Investigations of life cycle climate performance and material life cycle assessment of packaged air conditioners for residential application

Sustainable Energy Technologies and Assessments 11 (2015) 114–125

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Sustainable Energy Technologies and Assessments journal homepage: www.elsevier.com/locate/seta

Original Research Article

Investigations of life cycle climate performance and material life cycle assessment of packaged air conditioners for residential application Gang Li Ingersoll Rand Residential Solutions, 6200 Troup Highway, Tyler, TX 75707, USA Ingersoll Rand Engineering and Technology Center-Asia Pacific, Shanghai 200051, PR China

a r t i c l e

i n f o

Article history: Received 19 May 2015 Revised 14 July 2015 Accepted 16 July 2015

Keywords: Life cycle climate performance Life cycle assessment Packaged Air conditioner Material Seasonal energy efficiency ratio

a b s t r a c t A comprehensive investigation for life cycle climate performance (LCCP) and material life cycle assessment (LCA) is performed under various influencing factors for the packaged conditioners. The whole carbon dioxide equivalent (CO2-eq.) emissions during an air conditioner’s lifetime are evaluated from the LCCP aspect. Results indicate that the seasonal energy efficiency ratio (SEER) rating has a large influence on the emission variation, 13 SEER R410A has approximately a +3% CO2-eq. emission increase when compared with the 13 SEER R22 in the area of Richmond, which is mainly caused by the direct emission of annual leakage of high GWP R410A. The efficient 14 SEER R410A unit depicts a 9% reduction. In general, as the climate is varied from cold to hot, the emissions are increased. Among the emission contributors, the energy consumption accounts for more than 70% of the total emissions, followed by annual refrigerant leakage. Parameter analysis reveals that the refrigerant recovery rate has a larger effect on the LCCP results than the cycle degradation coefficient, especially in the cold areas. In addition, the two capacity air conditioner product has approximately a 13% emission reduction due to the better load matching. Material LCA investigation shows that, in general, most of the material phase environmental performance is decreased in 14 SEER air conditioners. This is because the addition of aluminum from employing of the micro-channel heat exchanger. For a sustainable future, minimizing material use and CO2-eq. emissions and maximizing energy efficiency should have been considered in its entirety. Ó 2015 Elsevier Ltd. All rights reserved.

Introduction Sustainability has become an alarming concern by increasing the awareness that there are limits to the availability of non-renewable resources, and there is the rising energy demand, especially in the area of heating, ventilating, air-conditioning and refrigeration (HVAC&R). To achieve a more sustainable future for products in various applications, both the research institutes and industry are taking more efforts to evaluate the environmental burdens with various products. Based on the U.S. Department of Energy (US DOE) [1], appropriately 70% of the households make use of the central air-conditioning systems run by a conventional external condenser or a heat pump. Therefore, the heating or cooling systems/products in the buildings deserve the further investigation to achieve better environmental impact. From the environmentally life-cycle perspective, a manufacturer is usually further challenged with strict design requirements, such as long operational life, maximizing the energy efficiency, maximizing the recyclable content, and minimizing the material use and CO2 E-mail address: [email protected] http://dx.doi.org/10.1016/j.seta.2015.07.002 2213-1388/Ó 2015 Elsevier Ltd. All rights reserved.

emissions, etc., to provide the most competitive products for the application. Currently there are limited studies regarding the in-depth environmental impact of residential buildings for cooling or heating systems/products. One study [2] was performed for the life-cycle energy, greenhouse gas emissions, and costs of a contemporary 2450 sq ft (228 m3) U.S. residential home (the standard home, or SH). A functionally equivalent energy-efficient house (EEH) was modeled that incorporated 11 energy efficiency strategies. These strategies led to a dramatic reduction in the EEH total life-cycle energy; 6400 GJ for the EEH compared to 16,000 GJ for the SH. Life-cycle greenhouse gas emissions were 1010 metric tons CO2 equivalent for an SH and 370 metric tons for an EEH. However, the estimated operating inputs such as the electricity for products are directly mapped into model sectors for calculation without considering various operating conditions under different climates for the air conditioners and heat pumps. A study by Heikkilä [3] compares the life cycle environmental impacts of two air-conditioning systems for an office building in Sweden. The difference in the form and source of the energy dominates the relative environmental effects of the systems. Another study

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G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

Nomenclature AHRI AP COP EEH GHG SEER SFP

air-conditioning, heating, and refrigeration institute acidification potential coefficient of performance energy efficient house greenhouse gas seasonal energy efficiency ratio smog formation potential

by Ochoa et al. [4] was conducted for the environmental impact for improving a single family house and outlined a simple approach to a life cycle analysis for residences. However, the following two studies did not consider the effect of climate for products as well, and this study by Ochoa et al. [4] was admitted their study was limited in the life cycle assessment to the building environmental impacts. There are many other similar studies. Therefore, based on the literature review, there are few, limited in scope, and fragmented investigations with in-depth analysis for the environmental impact including the climate effect for residential applications. To reveal the in-depth analysis, some powerful and necessary tools evaluating the product environmental performance or impact are briefly introduced here. One tool for is the web-based interactive life cycle climate performance (LCCP) modeling program for residential heat pumps and air conditioners from reference [5]. LCCP is a methodology that is used to assess the total global warming potential (GWP) impacts (both direct and indirect emissions), expressed as carbon dioxide equivalent mass (kg-CO2 eq.), over the lifetime of a particular refrigerant, piece of equipment or system with different climate inputs. It can be expressed as a summation of all sources of the direct and indirect source emissions. This tool has the detailed input parameters for the use phase, including various operating conditions based on ANSI/AHRI Standard 210/240 [6] with different climate conditions, cycle degradation coefficient, various cities, etc. It will calculate the equivalent mass of CO2 released into the atmosphere for different air conditioner types. As mentioned before, there are few investigations that do a complete and comprehensive work with covering one product area in detail comparing various influencing parameters to achieve the lowest environmental impact. Therefore, in the current study, the LCCP investigation is performed comprehensively, from both the direct and indirect emission aspects for the packaged 14 SEER air conditioners. In addition, there is a lack of material life cycle assessment (LCA) analysis for the latest HVAC&R products based on the recent component update from various environmental impacts from the literature review. Here the Ingersoll Rand’s (IR) Screening LCA tool, which is followed the ISO 14000 series standards [7–10], managed by PE, is used to evaluate the potential environmental impacts from the material phase. Therefore, in the current study the LCCP is used efficiently to evaluate the environmental impact of the packaged air conditioners from a whole life cycle aspect, including both the direct and indirect emissions. LCA tool can be efficiently utilized for the material phase during the material production stage, which is a small part for the indirect emissions. To show more detail about the environmental impacts for material phase, it includes not only the GWP, but also the acidification potential (AP), eutrophication potential (EP), ozone depletion potential (ODP), and smog formation potential (SFP). The discoveries from the current study are beneficial for the researchers, engineers and manufactures to minimize the total environmental impact through maximum efficiency and maintaining the maximum sustainability and safety. It can be also beneficial for the researchers and engineers

