Comfort Zone Or Acceptable Comfort Zone? : Comparison of Resident Behavior of Operating Air Conditioner According to Charge for Energy

Transcription

1 Comfort Zone Or Acceptable Comfort Zone? : Comparison of Resident Behavior of Operating Air Conditioner According to Charge for Energy Suh-hyun Kwon, Nu-ri Bae, Chi-hye Bae and Chungyoon Chun Yonsei University, Korea Corresponding amy611@hanmail.net SUMMARY This research compared two groups operation behavior of cooler, one is the resident of studio apartment who pays their energy charge per month, and the other is the resident of university dormitory who doesn t pay energy charge beside their rental fee. The amount of time to use a cooler and room temperatures were measured when they turn on/off air conditioner. Residents were interviewed about their cooling needs and decision factor on their operation behavior. Main results are as follows. 1. Dormitory group used the air-conditioner twice as much as studio apartment group. 2. Dormitory group turned on/off air-conditioner at lower temperature compare to the studio apartment group. 3. Studio apartment group s acceptable comfort zone was in or higher than ASHRAE summer comfort zone, but dormitory group s that is in or lower than ASHARAE comfort zone. INTRODUCTION Building systems have been developed and complicated, and it follows the energy which is consumed for the building is extending too. In a life cycle of the building, most using much energy is a dwelling phase. Big effects to these energy consumptions in a dwelling phase are the behavior and attitude of residents, and energy charge affects to these residents behavior and attitude. Consequently, we can assume that there would be a big difference between the residents who pay for the energy or not; house and office. Meanwhile, the electric consumption in Korea was increased 4 times much as 20 years before. Big parts of these residential energy consumptions are consent, lighting and cooling. Especially, cooling demand is expected to increase fast. On this background, this research compared two groups operation behavior of cooler according to charge for energy. METHODS Thermal environment and using time of air conditioner are measured in seven studioapartments and eight rooms in university dormitory where air conditioners were located. Measurement was conducted during 9 days from August 13 th to 22 nd in Subjects were selected to twenties who can operate air conditioner well and were limited to independent resident for restricting effects from other generations. We do an experiment in two groups operation behavior of cooler; one is the residents who pay their energy charge per month, and the other is the residents of university dormitory who doesn t pay energy charge beside their rental fee. This is for finding out whether charging for energy has effect on using time of air conditioner. Air temperature and relative humidity were measured at 110cm high from the floor and air temperature blowing from air conditioner was also measured to detect the

2 condition of on/off of air conditioner. Air temperature, relative humidity, and air temperature blowing from the air conditioner are measured with RH-temperature data logger. Interviews were also conducted to investigate characteristics of residents behaviors of operating air conditioner in addition to physical environment; time of staying at home, a way they operate air conditioner, a purpose that they use air conditioner, their Clo value, sex, age, kinds of AC, and spending electric power. RESULTS Outdoor temperature and relative humidity Outdoor weather data was obtained form Korea Meteorological Administration. The mean outdoor temperature was and relative humidity was 67% during experiment period Outdoor Air Temperature 100 Relative Humidity 80 Ta( ) RH(%) /14 8/15 8/16 8/17 8/18 8/19 8/20 8/20 8/21 Date a) Outdoor air temperature Figure 1. Climate during experiment periods 20 8/14 8/15 8/16 8/17 8/18 8/19 8/20 8/20 8/21 Date b) Relative humidity Comparison on the amount of time to use an air conditioner between two groups Table1 shows that the results of the time used with air conditioner for two groups. The dormitory group used air conditioner twice as much as the studio-apartment group: Dormitory group spend 43hours 55minutes and studio-apartment group spend 23hours 21minutes in the experiment period. All of the residents in two groups were university students or graduate students. Although considering their life style was similar, we calculated index of amount of time to use an air conditioner to more accurate analysis. The method of calculating of index was that amount of time to use an air conditioner divided by mean time for which residents stayed at home. As the result, index of dormitory (0.4) was higher than that of studio apartment (0.17). Even though, we excluded A-6 and A-7 that never used air conditioner during experiment period from a calculating, index of studio apartment became 0.24 to be still lower than dormitory. It was one of the reasons that residents even maintained running air conditioner when they went out for thermal comfort to come back. While, when going out, residents of studio apartment always turned off their air conditioner. A-3 of studio apartment group was the highest both time of use and index of time, because this one stayed at home by far than others. Most of studio apartment except A-3 was lower than dormitory in index of time. Also, despite of high temperature of outdoor, A-6 and A-7 never turned on air conditioner because of charge for energy.

