A waterpower site assessment consists of measuring the amount of energy available from a particular waterpower situation.
Usually there is some idea what the power will be used for and how much will be needed.
This is accomplished by measuring two things:
- the amount of water available for use (including seasonal flow variations).
- how much pressure the water will have when it reaches the turbine (after friction loss in the pressure pipe).
Power = (water) Volume x (water) Pressure
as a formula in gallons (U.S.) and feet :
Flow (gallons/minute) x Net Fall (feet) x 0.18 x Efficiency (%) = Power (watts)
746 watts = 1 h.p.
or as a metric formula :
Flow (litres/second) x Net Fall (meters) x 9.8 x Efficiency (%) = Power (watts)
Measuring Water Flow
With small streams the flow can often be measured by channeling the flow through a short section of 4" diameter plastic pipe and timed while being run into a barrel of a known size. If the stream is too large to measure the entire quantity at once, the stream flow can be divided into two or more sections, more or less evenly, and then one section measured. Also, it is important to have a good idea about the low seasonal water flow if you want to use the power year-round. The Watermotor is easily adjusted for flow variations.
Usually fall is measured in steps by a process of using a level to sight a pole marked out in feet or meters. Beginning where the turbine will be located, one person holds the pole and the other goes uphill until they are even with the top of the pole as viewed through the sighting level. The process is repeated until the forebay tank height is reached. This method is very accurate when done correctly.