Coupled Electric and Hydraulic Control of a PRS Turbine in a Real Transport Water Network

Abstract

Although many devices have recently been proposed for pressure regulation and energy harvesting in water distribution and transport networks, very few applications are still documented in the scientific literature. A new in-line Banki turbine with positive outflow pressure and a mobile regulating flap, named Power Recovery System (PRS), was installed and tested in a real water transport network for the regulation of pressure and flow rate. The PRS turbine was directly connected to a 55 kW asynchronous generator with variable rotational velocity, and coupled to an inverter. The start-up tests showed how automatic adjustment of the flap position and the runner velocity variation are able to change the characteristic curve of the PRS according to the flow delivered by the water manager or to the pressure set-point assigned downstream or upstream of the system, maintaining good efficiency values in hydropower production.

Hydropower Case Study Collection: Innovative Low Head and Ecologically Improved Turbines, Hydropower in Existing Infrastructures, Hydropeaking Reduction, Digitalization and Governing Systems

“…Water distribution networks have been designed to meet the variable consumer demands keeping the pressure within an acceptable pressure range, to provide a reliable service. At the end of such long pipelines, PRVs are usually installed to reduce excessive pressure upstream distribution to end-users [55]. The pressure excess that had to be dissipated can be transformed from a problem to an income, with a double goal in economic and ecologic terms, replacing the valves with hydro generators.…”

Design of Reliable and Efficient Banki-Type Turbines

“…We applied the proposed impeller design in a PRS turbine already installed in a pressure regulation node, named Fontes Episcopi, which is part of a larger water transport network of Sicily (Italy), named Gela-Aragona. The installed PRS turbine was designed with the following input parameters: H = 100 m, Q = 100 L/s, and ω = 1500 rpm, and its performances were reported in a previous work by some of the present authors [8]. Using the same design parameters, a new PRS turbine, called the PRS2 turbine, was designed with the proposed procedure.…”

“…Using the same design parameters, a new PRS turbine, called the PRS2 turbine, was designed with the proposed procedure. Assuming λmax= 110°, the impeller diameter D and the width B were found to be to 234 mm and 55 mm, respectively, by using the design methodology described in [7][8][9].…”

“…Energy recovery from mini-hydro turbines with positive outlet pressure installed in transport and distribution water pipes has recently gained major attention in the scientific literature, especially when the device can supply the same function as the valves [1]. These turbines are usually pumps used in reverse mode (pumps as turbines, PATs, see [2]), bulb types [3,4], or Crossflow-type turbine [5,6], like the power recovery system (PRS) [7][8][9]. The main advantage of the PRS, with respect to the other types of turbines, is that it has the capacity for hydraulic regulation by means of a mobile flap that can change the characteristic curve of the turbine, while still maintaining good efficiencies within a large range of head jumps and flow rates (see in Figure 1 a section of the PRS normal to the turbine axis).…”

“…The main advantage of the PRS, with respect to the other types of turbines, is that it has the capacity for hydraulic regulation by means of a mobile flap that can change the characteristic curve of the turbine, while still maintaining good efficiencies within a large range of head jumps and flow rates (see in Figure 1 a section of the PRS normal to the turbine axis). Design criteria for the impeller diameter and the width B can be found in [7][8][9].…”