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  A Comparative Assessment of Refrigerator Test Methods ECEEE 2001, Paper 5.194 Lloyd Harrington Energy Efficient Strategies Australia Synopsis During the development of revised refrigerator Minimum Energy Performance Standards for Australia, intensive refrigerator testing was undertaken to a number of international test methods. Experience suggests a range of recommendations to improve testing methods. Abstract In 1999 Australian Federal and State governments adopted a policy of matching world’s “best practice” for efficiency standards (or Minimum Energy Performance Standards or MEPS) for residential appliances and commercial and industrial equipment. The policy involves reviewing mandatory MEPS  programs in force around the world, assessing the requirements on a common basis (typically in terms of the Australian/New Zealand or AS/NZS test procedures) and selecting the most stringent levels currently in force (or in the process of adoption) for implementation in Australia. The first major product investigation in Australia using this approach was for refrigerators and freezers; US MEPS levels for 2001 are now finalised for implementation in Australia in 2004. The initial levels under AS/NZS were determined using a theoretical modelling approach based on known differences in the Australian and US test methods. A series of 9 refrigerators were tested to AS/NZS, ISO and US test methods for refrigerators to determine actual differences in energy consumption and to confirm in  broad terms the results of the initial modelling approach. This paper presents a range of findings regarding possible improvements within each of the major test methods that will help improve repeatability and reproducibility. It also suggests a new approach to refrigerator testing that will  provide greater flexibility, will enable more accurate modeling of real use in a range of climates and that may assist in the harmonization or at least converging the major international domestic refrigeration testing methods. The paper underlines the importance of test procedures in the implementation of energy policy. Background Codes and standards programs, where legislation and regulation are used to improve product energy efficiency, are amongst the most cost effective and widely used measures employed to reduce greenhouse gas emissions. The Australian program embraces two mandatory elements: ã Comparative energy labelling enabling consumers to choose energy efficient products when considering a purchase; & ã Minimum energy performance standards (MEPS) where government enforces predetermined energy efficiency levels for specified products. Mandatory appliance labelling commenced in 1986 with refrigerators and freezers and by 1990 air conditioners, dishwashers, clothes dryers and clothes washers were also labelled. However, introducing MEPS has proven to be more difficult. In the early 1990’s Australian state and federal governments commissioned expert reports to explore MEPS for domestic appliances (GWA 1993) and selected industrial and commercial equipment (Energetics et al 1994). In October 1999 MEPS commenced for three domestic products: refrigerators, freezers and electric storage water heaters. MEPS electric motors, packaged commercial air conditioning and fluorescent lamp ballasts remain to  be finalised but firm commencement dates are proposed for 2001 (ballasts in 2003/4) (Holt et al 2000). Policy Approach to MEPS The approach to setting the 1999 MEPS levels can be labelled a “statistical approach”; looking at the models available on the market and performing a regression analysis to determine the relationship  between energy use and model adjusted volume. The srcinal proposal for refrigerators and freezers would have eliminated 50% of models current in 1992, though the delay in implementation dramatically decreased the energy savings and greenhouse reductions attributable to the implementation of this 1999 MEPS level (GWA, 2000). The relative leniency, in comparative terms, of   2the Australian levels is due to a combination of the inherent limitations of a statistical MEPS approach in a dynamic market and unforeseen delays due to an absence of agreed process (see Holt et al 2000 for a more detailed discussion on this aspect). A growing recognition of the need to improve process lead to the 1998 government policy directive, contained in the National Greenhouse Strategy, to expand and extend the existing appliance and equipment codes and standards program (NGS 1998). In 1999, the Ministerial Council responsible for energy efficiency agreed to consider: “…. developing MEPS for Australia that match best practice levels imposed by our major trading  partners for internationally traded products that contribute significantly to Australia’s growth in  greenhouse gas emissions ” (NAEEEC, 1999, p8). By adopting an existing MEPS level from a major trading partner, the arguments regarding the “feasibility” of meeting the proposed MEPS level can be essentially transcended. The existence of a “default” MEPS levels from a major trading partner provides a focus for both government and industry and allows the discussions to quickly move forward into the negotiation of detail regarding any adjustments that are necessary for local product configurations and differences in the test method. It does, however, prevent going further to the adoption of lowest life-cycle cost options: to date these have always been at lower levels than world best practice MEPS. It is likely too, that this approach will continue to result in a significant lag between the introduction of a new best standard somewhere else in the world and its adoption in Australia. Details on the timetable for the