Monday, November 09, 2009
Pump system is net producer of electricity
Tom Angleberger
The New River Valley-based reporter answers your questions Mondays in his column, What's on Your Mind?
Recent columns
Q: I've been a lake resident for 20 years and noticed that people like to think of the Smith Mountain Lake Dam as a producer of electricity. No one seems to question that idea. I am.
The economic benefits to Appalachian Power of the pump storage protocol at Smith Mountain Lake are well understood. Since, however, it takes more electricity to "pump back" a cubic foot of water than that same water will generate in its reuse, I have a question. In the course of a year is the dam a net producer of electricity or a net consumer?
-- Donald A. Hopkins, Huddleston
A: Before we get into the answer, let's review the pump storage thing. I'm not sure it is all that well understood by most folks. (When I say "most folks," I mean "me," of course.)
To start at the beginning: Water going through the dam's turbines generates electricity. The water goes downstream to the lake created by the Leesville Dam. Sometimes it's actually worth it for Appalachian Power to pump some of the water back up into Smith Mountain Lake to let it run through the turbines again.
"The value to us and customers is the times of day in which we generate and pump back into the upper reservoir," explained Appalachian spokesman John Shepelwich. "So, we generate from Smith Mountain Dam when costs of other power (coal, etc.) are high and pump it back from the lower reservoir (Leesville) when those costs are lower."
As you've guessed, it takes a lot of electricity to do all this pumping. On a yearly basis, Smith Mountain Lake Dam often -- but not always -- uses more electricity than it generates. However, when you add in the electricity made at Leesville Dam, there's enough to make the whole operation a generator of electricity.
Shepelwich sent me some hard numbers. On average the Smith Mountain Lake operation generates 476,640 megawatt hours every year. Leesville makes 59,376. Together they total just a little bit more than the amount Smith Mountain Lake uses: 531,742.
Grammar Grumblings
Inge Camplejohn wrote in to grumble about people who say "I wish I was ..." or "If I was ..." The correct ways are, "I wish I were ..." and "if I were ..."
Why? Well, not for any logical reason, our Grammar Guru admitted.
"This one is all grammar, for there's no real logic to the rule," Virgil Cook told me. "This construction is a remnant of the subjunctive mode that was much more prominent in centuries past." It's the iffy nature of the sentence that does it. We're speaking of something that might be, not something that is.
While the rule may be pointless, there is an easy way to keep things straight. Just remember that Dixie is wrong: "I wish I was in the land of cotton ..."
But Tevye, the Fiddler on the Roof, was right: "If I were a rich man ..."
Bring on the questions
It's almost time for our fall edition of Ask the Readers. I've got some good questions already, but I'm always glad to get more. And, since the Christmas season is nigh, I'd love to have a Christmas-related question -- especially one that requires readers to fire up their memory banks.
Lastly, I'm sorry to report the passing of a friend of this column. Jim Slater, a retired state trooper, answered a question for us awhile back and was a very friendly fellow as well.
Got a question? Got an answer? Call Tom Angleberger at 777-6476 or send an e-mail to woym@roanoke.com. Don't forget to provide your full name, its proper spelling and your hometown. Look for Tom Angleberger's column on Mondays.
