DENVER — 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 happened one recent Tuesday — which just happened to be Election Day — because it got much windier during the daytime than both the pair of meteorologists and advanced forecasting systems employed by Xcel Energy had predicted.
"This week has been a very unusual week on our Colorado system for wind," said Eric Pierce, Xcel's managing director of power operations. "There have been some challenges."
The challenges Pierce speaks of get at the heart of what is one of the biggest obstacles facing widespread adoption of wind power: its inherent intermittency. The wind blows only sometimes (and sometimes it blows too much). By contrast, you can almost always rely on a steady source of coal, natural gas, or nuclear power.
"We've asked a lot more of our units over the last three or four years and the people operating the grid," Pierce said. Indeed, Xcel has been increasing its mix of wind power over the last few years largely because of Colorado's renewable portfolio standard and supporting federal tax policy — namely the production tax credit, which is scheduled to expire at year's end.
Xcel is now the country's largest wind-electricity generator with roughly 12 percent of its production coming from wind (the country as a whole gets about 3.5 percent of its electricity from wind). Almost half of Xcel's portfolio is coal and 25 percent is natural gas, which mirrors the national mix.
"For a period of time we were driven significantly by the state renewable portfolio standard," said Dave Eves, president and CEO of the Public Service Company of Colorado, an Xcel subsidiary that is the state's largest utility. "In the last few years the wind has been added and solar too, strictly based on economics."
On that windy Election Day, Xcel's grid system in Colorado, which is less connected to other electricity grids in the country compared with others, had to turn down its gas and coal plants as soon as possible so as not to overload the system.
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."
Representatives of the industries that produce the natural gas and wind have often been at loggerheads when it comes to lobbying. After all, they compete for pieces of the relatively stagnant U.S. electricity pie. According to Energy Information Administration data, wind and natural gas are the two fastest-growing sources of energy in the country.
"It's the best friend and worst enemy at the same time," Eves said.
The industries are being friendly as of late. The new president of the American Wind Energy Association met recently with the new president of America's Natural Gas Alliance.
"I look forward to working with ANGA and others in the natural-gas industry," said Tom Kiernan in an interview in Washington last week. "Gas sometimes and in some places is a good backup for wind, but there are a lot of times wind doesn't need back." He noted that in other places in the country where electric grids are more integrated than Colorado, other wind-energy sources can also serve as backup supplies.
Meanwhile, oil and gas companies also have positive words to say about wind, despite the energy boom they're reaping.
"Natural gas and renewables is a perfect marriage," Ted Noble, a senior vice president at Noble Energy, Colorado's biggest oil and gas operator, said in an interview in Denver. "We have to be able to supply, first of all, affordable energy to our citizens, and natural gas does that. And then at the same time when getting into the renewables side of the equation, when you marry those two together, one really can't function without the other."
The next few months will be especially pivotal to the wind industry as it fights to preserve the production tax credit. Eves said that if the tax credit expires, wind may not be able to compete as well with natural gas.
"It would have an impact on the cost of wind in the country," Eves said. "It depends on how the cost of wind without the PTC compares with natural gas."
That's when natural gas might go from wind's best friend to worst enemy.