The whine of the power plant sounds like a jet engine as refrigerant blasts through the turbine at 1000 mph. Though the equipment is compact, the din fills the vast hangar, and mechanical engineer Gwen Holdmann has to shout to be heard: "What you see here is very Alaskan. It's not painted. It's not pretty. But it's real." I place my hand on the steel door capping the plant's evaporator; it's warm to the touch, filled with Alaska's most promising new energy source--plain water.
It's midnight at Chena Hot Springs Resort, 56 miles northeast of Fairbanks, and outside, the July sun has only just slipped below the horizon. Holdmann's blond hair escapes a loose ponytail as she climbs onto a metal walkway to point out the heat exchanger. A black-eared husky named Amberlynn watches her every move from below. "The cool thing about this ... ," she begins, as she does most sentences, and it occurs to me that it's appropriate every time: This is cool. It is Alaska's first geothermal plant, and it's producing electricity from lower temperature water than any plant in the world.
Heat stored beneath the Earth's surface holds 50,000 times the energy of all the oil and gas in the world combined. If it could be harnessed, it would be an ideal source of base-load power: Geothermal is cleaner than fossil fuels, and more reliable than alternative sources like tidal, wind, wave and solar. Today, geothermal plants in the United States generate nearly 3000 megawatts of electricity--enough to power South Dakota. Almost all of it comes from reservoirs that are at least 300 F.
The water rising through a fracture in the granite pluton under Chena is only 165 F. Experts didn't think it was hot enough to produce serious power. But with the nearest electrical grid 32 miles away and generators burning through $1000 worth of diesel fuel daily, Chena had the incentive to prove the experts wrong. Now, its tepid water not only generates electricity, it heats the resort's buildings, maintains a greenhouse and keeps an ice museum frozen year-round. There are thousands of such low- to moderate-temperature geothermal systems scattered throughout Alaska and the rest of the country. Power plants like the one at Chena could tap them to produce tens of thousands of megawatts of electricity.
"I think we have an opportunity here in Alaska to be leaders in moving toward a more renewable energy economy," Holdmann says, her voice an equal mix of practical and impassioned. "The cost of power can be exorbitant in our villages--as high as a dollar a kilowatt-hour. It's a real bummer for a lot of these communities, but it can also be a real motivating factor." She pauses at the door of the hangar. "We're an oil-producing state and we're worried about our energy costs. It's just a matter of time before the rest of the country catches up to where we are."
Chena Hot Springs is the kind of resort one would expect to find on an episode of Northern Exposure. Nestled deep in a valley of birch and aspen, it has a comfortable, well-appointed lodge, an activities center, indoor plumbing and a resident masseuse. It also has a team of sled dogs, a 3500-ft. dirt runway, outhouses and, at this moment, a moose nonchalantly grazing near a geothermal production well.
Holdmann is well-cast for the setting. A professional dog musher, she lives off the grid with her husband and 80 huskies and commutes to work in a Jeep Liberty that runs on vegetable oil. She came to Chena four years ago as a hydropower consultant, but quickly determined that the water flowing under the resort was more valuable than the water flowing past it.
The only hitch: "Some of the reports I read from research on Chena concluded there was no way you could ever generate power out of this resource," Holdmann says. "I started to look into why, and began to realize it was a bit of a misconception."
When water cooler than 350 F is released from the pressure of a geothermal reservoir, it doesn't convert to steam efficiently enough to drive a turbine directly. Anything less than 230 F was considered too marginal for the alternative: a binary system that uses water to heat a fluid with a lower boiling point. But that threshold was a product of geography, not technical feasibility, Holdmann realized. A binary system just requires a heat source and sink: 165 F water can produce electricity if the ambient air or surface water temperature is at least 100 degrees lower. While that may be tough to find in the deserts of Nevada, in Alaska cold air and water are abundant resources.
Now all she needed was a plant, built to one important spec: "We need things that work up here," Holdmann says. "We don't need a bunch of things that, yeah, you can do in a lab. We need something we can take to a village and use normal people to run it. And run it every day, because we don't need it only half the time."
