Correction of the <i>EPANET</i> Inaccuracy in Computing the Efficiency of Variable Speed Pumps

Abstract

One attractive possibility for saving energy in water distribution systems is the introduction of variable speed pumps (VSPs). However, to assess the cost effectiveness of using VSPs, a correct estimate of VSP energy consumption, and therefore efficiency, is essential. This task involves estimating the efficiency of various components: pump, motor, and variable speed drive. Hydraulic solvers, which are used to check the hydraulics of the system, usually use the affinity laws to describe the pump behavior in a VSP pumping system. This paper demonstrates the inaccuracy of the popular hydraulic solver EPANET 2, which does not properly take into account the affinity laws in the efficiency computation when the speed changes for VSP operations. The correction of the code is presented and an additional improvement of the toolkit to directly retrieve the efficiency is introduced.