The Taum Sauk Hydroelectric Plant 80 Km away from the nearest Mississippi River is one of the most intriguing dams in the world as it is a net consumer of electricity and not a producer as dams are supposed to be and no, it is not because of falling infrastructure or any other reason. It is because it is one the few pumped hydroelectric power plants in the world where water is pumped from the lower reservoir to the top reservoir during limited consumption hours and then the stored gravitational potential energy is then used to produce electricity in the peak hours. Ironically enough, the dam sits top on the “Proffit Mountain” even when it is making an energy loss!
Now while it seems like a brilliant idea on paper, such a large set of reservoirs probably took a lot more money to develop than an average hydropower plant, and the result isn’t electricity generation but rather consumption. But, more and more emphasis is now on peak hours consumption in morning times and evening times than the total electricity generation because the idle timings don’t even require a quarter of the total power as compared to the peak hours. The two water reservoirs are more than two kilometers apart, and more than 1.5 billion gallons of water is stored in them. Now it all seems pretty straightforward, but it is not. The dam is still in service, but it had a catastrophic breakdown in 2005 when its banks overspilled. It is also a challenge from a civil engineering perspective to minimize the losses while achieving the maximum water velocity in the power generation tunnels. Also, since it is not a natural dam, the structure to hold back this amount of water is very difficult.
Even when the dam has an energy loss, it is still generating a profit since the electricity is provided to the customers at peak hours and charged accordingly while the power is being used in idle times. All in all, it produces 500 MegaWatts of power and does add valuable power to the grid when it is needed most. If it was somehow coupled with a large solar energy plant, the dam could do wonders by storing electricity in the day and then releasing at night!
The Tam Sauk dam is the largest roller-compacted concrete dam in North America and is being run by US society of dams.
THDC has also made such dam Tehri Asia second largest earthen dam. Its second stage is also doing pump storage scheme. In India.