New Techniques to Analyze Energy Use and Inform Sustainable Planning, Design, and Operation of Public Water Systems

Abstract

Public water systems face escalating energy requirements due to scarcer water supplies, stricter water quality standards, and population growth. As the challenges of managing finite water and energy resources continue to grow, new data, analyses, and models are needed to help water systems manage their energy use and operate more sustainably. This work offers three original contributions: 1) the discovery of annual, utility-scale energy intensities for public water supply from a panel survey of over 100 U.S. water utilities; 2) an empirical statistical model that accurately predicts a water system's energy use as a function of a few accessible variables and lends itself to fairer energy benchmarking; and 3) the development of a high-resolution method to model energy use within a water distribution network to inform energy management decisions at multiple scales. The survey showed an average water system energy intensity of 1,809 kilowatt-hours per million gallons (kWh/MG) but with substantial spread from 250 kWh/MG to 11,500 kWh/MG and with interannual changes up to 70%. These geographic and temporal variations should be considered in future work. The survey confirmed that a lack of adequate data is one of the greatest barriers to understanding energy-for-water demands. In the statistical model, the most important factors influencing energy use were found to be water system size, water source type, precipitation, and air temperature. By considering such internal and external variables, the model overcomes much of the difficulty in equitable energy benchmarking. The model is more accurate than those developed previously and uses more-accessible variables to estimate energy use, features that are useful when actual observations are unavailable. The technique for modeling energy intensities within a water system, built on extended-period hydraulic modeling, provided specific and actionable energy management insights. A case study with a real water system illuminated energy inefficiencies, and their solutions were validated through actual energy savings. Where water and energy interactions are complex, the method is a valuable analysis tool. Overall, the development of strong datasets, empirical relationships, and modeling techniques helps advance sustainable water supply from an energy perspective, with value to both researchers and practitioners.