HVAC&R LCCP ODP EOL EP LCA GWP

heating, ventilating, air-conditioning and refrigeration life cycle climate performance ozone depletion potential end of life eutrophication potential life cycle assessment global warming potential

to design the more efficient and convenient environmental impact assessment tools. Air conditioner unit performance The system test conditions are shown in Table 1 [6]. The indoor unit capacity (Q) is determined using the mass flow rate (mair) and the indoor air side enthalpy difference (Dh), as shown in Eq. (1). The COP is determined as the ratio of the indoor unit air capacity (Q) over the air conditioner total power (W) including both the compressor and fan power, as shown in Eq. (2).

Q ¼ mair Dh

ð1Þ

COP ¼ Q =W

ð2Þ

The COP (or the further calculated SEER) and capacity from cooling A are used for LCCP calculation, as shown in Figs. 1 and 2. Basically, there are three categories: 13 SEER R22, 13 SEER R410A and 14 SEER R410A. The 13 SEER R410A and 14 SEER R410A are the entry level Ingersoll Rand/Trane packaged air conditioner products. On April 24, 2014, the Department of Energy (DOE) and the American Public Gas Association (APGA) reached a settlement agreement on the implementation of the Federal Regional Standards [11]. From this new standard, in 2015, the U.S. DOE will increase the minimum federal standard for the air conditioners in the southern U.S. (including Arizona) to 14 rated seasonal energy efficiency ratio (SEER). The new standards are part of a compromise among industry groups and environmental and consumer advocates. This is resulting from a lawsuit brought against DOE by the Natural Resources Defense Council in 2004 after the Bush administration attempted to reverse air-conditioner efficiency standards set by the Clinton administration. Following this trend, the new 14 SEER R410A products are designed and released. As seen from Fig. 1, the cooling capacity for three categories is pretty close, while the total power consumption for the 14 SEER R410A is the lowest. As seen from Fig. 2, the 14 SEER R410A has the highest SEER value and the 14 SEER R410A in general has the slightly lower cycle degradation coefficients than the old 13 SEER R22 and 13 SEER R410A, which means for the most part it can achieve the better thermal performance than others.

Table 1 ANSI/AHRI standard 210/240 test matrix. Test

Indoor

Outdoor

Operating

D.B.

W.B.

D.B.

W.B.

Extended condition Cooling A Cooling B Cooling C

80 °F

67 °F

115 °F

NA

Steady state cooling

80 °F 80 °F 80 °F

67 °F 67 °F 657 °F

95 °F 82 °F 82 °F

NA NA NA

Cooling D

80 °F

657 °F

82 °F

NA

Steady state cooling Steady state cooling Steady state cooling, dry coil Cyclic cooling, dry coil

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G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125 60000

-1

40000

5500 5000 4500 4000

30000 3500 20000

3000 2500

Air conditioner power (W)

50000

Cooling capacity (Btu h )

system transportation, component manufacturing, etc. A detailed introduction can be found in literature [5]. The LCCP is calculated in CO2-eq. emissions as follows:

6000

13SEER R22 capacity 13SEER R410A capacity 14SEER R410A capacity 13SEER R22 power 13SEER R410A power 14SEER R410A power

10000 2000 0

1500

2.0 Ton 2.5 Ton

3.5 Ton

3.0 Ton

4.0 Ton

5.0 Ton

Air conditioner unit Fig. 1. Packaged air conditioner cooling A capacity and power consumption performance.

Actually there are a series of tests including cooling A, cooling B tests, etc., and only the cooling A performance is shown in Fig. 1. To evaluate the air conditioner CO2 emissions, a series of such tests from Table 1 are used for calculate LCCP. LCCP model framework and material LCA model framework LCCP model framework LCCP is a cradle-to-grave analysis of the environmental impact at all points in the life cycle chain, including the manufacturing of components, system operation and the end-of-life disposal. The LCCP tool can be found via reference [5]. This framework relies on four main modules: (1) the core open-source LCCP calculation methodology, (2) the system performance model, (3) the load model, and (4) standardized reference data sets for emissions and weather. These modules interact with each other via standardized communication interfaces that describe the data input–output process. The LCCP, expressed in terms of the greenhouse gases (GHGs) consists of the direct and indirect global warming impacts. The direct emissions are mainly from the refrigerant leaks. The indirect emissions mainly include the emissions from system operation,

20

1.2

13SEER R22 13SEER R410A 14SEER R410A

16

1.1 1.0 0.9 0.8

12

0.7

-1

-1

SEER (Btu h W )

14

10

0.6

13SEER R22 Cd_c 13SEER R410A Cd_c 14SEER R410A Cd_c

8

0.5 0.4

6

0.3 4

0.2

2

0.1

0

0.0

2.0 Ton 2.5 Ton

3.0 Ton

3.5 Ton

4.0 Ton

Cycle degradation coefficient

18

5.0 Ton

Air conditioner unit Fig. 2. Packaged performance.

