AXIAL FLOW TURBINES 4
As with the Kaplan turbine, an auxiliary system based on storage batteries or hydraulic accumulators will permit the turbine to be started up in the absence of outside power and, more importantly, to shut down in the event of overspeed caused by the removal of the external load, or by a fault condition.
Developments in recent years in the design of blades, guide vanes, actuating mechanisms and control technology have extended the head at which these machines can operate economically, down to 2 metres and possibly less.
This of course increases enormously the number of potential sites - particularly former mill sites where power can now be produced economically for local consumption or for sale to the national power distribution systems