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Impact of Air-Side Economizer Control Considering Air Quality Index on Variable Air Volume System Performance

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Impact of Air-Side Economizer Control Considering Air Quality Index on Variable Air Volume System Performance ctbuh.org/papers Title: Impact of Air-side Economizer Control Considering Air Quality Index on Variable Air Volume System Performance Authors: Sang-Hyeon Cho, Department of Architectural Engineering, Hanyang University Joon-Young Park, Department of Architectural Engineering, Hanyang University Jae-Weon Jeong, Department of Architectural Engineering, Hanyang University Subject: Architectural/Design Keywords: Environment Structural Health Monitoring Publication Date: 2017 Original Publication: International Journal of High-Rise Buildings Volume 6 Number 1 Paper Type: 1. Book chapter/Part chapter 2. Journal paper 3. Conference proceeding 4. Unpublished conference paper 5. Magazine article 6. Unpublished © Council on Tall Buildings and Urban Habitat / Sang-Hyeon Cho; Joon-Young Park; Jae-Weon Jeong International Journal of High-Rise Buildings International Journal of March 2017, Vol 6, No 1, 101-111 High-Rise Buildings https://doi.org/10.21022/IJHRB.2017.6.1.101 www.ctbuh-korea.org/ijhrb/index.php Impact of Air-side Economizer Control Considering Air Quality Index on Variable Air Volume System Performance Sang-Hyeon Cho, Joon-Young Park, and Jae-Weon Jeong† Department of Architectural Engineering, College of Engineeing, Hanyang Univeristy, Seoul 04763, Korea Abstract The objective of this study is to determine the effectiveness of a modified air-side economizer in improving indoor air quality (IAQ). An air-side economizer, which uses all outdoor air for cooling, affects the building’s IAQ depending on the outside air quality and can significantly affect the occupants’ health, leading to respiratory and heart disease. The Air Quality Index (AQI), developed by the US Environmental Protection Agency (US EPA), measures air contaminants that adversely affect human beings: PM10, PM2.5, SO2, NO2, O3, and CO. In this study, AQI is applied as a control for the operation of an air-side economizer. The simulation is analyzed, comparing the results between the differential enthalpy economizer and AQI–modified economizer. The results confirm that an AQI–modified economizer has a positive effect on IAQ. Compared to the operating differential enthalpy economizer, energy increase in an operating AQI–modified economizer is 0.65% in Shanghai and 0.8% in Seoul. Keywords: Air-side economizer, AQI-modified economizer, Indoor air quality, Air quality index, PM2.5 1. Introduction lained that people with asthma and fourth and fifth grade students experienced a decrease in pulmonary function of Big cities in China generally exceed PRC pollution up to 6% compared to normal conditions when PM10 standards for 10% to 30% of the day (Chan and Yao, exceeded 150 µg/m³. 2008), and 20.7% of China’s cities exceed Grade II of the An air-side economizer, which uses only outdoor air for National Standard of China (Zhang and Rock, 2012). cooling, has the advantage of reducing the energy needed Globally, most big cities face air pollution problems, to run a HVAC system (Park et al., 2013). Aktacir (2012) including Shanghai and Beijing in China and Seoul in researched monthly energy saving effect of air-side econ- South Korea. The poor air quality adversely affects human omizer in Antalya, Turky. In this energy simulation, three health, even indoors through HVAC systems. Schwartz HVAC system operation, which are air-conditioning with and Dockery (1992) reported that each increase of 100 no air-side economizer, differential enthalpy economizer µg/m³ in total suspended particulates (TSP) increases and differential dry-bulb temperature economizer, are mortality by 7%. Every 100 µg/m³ increase in TSP inc- used to verify the energy consumption differences. The reases mortality by 10% among people over 65 and 3% results showed the energy saving effects were the greatest among people under 65. In addition, a 10 µg/m³ increase in March and April. Specifically, 55% and 66% energy in PM2.5 increases mortality related to respiratory illness were saved in each operation of differential dry-bulb eco- by 1.78%, related to stroke by 1.03%, and for all-cause nomizer and differential enthalpy economizer in March. mortality by 1.21% (Frankin et al., 2007). Linares and 40% and 43% of energy were saved in each operation of Diaz (2010) researched the relationship between PM2.5 differential dry-bulb economizer and differential enthalpy concentrations and hospital admissions using hospital economizer in April. Yao and Wang (2010) analyzed dif- data from 2003 to 2005 in Madrid, Spain. It shows that ferential dry-bulb temperature/enthalpy economizer eff- PM2.5 concentration and hospital admissions have a linear ects in various climate zone of China. The selected reg- relationship with no threshold. Every 10 µg/m³ increase ions are Shenyang, Beijing, Xian, Chengdu, Shanghai, in PM2.5 raises