Water Distribution System Optimization Considering Behind-the-Meter Solar Energy with a Hydraulic Power-Based Search-Space Reduction Method

Abstract

To meet increasing energy demands, reduce environmental impacts, and increase economic benefits, many water utilities have installed on-site renewable energy generation and storage facilities. These are commonly referred to as behind-the-meter (BTM) energy systems. This paper proposes a systematic optimization approach to the design and evaluation of water distribution systems (WDS) with BTM solar energy. The trade-offs between economic and environmental costs and the benefits these systems can have throughout their design life are demonstrated using a real-world pressurized irrigation system. Due to the large number of decision variables required during the optimization process and the associated high-computational cost, a hydraulic-power-based search-space reduction method has been developed. This method identifies common features of the pipes across a network based on the potential maximum flow and residual pressure head at the outlet of each pipe, so that pipes having similar hydraulic power capacity and thus similar diameters can be grouped together as a single decision variable. This effectively reduces the search space size and significantly increases the optimization efficiency for complex WDS optimization problems such as the optimal pipe design of WDS incorporating BTM solar energy in this study. In this paper, trade-offs between two objective function values [the total life-cycle cost and total life-cycle greenhouse gas (GHG) emissions] are investigated. A reduction in GHG emissions leads to an increase in the total cost and vice versa. It has also been found that the incorporation of BTM solar energy can significantly improve both objective function values. However, the optimal diameters of pipes and therefore the capital costs and GHG emissions are not sensitive to the increase in solar photovoltaic sizes.