Indoor Solar Radiation Research Articles

Coordination Compound Guided a Novel Composite Film with Zn2V2O7 Nanoflake and VO2@Zn2V2O7 Nanoparticle for Enhanced Thermochromism Smart Window.

Thermochromic vanadium dioxide (VO2) can intelligently modulate the transmittance of indoor solar radiation to reduce the energy consumption of air conditioning in buildings. Nevertheless, it remains a great challenge to simultaneously improve the luminous transmittance (Tlum) and solar modulation ability (ΔTsol) of VO2. In this study, a novel approach is employed utilizing a coordination compound to finely tune the growth of a VO2 based composite film, yielding a hierarchical film comprising Zn2V2O7 nanoflakes and VO2@Zn2V2O7 core-shell nanoparticles. Remarkably, the resulting composite films showcase exceptional optical performance, achieving a Tlum of up to 73.0% and ΔTsol of 15.7%. These outcomes are attributed to the antireflection properties inherent in the nanoflake structure and the localized surface plasmon resonance of well-dispersed VO2 nanoparticles. In addition, the Zn2V2O7-VO2 film demonstrates remarkable environmental durability, retaining 90% of its initial ΔTsol even after undergoing aging at 100°C under 50% relative humidity for a substantial period of 30 days - a durability equivalent to ≈20 years under ambient conditions. This work not only achieves a harmonious balance between Tlum and ΔTsol but also introduces a promising avenue for the design of distinctive composite nanostructures.

Optical responsive asphalt coating with temperature-sensitive TiO2 quantum dots: Formula and temperature adaptability

The application of conventional asphalt contributes to extremely high pavement temperature in hot season as its black color entails large solar absorption. In this study, optical responsive asphalt is proposed to control pavement temperature, which is developed by introducing temperature-sensitive TiO2 quantum dots (TiO2 QDs) into traditional asphalt. Temperature-sensitive TiO2 QDs are prepared by blending thermochromic polymer and TiO2 quantum dots with varied concentrations. Optical characterizations on temperature-sensitive TiO2 QDs have demonstrated that peak value of solar absorption in temperature-sensitive TiO2 QDs at 45 °C is 14.29 %–22.86 % higher than that at 15 °C; the maximum fluorescent intensity of temperature-sensitive TiO2 QDs at 45 °C is 8.5 % higher than that at 15 °C. The results from optical characterizations on temperature-sensitive TiO2 QDs modified asphalt show that the incorporation of temperature-sensitive TiO2 quantum dots endows asphalt low solar reflectance at high temperature and high solar absorption at low temperature. Fluorescent intensity of modified asphalt at 45 °C is increased by 21.6 %, 10.2 % and 5.7 % than that at 15 °C for asphalt containing 5 %, 10 %, and 20 % temperature-sensitive TiO2 QDs, respectively. Indoor solar radiation simulation tests have revealed that compared with traditional asphalt, temperature-sensitive TiO2 QDs modified asphalt coating could yield cooling effectiveness of 6.4 °C at high temperature. Meanwhile, outdoor solar radiation test indicates TiO2 QDs modified asphalt coating could realize warming effectiveness of 0.7 °C at low temperature. The outcomes on temperature-sensitive TiO2 QDs modified asphalt with temperature-adaptability properties makes an advancement in functional pavement.

An Analysis of the Influence of Construct Parameters on the Solar Radiation Input in an Insulated Plastic Greenhouse

Insulated plastic greenhouses (IPG) were a new type of facility emerging in production in China. The mechanism of construct parameters on the indoor solar radiation deserves further study. A mathematical model that can well describe the spatial and temporal distribution of solar radiation in the greenhouse was established. Based on this model, the effects of multiple construct parameters, such as insulation blanket shading, height–span ratio, greenhouse azimuth, and geographical latitude, on the indoor solar radiation of IPG were quantitatively specified. The results showed that the spatial and temporal distribution of inside solar radiation was highly variable along the span direction of IPG. And by analyzing the simulation data, it was found that for different heights of greenhouses, the corresponding optimal span is different. Therefore, in the construction of greenhouses, the appropriate height–span ratio should be selected according to the planting demand. And by simulating the inside solar radiation under different greenhouse azimuth angles, it was found that accumulated daily solar radiation in the greenhouse reaches the optimum value when the greenhouse azimuth angle is in the range of 0–20°. This paper can provide theoretical guidance for the design and optimization of structure parameters of IPG in China.

