Innovative hydrid solution for measuring discharge flowing in the pipe of medium head

Compagnie Nationale du Rhone manages 19 hydropower plants along the Rhone River. Six Francis turbines equip the Genissiat hydropower plant. The precise knowledge of turbinated flow rate, between 80 and 130m3/s, is one of the key factors for optimising energy production. Between 2008 and 2011, the six turbines were equipped: 4 measurement plans with crossing path, then 16 ultrasonic sensors for each turbine. Two gauging campaigns with about thirty ADCP were organised downstream of the plant. A difference of 3% was reached between US measurements and ADCP. A simulation using a CFD model confirmed that the flow can be either straight or swirling, depending on the flow conditions upstream of the water intakes. It also confirmed that the calculated US flow rate was less than 1% accurate subject to availability of the values of the 8 acoustic paths. The mapping of the efficiency of all turbine units shown a difference of 4 to 6 points. Then, a better distribution in each turbine of the total flow could lead to a gain of about 400k (sic) per year to be compared to the 800k (sic) of initial investment for the implementation of the US system.