[01] Obinna Ajala Chinyere, National Agency for Science and Engineering Infrastructure (NASENI), Idu, Industrial Area, Abuja, Nigeria. [02] Nkiru Rosemary Obasih, National Engineering Design Development Institute (NEDDI), Nnewi, Nigeria. [03] Emmanuel Osiewundo Ojo, National Agency for Science and Engineering Infrastructure (NASENI), Idu, Industrial Area, Abuja, Nigeria. [04] Chidozie Okonkwo, National Engineering Design Development Institute (NEDDI), Nnewi, Nigeria. [05] Edward Udoka Mafiana, National Engineering Design Development Institute (NEDDI), Nnewi, Nigeria.

The penstock constitutes a major expense in the total Small-Hydro budget. It is therefore important that the pipe used is carefully chosen to minimize both lifetime running costs and initial purchase cost. Basic Design parameters for the penstock were gotten through field survey in 2015 for parameters like the gross head and flow to be 15m and 0.26m³/s respectively. The penstock was designed using the Un-Plasticised Polyvinyl Chloride (uPVC) material owning to its benefits over steel pipes, such as cost, roughness value, ease of installation, transportation etc. After subjecting different sizes of uPVC pipe internal diameter through iterative process to get the best diameter that produces a percentage head loss of less than 4% European Small Hydropower Association (ESHA) standard, the 442mm diameter penstock was selected because it has the least head loss of 2.5%, even though the 397mm diameter also met the condition having a 4% loss. Parameters like the friction loss, net head, thickness of pipe, safety value, wave velocity, diameter of vent, operating pressure were gotten to be 0.38, 14.62m, 27mm, 4.1, 384m/s, 0.07m, 8.2bar respectively. Finally the cost benefit analysis was computed to show the effect of using a larger diameter penstock over the smaller diameter that gave a cost benefit ratio of 1.4, an indication that shows that for every extra one naira (Nigerian Currency) spent on the penstock, a benefit of 40kobo (Nigerian Currency) is achieved. This shows that the larger pipe diameter if used will yield positive returns on the long run.

Head Losses, Friction Losses, Diameter of Penstock, Cost

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