Design and performance of composite runner blades for ultra low head turbines

Abstract Stream sites are abundantly available for small, ultra low head, hydropower applications with minimal environmental and ecological impacts compared to large-scale hydropower projects. However, little attention has been paid to these resources because of the relatively high weight and deployment costs of small turbines compared to the amount of power generated, which results from the use of stainless steel (SS) as the turbine material. Therefore, this study investigated the potential of replacing the machined SS blades in a small propeller-type turbine with light-weight composite blades injection molded from a fiber reinforced polymer. Using computational fluid dynamics models and finite element analysis, a carbon fiber-reinforced thermoplastic was selected from three candidate composite materials for its lower density and smaller blade tip displacement. Injection molded blades using this material were then manufactured and tested in a lab-scale turbine performance test loop to compare with the SS blades of the same design. With the same flow rates, the composite turbine blades generated more power but required a slightly higher head (∼0.08 m) than the SS blades. Both the composite and SS blades displayed similar peak turbine efficiencies, demonstrating the viability of the composite material in replacing SS from the perspective of power-generation performance.