T15 Turbine, is based on a consequent optimizing process conducted over many years. Numerous computer based modifications of the hydraulic profile were empirically tested in the laboratory of the Institute for Hydraulic Machines of Stuttgart University.
The test turbine of 29 kW had a runner diameter of 300 mm, and the sophisticated measuring facilities guarantee for reliable results. The achieved improvements were the basis for the redesign of the turbine. Three models, with the standard diameter of 300 mm and runner diameters of 400 and 500 mm, for larger flows at low head, were developed. It is now possible, even with the limitation of simple production methods, to build very reliable and long lasting turbines with competitive high efficiency.
Big efforts were made to reach a good part load efficiency. With only 20% of the rated flow, the efficiency is still over 50%. This allows to reduce costs, because a single cell CFT will be sufficient in the majority of the applications. Double cell CFTs have two independent guide vanes, and require two regulation devices as well, which increases cost.