bluuebunny/crossref_metadata_2025 huggingface dataset:
Mobile sensing based indoor thermal field reconstruction: Test in a virtual environment
Authors: Zhou Qi , Wang Zhe
Published: June 2023

Environmental monitoring is a prerequisite to evaluate, control, and optimize indoor environmental quality. Compared to stationary sensing that deploys sensors at fixed locations, mobile sensing using an automated moving robot can actively take measurements at locations of interests, which provides a more flexible and efficient way to achieve a high-granularity agile environmental monitoring. Studies have been conducted to design and implement mobile sensing algorithms, however, to deploy on hardware and test the algorithm in the real world is usually expensive and challenging. In this study, we introduced a virtual testbed, AlphaMobileSensing which can be used to test, evaluate, and benchmark mobile sensing algorithms easily and efficiently. Using the virtual testbed, we conducted a test on a spatio-temporal (ST) interpolation algorithm for its robustness in indoor thermal field reconstruction. Two factors, the moving path, and the initial position, were considered, and the corresponding field reconstruction results were compared. The results show that the ST interpolation algorithm can extract similar global trend of a dynamic field regardless of different moving paths and initial locations, however, predictions of field local variations are sensitive to these two factors.
Effect of distance between occupants and insulation performance of window on contaminant distribution in a room with displacement ventilation
Authors: Ishikawa Shinnosuke , Yamanaka Toshio , Kobayashi Tomohiro , Choi Narae , Essa Aya , Komori Miharu
Published: June 2023

In recent years, displacement ventilation system has received much attention in terms of infectious disease control, due to the epidemic of COVID-19 infections. Plume from occupants and the other heat sources is a very important factor for displacement ventilation because it determines the height of the contaminant stratification. Therefore, this paper aims at the effect of distance between occupants on distribution of temperature, contaminant concentration and plume from occupants in CFD analysis at first. The results suggest the specific distance where plume from occupant interfere with each other in the occupied zone. Our results also indicate that other conditions such as human body posture also affect the interference. In addition, since the aforementioned study don't take into account the influence of the temperature of window surface cooled by outside air, we vary the insulation performance of the window and check the concentration in the occupied area. The results are obtained that the amount of contaminants carried by the downward flow from the window to the lower part of the room depends on the insulation performance of the window, which affects the occupied zone.
Indoor air quality assessment to design a model for indoor air quality management and health impact assessment in Northern Thailand
Authors: Thongsumrit Jitvisut , Chantara Somporn , Naksen Warangkana , Bootdee Susira , Payam Mallika , Wiriya Wan
Published: June 2023

Indoor air quality (IAQ) has become an important area of concern these days and tends to be more serious to human health as well as resident convenience, especially in smoke haze season (February - April) in Upper Northern Thailand (UNT). Indoor air monitoring and model development for controlling the air quality indoors is necessary for all buildings, particularly in urban areas and polluted areas. This study aims i) to study indoor air quality, ii) to assess health impacts and factors related to indoor air quality, and iii) to develop an effective model for controlling indoor air quality in Sub-district Health Promoting Hospital (HP) and Early Childhood Development Center (ED). Temperature, relative humidity, air movement, PM2.5, PM10, Carbon Dioxide (CO2), Carbon Monoxide (CO), Ozone (O3), Formaldehyde (CH2O), Total Volatile Organic Compound (TVOC), Total bacterial and fungal were used to evaluate indoor air quality. It was found that PM2.5 and PM10 concentrations in all buildings exceeded indoor air quality standards. Moreover, CO2 concentration was higher than recommended levels, especially during the daytime. HP and ED found high values of total bacteria and total fungi, which were higher than recommended level. The indoor air quality management model of a clean room that involved with the calculation of total airflow in cubic feet per hour was created and a specific size of air cleaner for the room was selected. The results showed that PM2.5 and PM10 concentrations including other parameters of the selected rooms were reduced to the recommended levels after implementing the rooms. This result indicated the effectiveness of developing an indoor air quality management model. Thus, this model can be used as a successful study case for other HP and ED, leading to a positive impact on building occupant health.
Humidification Performance Evaluation of hollow-fiber membrane-based humidifier for air-conditioning
Authors: Jo Su-Young , Cheon Seong-Yong , Kim Beom-Jun , Kwon Taek-Don , Jeong Jae-Weon
Published: June 2023

Indoor viral and fungal activity is affected by the concentration of moisture in the air. Since the concentration of viruses and fungi in the air directly affects the human body, it is necessary to maintain a specific humidity range through the air-conditioning system. The optimum humidity in the building is 40-60%, and it needs to be maintained regardless of the season. In winter, a separate humidification system is required to adjust the indoor humidity due to the dry outside air. However, since the conventional humidification system injects water or steam directly into the air, various problems, such as water pollution, occur. Therefore, this study proposed a new humidification method called the hollow-fiber membrane humidification system to increase indoor humidity, and the effect was experimentally evaluated. When 150 CMH (air volume of ventilation level) was supplied, the absolute humidity increased by about 4.14g/kg compared to the initial condition, and the relative humidity of the indoor supply air increased to about 64%.
Causal inference between indoor dampness and adverse health effects
Authors: Hasegawa Kenichi , Mitamura Teruaki , Kagi Naoki , Sakaguchi Jun , Shiraishi Yasuyuki , Shinohara Naohide
Published: June 2023