air

conditioner

SEER

and

cycle

degradation

coefficient

Emtotal ¼ Emdirect;ref

leak

þ Emdirect;others þ Emindirect;elec

þ Emindirect;others

ð3Þ

Emdirect,ref leak is the direct emission from refrigerant leaks; Emdirect,others is direct emissions from the additional sources: atmospheric reaction products of refrigerant, manufacturing, transport & service leakage, accidents, and EOL refrigerant emissions; Emindirect,elec is the indirect emission from system operation; Emindirect,others is indirect emissions from additional sources: chemical production of refrigerant and transport, material manufacturing and recycling, system assembly. Both the direct emissions and indirect emissions are reported in terms of CO2-eq. emissions, considering the carbon content of the fuel utilized in each process and during system operation. The load model is used to determine the hourly load values which are required by the system performance model. In turn, the system performance model, using the weather data, calculates the hourly energy consumption of the system. The hourly consumption is then multiplied by the hourly emission rate for the electricity production, obtained from the standardized reference datasets for the location-specific emissions, to obtain the hourly emission due to the energy consumption of system. The default values for the hourly emission rate for specified locations within the USA are obtained from Deru et al. [12]. Some building energy modeling tools such EnergyPlus [13] can be used to determine both the hourly load and energy consumption. The default weather data available in the LCCP tool is based on the Typical Meteorological Year (TMY) data from the National Solar Radiation Database [14]. These datasets include the dry-bulb temperature, dew-point temperature, and the relative humidity for all 8760 h of the year. The tool has 47 built-in cities with the ability of adding additional user defined cities. The default GWP values used in the LCCP tool are obtained from the IPCC Fourth Assessment Report (AR4) [15] and are based on the 100 year time horizon (GWP100). LCCP model input data The most important data is the power consumption and the capacity performance data. In addition, there are other emission inputs assumed: annual leakage rate 5%, EOL refrigerant loss 15%, service leakage rate 5%, and accident leakage 0.3%. The back up heat fuel data is set as the default values in the LCCP tools. The model can simultaneously analyze various products for CO2-eq. emissions. LCCP model output data After the input data has been set into the model, the tool provides the output results including LCCP values, details of the direct and indirect emissions for different cities. The model can also be used to make the prediction for LCCPs under different influencing parameters. Material LCA model framework Ingersoll Rand’s (IR) Screening LCA tool, managed by PE, is used to reflect IR’s product portfolio to provide the directional decision support based on a variety of the environmental performance metrics. The calculation is closely follow ISO 14040:2006 and ISO 14044:2006 LCA guidelines. It can also be beneficial to enable the user to perform the quick and easy scenario analyses of new product design concepts based on the incomplete and high-level

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G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

material information. It uses best-case, worst-case, and most-likely modeling assumptions to establish three data points per design option: (1) lower bound = best case, (2) PERT estimate = (best case + 4 times most likely + worst case)/6, and (3) upper bound = worst case. PERT estimate is performed for the current study. The input is the material type with corresponding weight information for the air conditioner unit, and the output is the environmental performance metrics, including AP, EP, GWP, ODP, and SFP. LCCP results and discussion Effect of air conditioner size and climate for LCCP investigation Fig. 3 through Fig. 5 show the LCCP values of three categories for seven US cities, Minneapolis, Boston, Richmond, Los Angeles, San

Antonio, Phoenix, from cold to warm climate zones. Regarding 13 SEER R22, as shown in Fig. 3, from the 5.0 Ton air conditioner to the 2.0 air conditioner, CO2-eq. emissions are decreased sharply. It can also be found that when the climate is varied from cold areas (such as Minneapolis and Boston) to hot areas (such as Phoenix), the CO2-eq. emissions are increased. While for the area of Los Angeles, since the balmy and comfortable weather itself makes the cooling demand decreased greatly, the total emission is lowest among all areas in Fig. 3. It can also be found that the direct CO2-eq. emission is approximately 20% in cold areas of Minneapolis and Boston, while it is approximately only 5% in the hot area of Phoenix. Similar conclusions can be drawn from Figs. 4 and 5 for 13 SEER R410A and 14 SEER R410A, respectively. To make the fair LCCP comparison for the three categories, the area of Richmond is chosen to reveal their performance metrics, as shown in Fig. 6.

250000

Indirect

Direct

150000

-21% -30% -33% -48% -46%

5.0 Ton 13SEER R22 4.0 Ton 13SEER R22 3.5 Ton 13SEER R22 3.0 Ton 13SEER R22 2.5 Ton 13SEER R22 2.0 Ton 13SEER R22

-20% -30% -35% -48% -57%

200000

-19% -25% -25% -41% -46%

-20% -28% -29% -45% -51%

50000

-20% -29% -31% -47% -54%

100000

-20% -29% -30% -46% -53%

LCCP emissions per lifetime (kg CO2-eq.)

CO2-eq. emission composition:

0

Minneapolis

Boston

Richmond Los Angeles San Antonio

US cities

Cold

Phoenix

Hot

Fig. 3. Packaged 13 SEER R22 air conditioner LCCP.

250000

-20% -25% -37% -49% -59%

Indirect

Direct

5.0 Ton 13SEER R410A 4.0 Ton 13SEER R410A 3.5 Ton 13SEER R410A 3.0 Ton 13SEER R410A 2.5 Ton 13SEER R410A 2.0 Ton 13SEER R410A

150000

-20% -25% -31% -49% -57%

200000

-18% -23% -23% -42% -48%

-19% -24% -26% -46% -53%

50000

-19% -24% -29% -48% -55%

100000

-19% -24% -27% -47% -54%

LCCP emissions per lifetime (kg CO2-eq.)

CO2-eq. emission composition:

0

Minneapolis Cold

Boston

Richmond Los Angeles San Antonio

US cities

Fig. 4. Packaged 13 SEER R410A air conditioner LCCP.

Hot

Phoenix

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G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

250000

-16% -31% -37% -52% -59%

Indirect

Direct

200000

150000

-18% -32% -37% -52% -58%

5.0 Ton 14SEER R410A 4.0 Ton 14SEER R410A 3.5 Ton 14SEER R410A 3.0 Ton 14SEER R410A 2.5 Ton 14SEER R410A 2.0 Ton 14SEER R410A

-20% -26% -28% -44% -50%

-19% -29% -32% -48% -54%

50000

-18% -31% -35% -50% -57%

100000

-19% -30% -34% -50% -56%

LCCP emissions per lifetime (kg CO2-eq.)

