Editor's note: This story has been changed to correct an annual rate orginally described as a monthly rate.
Since 1991 the Bradley Lake Hydroelectric Plant has been quietly spinning its turbines on the south side of Kachemak Bay, turning the gravity-driven flow of water into electricity that turns on lightbulbs across the Kenai Peninsula. As long as the lake stays full, the project will continue pushing electricity in the Railbelt electrical grid.
“Hydro’s super simple,” said Bob Day of Homer Electric Association, a Power Production Manager at Bradley Lake. “You have water, it’s under pressure, it makes a wheel go round, the wheel turns a generator. It’s all low-speed, and as long as the bearings stay lubricated and the electrical equipment stays insulated, life is good.”
Day is one of the HEA employees who, working in rotating crews of five, sees to those requirements at Bradley Lake. He has been living at Bradley Lake in weekly shifts since 2006, and said he hopes to spend the rest of his career working on the project. He describes Bradley Lake as an apt place for hydropower.
“A hydro installation is really about location,” Day said. “...You have to have a good source of water, you have to have elevation, you have to have a place to put the power plant. You have to be near, or somewhat near civilization.”
Most of Alaska’s hydropower potential is concentrated in the mountainous panhandle, but Bradley Lake, about 27 miles from Homer, is one of the few locations on the Kenai Peninsula with the features Day described. The mountain lake, fed by meltwater from the nearby Nuka glacier, empties in turn into Kachemak Bay via Bradley Creek.
The Army Corps of Engineers studied the lake as a power source in 1955, and Congress authorized its development as a power source in 1962. But the project stalled for lack of funding until the state-owned Alaska Energy Authority took it over in 1982, funding the $328 million construction effort with legislative appropriations and bond sales.
A concrete-faced dam raised the lake 100 feet from its natural level. Propelled by gravity, water flows into an underwater opening, through a 3.5-mile tunnel in which it falls through a 760-foot vertical drop to reach a powerhouse on the shore.
The powerhouse’s two turbines are propelled by Pelton wheels — a type of waterwheel that uses pairs of spoon-shaped paddles to capture nearly all the flow’s energy. Large nozzles, similar to the smaller ones found on the ends of garden hoses, shoot a pressurized spray at the Pelton wheel’s blades. The flow can be controlled by needle valves in the nozzle’s opening. Each of the two turbines can generate 63 megawatts of power. Due to the limitations of the powerlines that carry electricity from Bradley Lake, however, the plant normally limits its output to 90 megawatts.
The plant is currently limiting its output further to complete a maintenance project.
The lower reach of Bradley River, where it spills into the marshy east end of Kachemak Bay, is listed by the Alaska Department of Fish and Game as spawning and rearing habitat for coho, sockeye, and chinook salmon. The river is kept intact with a tunnel diverting water from the dammed lake.
One inlet of this diversion tunnel had been stopped up with silt. In order to access the inlet for cleaning, engineers had to draw enough water from the lake to drop to its natural, pre-dam level. Although the diverson tunnel opening has been cleared, the lake still lies below the foot of the dam. With the diminished water level, only one turbine is currently producing power, putting out 3 megawatts used mostly to run the power station itself. Day said the staff are waiting for the lake to be refilled by nature, via rain and meltwater.
Most of Bradley Lake’s water melts from Nuka glacier, where a 10-foot gravel dike directs runoff into the reservoir. Another diversion is planned for the nearby Battle Creek ridge, where snowmelt naturally flows down the slope opposite Bradley Lake. According to a fact sheet from the Alaska Energy Authority, if that meltwater were instead contributed to Bradley Lake, it could increase the facility’s average annual generation by 10 percent.
The state continues to own Bradley Lake, although it is managed under contract by HEA. When the rules governing the project were created in early 90s, the state assigned percentages of the plant’s output to six different utilities — HEA, the Chugach, Matanuska, and Golden Valley electric associations, and the municipal governments of Seward and Anchorage — based on their relative sizes. Those percentages have remained in place since. HEA has a 12 percent share of Bradley Lake’s power. Geographically, Day said that around 88 percent of Bradley’s average annual output of 380,000 megawatt hours goes to Anchorage and Seward.
“Homer Electric right now is (using) on the order of around 470,000 megawatt hours a year,” Day said. “So if Homer Electric owned Bradley 100 percent, we’d still be about 10, 20 percent short in terms of energy. Bradley could carry most of the Kenai — not all — but that’s not the ownership situation.”
For HEA users, the difference is made up by HEA’s natural gas-fueled power plants in Nikiski and Soldotna.
“That’s typical,” Day said. “When you look at the Railbelt utilities — Golden Valley to Homer Electric — they’re typically about 10 percent hydro and 90 percent gas-fired.”
Economically, comparing gas-fired electricity to hydro electricity requires considering both the cost to build a generating plant and the cost to fuel it.
“It (a hydropower plant) costs a huge amount of money to build,” Day said. “With hydro, you typically spend a lot of money on your capital, and very little on your fuel. With gas-turbines, you spend not so much on your capital expense, but you spend a lot on your fuel.”
With the current price of natural gas, Day estimated that gas-fired electricity costs around $80 per megawatt-hour, while Bradley Lake electricity was about $43 a megawatt — or, reduced to the scale of home power consumption, about 4 cents per kilowatt hour for Bradley Lake electricity and about 8 cents for gas-fired power (an average household uses around 620 kilowatt-hours a month according to Day, though HEA manager Brad Janorschke said that with warming winters the usage has dropped to around 550 kilowatt-hours a month).
Added to that cost is the capital investment of creating Bradley Lake’s cheap power, which is still being paid. The Alaska Energy Authority financed the project with $260 million in bonds, which it continues to pay with revenue from Bradley Lake power.
Janorschke said the bonds are being paid off gradually, within a 30-year span.
“If you sold the power at the price it would cost to replace it with natural gas-fired generation, you’d have (the bonds) paid off in no time,” Janorschke said. “But because it’s only 4.5 cents per kilowatt hour, there’s no point paying it off any sooner than you have to, because you’re charging today’s customers more than you have to charge them. ... We spread the cost out over the expected life.”
Janorschke said hydropower facilities have very long lives — two of the hydropower plants powering Juneau are 100 years old — and that hydropower becomes progressively cheaper as the capital cost is paid off.
Technologically, Day said hydroelectricity as “a stodgy industry” that has changed little in the past century, never mind Bradley Lake’s present life. The Pelton wheels that spin its turbines were based on a design perfected in the 1870s. Communications technology is one major change — Bradley Lake is controlled from Anchorage via a fiber-optic connection. Day said most of the technological change has been in the plant’s software.
“Bradley is a baby in terms of hydro facilities,” Day said. “Not a lot has changed. The big change has been the control systems, the computer systems, the communications systems. But the basic hardware was designed in the late 1800s. ... They have stuff that works, and it’s real basic, and you’re not going to change it much.”
Reach Ben Boettger at firstname.lastname@example.org.