zero energy buildings (NZEBs) is widely accepted. One of the causes leading to high energy usage for space heating, resulting in avoidable carbon emissions, is heat loss via building windows. In order to improve window’s insulation in existing buildings, structured-core transparent vacuum insulation panels (TVIPs) are proposed. TVIPs mainly consist of the structured core material, the low-emissivity film, and the transparent gas barrier envelope. TVIPs have high insulation performance and are inexpensive to manufacture and can be easily installed. Therefore, TVIPs have potential to improve window’s insulation in existing buildings with low cost. However, it is necessary to overcome the issue of preventing the pressure rise inside TVIP after vacuum sealing. The authors constructed an experimental setup to quantify the effect of reduction of gas flow rate in TVIP after evacuation by applying pressure-rate-of-rise-method. In this experiment, a gas barrier film with a straw was used as the vacuum chamber. This could reproduce the pressure increase in the TVIP after sealing and the gas flow rate in the TVIP is evaluated. The experimental result show that the coated core material and the enclosing getter agentlowered the pressure rise and gas flow rate in TVIP by combining concurrent evacuation and heating. Furthermore, after extending the simultaneous vacuuming and heating period to 8 hours and applying the coated core material and enclosing the gettering agent, the internal pressure in TVIP may be lowered to around 1 Pa after 30 minutes after halting vacuuming. It was confirmed that this pressure satisfied the performance required for TVIPs, and the result was much closer to the realization of TVIPs.

Modeling, Simulation and Testing of Atomization Temperature Change Point of Thermochromic Glass for Building Energy Saving

Thermochromic glass possesses great potential for reducing the energy demand and providing indoor comfort in buildings. Suitable atomization temperature change points have a great influence on the application of thermochromic glass. Based on energy consumption simulations and theoretical calculations by introducing solar radiation in a transparent envelope, this paper investigates the atomization temperature change point of thermochromic glass in hot summer and cold winter zones in Chongqing, showing that the suitable temperature change point of the thermochromic glass is 39°C with air conditioning and 42.9°C without air conditioning. Furthermore, the results of simulations and theoretical calculations are applied to a test model, revealing that thermochromic glass with the temperature change point of 42.9°C compared with Low-E glass can reduce the temperature of a sunlight room by up to 5°C in the summer and displays a certain thermal insulation effect in winter.

Implicit method for solving building heat transfer model and its application in energy-saving materials

In this work, implicit method is used to solve the building heat transfer equations in order to improve the speed and stability of calculation. It only takes 161.906 s to calculate the annual data when the time step is 6 min in the specific calculation example. In addition, the effective heat capacity method is used to independently model the building module containing phase change materials (PCMs), which can accurately simulate the temperature distribution of each node inside PCMs. Therefore, the temperature changes of different nodes in PCM and the utilization efficiency of PCM can be analyzed. Radiative heat transfer in buildings can be considered separately so that it can be distinguished from convective heat transfer. The radiation characteristics of the envelopes can also be modified, which means that smart windows can be studied by changing the radiation characteristics of the transparent envelope. Combined with these calculation characteristics, a software called BuildingEnergy is proposed. At present, the reliability of the software has been proved by ANSI/ASHRAE Standard 140–2001. A set of experimental device was set up in Hefei (China), and through the comparison with the simulation results, it was found that the software has high reliability under both active and passive mode. Moreover, it has a high accuracy in simulating the performance of phase change materials and vanadium dioxide films in buildings.

Dynamic coupled heat transfer and energy conservation performance of multilayer glazing window filled with phase change material in summer day

Windows as indispensable for buildings play an important role in decreasing building energy consumption and improving indoor thermal comfort. However, the conventional windows made of the pure glazing units fail to meet the requirements of energy conservation for buildings due to poor thermal insulation. Recent researches found that the application of phase change materials (PCM) can improve the heat transfer performance of glazing unit and the PCM-filled glazing units have advantage in reducing building energy consumption and improving indoor thermal comfort. Therefore, the dynamic coupled heat transfer and energy conservation performance of PCM-filled multilayer glazing unit are investigated numerically in this work. A transient coupled heat transfer model considering conduction, phase change and solar radiation transfer in glazing unit is established, and the energy conservation performance is analyzed based on the heat transfer calculation. Results show that the PCM-filled multilayer glazing unit can significantly reduce energy consumption compared with pure glazing unit, and the energy saving rates are 14.55% for double glazing unit, 33.89% for triple glazing unit and 50.71% for four glazing unit, respectively. In addition, the effects of optical and thermal parameters of PCM on thermal performance of glazing units are investigated thoroughly. It is found that the PCM-filled multilayer glazing unit has advantages in thermal insulation which is good choice for transparent envelope in the building fields.

Identification of Sperm-Binding Sites in the N-Terminal Domain of Bovine Egg Coat Glycoprotein ZP4.

