Publisher：Energy  

To decrease the latent heat load of the air-conditioning system in residential buildings, we proposed a passive dehumidification and mechanical ventilation system that integrates energy recovery ventilation (ERV) into a passive dehumidification and solar collection (PDSC) system that can intelligently regulate the indoor hygrothermal environment, referred to as the PSE (PDSC & ERV) system. Field studies were conducted by monitoring the indoor temperature and humidity changes in the operating conditions using various systems. With the PSE system, the absolute humidity difference between the indoor and outdoor air was the most significant, and its ability to maintain a stable indoor relative humidity was the most remarkable compared with other systems. The PSE model had the lowest latent and total heat load compared with the exhaust-only ventilation model equipped with a standard insulated envelope without moisture adsorption and desorption function. Regression analysis showed that the higher the outdoor temperature, absolute humidity, relative humidity, and solar radiation in summer, the more significant the PSE system's latent heat load reduction effectiveness. Linear correlation between absolute humidity and energy-saving performance was the most evident, with a coefficient of determination as high as 0.98, illustrating the suitability of PSE systems for hot and humid areas.

DOI： 10.1016/j.energy.2023.129888

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Publisher：Journal of Cleaner Production  

Increasing energy efficiency and reducing emissions in industrial processes through waste-heat recovery systems are vital. The energy-intensive nature of professional laundry care generates waste heat from machines such as washers, dryers, and boilers. We focused on a waste-heat recovery system tailored for this sector. An accurate drying model is essential for analyzing its energy-saving potential. This study presents a water-potential-based drying model using equilibrium thermodynamics. Two measurement experiments and numerical simulations were conducted to verify the accuracy of the proposed model, and the experimental results were incorporated into the simulations. The first experiment collected and determined laundry samples' basic information and hygrothermal properties, including the surface area, initial weight, and heat and moisture transfer coefficients. The second experiment attempted to determine each laundry item's equilibrium water content and capacity at various humidity levels. Through simulations, a comparison was made between the surface temperature and water content predictions of the existing and proposed models. Experimental results revealed that the laundry surface temperature remained constant during the constant-rate drying period. However, during the falling rate period, it was influenced by water content. The drying characteristics differ based on the material and quilting method. The proposed model improved the temperature and water content predictions by approximately 80.07% and 63.08%, respectively, compared with the existing model. This model can effectively assess laundry drying processes, including the latent heat flux assessment of the indoor environment.

DOI： 10.1016/j.jclepro.2023.138735

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Publisher：Sustainability (Switzerland)  

The majority of the population in Indonesia lives in naturally ventilated and unconditioned residential buildings because they cannot afford energy services. This situation is common in many countries in tropical regions, negatively affecting the occupants’ health due to overheating. Therefore, housing types that can cool down indoor temperatures to the extent possible using a passive approach, rather than an active approach, should be developed. This study aims to improve naturally ventilated houses by considering the louver area and insulation of houses. First, we employ an on-site measurement for collecting data such as the indoor/outdoor temperature and relative humidity in an Indonesian city, Lhokseumawe. In addition, the experimental data are used to validate a numerical simulation model. Second, the numerical simulation is utilized to establish energy-efficient design solutions for houses in 14 Indonesian locations. The results show that, compared with the insulation cases, different louver areas insignificantly change indoor air conditions by approximately 0.3 to 1 °C. Additionally, the application of a combined performance improvement for both louver areas and building envelope insulation levels can reduce the indoor air temperature and relative humidity by 2.2 °C and 8%, respectively. Moreover, the daily cooling demand for the proposed improvement plan is reduced by 18.90% compared with that for the existing case. Furthermore, the annual cooling loads for the entire simulated regions are reduced by 46.63 GJ/year (23.09%). This study is a potential starting point for achieving zero-energy housing and occupants’ sufficient thermal comfort in unconditioned and naturally ventilated houses in Indonesia.

DOI： 10.3390/su151612173

Web of Science

Scopus

Publisher：E3S Web of Conferences  

With the aim of establishing a zero-energy housing (ZEH), an intelligent envelope system composed of a passive dehumidification and solar collection system (PDSC system) based on thermodynamic energy theory and an energy recovery ventilation (ERV) unit has been developed, abbreviated as PSE (PDSC & ERV) system, which can be expected to control the indoor hygrothermal environment by using renewable energy further to reduce the heating and cooling demand for the HVAC system. In this study, the measurement experiments were conducted in a wooden house equipped with a PSE system, and the temperature and humidity distributions in the rooms were assessed using thermohygrometer sensors. The field comparison experiments for the three systems (exhaust-only ventilation system, ERV system, and PSE system) were performed separately under various meteorological conditions in summer and winter. The measurement results in summer showed that the PSE system has a significant dehumidification effect compared to the exhaust-only and ERV-only ventilation systems and could effectively reduce the latent heat load caused by ventilation. The measurement results in winter indicated that the PSE system has the effect of heat collection and humidity control as well as reducing the sensible heat load originating from ventilation.

