Bench Test - an overview

3.4 Results

From laboratory bench-tests [13] it has been difficult to determine whether product lifetime will be reduced due to a change in the working fluid. Nonetheless, an extension in product lifetime as a result of this change is definitely contradictory due to the increase in the electrical power requirements observed (Table 1). Table 1 lists the CO2 contribution for the life cycle of the functional unit up to the end of its technical lifetime. The table assumes that the HFC compliant unit fails after 10 years. This 10 year period is an arbitrary value used to study the implications of premature product retirement and help highlight the fact that for a shorter product lifetime the environmental impact in the use phase drops but all other impacts gain in significance. This value was conveniently chosen to correspond to the projected direct and indirect CO2 emissions resulting from domestic refrigeration in the UK by 2010 (4.8Mt of CO2 equivalent). Hence, a percentage contribution towards these projections, as a result of a deterioration of power requirements or premature product failure, was calculated using detailed LCA. For calculation purposes, it was necessary to assume that 1.2 million HFC-134a units are sold in the UK in the year 2000. Further details of how the values in Table 2 were obtained are given in [15].

Table 1. Projection of energy consumption

Test labelRate of change of regression curveProjected power (W) after 500 hours

a

Lifetime electrical energy consumption

b

(MJ)Percentage difference between rated and projected valuesTest 1-0,021699.29385-9.82Test 2-0.0169101.89621-7.55Test 3-0.029395.49026-13.27Test 4-0.078870.66679-35.82Test 50.0058112.910,681+2.63Test 6-0.070374.97086-31.91Test 70.0106115.310,908+4.82Test 8-0.066976.67242-30.36

Table 2. Refrigerator CO2 contributions and its increase on 2010 projections

HFC-134a compliant (kg equiv.)CFC-12 compliant (kg equiv.)Increase in contribution for HFC unit

a

(kg equiv.)Contribution towards 2010 projections for CO2 equiv. emissions

b

Items

c

making up the functional unit

d

666.8663.9Compressor

d

103.6103.6Refrigerant production

e

1.40.9Lubricant production

f

0.81.2Lifetime of functional unit

g

:15 years2525.11640.3887.815%10 years1683.91093.6849.821%

For the completion of Table 2, four considerations were made. Firstly, it is important to note that the impact for the mineral and synthetic lubricants was included for completeness. This value assumes the production of the base oil alone and no consideration to the unknown additives in the POE was made. Therefore, this value is inaccurate but was included as it does not increase the results significantly and it is appropriate for comparison. Secondly, for the contribution throughout the use phase, the compressor electrical requirements for Test 6 and Test 7 were considered and these were assumed to stabilise just after 1000 hours of operation (Table 2). From observations made throughout this work, no indication of this assumption was given and therefore it is possible that the lifetime contributions will actually increase further for HFC-134a. Thirdly, during the time this research was carried out not enough information was obtained regarding the indirect effects of the disposal phase of a refrigerator. Undoubtedly, this would have augmented the percentages in Table 2. Finally, the percentage value obtained, albeit indicatory, does not account for any HFC-134a units manufactured prior and after the base year assumed (the year 2000) and therefore the contribution itself may be even higher.

Findings in Table 2 emphasise the importance a detailed LCA study has. Although influenced by the boundaries and assumptions set [15], this table should justify the use of the life cycle concept in quantifying the environmental burdens resulting from the use of a CFC substitute. By considering and comparing the CO2 equivalent emissions to projected emissions, this table identified a significant setback to the efforts being made by the UK (and other countries) to reduce greenhouse gas emissions from the domestic sector as a result of the Kyoto Protocol [19]. It is only through the use of this life cycle concept that the significance of such a contribution may be measured. Findings made here also emphasise the fact that, although shortening product lifetime increases the emissions pertaining to manufacturing, the environmental impact resulting from increased energy consumption is high enough to render a shorter product lifetime attractive, should new products become more efficient. It is accepted that the study does not account for indirect emissions resulting from end-of-life activities, which would increase if shorter lifetimes were experienced.