CO2-eq. emission composition:

0

Minneapolis

Boston

Richmond Los Angeles San Antonio

US cities

Cold

Phoenix

Hot

Fig. 5. Packaged 14 SEER R410A air conditioner LCCP.

100000

Richmond, Virginia Indirect

Direct

75000

3.0 Ton

-12%

+3% -12%

3.5 Ton

-1% -13%

+5% -9%

+2% -5%

50000

-1%

13SEER R22 13SEER R410A 14SEER R410A

-7%

+1%

LCCP emissions per lifetime (kg CO2-eq.)

CO2-eq. emission composition:

25000

0

5.0 Ton

4.0 Ton

2.5 Ton

2.0 Ton

Air conditioner Fig. 6. Packaged SEER rating air conditioner LCCP comparison.

Basically, 13 SEER R410A has approximately a +3% CO2-eq. emission increase as compared with the 13 SEER R22, which is mainly caused by the direct emission of annual leakage of refrigerant. GWP value for refrigerants R22 is 1810, and R410A is 2088, with approximately a 10% increase as compared with R22 (R22 is mainly phased out due to the ODP issues). Therefore, a higher CO2-eq. emission can be achieved for 13 SEER R410A. It can also be found that the 14 SEER R410A depicts a 9% reduction as compared with the 13 SEER R22. Possible explanation is that the new 14 SEER R410A adopts the more efficient scroll compressor, and has the reasonable thermostatic expansion valve (TXV) setting, and uniform refrigerant flow line distribution in the coil for better heat transfer.

It is necessary to reveal the CO2-eq. emission contributors to have a deep understanding about the product LCCP, as shown in Fig. 7. Three product categories are compared at the city of Boston, Richmond and Phoenix. In the cold city of Boston, 13 SEER R410A has a +6% CO2-eq. emission increase when compared with the 13 SEER R22 and the 14 SEER R410A depicts a 9% reduction. Among the contributions for 13 SEER R22, the energy consumption, the main indirect emission, consumes 70% of the total emissions. The annual leakage, the main direct emission, has 21% of the total emissions. Direct emissions from refrigerant loss end of life (EOL) and service leakage make the contributions of 4.0% and 4.0%, respectively. The total direct emission is approximately 29%. From the discussion in this paragraph, the emission due to

G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

LCCP contributors, Boston, Massachusetts 3 Ton 110%

70% 60% 50% 40% 30% 20% 10%

13 SEER R22 Boston, Massachusetts, BSL

80%

14 SEER R410A Boston, Massachusetts, BSL -9% BSL

90%

13 SEER R410A Boston, Massachusetts, BSL +6% BSL

100%

Emissions - Charge

Emissions - Materials and Recycling

Indirect Emissions Emissions - Service

Emissions - EOL

Direct Emissions Emissions - Annual Leakage

Emissions-Energy Consumption

0%

(a) Boston, Massachusetts

LCCP contributors, Richmond, Virginia

3 Ton



      

13 SEER R22 Richmond, Virginia, BSL



13 SEER R410A Richmond, Virginia, BSL +3% BSL



14 SEER R410A Richmond, Virginia, BSL -12% BSL



Emissions - Service

Emissions - EOL

Emissions - Annual Leakage

Emissions-Energy Consumption

(b) Richmond, Virginia

LCCP contributors, Phoenix, Arizona

3 Ton

 

    

14 SEER R410A Phoenix, Arizona, BSL -11% BSL



13 SEER R22 Phoenix, Arizona, BSL



13 SEER R410A Phoenix, Arizona, BSL -2% BSL

Emissions - Charge



Effect of air conditioner system energy consumption reduction for LCCP investigation This section further reveals the detailed effects of energy consumption reduction for product CO2-eq. emissions with location set to be Boston, Richmond, Phoenix, from cold to hot areas. As discussed in Effect of air conditioner size and climate for LCCP investigation, the energy consumption is the largest contributors for CO2-eq. emissions. Therefore, its variation will heavily influence the LCCP results. As shown in Eq. (4) for energy consumption LCCP calculation, tlifetime is the product lifetime (15 years), xlocation is the emission rate for the location city, Whr is the hourly energy consumed, and there are totally 8760 h for 1 year.

Emindirect;elec ¼ tlifetime





can also be found that the indirect emission of materials and recycling is only a small part of the total emissions. In addition, Boston, Richmond and Phoenix, from cold to hot, are compared for three product categories for total emissions. The 13 SEER R410A shows a +6% increase, +3% increase, and 2% reduction as compared with the 13 SEER R22, respectively. The 14 SEER R410A shows a 9%, 12%, and 12% reduction as compared with the 13 SEER R22, respectively. This is because the indirect emission has an increasing weighing factor for the total emissions, from the cold city of Boston (70%), to Richmond (80%) and the hot city of Phoenix (90%).

Emissions - Charge

Emissions - Materials and Recycling

Emissions - Materials and Recycling

8760 X

W hr  xlocation

Emissions - EOL

Emissions - Annual Leakage

Emissions-Energy Consumption



(c) Phoenix, Arizona Fig. 7. Packaged SEER rating air conditioner LCCP contributors.

energy consumption takes approximately 70%. Therefore, more attentions should be paid for energy efficiency improvements. It

ð4Þ

n¼0

The investigation of energy consumption reduction on LCCP results is shown in Fig. 8. For all three cities, results reveal that the CO2-eq. emissions are decreased. The direct emissions nearly remain constant and only the indirect emissions are decreased greatly as the energy consumption reduction is increased. From Fig. 8, with the energy consumption reduction of 5%, 10% and 15%, the LCCP is decreased by approximately 4%, 8%, and 12% as compared with the baseline 14 SEER R410A, respectively. Energy consumption, as the main LCCP contributors, with reasonable and efficient COP strategies, will lead the heavy CO2-eq. emission reductions. Energy efficiency can be improved with more efficient compressor, uniform coil refrigerant distribution, etc. Effect of air conditioner refrigerant recovery rate for LCCP investigation As shown in Eq. (5) for refrigerant leakage at the EOL LCCP calculation, mref is the amount of the refrigerant charge GWP, the GWP value for refrigerants (R22 with 1810, R410A with 2088), xref,EOL is the percentage of refrigerant lost at end of life.

