Performance of vertical-axis pumps as turbines

Hydropower generation in water distribution networks (WDNs) is an attractive topic in the field of management of water systems. Pumps as turbines (PATs) allow coupling pressure control with power generation. Although PATs have several advantages over traditional turbines, theoretical and experimental studies are still required to overcome the reduced knowledge about their performances, especially for vertical-axis pumps. To this end, laboratory experiments on three vertical pumps running in reverse, with different number of stages and motor efficiency classes, were carried out and discussed. Results were compared with theoretical models available in the literature for horizontal PATs, with maximum errors around 20% and 30% for head and power curve, respectively. Analytical relationships for vertical PATs were proposed for better agreement. The dependence of performances by the number of stages and the motor efficiency class was also discussed.