Current status main existing and future technology options

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Current status of the main existing and future technology options by Dennis Clodic and Sabine Saba.

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Current status main existing and future technology options

  1. 1. Current status of the main existing and future technology options Denis Clodic, Sabine Saba CEP, MINES ParisTech MAC and Environment: India policy workshop on the status of MAC replacement technologies
  2. 2. Contents • Environmental impact of HFC-134a • Technical criteria for a new refrigerant in MAC systems • CO2 as an option for replacement of R-134a • R-1234yf as an alternative option • R-152a where are we? MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 2
  3. 3. Refrigerants for Mobile Air Conditioning  Phase-out of CFC-12 by introduction of HFC-134a: • completed as of 1995 in developed countries • in all car manufacturing countries as of 2003  European Directive 40/2006: progressive phase-out of HFC-134a as of January 1st 2011for MAC  Decision based on: • High GWP of HFC-134a (1430) • “availability” of a low GWP technical option: CO2 for MAC • Possible competition with HFC-152a MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 3
  4. 4. Evaluation of HFC-134a environmental impact Typical penetration curves for MAC systems Sales of vehicles equipped with ACs
  5. 5. Evaluation of HFC-134a environmental impact RIEP – An advanced emission-factor approach RIEP : Refrigerant inventories and emission prevision Equipment level Operator level Refrigerant use in new equipment and for retrofit Annual sales Recovery efficiency Nominal charge Emissions during the Lifetime (mean or charging process survival curve) Bank Leakage rates Emissions and demand
  6. 6. Evaluation of HFC-134a environmental impact Total emissions of Mac systems of light vehicles Total em issions CO2 eq. em issions CFC HFC CFC HFC 100 000 600 000 500 000 80 000 .10e3 tonnes 400 000 60 000 tonnes 300 000 40 000 200 000 20 000 100 000 0 090 93 96 99 02 05 90 93 96 99 02 05 19 19 19 19 20 20 19 19 19 19 20 20 * D. CLODIC, S. BARRAULT, S. SABA - Global inventories of the worldwide fleets of refrigerating and air-conditioning equipment in order to determine refrigerant emissions. The 1990 to 2006 updating, ADEME, April 2010 6
  7. 7. Evaluation of HFC-134a environmental impact HFC em issions distribution in 2006 HFC CO2 eq. em issions distribution in 2006 Domestic Domestic 2% Commercial 1% 14% Commercial Transport 27% 2% Industry 2% Mobile AC Air to air AC 50% 13% Transport Mobile AC 2% 61% Chillers Industry 6% 3% Air to air AC Chillers 12% 5% Rapid switch from CFC-12 to HFC-134a within MAC systems Dominance of MAC systems to HFC emissions 5
  8. 8. Technical criteria for a new refrigerant in MAC systems MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 8
  9. 9. Refrigerant and design issues  Cooling capacity should be identical for the same surface areas of condenser and evaporator.  Three possible options: • Keep the same range of volumetric capacity (soft optimization): R-12, R-134a, R-1234yf • Change the range of volumetric capacity and consequently of pressures (R-744) • Indirect system with a flammable refrigerants: R-152a, R-290 9
  10. 10. Refrigerant and design issues  The most significant criteria are: • cooling capacity • COP  By design, the MAC system will be either soft optimized by integration of the detailed thermophysical properties or designed anew when thermophysical properties are significantly different. 10
  11. 11. Thermal stability  Highest pressures and temperatures are met at the discharge compressor port.  Tests are performed both in sealed tubes and on test benches in real operation conditions.  Possible decomposition of molecules occurs if the molecule bonds are weak or if active chemistry occurs (small water content). 11
  12. 12. Compatibility with materials and elastomers  Sealed glass tubes contain typical materials found in Refrigeration systems (aluminum, copper, steel), they are mixed with refrigerant and oil mixture and are heated up during long period of time (15 days) in order to verify possible reactions (Ashrae standard 97-99).  Elastomer tests are done at different temperatures to verify swelling or shrinkage, even reaction between the oil-refrigerant mixture and the elastomer material. 12
  13. 13. Diffusivity and solubility in elastomers  Characterization of the permeability of refrigerant gas through polymers used in hoses is necessary to verify the leak flow rate associated with elastomer permeability.  The leak flow rate is a function of the saturating pressure of the refrigerant and varies with the square of the pressure. It has been one of the main drivers to keep the range of evaporating pressure identical when replacing R-12 by R-134a. 13
  14. 14. CO2 as a technical option Issues to be addressed  Energy efficiency  Technical complexity  Reliability of high pressure system  Costs  Global solution or not MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 14
  15. 15. CO2 for low cost vehicle: the EU B Cool project A 6 million € research project  CO2 is an efficient refrigerant in MAC systems for outdoor temperatures lower than 35 °C  CO2 exhibits energy issues when the vehicle is idling MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 15
  16. 16. CO2 as an option for replacement of R-134a  CO2 requires additional components: • Internal heat exchanger for additional cooling after the gas cooler • Controlled variable displacement compressor • Electronic expansion valve MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 16
