The method of evaluating the economic efficiency of water supply systems with pumping stations equipped with tanks

Summary

A method of evaluating the economic efficiency of the water supply systems with pumping stations equipped with tanks is presented that provides for optimizing at the design stage water conveying systems in remote areas. These systems are characterized by: low energy efficiency because of the pressure loss during water discharge and low network reliability during bypass operation caused by pressure fluctuation. The method takes into account the specific features of simultaneous operation of two subsystems: pipeline and valving subsystem and booster pumping subsystem. The selection of net discounted flow rate over the life cycle as a uniform optimization criterion for all the subsystems is substantiated. It is stated that the economic and energy efficiency of the investment projects of upgrading water conveying systems is a function of the actual inlet pressure in the supply pipelines and depends on the engineering measures aimed to improve it. These measures include the use of valves for downstream pressure control, mini-hydropower units and auxiliary low head pumping stations. By the example of Parnas booster pumping station in St. Petersburg it is shown that the use of the developed method allows improving the reliability coefficients of the water supply system to P(t) > 0.95 with simultaneous 17% reduction of the net discounted flow rate over the life cycle. In this case depending on the actual inlet water pressure in the supply pipeline the energy consumption of a pumping station is reduced by 22–60%.

Key words

pressure , water supply network , energy efficiency , pumping station , control valve