Optimal selection of pumps as turbines for maximizing electrical energy production

Abstract

A Pump as Turbine (PAT) is a renewable energy technology that can be a cost-effective and reliable alternative to hydraulic turbines in micro and small hydropower plants. In order to further favour PAT exploitation, a general procedure that allows the identification of the most suitable turbomachine to install is required. To this purpose, this paper develops a novel methodology aimed at selecting the best PAT that, among several alternatives, maximizes energy production. The methodology comprises two steps, which only require the knowledge of the best efficiency point of the considered pump and the hydraulic parameters of the site. The novel methodology is validated in this paper by calculating the electrical energy production of a simulated water distribution network coupled with several PATs, whose performance curves, both in direct and reverse modes, are taken from the literature. For the sake of generality, the considered turbomachines account for different geometrical characteristics, rotational speeds and operating ranges.

Optimal Selection and Operation of Pumps as Turbines for Maximizing Energy Recovery

“…• Validation of the methodology proposed in Manservigi et al [31]. The validation is performed by means of two sites that differ in both flow rate and head characteristics by strengthening the general validity of the proposed methodology;…”

“…In this paper, the best PAT (i.e., the one that maximizes the recovered energy) to install in a given site is selected by means of the methodology developed by Manservigi et al [31], which is sketched in Figure 1.…”

“…First, for each PAT, the runaway condition, i.e., at the minimum flow rate, is calculated to filter out those PATs that are not suitable for the site under analysis. To this purpose, Manservigi et al [31] derived Equations ( 1) and (2), which calculate the minimum flow rate of the PAT (Q r,T ) and the minimum head of the PAT (H r,T ) based on the BEP values of some PATs running in pump mode (i.e., Q BEP,P and H BEP,P ). First, for each PAT, the runaway condition, i.e., at the minimum flow rate, is calculated to filter out those PATs that are not suitable for the site under analysis.…”

“…Then, PAT selection is performed by calculating the PAT-site index (PSI), which is defined as in Equation (3) [31]:…”

“…This gap is filled by the current paper, which is aimed at (i) validating the selection methodology developed in Manservigi et al [31] and (ii) assessing the potential of exploiting PATs for energy recovery. To these purposes, two installation layouts are investigated.…”