What is hydroelectric energy?
Water is pretty powerful stuff! You know this if you have stood in a flowing stream and felt the water rushing past you. Or, if you have gone whitewater rafting in a raging river. Even ordinary images of a place such as Niagara Falls assist you in appreciating just how strong moving water is. This is not a new observation, and water has been used to produce different forms of energy for a very long time. When electricity is generated from flowing water, this is called hydroelectric energy, and the prefix ‘hydro’ refers to water.
Hydroelectric energy is considered a renewable energy resource because it’s an energy resource that regenerates in a short time period. You can think of this like the hair on your head. If you get a bad haircut that you don’t like, you don’t have to worry about it too much because it will grow back in a reasonable amount of time. However, if you end up losing an arm, you definitely cannot regenerate that! Your hair is actually a renewable resource, whilst your arm is a non-renewable resource.
Wind, sunlight, and heat generated from the earth are the same types of renewable energy resources. Just like you can’t stop water from flowing, you can’t stop the sun from shining or the wind from blowing. The resource ‘renews’ itself as it is used, and unlike things such as minerals and metals, does not occur on Earth in a limited supply.
Hydroelectric energy is a very important energy source, both nationally and worldwide. About 19% of the world’s total electricity production comes from hydroelectric energy and about 7% of the power in the U.S. When we look at hydroelectric energy for the U.S. in terms of renewable energy sources (so comparing this to things like solar power, wind power, geothermal energy and biofuels), it makes up 96% of renewable energy electricity production. That means that almost all of our energy production that comes from renewable energy sources comes from water!
Water generates electricity
So, how exactly is electricity generated from water? This normally happens through a hydroelectric dam that is constructed along a flowing waterway. Think of the water at Niagara. The water flowing over the falls is travelling faster than the water approaching the falls. As the water moves downhill, it gathers power and actually increases speed.
To take advantage of this, dams are constructed along the waterway where there is a large elevation drop. This is exactly why you wouldn’t expect to find dams in flat places like Florida, but would expect to find them in the hilly, mountainous regions of the Southwest U.S.
Just like going down a slide at a playground, water is forced downhill by gravity and then it gradually picks up speed as it flows. Inside the dam there are turbines that are rotated by the moving water – exactly how a pinwheel gets rotated by the wind blowing by.
The rotating turbine chutes are usually linked to a generator, and the rotating of the turbines end up creating electricity right inside the generator. The generator is connected to power lines, which transmit the electricity to homes and buildings just like they do with coal-fired and natural gas power plants.
Just like wind blowing past the Catherine wheel is not affected by the Catherine wheel itself, the water flowing by the turbines is also not affected because it runs through the dam. It literally flows on downstream as if there is nothing which has happened. Well, I’m sure you can now see why this is such a widely used and valuable energy resource worldwide! However, with every source of energy, there are pros and cons. Let’s look at the benefits and drawbacks that come with harnessing the amazing power of moving water.
Pros and cons of hydroelectric energy
As you already know, hydroelectric energy is beneficial because it’s a renewable resource. The water is not affected as it flows through the dam and spins the turbines – water will flow whether there’s a dam there or not! This also means that there is minimal pollution, unlike the air and water pollution generated from coal and nuclear power plants.
Because water normally flows along naturally, we also don’t really have to create any water to go through the dam. Water is provided by nature, and we simply have to sit back and let it do all the work! This also means that maintenance and operational costs are relatively low for the dam itself.
One reason that hydroelectric energy is so popular is its reliability. Wind power is great, but if the wind isn’t blowing, you don’t generate any electricity. Solar power has a similar issue. If in any case the sun is not shining, then you are not generating any kind of electricity from the sunlight. However, dams are specially designed to hold a lot of water behind them. This basically provides a steady, constant flow of energy from the water that runs through it. So instead of depending on rainfall to deliver water, we all know very that the water will be there just waiting to rotate those turbines in the dam.
Whilst hydroelectric energy can be an extremely beneficial renewable resource, there are also certain drawbacks to using water to produce electricity. Whilst the costs of maintaining are low after the dam is built, they’re very expensive to construct and require large up-front investments.
And you know those reservoirs behind the dam? For the most part, these are a steady, reliable source of water. But they are dependent on water coming from their own sources, such as rain. If it doesn’t rain, the reservoir may dry up. It’s like having a slow leak in your bathtub. If in any case you sit in there long enough and you do not turn the water back on to re-fill the tub, then eventually you will be sitting in a dry tub, which certainly does not work very well!