FishFlow - Fish-friendly Screw Hydro Turbine
The FishFlow screw pump annex hydroturbine is a special version of the fishfriendly screw pump that can not only be used to pump water, but that can also function as a fishfriendly turbine to generate electricity. To function as a turbine the Archimedean screw is lowered until the waterlevel upstream of the screw is higher than the upper end of the screw. Consequently water flows into the screw and drives the turbine as a result of the waterpressure. A fishfriendly screw pump can be prepared to function as a turbine by fitting the pump with a direct-drive engine that can also function as a generator. In addition to this both the upper and lower ends of the screw are adjusted to guarantee fishfriendliness: at both ends of the screw the windings decrease in width until they seemingly merge with the casing that surrounds the screw.
The screwpump annex hydroturbine is fitted with a hydraulic system that can be used to change the position of the screw relative to the waterlevel. When in use as a pump, the upper end of the screw is elevated above the level of the downstream waterbody, whereas the upper end of the screw stands below the waterlevel during use as a turbine. In the latter position water will enter the screw and drive the turbine by gravitational force.
Because the screwpump is encased in a housing that rotates with the screw, no water is lost by leakage and the efficiency of the screwpump annex hydroturbine is very high.