Indoor dampness can promote the establishment of microbes in indoor environments, and as such, controlling dampness is important for maintaining a healthy indoor environment. Here, an index is proposed for evaluating indoor dampness based on checking for visible condensation, mold in living rooms and bedrooms, and moldy odors indoors. In this evaluation method, eight items related to visible condensation, presence of mold, and moldy odors are assigned a maximum score of 3 points; the total score (a maximum of 24 points) is then used as an index for the degree of dampness. We classified the total score into four rankings based on quartiles. Rank 4 represents the lowest rank and was assigned to houses that had the most severe levels of indoor dampness. We hypothesized that the lower the rank, the higher the incidence of sick housing syndrome (SHS) would be among young children. To clarify whether there was an association between child SHS and indoor dampness, we conducted an Internet-based cross-sectional survey on children aged 4–12 years. This study first identified potential confounding variables for exposure to indoor dampness using a directed acyclic graph. The results indicated that the higher the degree of dampness, the higher the health risk was for ocular, nasal, and throat symptoms. Dose-response relationships between indoor dampness and SHS were presented using the dampness index proposed in this study.
Holistic analysis of indoor environmental quality in refurbished school using HAIEQ methodology - Czech case study
Authors: Kabele Karel , Dvořáková Pavla , Veverková Zuzana
Published: June 2023

The subject of this paper is a detailed analysis and evaluation - audit of the quality of the indoor environment in the reference zone of a primary school building in the Czech Republic. The analysis and subsequent evaluation is performed by the certified CTU HAIEQ (Holistic Assesment of Indoor Environmental Quality) methodology, developed at the Department of Building and Construction Engineering of the Czech Technical University in Prague. The analysis is based on a detailed survey of the building, measured data of physical variables of the indoor environment and subjective assessment from the user's point of view. The evaluation of the quality of the environment is carried out in 8 categories - LS Location and location of the building in terms of external environment and social connections; STI Structural-technical design and interior of the evaluated zone; TCW Thermal comfort in cold season; TCS Thermal comfort in warm season; IAQ Air quality; LC Light environment; AC Acoustic environment and EC Electro-magnetic, -ionic -static fields. Each category has 5-8 criteria to be evaluated. The outcome of the indoor environment audit using the HAIEQ methodology is the identification of critical areas and the proposal of possible measures to improve the current situation. The implementation of the proposed measures must be carried out in accordance with applicable regulations and laws by authorized persons. The method used does not guarantee that all problem areas will be found using it and the preparer is not responsible for problems not found during the analysis of the building. The results of the measurement and evaluation methodology are not a substitute for an assessment by a sanitary service.
Effects of General and Task Lighting on Subjective Perception and Work Performance: Empirical Study in an Office
Authors: Zeng Yunyi , Zhou Jiayi , Yu Juan , Lin Borong
Published: June 2023

Lighting accounts for a large proportion of building energy use. Task lighting is effective in saving lighting energy consumption and found to improve productivity in factories, but its effects in offices remain unknown. This study aims to investigate the effects of general and task lighting on office occupants’ satisfaction, alertness, mood, and performance in simple and complex tests. A within-subject design involving 2 lighting condition (100% general lighting vs. 70% general + 30% task lighting) × 2 task type (paper-based vs. computer tasks) was adopted. The work-plane illuminance and the equivalent melanopic illuminance were controlled at the same level in two lighting conditions. The lighting power was reduced by 16.7% when introducing task lighting. 28 subjects participated in this empirical study. The results showed that different lighting conditions had no significant impact on alertness. Introducing task lighting would suppress positive mood, but improve work performance. The respond speed in simple tasks was significantly improved by 4.3%-8.5% and the correct rates in complex assessments increased by 6.2%. These findings highlight that the combination of general and task lighting reduces power consumption and benefits work performance. However, its suppression on the positive mood also needs to be considered in the lighting design.
The approach to adjusting commercial PM2.5 sensors with a filter-based gravimetric method
Authors: Wang Wan-Ru , Chen Hsiu-Ling , Su Huey-Jen
Published: June 2023

