AN IWIDGET ANALYTIC FOR OPTIMAL EQUIPMENT REPLACEMENT BY MINIMIZING LIFE-CYCLE COSTS UNDER DEMAND UNCERTAINTY

摘要

iWIDGET is an EU research project to improve water efficiency through the use of information and communication technologies with a special focus on the role of smart water meters for understanding consumption and improving system operations. This paper presents an iWIDGET analytic method to estimate the optimal times to replace smart meters in a water supply network considering life-cycle costs (LCCs) and the uncertainty in water consumption. The method separately provides suggested replacement times for smart meters by minimizing the LCCs, where the dominant costs are associated with non-revenue water due to loss of metering accuracy. Deterministic and robust formulations of the method are presented. The latter incorporates the uncertainty in the water demand estimated using demand measurements from the iWIDGET central system. Other important parameters in the modeling approach are the deterioration curves of equipment that describe the decay of functional performance and the economic variables associated with the investment on new meters. The method applies an economic analysis to calculate the present value of the replacement considering all the LCCs and estimates the statistics at the time that yields the minimum present value of total costs. The method is implemented and tested on a sample of iWIDGET smart meters. Our results illustrate the potential benefits in reducing the life-cycle costs of smart meters when demand uncertainty is considered in the optimization of replacement schedules.