Environmental evaluation of pump replacement period in water supply systems of buildings

Cost analysis of facility replacement is the common method used in building services facility management nowadays, however, replacement evaluation from the environmental aspect still lacks in literature. This study is the first trial to introduce the environmental evaluation, life cycle assessment technique is adopted, into the replacement period justification of building services facilities, taking water supply pump in buildings as an example. An environmental evaluation model of water supply pump replacement is proposed in this study to minimize the total environmental impact (i.e. energy consumption) of the water supply system, which compares the extra operational energy expenditure in the long-term operation to the pump embodied energy. The literature review is used to obtain the energy intensity data, of mining, metal production, and metal casting, for the determination of pump embodied energy. The results demonstrate that for common pump motor ratings of 1.1–5 kW in water supply systems of buildings, with annual efficiency drop and pump energy intensity that ranges from 0.012 to 0.028 and 18.2–177.6 GJ/t iron and steel respectively, a longer pump replacement period is noticed at the greater energy intensity of pump (the maximum difference of the replacement period can be about 10 years). Besides, higher annual efficiency drop justifies a shorter pump replacement period. It was found that the replacement periods of smaller pumps are more sensitive to the pump energy intensity and annual efficiency drop. Moreover, it was also shown that for pumps with the maximum embodied energy intensity (i.e. 177.6 GJ/t iron and steel), for example, the pump material is stainless steel, the pump replacement periods evaluated on the environmental and economic grounds are comparable. The study results provide an alternative solution of pump replacement period for water supply systems in buildings based on the life cycle environmental assessment of water pump.