Once you’ve estimated the head and the average flow, you can estimate the power output as detailed below.
The maximum power of the hydro system can be roughly estimated as:
Head X Flow X 5 = kW
The head is in metres and the flow in metres-cubed per second.
The micro-hydro power systems supplied by Hydro Generation typically range from 5kW - 250kW. A system smaller than 10kW however is unlikely to be cost effective.
A River which is as large as the photo shown in Category 5 above.
Estimate the average flow rate to be 4 m3/s.
The head at the site is 2 metres. Therefore the estimated power output would be:
Power (in kW) = Head X Flow X 5 = 2 (metres) x 4 (m3/s) x 5 = 40 kW
This is a reasonably good size for micro-hydro system.
A fast-flowing stream in a back garden, but no significant drop apart from the slope of the land, which falls 2 metres over a 100m length.
From the table Category 1 above estimate the average flow rate at 25 litres/second (0.025 m3/s).
The power output would be:
Power (in kW) = Head X Flow X 5 = 2 (metres) x 0.025 (m3/s) x 5 = 0.25 kW
This is not enough power to make a micro-hydro project economically viable.