Powering the Dream_ The History and Promise of Green Technology - Alexis Madrigal [128]
For too long, we have suffered from an Edison complex, delusionally believing that some superhero inventor will solve the energy problem. The truth is that energy technologies don’t work like that. The development paths are grinding and long because the levels of reliability required are high. If governments are going to invest in them, they have to be willing to act consistently and for many years at a time.
In February 2009 the production tax credit for wind was extended for three years, and given the economic tough times of the period, this allowed credits to be converted into grants. Without the moves, which were included in Barack Obama’s stimulus package, the industry might have collapsed again. “The stimulus package essentially saved the renewable-energy industry in the United States,” a venture capitalist told The Atlantic.68
Perhaps American energy policy is finally growing up.
chapter 25
Energy Storage and the Return of Compressed Air
IN 1991 A SMALL POWER PLANT opened up in McIntosh, Alabama, operated by the Alabama Electric Cooperative, one of the old public utility companies that brought power to the hinterlands of the deep South.
There was little fanfare. No one reported from the gates of the plant, which is located in a rural area about forty miles north of Mobile. It wouldn’t have been much to look at on the surface anyway. The plant’s footprint is about the same as the small high school that sits across Jefferson Davis Highway, if we include its football field and baseball diamond. A chemical factory in the area dwarfs the plant.
What matters about the McIntosh project is not so much what’s happening where you can see it but actually the action deep underground. It sits atop a large salt dome, the kind of geological structure that was an early target for wildcatters looking for oil. Petroleum and natural gas tend to get trapped underneath these impermeable rocks: Poke through the layers of salt and sometimes people can slurp up some hydrocarbons. A gas company explored this particular dome in 1945, and when it came up dry, Olin, the chemical manufacturer, purchased it, using the salt for various purposes.1
For decades, the dome lived a relatively quiet life until 1987, when two small test wells pushed down into it. Geologists looked at the rocks that came back up and decided that one area had salt that was perfect for what they were planning: solution mining. They then pumped water down wells, which dissolves the salt, then pumped the briny water back up. What’s left over is a cavern underground. For every fifty gallons of water they pumped down, they made one cubic foot of cavern. And the best part is that the salt heals itself up, becoming impermeable again.
In October 1988 an engineering contractor drilled a hole that reached 2,400 feet underground. Then the water pumping began. The briny water got passed off to Olin for use in making chloralkali. The cavern grew. By November 1990, the cavern ran 900 feet long and had a maximum diameter of 238 feet. It had a cubic volume of 19 million square feet. It is shaped roughly like an ear of corn inserted into the ground tip down.
What would anyone possibly want a corn-shaped cavern underground for? To store energy. The cavern acts like an underground pressure vessel, storing up power for later use. During off-peak times, when electricity is cheap, they can run that electricity to air compressors, which pump pressurized air into the cavern. Then, when electricity is expensive, they flip the switch and run that compressed air through a turbine with some natural gas. They have effectively stored the electricity to be used for later. The current state-of-the-art technology uses the wind electricity to reduce the amount of fossil fuel that’s burned in the generator by 60 percent, and future designs hope to eliminate combustion altogether.2
McIntosh and its salt dome hardly seem like a key destination on the map to the future of renewable