Emdirect;ref EOL ¼ mref  GWP  xref;EOL Emissions - Service

119

ð5Þ

The effect of refrigerant recovery rate on LCCP is investigated by varying it in four rates (82%, 85%, 88% and 91%), as shown in Fig. 9. Results showed that for the area of Phoenix the three categories have the negligible effects on total emissions. Actually, the variation of LCCP results is within 1%. This result can be easily explained from the CO2-eq. emission contributors. The refrigerant leakage is the main contributor for direct emissions and it is approximately only 5.0% of the total emissions for the area of Phoenix. With the refrigerant recovery rate change from 82% to 91%, the total emission variation is within 1%. Since all three categories are the packaged products, the weight of refrigerant effect is quite small as compared with the energy consumption for CO2-eq. emissions. While for the city of Boston and Richmond, the variation of LCCP results can be high of approximately 13% and 8%, respectively. The refrigerant leakage is the main contributor for direct emissions and it is high with approximately 25% and 15% of the total

G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

Indirect

Richmond, Virginia

Phoenix, Arizona -5%

Boston, Massachusetts

3.0 Ton Air conditioner

-9%

Direct

125000

100000 13SEER R22 13SEER R410A 14SEER R410A

25000

0

-8%

-6% -9%

-4%

50000

-12%

75000

-3%

LCCP emissions per lifetime (kg CO2-eq.)

150000 CO -eq. emission composition: 2

-14%

120

-5 -10 15 )0 ) 0 -5 ) -10 ) -15 ) 0 -5 ) -10 ) -15 ) ,% % ) ,% % ) ),% % ) on tion, n,% n,% on ion, ion,%on,% on ion, ion,%on,% i i i t t t t o t ti tio mp p mp p pt pti mp p pt pti su um mp mp su um um m su um um m on ns su su on ns s su on ns s su (C (Co Con Con (C (Co (Con(Con (C (Co (Con(Con ( (

Energy Consumption Reduction

Fig. 8. Effect of air conditioner energy consumption reduction on LCCP.

LCCP emissions per lifetime (kg CO2-eq.)

150000 CO -eq. emission composition: 2 Direct

125000

Boston, Massachusetts

3.0 Ton Air conditioner

+1%0%-1%-2%

Indirect

Richmond, Virginia

Phoenix, Arizona

100000 13SEER R22 13SEER R410A 14SEER R410A

75000

50000

+4% 0% -4%-8% +6%0%-6%-13%

25000

82 % 85 % 88 % 91 %

82 % 85 % 88 % 91 %

88 % 91 %

82 % 85 %

0

Rerfigerant Recovery Rate Fig. 9. Effect of air conditioner refrigerant recovery rate on LCCP.

emissions, respectively. Therefore, for air conditioners in cold areas, the refrigerant recovery rate cannot be neglected for CO2-eq. emission reductions. Effect of air conditioner cycle degradation coefficient for LCCP investigation This section further investigates the LCCP results for the effect of cycle degradation coefficient. Usually the air conditioners cycle off and on at part-load conditions to meet the load. Because of startup losses, the capacity and efficiency are lower at part-load conditions. The SEER procedure accounts for part-load losses with a cyclic degradation coefficient (Cd). The transient startup behavior

can be expressed with degradation coefficients. Usually low Cd indicates high-efficient system performance. The normalized efficiency degradation, i.e. the part load factor (PLF), can be expressed in Eq. (6), it is the function of the part load ratio (PLR). DOE-2 [16] includes several correlation curves that predict the energy use of systems under the part load conditions. DOE-2 simulates systems on an hour-by-hour basis, therefore the correlations are intended to predict the part load energy use (and efficiency) as a function of the (PLR) for each hour, where PLR is the ratio of the hourly load over the available capacity.

PLF ¼ 1  C d ð1  PLRðT amb ÞÞ

ð6Þ

PLR ¼ Q loading =Q available

ð7Þ

121

G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

Indirect

13SEER R22 13SEER R410A 14SEER R410A

Richmond, Virginia

Phoenix, Arizona

Direct

125000

Boston, Massachusetts

-1.5%

3.0 Ton Air conditioner

100000

75000

-1.5%

50000

-1.5%

LCCP emissions per lifetime (kg CO2-eq.)

150000 CO -eq. emission composition: 2

25000

as el in e -0 .0 2 -0 .0 4 -0 .0 6 B

B as el

B as el

in e -0 .0 2 -0 .0 4 -0 .0 6

in e -0 .0 2 -0 .0 4 -0 .0 6

0

Cycle Degradation Coefficient Fig. 10. Effect of air conditioner cycle degradation coefficient on LCCP.

LCCP emissions per lifetime (kg CO2-eq.)

150000 CO -eq. emission composition: 2

3.0 Ton Air conditioner Indirect

Direct

125000

Boston, Massachusetts

Richmond, Virginia

Phoenix, Arizona -12%

100000

13SEER R22 13SEER R410A 14SEER R410A

75000

50000 -14% 25000

-14%

gl e Tw Spd o ca p.

Si n

e Tw Sp o d ca p.

Si n

gl

Si ng le Tw Sp o d ca p.

0

Single Speed vs Two Capacity Fig. 11. Effect of two capacity air conditioner on LCCP.

