Integrated modelling of residential water-related energy

Abstract

Around the world, urban demand for resources is increasing over time. In Australia, 90% of the population resides in cities, which are growing in both population and housing density. These factors place greater demands on water and energy, and associated greenhouse gas (GHG) emissions. Water use, energy use and GHGs are strongly interconnected, and thus actions to reduce water or energy consumption can have unintended consequences. Consequently, reducing water use without increasing energy use and GHGs as well as reducing energy use without increasing water use is important. One key area where this can be achieved is in the reduction of water-related energy (WRE) use. WRE consumption occurs in two distinct sectors: the water sector through water supply and sewage collection services, and the residential sector through water end uses. WRE use of both utilities and end users are interconnected through infrastructure, environment, technology, behaviour, and policies. WRE use of water supply (10%) and sewage collections services (10%) are both within the control of utilities, however, the most WRE intensive component of the residential urban water cycle is residential end use (80%), which is largely outside the control of water utilities. This thesis used a systems approach to WRE modelling, across the water utility and residential sector interface, to investigate opportunities for whole-of-system reduction in resource consumption. Firstly, this study investigated an interaction between the infrastructure and the environment through the cold water temperature (CWT) variability impact on household WRE. The spatiotemporal variability in CWT was determined using 5760 measurements from 1255 sampling locations across Yarra Valley Water, Melbourne, Australia. The monthly CWT varied across the 4000 km 2 study site from 12-28°C during summer and 9-15°C during winter. Spatial clusters of hot spots and cold spots were observed. Variation in CWT was calculated to affect annual household WRE demand by-17 to +19%. Variability in results demonstrated the difference in household WRE demand in hot spots, cold spots, and neutral zones. Monthly mean CWTs for the study site diverged from hot water system (HWS) energy consumption guidelines by-21 to +47%. The CWT variability impact on household water heating varied up to three times the energy used by the water utility for water supply and sewage disposal services in this region. Results demonstrated the importance of modelling interactions between infrastructure and the environment. Quantifying the variability of CWT increased the accuracy of predicting regional WRE demand and HWS energy consumption.