The measurements of temporal change to indoor contaminant concentrations are critical to understanding pollution characteristics. As commercial sensors are becoming increasingly commonplace, concentration accuracy is still a critical issue. The most common methods for measuring indoor particulate pollutants based on filter-based gravimetric methods. However, the gravimetric method is expensive, time-consuming, and often provides little temporal information. More and more commercial sensors are utilized to collect larger and temporal information about indoor air pollutants. Nevertheless, limited data support the accuracy of commercial sensors so far. Thus, this study aims to evaluate the performance of commercial sensors. PM2.5 were collected for 30 days by personal environmental monitors with an airflow of 2 L/min on 37-mm Teflon filters and commercial sensors, simultaneously in a three-story house. Moreover, the intra-sensor comparison was conducted for 24 hours by the resolution in 1 minute. Finally, the linear regression model was built to adjust commercial sensors. The intra-sensor comparison results revealed that 24 hours average coefficient of variation (CV value) of PM2.5 in this study were under 10% and the R2 of the adjusted equation was 0.9394. We provide an accurate concentration of commercial sensors to estimate the association between pollutants exposure and health.
Field Survey of Indoor Microplastic in Four Regions of Japan
Authors: Lim Eunsu , Bai Yifan , Ni Yuan , Takeuchi Jinya , Ogasawra Takeshi , Takemura Akihisa , Kim Hoon , Ito Kazuhide
Published: June 2023

In recent years, the plastics pollution of 5mm or less size (microplastics) in marine ecosystems has been a global issue. The presence of microplastics (microfibers) is also a major concern in indoor environments of the residetial house. Many sources of microplastics in the marine environment also exist in the indoor environment. In the modern age where we spend most of our time indoors, the indoor environment is related to the health of residents, so it is important to investigate the presence and contamination status of microplastics in the indoor environment. There is limited the number of studies on microplastics in the indoor environment. In our previous studies have confirmed the presence of microplastics in indoor environments Kanto area including Tokyo of Japanese residential houses. The purpose of this study is to investigate the concentration of indoor microplastics in four regions; Kanto area including Tokyo, Chubu area, Tohoku area, and Kansai area. We focused on the indoor microplastics in settled dust on the floor of residential houses, and the survey was conducted on the 16 residential houses. Micro-Fourier transform infrared (µ-FT-IR) spectrophotometry was used for the qualitative analysis of microplastics. The detected components in the settled dust were cellulose, polyamide (PA), polyacrylamide (PAM), polyacrylonitrile (PAN), polybutylene terephthalate (PBT), polyethylene (PEs), polyester (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl acetate (PVAL).
Effect of Outdoor Temperature on Performance of All-air Wall Induction Unit in a Four-bed Hospital Ward
Authors: Sheng Shaoyu , Yamanaka Toshio , Kobayashi Tomohiro , Choi Narae , Chou Nobukazu
Published: June 2023

The prototype all-air wall induction unit (IU) has the characteristics of displacement ventilation (DV) and windless air supply, which is considered ideal for hospital ward usage. The outdoor temperature, however, will affect its ventilation and thermal performance. This study conducted a full-scale experiment. IUs are vertically installed in the four corners of the experiment room, which is furnished as a Japanese hospital ward. An outdoor climate simulation chamber (OCSC) is installed on one side of the room to simulate the external window and sill under different outdoor temperature conditions. CO2 is generated from the room’s one point, representing pollutants emitted by a patient. The room’s steady-state temperature and CO2 concentration distribution are analyzed under different outdoor temperatures (in OCSC) and air supply conditions. The IU maintained a comfortable thermal environment under all experimental conditions. In terms of ventilation performance, downward airflow undermines concentration stratification in midwinter. The DV stabilizes when the temperature difference between inside and outside air becomes less than 10 °C while using the double-pane window in winter. Conversely, upward airflow strengthens the DV in the summer. In addition, a sufficient supply rate is recommended to keep concentrations and temperatures above the patients’ breathing zone.
A simple neural network for predicting operable window status
Authors: Srisamranrungruang Thanyalak , Hiyama Kyosuke
Published: June 2023

A simple artificial neural network (ANN) is globally developed and broadly adopted in the building engineering field from many perspectives. It is a powerful tool to help engineer or predict future statements. There are many methods to introduce natural ventilation interior, and the simplest way is to conduct the airflow through windows. The general passive ventilation is practically in Spring and Autumn. This study aims to forecast the trends of indoor temperature and schedule the operation status of operable windows by using time-series differential data set. The building simulation has conducted during the transition periods to create training and testing data. A single-layer artificial neural network has been developed and performs training using the Levenberg-Marquardt algorithm. Additionally, the simulations have investigated in different seasons and places to validate the ANN model and find the best ANN model. From the result, the best trained ANN model is the training data that created covers the spring and autumn seasons with one hidden layer and 25 nodes. The training performances present in terms of MSE and R-values are 0.0507 and 88.25%, respectively. Finally, the best ANN model that has been built from a location is applicable and adapted to another location efficiently.
Study on reproducibility of exhaust diffusion properties of gas water heaters in apartment complexes
Authors: Hayakawa Atsunori , Kurabuchi Takashi , Kim Jeongil
Published: June 2023

