What Are Some Advantages and Disadvantages of Hydroelectric Energy?

Updated on October 31, 2022

How does hydroelectric energy work?

Hydroelectric energy, also known as hydropower, is electricity generated through the movement of running water. This can be from a flowing river, or a dammed reservoir. Generally speaking, the most widely used form of hydroelectricity is from power plants housed in a dam. One example is of course the Great Hoover Dam, which you may be familiar with.

To produce electricity, all hydropower plants follow roughly the same steps. The water is funnelled in through a channel (or channels) where its flow rotates a turbine. The turbine in turn powers a generator, and then the electricity produced by the generator enters the supply line.

These days, hydroelectric energy is an important component of the energy supplies of most major countries due to its reliability and advantages over fossil fuels. In this article we’re going to take a look at some of these advantages, but also the disadvantages of hydropower. We’ll also take a look at the pros and cons of small hydro plants.

Is hydroelectric energy renewable?

Unlike fossil fuels which are finite, hydroelectricity is considered a renewable energy source. This is because hydroelectric plants generate energy by harnessing the kinetic (associated with movement) power of flowing water. Given that water is naturally occurring, and not combusted during the process, we can say that it is a renewable resource.

Hydropower advantages and disadvantages

What are 5 advantages of hydroelectric energy?

The top 5 advantages of hydroelectric power are:

  1. As we’ve just discussed, hydropower is renewable and does not rely on combustion.
  2. Dams and their reservoirs hold predictable amounts of water according to the time of year.
  3. Modern engineering means Dams are now incredibly safe, no matter their size.
  4. Hydropower plants can be made to various scales and on rivers with varying volumes. Power generation can also be regulated up or down.
  5. Low emission generation. Any emissions generated by hydroelectric plants are from associated machinery and only a fraction of those generated by fossil fuel plants.

Though important, these aren’t the only advantages to this type of power. Others include improved irrigation, tourism generation, and flood control.

Which power plant is most reliable?

The most reliable power plant that uses non-renewable energy sources is the nuclear power plant. But as might expect, there are serious environmental and safety concerns associated with this type of power.

Amongst the power plants that use renewable energy, hydroelectric and geothermal plants are the most reliable. In fact, hydroelectric plants are more reliable than either solar installations or wind farms.

The reason for this is that the reserves of water in a hydroelectric reservoir, or even a whole river system, generally take months to deplete from low rainfall. Even a short-lived drought is unlikely to interrupt power supply. Sunshine and wind, on the other hand, can vanish over the course of a few minutes.

What are the disadvantages of hydroelectric power?

The main disadvantage of hydropower is that the initial environmental impact can be very high. Flooding damage, and the interruption of migration routes for fish can have a lasting impact on the local ecosystem. Fish ladders, and other mitigation measures are almost always necessary.

Moreover, the impact on local communities can be high. Displacement and flooding can uproot whole communities. Those that rely on fishing can be particularly hard hit.

In monetary terms, hydro dams are also very expensive to build. This is partly down to the red tape involved, which often includes legal opposition from the displaced communities mentioned above. Another reason is the skilled workforce and raw materials required to construct them. It doesn’t end there though – some dam reservoirs also need dredging which is also costly.

Another often overlooked disadvantage is that some areas that are flooded to build hydropower plants are “carbon sinks”. This means forests, bogs or other ecosystems that hold a lot of carbon in organic matter. When they are flooded, this matter decays and releases the carbon into the atmosphere.

Hydropower advantages and disadvantages PDF

What are the advantages and disadvantages of small hydropower plants?

Sometimes called Micro Hydropower Plants (MHP). Small hydropower plants are versatile installations which can be used anywhere there is running or dammed water. In some cases, they can even be installed on private property which includes running water.

Most small hydroelectric installations generate from 10 to 100 Kw per hour of usage at maximum power output. Due to their small size, they can be used on small rivers, streams and even along water supply lines – eliminating the need for large dams.

Their two main advantages are that they cost much less to build, and they have a much lower environmental and community impact.

Nonetheless, small hydropower does have disadvantages. The most important is of course that they cannot generate anyway near as much electricity as a traditional hydropower plant. Overall, they are very much for the individual of very small community.

Reliability is also an issue with this type of installation. If an installation relies on a small lake or stream, then a drought can completely halt electricity production.

What are the advantages of small hydro?

What are the advantages of small hydro?

Pros and cons of small hydroelectric plants

The true advantage of small hydro is its drastically reduced cost, both in monetary terms and in terms of environmental impact. This lower impact reduces resistance to installations from both local communities and environmental lobbyists.

We have seen community resistance to wind farms and hydropower plants around the world and in some areas, this has slowed their installation. With small, unobtrusive hydroelectric plants, however, this issue is much less frequent.

Components of micro hydro power plants

Small hydro power plants are all basically made up of similar components. Overall, they follow the same basic plan as traditional hydroelectric plants. Given their small size, they may not have a dam and reservoir, but the following components are essential:

  • A channel or conveyance system, which leads water into the plant
  • A turbine, or wheel to harness and transform the kinetic energy of the water
  • A generator which transforms the kinetic energy into electricity

In addition, a mechanism for controlling the generator and wiring for delivering the electricity are needed. How these parts are configured depends on the type/size of the generator.

Problems associated with hydroelectric power plant

Environmentally speaking, hydroelectric plants are not perfect. And, though better than fossil fuels can still harm the environment.

One problem associated with hydroelectric power plant use is that they inadvertently remove oxygen from water. De-oxygenation of water downstream means the section further down the river is no longer as healthy for wildlife. This directly harms fish, many of which are dependant on water oxygen content for growth.

Another point to consider is that the section of river downstream is going to be a fraction of its former size. Local communities can be deprived of valuable irrigation water despite being many miles from the dam and hydropower plant. This is what led to the Colorado River dispute between the US and Mexico.

Which is the main disadvantage of hydro power plant?

The main disadvantage of hydroelectric power plants is their environmental impact, both during and after construction. Though renewable, it might be a stretch to call them “green”, as local communities of both animals and humans can be negatively affected for generations.

Moreover, if you factor in the destruction of carbon sinks, then an installation’s carbon footprint can be deceptively high.

Environmental impact of hydroelectric power

The environmental impact of hydroelectric power depends very much on the scale of the installation. Some river systems create and maintain a wide array of habitat types, beyond themselves. Floodplains, brackish swamps, and mangroves are all highly productive habitat types that require fresh water to thrive. If a dam is large enough, it can lead to the decline of these habitats downstream and their associated ecosystems.

The Three Gorges Dam in China, for example, caused widespread flooding and displacement of both humans and animals during its construction. This is because it is the largest hydroelectric power installation in the world.

These days it depletes the Yangtze River of its oxygen and stops silt flowing downstream. This silt historically reinforced the riverbanks and will now make these areas more prone to erosion and flooding. In fact, Shanghai, one of China’s most important cities, is located on a silt plain that washed down from the Yangtze River.

Notwithstanding, the emissions from burning coal to reach the same power output would be massive. After all the Three Gorges Dam has a power output of 22,500 MW! You would need to burn over 12,000 tons of coal to produce the same amount of energy for an hour (22,500 MWh).

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Dams such as this may has a large environmental impact, but it is debatable whether this impact is a severe as coal, the most popular alternative.

Resources related to Hydro electric power advantages and disadvantages:

Benefits of Hydropower | Department of Energy

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