Fortunately, United Technologies Corp. was looking for a partner to collaborate on a pilot project: an air-conditioning unit that had been reverse-engineered to run off geothermal water. Instead of putting in electric power to create areas of high and low temperature, Chena provides the heat differential and the plant puts out electric power.
The technology has the added benefit of solving two remaining hurdles to low-temperature power generation. First, air-conditioning refrigerant operates more efficiently at low temperatures than isopentane and other fluids typically used in power plants. Second, the components are already mass produced, which cuts the cost of a small, modular plant in half.
Chena's two 200-kilowatt modules provide more than enough power for the entire resort and have reduced the cost of electricity from 30 cents a kwh to only 5 cents. With a capital cost of $2.2 million, including exploration and drilling, the project is expected to pay for itself in four to five years.
This fall, Chena and United Technologies received a Department of Energy grant to install a demonstration plant at an oil or gas well in the United States. The nation's wells produce at least 40 billion barrels of wastewater per year, much of it low to moderate temperature. That's another 6000 to 11,000 megawatts of potential electricity, according to a study by Southern Methodist University in Texas. "We feel we just need to show that it works," Holdmann says, "and companies will pick up on it."
165 F water, pumped three-quarters of a mile from Chena's 700-ft.-deep production well, enters the evaporator. After circulating through pipes, the water, now 135 F, is reinjected into the reservoir at a well 300 ft. from the power plant.
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The refrigerant R-134a fills the shell of the evaporator. Heat transferred from the 165-degree water causes the refrigerant to vaporize without the two liquids actually coming into .
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The vapor is expanded supersonically through the turbine nozzle, causing the turbine blades to rotate at 13,500 rpm. This turns a generator at 3600 rpm, producing electricity.
40 F water, siphoned from a shallow well 33 ft. higher in elevation than the plant, enters the con-denser without the aid of a pump. It circulates through pipes before being returned 9 degrees warmer to Monument Creek.
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Vapor exiting the turbine fills the shell of the condenser, where the 40 F water returns the refrigerant to liquid form.
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A pump pushes the refrigerant back to the evaporator, generating the pressure that drives the entire cycle so that it may start anew.
It's a balmy 68 F outside when I step through the heavy wooden doors of the Aurora Ice Museum with Bernie Karl, Chena's owner. Inside, it's only 21 F. He seems perfectly comfortable insulated by a fleece vest and a trim gray beard. I shiver in an oversize parka. "This is the largest ice structure in the world," Karl announces. Then, just as proudly: "Forbes magazine voted it the dumbest business idea of the year in 2004." That's because, with no refrigeration and an unusually warm summer, it melted. Or, as Karl likes to put it: "I took a frozen asset and made it into a liquid asset."
The enterprise appears solid now, or at least everything in it does. A wall of 2500-pound ice blocks, harvested from a lake last March, lines the right of the entrance; to the left, custom tools, including a row of Stihl chain saws with modified teeth, hang on an ice workbench. Heather Brice, a four-time world champion ice carver, stands over a vertical lathe, her slight frame covered in bulky layers and capped by a fur hat. Ice particles fly like sparks as she uses a spear bit to shape a frozen martini glass.
Heather and her husband, Steve Brice, a 13-time champion, created the museum's sculptures from scratch--twice--including a fiberoptic chandelier and a chessboard with 3-ft.-tall black-bear pawns and totem-pole rooks. The centerpiece is a stocked ice bar for which the Brices make up to 600 martini glasses a week. "Usually the glass outlasts the drinker," Heather says, as the bartender hands me an appletini. When my lower lip touches the frozen vessel and I take a sip, I realize she's probably right.
Judging by the tourists sitting on caribou-hide-covered stools next to me, an ice museum open during the summer season is not dumb at all. Before Karl took over the resort nine years ago, the business had been losing $1 million a year. Like most of Karl's brainstorms, this one just needed to be refined--a job best suited to a mechanical engineer. "This is like a playground for me," Holdmann says. "Bernie comes up with the big ideas and then gives me a ton of freedom to work out the details."