Gas water heaters in Japan are generally in shared corridors. However, there are restrictions on the installation location and the shape of the corridor to avoid the stagnation of exhaust gas in the corridor and its flow into the rooms through the external air supply opening. These installation standards limit building planning and require further mitigation. Although experiments using full-scale models have been conducted, it is still difficult to consider all possibilities as the shared corridors can be of many shapes. The relaxation of standards should be studied through simulations using computational fluid dynamics (CFD). First, the target data for reproducing the exhaust properties in the CFD analysis are collected via actual measurement. Subsequently, the exhaust diffusion properties of gas water heaters are reproduced by simulation using CFD analysis based on the measured data. Reproducibility is improved by changing the location of the outlet boundary condition in gas water heaters. Finally, the reproducibility of the exhaust diffusion properties is examined for the gas water heater installed in the shared corridor. Comparing the experimental and simulation results, confirms the reproducibility of the concentrations at the exhaust trajectories and air supply outlets.
Review of modern demand control solutions and technologies for HVAC operation
Authors: Borodinecs Anatolijs , Zemitis Jurgis , Palcikovskis Arturs , Ardavs Arturs , Lavendelis Egons
Published: June 2023

HVAC systems, which use traditional control strategies with fixed ventilation rates or with ventilation rate schedules, do not adjust according to the required IAQ and thermal comfort. As a result, building spaces are being over or under-ventilated. In this paper, the latest modern solutions for demand-controlled HVAC system operation are analyzed, based on the review of existing studies. Such modern technologies as human detection systems, computer vision, and neural network applications are looked at. Different types of human presence detection are presented based on the applied technology. The most common ones are indirect detection based on the usage data of existing IT equipment, and direct detection through the use of passive infrared sensors, wearable tags, and vision sensors. Also, the potential solutions of human activity monitoring, skin temperature, and clothing level detection systems are examined. The studies discussed in this paper show real application examples and prove the benefits of using the technologies for the control of ventilation systems in various building types. Research has shown that such technologies have a favorable effect on both indoor air quality and system energy consumption. In the future, the ventilation system should be equipped with cameras for a more accurate analysis of the room and occupancy. Also, the systems must consider occupant behavior, activity, and other information, which can be used for indoor environment quality improvement. Based on the gained knowledge a sensor capable of human detection, accounting, and location marking is developed.
Potential and limits of Natural Ventilation for comfort in retrofit buildings in tropical climates
Authors: Riou Brieg , Ortego Egoï , Delplanque Valentin , Blanchard Benoit , Gandemer Jacques , Stabat and Pascal
Published: June 2023

The space cooling demand is growing very fast in the world in conjunction with the increase of life standards and the climate change. A major stake for the future in buildings is to provide human comfort and to limit the cooling energy consumption. In this context, natural ventilation turns to be an interesting solution in tropical zones where 40% of the world's population lives. This paper aims to assess the potential and limitations of wind induced crossed natural ventilation for comfort in tropical environments. A method based on correlations from the literature is proposed, integrating all the links in the physical chain of natural ventilation, i.e. from outdoor climatic conditions to indoor comfort. The application of this method is done through a case study in Reunion Island and gives orders of magnitude of comfort time proportion according to different parameters such as the opening surface, the indoor thermal and humid loads and the orientation of the considered building. Finally, the limitations of the method are discussed, as well as the need for research to define design rules to favour natural ventilation for housing and office retrofit.
Building air leakage characteristics and airtightness durability of single-family dwelling
Authors: Toriumi Yoshihiro , Kurabuchi Takashi
Published: June 2023

In this study, we focus on the leakage characteristics and composition of openings associated with building airtightness in wooden single-family dwellings. The proposed parallel combination models for leakage are equal to or better than the power law in terms of compatibility with measured values. Unlike reinforced concrete housing complexes, wooden single-family dwellings indicate variability in terms of the coefficient of leakage characteristics, including in highly airtight units. Dwellings constructed approximately 10 years ago do not exhibit a clear declining trend. However, the airtightness decreases in dwellings that have undergone renovations on the outer walls, such as through the addition of an attic or the installation of additional heat pumps.
Control of Natural Ventilation Opening to Achieve Energy Saving Performance and Thermal Comfort in Office Room
Authors: Niwa Kenryu , Kobayashi Tomohiro , Yamanaka Toshio , Choi Narae
Published: June 2023

In recent years, the number of office buildings that introduce natural ventilation (NV) is being increased to save energy. However, operating NV systems with NV opening device fully open could lower thermal comfort, depending on meteorological condition. Therefore, automatically-controlled NV systems can generally work only for a relatively short period of time. In order to keep both energy saving performance and thermal comfort even when outdoor temperature is low in the mid-seasons, it is necessary to understand the relation between NV conditions and the indoor environment. In this paper, the indoor environment is evaluated changing NV conditions by using CFD for a generalized office room model. Four types of NV inlet system were assumed, i.e., high peri-counter (Type 1), low peri-counter (Type 2), slot-type downward inlet (Type 3), and slot-type horizontal inlet (Type 4). Twenty conditions were analyzed for each type, varying the outdoor air temperature and NV flowrate as parameters. As indices of thermal comfort, average vertical temperature difference within perimeter zone and ADPI in the occupied zone were calculated. For each of NV systems, simplified equations to calculate Nmax from indoor/outdoor temperature difference are finally to be proposed, which may be considered for NV opening control in operating NV systems.
Impact of cultural behaviour on indoor comfort: Examining the air quality in Homes and exploring observational and experimental methods of representation through filmmaking
Authors: BK Satish , Gall Allister , Shahzad Sally
Published: June 2023

