Understanding the Hydroelectric Power Plant that Loses Energy

When you think of a power plant, you typically assume that it creates more electricity than it consumes. While this might be the case in most power plants, there are a select few that actually result in a net energy loss.

Take for example the famous Taum Sauk Hydroelectric Plant in the Missouri Ozarks. This hydroelectric plant isn’t located on a dam on an existing waterway, rather it is perched atop a mountain. The nearest water source, the Mississippi River, is over 80 miles away from the facility.

This plant in the Ozarks is one of the few plants in the world that is a purely pumped-storage power plant. It holds 1.5 billion gallons of water and was built to supply power to the locals during the day. There is no natural inflow of water into the reservoir, making the plant a net consumer of energy.

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Image Source: Avirat

The logical next question when hearing about this power plant is… why? It all has to do with electricity costs. Water is pumped up to the reservoir at nighttime hours when demand for electricity is lower and thus cost to run pumps is lower. This stores massive amounts of potential energy in the water stored in the dam. During the day when costs for electricity are higher and so too with demand, water is drained from the reservoir converting the potential energy in the water into kinetic electric energy.

In total, the power plant can generate 500 MW of power. When you consider the dam in terms of money, the whole operation is able to stay profitable due to the fluctuation of energy prices in the area at different times of the day. Due to these economics, this power plant can operate on a net loss of energy. Instead of being a power plant, we can almost think of it as a giant potential energy water battery.

Digging into the engineering of this specific power plant even further, you can begin to understand how this project was technically daunting. Normally, dams and hydroelectric plants only have to deal with blockading one portion of a natural waterway. In the case of the Taum Sauk power plant, what is essentially a massive concrete pool had to be constructed on the top of a mountain. The amount of hydrostatic and dynamic pressure this structure has to hold is absolutely insane from a loading perspective.

All of this technically daunting background leads us to an all too common occurrence with dams: failure.

When this power plant was first built back in the 1960s, there were leaks plaguing the structure. For essentially the first half century of the plant’s life, the leaks and problems were manageable by operators. Until December 14, 2005.

On this date, pumping stations failed to shut off and water began to overflow the walls of the reservoir. Eventually, the earth making up the dam became saturated and failed. All of the stored water in the power plant rushed down the side of the mountain in what was described as “Niagra Falls.”

Luckily, there were no fatalities in the dam disaster, but the plan was completely destroyed. Construction to rebuild the power plant began in 2007, eventually being completed in 2010. A number of fail-safe alarms and safety systems were put in place in the new structure to ensure that the disaster never happened again.

Engineers also changed some of the ways in which the reservoir walls were constructed in the new design. Instead of a large earthen outside wall with an interior concrete structure, the new dam is now entirely covered in concrete through roller compaction. This makes the walls of the Taum Sauk power plant technically the largest roller-compacted concrete dam in North America.

Operations of the power plant continue to this day.

Trevor is a civil engineer by trade and an accomplished internet blogger with a passion for inspiring everyone with new and exciting technologies. He is also a published children’s book author whose most recent book, ZOOM Go the Vehicles, is aimed at inspiring young kids to have an interest in engineering.


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