High Country News: The 21st century’s Hoover Dam?
October 19, 2014
In late September, on the same day that world leaders were meeting in New York to talk about the climate, a group of four energy corporations announced the $8 billion Pathfinder project, which would generate wind power in Wyoming to sell to California and, according to its proponents, would be "the 21st Century's Hoover Dam — a landmark of the clean energy revolution."
At first listen, it sounds like a bunch of hot air. Hoover Dam is hard to match as a component of the grid, $8 billion is a lot of cash to scrounge up, and the permitting alone could take years, even decades. Besides, a similarly ambitious project by Power Company of Wyoming — two huge wind farms paired with the direct current TransWest Express line to California — is already much farther along than Pathfinder. In fact, the Pathfinder plan isn't even new: It's been on the table, stagnating for years.
Still, there are some twists in that new/old proposal that are buzzworthy: A massive energy storage component that utilizes underground salt caverns in Utah; and the proposal to use an existing transmission line that stretches from Utah to California. Though the whole endeavor may be pie-in-the-sky, it gives a glimpse into a post-coal — and possibly post-hydropower — West, and reminds us how inextricably entwined the Interior West's energy ambitions are with California's energy hunger.
The Pathfinder project would work like this: Wind turbines near the southeastern Wyoming towns of Wheatland and Chugwater, with a collective generating capacity of 2,100 megawatts, would send 6 to 9 terawatt-hours* of electricity each year through the 525-mile direct current Zephyr transmission line (to be built as part of the project), across Colorado, to Delta, Utah. There, the line would connect into the Intermountain high voltage direct current line that now carries coal-generated electricity from the Intermountain Power Plant, also in Delta, to Los Angeles.
Building the Zephyr DC line enables Pathfinder to send its wind power straight into the California grid, without the possibility of getting diluted by fossil-fuel-generated electricity along the way, thus making it more compatible with California's renewable portfolio standard requirements (the proposed TransWest Express is also DC). Meanwhile, since Intermountain's biggest customers, Los Angeles and other California utilities, must kick coal by 2027, the Intermountain line into L.A. should have plenty of available space on it in a few years. Rather than building a brand-new transmission line across California, an increasingly difficult and expensive task, the project can utilize that existing line.
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Then there's the storage part. When Southern California's load, or electricity demand, is low, but the wind is cranking in Wyoming, excess energy will be used to compress air, which will be pumped into underground salt caverns near Delta. When the wind's not blowing, or when the California load increases, then the compressed air can be released, combined with natural gas, and used to turn turbines to generate electricity that can go back into the grid. It's cool stuff, for sure. But is it as good as a massive dam, like Hoover?
To a grid operator, a hydroelectric dam is a beautiful thing. Like a nuclear or coal power plant, it can provide oodles of steady, baseload power, yet does so more efficiently, elegantly and without the pollution and waste. Hoover has a nameplate capacity of about 2,000 megawatts, about the same as the largest coal power plants in the West. A dam's turbines can be cranked up or down relatively quickly, giving grid operators an effective tool for "following the load," or reacting to large fluctuations in power demand. This flexibility also allows a dam to be used to "smooth" the natural peaks and valleys of a wind farm or solar plant's power output, a service often provided by natural gas power plants. Meanwhile, the reservoir is like a giant battery, storing potential electricity until it's needed.
Only, there are problems. First, electricity generation is a couple of notches down the priority list for most Western dams. Storing and delivering water to the masses comes first, followed by environmental concerns, thus rendering the energy-generation aspect less flexible and robust. And then there's that nagging drought. The amount of water impounded behind Hoover Dam in Lake Mead has dropped precipitously over the last decade, thanks to less snow in the Colorado River watershed, higher temperatures and greater demand. Less water means less water pressure, which equates to less power generated from the dam on a daily basis. This phenomenon is on display now across California, where the nasty drought has significantly diminished hydropower production. An increase in wind and solar capacity has helped offset the decrease, but more natural gas power has been needed, as well.
And if Lake Mead keeps shrinking, the turbines will eventually become impotent. No one knows exactly what the level is — dam operators once thought it was 1,050 feet, or a mere 32 feet below the current level. But over the last couple of years, new turbines were installed in the dam, boosting its output and extending its power-giving life a little longer. In any event, it's probably prudent not to count on Hoover Dam being around forever, at least as a critical component of the electrical grid. Even now, it only produces about a quarter of the energy of which it's capable.
SALTING POWER AWAY
Enter Pathfinder. The proposed wind farm is massive, with a capacity just a bit larger than Hoover Dam's turbines. It could kick out as much as twice the amount of juice as Hoover has in recent years (and about half to two-thirds of that generated by coal-fired Intermountain). Excess energy will fill four huge underground salt caverns — the Pathfinder project's analog to Lake Mead — with enough compressed air to generate 60,000 megawatt-hours of electricity at any one time, according to the project proponents. A typical U.S. household uses about 10 megawatt-hours per year.
That's a big deal and, to say the least, ambitious; the day after the Pathfinder announcement, the largest battery storage project in North America was unveiled in the Tehachapi Mountains in California. It can store just 32 megawatt-hours. There are only two large-scale compressed air energy storage projects (CAES) in operation currently, one in Germany and one in Alabama. They serve in similar backup roles as hydropower: the German project helps smooth out the fluctuations from wind power, while the Alabama one is used to provide a little extra juice during times of peak demand. Both have been successful, but they are far smaller than the one proposed for Utah.
The technical challenges can be overcome. The bigger question is whether California, which has been beefing up its in-state renewable energy resources, will be willing to pay for all of that Wyoming wind power. The Power Company of Wyoming and TransWest Express project — with 50 percent more planned capacity than that proposed for Pathfinder — could double the amount of wind power in California's grid. There may not be room for more. But then, if Hoover Dam stops churning out the juice, something's gotta replace it. California could do a lot worse than Wyoming wind and Utah salt caverns.
*Proponents claim the Pathfinder wind farm would generate 9.2 terawatt-hours, or 9.2 million megawatt-hours, per year, which would amount to a capacity factor of about 50 percent. But the capacity factor of existing Wyoming wind farms tends to be closer to 35 percent, which would result in about 6 terawatt-hours per year.
Jonathan Thompson is a senior editor at High Country News.