There is a limited understanding of householders’ cultural differences and their impact on spatial organisation and energy behaviour in dwellings. Indoor air quality directly impacts the health and well-being of occupants. The airborne COVID-19 epidemic has highlighted shortcomings of controlled ventilation systems in recent reports (PHE, Dec 2020). While efficiency interventions can make homes more affordable to heat, they can exacerbate conditions such as asthma, due to reduced indoor air quality and ventilation. Preliminary research conducted in Plymouth by the applicant indicates that British Asians use their homes differently compared to native British in terms of spatial organisation, cooking habits (on average, they spend five times more time cooking the daily meal) and ventilation strategies, all of which have an impact on indoor air quality. This project sets out to establish the impact of culturally informed choices on indoor air quality and the extent to which the norms that guide the design of energy-efficient homes ignore potentially significant cultural and behavioural differences. It will achieve this by focusing on the impact of energy behaviour and choices related to cooking on the indoor air quality of British-Asian households. The project aims to quantify temperature, humidity and air quality by data collected by a pilot study in Plymouth, UK. We will engage the community in a participatory methodology using correlational research and survey questionnaires and IAQ Data Loggers to evidence anomalies from the design norms currently used in the UK. In addition to traditional data analysis, our methodology includes artistic research, utilising observational and sensory ethnographic filmmaking techniques, to support, document, and evidence the impact of cooking in the home. We aim to explore how the intersection between these two methods can reveal and communicate new perspectives. The main outcome is to evaluate the impact of cultural behaviour on the air quality of super-insulated British-Asian homes through an interdisciplinary methodology. This project lays foundations for larger-scale research working with diverse ethnic minority communities to promote engagement in a low-carbon society.
Impact of Layer Configuration and Chilled Water Temperature on the Cooling Capacity of Thermally Activated Light Shelf (TALS) System
Authors: Park Jong-Ho , Kim Sang-Yeop , Choi Ji-Su , Kim Chul , Rhee Kyu-Nam , Jung Gun-Joo
Published: June 2023

Light shelves provide a function to control direct sunlight and introduce daylight into indoor spaces. Also, chilled water flowing in the light shelf can mitigate local cooling demands in perimeter zones. Therefore, in this study, a thermally activated light shelf (TALS) system was proposed, and the TALS’s radiative cooling capacity was evaluated. To do this, a mock-up chamber was developed using prototypes of TALS systems based on panel configurations. It is included: ‘Insulated’ (INS), ‘Air layer’ (ARL), and ‘Air layer with fans’ (ARF), which were designed to increase thermal insulation, natural convection, and forced convection in the TALS panels, respectively. The experiment showed that the ARL and ARF increased cooling capacity by 29% and 57% compared to the INS. Natural convective heat transfer and fan-forced airflow in the TALS's air cavity contributed to improving cooling capacity. With the INS and ARL, the air temperature was recorded at 28.6°C, which requires additional space cooling. The ARF reduced air temperature up to 2.0°C because the TALS cavity fans expedited convective heat transfer and mixing air between the cavity and test chamber. The results of this study could be used to estimate TALS cooling capacity and propose an optimal design in buildings.
Reducing energy consumption of heat pumps by introducing a thermal energy storage system
Authors: Hashimoto Ryoya , Kindaichi Sayaka , Huang Hongzhang , Nishina Daisaku
Published: June 2023

We proposed a short-term thermal energy storage system by applying Phase Change Materials (PCMs) in air ducts connected to an indoor air conditioning unit within a ceiling space. PCM tubes were arranged in a staggered layout in the air duct and cooled by chilled air from the air conditioning unit during “charging” mode, whereas the PCM tubes released cold energy to the room space without operation of the compressor during “discharging” mode. The charging mode allowed for an increase in the partial load ratio of the heat pump to prevent low-efficiency operation at <20% load, which can increase seasonal energy efficiency. We constructed an energy simulation program, where the heat exchange coefficient between the PCM tubes and air was varied with airflow rate and the temperature difference between the PCM and air, in accordance with results from CFD analysis. Switching between the charging and discharging modes was based on the outlet temperature (Tout) and 30% of the rated capacity of the indoor unit (Lr). The heat balance between the charging and discharging modes was improved by this change to the system control. A higher load factor and higher COP resulted in a 7.6% reduction in energy consumption.
Uncertainty quantification of borehole heat exchanger design length based on a global sensitivity analysis
Authors: Shin Euntak , Kim Yoonseong , Kim Young-sang , Choi Wonjun
Published: June 2023