  17. 17. CO2 as an option for replacement of R-134a MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 17
  18. 18. CO2 as an option for replacement of R-134a  On the tested prototypes: energy consumption is higher for all tested temperatures MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 18
  19. 19. CO2 as an option for replacement of R-134a  The overall costs for mass production is estimated 80% higher  For low cost vehicles the cost constraint is too high MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 19
  20. 20. Current conclusions for CO2 • Major developments have succeeded in efficient CO2 systems at high cost • Reliability is an issue due to possible high leak flow rates at the compressor shaft seal • CO2 is not a global refrigerant • CO2 is not the reference choice for low cost vehicles MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 20
  21. 21. R-1234yf as a technical option • Energy performances • Flammability • Costs MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 21
  22. 22. R-1234yf as an alternative option MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 22
  23. 23. R-1234yf and flammability Refrigerant Molar LFL UFL RCL RF BV MIE HOC mass (% v/v) (% v/v) (kg/m3) number (cm/s) (mJ) (MJ/kg) (g/mol) (kJ/mole) R-290 44.1 2.5 10 0.009 56.7 46 0.25 46.3 R-152a 66.0 4.65 16.9 0.025 16.6 23 0.38 17.4 R-717 17.0 15 18 0.00035 6.82 7.2 100 18.6 R-32 52.0 14.4 29.3 0.0614 4.6 6.7 30 9.4 R-1234yf 114 6.2 12.3 0.058 3.6 1.5 5000 10.7  LFL - Lower flammability limit, with the usual ASTM E681-01  MIE – Minimum Ignition Energy, measured with a modified ASTM E582 standard  BV – Burning Velocity, measured by accepted test methods such as the tube or the bomb method MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 23
  24. 24. R-1234yf and flammability  The severity of damages is different depending on the burning velocity  The BV of R-1234yf limits the severity MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 24
  25. 25. R-1234yf and flammability  MIE is the property that ranks the possible sources of ignition  The MIE of R-1234yf eliminates most possible sources of energy on a vehicle MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 25
  26. 26. R-1234yf and energy efficiency  Tests made in 2008 on a nearly drop-in basis by a number of OEMs show a lower refrigeration capacity and, many times, a higher COP  Diagnosis: adaption of heat-exchanger, expander, and compressor will lead to similar performances to that of HFC-134a MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 26
  27. 27. Current conclusions for R-1234yf • Energy efficiency and cooling capacity are comparable to HFC-134a • R-1234yf is not a toxic refrigerant; it is classified as A as R-134a • Flammability : R-1234yf is classified 2L (ISO 817), risks are seen as acceptable by car manufacturers • Cost is unknown, global market is also unknown MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 27
  28. 28. R-152a as a technical option • Energy efficiency • Flammability • Direct expansion or Indirect system? • What technical development? MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 28
  29. 29. HFC-152a as a possible option  Few papers (B. Hill and J Baker)  Cooling performances comparable in wind tunnel tests MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 29
  30. 30. HFC-152a as technical option  Energy efficiency claimed to be in the same order of magnitude as tests made in laboratory MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 30
  31. 31. HFC-152a and flammability  Flammability tests have led to the conclusion that indirect systems are preferable MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 31
  32. 32. Indirect HFC-152a system  Energy performances is lowered of 5 to 10%  In real conditions inertia of the secondary loop is an advantage when idling and a drawback for cool down  Costs are estimated to be 15 to 20% higher compared to a direct system MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 32
  33. 33. Current conclusions on R-152a  Flammability is significantly higher compared to R-1234yf and lower compared to propane  Flammability requires indirect system design for R-152a  Cost of R-152a is low, additional cost is related to the system (15 to 20%)  Few developments, few advocates of the solution MAC Refrigerant Update – UNEP Workshop, Dehli, June 7-8, 2010 33
  34. 34. Conclusions  After CFC-12, HFC-134a has been the global refrigerant for MAC systems  Nearly 90% of new European vehicles are air conditioned  Most light vehicles sold in China and India are air conditioned  The increase in HFC-134a emissions has been seen as non sustainable by the EU Commission 34
  35. 35. Conclusions (cont’d)  CO2 has been seen as the possible replacement for HFC-134a  Costs of CO2 systems for MAC are significantly higher compared to the base line.  CO2 systems require high reliability of open type compressor shaft seals .  CO2 hermetic compressor for hybrid and electric vehicle may change the refrigerant choice for those vehicles  CO2 technical development has been the basis of the European decision. 35
  36. 36. Conclusions (cont’d)  HFC-152a has not been tested at a fleet level  No OEMs except GM have shown interest in this refrigerant.  R-1234yf has taken the lead because of simplicity of adaptation  R-1234yf has not yet a market because the regulation is only issued in Europe. 36

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