Effect of Storage Tank Size on the Minimization of Water Distribution System Cost and Greenhouse Gas Emissions While Considering Time-Dependent Emissions Factors

Abstract

The importance of reducing greenhouse gas (GHG) emissions, which have been linked to human-induced climate change, is gradually being recognized by water utilities. Although multiobjective optimization has been applied by previous literature to minimize cost and GHG emissions associated with water distribution systems (WDSs), this has primarily been achieved by considering design options of pipe size and pump type. Little consideration has been given to the appropriate sizing of storage tanks. As such, this paper aims to investigate the effect of storage tank size on the minimization of cost and GHG emissions associated with WDSs. Increases in storage tank size are considered by increasing the tank reserve size (TRS), i.e., the portion of the storage tank available for system balancing purposes. Because storage tanks are critical to the operation of a WDS, it is necessary to accurately model the operation of a WDS. Although electricity tariffs (ETs) are used to consider the time dependency of pumping operational cost, no such consideration has been given to pumping operational GHG emissions. As such, time-dependent emissions factors are used to calculate pumping operational GHG emissions. To investigate the effect of TRS on the minimization of cost and GHG emissions associated with a WDS, the multiobjective optimization of two WDS case studies is performed. The results show that using different TRSs can affect the optimal pumping operational management of a WDS, and increasing the TRS can result in GHG emissions reductions. However, using a very large TRS is likely to be associated with prohibitive costs.