The power grid may determine whether we can kick our carbon habit

  • High voltage transmission lines and turbines at the Dry Lake Wind Project near Holbrook, Arizona. The project is operated by Iberdrola Renewables, and all its power is purchased by Salt River Project.

    Jonathan Thompson
  • The 2011 San Diego blackout.

    Sean M. Havvey/U-T San Diego/ZUMApress.com
  • The Palo Verde Nuclear Generating Station west of Phoenix can crank out more megawatts than any power plant in the nation, and the associated Palo Verde/Hassayampa switchyard is the most active electricity trading hub in the West.

    Jonathan Thompson
  • The switchboard and generator of the world's first single-phase AC power transmission system at the Ames hydroelectric plant near Telluride, Colorado. The plant, now owned by Xcel Energy, continues to feed up to 3.75 MW into the grid.

    Library of Congress, HAER COLO,57-AMES.V,2A-6
  • The Alhambra control center of the California Independent System Operator, which manages about 80 percent of the state's grid and the mix of energy going into it.

    California Independent System Operator
  • Wind turbines line the ridge above the John Day Dam on the Columbia River. When water levels are highest, the Bonneville Power Administration may force wind generators to shut down, to avoid overwhelming the grid. Courtesy

    Samuel M. Beebe/Ecotrust
  • Contractors watch last April as a helicopter places a lattice tower for the Sunrise Powerlink, the controversial 117-mile, 500-kilovolt electric transmission line that runs from Imperial County to San Diego, California.

    Sam Hodgson/Bloomberg via Getty Images
  • High-voltage transmission line in Arizona.

    Jonathan Thompson
 

Page 3

On the south end of Scottsdale, Ariz., a low-slung, mostly windowless brick building sits back from the street between a Spanish colonial apartment complex and an upscale mobile home park. No sign tells the curious passerby what might lie within, yet the gleaming razor wire atop the surrounding wall raises unsavory possibilities. A guard is there to stop the curious, and if she fails, the device that pops out of the pavement and rips your tires to shreds will definitely succeed.

This is the operations center for the Salt River Project, one of the nation's largest municipal utilities. The executives and the clerks hang out at another building a couple miles away in Tempe, but this is where the real grid action goes down. When potential crises strike, operators here do their best to keep them from spreading. (SRP wasn't hit by the San Diego blackout, but since it operates the Palo Verde switchyard, it was peripherally involved.) Most of the time, though, technicians spend their time keeping power flowing to some 1 million customers in the Phoenix metro area from the utility's power generators, which range from shares in coal plants as far away as northern Colorado to small hydroelectric facilities on Scottsdale's canals.

You'd think the stress of keeping all those air conditioners running would wear on Mark Avery, SRP's grid manager. But he's fit, trim and looks no older than 50, with a full head of salt-and-pepper hair. When he tells me that he started his career as an operator trainee in 1974 at Navajo Generating Station in northern Arizona, I have to ask him to repeat himself.

Of all the baffling facts about the grid, perhaps the most mind-boggling, Avery tells me, is its constant need to be kept in balance. "The Western Grid is like a giant bucket," he says, "with a bunch of spouts running in and out, and you have to keep the water level constant." That is, the amount of electricity being fed into the Western grid by thousands of generators must always be equal to the load –– meaning the amount being used by its millions of customers. Lose the balance, and the frequency of the alternating current will drift away from the optimum 60 cycles per second, which could cause equipment to fail and result in outages. In the Western Grid, that balancing act is performed simultaneously by 38 different authorities; Avery and his colleagues oversee one of them.

Each day, using models based on weather forecasts and historical patterns, SRP's marketing team draws up a demand forecast for the following day, and schedules generation from SRP's own array of generators, (or from neighboring utilities if it's cheaper) to "follow" the demand curve. They also schedule plenty of extra backup power -- usually from fast-firing natural gas or oil "peaking" turbines -- to make up for forecast errors or to compensate for a downed power line or plant. The grid operators are then responsible for implementing the daily plan, and for tweaking it as it unfolds with hourly forecasts and scheduling. Over the course of the hour, they make up for energy imbalances -- or deviations from the plan -- by turning generation up or down. Minor, second-to-second bobbles are "regulated" automatically by software, typically by adjusting Hoover Dam's hydroelectric turbines.

Over time, this balancing act has become more and more challenging. Four decades ago, the greatest demand came from big industrial facilities like factories or mines that ran round-the-clock or on a set schedule. The generation sources were also steady and predictable, coming mostly from "baseload power" –– meaning coal or nuclear.

In the 1980s, the demand side of the equation began to change radically. As manufacturing moved overseas and people poured into the region, residential and commercial customers -- whose electricity demand curve has bigger daily ups and downs -- took up a larger share of overall demand. The air-conditioning revolution arrived at the same time: Between 1980 and 2009, the percentage of Western homes with air conditioning shot up dramatically, so that now there are more than 18 million homes with power-gulping cooling systems on the Western grid. On a summer's day in the desert Southwest, the overall electrical load at 5 p.m. can be twice what it was at 5 that morning, mostly due to the energy it takes to cool us all down; it can account for about 30 percent of total peak electricity demand in California or Arizona.

