Video: Understanding the Advantages of Hydroelectric Power from Dams

Which of the following correctly describe the advantages of building a hydroelectric dam? [A] Building a hydroelectric dam releases no carbon dioxide into the atmosphere. [B] Building a hydroelectric dam releases no methane into the atmosphere. [C] Hydroelectric dams can respond quickly to changes in energy demand. [D] Hydroelectric dams are very cheap to build. [E] The running costs of a hydroelectric dam are very low.

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Video Transcript

Which of the following correctly describe the advantages of building a hydroelectric dam? a) Building a hydroelectric dam releases no carbon dioxide into the atmosphere. b) Building a hydroelectric dam releases no methane into the atmosphere. c) Hydroelectric dams can respond quickly to changes in energy demand. d) Hydroelectric dams are very cheap to build. e) The running costs of a hydroelectric dam are very low.

Okay, we’re being asked to describe the advantages of building a hydroelectric dam. Now, the starting point for most hydroelectric dams is a river. And let’s say this is our river right here. When we create a dam, we put a big concrete wall in the way of the river. The effect of this is that the river water starts to pile up behind this dam. And when that happens, it’s not uncommon for flooding to occur. After all, before the dam was in place, the water in the river just occupied this narrow riverbed. But now, it’s all collected up in a gigantic pool, called a reservoir.

This means that land that used not to be underwater now is. And this includes the plants that grow on that land. When these plants are underwater for long enough, they start to rot. And in the process, they release greenhouse gases, both methane and carbon dioxide. As we look at our first two answer options, we see that these options claim that building a hydroelectric dam releases no carbon dioxide and no methane. But the decaying plants released both of these gases. And along with that, the production of all the concrete needed to build the dam releases CO2 as well.

So building a hydroelectric dam does release carbon dioxide, which means we won’t choose option a as an advantage. And it also tends to release methane. So we won’t choose option b. Option c says that hydroelectric dams can respond quickly to changes in energy demand. And if we think about it, this dam can be designed so it releases different amounts of water from the reservoir. And it’s the amount of water running through the dam that affects how much electrical energy the facility produces. So if there’s a change in energy demand, either an increase or a decrease, the dam can be changed so that the water flow through it responds to that. And this can happen very quickly, as quickly as moving a mechanized gate. So option c does correctly describe an advantage of building a hydroelectric dam.

Let’s move on to options d and e. Option d says, “Hydroelectric dams are very cheap to build.” Well, when we consider the manufacturing costs of building a gigantic wall of concrete and then installing the turbines and the generators that help produce electricity, on the front end, when they’re being built, hydroelectric dams are actually very expensive. They’re very expensive to set up, to build. But they’re inexpensive to maintain once they’re built. We won’t choose option d as an answer choice.

The last option says that the running costs of a hydroelectric dam are very low. Once the dam is built, the turbines and generators are installed, and the reservoir is filled, not much needs to happen from then on for the hydroelectric facility to generate electricity. The costs at the start are very large. But once electricity is being produced, it can be produced fairly inexpensively from then on. The cost of maintaining a hydroelectric dam is low. So in describing the advantages of building a hydroelectric dam, one advantage is these dams can respond quickly to changes in energy demand. And another is that their operating costs are very low.

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