Effects of the clothing colors on heat transfer and thermal sensation under indoor solar radiation in winter

The clothing color could always produce different human heat transfer and thermal sensation under solar radiation. And this issue has already been scrutinized by a few studies in outdoor environment. As the natural lighting is becoming common in buildings, e.g. the large curtain walls in high-rise buildings, the direct solar radiation could also affect the indoor occupants. Consequently, effects of the clothing color on the human body could not be ignored. Unfortunately, very limited studies have been reported in this field. In order to acquire the contribution of the clothing color to the heat transfer and thermal sensation of the indoor occupants, experimental study was conducted in this paper. Firstly, considering the non-uniformity of direct solar radiation on the indoor occupants, the equations that were used to calculate the solar heat gain of different body segments and the clothing surface temperature were revised, respectively. Thereafter, an experimental study was conducted in a climate chamber in winter. Participants wore cloth with different colors when exposed to different solar radiation intensities, during which the mean skin temperature, heat transfer, and subjective evaluations were acquired. Results showed that the dark clothing led to the reduced total heat loss by 4.52%, compared with that of the light clothing, at the solar radiation intensity of 200 W/m2. And the mean thermal sensation vote (TSV) under dark clothing was 0.65 higher than that under the light clothing. Meanwhile, at the solar radiation of 400 W/m2, the total heat loss under dark clothing was 14.17% lower than that under the light clothing, and the mean TSV under the dark clothing was found to be 0.25 higher that under light clothing condition. The results implied that wearing the dark clothing could benefit the improvement of the indoor human thermal comfort at low solar radiation in winter. These findings could provide a few useful references for studies on indoor thermal comfort under the solar radiation.

Experimental investigation of indoor lighting/thermal environment of liquid-filled energy-saving windows

To enhance the effectiveness of energy-saving buildings, windows play a crucial role, as they contribute to comfort, energy efficiency, and adaptability. However, traditional static windows, which primarily focus on reducing solar radiation, struggle to strike a balance between heating/cooling requirements during winter and summer seasons. On the other hand, dynamic windows, while offering adjustability, suffer from issues such as high haze and poor color rendering, making them less suitable for residential buildings. In this study, we propose a novel reversible liquid-filled energy-saving window that effectively regulates indoor solar radiation heat gain. To evaluate the dynamic indoor light/heat environment provided by liquid-filled energy-saving windows, we conduct an experimental investigation. Results indicate that windows filled with 10 wt% and 20 wt% CuSO4 solution cause a 1.5 °C and 2.5 °C reduction in indoor mean air temperature compared to water-filled windows during the summer season. Similarly, in the winter season, the decrease is 1.4 °C and 0.5 °C, respectively. Moreover, there is no significant difference in indoor illuminance between energy-saving windows filled with 10 wt% and 20 wt% CuSO4 solution. With the mass concentration of 10%wt CuSO4 solution, indoor mean illuminance difference between the two groups is only 236 lux and 214 lux during the summer and winter seasons, respectively.