various stages of the new process are provided in Holt et al (2000). The  balance of this paper concentrates on elements of the work undertaken to complete the review of international MEPS levels and how these were translated into equivalent levels under the AS/NZS test  procedure for refrigerators and freezers in Australia during 2000 and the lessons learned from the intensive testing and associated data analysis. Identifying the most stringent MEPS level Refrigerators and freezers were the first product to be subject to this new policy approach in Australia. A review by Energy Efficient Strategies (EES) (for the AGO) of the MEPS levels for refrigerators and freezers in mid 1999 revealed that, at that time, the US MEPS levels proposed for July 2001 appeared to be the most stringent level proposed or in force around the world (US MEPS levels can be found in DOE 1997). Canadian and Mexican MEPS levels for refrigerators are generally harmonised with US requirements, although the implementation dates vary. At about this time Japan had just released details of its “Top Runner” program, which has some stringent requirements for refrigerators, especially those incorporating new technology such as variable speed drives and vacuum panels. The Top Runner program, developed in 1999, identified the most efficient models on the Japanese market in 1999 for a range of products and set this level as a sales weighted target for all manufacturers at a future date (refrigerator target is 2004). The program is nominally “voluntary”, but the implementation method is quite coercive in nature and can be regarded as effectively “mandatory”. Little information was available on the new test method at the time of the initial analysis, so it was not possible to compare these levels under the Australian test method without extensive investigative testing. The new Japanese method is similar to ISO in terms of compartment temperatures and ambient temperature, but has the added complication of door openings, which makes simulation modelling very difficult. The presence of test packs for convectively cooled appliance types  but not for forced air models also makes direct comparisons difficult for the former types. Korea has had MEPS in place since about 1996, but the levels in force in 1999 were weaker than the US 2001 levels. In late 2000 Korea also announced new MEPS levels for refrigerators, although these have not yet been analysed. The EU MEPS levels for refrigerators that came into force in 1999 were generally more stringent than the Australian MEPS levels for 1999, but were not as stringent as US 1993 MEPS levels (Harrington 1994), especially for frost free products (forced air) which are now dominant on the Australian market (the European market is still dominated by convectively cooled refrigerator products). US 2001 MEPS levels were considerably more stringent than the US 1993 levels. A recent proposal to mandate current   3Class A efficiency as a MEPS for refrigerators and freezers in Europe is outlined in another ECEEE 2001 paper by Dr Paul Waide of PW Consulting. Other MEPS levels reviewed in the international comparison were Chinese Taipei (Taiwan), China and Russia, although obtaining technical details of the latter two proved difficult. Details of all MEPS levels in force as at mid 1999 and a detailed comparison of the test methods in each country used can  be found in APEC (1999). Initial Conversion of US 2001 MEPS levels for refrigerators to AS/NZS4474 Initial US 2001 MEPS levels under the AS/NZS test method were estimated through modelling undertaken by Energy Efficient Strategies (EES) in late 1999. These were offered to industry as the default levels for Australia in 2004 in the absence of an agreement between government and industry. The approach taken in the EES model was to calculate the US MEPS levels under the US test method for each model on the Australian market. The equivalent energy consumption for each model was then estimated under the AS/NZS energy using EES’s thermodynamic model. A linear regression of energy consumption against adjusted volume was then applied to estimate a new MEPS line under the AS/NZS test method that was broadly equivalent to the US MEPS level. Elements of the EES model (EES 2000a) include: ã US MEPS were modelled using imperial units (US DOE metric conversions are not exact); ã US Fahrenheit temperature targets were used (US DOE metric conversions are not exact); ã The condenser temperature was assumed to be 12K above test-room ambient; ã The evaporator temperature was assumed to be 7K below compartment temperature at -18 o C varying to 15K below at +5 o C; ã The model assumed that 5% of frost free energy was used in auxiliaries (ie energy not affected  by changes in ambient conditions; 10% for cyclic refrigerator-freezers, 0% for others); ã Overall energy adjustments for separate freezers in the US test method (0.85 of tested energy for vertical freezers, 0.7 for chest freezers) were reversed out during the conversion; ã Relative heat gains into each compartment are estimated on difference between the ambient test temperature and the average compartment target temperature; ã Changes in compressor efficiency are based on an idealised Carnot engine where COP for a  particular condition = (T evap ) / (T cond  – T evap ) (note: all temperatures are in kelvin) and the change in COP is given by ∆ COP = COP  US  / COP  AS/NZS   Testing Program An intensive testing program was undertaken on a total of 9 two door refrigerator-freezers. The testing was contracted to SGS, are an independent international testing organization with a laboratory in Melbourne. They are accredited by the National Association of Testing Authorities, Australia (NATA) to undertake