As shown in Fig. 10, with the value of 0.06 decreased for the Cd values, the CO2-eq. emission is decreased by 1.5%. For air conditioners, the refrigerant recovery rate has larger influence than the Cd on the CO2-eq. emission reductions. Effect of air conditioner two capacity unit for LCCP investigation All the air conditioner LCCP result discussed above is the single speed type. The two capacity air conditioner unit was developed for better loading match at part-load conditions. As shown in Fig. 11 for the effect of two capacity unit LCCP investigation, the 14 SEER two capacity air conditioner product from Ingersoll

Rand/Trane has approximately a 13% CO2-eq. emission reduction as compared with the current 14 SEER R410A air conditioner (single speed). Basically, the two capacity unit has the higher efficiency at part-load conditions. In addition, it has the better comfort condition due to the better load matching (few cycles and less temperature and humidity swing). Furthermore, due to the fewer compressor cycles, it can achieve the higher reliability performance. To explore the reason in detail, Fig. 12 shows the two capacity operation illustration as compared with the single speed air conditioners. The illustrations show profiles of various parameters, such as the high stage capacity, low stage capacity, energy efficiency ratio (EER) or COP, and the single speed capacity. All

G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

60000

122

26

Single speed capacity High stage capacity

Energy efficiency ratio (Btu h-1W-1)

Cooling capacity (Btu h-1)

Loading High stage continuous

Cycling between high& low stage

Low stage capacity Cycling on low stage

High frequency temp. range

75

T1

T2

High stage EER T3

11

6000

Low stage EER

105

Ambient temperature (°F) Fig. 12. Packaged two capacity air conditioner operation condition.

illustrations show the progress of the performance over a range of the ambient temperatures. For the convenience of readers, customers and manufactures, the English unit system is used other than the International units. The magnitude of parameters is not identified exactly at the axis, as the illustrations are meant to merely facilitate the understanding of operation conditions of the two capacity air conditioners. As shown in Fig. 12, when the loading is at the low ambient temperature zone (T1–T2), the low stage capacity is utilized for cycling; while for the single speed air conditioner, the capacity used is much higher than the low stage capacity and the excessive cooling capacity (shaded area in the figure) is wasted. When the loading is in the temperature ozone from T2 to T3, which is the high frequency temperature range, the two capacity air conditioner unit is cycling between the high stage and low stage. If the rough assumption is made that two capacity air conditioner unit cycling in such temperature ozone matches the loading well, the shaded area indicates the excessive cooling capacity is wasted for the single speed air conditioner operation. As to the ambient temperature zone above T3, the two capacity unit operates at the continuous high stage, which is close to the operation of single speed air conditioner. In general, the shaded areas show the wasted cooling capacity for single speed air conditioner (high frequency temperature range: T2–T3), which indicates that excessive CO2-eq. emissions could be produced as compared with the two stage air conditioner unit. Therefore, with a better match with the loadings, the two capacity unit has lower CO2-eq. emissions as compared with the single speed air conditioner unit.

supplied by the vapor compression cycle and furnace is supplied by the gas combustion). The product of air conditioner only provides the cooling. It can be also observed that the 14 SEER R410A air conditioner shows a slightly higher CO2-eq. emission than the 14 SEER R410A heat pump. This difference can be explained with the refrigerant charge amount. For the ANSI/AHRI Standard 210/240 test, the refrigerant charge amount for heat pumps is usually a littler lower than that of the air conditioner because the heat pump should meet both the cooling and heating rating test and the charge amount cannot be large enough. While for air conditioners, since it only provides cooling, the refrigerant charge amount can be large enough to make the cooling capacity more satisfied. As a result, for the CO2-eq. emission with cooling purpose, the slightly lower refrigerant in heat pumps makes less contribution than that of air conditioners. From Fig. 14, it can be observed that in cold areas the heat pumps can achieve a 220% increase for CO2-eq. emissions as compared with air conditioners, while furnace has a 710% high increase. While the increase can be reduced in hot areas since the heating demand is decreased. To reveal more details about the packaged air conditioners, the micro-channel heat exchanger, which has been investigated by researchers widely [18,19], is employed for most 14 SEER R410A air conditioners. It can reduce the refrigerant charge and make the system more efficient with uniform refrigerant flow line distribution in the coil for better heat transfer. In addition, the high efficient Trane unique outdoor unit spine fin coils (Fig. 15) are also employed for better air-refrigerant heat transfer. Material LCA results and discussion

Effect of air conditioner, furnace and heat pump for LCCP investigation Air conditioner material composition This section makes the comparison of the packaged air conditioner, furnace and heat pump for CO2-eq. emissions. The air conditioner and furnace have the same cooling capacity and the furnace has the additional natural gas for backup heat output. As shown in Fig. 13, from cold area to hot area, the cooling demand increases while the backup heat decreases. It can also be found that the heat pump shows larger emissions as compared with the air conditioner, and the furnace shows the largest emissions, especially in cold areas. The packaged heat pump product has been systematically investigated by Li [17]. For the products of heat pump and furnace, they include both the cooling (supplied by vapor compression cycle) and heating sector (heat pump is

The material categories regarding the 3 Ton air conditioners are shown in Fig. 16. The 13 SEER R22 air conditioner and the 13 SEER R410A air conditioner are assumed to have the similar material composition. It can be found that the carbon steel (47%), aluminum (10%), ferrous (17%) are the main materials for the 13 SEER air conditioner unit. The 14 SEER air conditioner unit has a 4% weight increase due to the increasing amount of 22 lbs for the material of aluminum. The micro-channel heat exchanger, which is mainly made of the aluminum and employed in the 14 SEER air conditioners, is the main contributor for material increase of aluminum.

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LCCP emissions per lifetime (kg CO2-eq.)

250000 CO -eq. emission composition: 2 225000

Cooling

3 Ton

HP heating Backup heat

200000

Boston, Massachusetts

13SEER R22 Air conditioner 13SEER R410A Air conditioner 14SEER R410A Air conditioner 14SEER R410A Heat pump 14SEER R410A Furnace

Richmond, Virginia

Phoenix, Arizona

175000 150000 125000 100000 75000 50000 25000 0

Packaged Product Type Fig. 13. Effect of air conditioner, furnace and heat pump for LCCP investigation for energy demand.

CO2-eq. emission composition:

225000 Direct

3 Ton

13SEER R22 Air conditioner 13SEER R410A Air conditioner 14SEER R410A Air conditioner 14SEER R410A Heat pump 14SEER R410A Furnace

Indirect

200000 175000

Boston, Massachusetts

Richmond, Virginia

Phoenix, Arizona +3% +32%

150000 125000 100000

50000 25000

+100% +330%

75000

+220% +710%

LCCP emissions per lifetime (kg CO2-eq.)

