Geothermal: Touring The Geysers

The cooling tower for the West Ford Flat power plant, which is part of The Geysers, the world's largest geothermal power development. (Photo credit: Wikipedia)

Driving north on the 101 up the California coast, I stifled a yawn. Partly because I’d started out early, around 6am, to make a 9am interview and tour I’d scheduled at The Geysers–a complex of geothermal energy plants about two and a half north of San Francisco. But also because the thought of spending an entire day touring a geothermal energy plant wasn’t exactly scintillating. When I began working on this book, geothermal was way down on the list of things that seemed exciting. Standing in the shadow of a towering wind turbine? Very cool. Walking among the sleek, futuristic-looking panels of a working solar farm? Intriguing. Even surveying a field of giant grass that might one day help wean us off gasoline had its appeal.

But geothermal?

I really wasn’t sure what to think. There are no iconic images associated with geothermal energy, as there are with solar and wind. Several Google searches had dug up a handful of pictures of ordinary looking power plants–squarish, industrial buildings coughing white steam from concrete silos. Not exactly eye candy. Serious geothermal action, like the kind the supercharges the hot springs and geysers at Yellowstone, takes place mainly deep underground, I knew, where rocks superheated by the earth’s natural body heat produce either steam, hot water, or just plain old heat. Tap that heat, channel it to spin industrial turbines, and presto: you’ve got geothermal powered electricity.

Reliable? Yes. Interesting? Kinda. Jaw-droppingly cool? Not so much.

Of course, I had learned a few intriguing facts. For one, geothermal is by far the most constant renewable resource for large-scale electricity production. The sun shines only during the day. Wind comes and goes. Energy crops have to be laboriously harvested, processed, and replanted. Even ocean and river currents ebb and wane. But the earth’s internal heat is steady: always there, always on. And there’s a lot of it–an entire planet full, really. Similar to solar advocates’ popular mantra that enough sunlight falls on the earth every minutes to meet the world’s energy demands for a year, geothermal proponents have their own astonishing statistic: within about 10,000 meters (33,000 feet) of the earth’s surface there’s enough heat to provide 50,000 times more energy than the world’s combined oil, coal, and natural gas resources.# In other words, the planet contains way more than enough naturally occurring, non-polluting, carbon-dioxide free heat to provide for humanity’s energy needs basically forever. (The rub is that only a relatively small amount of the earth’s heat is capable of producing lots of steam at pressures high enough to turn an industrial-strength turbine is easily tapped; most of the planet’s hot rock is buried miles underground and lacks an indigenous water source to produce naturally-occurring steam. More on this later.) At the moment (that is, in mid 2011) several dozen geothermal power plants generate around 10,700 megawatts of energy around the world–a relatively tiny amount that’s projected to grow to at least 18,500 megawatts by 2015.

And concerning The Geysers, the world’s largest complex of geothermal power plants, there was the intriguing historical “fact” (albeit probably apocryphal) that the place owed its existence to a grizzly bear that had been menacing trail blazers and homesteaders (in what would become northern California’s Napa and Lake counties) in the mid 1800s. Or more specifically, the geothermal region that came to be known as The Geysers owes its discovery and moniker to the man charged with hunting and killing the grizzly: an explorer and professional bear trapper named William Bell Elliot. An 1881 pamphlet, History of Napa and Lake Counties, California: Comprising Their Geography, Geology, Topograhy, Climatography, Springs and Timber, describes Elliot in mythic language: “On the plains, Elliott was a leader. He did not know the meaning of the word fear. Armed, he did not care a snap for Indians, and would have toppled them over if they interfered with him with as little compunction as he formerly knocked gray squirrels out of a tall poplar or chestnut tree in the mountains of West Virginia [where Elliott was from].”# One day, according to the History, out on a bear hunt, Elliott and his son (one of seven) came across some Native Americans, possibly of the regional Lake Miwok tribe, who pointed him toward a good spot to find grizzlies, over the mountains to the west. Several hours later, descending a divide between what came to be known as Big Sulfur Creek and its main tributary, Elliott and son got a strong whiff of sulfur. (He would have recognized the odor as what was known as “brimstone”.) Curious, they followed the creek and were soon stopped in their tracks by a spout of steam hissing noisily from the ground. Glancing around furtively, they noticed other towering columns of steam spiraling up from the earth and felt the ground trembling beneath their feet. Elliott and his son looked at each other and began to tremble themselves: they’d discovered the gates of hell! Just then, as if on cue, the very grizzly they’d been tracking (or possible another bear) reared up, bared its teeth, and roared. Despite the netherwordly surroundings, Elliott and son remained cool, shooting the bear to death before fleeing back to civilization to report what they’d seen.  [AN AMUSING STORY, I THINK … BUT IS IT TOO CUTE, OR JUST PLAIN IRRELEVANT?]

