The first thing to ask when someone tells you the head and flow for their site, is “when?” because head and flow are constantly changing at every site and sometimes quite drastically.
Therefore when someone gives us a simple figure for head and flow it is possible to provide a “spot” measurement of power generation potential but it should be taken in context that it is just one estimate of power generation potential at a single point in time.
To determine the optimal or real world power generation potential the duration of all heads and flows experienced at the site must be considered.
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It is quite easy to estimate power available in the water at a point in time by using the following formula:
Gross Hydraulic Power (kilowatts) = 9.81 x Q x H
Q = Flow (Cubic meters per second)
H = Head (Meters)
However, what do you do if measurement at another time produces a number 10 to 15 times higher – which is quite possible?
The power potential is a range and the selection of the most optimal system size must be done.[/info_box]