Hi. It’s Mr. Andersen and this is AP environmental sciences video 26. It is on hydroelectric
power, which is power created by the movement of water. If we look back in 1980 at the world
lead in the hydroelectric power, it was the United States followed quickly by Canada.
Nearly 300 billion kilowatt hours being produced mostly by dams. If we look at what has happened
over the last 35 years however we see a new country emerge. China. And the reason why
is the Three Gorges Dam. It is the largest dam on our planet. And they hope to produce
up to 10 percent of their electricity needs from this one dam alone. And what is hydroelectric
power? It is power through the movement of water. And we call it renewable. And the reason
why is it is really the sun. The sun is evaporating the water. It is moving up and as it falls
down again we can move that water through a turbine in most of the systems and we can
generate some electricity. The major types we will talk about are the run of the river
systems. Instead of having a dam they simply have a turbine on the river itself. So as
the water flows they can generate electricity. We have tidal systems. And we are starting
to bring on wave systems. And so as the water moves back and forth we can generate energy.
And then finally we have the most famous type, the water impoundment system or the dam. So
we essentially take a river, we build a wall on it and we can trap the water behind it.
Now we can regulate when we let the water out and when we let the water flow through
the turbines to generate electricity. And so what are some of the advantages of these
hydroelectric systems? We can reduce the amount of carbon dioxide into the atmosphere. Now
a lot of it is going to be produced as we are producing the dam, but once it is going
it is really cheap to maintain. If we look at flood control we can also regulate how
much water is moving down, especially in an impoundment system. And then you are creating
a lake so you can create a recreation system that can be used. What are some of the disadvantages?
Well these things fill in over time. So as the water flows into the impoundment system
it drops the silt and that is going to fill it up with solid material. So we either have
to remove that material or remove the dam. They are also limited. So if we look in the
US we pretty much used all of the viable places to have dams in our country. And since it
is disrupting flow it is disrupting natural flow of the river and anything that moves
in the river. For example spawning fish. And so how does this work? Well if you are familiar
with the water cycle you really know what is going on. We have evaporation, condensation,
precipitation and runoff. And as the water is running off we are capturing that energy
of the flowing water. We could also have tidal systems. So as the moon pulls on the water
on our planet and moves the water back and forth we can generate a little bit of energy
there as well. First type I want to talk about is the run-of-the-river system. Now this is
not a dam. It looks like a dam, it is just a very wide river. And so as the water runs
through it, it is generating electricity. What are some of the nice things about this?
We are not going to have that siltation problem. But the problem is that is only going to be
generating electricity when the water is actually flowing. In an impoundment system what we
have is a dam. We have a huge wall and then we just have a reservoir behind it. So we
have a bunch of water behind it. As the water is let through we can generate electricity
as it moves down to the river. And so you can see we have a huge amount of potential
energy on that side. And if you look at the size of that Three Gorges Dam you can just
start to imagine how much electricity can actually be generated. We also have tidal
systems. So in a tidal system the water is moving back and forth as the tides come in
and out. And so if we lower this down we can generate electricity. We also have a turbine
in there as well. What are the advantages? Well if we look at the Grand Coulee Dam, which
is the largest concrete structure that has ever been made on our planet. It is in Washington
state. Some of the advantages? It is a renewable form of energy. So the sun is actually generating
the lifting of that water and as it flows down we can tap some of that energy. We can
then use the water to irrigate crops in the nearby areas. This is an area that was actually
plagued by floods in the past. And so one of the reasons they put the Grand Coulee dam
there was for flood control. Did not really work so they had to work with other dams in
Canada to actually do that. We have created a giant reservoir behind here, a recreation
area that can be used. And then finally these are not carbon dioxide producers. We can reduce
our carbon dioxide emissions by running more hydroelectric power. What are some disadvantages?
Like everything, incredibly expensive to build and maintain. They destroy everything that
was there before. So this used to be a river that flowed up here. And so you are displacing
humans. You are covering up a lot of the Native American tribal areas as well. Siltation is
a problem. Silt is going to fill it in. Eventually it becomes useless. Fish can not move up.
So they can put fish ladders but they are not super effective. And then it is limited.
So there are limited places on our planet where we can actually use hydroelectric power.
And so did you learn the following? Could you pause the video at this point and fill-in
all of the blanks? Let me do that for you. It is a renewable form where water flows through
a turbine in these systems. That could be run-of-the-river, impoundment or tidal systems.
Some of the advantages, lowers carbon dioxide emissions, increases recreation and also decreases
floods. Disadvantages, siltation disrupts the flow, it is limited. And the big thing
is it is breaking down the natural flow of the river. And so spawning fish, for example,
like salmon can not make their way up. That is hydroelectric power. And I hope that was helpful.