That’s the story that became part of the region’s lore, anyhow. What Elliott had actually discovered was a part of the geothermally active region that came to be know as The Geysers–a curious misnomer, given that the area includes no actual geysers. (The steam vents are technically known as “fumaroles.” Geysers, like Yellowstone National Park’s famous “Old Faithful,” spout liquid water.) Of course, as is nearly always the case with “discoveries” made by white settlers in the American west, the region had been well known to the native inhabitants for thousands and possibly tens of thousands of years. Native Americans of the Lake Miwok and Wappo tribes used it as a natural pharmacy, bringing their sick to wallow in the bubbling mud pools and hot springs and to drink the mineral water that owed its reputation as a miraculous cure-all to its potent laxative properties.

Approaching the modern day Geysers visitors center, it wasn’t hard to imagine what the place might have looked like during the mid 19th century. The area is still largely rural and has the look and feel of untrammeled wilderness, despite the presence of 22 power plants spread out over 45 square miles in the Mayacamas Mountains. Charlotte Doherty, head of safety at The Geysers, met me inside the center, near a large-scale plastic model of the entire, sprawling complex. A veteran of the California oil boom of the 1980s, Doherty had been with Calpine (the energy company that currently owns The Geysers) since 1989, first as an environmental chemist, for the last  ten years as a health and safety expert. She quickly took me through the basics: The Geysers is a dry steam operation, meaning that steam is mined directly from naturally occuring reservoirs miles underground. (Dry steam power plants are rare, making The Geysers something of an outlier. Most geothermal plants of are of the flash steam variety, where hot water is pumped from the ground into a low-pressure tank, which causes it to vaporize, or “flash”, into steam used to run a turbine. And, increasingly, some plants use a binary-cycle system, where hot water pumped from below is used to heat another liquid, which then flashes to vapor.)

“It’s really pretty simple,” Doherty said as we got in her truck and headed out toward one of the power plants. “We make electricity the same way it’s almost always been made: the steam goes to the power plants and turns rotors that create electricity.” Most of the steam is then condensed back into water, although some becomes a gas which is cleansed of pollutants and vented to the atmosphere. Yet, as Doherty went on the explain, making power at The Geysers is actually more complicated than it might appear, especially when it comes to harvesting steam. In the mid to late ‘80s, steam production at many of the plants began to decline. After nearly 30 years of mining, with dozens of wells siphoning stream from the natural reservoir, the underground water source necessary for producing the steam began to be used up faster than it could naturally replenish. Or, as Doherty put it, as more and more wells had been added over the years, and before long, “instead of just a few straws in the milkshake, there were a few dozen, every one sucking just as hard.”  So, in effect, dry steam geothermal was revealed to be a not entirely renewable resource–at least not in the classic sense. Unlike wind and sun, superheated underground steam could be used up. But Geysers engineers have found a clever way of replenishing the supply. For years, northern California municipalities had struggled to safely treat and get rid of their waste water; The Geysers’ decline presented an unforeseen and fortuitous solution. In 1997, Sonoma county began pumping treated waste water through a 40-mile-long  to The Geysers steam fields, where it was injected down specially reconfigured wells to replenish the underground water source and boost steam production. In 2003, the cit of Santa Rosa joined the effort, sending 11 million gallons of waste water per day to The Geysers.

From the outside, a geothermal power station looks a lot like a coal-fired (or any other) plant. And from the inside, too. The interior of the plant I visited, the West Ford Flat station, was dominated by the turbine apparatus: basically a block-like, school bus-sized metal casing concealing the turbine. A large, matte-green tube piped high pressure steam inside the casing to spin the turbine’s rotors to generate electricity. Like the coal-powered plant I’d visited in Indiana, the geothermal plant was loud, making it hard to speak and be heard over the turbine’s mechanical roar. The control room, too, looked familiar: a couple of guys in work clothes, sipping coffee, monitoring a large board with lots of lights and switches, ready to leap into action if anything went wrong, but mostly just watching to make sure that everything was running smoothly.

But entirely unlike the coal plant, West Ford Flat was conspicuously clean. At the heart of every coal-burning power plant is a multi-story boiler containing a massive, perpetual explosion of incinerated coal. The 24-hour, seven-days-a-week piping of coal particles through the plant and into the boiler leaves everything coated with a thin layer of dark, smudgy dust. And to keep all that dust from blowing around, coal plants are shut tight. Consequently, the boiler and turbine areas look and feel like a scene straight out of Dickens, or the Terminator movies: dark, loud, dirty, and dominated by large machines. Geothermal plants, by contrast, are loud but strangely clean. They’re also relatively small. Since the steam-generating “boiler” of a geothermal plant is the earth itself, the building doesn’t need to be large enough to contain a giant metal boiler. And because there’s no need to keep toxic coal dust from being swept up into the air or throughout the surrounding countryside, a geothermal plant doesn’t have to be quite so locked down. On the day I visited West Ford Flat, open windows and doors let in plenty of natural light.

Outside, we walked a few hundred yards toward a bunch of dull green tubes snaking out of the forest and converging at a central, boxy apparatus: the plant’s steam-feeding mechanism. Four wells fed steam into West Ford Flat, Doherty explained. Made of fiberglass encased in metal jacketing, the tangle of 24-inch diameter tubes had the look of a giant Habitrail. Although they weren’t particularly hot to the touch, the steam flowing inside them topped out at around 340 degrees Fahrenheit.