The new sources of power feeding into the grid are even less predictable. Solar and wind energy can swing up and down dramatically during a single hour. A massive dust storm or thunderheads moving in on a summer afternoon can cut production from a photovoltaic array by 80 or 90 percent in a matter of seconds. Wind-power swings are less violent, but can be huge: California's collective turbine output can vary by 3,000 megawatts or more over the course of a day, and by 100 megawatts in an hour. The greater the percentage of solar and wind in the mix, then, the greater the potential for errors in the day- and hour-ahead scheduling, and the more potential for imbalances, instability and outages.

"It's not the same kind of dispatchable, turn a lever, decide a day ahead what you're going to run the next day with any kind of certainty system that we're used to," says Brian Parsons, transmission and wind integration group manager at the National Renewable Energy Laboratories in Golden, Colo. Utilities typically respond to that uncertainty by adding two megawatts of natural gas backup capacity for every three megawatts of added wind power, chalking up the expense of building and operating the reserve to wind's "ancillary costs."

For Mark Avery, the variability is virtually a non-issue, because only about 3 percent of SRP's energy mix comes from solar and wind. But in California, where the state has required utilities to get 33 percent of their power from renewables by 2020, it's been a significant source of hand-wringing, as officials scramble to make sure they have enough reserves to cover wind and solar's variability. Fossil-fuel pushers regularly warn that replacing their steady plants with fickle solar and wind will plummet us all into darkness. They point to Germany, which now gets more than 20 percent of its power from non-hydroelectric renewables, primarily solar and wind. That has pushed the transmission system to "the brink of capacity," according to that grid's federal overseer, and renewables-caused voltage swings have resulted in machine malfunctions at Hamburg factories.

But is the problem really with renewables, or with the grid and the way it's run?

Howard Johnson
Howard Johnson says:
May 28, 2013 11:48 PM
Great article, continue to follow the ACC, as it is critical for AZ to push solar ! !
Jonathan Thompson
Jonathan Thompson says:
May 30, 2013 10:42 AM
Editor's note: A comment was deleted from this thread because the commenter, after reading the rest of the story, retracted the comment (realizing the story actually did address the issue that he thought it had overlooked).
Toby Thaler
Toby Thaler says:
Jun 04, 2013 04:00 PM
"There is probably no other five-square-mile patch on the planet with more electrical generating capacity." Well...

Palo Verde nukes = 3.3 Gw; Arlington Valley gas turbines = 0.6 Gw; solar in area= 0.5 Gw(?)

Grand Coulee Dam generates 6.8 Gw. Three Gorges Dam in China = 22.5 Gw. In fact, it looks like there are a dozen or more hydro projects that generate more than the entire Palo Verde hub area, unless I am missing some large generators (it's not an area I'm familiar with). See http://en.wikipedia.org/[…]/List_of_largest_hydroelectric_power_stations

Palo Verde does not even appear to be close to the largest generator of thermal power. See http://en.wikipedia.org/[…]/List_of_largest_power_stations_in_the_world

Please don't put inaccurate factual puffery into your reporting; it detracts from the high quality of the article.
Jonathan Thompson
Jonathan Thompson says:
Jun 04, 2013 09:30 PM
Toby: Thanks so much for keeping me on my toes. We love our readers for that very reason. I'll confess that when I wrote that, I did not consider those giant dams -- and certainly not Three Gorges in China, which dwarfs just about everything. As for the generating capacity for the Palo Verde hub area, here are my numbers: Palo Verde Nukes: 3,800 MW (SRP figures); Mesquite natural gas plant: 1,250 MW; Arlington Valley Solar: 250 MW; Red Hawk natural gas: 1,060 MW; Arlington Valley Natural Gas plant: 577 MW; Mesquite Solar: 150 MW. For a grand total of 7,087, which is greater than Grand Coulee Dam, and collectively makes it the largest generator in the nation (not the planet! It is my understanding, though, that the Kashiwazaki-Kariwa nuke plant in Japan, which would be bigger, is shut down for "inspections" following the Fukushima disaster, but may never reopen because it lies on a fault). And the Palo Verde energy park, if you can call it that, continues to grow: The Mesquite Solar facility will be 700 MW when it's finished (and I may have missed more solar facilities. To be honest, it's hard to keep track). All of which to say, you're right: the Palo Verde area collectively adds up to have the biggest generating capacity in the nation, but not the planet. A handful of giant dams have that distinction. Thanks again for pointing that out.
Toby Thaler
Toby Thaler says:
Jun 05, 2013 01:33 PM
And thank you very much for the more detailed list of generating plants in the area. That's 54% nuke, 41% fossil thermal, and 6% renewable. Not a pretty picture as we move onto the down slope of peak fossil fuels.

And, as wiki points out, "Since the nuclear fuel cycle is effectively not closed, Hubbert peak theory applies." The analysis of this aspect of nuclear power is very unsettled. See http://www.theoildrum.com/node/2379

Good reporting, thanks.