Towards Sustainable Indoor Thermal Comfort in the Tropical Building Design: Comparative Performance Analysis of Fixed External Shading Elements and Differential Window Glass Thermal Properties

Tropical region is characterised by high outdoor solar radiation and temperature. These radiations penetrate into the interior particularly through the window glazing, thereby raising the indoor temperature with a resultant effect on high cooling energy demand (for comfortable indoor living condition). Of the identified three sustainable approaches towards inhibiting direct incoming indoor solar penetration in the tropical city of Ogbomoso, Nigeria, this study, through computer-based simulation technique, compared performance effectiveness of varying design interventions on the window composition/material adopted. Through multiple/iterative building performance simulation tool, DesignBuilder, the methodology involves virtual model of a three-bedroom residential building, typical of the prevailing building typology in the study area. This particular model served as the experimental control model. Three (3) variants of the control model, each with either externally mounted shading devices on the building envelope, or improved thermally resistant multilayer window glazing (i.e., double glazing) or low-emissivity coated window glazing material, were generated for individual performance effectiveness evaluation. All the four models were subjected to a twelve-month simulation cycle, to experience a year-round thermal conditions and evaluations individually. The results show that double-glazing window installation proved to be the most effective approach, with about 13.1 % improvement (i.e., solar radiation inhibition) on the indoor thermal gains. This is followed by the externally mounted shading devices (i.e., 11.1 % improvement) and the least inhibition (i.e., 5.0 %) was observed in the case of low-emissivity coated window glazing material. Adoption of double or more layers of glass panes in window fabrication for controlling indoor solar radiation penetration is therefore advised. Alternatively, integration of external window shading elements could be adopted. This study is directed towards reduction of cooling energy consumption in tropical buildings through efficient and sustainable indoor cooling mechanism capable of inhibiting solar gains into the building, with a focus on the performance roles and composition of windows in particular.

Intelligent optical management for energy-efficient windows driven by mechano-thermochromism

The thermochromic windows based on vanadium dioxide (VO2) can intelligently modulate the transmittance of indoor solar radiation, which is significant for reducing building energy consumption. However, conventional thermochromic windows only have the ability of single spectral modulation, continuously switching the solar spectral transmittance in response to varying ambient temperature on a window is challenging. In this work, a SiO2-VO2-PDMS-driven by mechano-thermochromism intelligent optical management system was proposed for automatic switching and continuous adjustment of the solar spectral transmittance. Compared with the single-layer VO2 film, the SiO2-VO2 double-layer thermochromic window provides a gradual refractive index change from the top with nair = 1 to the middle with around 1.5, and then to the bottom with a higher refractive index, which suppresses reflections over a wider wavelength range. The results show that the SiO2-VO2 double-layer coating with a refractive index buffer layer exhibits improved optical performance with a solar modulation ability (ΔTsol) of 18.4% and an average luminous transmittance (Tlum,avg) of 49.1%. Furthermore, the design can achieve increases in the stretch-related solar modulation ability (ΔTsol,stretch) and the stretch-related luminous transmittance (Tlum,stretch) from 18.4% to 43.8% and 49.1% to 60.5%, respectively, which is realized by the deformation of polydimethylsiloxane (PDMS). Combining elastic stretching with thermochromic windows can dynamically modulate the solar spectral transmittance to improve thermal comfort. This work provides a promising approach to improve the industrial application of VO2 thermochromic windows, contributing to the advancement of research in green buildings, window design, and automotive energy efficiency.

Dynamics of shaded areas in a typical-shaped solar greenhouse and their effects on tomato growth—A case study in winter