Ground heat exchangers are essential components of ground-source heat pump systems. One of the most-used ground heat exchanger types is a borehole heat exchanger (BHE). Many parameters, such as the building thermal loads, ground thermal properties, and BHE components, influence the required BHE length. Therefore, understanding how individual parameter uncertainties are propagated to the output is counterintuitive. In this study, a global sensitivity analysis (GSA) was performed using the framework of the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) BHE design method. The GSA was conducted to identify the subparameters behind the input parameters of ASHRAE design method, which indirectly determine the BHE lengths by impacting the direct input parameters in the ASHRAE formula. The results reveal that the zone infiltration, heat pump efficiency, ground temperature, effective borehole thermal resistance, and electric equipment heat gain are the most influential parameters on the BHE design length.
PV Panel Heat Transfer Rate Enhancement Using a Novel Heat Exchanger with High-Resolution Spikes and Dimples
Authors: Kashan Mohammad E. , Fung Alan S. , Swift John , Kumar Rakesh
Published: June 2023

PV cell electrical efficiency has an inverse relationship with its temperature. This study uses a novel and commercialized backsheet to reduce PV panel surface temperature. The novel backsheet consists of spikes and dimples to increase the air turbulence and convection heat transfer rate. Experimentally validated computational fluid dynamic (CFD) models are developed to investigate the influence of GripMetal backsheet on PV cell temperature and efficiency of PV panels and PVT collectors. Under 1000 W/m2 solar irradiation, it is shown that a PVT collector with a 2.25 mm spikes height has almost 10% more electrical efficiency than a PVT collector with a flat plate channel. A maximum 22.5℃ temperature drop was observed by using the GM-based PVT collector for slow-motion airflow. It is shown that the GM spikes are more efficient in low Reynolds numbers and can enhance air turbulence more effectively. The GM PVT collector has the best performance at low Reynolds numbers which is suitable for air-based PVT applications.
Analysis of heating behaviour based on occupancy patterns in residential building with radiant floor heating system
Authors: Shim Jisoo , Song Doo-sam
Published: June 2023

To achieve a carbon-neutrality, a reduction of heating energy consumption in residential building should be achieved. Although, lots of building energy policies were implemented to reduce heating energy consumption, it still accounts the largest share of global building energy consumption. Large number of researches pointed out the poor heating energy management by occupant makes inefficient heating energy consumption. In this research, the occupancy patterns and heating behaviour in Korean residential building are analysed. The occupancy patterns are identified with electricity consumption collected from 229 households. By comparing the heating energy consumption and occupancy patterns, the heating behaviour in residential building is analysed. The results show that about 81.2% of the analysed households applied continuous heating strategy whether occupants stay in the building or not. About 39.5% of the total heating energy consumption in 229 households, is consumed during unoccupied hours. The result of this research shows that the heating control strategy considering occupancy patterns can be greatly reduce the heating energy consumption in residential building.
Field study of system efficiency of detached house with solar energy system and fuel cell cogeneration system in Japan
Authors: Takaki Rie , Yoshino Hiroshi , Kobayashi Hikaru , Satake Akira , Hanabusa Toshiki , Konno Kenichi , Takahashi Kimio
Published: June 2023

In this study, the energy flow in detached houses in Sendai City in the Tohoku region of Japan where photovoltaic power generation system, solar thermal collection system, and fuel cell cogeneration system were installed was analyzed based on measured data. Hot water obtained by solar heat collected in the house is used to supply hot water to the kitchen throughout the year, to supply hot water to floor heating and to preheat the air supply of the HVAC system in winter, and to regenerate the desiccant wheel of the HVAC system in summer. A hybrid hot water supply system using city gas and a heat pump is used as an auxiliary heat source for a solar thermal system. As a result, the monthly energy self-sufficiency rate, energy efficiency and heat loss rate of the house for three years were calculated, and the necessity of the optimization of the operation method of the solar thermal system was found. In addition, daily analyses of solar thermal system in winter and summer suggested the importance of the operation corresponding to the weather.
Optimal Economizer Control of VAV System using Machine Learning
Authors: Lee Jin-Hyun , Lee Hye-In , Ji Kyoung-Hwan , Cho Young-Hum
Published: June 2023

Energy efficiency of the HVAC system can be improved through system renovation and operating method improvement. Economizer control, one of the energy efficient measures through improvement of operating method, introduces outdoor air when outdoor air is sufficient for cooling. There are high/low limit that determine the range of economizer control and mixed air temperature as control set-points. Economizer is controlled with the user's or manager's experience, and the set-point is operated fixed. This causes problems energy waste because it does not consider indoor and outdoor environments. Therefore, the purpose of this study is to develop an optimal economizer control of VAV system that resetting the set-point considering the indoor and outdoor environments. To this, a machine learning model was used to develop a model that predicts the future state based on the current state. Based on the developed prediction model, the optimal economizer control of VAV system that resets the mixed air temperature set-point in real time was developed and the control method was evaluated through simulation. As a result, it was confirmed that the mixed air temperature set-point changed in real time, and that about 20% of energy consumption was saved compared to the existing dry- bulb temperature control.
Data-driven Optimal Control of Single Duct VAV Terminal Unit
Authors: Kim Hyo-Jun , Lee Han-Gyeol , Jing Jia Jun , Cho Young-Hum
Published: June 2023

