GreenTech

Why hydroelectric power dams aren’t pro-environment

Several developing nations consider hydro-power as a renewable unlimited electric energy source. Such as C. Rinzin, director of Bhutan’s Druk Green Power Corporation for Bhutan, Indian corporations and The African Union Commission for the continent Africa. It´s a popular energy source, because the largest hydroelectric power dam Itaipu generates 12.600MW which can power more than 37.600.000 houses. It´s jointly owned by Brazil and Paraguay. On the second-place stands Guri dam (Venezuela) with 10.300MW and the largest in USA is Grand Coulee power station with 7.600MW. In this article we’re going to look at how hydro-power dams work and the pro’s/con’s.

The basic concept is rather simple: water flows through a dam, turns the turbines which turns the generator thus producing electricity. It goes as follow the dam holds back water which creates a lake called a reservoir. The dam gates opens, gravity pulls the water flow through a pipeline (called a penstock) where the pressure builds up for the turbine. These turn and connects to the generators. The generators are the heart of the hydroelectric power-plant and generates electricity by rotating a series of magnets inside coils of wire this moves electrons, which produces electric current. Then this AC concerts into high-power voltages with the transformer.Then power-lines transmit and distribute the power through 4 wires and the used water outflows and re-enters the river downstream through pipelines, called trail-races. The description above is about the impoundment hydro-power facility, which is the most common one. In the article below we got further into these types of hydro-power facilities, the pro’s and con’s of dams and more. 

You can divide hydro power facilities into three main types: diversion, pumped storage and impoundment. Not all of them are used for generating energy such as the run of river facility also known as diversion facility which pumps a portion of the river through a pen stock or contal. It doesn’t necessarily need a dam. The impoundment facility is the most known and common one. It is a hydroelectric power plant, which uses a generator to turn the water flow into energy depending on the consumers needs. Lastly, you got pumped storage hydro-power.renee van wesepNext to the types of large hydro-power plants you also have three size varieties: large,small and micro hydro power devices. It’s possible that individuals can own these devices for their own energy needs or to sell power to others. According to DOE (an USA organisation) large ones produce 30 megawatts (MW), small ones generate 10MW and micro hydro-power devices only up to 100 kilowatts. The last named is also being used for ranches, farms, villages or other individual home electric needs. Some governments encourage farms to build small ones to have a low ecological affect on the environment. 

Now you know the variety of hydro-power sizes, however it’s important which type of hydro-power turbines you select based on flow,volume and height of the standing water. At this moment you have impulse and reaction turbines. A reaction turbine are generally used for high flow with a lower water height sites. It can be divided into different types of propeller turbines: Francis, Kaplan, StraFlo and Turbe turbine. Secondly you have the impulse turbine which is generally suitable for low flow and high standing water. It can be divided into two types of turbines: the cross-flow and Pelton.

In this part of the article we’re going to look at the many pro’s and con’s of hydro-power. And we conclude if hydro-power is clean,flexible and practical enough to run as a main energy source. First we start with the main pro point of hydro-power: it’s renewable. Because the water flow is unlimited and production costs are eliminated when it’s running and has no direct ill-effects on the environment, because the dam doesn’t emit greenhouse gases,burn fossil fuels or pollute the water like other types of power plants do.

renee van wesep

Hoover Dam (USA)

Secondly, hydro-power plants have a long economic life span of 50-100 years and require only a small team of operators since the process is automated. In order to control water quality adjust the water flow and output of electricity for the demand or to prevent floods by storing excess water. They can also let debris settle out downstream, which improves the area conditions. And other new hydro power plants can be added to the excising one.

Another big pro is that water-power is safe and reliable, because there isn’t any fuel involved during the process and there are very little fluctuations with the output. The water flow is unlimited, making hydroelectricity consistent, practical and available through the entire year. And this popularity is felt: according to The Department of Energy (USA) hydroelectric power currently the largest renewable energy source worldwide. And 96% of US renewable energy comes from water-power, but there is space for more, because this department said that there are 5.677 potential sites available for these power-plants in USA. Lastly, water activities such as aquaculture, irrigation and water sports can be active in the basins where power-plants are located. 

With the many advantages that hydro-power offers there are major drawbacks, which makes this energy source renewable but less environmental friendly. Firstly, with the build of these power-plants greenhouse gases are emitted such as carbon dioxide. Generally, it’s an expensive project which can take between 5-10 years to construct. Another drawback is that hydro power plants must be build in particular places and there are only a limited number of suitable reservoirs which can make this project profitable. Because the dam is build on a large scale and holds back volumes of water it can’t afford fails due to poor construction or other risks, which can rapture the dam and damage it’s surroundings. A displacement of a massive dam can have large scale consequences such as the Three Gorges Dam in China, which flooded 13 cities, 140 towns and 1.350 villages in 2008.

This picture taken on July 24, 2012 show

Three Gorges Dam (China)

It can also cause opposition of (local) groups such as religious infringement of sacred land or tribal rights, because of flooding areas of land that was once forested or farmed. Environmental and conservationist groups in USA have often contested to construct large scale dams. Examples are the Hetch Hetchy reservoir and the O’Shaughnessy Dam in Yosemite National Park (1923) and the Echo Park Dam at Dinosaur National Monument (1950). Another placement drawback is that hydro-power dams are linked to increased earthquake vulnerability.

Hydro-power plants aren’t fail proof, because if there is a lack of rain near the plant, water won’t collect upstream thus less water flows through the dam. Rain is dependent on the hydrologic life cycle. The sun is heating the water, which evaporates and eventually condenses and falls in the form of rain. Droughts can occur and this means an increase in energy prices.

But the biggest drawback of this renewable energy is that during the construction and in operation it can lead to imbalances in the landscape, ecosystem and river flow. Affecting the river’s temperature, slit-load, chemistry and water flow, because of the dam the river is turned into a lake. And according to International Rivers [GNO] the construction have led to the disappearance of birds, losses of farmland,wetland and forest, erosion of coastal deltas and the extinction of fish populations. The fish population and other water species have the most to lose. Aquatic flora (plankton/Algae) can increase in the lake which can cause atrophy accumulation leading to the loss of wildlife and local climate changes due to water evaporation (fog). Also the dam limits the fish access to a broader spawning ground and it won’t transport heavy particles causing an increase in siltation. Another problem occurs behind the dam where sediment is retains so the banks downstream of dams are subject to erosion. 

In conclusion hydro electric power is a great cost efficient way for developing countries, because the constant waterflow means an unlimited power resource and you need a small group to operate the machines. That being said hydro-power is far from environmental fail proof: earthquakes, loss of wildlife/landscape and the local climate changes. Although it can be  a renewable energy source in most cases hydro-power doesn’t provide the best green environmental solution.

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