Journal of Environmental Engineering (Transactions of AIJ)
Online ISSN : 1881-817X
Print ISSN : 1348-0685
ISSN-L : 1348-0685
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Showing 1-10 articles out of 10 articles from the selected issue
    2020 Volume 85 Issue 767 Pages 1-9
    Published: 2020
    Released: January 30, 2020

     This study proposes a simplified prediction method of heat storage amount of walls including Phase-Change Materials (PCM).

     Chapter 1 introduces the purpose of this research. PCM contributes to the temperature stability in houses, and room temperature stability is related to heat storage amount of walls. In previous studies, calculation methods of heat storage amount of walls are established. However, these methods aim at walls without phase change. Therefore these methods cannot be applied to walls including PCM. Heat storage amount of walls with PCM is usually confirmed by experiment or difference calculation, but it takes a long time to execute these methods. Hence, this study proposes a simplified prediction method of heat storage amount of walls including PCM. Using the proposed method, there is no need to execute convergent calculations nor repeated calculations for several days.

     Chapter 2 presents the method of prediction. Temperature change inside the wall and heat flux at the surface of the wall are assumed to be sinusoidal waves. Furthermore, it is assumed that phase change occurs at a particular temperature without temperature range. Heat storage amount is predicted by the latent heat, the thermal conductivity of PCM, temperatures of the inner and outer side of the wall, temperature gradient in the wall, and so on.

     Then, Chapter 3 shows the comparison between the simplified prediction method and difference method. The accuracy of the method is confirmed by comparison. The prediction results show less heat storage amount and heat storage quantity under some circumstances. However, there is a strong association between the prediction result and the difference method result.

     Some issues must be considered when predicting the heat storage amount of walls including realistic PCM. These issues are presented in Chapter 4.

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  • Yukio KOMATSU, Takahiro CHIBA, Akira FUKUSHIMA, Sayaka MURATA, Masahir ...
    2020 Volume 85 Issue 767 Pages 11-18
    Published: 2020
    Released: January 30, 2020

     We propose a method for testing the drainage performance and waterproof performance of the structural part of a wall in the external insulation, and a method for reducing the risk of water leakage by cutting drainage grooves on the insulating material, and show its performance by full‐scale model experiments and laboratory experiments. The research results are summarized below.

     1) Full‐scale model experiment on drainage performance

     The outer wall of the outdoor experimental building was used to clarify the behavior of infiltrating rainwater on the back of the EPS external insulation wall. In order to examine the effect of the presence or absence of the drainage layer on the drainage performance, the walls where the grooves were cut on the back of the EPS and walls without the usual groove were tested at the same time. Red colored flush water were injected into the wall installed in the experimental building, and the drainage performance was confirmed visually. The obtained findings are as follows.

     ・ For the drainage condition of the whole, there is a specific water channel in the grooveless wall and drainage is concentrated, but in the grooved wall, it was possible to disperse in the drainage and avoid partial concentration of the flow.

     ・ It was found that the flow was blocked in the grooveless wall, especially at the lower end because of the drainage condition of the wooden horizontal base. In the grooved wall the flow was blocked, but it drained smoothly.

     ・ At the longitudinal joint of the grooved thermal insulating material, the water was retained, and it is considered necessary to study the shape of the groove to further improve drainage.

     2) Labo test on waterproof performance

     We made a full-scale wall following the plaster on insulation method and tested drainage performance. The effectiveness of the drainage groove was confirmed by comparing the grooved and non-grooved test results. The waterproofing performance test was conducted according to the JIS standard, and the method for testing the waterproofing performance of the plaster on insulation was established. The obtained findings are as follows.

     ・ In the experiment without pressure, after 1 minute 27 seconds, water leaked from the window top to the internal wall, and after 6 minutes 38 seconds water also leaked to the internal wall from the lower end of the wall.

