Supplying power to the outermost reaches of the outermost state in the union is difficult enough under normal circumstances. Throw in high fuel costs that have resulted from a burgeoning global middle class with a considerable energy appetite, as well as recent geopolitical and climatologic instability, and you start looking for ways to ease a burden that threatens the very economic viability of many businesses. Nowhere is the burden more apparent than for organizations that are actually in the business of producing energy, such as the Alaska Village Electric Cooperative (AVEC).
This organization supplies electric power to 52 remote communities in Alaska and, until recently, relied almost exclusively on the use of diesel gensets. AVEC operates over 144 diesel generators that run a cumulative total of more than 410,000 hours per year. This reliance on diesel, notes Brent Petrie, manager of key accounts for AVEC, creates some major cost and logistical challenges.
“We buy about 5 million gallons of diesel a year,” says Petrie. “Our average fuel cost in 2003 was about $1.49 a gallon. In 2004, it jumped to $1.94, and in 2005, it was $2.09. So in a two-year period, our fuel costs have jumped about [40 percent].”
The remote locations’ inaccessibility and necessary storage facilities are the fuel cost drivers, notes Petrie. “We have 48 power plants; in some cases, we have to fly the fuel in to villages. Diesel is the most reliable fuel source that we have—it’s very flexible, very versatile. But we’ve had to build storage facilities for it, and that’s a huge cost. In many cases, our fuel is only delivered once a year, so we have to have fuel storage that provides for the needs of the village and for our plant for an entire year.”
The unique climate of Alaska necessitates unique construction for diesel storage facilities in these remote villages. Storage is a major consideration “because we have permafrost and, in some cases, we have to build our tank farms on pilings,” says Petrie. “We set them up above the tundra in order to keep the tundra frozen. We do that by elevating the tank farms and allowing the cold air in the wintertime to blow underneath the tank farms and keep that ground frozen” for stability.
Wind Eases Burden
While AVEC does not foresee the complete replacement of diesel as the main fuel source for its remote power generation, wind power serves a niche purpose of supplementing diesel. By the end of 2005, the co-op completed installation of three 100-kilowatt wind turbines in the western Alaskan villages of Toksook Bay and Kasigluk, bringing the total of turbines purchased from Waitsfield, VT-based Northern Power Systems Inc. to 10—considered the largest investment in wind turbines within the state in one year. The first three turbines that AVEC installed are expected to provide a reduction in diesel fuel consumption of about 52,000 gallons a year and approximately $100,000 in annual energy costs.
“These are small villages where, typically, the air quality is very good,” according to Petrie. “Diesel is very reliable, but it’s also very costly, and the cost of storing it is also an item because we also have to build these fuel facilities that are capable of storing the entire year’s supply. Wind can help us extend the life of our fuel storage facilities and lower the cost for power generation—that’s the main thing we’re looking at.” Installation and maintenance of wind power systems presented its own challenges, however.
AVEC’s initiative to reduce dependence on diesel actually began earlier this decade, when the organization began investigating ways to implement wind power at its remote power plants. Current plans call for the ultimate integration of wind power into AVEC’s 51 remote villages. A pilot project was conducted in Wales, AK, in conjunction with the National Renewable Energy Laboratory (NREL), and AVEC also utilized wind in another project in Selawik, both of which utilized NorthWind 100 turbines. Additionally, since being installed in May 2002, AVEC has operated a NorthWind 100 in temperatures as low as minus-39 degrees C and has had the highest energy capture of the turbines at a wind farm in Kotzebue.
Having experienced success with these turbines, AVEC ordered three more NorthWind 100 turbines to be installed in Toksook Bay and Kasigluk, which feature a harsh winter environment, by the end of 2005. The turbines’ harsh operating environment presented a challenge for Northern Power and AVEC.