250000

0

Packaged Product Type Fig. 14. Effect of air conditioner, furnace and heat pump for LCCP investigation for direct and indirect emissions.

Outdoor coil

Fig. 15. Spin fin.

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Acidification Potential (AP)

Material Composition Carbon steel Ferrous Rubber

0

Stainless steel Non-ferrous Refrigerant

50

100

150

Aluminum Compression molding PWB electronics

Copper Injecon molding Wiring electronics

Carbon steel Ferrous Rubber

Stainless steel Non-ferrous Refrigerant

Copper Injecon molding Wiring electronics

13 SEER unit, BSL

13 SEER unit, BSL:1.94E+02 kg H+ moles-eq.

14 SEER unit, BSL+4%BSL

14 SEER unit, BSL-3%BSL

200

250

300

350

400

450

0%

20%

60%

80%

100%

Fig. 19. Air conditioner material AP distribution.

Fig. 16. Air conditioner material composition.

Global Warming Potential (GWP100) Stainless steel Non-ferrous Refrigerant

40%

Acidification Potential (AP) Distribution

Unit Material Composition (lbs)

Carbon steel Ferrous Rubber

Aluminum Compression molding PWB electronics

Aluminum Compression molding PWB electronics

Eutrophication Potential (EP) Copper Injecon molding Wiring electronics

Carbon steel Ferrous Rubber

Stainless steel Non-ferrous Refrigerant

Aluminum Compression molding PWB electronics

Copper Injecon molding Wiring electronics

13 SEER unit, BSL:6.8810E+02 kg CO2-eq. 13 SEER unit, BSL:9.53E-02 kg N-eq.

14 SEER unit, BSL+9%BSL 14 SEER unit, BSL+5%BSL

0%

20%

40%

60%

80%

100%

120%

Global Warming Potential (GWP100) Distribution

0%

20%

40%

60%

80%

100%

120%

Eutrophication Potential (EP) Distribution Fig. 17. Air conditioner material GWP distribution. Fig. 20. Air conditioner material EP distribution.

Ozone Depletion Potential (ODP) Carbon steel Ferrous Rubber

Stainless steel Non-ferrous Refrigerant

Aluminum Compression molding PWB electronics

Copper Injecon molding Wiring electronics

13 SEER unit, BSL: 6.35E-06 kg CFC 11-eq.

14 SEER unit, BSL+11%BSL 0%

20%

40%

60%

80%

100%

120%

Ozone Depletion Potential (ODP) Distribution Fig. 18. Air conditioner material ODP distribution.

Air conditioner material environmental performance metrics Figs. 17–21 show the air conditioner material environmental performance metrics. These figures can be helpful in understanding the overall results and in identifying hot-spots that drive the environmental performance profile. Fig. 17 shows the GWP-also known as the Product Carbon Footprint (PCF) – based on IPCC 2007 characterization data for a 100 year time horizon. It can be found that 14 SEER unit shows a 9% increase due to the addition of material of aluminum. It should be noted that here only the material phase is performed for environmental performance assessments, and the refrigerant leakage and recycle are not considered here since they are investigated in the LCCP. Fig. 18 shows the ODP distribution. ODP is a measure of air emissions that contribute to the depletion of the stratospheric ozone layer. Depletion of the ozone leads to higher levels of UVB ultraviolet rays reaching the earth’s surface with detrimental effects on humans

and plants. Similarly, it can be found that the 14 SEER unit shows approximately an 11% increase due to the addition of material of aluminum. Fig. 19 shows the AP distribution, which is a measure of emissions that cause acidifying effects to the environment. The acidification potential is a measure of a molecule’s capacity to increase the hydrogen ion (H+) concentration in the presence of water, thus decreasing the pH value. Potential effects include fish mortality, forest decline and the deterioration of building materials. The 14 SEER unit has a larger amount of aluminum than the 13 SEER unit. However, it has less amount of copper. The larger amount of copper for the 13 SEER unit, which is mined in most sulfuric ones, is one of the main contribution for AP. Therefore, the 14 SEER unit shows approximately a 3% reduction due to the reduction of material of copper. Fig. 20 shows the EP distribution. Eutrophication covers all potential impacts of excessively high levels of macronutrients, the most important of which nitrogen (N) and phosphorus (P). Nutrient enrichment may cause an undesirable shift in species composition and elevated biomass production in both the aquatic and terrestrial ecosystems. In the aquatic ecosystems increased biomass production may lead to the depressed oxygen levels, because of the additional consumption of oxygen in the biomass decomposition. Similarly, the 14 SEER unit shows approximately a 5% increase due to the reduction of the material of aluminum. Fig. 20 shows the SFP distribution. SFP is a measure of emissions of precursors that contribute to ground level smog formation (mainly ozone O3), produced by the reaction of VOC and carbon monoxide in the presence of nitrogen oxides under the influence of UV light. Ground level ozone may be injurious to the human health and ecosystems and may also damage the crops. It can be also made the conclusion that the 14 SEER unit shows approximately a 7% increase due to the reduction of material of aluminum. In general, because of the addition of aluminum, the material phase environmental performance may be decreased. From the use phase with LCCP analysis, with the micro-channel

G. Li / Sustainable Energy Technologies and Assessments 11 (2015) 114–125

Smog Formation Potential (SFP) Carbon steel Ferrous Rubber

Stainless steel Non-ferrous Refrigerant

Aluminum Compression molding PWB electronics

Copper Injecon molding Wiring electronics

13 SEER unit, BSL: 3.04E+01 kg O3-eq.

14 SEER unit, BSL+7%BSL 0%

20%

40%

60%

80%

100%

120%

Smog Formation Potential (SFP) Distribution Fig. 21. Air conditioner material SFP distribution.