DOI： 10.1051/e3sconf/202339603025

Scopus

Publisher：E3S Web of Conferences  

Buildings use a large amount of energy, depending on the climate. To design buildings with high energy and thermal performance in the future, it is necessary to use weather data that reflect future climatic information. Some future weather files for building simulations have been developed. However, these datasets are based on different predictions, and each future weather file has a different creation process. Such methodological differences may lead to differences in predicting the energy and thermal performance of buildings. Understanding the characteristics of each data type is necessary for its appropriate use. However, limited information is available for properly utilizing future weather data for building simulations. This study aims to provide information on the characteristics of future weather data for better utilization. After thoroughly reviewing the existing data and creation methods, we propose a framework for understanding future weather data based on their creative process. We collected five types of future weather datasets available in Japan and compared their characteristics. One of these datasets is the future weather dataset based on climate information provided by the National Institute for Environmental Studies (NIES). We confirmed the degree of variation in each weather element and predicted cooling/heating demand using future weather data available in Japan.

DOI： 10.1051/e3sconf/202339605014

Scopus

Publisher：E3S Web of Conferences  

Louvre openings are widely used for ventilation in residences at tropical regions. Traditional households rely primarily on natural ventilation for cooling instead of using air conditioners throughout the year. Hence, a design strategy that maximizes the natural ventilation rate with an accurate discharge coefficient is necessary. The discharge coefficient for a traditional window without a louvre is 0.6. However, studies on discharge coefficients for louvre openings with sashes are lacking. Discharge coefficient will differ according to the installed sash owing to increased contraction and friction losses. Therefore, we determined the discharge coefficient value for various sash angles and the impact of the louvre geometric parameter on the discharge coefficient. To investigate the effects of geometry on the discharge coefficient, real-time natural ventilation rate was quantified using the tracer gas (constant concentration) method. Pressure difference, outdoor wind velocity, and temperature difference were also measured. The opening types were divided into three cases: louvres with a sash angle of 0, 15, and 30 with similar opening areas. The results show that discharge coefficients for louvres with sash angles of 0, 15, and 30 are 0.80, 0.62, and 0.41, respectively, indicating that the coefficient decreases with increasing sash opening angle.

DOI： 10.1051/e3sconf/202339602030

Scopus

Publisher：E3S Web of Conferences  

Biophilic design is aimed at creating a good habitat for people by enhancing the connectedness between people and nature in the urban environment; its effects on promoting psychological health are well known, but further studies are required to quantify the effects on physical and physiological aspects to provide a holistic view to support design practice. In this study, we focused on the physical aspect and quantitatively analyzed the effects of biophilic design on the thermal environment and occupants' thermal sensations. Field measurements and questionnaire surveys were conducted at a multifloor indoor garden in a public building in Kumamoto, Japan, with an artificial waterfall, pond, plants, and natural light as biophilic elements. Predicted mean vote was calculated using field measurement results as an objective indicator to assess thermal comfort. Questionnaires were used to verify the psychological effects and clarify the occupants' thermal sensations by comparing with field measurement results. The effects of the waterfall were studied when it was switched on and off. The results suggest the rationality behind incorporating biophilic design inside buildings, in terms of the physical aspect, highlighting the psychological effectiveness, especially during winter, and the benefits of thermal comfort, especially during summer.

DOI： 10.1051/e3sconf/202339601085

Scopus

Publisher：Building Simulation Conference Proceedings  

In this study, a new heat and mass transfer model in energy recovery ventilation (ERV) systems based on water potential as a moisture driving force, named the Water Potential (WP) model, was developed. WP model was compared with the existing numerical model which uses absolute humidity differences as a driving force by predicting temperature and absolute humidity of supply air side. Differences between the temperature calculated by WP model and the actual data were less than 0.8 %, comparable to that of the existing model. For the prediction of absolute humidity, the averaged error of the WP model was approximately 6.4 %, while the existing model`s error showed 10.1 %.