     ・ In the experiment in which pressure was applied, leaked water from around, the screw and above the window to the interior at a pressure of 100 Pa. At 500 Pa, water leaked to interior from the lower end of the wall, and about 10 cm of water accumulation occurred. Water leaked from around the screwe at 700 Pa, and water leaked from around the nail at 2.0 kPa.

     ・ According to the test results of the wall with groove, the water did not stay behind EPS, and the water leakage did not occur in the interior.

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  • Sadaharu OSAMURA, Hiroaki SAITO, Masao NAKAJIMA
    2020 Volume 85 Issue 767 Pages 19-28
    Published: 2020
    Released: January 30, 2020

     The wall assembly with vented cavity using the siding is installed for durable improvement in many wooden houses. The houses with less projected eaves built on very narrow and small properties are increasing in recent years. According to an investigation of moisture damage by authors, many of houses which internal condensation occurs were built in less than ten years. Deteriorated siding and joints in these houses have potential for water absorption and rain penetration. It is considered that these accumulated moisture have significant impact to cause the internal condensation within stud cavity, when surface temperature on the siding raises by solar radiation. However there are few studies regarding hygrothermal behavior in consideration of these impacts such as water absorption and rain penetration at outside finishings.

     To unravel mechanism of the internal condensation due to moisture cause the rain water, lab-experiments and field measurements were conducted. In the lab-experiments, water penetration rate and water absorption coefficient of sidings were quantitated. In the field measurement, the internal condensation was reproduced by intermittent injection of rain water into the vented cavity. Additionally, the drying performance of different ventilation configurations were compared by humidity and moisture content variations within wall assemblies in field measurements. The findings of the study are as follows;

     (1) Quantity of rain penetration form siding joints : Quantity of rain penetration from siding joints of four installation methods were measured by water spray test. It was confirmed that there were significant differences in the amount of water penetration between the installation methods. In the cases which condensation occurred, the water penetration rate was 5 to 12 % at low wind speed. From the result, it is considered that intermittent rain penetration occurs with high frequency in rainy day.

     (2) Water absorption test from siding surfaces : Quantity of water absorption of siding with chalking and sound one just after the testing are 0.62 kg/m2 and 0.06 kg/m2 respectively. This result is suggested that the quantity of absorption water increased with deterioration of the surface coating due to aging. In addition, since water was absorbed just after water absorption, it is considered that water is absorbed and retained every time it rains.

     (3) Impact of rain penetration and water absorption of exterior system on hygrothermal behavior within wall assembly at the experimental house : For the external finishing of the experimental house, deteriorated sidings were installed to four types of vented cavity. To verify hygrothermal behavior within wall assembly, authors reproduced intermittent long-term rain penetration into the vented cavity, and measured the temperature, humidity and moisture content variations.

     Authors confirmed that moisture accumulation in wall assembly being reproduced on east side of the wall, when the moisture retained in the sidings and vented cavity was released into the wall assembly. This phenomenon was caused when the surface temperature on sidings were raised by solar radiation after rain. Especially in case of the configuration with low ventilation performance, the condensation occurred for 10 to 13 hours in daytime. As for the configuration with secured ventilation performance, the internal condensation did not occur.

     In conclusion, aforementioned results verified that the moisture condensation at the vapor retarder due to rain water was caused by co-occurrence of several factors, i.e. rain penetration, water absorption, insufficient ventilation and solar radiation.

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  • Results of summer survey on two facilities in Kasugai city
    Aya YOKOE, Megumi MITSUDA, Toshimi TANAMURA, Motoi YAMAHA, Bishnu NEPA ...
    2020 Volume 85 Issue 767 Pages 29-35
    Published: 2020
    Released: January 30, 2020

     As a very aged society, present-day Japan has an increasing demand for numerous elderly facilities with good environment in terms of both thermal aspects and odor. This study examines the characteristic thermal and odor environment, as both elements are related, of such facilities through practical observation during summer.