The species-selective interaction between sperm and egg at the beginning of mammalian fertilisation is partly mediated by a transparent envelope called the zona pellucida (ZP). The ZP is composed of three or four glycoproteins (ZP1–ZP4). The functions of the three proteins present in mice (ZP1–ZP3) have been extensively studied. However, the biological role of ZP4, which was found in all other mammals studied so far, has remained largely unknown. Previously, by developing a solid support assay system, we showed that ZP4 exhibits sperm-binding activity in bovines and the N-terminal domain of bovine ZP4 (bZP4 ZP-N1 domain) is a sperm-binding region. Here, we show that bovine sperm bind to the bZP4 ZP-N1 domain in a species-selective manner and that N-glycosylation is not required for sperm-binding activity. Moreover, we identified three sites involved in sperm binding (site I: from Gln-41 to Pro-46, site II: from Leu-65 to Ser-68 and site III: from Thr-108 to Ile-123) in the bZP4 ZP-N1 domain using chimeric bovine/porcine and bovine/human ZP4 recombinant proteins. These results provide in vitro experimental evidence for the role of the bZP4 ZP-N1 domain in mediating sperm binding to the ZP.

Multi-Objective Optimization of Transparent Building Envelope of Rural Residences in Cold Climate Zone, China

Multi-Objective Optimization of Transparent Building Envelope of Rural Residences in Cold Climate Zone, China

Influence of different building transparent envelopes on energy consumption and thermal environment of radiant ceiling heating and cooling systems

In this study, the energy consumption and indoor thermal environment of a radiant ceiling heating and cooling system with three types of transparent building envelopes, namely, ordinary insulating glass (OIG), heat reflective insulating glass (HFIG) and triple silver low-e insulating glass (TSIG), were investigated and compared by experiment and simulation. The annual energy consumption and thermal environment distribution of the radiant ceiling system equipped with the three types of transparent envelope in five different climate zones were obtained. The results show that the energy saving rates of HFIG and TSIG windows are −9.78% to 48.00% and 8.82–63.65% in the five climate zones, compared to the OIG window. It is seen that the TSIG window has greater energy-saving potential in both heating dominant and cooling dominant climate zones. In addition, the annual average air temperature of the room with TSIG window is more stable, which means the thermal environment level is better. It is also found that the response of radiant ceiling system to solar heat gain is different in summer and winter. It has a good response to cooling, and it can timely take away the influence of solar heat gain through the radiation heat transfer. Therefore, the indoor thermal environment level of the rooms with different transparent envelopes has little difference during the cooling season. However, as the response of radiant ceiling systems to heating is poor, the indoor thermal environment is greatly affected by the outdoor parameters and varied with the transparent envelopes. Hence, adopting the transparent envelopes with high performance is preferred in the heating dominant zones.

Performance of a Solar Spectrum-Selective Absorption Film as a Building Energy-Saving Retrofit in China.

The transparent envelope structures in existing buildings have caused so much energy consumption. As one kind of the energy-saving technologies and strategies, the solar spectrum selective absorption film (SSAF) is considered suitable for the retrofit of glazing systems. The energy-saving performance of the SSAF in different types of glazing systems under different climate zones in China was investigated via a field study and simulation experiment. The results indicated that SSAF slowed down the rise of indoor air temperature in the daytime and reduced the total energy entering the room. The effect of the SSAF on the single glazing system was more potent than that on the double glazing system. In the hot summer and cold winter zone, moderate zone, hot summer and warm winter zone, the SSAF could reduce the energy consumption of windows. The highest energy-saving rate reached 35.0% for the single glazing system and 28.3% for the double glazing system. However, the SSAF does not have the energy-saving potential in existing buildings that already have low-E double glazing systems.

Solar greenhouses: Climates, glass selection, and plant well-being

Solar greenhouses are currently the most energy-intensive agricultural sector. In literature, there is no worldwide mapping of solar greenhouse performance under different climate scenarios. This study analyzes the performance of a Venlo solar greenhouse for 48 localities around the world. Solar greenhouses are mainly made of a transparent envelope and the effect of the direct and diffuse component of solar radiation impacts the internal plant well-being. This study aims to identify the best solution of a transparent envelope on locations with different latitudes and evenly distributed around the globe. The simulations are carried out using TRNsys, considering different thermal phenomena three-dimensional shortwave and longwave radiative exchange, airflow exchanges, presence of lamps with their exact 3D position, ground, plant evapotranspiration, and convective heat transfer coefficients. A total of 336 simulations are performed in the free-floating regime. A new index for the identification of the best glass solutions based on annual average deviation is defined. For all climates, the best glass solutions work better in winter than in summer. The optimal choice of the glass must be combined with effective scheduling of openings for natural ventilation to avoid internal overheating phenomena.

