In post-industrial Europe, there is no turbine design for small and very small hydropower potentials in the low and medium head range that is compact, reliable and at the same time economically viable. Based on standard reverse-rotating centrifugal pumps as turbines (PaT), a new concept has been developed how, with the use of modern production methods and standard components from building services engineering and other renewable energy technologies, a cost-effective hydro turbine - called PaT-Francis - can be built, which is capable of handling a variable flow thanks to the use of a guide vane. This greatly extends the field of application of a PaT. Weak points of small Francis turbines, such as strongly decreasing efficiency in part-load operation or the susceptibility to clogging, have been improved with variable speed operation or a special flushing programme respectively. In a pilot project in the Zürcher Weinland, a 2.5 kW PaT-Francis was installed and extensively tested during the first year and a half of operation. The practically uninterrupted operation of the plant confirms the high reliability that was intended with the chosen design and equipment. The pilot plant's output of 2.5 kW at 80 l/s flow rate and a maximum efficiency of 74.5% for the PaT-Francis turbine are within expectations, considering the small size. However, potential for improvement could be identified in the overall efficiency, which is only a maximum of 64% because the generator and frequency converter were chosen too large. The PaT-Francis concept is suitable for applications in the power range up to approx. 50 kW and, thanks to its compact and noise-reducing design, can be used to exploit various potentials in the midst of inhabited areas in historical canals but also in fish ladders.