     Two facilities, A, built in 2009, and B, built in 1997, were the survey targets. In each facility, the parameters of thermal environment, i.e., temperature and humidity, were continuously measured at a representative point for 24 h. Four activity-meter-equipped care givers attending the elderly were asked to participate during this period. They were given a questionnaire to answer approximately every hour, and their behavior during the measurement was visually observed and then recorded.

     Similarly, continuous measurement for odor environment was performed every 30 min using a hot-wire-type semiconductor gas sensor, smell evaluation by the researchers, and measurement by an ammonia detection pipe. Moreover, a 250‐L odor sample was placed into a collection tube. Evaluation procedures for the odor included a “6‐stage odor intensity evaluation,” a “9‐step free discomfort evaluation,” and a “smell quality evaluation” based on the semantic differential (SD) rating scale.

     Measurement results for the thermal environment indicated that facility A had higher temperature than facility B. Additionally, even when the same PMV values were assessed for the elderly and the caregivers, the latter deemed facility A as “hot” and “uncomfortable” owing to high temperature, which exceeded the recommended comfortable range.

     In contrast, odor concentration in facility A was 63, whereas it was ≤10 for facility B. Smell evaluation and odor component analysis both detected odors of sweat and building materials, particularly in facility A, which were thus presumed as sources of odor generation and emission. Based on the amount of generated odor, facility A requires a ventilation rate of 6.3 times/h rather than the current 2.6 times/h, whereas facility B, operating at 1.9 times/h, met the threshold requirement.

     Thus, facility A exhibits an excessive thermal environment that potentially leads to odor generation. An in‐depth study of the relationship between thermal and odor environment, with sufficient accumulation of data, will be explored in future work. Nevertheless, given a comfortable thermal environment, we believe that a ventilation rate of 2 times/h is suitable in this case.

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  • Takuya KISHI, Sihwan LEE, Yoshiharu ASANO
    2020 Volume 85 Issue 767 Pages 37-44
    Published: 2020
    Released: January 30, 2020

     A local air-conditioning for occupied room is mainly used in Japan, thus individual cooling and heating units placed in each room of the house such as a stove, an air conditioner, and a kotatsu etc. By using these individual cooling and heating units, health risks have been occurred as a problem such as mold and tick caused by dew condensation or heat shock caused by temperature irregulation. The number of deaths due to heat shock is estimated to be 17,000 people per year in Japan, accounting for about 30% of 59, 416 deaths from annual accidents.

     To solve this problem, the central cooling and heating system has been received attention to prevent the heat shock in residential buildings. The central cooling and heating system has been limited in Japan, because the space of mechanical equipment room and individual needs to adjust the thermal comfort have been increased. So, the whole-house air conditioning system is proposed and installed to residential buildings by several HVAC makers in Japan, because the system is only needing a small space for mechanical equipment room. However, the fans are CAV despite of the load changes from moment to moment that the room temperature difference and daily range occur. To improve this problem, it is effective to introduce VAV for the blower fans, and there is also a past study on the VAV system of the central air-conditioning, but there is no document which studied about the effect of environmental improvement. Therefore, in this study, evaluating the effect of improving indoor thermal environment by central air-conditioning system with VAV introduced in the residential house, using the actual measurement and the coupled calculation of the CFD and the ES, comparing the existing CAV system and the individual type air-conditioning generally used.

     The indoor thermal environment improvement effect on introducing VAV to the blower fan of the central air-conditioning in the residential building is analyzed on following 4 aspects.

     1. The percentage of the setpoint temperature ± 2 ºC for the whole house is 45 to 75% for the central air-conditioning CAV and about 60% for the individual air conditioner, whereas the central air-conditioning VAV is about 90%, and the proportion of comfortable areas is high.

     2. Comprehensive central air-conditioning CAV, VAV increased PMV by 10 to 20% compared with individual air conditioning.

     3. The temperature difference of up to 10 ºC is generated for individual air-conditioning, while central air-conditioning is 6 ºC, the temperature difference of 4 ºC is relaxed. The bathroom and undressing room, which are related to bathing activities, are also kept at 20 ºC or more, and the effect of suppressing heat shock is revealed.

