New Expressions to Apply the Variation Operation Strategy in Engineering Tools Using Pumps Working as Turbines

Abstract

The improvement in energy saving aspects in water systems is currently a topic of major interest. The utilization of pumps working as turbines is a relevant strategy in water distribution networks consisting of pressurized pipes, using these machines to recover energy, generate green energy and reduce leakages in water systems. The need to develop energy studies, prior to the installation of these facilities, requires the use of simulation tools. These tools should be able to define the operation curves of the machine as a function of the flow rate. This research proposes a new strategy to develop a mathematics model for pumps working as turbines (PATs), considering the modified affinity laws. This proposed model, which can be input into hydraulic simulation tools (e.g., Epanet, WaterGems), allows estimation of the head, efficiency, and power curves of the PATs when operating at different rotational speeds. The research used 87 different curves for 15 different machines to develop the new model. This model improves the results of the previously published models, reducing the error in the estimation of the height, efficiency, and power values. The proposed model reduced the errors by between 30 and 50% compared to the rest of the models.

Analysis of Applicability of CFD Numerical Studies Applied to Problem When Pump Working as Turbine

“…The use of these machines is justified when the heads are low and the flow has high values [75]. In many real situations, the axial machines would adapt correctly, but the lack of previous experimental tests causes the water managers to have few analytical expressions to estimate the energy analysis using axial PATs [13].…”

“…Mainly, this error was upper when the analyzed variable was the efficiency. This parameter was difficult to make estimations for both analytical as well as numerical analysis, but it is crucial to obtain accurate energy studies [13]. Besides, it should be noted that hexahedral structural are preferred to tetrahedral because of their efficiency in optimizing the space in which a smaller number of cells is required to solve the geometry.…”

“…The different methods used are theoretical analyses, mathematical models, numerical simulations with CFDs, experimental tests, and empirical expressions. As an example of mathematical analysis, Plua et al [13] proposed a new PATs prediction model that can be used in different hydraulic simulation software. However, the majority of the previous studies only focused on the operation under fixed rotational speed, whereby published researches showed the need to operate under variable rotational speed considering both hydraulic and electrical regulation [14].…”

Bypass Control strategy of a Pump as Turbine in a Water Distribution Network for energy recovery

“…Therefore, several models have been developed considering different approaches for this purpose [6]. The most common approaches are based on the development of empirical models [7,8,9], 1D models (unknown geometry) [10] and Physic-Based models (known geometry) [11,12]. Defining the control strategy of a PaT in a WDN is not immediate and requires in-depth analysis on the hydraulic load variability in order to maximize the energy production.…”

Pumps as Turbines (PATs) by Analysis with CFD Models

“…The main advantages of PATs are availability [1], short delivery time, long service life, and economic feasibility, construction and, maintenance advantages. Different types of analysis have been carried out to predict the characteristics curves of pumps working in turbine mode to select the machine to be placed in the systems [13], [14]. However, this task has not yet been solved for the existing range of possibilities.…”