ONWARDS AND UPWARDS - Bent Tree Wind Farm Site Manager Greg Kaelberer exits one of the 121 currently operating units near Hartland. Up to another 80 units may be constructed in the relatively near future.
Star Eagle photos by Deb Bently
By DEB BENTLY
Staff Writer
Talk with site manager Greg Kaelberer at Bent Tree Wind Farm for a few minutes and you’ll see why the word “farm” is more than a figure of speech when it comes to the nearly 20,000-acre farm just south of Hartland.
The thing is, when Kaelberer speaks of his “harvest,” it occurs nearly constantly—up to 400 feet in the air, using 130 foot long blades.
Apparently, when you think of wind power, you have to learn to think on a very large scale.
From a distance, Bent Tree and its turbines have looked much the same since they were constructed back in 2010 and began operation in 2011, but from Kaelberer’s perspective, things are always changing. For one thing, he and the company’s 10 other employees have to keep the site’s 121 units operating, which means running a maintenance regimen every six months or so on each of them.
The workspace inside the turbines is, according to Kaelberer, about the size of a camper, so crews of four and their equipment can fit easily. And they don’t have to climb 200-some stairs to get there: “Most people are surprised to learn that there are elevators inside each unit. They’re big enough to hold two people and some equipment, although it can get a bit tight at times.” For backup, there are also ladders.
For anyone who’s starting to feel dizzy at the idea of working 262 feet in the air, Kaelberer emphasizes that there are strict safety protocols. In more than 10 years of operation, the site has never had a serious accident.
Another way that things remain fluid is the amount of power being generated. Obviously, a major factor is wind flow. To use Kaelberer’s perspective, each wind generator “harvests” power from a space as big as 82 meters, the circle its blades travel, an area about the size of a football field. The faster that air is moving, the more power is generated.
Even with the ups and downs of wind flow, each turbine creates enough energy each year to power more than 400 homes. For that same span of time the entire output from the farm would supply about 50,000 houses.
For the truly curious, a “Wind Resource Map” produced by the U.S. Department of Energy is available online. A quick glance shows that, across much of southern Minnesota, winds at 400 feet are typically about 18 mph (8 meters/second). According to a Bent Tree publication, power can be generated beginning at 8 mph, reaching optimal levels at 28 mph, and losing feasibility at 47 mph, at which point the blades are set to stop spinning.
When it comes to consistent winds, Kaelberer says, flatter land is better. Factors such as landscape, structures and trees can have significant impact. His statement is supported by the fact that, according to the Wind Resource Map, wind speeds drop by more than 2.5 meters/second around the Minnesota River Valley less than 40 miles away.
Along with its optimal winds, the Freeborn County location has two other assets which make it desirable. One is that landowners—88 of them so far—have been receptive to the construction and maintenance needs which are part of harvesting wind. This is especially good news given that Bent Tree is looking at the possibility of expanding, probably to the north of its current location. According to Kaelberer, talks with affected landowners have begun. Someday another 50 or so turbines may be constructed.
The new units will probably look very similar to the existing ones, although they are expected to be slightly larger and more widely spaced. What the typical passerby will not be able to see is that, thanks to developing technology, they are likely to cost significantly less to construct, yet generate one and a half to double the amount of power.
The third desirable element offered by the current location is one a typical passerby might not think of: access to a reliable power transmission system. That asset comes in the form of a major power line just north of Albert Lea. Managed by the Independent Transmission Company (ITC), the line delivers power to a grid which extends across several states. This is especially beneficial given that the power generated at Bent Tree is meant to benefit a region of land in Wisconsin.
“It’s helpful to think of it like a river,” explains Kaelberer. “If you pour a bucket of water into the river, you can take a bucketful out anywhere else. It might not be the same water, but it’s from the same stream.” Power generated at Bent Tree is put into the Midcontinent Independent System Operator (MISO) grid and made available to the appropriate homes and businesses.
To extend the “river” analogy, the grid also has a maximum capacity, so Bent Tree and other providers receive updates every five minutes regarding the amount of energy which the system needs, depending on how much power is being used by the system’s subscribers. If needs are low, Bent Tree might stop some of its generators temporarily to avoid overloading the grid.
The nearby high-capacity power line is an important asset because less underground cable is needed to submit power to the grid, thus creating a significant financial advantage.
Also for the truly curious, the MISO grid website shares some interesting information about the amount of power being used system wide and the types of generators which create it. The slice of its pie chart that represents wind power is still relatively small, but larger than it once was. This growth fits well into the plans of Alliant Energy, Bent Tree’s parent company.
Company spokesperson Morgan Hawk reveals that Alliant Energy is one of the nation’s largest utility owner/operators of regulated wind energy, with farms located in Iowa, Minnesota and Wisconsin. He mentions the company’s commitment to eliminate coal from its power generation system by 2040 and reach net zero carbon dioxide emissions by 2050.
In the meantime, Hawk mentions the many local benefits “generated” by wind farms, include: jobs created by construction projects, payments to local landowners, and tax revenue to area governments.
Coming back to the idea of thinking on a large scale, it becomes clear that the wind turbines at Bent Tree Wind Farm cast two kinds of “shadows,” those created by the sun and those cast across our area’s culture, finances, and future.