     4. By supplying the blowing temperature of the air-conditioner and the air flow rate obtained from the heat load, it is possible to set the indoor temperature roughly to the target setpoint temperature. Therefore, it is possible to equalize the indoor temperature by the VAV system by sensing the outdoor air condition and the air-conditioning blow temperature.

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  • Takahiro YAMAMOTO, Daisuke SUMIYOSHI, Youngjin CHOI
    2020 Volume 85 Issue 767 Pages 45-54
    Published: 2020
    Released: January 30, 2020

     The results of a measurement survey of PEFC installed in detached houses in Fukuoka City are shown in this paper. The purpose of this measurement survey was to collect the measurement data of fuel cells that are practically used in households. This measurement data is used for simulation programs of PEFC and other fuel cells for residences and the research concerning of examination method of the fuel cells for residences based on industrial standard.

     At first, the purpose and background of this research are shown. Since commercial sales began in 2009, the development and dissemination of the fuel cells for residences have progressed. However, there are only a few case examples of measurement surveys targeting recent model specifications and the relationship among electricity usage, hot water usage and the power generation amount of fuel cells has not been researched enough. A detailed measurement survey of relatively new PEFCs that were purchased around 2013 was conducted and the measurement data were collected.

     Secondly, the outline of the measurement survey, the characteristics of equipment specification of fuel cells that are measured in this paper, and the definition of evaluation items used in this paper are shown. The households subjected for the survey in this paper have introduced Home Energy Management System (HEMS), so they can obtain electricity usage, city gas usage and the power generation amount of fuel cell at hour intervals. These data are totaled, and the life schedule of each household is confirmed.

     Then, the data that were obtained in this research are totaled and the analyses and discussions concerning the evaluation items shown in chapter 2 were performed. The catalog spec of the measured device shows that the efficiency of power generation is 36% by HHV conversion and that of heat rejection is 51%; however, Usage end, the efficiency of power generation of household-I was 35%, that of household-II was 30%, and the heat rejection of household-I was 41%. It was also found that the energy of about 0.4kWh is consumed each day for the start and stop of power generation. This is equivalent to 5-10% of the power generation amount. Sometimes a power generation contribution rate becomes low because the changes of power generation amounts in the fuel cell cannot follow the small fluctuations of electric power usage. In many cases in past research, the average value of the interval of about 1-30 minutes is used as load data to be input. However, it was found that the calculation time interval should be 10 seconds or less for accurate estimation. Finally, the findings obtained through the contents of this paper and the tasks in the future are organized.

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  • Takahiro UENO, Youngjin CHOI, Kentaro TAKAHASHI, Daisuke SUMIYOSHI
    2020 Volume 85 Issue 767 Pages 55-65
    Published: 2020
    Released: January 30, 2020

     This paper describes development of co-generation system (CGS) model in individual building and District co-generation (DCG), and the effect analysis by the diffusion of CGS in Japanese business area. Developed model in this paper calculated CGS operation at 5-minute interval. And it contain heat supply piping length, transport power, piping heat loss in DCG calculation. The estimating of CGS diffusion effect confirmed the effect of reverse power flow permission and the demand aggregation by DCG in Japanese business area.

     11st chapter describes a background of this paper. The city in Japan needs to construct distributed energy supply systems. And CGS is considered to be one of effective distributed energy systems, but the details of its spread effect has yet to be clarified. Therefore, we developed a CGS operation model in urban scale to the effect analysis by the diffusion of co-generation system in Japanese business area.

     2nd chapter indicates the development of CGS model. We made a CGS model based on past programs. This model calculated CGS operation in 5-minute interval. And it also considered heat supply piping length, transport power, piping heat loss in DCG calculation.

