Abstract
Very low-head water facilities are the salient resources for the development of hydropower using non-conventional hydro turbines. This review paper is concentrated on the collection and selection of turbines suitable for hydraulic heads between 0.5 and 3 m only defining them as the ultra-low-head. Turbines reviewed are feasible for new or existing infrastructure, drinking or waste-handled water, and able to function as a single unit, or parallel unit installation. From several earlier research and communication with 25 turbine manufacturers, thirty-eight different hydro turbines are discussed in this review with their operating range in most cases. The novelty of this review includes providing a comprehensive explanation of all the non-conventional hydropower turbines which were scattered in different literatures and providing a selection chart for classification of turbines. The distinct chart with four classification bases for hydro-static energy conversion of ultra-low-head turbines has been concluded and launched the category 'mode of action' to be the most comprehensive. The existing literature cover different basis for the selection but includes only few nonconventional turbines. This enforces the development of a specific selection chart comprising all such turbines with global scenarios.