Old Man Winter’s frigid temperatures might bring life to a grinding halt for some, but for the Tennessee Valley Authority, cold days make ideal conditions to generate efficient, low-cost electricity.

“You would think the hot summer would be a perfect time to make steam for electricity,” said D.J. Allen, operations shift manager at Watts Bar Nuclear Plant. However, “it’s the winter where we see the most efficiency because of the colder river water we use as a cooling medium.”

Allen said steam is a key ingredient when making electricity at nuclear and fossil plants. The TVA turns ultra-pure water into super-hot, high-pressure steam that turns massive turbines, which then spin generators to make electricity.

“Heat is the blessing and curse at a power plant,” Allen said. “To run a plant at maximum efficiency, you have to generate a lot of heat and then you have to remove it quickly so the steam cycle can start all over again.”

Allen said removing excess heat is easier in the winter because cooling water from the river could be as low as 45 degrees. In the summer, river water temperatures can rise above 80 degrees.

“Summertime is extremely hard on equipment,” Allen said. “A generating unit might be rated for 500 megawatts but restricted to only 300 megawatts in the summer because we don’t have the cooling capability that is provided during the winter months.”