Journal of Environmental Engineering (Transactions of AIJ)
Online ISSN : 1881-817X
Print ISSN : 1348-0685
ISSN-L : 1348-0685
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  • A ventilation network approach to double-skin cavities, blind circulation airflow and blind operation performance
    Hiroshi OHGA
    2020 Volume 85 Issue 775 Pages 645-654
    Published: 2020
    Released: September 30, 2020

     A multi-space model of a double-skin façade system is proposed using the practical thermal load simulation program NewHASP and the ventilation network program employed in mechanical design practice. Using this model, thermal performance evaluation of various venetian blind controls including the newly proposed blind control system is performed. The conclusions of this paper are shown below.

     1) A method called Meta_simulation was developed to directly replace the airflow rate between zones and infiltration airflow rate in the NewHASP program with the results of the ventilation network program. Using this method, the airflow of the double-skin cavity and the airflow between the blind slats are obtained, and a thermal load simulation is performed.

     2) Derived the formula of double-skin solar heat gain coefficient for double-skin cavity (hereafter DS), blind and double-skin inner glass air layer (hereafter BS), and office room (hereafter RM). Three-space model using NewHASP multi-space calculation is developed.

     3) As a slat control method of the blind installed inside the double-skin cavity, the author proposed two variation of the avoid direct sunlight control. First is to keep the transmittance constant when the avoid direct sunlight angle becomes negative and second is to keep the slat angle constant. The operation curve of the blind control was proposed, and the thermal performance was compared with the conventional control method.

     4) Blind circulation airflow rate on summer peak day was 30 ~ 60m3 / h.m2 and BS air temperature was up to 2K higher than DS air temperature.

     5) When the slat angle is fixed through the year and the slat angle is sequentially increased in increments of 0° to 75° in increments of 15°, the solar shading performance increases as the slat angle is increased from 0° to 45°, and maximum and annual cooling load decreased. However, at slat angles of 60° and 75°, the gap between the slats became narrow, and the ventilation performance between DS / BS was reduced and the cooling load increased.

     6) In the conventional blind avoid direct sunlight angle control, the case where at the night slats were vertical and the case where they were horizontal were compared. Both horizontal and vertical cooling heat loads were reduced when compared to vertical. It is thought that the ventilation performance between DS / BS is promoted when it is horizontal.

     7) As a variation of the blind avoid direct sunlight angle control, the control to keep the transmittance constant when the avoid direct sunlight angle becomes negative and the control to keep the slat angle constant were compared by changing the transmittance and the slat angle. The effect on the maximum / annual cooling load is small. However, it is expected to affect the effectiveness of daylight harvesting systems.

     8) By using the double-skin multi-space model in this paper, if the combination of double-skin structure, solar shading, glass, etc. is changed, it is only necessary to change the double-skin solar heat gain diagram, solar heat gain formula, solar shading, the incident angle characteristic approximation formula of glazing and the blind characteristics. This change can be dealt with only by changing the Excel files, and so it is a model with extremely high flexibility and applicability.

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  • Evaluation of natural ventilation performance applying thermal autonomy
    Kyosuke HIYAMA, Yuichi OMODAKA, Yoshihide YAMAMOTO
    2020 Volume 85 Issue 775 Pages 655-663
    Published: 2020
    Released: September 30, 2020

     Natural ventilation is an essential component in sustainable building designs. However, it remains difficult to incorporate the system successfully because the utilizable amounts of ambient energy resources differ according to project conditions such as ambient climates. Moreover, lack of a quantitative metric that could encourage an architect to design a proper plan and façade for natural ventilation at the schematic design stage is being recognized as a barrier to successful achievement of natural ventilation. An inappropriate architectural plan and façade would make it impossible to make thorough considerations for successful implementation of natural ventilation at the later design stages. To encourage even architects without special expertise in natural ventilation, a simple metric should be utilized to evaluate the achieved design level intuitively and rationally. Against this background, an evaluation method utilizing a simple metric, Thermal Autonomy, is discussed for a passive design integration at an early stage of building design in this paper.

