Tuesday, March 20, 2012

Mega Hydro

By Keith Heyde

A few weeks ago I wrote a piece of micro hydro. The article focused on the ability to generate electricity from small sources without any real inhabitation to the natural flow of water. These micro systems offer advantages of being minimally disruptive to the environment while simultaneously generating energy.

Well, this week we are going in a different direction.

Let’s talk about BIG hydro for a bit.

For those of you who are less familiar with hydroelectric generation, BIG hydro refers to the world’s mega dam projects. These projects range in size, shape, design, and output, but they all preform a very similar function to one another: to hold back the tide of water and generate electricity accordingly.

The United States is home to a couple of big dams of note. Perhaps the most famous and ‘iconic’ dam is the Hoover dam. This construction feat, built during the great depression, still boasts the title of being the tallest dam in the United States, and it is perhaps the most influential.

The Hoover dam opened up the door for megadams worldwide. First off, the Hoover dam faced some unique construction issues while it was being built. Never before has such a large flow of water needed to be diverted. This led the way to novel construction techniques and practices. Secondly, the dam pushed the limits of what was thought possible. Not only did the dam tower above all previously constructed dams, but it also rose above most buildings at the time.

Furthermore, the Hoover dam profoundly altered the ecosystem around the dam. It formed Lake Mead as a reservoir behind it which has altered the entire shape of that region in Nevada. In the American Southwest, an area constantly parched, building a lake (with both collective and evaporative issues) altered the entire course of development. This also lead to the Glenn Canyon dam and others which bottled and harnessed the Colorado for both energy and reservoir purposes.

The Colorado of today usually does not even reach its original terminus in Baja California.

Believe it or not, the Hoover dam is not the ‘biggest’ in the United States, that title belongs to Grand Coulee dam (eastern Washington state), which has a measured output of around 7000 MW and is looking to nearly double its output through retrofits within the next few years. On a side note, the Grand Coulee dam is also a byproduct of depression era construction projects.

Although an output of 14,000 may sound impressive, it is paled when compared to the 20,000 MW dam proposed for Russia. This project is still in the works but has stalled recently due to the boom of cheap natural gas in Russia.

Interestingly, there are some stark contrasts between dams slated capacity and their actual output. Of the top 5 hydropower producers in the world (Canada being first), the most efficient by far is Canada. With a ‘conversion ratio’ of 4.7 they top the charts. Brazil follows with a conversion of about 4.4, then Russia at 4, China at 3.7, and finally the United States at 2.5. Of course these are only the world’s largest hydropower producers, but it is still interesting to see the conversion. Part of the reason the U.S. lags behind is due to aging infrastructure.

Large dams can be profoundly altering to ecosystems in disruptive ways. At the same time, dams do allow for life to spring up where formerly thought impossible such as Lake Powell in southern Utah. This reservoir has created a mini ecosystem full of fish, trees, and many other forms of life in what was an arid desert.

However, as we have seen with the demise of the Aral Sea, we should never take too much from the water systems around us. If we push something too far for too long, it often breaks.

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