“In Alaska, there are some unique geological conditions: you have cold permafrost, you have warm permafrost, there’s gravel, and bedrock,” notes Brett Pingree, project manager for Northern Power. “Where we’ve installed our turbines in Toksook and in Kasigluk, that’s an area we call the YK Delta, where the Yukon River and the Kuskokwim rivers form a delta, and there are a lot of villages there. It just so happens that this delta, composed of glacial silt that has formed over thousands of years, creates this really mucky, wet clay, silty permafrost; that’s one problem. The other problem is that in the YK Delta, it’s only taken a half a degree increase in temperature, and that half a degree in the summer has pushed the permafrost over the melting point. You have the silty soil and then it gets a little bit warm in the summer and it gets mushy.” In order to counteract the unstable soils, AVEC put a lot of investment, engineering and time into construction of stable foundations for the towers.
“For us, it’s a pioneering effort because if you look at a tower in the Lower 48, most of them are sitting on a block of concrete, and the point of fixity is basically at the base of the tower,” says Petrie. “In our case, the point of fixity is at the frost line; the frost line varies throughout the year, as the frost line in the ground goes up and down, and you have to engineer that whole arrangement of the turbine, the tower and the foundation together so that you’re capable of holding that tower stiffly so that it doesn’t develop an adverse vibration or frequency when the rotors are operating. We had to basically create a frame that tied in the pilings at the base of the tower and stiffened everything.”
Maintenance of the units is also a challenge in an environment with such high winds and frigid temperatures. Pingree, mindful of the fact that many wind turbine manufacturers are offering large-capacity units from 1.5 to 5 megawatts, points out that the NorthWind 100 turbines are designed with several premium features that one would expect to see in a much larger turbine. They are direct-drive, not gearbox-driven, units, which reduces the number of moving parts. “With a gearbox, there are multiple sprockets, gears with teeth,” Pingree notes. “There are multiple sets of those that are connected. As the blade in the hub turns, they turn all of the different gears with teeth; that transfer of energy is passed through the gears. You have a lot of gearboxes that need replacing, a lot of gears that get chipped and worn.”
Pingree says he’s not aware of another 100-kilowatt turbine with an enclosed nacelle, which makes maintenance possible in the frigid temperatures found in the villages in which AVEC has had the turbines installed.
“In case we have to maintain them in inclement weather, we can go up into the tower and work in the nacelle,” says Petrie. “That’s an advantage; we have had icing conditions in one location where it would have been advantageous to work inside the tower.
“We also did some special things on these machines. We specifically selected black blades—that’s rather unique.” Maintenance personnel also coat the blades with an antifreeze agent. “The purpose of our adding that coating was to able to keep ice or frost off and maintain production during icing-type events,” Petrie continues. “Last November, we had an icing event, and we were able to allow rotors to face the south. When a weather front moved through, we had about four hours of sunshine, even though it was 15 degrees F. We were able to remove the ice and go back into production.”
Another feature is the turbines’ optimization for low-speed operation. “There are limited class-6 wind sites,” Pingree notes. “There are only so many of those in the U.S., and many more times as many class-3 and -4 wind sites” for which the turbine was designed. “Our turbine spins more than the other turbines, and at a lower wind speed our turbine is able to start spinning and actually produce some power.”
Adds AVEC’s Petrie, “We may have windy conditions at 20 below zero; when it’s that cold, the air here in the arctic and subarctic is more dense, so the turbines need to operate in extremely cold temperatures in air that is more dense than typical operating conditions in the Lower 48. We get more production out of the machine that way.” On other turbines, you’ve got a gearbox full of oil, and you have to warm up. When you have other machines with oil-filled gearboxes, you have to have oil that is less viscous. With these types of machines, there are no worries.”
Pingree, describing the NorthWind 100 as a unit designed for applications such as AVEC’s remote villages, says that addressing the units’ penetration level is a key consideration, as they are supplying partial power to the local grid. “What’s the demand of the system, what’s the demand of the grid, and how much are we gonna be able to contribute?” For the purpose of providing partial power, the system installation utilizes a waste heat recovery system. “You can put excess wind generation that’s not being put on the grid into what’s called a dump load boiler; that takes that excess wind energy and boils water,” Pingree says. “That was a little bit of a complicating factor—just figuring in the installation of the dump load boiler. We were really waiting for them to get that dump load boiler installed so that we could let all three turbines rip at full capacity; without the dump load boiler, we couldn’t let all three turbines go full bore.