     The practicality of the proposed metric is examined through parametric building energy simulations and analyses. Thermal autonomy is originally defined as “the percent of occupied time over a year where a thermal zone meets or exceeds a given set of thermal comfort acceptability criteria through passive means only.7)” In this definition, ASHRAE -55 Adaptive Comfort Standard is used as the thermal comfort acceptability criteria. However, the standard can be applied to a naturally ventilated building without cooling and heating system. In Japan, the HVAC system is basically installed, then the definition should be modified to adapt this method for building designs in Japan. The averaged lower and upper indoor temperature limits through actual operations among buildings with natural ventilation system, 21C° and 27C°, are used. The results obtained through the case study are as follows:

     • An appropriate ventilation volume, not a plenty of ventilation volume, is necessary to improve the level of thermal autonomy, because excessive heat release due to excessive outdoor air intake could deteriorate the index level. As a result, the method can be utilized to find an appropriate natural ventilation performance, whereas cooling and heating loads for HVAC design can’t be used because it increases in proportion to the ventilation volume.

     • The index can be utilized to find an appropriate operation setting of vent, e.g. a lower outdoor temperature limit, because the deterioration of thermal autonomy can be avoided by adjusting them.

     • Appropriate thermal insulation level can also be evaluated, because it affects the level of thermal autonomy. The higher thermal insulation level can improve the index level, because it can contribute to keep the thermal comfort level within the acceptable range mainly during winter season while the natural ventilation system is not operated. On the other hand, lower insulation level could be the better solutions when heat load alone is used for the evaluation. The lower the insulation level is, the more the heat release through façade occurs during intermediate season. It decreases the cooling load due to excessive internal heat load.

     • As a result, the case study concludes that thermal autonomy is effective to realize a successful natural ventilation implementation, especially at the early stage of building design when natural ventilation plan and thermal insulation level are usually discussed.

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  • Miwako FUJITA, Daisuke NARUMI
    2020 Volume 85 Issue 775 Pages 665-675
    Published: 2020
    Released: September 30, 2020

     From changes in Japan's final energy consumption, the overall increase rate from 1973 to 2013 was 1.2 times, but the increase in business divisions 2.4 times, so that energy saving is required.

     Refrigeration equipment with a high energy consumption density is exposed to cost competition in the food store industry, so that energy-saving equipment is slow to spread. Therefore, it is important to save energy by devising operation and design.

     From the advantage of easy to get products, many open display cases are installed in food stores. The open display case maintains the internal temperature with the air curtain, but from a part of the air curtain cold air in the refrigerator leaks from the display case and the surrounding air enters the display case. Leaked cold air stays in the lower part of the store, affects the air enthalpy in the store and worsen comfort. At the same time, air enthalpy entering display case affects the display case refrigeration load. For these reasons, the load of the open type display case interacts with the space conditioning load, making it difficult to consider energy saving.

     In this study, we will devise a method to give the enthalpy of the intrusion air into the SC considering the amount of heat leaked from the SC. The SC refrigeration load is calculated by combining the enthalpy of the air entering the SC and various SC characteristics obtained from the experiment. Furthermore, by combining with air conditioning load calculation, store air conditioning, ventilation, and SC energy consumption are calculated, and the impact of various energy saving measures on store energy consumption is clarified.

     In this report (1st report), two types of refrigerated temperature zones(multi-deck (MD (RE)) and semi-multi-deck (SMD (RE))) and three types of freezing temperature zones (multi-deck (MD (FR)) and flat tub (TUB (FR)) and glass door attachment (RI (FR))) were tested, and The enthalpy characteristic formula of total heat and latent heat was obtained. And we were able to confirm the following:

     1. The refrigeration load of SMD (RE) is about 30% larger than MD (RE). However, there is no difference in the SHF characteristics, and the enthalpy of the laboratory is close to 1.0 at 30 kJ/kg, and it decreases to 0.6 at the laboratory enthalpy of 60 kJ/kg.