3 Table 1. Operating time of air conditioner. Studio-apartment Dormitory Resident Operating time Index Operating time Index Resident (hour, minute) of operating time (hour, minute) of operating time A-1 29h 8m 0.29 B-1 49h 24m 0.50 A-2 10h 36m 0.10 B-2 45h 58m 0.46 A-3 64h 4m 0.44 B-3 73h 0.50 A-4 40h 40m 0.28 B-4 54h 52m 0.38 A-5 18h 8m 0.08 B-5 37h 0.37 A-6 0m 0 B-6 31h 32m 0.31 A-7 0m 0 B-7 33h 20m 0.37 B-8 26h 16m 0.27 Avg. 23h 21m 0.17 Avg. 43h 55m 0.40 * Index of operating time = Operating time of air conditioner / inhabitant time Indoor Thermal Environment when residents operate air conditioner There was a gap between two groups about mean temperature at the point time that air conditioner turned on or off. Table 2 shows that indoor air temperature fight at the point time that residents turn on air conditioner and turn them off. It appeared that residents of the studio apartment start air conditioner at 29.9 of air temperature, and switch off at While, residents of the dormitory turn on air conditioner at 27.0, and turn off at It means that residents of studio apartment turn on and off at higher temperature than residents of dormitory. Like above these results, we know that the dormitory group not to charge for energy used air conditioner in lower temperature than the studio apartment group to charge for energy. Table 2. Mean indoor air temperature when AC was turned on or off. Studio-apartment Dormitory Resident On( ) Off( ) Resident On( ) Off( ) A B A B A B A B A B A-6 Never used B A-7 Never used B B Avg Avg Interview of resident cooling behavior Interview was conducted to help understanding about residents behavior of operating air conditioner. When asked whether residents still remain air conditioner turn on for going out, more than 50 percent of the dormitory residents blamed yes, but all of the studio apartment residents answered no. Setting temperature of air conditioner in both groups was similar, 20. They controlled indoor temperature by switch on and off, not the setting temperature. The main reason why they turn on air conditioner is high temperature, the other is to exsiccate. Also, it seems that their habituation of operating air conditioner is only to turn on or off cooler

4 than to regulate. When they ho to sleeping, all in both groups stopped cooler and opened windows, but only one in the dormitory remained cooler running beside opening windows. Indoor mean Clo value of the studio apartment group was higher rather than the dormitory group: the studio apartment group was 0.15 clo and the dormitory group was 0.24 clo. When asked How much could you pay for using air conditioner?, they answered each 34 dollars on the dormitory and 70 dollars on the studio apartment. It means that residents of the studio apartment who pay for energy have more recognition than them of the dormitory. Comparison with a previous research We compared this result with previous research, which was studied from Nu-Ri Bae for finding out resident operating behavior of air conditioner according family members as well as charge for energy.[1] The previous research was conducted during 60days from July 3 rd to August 31 st in 2004 in six family apartments living rooms there air conditioner were located. Indoor thermal environment was measured and air temperature blowing from air conditioner was also measured to find out the condition of on/off of air conditioner. Mean outdoor temperature was 25.2 and relative humidity was 76.5% in experiment period. 1. Thermal environment of three groups In Figure 2~ 4 thermal environments at the point time air conditioner was started and was stopped in three groups compared with thermal comfort range of ASHRAE Standard 55. [2] First of all, compared with thermal environment according charge for energy, three groups have a clear distinction. Figure 2 shows that the result of studio apartment group. When residents started air conditioner, most cases of thermal environment were on very high temperature that is not contained ASHRAE comfort zone and when air conditioner was stopped, some cases was covered or accessed ASHRAE comfort zone of summer. Also, Figure 4 indicated that family apartment was as same as studio apartment but was rather high range. An air conditioner was started and switched off at thermal range that was not included ASHRAE comfort zone. On the other hand, Figure 3 displayed that residents behavior of the dormitory was different from other two groups. They turned on air conditioner at air temperature whose one third already was included on summer comfort zone of ASHRAE and turned off it at air temperature whose most was contained on lower air temperature, winter comfort zone, as well as summer comfort zone of ASHRAE. It means that range of thermal environment which residents controlled was significantly different according charge for energy. Judging from air temperature, residents can use air conditioner on very low air temperature in case of no charging for energy. From interview, there are some responses that residents still keep cooler in running until feeling cold and wear more clothes instead of stopping cooler.

