The British Refrigeration Association Specification (1996) describes a way of comparing the influence of different refrigeration systems on climate change. A value, termed the Total Equivalent Warming Impact (TEWI) is determined. This estimates a direct effect, which is the total release of refrigerant and an indirect effect, which is an estimate of the total energy consumption, both expressed in equivalent tonnes of C02 over the expected life of the system. The sum of the two effects is the TEWI value. Apparently, the indirect effect of energy consumption usually dwarfs the direct effect of refrigerant release. Miro and Cox (1999) have pointed out that HFC refrigerants, such as R134a, have a much greater global warming potential on a molecule-to-molecule basis than C02 but their overall contribution is trivially small when the enormous abundance of C02 is considered. HFCs contain no chlorine. See Table 9.7.
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