The ice museum is now kept frozen by an absorption chilling system. Though the concept has been around for more than 150 years, 230 F water was considered the minimum temperature required to be cost effective. As with the power plant, absorption chillers take advantage of a temperature differential--rather than a mechanical compressor--to create refrigeration.
A unique three-pressure system, invented for Chena by Energy Concepts in Annapolis, Md., uses an ammonia-water absorption cycle to chill brine circulating through an air handler behind the ice museum to minus 20 F. This generates 15 tons of refrigeration at the cost of about $12 a day; fuel for a traditional vapor compression system would cost about $200 a day.
For the first summer Holdmann was the only person who could run it, and after spending 18-hour days at Chena she would sometimes go home and then drive back at 1 am because it had gone down. Now the maintenance crew troubleshoots the system--leaving Holdmann free to refine the next big idea.
Alaska is not exactly famous for its long growing season, yet you'd never know it by the 50-ft. vines on the tomato plants at Chena. Half of a 4300-sq.-ft. greenhouse is devoted to growing seven varieties, hydroponically. I trail the greenhouse manager, Rusty Foreaker, through the other half, which has room for 2000 heads of lettuce in neat trays. He wipes his hands on dirt-smudged jeans and tears off a vibrant green leaf of Vegas butterhead. "Here, taste this," he says. It's surprisingly sweet.
Like most of Chena's produce before 2005, Foreaker came from the lower 48. He was working at a botanic garden in Peoria, Ill., when Karl visited and talked about his plan to build geothermally heated greenhouses in interior Alaska. "I thought it sounded like a crazy idea," Foreaker says. So he drove north to help.
Three years, two greenhouses and a garden later, the concept seems a bit saner. "We're working with green beans, squash, tomatoes, lettuce, herbs, cucumbers, bell peppers, strawberries, raspberries," Foreaker says. The crops are both an experiment with the University of Alaska Fairbanks and food for the resort. "Without geothermal, it would be entirely too costly to do this."
A district heating system links all 46 of Chena's buildings, saving $300,000 in heating fuel a year. Even when it's minus 50 F outside, the main greenhouse can remain a toasty 78 F thanks to hot water running through radiant flooring and air exchangers. The metal halide lights rely on geothermal, too, and during the near-total darkness of winter they are on 16 hours a day.
Karl has already come up with a new plan for Chena: hydrogen. "We're going to fill vehicles with it," he says. Holdmann's take is more practical, but no less ambitious: Use biodiesel in the resort's vehicles and blend hydrogen gas with the propane still used for cooking, displacing some of the fossil fuel and saving $10,000 a year. The University of Alaska Fairbanks has donated an old electrolyzer for this purpose, and I go with Gwen to its Arctic Energy Technology Development Laboratory to retrieve it.
Inside the loading dock, Holdmann picks up a flathead screwdriver and begins to disassemble the elaborate machine, part by part. I ask Dennis Witmer, the lab's director, what it's worth. "Gwen, how much are you paying me for this piece of crap?" he says, laughing. Then he explains the math behind why he's giving it away: The electrolyzer needs 18 kw of electricity to split water molecules into 10 kw worth of hydrogen. If the electricity is derived from fossil fuels, that's far too inefficient.
Holdmann, however, plans to use surplus electricity generated by the geothermal plant. "This is my way of doing something with hydrogen that makes sense," she says. "The hydrogen this electrolyzer produces using green power will go to fill a need." She just received a grant from the National Science Foundation to track the economics for Alaskan villages. "What doesn't make sense in New York City today might make sense in rural Alaska, where they're paying $8 a gallon for fuel," she says. "The economics are different here, but it's all a precursor for what we're going to see in the rest of the country. I really believe that."
Sure, mi the hydrogen and propane gases may be tricky. "It's not that it hasn't been done, but ... it kind of hasn't been done, actually," Holdmann says. Everyone agrees that it should work; it's just that, outside of a lab, no one's ever tried it. Which is, of course, when the folks at Chena step in.