Investigation of the Effect of Penstock Configuration on the Performance of a Simplified Pico-hydro System

This paper presents an investigation of the effect of penstock configuration with regards to area reduction on the performance of a simplified Pico-hydro system currently undergoing development. The system explores the utilization of the head developed by pumping water into an overhead reservoir and releasing it through a vertically oriented penstock. The concept in this study was introduced in the system in order to extend the duration in which continuous recycling of the water can be sustained while minimizing head losses and achieving higher power output. Five different configurations were obtained by joining pipes of diameters 76.2 m and 50.8 m with respective lengths in ratios of 5:2, 4:3, 3:4, 2:5 and 1:6 over a total height of 6.8 m with the aid of area reducers. The rotational speed of the alternator shaft, water level in the two reservoirs, output voltage and duration of test were measured and the flow rate, losses and net head were computed. The configuration with the ratio of 5:2 produced the highest rotational speed and voltage of 1810.2 rpm and 223.65 V respectively. This suggests that the use of a penstock configuration with a larger diameter forming the greater part of the total head will favor better power generation while ensuring sustained continuous water recycling which is critical to the operation of this system. The results show good promise for future penstock configuration for this system as a stand-alone, small and clean power generation system.