Site assessment
Application Criteria
1.7 m/s
> 1.0 m
1.25 m
3–4 m
Technical criteria
Flow velocity is the key factor
The most essential factor for the performance of the Rotor is the flow velocity of the water. With the final prototype, around 300 W can be generated at a flow velocity of approx. 1.7 m/s. The higher the flow velocity, the better: doubling the velocity increases the power eight-fold (P ~ v³).
Measuring the flow velocity on site
The surface velocity method has proven successful and is the simplest way to determine the flow velocity. A floating body (such as a piece of wood or paper) drifts with the river over a defined distance x (for example 10 m) down to the point where the Rotor is to be installed, and the time t needed is stopped. Repeat the measurement at least three times and record the results.
v = x / t
Although this method involves some inaccuracies, it is simple, can be done without measuring equipment and is sufficient.
Geometry of the water body
The Rotor has an immersion depth of 75 cm, so the flow depth should be greater than 1.0 m to ensure the Rotor is still flown through if the water level fluctuates.
The Rotor’s width is approx. 1.25 m, so the width of the riverbed does not matter substantially. Depending on the cross-section of the channel, it should be at least 3–4 m.
Further questions to be answered
- Is the discharge of the river constant throughout the year? How strongly does it depend on precipitation and rainy seasons, and how much does it drop in the dry season?
- Are there official data, or can the local community provide information?
- What are the options for security and ownership of a pilot installation?