Methodology for evaluating city-level energy footprint for water distribution systems

Abstract

Water distribution is a major contributor to energy use for water supply. Reducing network pressure can decrease energy use for centralised distribution while simultaneously increasing energy use for high-rise pumping. This study describes a method of calculating and optimising energy for water distribution at city level that incorporates both centralised and high-rise distribution and the pressure trade-off between them. The methodology is applied to 82 case cities in China and is used to judge whether China’s recommended minimum pressure regulation leads to unnecessarily high energy use in certain cities. Results show that 63 of these cities could save energy by reducing the minimum and average pressure used to distribute water, with energy savings of up to 28% of total energy for water distribution. The methodology was also used to investigate how the distribution of households in buildings of different heights affects energy use for water distribution. Adjustments to pressure had greater impact on energy use and adjustments to building height distribution had less impact on energy use in cities with fewer high-rises. The methodology provides a way for urban planners, government and water companies to reduce energy use for urban water distribution. For the case of China, the results suggest a city-specific minimum pressure recommendation is more suitable than the existing nationwide recommendation.