refrigerator testing. All units tested ranged in capacity from 330 to 650 litres: all but one were frost free models. Three of the units were sourced directly from the USA (110 Volt 60Hz models destined for the US domestic market). US models were selected on the basis of commercially available models that were close to the US 2001 MEPS line. The purpose of the physical tests was to test the accuracy of the initial modelling undertaken by EES and to resolve a number of minor issues regarding adjustments and differences in the test methods between US and AS/NZS. Exploratory tests were also undertaken to examine the energy impact of specific differences the test methods. The primary focus of the physical tests was comparison of AS/NZS and the US test methods (which have many similarities), but most units were also tested to ISO8561. The broad elements of each of the test methods is shown below in Annex A (more details are in APEC 1999). Key Results The modelling undertaken by EES to convert between the AS/NZS and US test methods was very successful. For 6 of the 9 models, the tested AS/NZS and US energy consumption values were in close agreement with the EES model estimates (within 3% of the actual values). However, there were a number of cases where the conversion was in disagreement. On closer examination, the reasons for this were quite clear - the thermodynamic model assumes that the optimal energy consumption at the target temperatures can be attained under both test methods; however, this is not always the case.   4The US test method requires that both controls be moved together   to obtain test points for interpolation; this effectively means that the unit is tested as if there is a single control. A unit’s energy consumption is minimised under the US test method where the fresh food and freezer temperatures  pass through a point of +7.22 o C/-15 o C when both controls are moved together. The tested energy and the modelled energy diverge as the internal temperatures attained during the US test move further from the US target temperatures. In these cases the differences in energy were smaller than modelled. The AS/NZS test method is unaffected by this aspect as both controls can be adjusted as required to obtain the desired target temperatures. In a couple of cases (US imported machines) the AS/NZS target temperatures were unattainable simultaneously in each compartment (for example to meet the fresh food requirement of +3 o C under AS/NZS, the warmest freezer temperature attainable was -18 o C which is much colder than the target requirement of -15 o C); in these cases the differences in energy were larger than modelled. However, this is not surprising as the temperature balance and operational design is poor and ill suited to the conditions of normal use. Suppliers of the machines in question noted that the controllers supplied to the US market were generally low cost and did not offer the range of control offered on equivalent export models. The range of tests undertaken on most models were: ã AS/NZS test as published; ã ISO test as published (25 o C ambient, also 32 o C on selected models); ã US CFR430 test Appendix A as published; ã US test varying the internal fresh food temperature from <+3 o C to the warmest setting with constant freezer temperature (fresh food temperature impact test); ã Constant control settings while varying ambient from +30 o C to +34 o C; ã Constant control settings while setting supply voltage at 230V then at 240V (ambient at +32.2 o C = US condition) (Australian models only, US models all tested at 110V/60Hz only). Key test results are shown in Table 1. Table 1 Summary of energy test results for selected units MODEL FZ a  AS 3 o C/-15 o C FZ a  AS 7.2 o C/-15 o C FZ a  US 7.2 o C/-15 o C Difference actual ** US/AS modelled ISO Measured Unit 1 857.4 * 741.0 725.5 0.874 0.920 N/A Unit 2 896.0 825.5 812.0 0.930 0.940 853 Unit 3 654.2 616.6 725.5 0.955 0.922 651 Unit 4 639.9 598.8 602.9 0.946 0.919 492 # Unit 5 525.4 487.4 500.5 0.942 0.912 450 ## Unit 6 N/A N/A N/A 1.000 *** 0.917 N/A Unit 7 613.3 * 506.8 480.8 0.837 0.907 N/A Unit 8 610.6 * 536.9 519.8 0.891 0.911 N/A  Notes: (a). FZ indicates freezer temperatures – AS indicates 4 probe positions to AS/NZS4474.1 and US indicates 3 (or 5) probe positions to CFR430. Target fresh food/freezer compartment temperatures shown. Units kWh/year. Units 6, 7 and 8 were US models. Results for cyclic/manual defrost model excluded, others frost free. See discussion below regarding ISO energy results and comparisons. * Freezer temperature is at about -18 o C for this energy, hence larger than modeled difference. ** This difference excludes the impact of the freezer thermocouple positions, assumes idealised target temperatures are achieved in both compartments under both test methods. ***Estimate based on US test result data which passes through +3 o C and -15 o C. Under the US test the internal temperatures were far from the US target, hence the difference between US and AS is smaller than expected # For this test the freezer temperature achieved a 2 star freezer rating only, but had the ability to achieve 3 star. ## Unit 5 ISO test at 32 o C ambient was 640 kWh. ISO and AS/NZS test measurements During all tests the temperatures were recorded at 2 minute intervals to provide some comparative data under the different test methods, most notably with and without test packs in the freezer compartment. The following figures show the results on a single model for both the freezer and the fresh food compartments. The x axis is nominal time from the start of the test and the figures all commence with a defrost cycle. The y axis is the compartment temperature in o C.
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