Optimal energy management of water-energy networks via optimal placement of pumps-as-turbines and demand response through water storage tanks

A sustainable water infrastructure cannot be made possible without improving its energy efficiency in terms of the consumption value and the type of supplying resources. One solution to reduce the external energy requirement of the water systems is to decrease the energy consumption, while the internal energy recovery capacity is increased. Such is achieved by the present work through (1) optimizing the water demand and tanks’ and pumps’ scheduling and operations and (2) installing pumps-as-turbines (PATs) where there is excess pressure head in the water. In this paper, two optimization models are developed. The first optimization problem is designed to find the optimal number and location of the PATs among the eligible positions across a water system. The optimal solution will be incorporated in the second optimization problem, i.e., an economic dispatch problem, where the cost of energy generation of an integrated water-energy system is minimized while the water and electrical load demands, as well as the hydraulic integrity of the system are satisfied. The energy system consists of conventional power generation units aggregated of natural gas and diesel based generators, solar photovoltaic units, wind generators, and battery energy storage systems. The proposed models are verified with case studies, and the numerical results show more than 30% reduction in the daily electricity consumption of water systems and $79 in daily operating cost of energy generation in water-energy systems when 3 PATs were installed at optimal locations.