Balancing Wind and Gas Generation

National Journal:

Managing wind power makes flying a kite look easy.
Wind usually blows the most between 1 a.m. and 4 a.m. when people need electricity the least. But every now and then, the weather gets surprisingly windy at other times. That's when a handful of people on the 10th floor of a downtown Denver office building suddenly get very busy.
"They're really scrambling during that time frame," said Mike Boughner, Xcel Energy's manager of generation control and dispatch, while giving a recent tour of the company's "trading floor," where traders buy and sell electricity and other employees manage the power of the company's entire electric-grid operations throughout the Western and Central U.S., 24 hours a day, seven days a week. "They're calling all the plants, both natural gas and coal, and telling them to back down as fast as they can."...
This is where natural gas comes in, which can be turned on and off more quickly than coal and nuclear. It's also cheaper than nuclear and cleaner than coal.
Pointing to one of many large screens in the room, Boughner said: "This shows the flexible gas-fired combustion turbines that the operator uses to fill in the gaps and respond to variabilities in the wind."
In addition to natural gas, Xcel also uses a hydroelectricity dam in the nearby Rocky Mountains as backup power to wind, which in a roundabout way is actually powered by wind. But natural gas is the primary source used by Xcel—and the country—to use when the wind dies down.
These two energy resources have long been considered a good match on the grid, and Xcel Energy is on the forefront of testing the boundaries of this relationship. Until technology offers a way to store renewable energy on a wide scale, wind needs natural gas.
"We'd have blackouts," Boughner said when asked what would happen if Xcel didn't have natural gas to back up wind. "We would definitely have events where we would have to shut off the lights."
But wind helps natural gas, too, in different ways. It has no carbon emissions, which helps utilities comply with stricter environmental rules and combat global warming. It also has a cost benefit. Even though the country is awash in shale gas and prices are at near-record lows, utilities remember that just a handful of years ago prices were five or six times what they are today. They don't want to depend too much on gas.
"We look at wind as a hedge for natural gas," said Eves. "So with some of these low-cost wind farms, that's the equivalent of locking in a $4.50 gas price for 25 years. It's an unbelievable hedge."

This highlights some of the things I was talking about yesterday. It would be interesting if the article went into a little more detail when it says the hydroelectric dam is powered by wind in a roundabout way.  I would assume that means they are using excess wind power to pump water into the reservoir, but they don't really say.  Anyway, in the Great Plains they are going to be generating a significant amount of electricity with wind turbines.