Design of a Cross Flow Turbine for a Micro-Hydro Power Application

The total installed capacity of the hydropower stations in Pakistan is about 7,000 MW which is about 20% of the total available hydro power potential. For possible micro-hydro stations, a potential of about 1300 MW exists at a number of low head and high flow rate sites. Work has been reported by Chattha et al. [1, 2] related to installation of a micro-hydro power station at one of the typical sites. An axial flow pump-as-turbine (PaT) was installed to generate electrical power at the micro-hydro station. The site selected for this work is quite typical and efforts are now being made to utilize the maximum potential of the site conditions. The PaT only utilizes about half of the available flow of water and a spillway was constructed at this site to divert the excess amount of water. The diverted water flows back to the main stream after bypassing the PaT. Work is now being carried out to explore the installation of a turbine in the spillway to harness the energy potential of the diverted water stream. This work includes selection, design, fabrication and installation of a turbine in order to generate electrical power utilizing the energy of water diverted to the spillway. A 100 ft³/sec flow rate with about 11 ft head is available at the spillway side. Considering these site conditions and indigenous fabrication expertise, cross flow type turbine has been selected for installation. Cross flow turbines are being manufactured in Pakistan and are usually quite successful for micro-hydro systems. Based on the available site conditions, a cross flow turbine has been designed. The diameter and length of the turbine runner have been calculated. Furthermore, the number of blades and radius of curvature have been determined along with other design parameters. The designed turbine is expected to produce about 50 kW of power. The complete design of the turbine, based on the available site conditions is presented in this paper.