Pump Efficiency Analysis for Proper Energy Assessment in Optimization of Water Supply Systems

Abstract

Water supply systems need to be designed accounting for both construction and operational costs. When the installation requires water pumping, it is key for the operational costs to know how well the pump can perform. So far, pump efficiency has been considered using conservative values, in the absence of a better estimation. The aim of this paper was to improve determining the energy costs by clarifying what the value of the pump performance should be. For this, 226 commercial pumps were studied, registering the efficiency at the optimum operating point, as well as other variables such as the flow rate, height, and pump type. As a result, a strong relationship between the pump performance and the discharge flow was spotted. That allowed the generation of an empirical curve, which can be used by designers to anticipate what pump efficiency can be expected. The results are used in a simple case study using the Granados Optimization System. These achievements can be implemented in design policies for a better energy assessment in the optimization of water supply systems.

Optimization of the Design of Water Distribution Systems for Variable Pumping Flow Rates

“…As a general rule, it was assumed that the larger the pump is, the better performance it had. Nevertheless, Martin-Candilejo et al [32] have addressed this issue in depth concluding that there is a direct relationship between the flow rate and the pump efficiency: The pump efficiency is better for greater discharge flow rates, reaching an asymptote for 90%. Figure 1 is a scheme of the cost distribution depending on the pipe diameter.…”

“…With the exception of the pump performance µ B , the other variables in the previous equation are actually data: V is the total volume to be pumped, p is the unit price of the energy that has been hired, and f A is calculated from the discount rate i, the service life n U of the water pipeline and the construction period n C . Regarding the engine efficiency µ M , although it varies theoretically depending on the engine model chosen and the operating point of the pump, the variations in engine performance are so small that it can be considered constant across different models and manufacturers [32]. Therefore, the above equation can be simplified by grouping all the data and parameters that have fixed values in the coefficient KC E1 , which can be considered constant for each case analyzed:…”

“…Therefore, to apply this method it is necessary to know the maximum performance that pumps can reach. Martin-Candilejo et al [32] studied the optimum pump efficiency of 226 commercial pumps. After their assessment, they obtained an empiric relationship between the optimum µ B and the flow rate, q.…”

Use of Fixed and Variable Speed Pumps in Water Distribution Networks with Different Control Strategies

“…These previous antecedents could incentivize researchers such as Casasso et al [3] and Candilejo et al [4] to develop strategies to improve energy efficiency in water infrastructures that include pumping stations. The Environmental Protection Agency (EPA) [5] defined several measures to save energy in pumping stations, such as reduced pressure service, managed pressure service, maximized efficiency of the system, and adequate pump and control modes selections.…”

“…However, using more FSPs than the minimum required in the system generates significant benefits in energy costs because pumps improve their efficiency, as was demonstrated by Walsky and Creaco [33]. Later, Candilejo et al [4,34] improved a methodology to estimate pump's performance for a proper design of a pumping station in order to reduce operational costs and then create a methodology for the optimal design of a water pumping system with variable flow rates.…”