mortality from diabetes mellitus by 11% Guangzhou. Operating differential dry-bulb saved more (O’Donnell et al., 2011), significantly influences indoor energy than operating differential enthalpy economizer in allergens (Maesano et al., 2007), and reduces heart rate the northern region cities including Shenyang, Beijing variability (Rodriguez et al., 2006). Pope et al. (2015) exp- and Xian. Otherwise in southern region cities, operating differential enthalpy economizer saved more energy. Com- †Corresponding author: Jae-Weon Jeong paring the two regions, operation in southern region cities Tel: +82-2-2220-2370; Fax: +82-2-2220-1945 saved more energy than operation in northern region E-mail: [email protected] cities due to the longer cooling period. LEE and Chen 102 Sang-Hyeon Cho et al. | International Journal of High-Rise Buildings (2013) analyzed how differential enthalpy economizer operation. One is that IAQ is improved by the air-side affects energy saving in 17 different climate zone when economizer ceasing to operate during times of bad air indoor set temperature is 27oC. In Climate zone 4A (mixed- quality, even if the weather is suitable to operate the air- humid) 33% of energy consumption decreased and in side economizer. The other is that chiller energy consump- Climate zone 3C (warm-marine) 32% of energy consump- tion increases compared to DEE because cooler outdoor tion decreased. As indicated above, air-side economizer air may not be able to be used; hence, the chiller must be has an effect on saving the cooling energy in HVAC system. operated to maintain a set indoor temperature. However, outdoor air is not always clean so that oper- To verify the effects of AME use, two simulations of ating an air-side economizer can cause problems because DEE and AME operation were conducted. Indoor conta- all the contaminants in the outdoor air enter the building minant concentration was calculated by Eq. (1) in the sim- space (Elkilani and Bouhamra, 2001). For this reason, the ulation (Noh and Hwang, 2010). To confirm how energy aim of this research is to suggest how to consider outdoor consumption increases when operating an AME, an energy air quality in use of an air-side economizer. simulation including chiller, pump, and fan was also con- ducted for each case. 1.1 Methodology dC · In this research, Air Quality Index (AQI) is introduced V---------in- = {}ε ⋅()C –C +C ⋅{}ε ⋅⋅Q ()1–ε dt CCI in SA SA AEE SA f as a control to operate the air-side economizer. The AQI (1) suggested by the US Environmental Protection Agency · · · · · +COA⋅⋅QI P–Cin()εAEE⋅QSA++QI β ⋅V +S (US EPA) rates outdoor air pollution levels on a scale from 0 to 500, and will be described further in the next where section. The suggested method is that the air-side V = volume of room (m3) 3 economizer is stopped when the AQI exceeds 100, which Cin = indoor contaminant concentration (µg/m ) 3 is labeled “Unhealthy for sensitive groups.” This metho- CSA = contaminant concentration of supply air (µg/m ) 3 dology is depicted in Fig. 1, which describes conventional COA = contaminant concentration of outdoor air (µg/m ) · 3 differential enthalpy economizer (DEE) and AQI-modified QSA = volume flow rates of supply air (m /min) · 3 economizer (AME) operation algorithms. In Fig. 1(b), the QI = volume flow rates of infiltration (m /min) added condition for activating the air-side economizer P = the penetration efficiency of particles through the differs in two aspects between AME operation and DEE air infiltration (-) Figure 1. Air-side economizer algorithm. Impact of Air-side Economizer Control Considering Air Quality Index on Variable Air Volume System Performance 103 Figure 2. Mass balance model schematic. εCCI = the cross contamination index around the exterior where air vent (-) Ip = the index for pollutant P (AQIP) εAEE = efficiency of air exchange effectiveness (-) Cp = the rounded concentration of pollutant P εf = filter efficiency (-) BPHi = the breaking point that is greatest than or equal · 3 S = emission rate of PM2.5 in room (µg/m ) to Cp -1 β = deposition rate of particles onto surfaces (h ) BPLo = the breaking point that is less than or equal to Cp IHi = the AQI value corresponding to BPHi In simulating those cases, filters were also added. Filters ILo = the AQI value corresponding to BPLo states ranged from Minimum Efficiency Reporting Value (MERV) 8 to MERV 16, and the absence of a filter was In Eq. (2), the Guidelines for the Reporting of Daily also considered. Air Quality - the Air Quality Index (Park, 2006) regulates BPHi, BPLo, IHi, and ILo. The highest AQI calculated by 1.2. Air Quality Index each pollutant indicates air quality using the value scale The AQI is calculated for six contaminants that adver- presented in Table 1 (Park, 2006): From 0 to 50, air qua- sely affect human health: PM2.5, PM10, ozone, carbon lity is “Good,” from 51 to 100 air quality is “Moderate,” monoxide, nitrogen dioxide, and sulfur dioxide. Each from 101 to 150 air quality is “Unhealthy for Sensitive AQI contaminant is calculated as in Eq.
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