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Lead-free double perovskite halides are emerging optoelectronic materials that are alternatives to lead-based perovskite halides. Recently, single-crystalline double perovskite halides were synthesized, and their intriguing functional properties were demonstrated. Despite such pioneering works, lead-free double perovskite halides with better crystallinity are still in demand for applications to novel optoelectronic devices. Here, we realized highly crystalline Cs2AgBiBr6 single crystals with a well-defined atomic ordering on the microscopic scale. We avoided the formation of Ag vacancies and the subsequent secondary Cs3Bi2Br9 by manipulating the initial chemical environments in hydrothermal synthesis. The suppression of Ag vacancies allows us to reduce the trap density in the as-grown crystals and to enhance the carrier mobility further. Our design strategy is applicable for fabricating other lead-free halide materials with high crystallinity.

Accurate measurement of air flow rate is essential in automatic building control using the variable air volume (VAV) system. In order to solve the problems of the existing air flow measurement method and improve the accuracy of air flow control, this study developed a data-based multiple regression air flow prediction model. The independent variables used in the development of the predictive model were selected as the factors used for control and monitoring when operating with variable air flow rate in the existing air conditioning system. Data collection and correlation between independent variables and air flow rate of the terminal unit were analyzed. Using the IBM SPSS statistics version 25, an air flow rate prediction model was developed using multiple regression analysis. Reliability of model was evaluated by comparing the measured airflow. The relative error of −9.3% to 10.4% is shown when comparing the estimated air flow rate by the developed model with the measured air flow rate.

Mean radiant temperature (MRT), which is a crucial factor for thermal comfort, varies within a space. This renders deriving the representative values for radiant heating and cooling control challenging. This study reviewed existing methods for deriving MRT in previous research and addressed their limitations by proposing a method for determining a representative MRT value. The existing methods were categorized as air temperature, single location, and area weighted. Three methods for deriving representative MRT values were proposed, considering the building’s usage, scale, and applicable system installations. The proposed methods were categorized as single-zone averaged, multi-zone averaged, and point-zone MRT. Experiments were conducted by distinguishing cases based on the control of equipment systems during heating and cooling periods. During the cooling season, the single-zone averaged MRT and air temperature differed by up to 4 °C, and the difference between the multi-zone averaged MRT and MRT at a point in the perimeter zone reached up to 7 °C. During the heating season, the single-zone averaged MRT and air temperature differed by up to 2.2 °C. Thus, the results of this study emphasize the importance of applying different methods of deriving representative MRT values depending on the size and usage of the building, and demonstrate that this facilitated more effective heating and cooling control systems.

Accurate analysis of building energy performance necessitates methodologies that can diagnose the thermal performance of a building's envelope. The building envelope contains various uncertainties and poses difficulties in verifying the measurement results, making it crucial to ensure the reliability of the measurement method. This study used dynamic simulations to verify the accuracy and reproducibility of commonly used field measurement methods. The simulation data were applied to the heat flux meter (HFM) and infrared thermography (IRT) methods to calculate the thermal transmittance of the building envelope and confirm their suitability as a field measurement method. According to the accuracy verification results, the HFM and indoor IRT (IRTi) methods, which are less affected by the external environment, evaluated the actual thermal performance of the wall close to the theoretical value with average relative errors of 3.3% and 4.2%, respectively. In the reproducibility evaluation, the HFM method exhibited similar levels of deviation over time. Additionally, to reduce the deviation in the reproducibility of the thermal transmittance derived from the IRT method, the average method was applied for data analysis, leading to a decrease in the reproducibility deviation from 36.5% to 13.3% for IRTi and from 107.3% to 71.8% for IRT outdoors (IRTo).

In high-rise buildings, the excessive pressure differences cause various problems, and architectural and mechanical measures are always applied. In this study, pressure measurements on a 67-story high-rise building were conducted to evaluate the effect of mechanical pressurization on the pressure distribution. Absolute pressure measurement devices were installed at 28 points on 10 floors, a full-scale pressure profile of the test building was derived, and the pressure distributions on the main floors were reviewed. Four pressurization modes for the test building were considered, and the variation in the pressure distribution for each mode was analyzed. The results showed that mechanical pressurization reduced the pressure difference on the lobby floor by approximately 18%. Although it did not exert an apparent impact on the pressure difference due to the stack effect, pressurizing the entire floor serves as the most effective way of reducing the excessive pressure difference.

Airflow in a multi-zone building can be a major cause of pollutant transfer, excessive energy consumption, and occupants discomfort. The key to monitoring airflows and mitigating related problems is to obtain a comprehensive understanding of pressure relationships within the buildings. This study proposes a visualization method for representing pressure distribution within a multi-zone building by using a novel pressure-sensing system. The system consists of a Master device and a couple of Slave devices that are connected with each other by a wireless sensor network. A 4-story office building and a 49-story residential building were installed with the system to detect pressure variations. The spatial and numerical mapping relationships of each zone were further determined through grid-forming and coordinate-establishing processes for the building floor plan. Lastly, 2D and 3D visualized pressure mappings of each floor were generated, illustrating the pressure difference and spatial relationship between adjacent zones. It is expected that the pressure mappings derived from this study will allow building operators to intuitively perceive the pressure variations and the spatial layouts of the zones. These mappings also make it possible for operators to diagnose the differences in pressure conditions between adjacent zones and plan a control scheme for the HVAC system more efficiently.

The mean radiant temperature (MRT) is an indicator for evaluating the radiant heat environment near occupants and is determined by the radiant heat exchange between the occupants and their surroundings. To control various heating and cooling systems according to the occupants’ thermal comfort, it is essential to consider MRTs in the real-time evaluation of thermal environment. This study proposes a pan–tilt infrared (IR) scanning method to estimate the MRTs at multiple occupant locations in real buildings. The angle factor was calculated by defining the specific classification criteria for dividing the entire indoor surface into sub-surfaces. The coupling IR camera and pan–tilt motor were applied to enable storing data pairs of IR thermal image frame (IR image frame) and pan–tilt angle so each surface area taken by the IR camera can have its direction information. The measurement method of the mean surface temperature using the pan–tilt IR system was presented. The pan–tilt IR system hardware and MRT monitoring software were developed. An experiment was performed to verify the applicability of the proposed pan–tilt IR scanning method. By comparing the surface temperatures measured using a contact thermometer and the proposed IR system, the contact thermometer could cause inaccurate measurement of surfaces with a non-uniform distribution of temperature. The difference between surface temperatures increased by up to 15 °C and, accordingly, the MRT distributions differed by up to 6 °C within the same space. The proposed IR scanning method showed good applicability in various aspects. This paper reports that the MRT has a significant effect on the occupants’ thermal comfort and also suggests considering MRTs in the real-time evaluation of thermal environment to control various heating and cooling systems appropriately.

Exterior dynamic shading devices, installed on "kinetic façades", generate shaded areas of various shapes on windows according to the shape of the shading elements and the direction of their movement. The calculation of the shaded area is vitally important because it is directly related to the solar heat gain calculation process in building energy assessments. This paper dis-cusses a dynamic calculation method for deriving shaded fractions in consideration of the irregular shapes and unique movements of the shading elements in kinetic façades. The planar-polygon method was adopted for calculating accurate shaded areas on a window generated by irregularly shaped shade elements. To account for movements of the shading elements, the range of movement directions (i.e., rotating, sliding, etc.) was divided into b steps of equivalent intervals. Applying these two methods, a shaded area calculation tool for the kinetic façade was developed. Three movement directions of shading devices were chosen for calculating shaded area, and the values of shaded fractions for six kinetic façade types were derived for different façade orientations during the summer and winter solstices. Lastly, to simplify the detailed calculation method, estimation equations for two types of kinetic façade were derived from a trend analysis of the shaded fraction values. This study deals with both detailed and simplified methods (estimation equation) for deriving the shaded fraction. The detailed method can be a more accurate solution in deriving the shaded fractions generated by complex exterior movable shading devices. However, the simplified method can be adopted in the early design stages to review various shading devices within a brief duration of time. [ABSTRACT FROM AUTHOR]

The construction industry has made considerable energy-saving efforts in buildings, and studies of energy-savings are ongoing. Shading is used to control the solar radiation transferred through windows. Many studies have examined the position and type of shading in different countries, but few have investigated the effects of shading installation in Korea. In this study, the case of the shading installation according to the standard of Korea, and variations of the heating and cooling load in the unit area on the performance of the windows were examined. This study compared the variations of the heating and cooling load in the case of horizontal shading and the changing position of venetian blinds. This study confirmed that horizontal shading longer than the standard length in Korea saved a maximum of 13% energy consumption. This study confirmed the point of change of energy consumption by the Solar Heat Gain Coefficient (SHGC) variations. The exterior venetian blinds and those between glazing were unaffected by the SHGC. On the other hand, in the case of a south façade, the interior venetian blinds resulted in 24% higher energy consumption than the installation of horizontal shading in case of Window to Wall Ratio (WWR): 80%, U-value: 2.1 and SHGC: 0.4. [ABSTRACT FROM AUTHOR]

The energy performance of buildings depends on how effectively the building envelope responds to climate. Architects, therefore, need to design building envelopes with the consideration of local climate characteristics in the early design stage. Simplified formulas were used that evaluate the heating and cooling energy demand of building envelopes, which were applied to a model building with envelope and climate properties according to eight climate zones. Two climate indices, P and S, were developed. P enables the comparison of the heating and cooling energy demand of building envelopes, and S is for comparing the solar heat gain during heating and cooling seasons to review the feasibility of installing shading devices. The physical properties of envelopes were set differently according to the requirements in each climate zone proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 90.1. Using local climate data, the P and S of 24 cities over eight climate zones in the United States were derived, which can be used to evaluate the heating and cooling energy characteristics of envelopes. The indices not only enable users to understand the characteristics of the local climate conditions in a simple manner, but also to carry out quantitative assessments on whether shading devices are feasible and, if so, what type is recommended. [ABSTRACT FROM AUTHOR]

In this study, a model equation is derived that uses a statistical analysis based on empirical models to predict the airtightness of reinforced concrete apartment buildings popular in Asian regions. Airtightness data from 486 units personally measured by the authors in the past eight years are used. As major variables used in the prediction model, two groups of variables are configured for the geometric components of the envelope, which is a major path of airflow in a building and is where air infiltration and leakage occur. The two groups of variables represent (1) the areas of the individual components forming the envelope and (2) the connection lengths between different components of the envelope. For the effective prediction of airtightness, correlation analysis and multiple regression analysis were applied step by step in this study. The results of the correlation analysis indicated that the areas of the slab and the window are the area variables that present the greatest impact, whereas the perimeter length of the window is the connection length variable that presents the greatest impact. Using a multiple linear regression analysis method, airtightness prediction model equations can be derived, and it is found that the model with variables for area is able to predict airtightness more accurately compared to the two models derived from variables for connection length and all variables for area and connection length. Although the statistical approach in this study shows a limitation in that the prediction results may vary depending on the attributes and type of data collected by countries, the methodology and procedure in this study contribute to similar studies for making prediction models and finding the influence of variables in the future with high applicability and feasibility.

Achieving energy efficiency by improving the operating method of the system used in existing buildings is attracting considerable attention. The Building Design Criteria for Energy Saving was established to induce energy saving design in the domestic construction field, and the introduction of a free-cooling system, such as an economizer system, as an item of the mechanical sector, was evaluated. The economizer is an energy saving method that reduces the building load by introducing outdoor air through damper control according to the indoor and outdoor conditions. The system consists of dry-bulb temperature control and enthalpy control and the mixed air temperature is kept constant in the conventional economizer controls. On the other hand, in dry-bulb temperature control, when the set value of the mixed air temperature is changed according to the load, additional energy savings are expected compared to the conventional control method. Therefore, this paper proposes an economizer control that makes the mixed air temperature variable according to the load in a Constant Air Volume single duct system. For this, a load prediction is needed and an Artificial Neural Network is used for the load prediction. In addition, the relationship between the mixed air temperature and energy were analyzed using the BIN method and TRNSYS 17. Based on the results of previous analysis, a control method which predicting the load using Artificial Neural Network and controlling the mixed air temperature according to the predicted load in the dry-bulb temperature control of a Constant Air Volume single duct system is proposed and the proposed control was applied to the dynamic simulation program and compared with the conventional control. The results show that the temperature of each room was 21–23 °C in summer and 22.5–26 °C in winter when the economizer was controlled using the proposed control method and the energy consumption analysis showed that 19% of the energy was reduced compared to the conventional method when the proposed method was controlled.

Since the thermal environment of large space buildings such as stadiums can vary depending on the location of the stands, it is important to divide them into different zones and evaluate their thermal environment separately. The thermal environment can be evaluated using physical values measured with the sensors, but the occupant density of the stadium stands is high, which limits the locations available to install the sensors. As a method to resolve the limitations of installing the sensors, we propose a method to predict the thermal environment of each zone in a large space. We set six key thermal factors affecting the thermal environment in a large space to be predicted factors (indoor air temperature, mean radiant temperature, and clothing) and the fixed factors (air velocity, metabolic rate, and relative humidity). Using artificial neural network (ANN) models and the outdoor air temperature and the surface temperature of the interior walls around the stands as input data, we developed a method to predict the three thermal factors. Learning and verification datasets were established using STAR CCM+ (2016.10, Siemens PLM software, Plano, TX, USA). An analysis of each model’s prediction results showed that the prediction accuracy increased with the number of learning data points. The thermal environment evaluation process developed in this study can be used to control heating, ventilation, and air conditioning (HVAC) facilities in each zone in a large space building with sufficient learning by ANN models at the building testing or the evaluation stage.

The Korean government is fostering a renewable energy industry as a means of handling the energy crisis. Among the renewable energy systems available, geothermal energy has been highlighted as highly efficient, safely operable and relatively unaffected by outdoors air conditions. Despite the increasing use of renewable energy, the devices using renewables may not be operating appropriately. This study examined current problems in the operation of a geothermal heat pump (GHP) system. The efficiency of a geothermal heat pump system to studied to maximize the operation plan. Our study modelled the target building and analyzed the energy using TRNSYS, which is a dynamic energy simulation tool, to apply the coefficient of performance (COP) and evaluate the operation method. As a result, the GHP total energy consumption from the COP control method was reduced by 46% compared to the current operation. The proposed control method was evaluated after applying the system to a building. The results showed that efficient operation of a geothermal heat pump system is possible.