TVA's power generation more efficient with cold winter temperatures
On Wednesday morning, low temperatures were in the 20s and teens across the area. With the colder temperatures, regional power demand increases.
TVA’s peak power demand Wednesday morning was 27,500 megawatts, and they expect a higher peak demand Thursday morning with even colder forecasted temperatures.
They are prepared to meet this demand partially because the winter season cold weather helps power to be generated more efficiently at their nuclear and fossil plants.
Both plants produce heat first.
"That heat, it boils water. We flash it over to steam, and that generates electricity through a generator, and then we use river water to cool that steam back into water. And then, we flash it back into steam again,” Scott Fielder, TVA spokesperson, said
Colder temperatures during the winter season mean the temperature of the Tennessee River is lower. The cooler the water temperature, the more efficient the power generation cycle will run.
"We use that river water to cool the steam, so if we can cool the steam fast, heat it up fast, cool it fast, it generates. It allows us to generate more electricity faster," Fiedler explained.
In summer, the water temperature of the Tennessee River is about 80 degrees compared to 45 degrees or less in the winter. This cold winter temperature provides the ability for power generation units to run at full capacity.
For instance, if a unit has a max rating of 500 megawatts, during winter it can produce at the full 500 megawatts with the faster cooling process of the river water.
"During the summer, when the river water is warmer, we may have to degrade that or down rate that unit to maybe 300 megawatts because we can't cool the steam fast enough," Fiedler stated.
So, the colder the water is in the Tennessee River, the more power can be generated.
On the other hand, daily cold temperatures increase power demand.
TVA has a team of meteorologists tracking weather conditions to prepare to meet increased demand.
"We can look out as far as 6 weeks in advance. Sometimes there is confidence in that, and sometimes there is not, but we've had some pretty good confidence in this upcoming cold wave. We've been looking at it for the last couple of weeks," Patrick Walshe, TVA Manager of Resource Operations and Analysis, said.
They then notify the company, so if additional units are needed to meet peak power demand, they can be operationally turned on in advance of the arriving colder temperatures.
If you are interested in testing out this process of colder water condensing steam back to liquid water faster than warm water, here is a simple experiment you can do from TVA.