These vertical axis units well fit with low head, from 2 to 30 meters, and relatively high flow situations, showing a very wide high efficiency field thanks to their double regulated mechanisms: accordingly to the available flow, the distributor and the runner blades (from 3 to 5) take a position following a collimation curve, allow to obtain the maximum power production.
Are available also single regulating Kaplan turbines, where the runner blades can’t be moved: these cheaper units are suitable for steady flow conditions, cause the significant efficiency drop when working in different from flow design condition. Each turbine should be calculated accordingly to the site characteristics (head and maximum flow), looking for the optimal combination of shaft speed and overall efficiencies.