The purpose of this study is to propose a control method that optimizes the set point of the variable air volume (VAV) terminal unit using real-time prediction model of indoor thermal and air environment and energy consumption. Indoor thermal environment and air environment are predicted through indoor load and carbon dioxide (CO2) concentration. A prediction model was developed through operation data of the VAV terminal unit by artificial neural network (ANN) algorithm. The developed prediction model was used for real-time set point control of the VAV terminal unit. The optimal control of VAV terminal unit can be expressed in 3 step. First, it predicts the current indoor load and CO2 concentration. Second, all supply temperatures and supply air flow rate that can be provided in the predicted condition are repeatedly simulated. Finally, the set point of the minimum energy consumption is applied to the control. The evaluation of the proposed control method was compared with the dual maximum control logic. Comparative evaluation was performed using TRNSYS. It was confirmed that the proposed control method reduced the reheat coil energy consumption by about 20% and the air supply fan energy consumption by about 17% compared to the existing control method.
Exploring Hydrogen-Based Energy Storage Systems for Canadian Residential Buildings: An Energy Evaluation Methodology
Authors: Wu You , Zhong Lexuan
Published: June 2023

In recent years, integrating solar energy systems and hydrogen-based energy storage systems into residential buildings has shown promise in reducing urban greenhouse gas emissions and achieving clean energy supply. However, there is a lack of evaluation on the application potential of hydrogen-based energy storage systems in urban residential buildings. Therefore, a comprehensive energy evaluation method that considers urban building energy differences was implemented in 20 Canadian cities to evaluate the net-zero energy building status. The simulations were based on a typical residential building in North America. The results indicate that, for selected cities, the hydrogen-based energy storage system effectively addresses the seasonal energy mismatch and improves the energy self-sufficiency rate of urban residential buildings. These cities are classified as net-zero energy cities, nearly zero-energy cities, and non-net-zero energy cities based on their energy self-sufficiency rate. It is recommended to adopt hydrogen-only energy storage systems, hydrogen-electricity energy storage systems, and diverse renewable energy resources as integrated solutions to achieve net-zero emission buildings. The proposed energy analysis method can provide technical references for Canadian planners to plan a reasonable hydrogen roadmap for urban residential buildings.
Technical Assessment of Frozen Soil on Geothermal Heat Pump Technology in Western Canada
Authors: Keramat Fatemeh , Zhong Lexuan
Published: June 2023

This study examines the thermal performance of a two-dimensional borehole system, featuring a U-shaped pipe embedded in porous soil, through the application of computational fluid dynamics. The investigation encompasses 24 cases, assessing the impact of various factors such as soil thermal conductivity (k = 1.5, 1.84, 2 W/mK), average soil temperature (T = 280-285 K), and soil moisture content (10%-55%) on ice formation and heat transfer enhancement. The k-ε turbulence model and Darcy-Forchheimer model are employed for the pipe and porous medium, respectively. Furthermore, a solidification model is utilized to monitor potential ice formation within the system. The findings reveal that an increase in soil thermal conductivity enhances heat transfer between the soil and pipe while simultaneously reducing ice formation. Additionally, higher soil moisture levels lead to an elevated outlet temperature for the pipe and decreased ice formation in the soil. Lastly, it is observed that ice formation becomes negligible when the temperature reaches 285 K.
Classification of typical layout design for Indonesian apartment buildings
Authors: Prasetya Andhika Budi , Ho Anh Dung , Kubota Tetsu
Published: June 2023

Along with rapid urbanization, housing development increased in major cities worldwide. Public and private apartments have been constructed rapidly in Indonesia to accelerate housing provision, particularly in urbanized areas of major cities. From the early era of apartment construction to the present, many design prototypes have been implemented for various specific purposes such as energy-saving. Nevertheless, no comprehensive study has determined a typical layout of apartment buildings in Indonesia. The typical layout design is useful as the base model for building simulations. This study sought to classify the typical layout design of public and private apartments in Indonesia, using the selected building drawing data ranging from 1986 to 2021. We obtained primary data consisting of 268 public apartments from 22 cities and 268 private apartments from 9 major cities in Indonesia. To determine the typical layouts, both qualitative and quantitative analyses were conducted. As a result of this study, a pair of typical public and private apartment buildings which include the 1-bedroom unit and 2-bedroom unit types have been selected as the typical layout of the Indonesian apartment building. The results of the typical layout classification could be utilized as a standard testing model for designing future apartment building prototypes.
Scenario analysis of embodied energy and CO2 emissions for multistory apartments in Indonesia
Authors: Alvarez Diego , Kouda Riko , Ho Anh Dung , Kubota Tetsu
Published: June 2023