     3rd chapter is the development of a total energy supply system. In order to develop this system including CGS, This paper combined CGS, multi air conditioning, hot water storage tank and hot water supply boiler. This system operates each facility model in 5-minute interval and calculates annual primary energy consumption of each non-residential buildings in target area.

     4th chapter describes case studies. We analyzed six areas with different characteristics of located buildings. Pre-stage of the analysis estimated the 5-minute power demand and each heat demand for cooling, heating and hot water supply of each non-residential building in these target areas. Moreover, we analyzed dozens of calculation results of each area in two case studies and confirmed the energy saving effect of reverse power flow permission and the demand aggregation by DCG in Japanese business area.

     5th chapter is conclusion. It summarizes the main points so far and shows future issues.

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  • Junya YAMASAKI, Toshiharu IKAGA, Norihiro ITSUBO
    2020 Volume 85 Issue 767 Pages 67-77
    Published: 2020
    Released: January 30, 2020

     A global standard method for measuring environmental loads in administrative divisions has not been officially established for environmental accounting at the local government level. As a consequence, environmental accounting has not been adopted by local governments as widely as private companies around the world.

     Life cycle impact assessment (LCIA) is one aspect of research in the field of life-cycle assessment, whereby environmental loads throughout the life cycle of products and services are measured in a quantitative way. Research in which environmental loads are determined according to geographical location has become more and more important. This study therefore focused on administrative divisions in 42 countries, most of which are OECD members, and attempted to quantify the annual environmental loads emitted within each division in the year 2015, using the global-scale LCIA method. For this, this study leveraged the assessment theory Life-Cycle Impact Assessment Method Based on Endpoint Modeling 3 (LIME3). This method is able to calculate assessment results in monetary units while integrating the environmental loads of several impact categories, such as climate change and land use, based on environmental conditions and environmental science.

     Using statistical information that was reliable, verifiable, and comparable, this study calculated environmental loads in administrative divisions in 42 countries. The total environmental damage amount for the 42 countries was calculated to be 5.22 trillion USD. The top five amounts were land use (1.76 trillion USD), water consumption (1.36 trillion USD), forest resource consumption (0.70 trillion USD), climate change (0.52 trillion USD), and fossil fuel consumption (0.50 trillion USD). When the damage amounts were divided by the area or population of each division, the average amount per unit area for all Territorial level 2 (TL2) regions was calculated to be 67,300 USD/km2 (area-weighted average), and the average of amount per capita was calculated 1,250 USD/capita (population-weighted average). These damage amounts per unit area and per capita were placed on a world map according to impact category to visualize the regionality of environmental loads worldwide. The amount per unit area for most categories showed a trend similar to population distribution around the world, and the values for land use also showed a trend indicative of local agricultural activity in some countries. In particular, the amount per capita for climate change as well as the total of all categories showed a contrasting trend to the amount per unit area, and the value tended to be relatively lower in densely populated areas around the world.

     The variation coefficient for the damage amounts per unit area and per capita was calculated for each region in order to statistically capture the disparities of environmental loads according to impact category. The disparities of environmental loads that were deeply related to housing, such as climate change and waste, tended to be narrow among TL2 regions worldwide. From these results, this study revealed environmental impacts around the world from the perspective of several categories, thus providing information useful for making decisions about international environmental policies.

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  • - Focusing on the calculation method of biomass entropy and application of the closed-circulation model -
    2020 Volume 85 Issue 767 Pages 79-88
    Published: 2020
    Released: January 30, 2020

     This paper describes the trial and its results of entropy analysis on wood biomass circulation relating building. The reason for conducting an entropy evaluation is that the circulation of working matter and entropy disposal obtained from that are the indispensable requirements against the sustainability of all the working systems. The purpose of this paper is to show the methodology of entropy analysis on wood biomass circulation relating building and characteristics and requirements on biomass circulation based upon entropy.

