Performance Analysis and Optimization of Undershot Water Wheel for Small-Scale Hydropower Applications

This study examines the performance of four undershot water wheels with different blade counts and profiles to identify the optimal setup for small-scale hydropower. The original wheel (nO24), with 24 flat blades and installed at the Kalinga canal in Dehradun, India, is compared to new (N) designs with 24 (nN24), 36 (nN36), and 48 (nN48) curved blades. All models have a 1-meter diameter, scaled down at a 4:1 ratio and tested in the turbine facility at the UPES Fluid Mechanics Lab, Dehradun. Design Expert 13 (DoE) software was used to optimize the number of experiments. Tests were conducted under varying flow rates, heads, and loads to evaluate hydraulic efficiency (η) and mechanical power (P). The nO24 wheel failed at higher loads (1.85 L/s), while the nN24 reached a maximum efficiency of 58%, improving by 6% over nO24. The nN36 outperformed all, achieving 65% efficiency and 1.35 W power output. In comparison, nN48 had reduced productivity from flow interference. Overall, nN36 had the highest efficiency-power trade-off with an increased power output of 27%. This study has shown that curved blade designs, in general, could be beneficial for undershot wheels used in decentralized, small-scale hydropower systems.