The side walls and fixed insulation quilt of a solar greenhouse helped reduce heat loss from the room at night but produced shadows on the greenhouse floor during the day, affecting the growth and development of crops. In the present study, a method to calculate the projected area of the side walls and fixed insulation quilt in the greenhouse was derived. Then, a typical-shaped solar greenhouse and tomatoes were used as experimental research objects to investigate the spatial and temporal variation of indoor solar radiation intensity and tomato growth. The results showed that: 1) The average absolute error between the calculated and measured values of the ground shade of the solar greenhouse on four typical sunny days was 1.12%, 2.65%, and 2.02%, respectively. The area of selected greenhouse was 450m2, the maximum shaded area could account for 20.3% of the total area of the greenhouse, the shaded area projected by the insulation onto the greenhouse floor remained constant at different times, and that projected by the wall decreased and then increased parabolically with time. 2) The average solar radiation intensity in the greenhouse at the winter solstice tended to increase and then decrease with time, with a maximum value of 41,374.0 Lux. The uniformity of solar radiation distribution was reduced in the morning, evening and midday hours. 3) The tomato plant height, stem diameter, leaf area index and yield were 36.9%, 14.7%, 63.1% and 125.4% higher, respectively, in the high than in the low solar radiation zone. The results of the study can provide a theoretical basis for clarifying the dynamics of shaded areas and the spatial and temporal distribution of solar radiation intensity in greenhouses, and for optimizing the structural parameters of solar greenhouses.

Self-Powered Dynamic Glazing Based on Nematic Liquid Crystals and Organic Photovoltaic Layers for Smart Window Applications

Dynamic windows allow monitoring of in-door solar radiation and thus improve user comfort and energy efficiency in buildings and vehicles. Existing technologies are, however, hampered by limitations in switching speed, energy efficiency, user control, or production costs. Here, we introduce a new concept for self-powered switchable glazing that combines a nematic liquid crystal, as an electro-optic active layer, with an organic photovoltaic material. The latter aligns the liquid crystal molecules and generates, under illumination, an electric field that changes the molecular orientation and thereby the device transmittance in the visible and near-infrared region. Small-area devices can be switched from clear to dark in hundreds of milliseconds without an external power supply. The drop in transmittance can be adjusted using a variable resistor and is shown to be reversible and stable for more than 5 h. First solution-processed large-area (15 cm2) devices are presented, and prospects for smart window applications are discussed.

Investigation based on physiological parameters of human thermal sensation and comfort zone on indoor solar radiation conditions in summer

Indoor solar radiation significantly affects human thermal sensation, especially with the extensive use of glass structures in modern buildings. This study explored the varying characteristics of human physiological and psychological responses to indoor solar radiation in the summer, based on a laboratory experiment involving 20 participants and six cases comprising different intensity levels and irradiation areas. In this experiment, the thermal sensation and acceptability were recorded, and environmental and physiological parameters such as local skin temperature, arterial oxygen saturation (SpO2) and pulse rate (PR) were continuously monitored. The results revealed that human physiological regulation is generally delayed, as compared with the psychological changes in unstable environments. This paper proposes a method for calculating the mean skin temperature, representing the skin temperature on the irradiated side by that on the nonirradiated side. The skin temperature calculated using this method reflected the strongest correlation with thermal sensation; this helped reduce the prediction errors in thermal sensation due to psychological factors, when considering skin temperature as a predictor. Furthermore, this study used the standard effective temperature (SET) to calculate acceptable temperature ranges and a neutral SET. It was found that the neutral SET exceeded the general indoor environment by approximately 1 °C; the upper limit of acceptable temperature was 1.77 °C higher than that recommended in ISO 7730, indicating humans' enhanced acceptance ability to air temperatures under indoor solar radiation. Notably, the results of this study constitute a significant theoretical basis for improving thermal comfort under indoor solar radiation in the summer.

A novel solar-based human-centered framework to evaluate comfort-energy performance of thermochromic smart windows with advanced optical regulation