Contribution in the building sector to the global warming can be tackled by diminishing greenhouse gas (GHG) emissions (mainly CO2) not only from operational energy but also from the embodied energy (EE) of construction materials. Harvested Wood Products (HWP) such as Cross Laminated Timber (CLT), Glued Laminated (Glulam) timber, among others, make multistorey wooden buildings possible. These wooden buildings could help to reduce EE and CO2 emissions significantly. A material flow analysis (MFA) using an I-O (Input-Output) table was used to compare three scenarios for an 8-story apartment building in Indonesia (total floor area: 9140 m2): First, the building had a reinforced concrete structure. Second, the building had a “hybrid” structure with reinforced concrete cores and first-floor elements, consisting of CLT floor panels, and Glulam columns and beams. Third, the building used only CLT panels besides reinforced concrete cores. The results showed that the last scenario achieved the largest CO2 emissions and embodied energy reductions (58 t-CO2 and 905 GJ), compared with the first scenario (81 t-CO2 and 1110 GJ). Furthermore, we compare two methods to apply displacement factors (DF) to assess the CO2 emissions savings for each CO2 ton in wood products substituted in place of non-wooden products between the three building scenarios.
Analysis of Thermal Environment of Waterfront Space in Summer in Mountain City: A case study in Chongqing, China
Authors: Ma Jinhui , Huang Haijing
Published: June 2023

A crucial component of the urban ecology, waterfront space plays a key role in mitigating the urban heat island effect. However, waterfront spaces in mountain cities differ greatly from those in plain cities in terms of spatial form and environmental factors. Accordingly, it is urgent to study and improve the thermal environment of waterfront spaces in mountain cities. According to the spatial morphological characteristics and shading means of the waterfront space in Chongqing, a typical mountain city in China, the summer thermal environment of the waterfront space has been studied through field measurements. The outdoor thermal environment factors assessed include air temperature, relative humidity, wind speed, and mean radiation temperature. The results showed that the cooling effect was more significant at 1 m from the water's edge and decreased as the elevation increased. Air temperature and humidity showed a clear stratification characteristic with increasing elevation. At the same time, viaduct-shading was the most effective way of reducing heat stress, followed by the combined shading of sun sails with building-shading, while tree-shading was the least. This study offers basic data for further study and optimization of shading strategies for waterfront spaces in mountain communities.
Optimal Design Method for Surface Shape of Exterior Material to Improve Thermal Environment in Streets
Authors: Futaoka Kako , Yoshida Shinji
Published: June 2023

Retro-reflective materials have garnered attention as a countermeasure against heat island phenomena. However, the existing materials are inadequate for improving the thermal environment of outdoor spaces because these have been developed for traffic signs. Hence, in this study, an optimal design method for near-infrared rays retro-reflective materials to be installed on the exterior surfaces of buildings is proposed. It consists of a multi-objective genetic algorithm (MOGA) coupled with numerical analysis based on a ray tracing method. First, the outline of the method is shown. Next, the investigation of optimized surface shapes is presented. The results show that in individuals with high summer reflective performance, most of solar radiation hits a surface element only once and reflects upward in summer. In the investigation, the elevation angles of surface elements were approximately 70° and 60° for the installations in the south and west, respectively. It is predicted that the normal of the surface element where solar radiation reaches first is one of the determinants of the summer reflective performance. In addition, the effect of installation city or direction on the optimal design is analyzed. The results show that the direction does not significantly affect, the city suggests to affect the optimal design.
The impacts of climatic conditions on dengue fever and general emergency hospital admissions in tropical Indonesia
Authors: Asiga Cahya Adhianti Rosa , Kubota Tetsu , Putra Pradana Radyan , Soo Lee Han
Published: June 2023

Changes in climate parameters such as air temperature, rainfall, and humidity may dramatically impact the occurrence of infectious diseases. Dengue fever is a prevalent disease that has been extensively reported in relatio to climate change, particularly in tropical countries such as Indonesia. In addition, the consequences of climate change may affect the physiological responses of our bodies, which could lead to a rise in hospital admissions even in tropical countries. Wet Bulb Globe Temperature (WBGT) is an index to estimate the effect of air temperature, humidity, and solar radiation on human bodies. First, this study aims to investigate the influence of climatic conditions, including air temperature (AT), relative humidity (RH), and rainfall (RF), on the occurrence of dengue fever in Jakarta, Bandung, and Malang city, through a cross-correlation analysis. Second, it also explains the relationships between WBGT and general emergency hospital admissions in Indonesia and Japan. The results showed that climate conditions such as rainfall and humidity had a strong correlation with the incidence of dengue in Indonesia, with a relatively short lag of around 2-5 months in the form of negative values, while positive values were observed with a lag of 9-10 months with some exceptions in Jakarta. Extreme WBGT changes do not affect general emergency hospital admissions in both Hiroshima and Indonesian cities, although the WBGT changes clearly affected the emergency hospital admissions caused by the heat stroke in Hiroshima.