“In the middle of the night, when all the TVs are turned off and all the lights are off, you’ve got a low demand, and the wind might be blowing 25, 40 miles an hour, and we had to restrict the use of the turbines; we couldn’t let them rip at full power because they would just overpower the grid. That’s where the dump load boiler comes in; that excess energy that’s being created that can’t be put on the grid would get diverted into the dump load boiler, and the recovered heat from that would heat the school, heat other buildings. They use that hot water as a heating source.”
Keeping An Eye On Things
Given the remote locations of the turbines, monitoring normally would have posed a challenge to AVEC. The solution was to also purchase Supervisory Control and Data Acquisition (SCADA) systems utilizing Northern Power’s SmartView software, which will allow AVEC to monitor and control the wind turbines in both villages, as well as the organization’s diesel gensets. The SmartView software works on a Web-based platform and provides a graphical user interface with visual representations of various turbine components’ operation.
“You can see a representation of the turbine spinning, you can read the graphs, it’ll tell you what the wind speed is, what the ambient temperature is, how much energy is being produced, the temperature on the brake, the safety system, the temperature of the generator,” says Pingree. “It basically gives you insight into all the components of the system. It also gives you the ability to start and stop the turbine remotely, so if for some reason you felt that you needed to stop the turbine, you can do that; you can put it into service remotely, and you can put it back on remotely.”
Petrie says that the remote monitoring system comes close to allowing AVEC to keep tabs on all of the inner workings of the turbines, although the system can’t replace the onsite technician’s personal vigilance. “We have a local operator who checks the equipment several times a day, and we also have automated switch gears,” he says. “We’re not able to monitor all of that remotely, but you can put a small programmable logic controller on the plant; if the load gets to a certain level, it starts another engine, puts it online and drops the other engine offline.”
However, the system produces data that really didn’t exist before, Petrie adds. And, it collects the data without active intervention by personnel. “You’re able to see trend information that you were not able to see before; that helps us quickly diagnose,” he says. “We’re capturing information on temperatures of the equipment, loading of the wind equipment, loading of the diesel equipment, temperatures of the coolant and on the power plant—all of this is coming in an automated manner where the values are sent and recorded every 15 minutes.
“The alternative way was where the plant operator had a clipboard with a piece of paper on it, and they would jot down the time that they took the reading. Some operators were very diligent about doing that. In other cases, maybe something would happen where there’d be a family emergency or something and the operator might not be able to fill that out like they had previously; there might be a gap there. The nice thing about the SCADA system is that it records the values whether or not the person is there, and those values are there for diagnostics.”
Pingree sees no reason why the SmartView system can’t be used to monitor all of AVEC’s power systems. The system already monitors the co-op’s diesel gensets in Toksook Bay and Kasigluk. “We’re talking to AVEC about having all of their villages do this and they can be in Anchorage and have a very centralized approach to monitoring their power sources in remote locations,” says Pingree. “Even in Anchorage, it costs them a couple of thousand bucks to fly up to a village for a day. It’s not that unusual for guys to get stuck in a village for a week due to weather.”
Not A Complete Replacement
Despite the early promise of wind supplementing diesel power in AVEC’s remote villages, AVEC does not see wind completely replacing diesel anytime soon, if ever. Petrie reiterates diesel’s versatility and reliability. However, “I can say that we expect to expand our wind turbine fleet,” he says. “Of the 52 villages we serve, mostly in Western Alaska, 27 of those villages are in a class-4 wind regime or better, and they are not connected to any grid; they are currently isolated diesel systems. If we can master the integration of the wind and the diesel, we have several places where we can employ this technology to save on fuel.”
But AVEC has found that wind power has firmly established its niche as a reliever of the substantial cost burden inherent in diesel fuel. “We envision wind as a fuel saver; we don’t envision the diesel plant going away,” Petrie adds. “What we want to get better at is integrating wind and diesel, making them operate more efficiently together so that we get higher use out of wind and not have any adverse control issues with the diesel plants.” DE
Communications specialist DON TALEND resides in West Dundee, IL.
DE - May/June 2006
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