Thermochromic windows provide a promising and practical solution to lower building air conditioning energy via automatically reducing window-through solar radiation which imposes large cooling loads on air conditioning systems. The conventional framework for evaluating thermochromic windows assumes that the solar radiation passing through smart windows is immediately absorbed by indoor air, which ignores the deviated occupant comfort by indoor solar radiation and leads to a biased comfort-energy performance of thermochromic windows. This study proposes a novel solar-based human-centered framework to evaluate the comfort-energy performance of hydrogel thermochromic smart windows (HTSWs) via integrating human-solar modelling, solar-based indoor set-point correction, and building simulations. The comfort-energy performance of HTSWs are evaluated with different warm climates and compared to that of normal windows. The main results indicate that, the conventional framework, which ignores solar radiation on indoor human bodies, underestimates the discomfort time duration of indoor occupants by 55.0% and 75.2% when evaluating normal windows and HTSWs, respectively. Under the human-centered framework, with solar-based set-point correction, indoor occupants with HTSWs regulating solar radiation will be comfortable during more than 95% of working hours; and HTSWs reduce nearly 50% of the discomfort hours compared to normal windows. In addition, the average energy saving potential of HTSWs under the human-centered framework is extended by 35.0% compared to that under the conventional framework. To be specific, the air conditioning energy savings of HTSWs under the conventional framework are 9.9%–20.3% (average 14.5%); under the human-centered framework, the energy savings are 13.5%–25.6% (average 19.5%, which is 35% higher than that under the conventional framework). The considerably improved comfort-energy performance of HTSWs under the human-centered framework will further contribute to the wide adoption of HTSWs.

Performance of Solar Control Films on Building Glazing: A Literature Review

Buildings with a high window-to-wall ratio tend to suffer from excessive solar gains/losses that usually result in high energy demand and discomfort for occupants. Solar control films (SCFs) are a passive solution with the potential to increase the performance of new or refurbished glazing they are applied to. This paper presents a comprehensive literature review of the performance of SCFs applied to glazing systems of buildings. Research studies with experimental, analytical and computer simulation approaches were gathered and analyzed, identifying glass and film systems, climatic conditions, energy savings and comfort performance. The research approaches and main findings of existing research studies were compared and discussed. The presence of SCFs significantly reduced indoor solar radiation and illuminance levels, particularly with reflective films applied to south-oriented glazing (northern hemisphere). Glazing systems with SCFs were reported to promote cooling energy savings compared with clear glazing in hot climates. Few studies have explored the visual and thermal comfort performance of SCFs, concluding that these films promote thermal comfort, and reduce excessive illuminance and potential glare. Furthermore, this paper helps to highlight areas of guidance for future studies on the topic.

Feasibility analysis of energy-saving potential of the underground ice rink using spectrum splitting sunshade technology

The original intention of skylights for underground ice rinks is to introduce natural light, but incoming solar radiation also affects the ice quality and ice-making energy consumption. As public sports and fitness venues of “Ice Cube”, sustainable operation of the underground ice rink with transparent skylights, has attracted much attention of architectural designers. To reduce the energy consumption without affecting indoor natural lighting, the heat transfer process of a skylight is discussed and modeled, and an advanced sunshade technology using Antimony Tin Oxide (ATO) nanofluids is proposed to filter UV/NIR and reserve visible light for indoor natural lighting. Meanwhile, two factors’ effects, including outdoor solar irradiation and mass fraction of ATO nanofluids on the energy-saving potential of an underground ice rink, are discussed, and results indicate that spectral energy of UV and NIR decreases by 23.16% and 32.99% respectively, with 20 ppm ATO nanofluids, but the energy during visible light region only reduces by 11.56%. Additionally, a high mass fraction lowers indoor solar radiation but also lifts artificial lighting energy consumption, and the mass fraction of 200 ppm is recommended as the optimal mass fraction with annual total energy consumption of 392 GJ.

Application of New Energy Thermochromic Composite Thermosensitive Materials of Smart Windows in Recent Years.

Thermochromic smart windows technology can intelligently regulate indoor solar radiation by changing indoor light transmittance in response to thermal stimulation, thus reducing energy consumption of the building. In recent years, with the development of new energy-saving materials and the combination with practical technology, energy-saving smart windows technology has received more and more attention from scientific research. Based on the summary of thermochromic smart windows by Yi Long research groups, this review described the applications of thermal responsive organic materials in smart windows, including poly(N-isopropylacrylamide) (PNIPAm) hydrogels, hydroxypropyl cellulose (HPC) hydrogels, ionic liquids and liquid crystals. Besides, the mechanism of various organic materials and the properties of functional materials were also introduced. Finally, opportunities and challenges relating to thermochromic smart windows and prospects for future development are discussed.