5 a) Thermal range when AC was turned on b) Thermal range when AC was turned off Figure 2. apartment Indoor thermal range on ASHRAE comfort zone when AC operated in studio a) Thermal range when AC was turned on b) Thermal range when AC was turned off Figure 3. Indoor thermal range on ASHRAE comfort zone when AC operated in dormitory a) Thermal range when AC was turned on b) Thermal range when AC was turned off Figure 4. Indoor thermal range on ASHRAE comfort zone when AC operated in family apartment

6 2. Prediction of time to use air conditioner What effect will outdoor weather factors including mean temperature, highest temperature, lowest temperature, mean relative humidity and highest wind velocity have on time to use air conditioner? The relationship between outdoor weather factor and using time was calculated by linear regression model. As a result, the relationship with both mean temperature and highest temperature is the strongest in the family apartment, the relationship with lowest temperature is the strongest in the dormitory and the relationship with both highest temperature and lowest temperature is the strongest in the studio apartment. It is appeared that residents of the family apartment start air conditioner when outdoor temperatures getting hotter but residents of the dormitory turn off it when weather become colder. In other words, residents in family apartment don t use air conditioner usually and then start it when air temperature reach the maximum, but the residents in dormitory use air conditioner always and then they switch off it when air temperature go down. Table 3. Correlation coefficient between outdoor weather and time of using AC Weather factor Studio apartment Dormitory Family apartment R R R Mean outdoor air temperature Highest outdoor air temperature Lowest outdoor air temperature Mean relative humidity Highest wind velocity 1E Using time of air conditioner of each group was predicted through regression model with mean outdoor temperature that is related in all groups comparatively high. 26 and 30 of outdoor air temperature were applied to regression model, and mean using time of each group was calculated. Showing fig. 6, the dormitory has each value of 319 minutes and 540minutes, the studio apartment has each value of 222minutes and 364minutes and the family apartment has value of 119mimutes and 202minutes. From this graph, we can see the order of using time of air conditioner in same outdoor temperature is Dormitory, Studio apartment, and Family apartment. And an angle of inclination by temperature increasing shows same order. The reason why residents of the family apartment use less time compared with studio apartment could be from generation gap about energy saving and charging for energy, different thermal sensation between ages, and housewife economical conception, etc Apartment Studio Apartment Dormitory Time(min) Room Temperature( ) Figure 5. Predicted AC using time by outdoor air temperature

7 DISCUSSION When people turn off air conditioner, which means room air temperature became cool enough to them. This enough cool temperature was different between three groups. Of course, it is because of economical factor. Thermal comfort zone like ASHRAE Std.55 is based on sensory comfort in climate chamber. It was calculated from experiment results in climate chamber. Subjects didn t get the influence from economical factor, and tried to find out just comfortable temperature. If we call this just comfortable temperature as sensory comfort zone, we can call acceptable comfort zone in this study as cognitive comfort zone. Sensory comfort zone is related on human sensory system physiological & physical characteristics. Cognitive comfort gets the influence from many factors economical situation, thermal history, adaptation state, etc. These differences made the difference between many chamber study results and field study results. In ordinary, field study results show wider acceptable range than chamber study results. This tendency respected to the revise of ASHRAE Std. 55 (2004). Both of them Sensory & Cognitive Comfort are necessary and worth. However, broad acceptable range may be desirable in point of human thermal adaptation and environment of the earth. REFERENCES 1. Nu-ri Bae A study on acceptable thermal comfort zone and resident behavior of operating cooling devices in apartment. Proceedings of Healthy buildings. 2. ASHRAE ANSI/ASHRAE Standard , Thermal Environmental Conditions for Human Occupancy, Atlanta: American Society of Heating, Refrigerating, and Air conditioning Engineers, Inc. 3. Busch, J.F A tale of two populations: thermal comfort in air-conditioned and naturally ventilated offices in Thailand. Energy and Buildings. 18: Cena, K.M. Thermal and non-thermal aspects of comfort surveys in homes and offices. in Thermal comfort: Past, Present and Future, ed. by N.A. Oseland and M.A. Humphreys Garston: Building Research Establishment de Dear, R. and A. Auliciems Air-conditioning in Australia Ⅱ - User Attitudes. Architectural Science Review, 31: de Dear, G.J. and M.E. Fountain Field experiments on occupant comfort and office thermal environments in a hot-humid climate, ASHRAE Transactions, 100(2): de Dear, R.J. and G.S. Brager Thermal comfort in naturally ventilated buildings: revisions to ASHRAE Standard 55, Energy and Buildings, 34: 549: ISO. ISO Ergonomics of the Thermal Environment-Analytical determination and interpretation of the PMV and PPD indices and local thermal comfort criteria. Geneva: International Organization for Standardization. 9. Meyer, W.B Why indoor climates change: a case study, Climatic Change, 55: Parsons, K.C The effects of gender, acclimation state, the opportunity to adjust clothing and physical disability on requirements for thermal comfort, Energy and Buildings, 34: Raja, I.A., J.F. Nicol, K.J. McCartney and M.A. Humphreys Thermal comfort: use of controls in naturally ventilated buildings, Energy and Buildings, 33: