Alternatives in the AC & Chiller Sectors Sukumar Devotta and Lambert Kuijpers OORG Refrigeration 1
Outline ASHRAE position paper summary which marks a difference in the US approach dealing with various types of refrigerants Alternatives in Unitary A/C and Chiller sectors 2
ASHRAE position paper (Jan 09) ASHRAE holds a strong position that: the use of natural refrigerants helps to meet growing HVAC&R demands in a sustainable manner there are still research needs in order to achieve this in a safe, costeffective, and environmentally beneficial manner projects must be assessed in a rational, fact-based, systematic manner to ensure that environmentally beneficial technologies are not rejected on the basis of false information or irrational fears. 3
Unitary Air Conditioning Globally, air-cooled air conditioners and heat pumps --ranging in size from 2 to 420 kw-- comprise a vast majority of the AC market below 1,500 kw capacity. Nearly all air-cooled AC and heat pumps manufactured prior to 2000 used HCFC-22 as their working fluid. Air-cooled air conditioners and heat pumps generally fall into four distinct categories, based primarily on capacity or application: small self-contained air conditioners (window-mounted and through-the wall air conditioners); non-ducted or duct-free split residential and commercial air conditioners; ducted split residential air conditioners; and ducted commercial split and packaged air conditioners. 4
Unitary Air Conditioning- Current Situation HCFC-22 was the ideal refrigerant in the past for AC and is still being massively applied in Article 5 countries. The transition away from HCFC-22 is nearly complete (Europe in 2004) or is well underway in most developed countries. HFC refrigerant blends R-410A and R-407C have been the dominant replacements for HCFC-22 in all categories of unitary air conditioners in developed countries. Hydrocarbons have been used in some applications, including lower capacity portable room units and split system air conditioners. Most developing countries continue utilising HCFC-22 as the predominant refrigerant in unitary air conditioning applications. The two largest developing country markets are China and India. 5
Unitary Air Conditioning - Choices to convert from HCFC-22 Decision XIX/6 has asked to take into account environmental considerations, including climate, when converting from HCFC-22 to other refrigerants (also in AC). Most HFC alternatives available so far have a higher GWP than HCFC-22 and do not show better energy efficiency than HCFC-22 HFC-134a may be the exception; however, HFC-134a has so far not really been considered for large scale AC operations and only in a restricted way for commercial refrigeration Low GWP refrigerants (such as HC-290) are often applied in AC (equipment with small charges); further developments necessary in this area for different types and sizes of equipment. 6
Unitary Air Conditioning - HFCs R-407C is mostly used as a retrofit refrigerant (requires less redesign when converting from HCFC-22) and was also used for new equipment especially in Europe (to facilitate the early HCFC-22 phase-out for new equipment, 2002-2003) R-410A is the most likely refrigerant to replace HCFC-22 in most applications in the developed countries and requires significant redesign. Article 5 countries may go slightly different routes to phase out HCFC-22; near future will show. As many HFC blends containing HFC-125, R-410A shows a capacity and energy efficiency decrease with higher ambient temperatures (much more than e.g. HFC-134a or R-290, both having a much higher critical temperature) 7
Unitary Air Conditioning - HC-290 HC-290 is considered as an alternative to HCFC-22, particularly in low charge applications; IEC Standard 60335-2-40 has established the maximum charge limits for these applications Broader use of hydrocarbon refrigerants in unitary air conditioners will be much more difficult, because the vast majority of unitary air conditioners have much higher charge levels. Significant progress made in reducing charges via redesign and micro-channel HXs. HC-290 is considered as one of the candidates in the phase-out process of HCFC-22 in air conditioning in Article 5 countries; full cost implications are not yet established. There is a significant research conducted on carbon dioxide (R-744) systems to address efficiency issues. It is not yet clear whether this will be a serious candidate in this sector. 8
Unitary Air Conditioning- Future outlook The air conditioning industry is currently exploring alternatives to R-410A and R-407C, which have lower Global Warming Potentials and/or better Life Cycle Climate Performance. Alternatives include: HFC-32, HC-290, CO 2, HFC-152a and possibly HFC-1234yf. Technical challenges: flammability, toxicity, peak load efficiency and economic feasibility. Products with HC-290 have already been developed by some manufacturers. The development of products with the other options is expected to require significant additional research and development.
Chillers - Past and Present Refrigerants Prior to the Montreal Protocol, chillers used these refrigerants: Centrifugal chillers: CFC-11, CFC-12, R-500 Reciprocating and screw chillers: CFC-12 and HCFC-22 with a few using R-717 (ammonia) Now chillers use these refrigerants: Centrifugal chillers: HCFC-123, HFC-134a, HFC-245fa (limited use) Screw and scroll chillers: HCFC-22, HFC-134a, R-410A, R-407C (decreasing) Screw and reciprocating chillers also available with R-717 HCFC-22 has been phased out for use in new equipment in all developed countries by 1 January 2010 (Europe, 2004) 10
Chillers using HFC-134a HFC-134a systems are widely available (350 to 30,000 kw capacity) with both positive displacement and centrifugal compressors. HFC-134a operates at higher pressures than the low pressure chillers; much has been done successfully to reduce leakages. HFC-1234yf is similar in characteristics to HFC-134a and has a potential for applications in screw and centrifugal chillers; however, there are still too many uncertainties. 11
Chillers using Ammonia and Water Using reciprocating compressors, ammonia (R-717) chillers are available in the 10-1600 kw range. With screw the range is 100-7000 kw, with scroll the range goes up to 10,000 kw. Techniques are available to reduce system volume and charge. The market for R-717 chillers is likely to grow in the future in regions where concerns about use of high-gwp refrigerants are strong. However, safety concerns in comfort cooling applications will increase the installation costs and decrease the flexibility of installation arrangements. Water (R-718) applications have been less common for comfort than process cooling. Some water chillers are installed in Europe (limits to evaporation temperature). Large process cooling chillers have enormous compressor swept volumes (low density of water), are mainly applied in mines (South Africa). The higher costs are inherent and are associated with the large physical size of water vapour chillers and the complexity of the large low pressure (fan) compressor technology. R-718 may be used in special applications only. 12
Chillers using Propane and CO 2 Propane (HC-290) is used in chillers (<300 kw) in both industrial and in larger buildings in Europe. Some Article 5 countries such as Indonesia, Malaysia, and the Philippines are applying hydrocarbon chillers to large space cooling needs. However, safety codes restrict hydrocarbon use for the large refrigerant charges in chillers due to problems associated with flammability. The use of HC refrigerants in small chillers is likely to grow in the future where codes and regulations allow. Several companies have started the production of R-744 (CO 2 ) chillers. R-744 chillers are not known to meet present chiller energy efficiency standards. In cooler climates such as in northern Europe, R-744 chillers are accepted as alternatives to HFC chillers. R-744 chillers offer the advantage of being able to use waste heat to raise water to higher temperatures with higher efficiency than other refrigerants. For this application, R-744 heat recovery chillers provide good efficiency. 13
Centrifugal Chillers - Low GWP Alternatives Centrifugal chillers No replacements for HCFC-123 or HFC-134a have been commercialized yet. After phase-out for new equipment, HCFC-123 can be produced for servicing existing chillers. Recovery and recycling also can provide HCFC-123 for chillers in service. Hydrocarbons are used in centrifugal chillers in process applications but not for comfort cooling because of safety concerns with large refrigerant charges. Water (R-718) can be used with centrifugal compressors, but chillers are physically large and have higher costs because of their size and compressor complexity. HFC-1234yf may prove suitable for centrifugal chillers but it is too early to tell. It is not clear whether HFC-1234ze will find any use in low pressure chillers. 14
Low GWP Alternatives to R-410A R-410A is an HFC blend with higher operating pressures and lower volumetric flow rates than HCFC-22. Many chiller manufacturers converted production of scroll and some screw chillers to R-410A because of the phase-out of HCFC-22. R-717 and HCs were not chosen because of safety concerns that R- 410A did not have. At this time, there are no known low-gwp refrigerant alternatives to R-410A, if major redesign is excluded 15
Thank you 16