Study on the Roof Solar Heating Storage System of Traditional Residences in Southern Shaanxi, China.

Solar energy is a renewable, green, clean, and universal resource that has great potential in rural areas. Combining solar heating technology with building design to increase indoor thermal comfort in winter is an effective energy-saving and environmentally friendly approach. The factors affecting solar building heating mainly include two aspects; one is the lighting area of the building, and the other is the storage of building materials. By increasing the lighting area and using materials with good heat preservation and storage performance, the indoor temperature in winter can be effectively increased, and the heating time can be prolonged, thus decreasing the energy requirements of the building. In this paper, traditional houses in cold winter areas are selected as the research object, and a roof solar heating storage system is proposed. The method is to transform the opaque roof of the traditional houses into a transparent glass roof, and the thermal insulation and heat storage material HDPE is installed in the attic floorboards. The working principle of this system is to increase the amount of indoor solar radiation to raise the indoor temperature and make use of the thermal insulation performance of heat storage materials to prolong the indoor heating time. Through ANSYS software simulation, the heat transfer process, heat transfer mode, and temperature change of the system are analyzed, and the energy saving of the system is analyzed. The system can effectively raise the indoor temperature and has good energy-saving performance. The indoor temperature is raised by 5.8 °C, and the annual heat load of the building is reduced by 1361.92 kW·h, with a reduction rate of 25.02%.

MgF2 as abundant and environmentally friendly electrolytes for high performance electrochromic devices

Electrochromic devices (ECDs) can regulate the indoor solar radiation by adjusting optical transmissive properties, showing great commercial potential and important social value of green energy saving. However, the unsafety and high cost of Li+ based electrolyte hinder the large-scale and industrialized production of ECDs. Other metal ions have been used as electrolyte ions, but they are rarely reported in all solid state ECDs. In this study, MgF2 film is used as the solid electrolyte to construct all solid state ECD with the structure of glass/ITO/WO3/MgF2/NiO/ITO. The ECD shows the large optical modulation (∼83% at 820 nm, with 100 s durations) and fast response (19.2 s for bleaching and 8.3 s for coloring, with 25 s durations). Moreover, the ECD achieves the extreme transmittance value of colored states Tc ≈ 0%, which can give an absolute private state. This work not only indicates that MgF2 film can be an alternative to Li+ based electrolyte in all solid state ECDs, but also broadens the applications of all solid state EC smart windows to private buildings.

Heat exchange character and thermal comfort of young people in the building with solar radiation in winter

Indoor solar radiation notably affects the thermal environment and the character of human heat exchange with the ambient environment. Based on the field experiments of human body thermal comfort under indoor solar radiation in winter, this paper analyzes heat exchanges between the human body and the surrounding environment and the local and overall skin temperature, and discusses the relationship between heat exchange and thermal sensation. The results show that the skin temperature of the left upper arm and left thigh under radiation is 3.3 °C and 2.0 °C higher than that without radiation. As the irradiated area increases, convection and evaporation heat loss increase, and total heat loss decreases. When the thermal sensation of the human body is in a neutral state, the proportions of heat loss by convection, radiation and evaporation are 33.9%, 47.1% and 10.4%, respectively.