     The wood biomass circulation system was assumed to be composed of five subsystems: forest subsystem, logging subsystem, timber production subsystem, biomass-fuel production subsystem and biomass-fuel combustion subsystem. The amount of carbon dioxide and water vapor emission from the biomass-fuel combustion subsystem was assumed to be the same amount of those to be used for photosynthesis in the forest subsystem. This assumption enables us to articulate matter balance from wood biomass to carbon dioxide and water vapor and their vice versa as the working matter in wood biomass circulation like water circulation in closed loop. The authors calculated matter balance, energy balance and entropy balance in all the subsystems. We also developed an approximate formula for calculating absolute entropy of wood biomass which has no chemical formula.

     The results obtained from this study are following.

     1) The developed approximate formula for calculating absolute entropy of wood biomass enables us to estimate absolute entropy of high molecule-organic compounds like wood biomass with high approximation accuracy.

     2) Modelling biomass circulation with the same output of carbon dioxide and water vapor in biomass combustion subsystem as input of those in forest subsystem, it was found that entropy of biomass is much smaller than other materials in working matter of the wood biomass circulation in spite of used material and utilizing wood biomass as low-entropy fuel can make biomass circulation complete as one closed loop.

     3) If both material and thermal use of wood biomass are not realized, total entropy disposal becomes much smaller than that in case with material and thermal use of wood biomass, even though the amount of entropy contained by combustion gas of wood biomass are compensated with wood biomass circulation.

     4) If the care condition of forest becomes bad, the absolute entropy storage gets beyond 0.222 GJ/K in the forest subsystem.

     5) On one hand, the share of thermal flux entropy in total entropy input is 9.9 % in forest subsystem. On the other hand, that in output is 60.1 %. The share of thermal flux entropy in total entropy output becomes larger than that in total entropy input in forest subsystem.

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  • Empirical analysis using the assessment data of CASBEE Yokohama
    Hideyuki TAKADA, Yoshikuni YOSHIDA, Shun KAWAKUBO, Ayuta YAMAGUCHI
    2020 Volume 85 Issue 767 Pages 89-95
    Published: 2020
    Released: January 30, 2020

     There has been increasing interest in ESG management and movements to improve the environmental performance of real estate. Initiatives regarding SDGs (sustainable development goals) are expanding in corporate environmental behavior in answer to global environmental problems. In the United States, there are many reports showing the relationship between environmental performance certifications such as “LEED” (Leadership in Energy and Environmental Design) and rental income and real estate value, but in Japan, accumulation of comparable research is not as advanced as in Western countries. Regarding studies in Japan, target real estate comprises mainly office buildings and there are few studies analyzing the relationship between high environmental efficiency and real estate sale prices and used transaction prices for condominiums.

     The principal aim of the present study is to clarify the effects of the environmental efficiency of buildings on real estate prices. Specifically, focusing on local government “CASBEE” (Comprehensive Assessment System for Built Environment Efficiency), we targeted apartment buildings certified by CASBEE Yokohama (485 buildings completed after 2006) and examined the effects of the level of each factor that composes CASBEE with regard to (1) new construction sales prices and (2) the influence on the rate of change in used transaction prices (rate of decline) by the hedonic approach. The targets of analysis were all 485 buildings in (1) and of the 80 buildings that were newly built in 2006 and 2007, those that were used transactions 5 years and 6 years after construction in (2).

     The analysis results revealed the following three points.

     1) When the BEE value, which is a comprehensive indicator, increases by 1 point, the average unit price increases by approximately 5.5%.

     2) A 1-point increase in BEE value has a positive impact of 1.63% on the annual rate of change of the used transaction price (decline rate).

     3) It is economically advantageous to purchase a condominium with a high BEE score when future sale (asset value) is taken into consideration.

     It is our hope that widespread understanding of the results of the present study by concerned parties will lead to the further spread of environmentally conscious real estate. Moreover, by investigating environmental efficiency needs and willingness to pay on the customer side, we aim to clarify the differences in environmental efficiency that suppliers and consumers emphasize, leading to the future proposal of more effective environmental efficiency display and disclosure methods.

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