heat exchanger employed efficiently in the 14 SEER unit, the total emissions during a product’s lifetime is decreased greatly. Therefore, for a sustainable future for products in various applications, it is acceptable with proper material phase CO2-eq. emission increase to decrease the total emissions during a product’s lifetime. For future perspective, minimizing material use and CO2-eq. emissions and maximizing energy efficiency should have been considered in its entirety. Conclusions Comprehensive LCCP and material LCA investigations are detailed from various influencing parameters for the packaged air conditioners. Several conclusions are drawn as follows: (1) The SEER rating for air conditioner systems performs a large influence on lowering the CO2-eq. emissions. The 13 SEER R410A has approximately a +3% CO2-eq. emission increase when compared with the 13 SEER R22 in the area of Richmond, which is mainly caused by the direct emission of annual leakage of refrigerant. It can also be found that the 14 SEER R410A depicts a 9% reduction. Possible explanation is that the new 14 SEER R410A adopts the more efficient scroll compressor, and has the reasonable TXV setting, and uniform refrigerant flow line distribution in the coil for better heat transfer. (2) In general, for all three categories, when the climate is varied from cold areas (such as Minneapolis and Boston) to hot areas (such as Phoenix), the CO2-eq. emissions are increased. Due to the comfortable weather itself, balmy area such as Los Angeles, has the lowest emissions. Among the contributors for CO2-eq. emissions, the energy consumption accounts for more than 70% of the total emissions, followed by the emissions from the annual refrigerant leakage. Therefore, more attentions should be paid for the energy efficiency enhancements. (3) When the energy consumption is decreased by 5%, 10% and 15% as compared with the baseline 14 SEER R410A, the corresponding LCCP is decreased by 4%, 8%, and 12%, respectively. Energy consumption, as the main LCCP contributor, with reasonable and efficient COP strategies, can lead heavy CO2-eq. emission reductions. The refrigerant recovery rate has larger influence than the Cd on the CO2-eq. emission reductions, especially in the cold areas. Basically, the two capacity unit has the better comfort condition due to the better load matching (few cycles and less temperature and humidity swing). Furthermore, due to the fewer compressor cycles, it can achieve the higher reliability performance.

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Therefore, the 14 SEER two capacity air conditioner product has approximately a 13% CO2-eq. emission reduction as compared with the current 14 SEER R410A air conditioner (single speed). (4) The LCA investigation shows that the carbon steel (47%), aluminum (10%), ferrous (17%) are the main materials for 13 SEER air conditioner unit. The 14 SEER air conditioner unit has a 4% weight increase due to the increasing amount material of aluminum. The employing of the micro-channel heat exchanger (as the evaporators), which is mainly made of aluminum and employed in 14 SEER air conditioners, is the main contributor for material increase of aluminum. In general, most of the material phase environmental performance is decreased in the 14 SEER air conditioners due to the addition of aluminum. For a sustainable future, minimizing the material use and CO2-eq. emissions and maximizing the energy efficiency should have been considered in its entirety.

Acknowledgments No funding support. The author would like to express the deepest appreciation to Z. Li and P. Li for their endless love, support, and encouragement during the uncertainty of career path. References [1] U.S. Department of Energy. Energy Information Administration. http://www. eia.doe.gov. [2] Keolian G, Blanchard S, Reppe P. Life cycle energy, costs and strategies for improving a single family house. J Ind Ecol 2000;4(2):135–57. [3] Heikkilä K. Environmental impact assessment using a weighting method for alternative air-conditioning systems. Build Environ 2004;39(10):1133–40. [4] Ochoa L, Ries R, Matthews HS, Hendrickson C. Life cycle assessment of residential buildings. In: American Society of civil engineers construction research congress. San Diego (CA); April 2005. [5] Life Cycle Climate Performance, V1.0, 2014. Available at: http://lccp. umd.edu/ ornllccp/. [6] ANSI/AHRI Standard 210/240. Performance Rating of Unitary Air-Conditioning & Air-Source Heat Pump Equipment. Arlington, Virginia; 2008. [7] ISO. Environmental management—life cycle assessment—principles and framework (ISO 14040:1997). Brüssel: European Committee for Standardisation; 1997. p. 16. [8] ISO. Environmental management—life cycle assessment—goal and scope definition and inventory analysis (ISO 14041:1998). Brüssel: European Committee for Standardisation; 1998. p. 27. [9] ISO. Environmental management—life cycle assessment—life cycle impact assessment (ISO 14042:2000). Brüssel: European Committee for Standardisation; 2000. p. 20. [10] ISO. Environmental management—life cycle assessment—life cycle interpretation (ISO 14043:2000). Brüssel: European Committee for Standardisation; 2000. p. 22. [11] U.S. Department of Energy (DOE). Federal regional standards for heating and cooling products. www.energy.gov/; 2015. [12] Deru M, Torcellini P. Source energy and emission factors for energy use in buildings. NREL Technical Report NREL/TP-550-38617. National Renewable Energy Laboratory: Golden, CO; 2007. [13] EnergyPlus Energy Simulation Software. US DOE, Available at: http://apps1. eere.en ergy.gov/buildings/energyplus/; 2013. [14] NREL, National Solar Radiation Data Base. 1991-2005 Update: Typical Meteorological Year 3. Renewable Resource Data Center, National Renewable Energy Laboratory: Golden, CO; 2012. Available at: http://rredc.nrel.gov/solar/ old_data/nsrdb/19912005/tmy3/by_state_and_city.html. [15] IPCC. Fourth assessment report: climate change. Geneva, Switzerland; 2007. [16] Birdsall B, Buhl WF, Ellington KL, Erdem AE, Winkelmann FC. (DOE2 90) LBL19735, Rev. 1 Overview of the DOE-2 building energy analysis program, version 2.1D; Feb. 1990. [17] Li G. Comprehensive investigations of life cycle climate performance of packaged air source heat pumps for residential application. Renew Sustain Energy Rev 2015;43:702–10. [18] Tuo H, Hrnjak P. Effect of the header pressure drop induced flow maldistribution on the microchannel evaporator performance. Int J Refrig 2013;36(8):2176–86. [19] Tuo H, Hrnjak P. New approach to improve performance by venting periodic reverse vapor flow in microchannel evaporator. Int J Refrig 2013;36:2187–95.