Life-cycle Energy Consumption of Urban Water System in Shenzhen, China

Abstract:

Within rapid urbanization and industrialization, Shenzhen, the first special economic zone in China, has been facing serious water shortage. More than 80% of water demand in Shenzhen, i.e., about 1.6 billion m³/yr, is satisfied by water diversion projects. A lot of energy has been used to extract, clean, store and transmit these water. In this paper, energy consumption of urban water system in Shenzhen, China was investigated from a life cycle perspective, and the water system can be divided into five subsystems, i.e., water diversion, water production & supply, household water use, sewage treatment and water reuse. Industrial water use was not considered here, because industrial production processes were so varied. The results showed that water diversion subsystem in Shenzhen consumed electricity of about 0.839 billion kWh/yr (0.53 kWh/m³), water production & supply subsystem about 1.241 billion kWh/yr (0.64 kWh/m³), household water use subsystem about 6.57 billion kWh/yr (9.65 kWh/m³) sewage treatment subsystem about 0.449 billion kWh/yr (0.29 kWh/m³) and water reuse treatment subsystem about 0.013 billion kWh/yr (0.33kWh/m³). So the human-related water system in Shenzhen consumes electricity of about 9.113 billion kWh/yr in total, accounting for about 11.0% of all the electricity use in Shenzhen. Among this, household water use subsystem consumed up to 72.1% of all electricity used in urban water system, followed by water production & supply subsystem (13.6%), water diversion subsystem (9.2%) and sewage treatment and reuse subsystem (5.1%). Unit energy consumption of sewage treatment and reuse subsystem was much less than that of water diversion subsystem, indicating local sewage resource development was advantageous on saving energy to water diversion from a long distance. Further, it implied that the best way to save energy in urban water system is to save portable water, since both water production and household use require to consume much energy.