iea annex 54 update – low-gwp refrigerants in residential ac - … · 2020. 6. 26. ·...

Energy Efficiency and Heat Pumps ConsortiumCopyright © 2020 Center for Environmental Energy Engineering

IEA Annex 54 Update –Low-GWP Refrigerants in Residential AC

June 2020

Tao Cao, Yunho Hwang

Center for Environmental Energy EngineeringDepartment of Mechanical Engineering

University of MarylandCollege Park, MD 20742-3035


Background• Low GWP refrigerants are coming for residential AC systems.• Yet, there hasn’t been a consensus on the winning candidate.• What’s the latest R&D and regulation efforts in bringing low

GWP alternatives to residential AC?

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• AC leads the power consumptions in residential sectors.

Fig. source: [1]


Recent Reviews• Comprehensive reviews focusing on residential AC alternatives are needed.

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Author Focus Highlights

Dalkilic and Wongwises (2010) [2]Theoretical analysis R12, R22 and R134a replacement with

mixtures from (R134a, R152a, R32, R290, R1270, R600 and R600a)

R290/R600a (40/60) best alternative for R12; R290/R1270 (20/80) best alternative for R22

Benhadid-Dib and Benzaoui (2012) [3] Briefing on refrigerant phasing history up to 2015. Cover the basics of most refrigerants, and overview of regulation efforts

Wang et al. (2012) [4]Alternative refrigerants for air conditioners, heat pumps,

chillers, water heaters, ice makers and refrigeration equipment

AHRI led, industrial-wide cooperative program lasts years, covers dozens candidates

Bolaji and Huan et al. (2013) [5] Natural refrigerants: R717, HCs, R718, R744 Reviewed potential application of major natural refrigerants, including oil compatibility

McLinden et al. (2014) [6] 62 candidates with critical temperatures within 300 to 400 K Thermodynamic analysis indicate no ideal fluid

Sarbu (2014) [7] Candidates for air conditioning, heat pump and commercial refrigeration applications Describes refrigerants selection based on properties

Mota-Babiloni et al. (2015) [8]Commercial refrigeration working fluids R404A, R507A and their substitutes: HC, Natural (CO2, NH3), HFC, HFO/HFC

mixture

No universal solution: propane for low charge; low-GWP HFC or HFC/HFO mixture as drop-in or retrofit; CO2 for

transcritical

Pham and Monnier (2016) [9] R410A interim replacements (R32 and other A2L HFO blends) and long term replacements (natural, HCs)

Dedicated overview for R410A, different paths towards long term ultra-low-GWP

Domanski et al. (2017) [10] R410A and R404A candidates review Comprehensive database search based on modeling and cycle analysis

Mota-Babiloni et al. (2017) [11] Focused on recent low-GWP investigations because of F-gas Regulation for applications of all sizes

Unique perspective looking into policy driven advancements in low-GWP research and commercialization

Harby (2017) [12] Hydrocarbon as replacements in refrigeration, AC and automobile AC Comprehensive review of latest HC research efforts

Abas et al. (2018) [13] Major natural and synthetic refrigerants A parametric quantification based model for natural refrigerant selection and optimization

Ciconkov (2018) [14] Historic overview of refrigerants transition up to now and future envisions, focusing on natural refrigerants and HFOs

Proposed direct phase-in of natural refrigerants instead of step by step phase down


R&D Progress – A1

• R744, GWP: 1• Pros: environmentally benign and stable• Cons: need major system redesigns to improve performance and reliability (high pressure)• R&D Gaps: mostly focused on applications other than residential

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• R466A (49% R32, 11.5% R125, 39.5% R13I1), GWP: 730• Pros: non-flammable, similar properties of R410A• Cons: supply and cost associated with iodine in R13I1• R&D Gaps: need more performance and reliability studies


R&D Progress – A2L• R32, GWP 675• Performance: close to R410A (lower discharge T limits)• Pros: low GWP, pure fluid, validated success in ductless units• Cons: flammability, interim replacements• R&D Gaps: safety study (for unitary systems)

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• A2L mixtures, GWP: ~200 to ~700)• Representatives: R452B (67% R32 + 26% R1234yf + 7% R125); R454B (68.9% R32 and 31.1% 1234yf);

R446A (29% R32 + 3% R600 + 68% R1234ze); R447A (68% R32 + 3.5% R125 + 28.5% R1234ze(E))…

• Performance: on par with R410A with variations• Pros: lower GWP than R32• Cons: flammability, interim replacements, not validated in the market• R&D Gaps: need to find convincing advantages over R32 and R466A

Operating Envelop R32 vs. R410A [15]


R&D Progress – A3

• A3, GWP < 100• Representatives: R290, R161• Performance: slightly lower than R410A but can be improved with system redesigns• Pros: ultra-low GWP (ultimate replacements)• Cons: flammability, costs with associated product redesigns• R&D Gaps: ways to handle flammability without sacrificing performance and cost

• Safety precautions• Secondary loop• Novel designs (On-going efforts)

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Comparison

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• R466A, R32, R452B / R454B and R290 remain the top replacements of R410A for now, considering balances among the GWP, performances and property similarities.

Fig. source: [16]


Regulation Progress – USA• Refrigerants

• ASHRAE Standard 34: refrigerant classification• EPA SNAP: identify acceptable substitutes (environmental aspect)

• System• ASHRAE 15: refrigerant system safety (subcommittee 15.2 for residential application)• UL IEC: safety of household appliances

• Building & Local Codes

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Code Adoption Process

Fig. source: [17]


Novel Unitary System Design• Propose a novel design, enabling safe flammable refrigerant usage while ensuring

performance advantages over R410A• The APF can be increased by up to 45% as compared to the existing design based on simulations.• Refrigerant charge can be reduced by 54%.

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System Schematic

COP Comparison vs. Ambient Temperature (Top);Performance Comparison in Different Climates (Bottom)


2nd Year Work – Component Optimization

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• Objective:• A comprehensive review of latest R&D progress on component

optimizations using low-GWP refrigerants in residential AC• Performance, charge and cost comparisons of various novel HX

designs aiming for low GWP refrigerants in residential AC• Expected outcome:

• An report covering latest R&D progress, clarifying research trends of component optimizations for residential AC refrigerant replacements (On-going, 30+ review completed)

• A quantitative comparison of various novel HX designs. Guidelines on future high performance, low charge HX designs for residential AC


Conclusions• We have completed a review of recent R&D and regulation

progress on low GWP refrigerants for residential AC.• R466A is the most promising non-flammable immediate

replacements, though more performance and reliability studies are necessary.

• R32 remains in strong position over other A2L mixtures with proven market success, other than unitary systems.

• The ultra-low-GWP replacements are still an open question.• Existing efforts to promote interim refrigerants mostly focus

on product safety re-designs.

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Thanks!

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environmental impact. Int J Refrig 2017;82:288–301. https://doi.org/10.1016/j.ijrefrig.2017.06.026.12. Harby K. Hydrocarbons and their mixtures as alternatives to environmental unfriendly halogenated refrigerants: An updated overview. Renew Sustain Energy Rev

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https://doi.org/10.1016/j.enbuild.2007.03.007

https://doi.org/10.1016/j.ijrefrig.2017.12.006

https://doi.org/10.1016/j.ijrefrig.2015.08.004


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