Introduction to hydropower

Introduction to hydropower
To know the power potential of water in a river it is necessary to know the flow in the river and the available head.
The flow of the river is the amount of water (in m³ or litres) which passes in a certain amount of time a cross section of the river. Flows are normally given in cubic meters per second (m³/s) or in litres per second (l/s).
Head is the vertical difference in level (in meters) the water falls down.

Components of a typical high head hydro installation.
(click for enlargement) The theoretical power (P) available from a given head of water is in exact proportion to the head H and the flow Q.
P=Q × H × c       c = constant The constant c is the product of the density of water and the acceleration due to gravity (g).
If P is measured in Watts, Q in m³/s and H in meters, the gross power of the flow of water is:
P=1000 × 9.8 × Q × H This available power will be converted by the hydro turbine in mechanical power. As a turbine has an efficiency lower than 1, the generated power will be a fraction of the available gross power.
 
 


Different sizes hydropower installations Hydropower installations can be classified as follows:
 

name	description
Large	all installations with an installed capacity of more than 1000 kW (according to some definitions more than 10,000 kW)
Small	general term for installations smaller than 1000 kW (or < 10,000 kW). Also used for installations in the range between 500 and 1000 kW.
Mini	capacity between 100 and 500 kW
Micro	hydropower installations with a power output less than 100 kW (or less then 1000 kW)