What is measured?

The experimental setup includes probes and meters to determine at every instant the power extracted by the hydrokinetic turbine:

• A torque meter is installed on the rotating shaft, allowing to measure torque on the turbine side, just before the gearbox and the generator.
• A resolver is fixed at one end of the rotating shaft, measuring the rotating speed with high accuracy.
• Accelerometers are used to assert the pontoon stability.
• Water velocity probes are fixed underwater in order to measure precisely the boat speed.

These measurements are recorded synchronously many times per second on a laptop computer.

The power extracted is calculated with the product of the instantaneous torque and instantaneous rotating speed:

Power [Watts] = Torque [Newton-meters] x  Rotation speed [radians/second]

The average power extracted can then be computed and compared to the available power in the water current, which is proportional to the cube of water flow velocity (the pontoon speed). One obtains the turbine power extraction efficiency as the ratio of the power extracted to the available power.