Analysis of the CPMV index for evaluating indoor thermal comfort in southern China in summer, a case study in Nanjing

With the rapid development of building technology, transparent envelope is more and more widely used, which makes the indoor environment of buildings more and more affected by solar radiation. However, the effects of solar radiation are not included in the PMV model. The Corrected Predicted Mean Vote (CPMV) model considering solar radiation was previously proposed and verified in northern China. In order to expand the applicability of the CPMV model to the hot summer and cold winter (HSCW) zone of southern China, a field study was conducted in an office building in Nanjing. A total of 686 valid questionnaires were recovered during the surveys in two summers in 2019 and 2020. The results show that the evaluation value of CPMV is highly consistent with the actual thermal sensation vote (TSV) when the corrected operative temperature is below 30 °C. However, when the corrected operative temperature is above 30 °C, the CPMV value is higher than TSV, because it underestimates the tolerance of human body to the hot environment in Nanjing. The thermal neutral temperature is 26.12 °C (CPMV) and 26.28 °C (TSV) respectively, which is higher than that in winter and summer in northern China. This study fills the blank in the application of CPMV model in southern China. The CPMV model can accurately evaluate the thermal comfort of indoor environment affected by solar radiation, which is worthy of promotion and application to other types of buildings and areas.

The thermal potential of a new multifunctional sliding window

Nowadays, new generations of building envelope need to manage the energy exchange between outdoor and indoor environment responsively and save the building energy. A significant amount of solar heat gain in buildings comes through the windows. The transparent envelope also must answer to visual requirements allowing for external vision but guarantying comfort conditions. In this framework, this article aims to test numerically the thermal performance of a new design of multifunctional glazed window combining the most recent technologies used in building envelopes. Five distinct window designs combing phase change material (PCM), vacuum glazing (VG), photovoltaic (PV), and air cavity were numerically tested for hot weather conditions. The proposed window designs slide inside the wall of the building. A comprehensive transient Multiphysics model coupling the thermo-electric model of the PV, melting and solidification model of the PCM, and the heat transfer mechanisms in the vacuum and air gaps are developed. The model is step by step validated with data in the literature. Various PCM types and PCM thickness are investigated. Among the five investigated window designs, the result showed that the window, including the air gap with PV, PCM cavity, and VG, is the optimal design for the indoor air's thermal isolation. Simultaneously, the PCM with a melting point of 35 ˚C and thickness of 50 mm is the best performance material in a hot arid region in summer at Cairo. The proposed multifunction window generated maximum electrical power intensity of 162 W/m2 at received solar radiation of 1000 W/m2.

Study on dynamic thermal behavior of double glazing unit filled with phase change materials

Glazing units are indispensable for a variety of buildings and their thermal behavior has significant effects on improving indoor thermal comfort and decreasing energy consumption. Recently, the double glazed windows that are filled with phase change material (PCM) have been considered as potential glazing units. Therefore, the dynamic thermal behavior of the PCM-filled double glazing unit is investigated in this work. A three-layer glass-PCM-glass model considering coupled conduction-solar radiation-phase change is established. Effects of physical parameters of the PCM on the thermal behavior of the PCM-filled glazing unit are examined thoroughly. The results indicate that the filling of PCM can affect heat transfer within the glazing unit significantly by reducing solar energy entering the indoor room through the window. When the glass-PCM-glass model is adopted, the transmitted solar energy can be reduced by 78.82 W/m2. Optical parameters (especially absorption coefficient) of the PCM have significant impact on the thermal behavior of glazing units: the larger the absorption coefficient is, the less solar energy will enter indoors, and the larger will be the temperature fluctuation. For different absorption coefficients, the maximum temperature difference on the interior surface can reach 3.57°C. Thermal properties of the PCM also have significant impact on the thermal behavior of glazing units. Decreasing the thermal conductivity or increasing the latent heat of the PCM can reduce the temperature fluctuation of the glazing windows. Selecting a reasonable melting temperature can make full use of the heat storage capacity of PCM. Thus, this study can provide a reference for how to apply PCM into a transparent envelope in buildings.

Sperm-binding regions on bovine egg zona pellucida glycoprotein ZP4 studied in a solid supported form on plastic plate.

The zona pellucida (ZP) is a transparent envelope that surrounds the mammalian oocyte and mediates species-selective sperm–oocyte interactions. The bovine ZP consists of the glycoproteins ZP2, ZP3, and ZP4. Sperm-binding mechanisms of the bovine ZP are not yet fully elucidated. In a previous report, we established the expression system of bovine ZP glycoproteins using Sf9 insect cells and found that the ZP3/ZP4 heterocomplex inhibits the binding of sperm to the ZP in a competitive inhibition assay, while ZP2, ZP3, ZP4, the ZP2/ZP3 complex, and the ZP2/ZP4 complex do not exhibit this activity. Here, we show that bovine sperm binds to plastic plates coated with ZP4 in the absence of ZP3. We made a series of ZP4 deletion mutants to study the sperm-binding sites. The N-terminal region, Lys-25 to Asp-136, and the middle region, Ser-290 to Lys-340, of ZP4 exhibit sperm-binding activity. These results suggest that among the three components of bovine ZP glycoproteins, ZP4 contains the major potential sperm-binding sites, and the formation of a multivalent complex is necessary for the sperm-binding activity of ZP4.