Prediction of Global Efficiency and Economic Viability of Replacing PRVs with Hydraulically Regulated Pump-as-Turbines at Instrumented Sites within Water Distribution Networks

Abstract

Pressure management in water supply pipe networks using conventional pressure reducing valves (PRVs) results in the dissipated energy being lost. In pursuit of more energy efficient solutions in the sector, researchers are exploring the technological and economic feasibility of replacing PRVs with low-cost hydroelectric converters such as pump-as-turbines (PATs). The present study addresses two problems: (1) is it possible to accurately estimate the energy recovery potential of a PRV site using only the statistics of its recorded operating conditions? and (2) can we define a bound representing minimal average operating conditions at PRVs for which their upgrade to PAT is expected to be economically viable? The first problem was addressed by calculating descriptive statistics of yearly recordings of the operating conditions at 38 real-world PRVs from Ireland and Spain, and carrying out linear least-squares regression analysis in which the statistics were used as predictor variables. The results imply that global plant efficiency can deviate up to 33.33% depending on the level of variation of the operating conditions, and that a realistic value of the expected global plant efficiency is around 0.4277 rather than 0.65 that was used in some of the previous studies. To address the second problem, the study first identifies the range of variability of the operating conditions and total installation costs for 340 hypothetical PRV sites whose average operating points (OPs) were evenly distributed across the investigated domain. The optimal net present value (NPV) was assessed for all hypothetical sites and their variability scenarios. The results suggest that there is a high probability that sites with the gross hydraulic power of 12 kW or larger will be economically viable for the upgrade.