Thermal and electrical performances of semi-transparent photovoltaic glazing integrated with translucent vacuum insulation panel and vacuum glazing

The development of smart windows must provide low solar heat gain with a low overall heat transfer coefficient, avoid humidity and condensation in cold regions, generate clean electricity, and admit comfortable levels of daylight. Therefore, methods for integrating semi-transparent (or 50.8% transparent) CdTe solar cell strings-based glazing with structured-cored mesh translucent vacuum insulationpanels and indium sealed vacuum glazing are described for modernizing smart windows. This study reports experimental and theoretical studies on the thermal and electrical performances of six different glazing systems. These systems include semi-transparent photovoltaic glazing (GPV), vacuum glazing (VG), translucent vacuum insulation panel (GVIP), semi-transparent PV with VG (VGPV), and semi-transparent PV with translucent vacuum insulation panel (VIPPV), and their performances will be compared with that seen with single glazing (SG). These glazing systems are designed, constructed, and tested using a hot box calorimeter, and with and without the effects of simulated indoor solar radiation. The center-of-pane U-values, the transient temperature variations of the inner and outer surfaces of the glazing systems, the open circuit voltages, the short circuit currents, the fill factors, and the steady-state temperature contours were determined. For the first time, the moisture condensation pattern is also depicted for these systems and will be of value for applications in harsh, cold regions. A 3D finite-volume heat transfer model is developed and validated with the experimental results, allowing comparison of the thermal performances of these glazing systems under ASTM boundary conditions. The results showed that the VGPV system achieved a lower U-value than did the VIPPV system. The steady-state center-of-pane temperature differences seen with a solar irradiation level of 1000 W·m−2 are 55 °C, 32.5 °C and 5 °C for the VGPV, VIPPV, and GPV systems, respectively. The validated center-of-pane U-values for the VG, VGPV, VIPPV, and GPV systems, each with dimensions of 15 cm × 15 cm, are predicted to be 1.3, 1.2, 1.8, and 6.1 W·m-2K−1, respectively. The results also show that the use of either the VGPV or VG systems eliminates moisture condensation. It is concluded that VGPV and VIPPV generate comparatively less power but provide higher thermal insulation.

Performance-rating-based approach to formulate a new envelope index for commercial buildings in perspective of energy efficiency and thermal comfort

Taiwan's building envelope thermal performance assessment method (ENVLOAD) was implemented in 1995. The lack of regard for thermal comfort in ENVLOAD has caused ENVLOAD certified buildings to have indoor areas that cause thermal discomfort, which leads to an increase in the energy end-use of the building during actual operation stage. This study aims to develop a new building envelop energy performance index by simultaneously analyzing the influence of energy consumption and thermal comfort. Latin hypercube sampling method is adopted to generate various building envelope samples for building energy simulation to construct the evaluation equations. By comparing to each sample’s annual sensible cooling energy against its own baseline case, indices of performance ratings (PR) based on the dry-bulb temperature and the operative temperature control are proposed. Another aim is to establish an algorithm to convert the proposed index to the previous ENVLOAD benchmark so that the new index can be directly applied to the existing building energy conservation regulations. The study found that the standard regression coefficient of the glazing's thermal insulation property rises from 0.11 to 0.20 when the control scheme switches from dry-bulb control to operative temperature control. Suggesting that the thermal performance requirements for the openings of building envelopes are more important for the new index based on thermal comfort, and that designers need to pay more attention to the control of indoor solar radiation heat gain.

Review: smart windows based on photonic crystals

Smart windows control indoor solar radiation by regulating the transmittance of light, which is a promising way to reduce building energy consumption. The advent of photonic crystals (PCs) has accelerated the industrialization of smart windows. The combination of static and dynamic regulation can be realized based on the photon control function of photonic band gaps, which is expected to achieve the ideal effect of light transmission and heat control. This paper reviews recent advances of electrochromic and thermochromic smart windows based on PCs. Firstly, theory, materials, performance and development of electrochromic and thermochromic smart windows based on PCs are briefly outlined. Typical structures of electrochromic and thermochromic PCs are introduced in detail, from preparation process, morphology characterization and performance analysis, which provides directions for the future development and construction of smart windows based on PCs. Finally, challenges and opportunities facing next-generation smart windows are summarized.