Hydropower plants capture the energy of falling water to generate electricity. A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy.
Hydroplants range in size from "micro-hydros" that power only a few homes to giant dams like Hoover Dam that provide electricity for millions of people.
The photo on the right shows the Alexander Hydroelectric Plant on the Wisconsin River, a medium-sized plant that produces enough electricity to serve about 8,000 people.
Parts of a Hydroelectric Plant
Most conventional hydroelectric plants include four major components (see graphic below):
How Much Electricity Can a Hydroelectric Plant Make?
The amount of electricity a hydropower plant produces depends on two factors:
Can I Figure Out How Much Energy a Dam in My Area Can Make?
Sure. It's not that hard.
Let's say that there is a small dam in your area that is not used to produce electricity. Maybe the dam is used to provide water to irrigate farmlands or maybe it was built to make a lake for recreation. As we explained above, you need to know two things:
Now all we need to do is a little mathematics. Engineers have found that we can calculate the power of a dam using the following formula:
Power = (Height of Dam) x (River Flow) x (Efficiency) / 11.8
For the dam in our area, lets say we buy a turbine and generator with an efficiency of 80%.
Then the power for our dam will be:
Power = (10 feet) x (500 cubic feet per second) x (0.80) / 11.8 = 339 kilowatts
To get an idea what 339 kilowatts means, let's see how much electric energy we can make in a year.
Since electric energy is normally measured in kilowatt-hours, we multiply the power from our dam by the number of hours in a year.
Electric Energy = (339 kilowatts) x (24 hours per day) x (365 days per year) = 2,969,000 kilowatt hours.
The average annual residential energy use in the U.S. is about 3,000 kilowatt-hours for each person. So we can figure out how many people our dam could serve by dividing the annual energy production by 3,000.
People Served = 2,969,000 kilowatts-hours / 3,000 kilowatt-hours per person) = 990 people.
So our local irrigation or recreation dam could provide enough renewable energy to meet the residential needs of 990 people if we added a turbine and generator.
Note: Before you decide to add hydropower to a dam, have a hydropower engineer review your calculations and consult with the local resource agencies to be sure you can obtain any permits that are required.