# If the river flows faster can it produce more power?

• Asked on March 25, 2010

Well, sure it does. The way hydroelectric power works is that it captures the kinetic energy of the river’s movement and converts it to potential energy for electricity. If you have a faster river flow, then the turbines that are turned, which capture the energy, will turn faster, and more energy will be collected.

Two other ways of capturing more of the kinetic energy of water is 1) if the water “falls” quickly as in a waterfall, since gravity accelerates the rate of water flow and 2) if you force water through increasingly more narrow pipes, as this increases the pressure and the velocity of the water.

Yes. Every energy plant uses turbines to produce electricity, even nuclear power plants. These generally heat water to boiling point and use the steam to turn turbines that create electricity. The material that is used to boil water changes only. Hydroelectric works much the same way but instead of using the upward steam movement of the water, it uses the downward liquid form of the water, which makes it much more powerful. The reason we can’t apply hydroelectric plants on lakes is because the lakes have a very slow moving water. But wave generators are being developed to harness these.

No.  The rate of the river has less to do with power generation than you would think.  Power generation depends on momentum being transfered to a turbine.  More momentum can be achieved by adjusting the flow rate, which is amount of water per unit time.  It is defined as the cross-sectional area of the flow multiplied by the velocity of the water.  Flow rate is understood more easily if you think about a large tank of water, such as a water tower, being punctured through its wall by something like an icepick.  The surface of the water tower will appear not to move, but a jet of high-momentum water will be projected out of the puncture.

In order to increase momentum, we can channel a large amount of water from the river into a tube at the end of which is a turbine.  This means that a river with a large amount of water will produce more power, whereas a fast river will produce less because it carries less water.

The old adage applies to hydroelectricity output: “Still waters run deep”.  Deeper water = more power.

Think of it this way: if a faster river produced more power, the giant man-made lakes behind hydroelectric dams such as Lake Mead and Lake Roosevelt would be problems, since they do not move at all!