     2. MD (FR) SHF increased due to low SC pre-set temperature, and exceeded 0.8. The change in refrigeration load is small compared to the refrigeration temperature range, but the amount of change in refrigeration load relative to enthalpy is about 20% larger than MD (RE).

     3. The TUB (FR) / RI (FR) SHF was high due to the low pre-set temperature of the SC, and it was close to 1.0 even at high enthalpies due to the small amount of air in the store. The amount of change in enthalpy of the refrigeration load is very small.

     4. The cold heat leaked from the SC causes a large vertical temperature distribution in the store. Under this experimental condition, the temperature decreased from about FL 2.0m. This coincides with the increase in the amount of leakage heat when the ambient temperature is high. When calculating the mutual influence of air conditioning load and SC load, it is necessary to consider such vertical temperature and humidity distribution.

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  • Masato OOTA, Yumiko IWAFUNE, Ryozo OOKA
    2020 Volume 85 Issue 775 Pages 677-683
    Published: 2020
    Released: September 30, 2020

     We have been studying home energy consumption using data from Home Energy Management System since 2011. In this paper HEMS data of about 50,000 houses were collected and analyzed. We clarified the composition of HEMS data. It turns out that the energy consumption is decreasing as the buildings are newer. We further analyze energy consumption by appliances. The purpose is to promote energy saving of new houses and existing houses

     Energy consumption ratio in the household sector has not stopped the increase trend of 26.5% in 1990 to 30.4% in 2016. The data acquired by HEMS includes total energy consumption, usage, equipment, power generation, storage battery charge / discharge, electric vehicle energy, construction site, construction year, floor area, and family composition. The average floor area of the investigated houses is 121 square meters. This is almost equal to the average floor area of Japanese houses.

     The total energy consumption was analyzed. Compared to 2011, the reduction is about 30% in 2017. We analyzed consumer electronics, ventilation, and lighting energy consumption. Since 2011, type 1 ventilation system has a 20% greater consumption than type 3 ventilation. But in 2017 it is equivalent. This is thought to be due to an improvement in the efficiency of a kind of ventilation. It was found that consumption was reduced by about 50%. The reason is presumed to be high efficiency of home appliances and LED lighting, This will need to be clarified in future research.

     The annual energy consumption of ventilation has been half from about 1200kWh to about 600kWh. That of refrigerators have been reduced by about 30% from 560kWh to about 400kWh. In 2017, The power consumption of TV and video equipment was about 520kWh. 3 years energy savings is only about 5%. The next biggest influence is the total consumption of kitchen appliances (IH heaters, microwave ovens) about 500kWh even in 2017. IH heaters are about 20% more energy efficient, but other home appliances are less energy efficient. The energy consumption of toilet, living room lighting, and sanitary are about 300kWh in total and there is little impact on the whole, but energy saving is progressing reliably by about 30-40%

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  • Reina OKI, Takaomi OGAWA, Shin-ichi TANABE
    2020 Volume 85 Issue 775 Pages 685-694
    Published: 2020
    Released: September 30, 2020

     The purpose of this study is to investigate the energy consumption, power supply and demand of all-electrified net Zero Energy Houses (ZEHs). Energy measurement data of 67 all-electrified ZEHs was analyzed based on a nationwide survey conducted from 2018 to 2019. The primary energy consumption of all-electrified ZEHs was described in comparison with conventional houses. By analyzing the self-consumption rate, the self-sufficient rate, the amount of sales and purchase power, and the charging and discharging of storage batteries, the circumstances of power supply and demand of the all-electrified ZEHs were discussed.

     The following conclusions are obtained in this article.

     1) The average annual primary energy consumption of all-electrified ZEHs was 56.5 GJ, which was about 0.9 times that of conventional houses in 2003. Sum of air conditioning and ventilation energy, and hot water supply energy of all-electrified ZEHs decreased compared to conventional houses in 2003, but other energies such as that of home appliances increased 1.8 times and accounted for about half the total energy. Moreover, sum of lighting and home appliance energy increased about 2.0 times compared to the conventional houses in 2017, suggesting that energy saving measures for home appliances are highly required.