DOI： 10.26868/25222708.2023.1443

Scopus

Publisher：Environmental Science and Engineering  

Although many studies highlight the relevance of heat transfer through frames and aim at improving the thermal performance of the frame, unfortunately poorly insulated frames are still being sold in many regions of the world. Therefore, it is necessary to quantify the potential effect of strengthening on the window frame of nationwide. This study evaluates the impact of window frames on annual energy consumption and its contribution to CO2 emission reductions at the city-scale. The impact of frame material on annual energy consumption is approximately 0.11%–3.55%. Consequently, it was confirmed that the CO2 emissions can be reduced by approximately 4.76%–8.02% by alternative. In conclusion, when converted to the amount of CO2 gas absorbed by cedar, the absorption effect of 282,558–476,530 cedar trees can be obtained. Through this, it can be confirmed that, among the various elements of the building, changing the material of the window frame shows a significant energy saving effect, and that it is a considerable amount when converted into the city-scale.

DOI： 10.1007/978-981-19-9822-5_56

Scopus

Language：English   Publisher：Faculty of Human-Environment Studies, Kyushu University  

Even though the hot and humid conditions throughout the year, most Indonesian stay in a house that uses natural ventilation due to energy poverty and economic conditions. Commonly, they rely on natural ventilation by opening windows to achieve thermal comfort in the indoor environment. Therefore, an on-site survey and questionnaire were performed on more than 240 occupants and 115 naturally ventilated houses to investigate thermal comfort performance between two houses based on thermal sensation vote (TSV) and thermal comfort vote (TCV). In addition, some questions related to airflow scale, air freshness, thermal preference and body response are employed. The results present that type 1 is more comfortable than type 2. The study also reveals that the larger openings ratio is more acceptable than the few ones. Furthermore, this study confirms the adaptive behaviour where most occupants utilize the windows openings in the morning until noon and operate the fans during the night to modify indoor environment conditions to be more comfortable. Keywords: Naturally ventilated house, Indoor thermal comfort, Assessment, Tropical region

DOI： 10.15017/6788786

CiNii Research

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.3390/en15103692

Publisher：Energies  

Windows are among building components that have the strongest effect on thermal load. They play a significant role in heat loss in buildings because they usually have a largely higher thermal conductance than other components of the building envelope. Although many studies have highlighted the relevance of heat transfer through frames and aimed to improve their thermal performance, poorly insulated aluminum frames (thermal conductivity of aluminum is 160 W/m·K, while that of polyvinyl chloride [PVC] is 0.17 W/m·K) are still in use in Japan. Therefore, the U-values of different window frames were calculated, and annual thermal loads were calculated according to the window configurations, including the frame, glazing, and cavity. We focused on standard residential buildings in Japan with a total floor area of 120.6 m2 (two-story building), and the number of newly built houses and the application rate of window configurations in 2019 were surveyed to estimate the CO2 emissions by regions. CO2 emissions were reduced by approximately 3.98–6.58% with the application of PVC frames. Furthermore, CO2 emissions were converted into the amount of CO2 gas absorbed by cedar trees, which cover nearly 18% of the total land area of Japan. In conclusion, analogous to the amount of CO2 gas absorbed by cedar trees, the absorption effect was equivalent to 327,743–564,416 cedar trees. Changing the window frame material can facilitate a significant energy-saving effect as a considerable amount of energy is saved, especially at a city scale.

DOI： 10.3390/en15103692

Web of Science

Scopus

Publisher：Energy and Buildings  

As social interest in energy welfare increases, support programs and policies for fuel poverty are steadily being implemented. Energy subsidies play a significant role in improving the indoor thermal conditions affected by fuel poverty. However, various measures to reduce green-house gas emissions in the building sector are being applied. As a result, a balance between energy welfare and energy saving policies is required. This study aims to analyze the effect of an energy subsidy on improving the indoor temperature and heating energy consumption in low-income dwellings. Long-term and detailed measurements and surveys were conducted for 16 low-income households in an apartment complex in Korea (semi-cold climate). The indoor temperature and heating energy use with/without energy voucher were analyzed. In addition, the annual heating energy consumptions of all 1460 households in the same apartment complex were analyzed. The results showed that the indoor average temperature of the households receiving the energy subsidy was 24.68 °C, and the households without the energy subsidy were 22.62 °C. In addition, the indoor minimum temperature of the households receiving the energy subsidy was about 1.5 °C higher. The annual heating energy use increased by 59.9% for the older building and 26.6% for the newer building compared with those who did not receive energy subsidies. Energy vouchers have a strong influence on the indoor thermal condition and heating energy consumption of low-income dwellings. The energy subsidy policy for the low-income households needs to be re-examined in terms of energy savings and energy welfare.

DOI： 10.1016/j.enbuild.2021.111678

Web of Science

Scopus

Event date： 2023.5

Language：English  

Country：Japan  

Event date： 2023.5

Language：Japanese  

Country：Japan  

Event date： 2022.9

Language：English  

Country：Japan  

Event date： 2022.7

Language：English  

Country：Canada