After an extended summer, cold weather slipped into the valley over the weekend, with temperatures dipping below freezing in some parts of the region. Monday morning commuters had the pleasure of watching the plumes of their breath as they scraped frost away from windshields and cradled cups coffee for warmth.
The System Operating Center in TVA’s Chattanooga office was abuzz with activity—with cold weather comes increased operations, of course, and decisions were being made about bringing more coal or gas plants online to meet anticipated peaking load.
They weren’t shooting in the dark, nor reacting to conditions in the moment. Their performance had been carefully orchestrated 24 hours in advance by one man: Jeff House, senior program manager of Short-Term Load Planning and TVA’s acting in-house meteorologist.
His job is to deliver an hour-by-hour forecast, 24 hours in advance, for all 8,760 hours of the year, every year. How well he does his job determines how closely TVA can match generation to actual demand. It’s incredibly important, as there are considerable consequences and costs associated with missing the mark on either end—forecast too high, and TVA might be left with too much power and have to sell it cheaply on the open market; forecast too low, and TVA might have to buy power at a premium to make ends meet.
The Personal Touch
Luckily, Mr. House is very, very good at his job, explains his boss, Patrick Walshe, manager of Resource Operations and Analysis. “Good weather forecasting will generate under a three percent error; here at TVA, we aim to get closer to 2 percent,” he says. “Jeff House has recently brought our mean absolute percentage error down to 1.9 percent.”
It takes a human touch to get those kinds of stellar results. Mr. House—who boasts a degree in atmospheric science from the University of Kansas and an MBA from Wichita State—works with a variety of computer modeling tools designed to help him hone in his forecast, but they’re no substitute for human experience.
“Sometimes I see something in the weather pattern coming into the Valley that I’ve seen before, and I just know the raw data needs a little human adjustment,” he says. “I’ve learned to add it up in a specific way that accounts for the Valley’s specific features. The Cumberland Plateau, for instance, can make or break a forecast. I can read between the lines, and I know when I need to be concerned or not.”
Mr. House issues mid-term and long-term forecasts, too. For instance, he knows that after this cool snap, things will warm up for a while, and that we’re likely to have a mild winter this year—though “not as crazy warm as the last two years.”
His forecasts are used across the agency—by transmission (lines act differently, depending on how hot or cold it is), by operations (which makes decisions based on load forecasts), by purchasing (which buys fuel based on forecasted needs) and by generation (turbines also respond to fluctuations in the weather).
Accuracy translates directly into megawatts. “When Jeff first started with TVA in 2010, the average hourly error was 500 MW,” Mr. Walshe says. “Now he’s gotten that down to 344 MW—he’s lowered the average by 150 MW, and that’s pretty amazing. The better he is, the better we can do for TVA financially.” To put that number in persperspective, 150 MW is enough energy to power roughly 87,750 average homes.
It’s hard to put a dollar value to Mr. House’s work, but on a bad and blustery day, getting the forecast right might save TVA somewhere in the hundreds of thousands of dollars. “You can turn off your combined cycle plants, but you don’t want to ever be shutting down a coal plant in the middle of the night,” Mr. Walshe explains. “That’s why a day ahead is the big measure for forecasting. It’s as important in the middle of the night as it is in the middle of the afternoon. It’s important 24/7.”
And, yes, Mr. House predicted his manic Monday freeze—and so all of TVA’s assets are aligned to deliver a predicted peaking load of 21,300 today. “That’s just typical,” he says. “We always get our first freeze right around Halloween.”