     2) In comparison with the design values, the actual measurement values of air conditioning, ventilation, hot water supply and lighting energy decreased, but that of home appliance energy increased. Additionally, all all-electrified ZEHs achieved net zero energy when excluding home appliance energy, whereas about 20% of the all-electrified ZEHs did not achieve net zero energy when including home appliance energy during the operation stage.

     3) The air conditioning and ventilation energy consumption of all-electrified ZEHs was higher in summer but lower in winter compared to the conventional houses. It can be inferred that the use of air conditioners in summer increased in all-electrified ZEHs. Moreover, the heating energy consumption of all-electrified ZEHs in winter was reduced because of the improvement in thermal insulation performance and efficiency of heating equipment.

     4) Water heaters (CO2 Heat Pump) were operated during nighttime in most of the all-electrified ZEHs. To improve the self-consumption rate with the sequential completion of the feed-in tariff system, it is necessary to consider daytime operation of water heaters.

     5) The average self-consumption rate of all all-electrified ZEHs was 22.4%. There was no particular trend regarding the presence or absence of storage batteries on the self-consumption rate, suggesting that all-electrified ZEHs currently use the feed-in tariff system and are operated with profit as the objective, obtained by selling more electricity. To improve the self-consumption rate, it will be necessary to establish the definition and set requirements of the self-consumption rate, and clearly present benefits to the residents.

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  • Changes in graduate students' power operation of automated office equipment by information provision
    Keisuke OJIMA, Jongyeon LIM, Yasunori AKASHI, Jiawei CHEN, Naoki YOSHI ...
    2020 Volume 85 Issue 775 Pages 695-704
    Published: 2020
    Released: September 30, 2020

     It is important to not only improve the performance of the building envelope and the efficiency of the equipment system but also to focus on occupants’ behavior to further promote energy conservation in buildings. In fact, the method called “Nudge, ” which has been applied in the field of behavioral science, is attracting attention as an energy-saving measure for buildings. Nudge is a system that alters people’s behavior in a predictable way without forbidding any options or significantly changing their economic incentives. Through information provision using Nudge, people can be encouraged to change their behavior to save energy.

     In a large-scale experiment conducted in the US, the electricity consumption of households was reduced by approximately 2% on average as a result of providing information on electricity consumption compared with that of neighborhoods. It is thought that energy-saving behaviors are likely to occur because those behaviors directly lead to economic benefits for households. On the other hand, in public spaces such as offices and schools, the energy-saving effects may differ because occupants do not directly pay for utilities. In order to encourage energy conservation, it is important to promote initiatives that utilize information provision in office spaces. For this purpose, the impact of information provision on public spaces need to be verified, and the necessity of applying such measures must be clarified.

     In previous research on occupants’ behavior, there are some examples in which the probability that occupants perform actions such as switching off lights and opening windows is modeled by logistic regression analysis. However, there are few examples on modeling the operation of automated office equipment. For further energy conservation, it is important to reduce wasteful consumption such as forgetting to turn off equipment upon leaving.

     This paper proposes a method to model the operation of office equipment. Moreover, the energy-saving effects of information provision are evaluated using the model. The model was created by logistic regression analysis, and the data to determine the model parameters was obtained through an information provision experiment. The experiment was conducted in a laboratory as an example of a working space. In this paper, therefore, the operation of equipment by graduate students was modeled.

     Modeling made it possible to calculate each subject’s probability of turning off the PC and Display when leaving the room using absent time as an explanatory variable. The degree to which behavioral change was caused by information provision varied greatly between subjects, and the results were not always positive. A simulation using the model showed that approximately 70% reduction in energy consumption could be achieved if all occupants changed their behavior as a result of information provision. However, considering the variations in the degree of behavioral change, it was possible to estimate that the total electricity consumption of the entire building could be reduced by several percent.

     The proposed modeling method is expected to make it easier to grasp the characteristics of occupants’ behavior with regard to equipment operation, and contribute to strategic planning for information provision. In the future, a model will be developed that considers the fact that some people will not change their behavior even if information is provided. This is expected to improve the accuracy of predicting information provision effects by simulation.

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