The basics of a wind farm by Lisa Kaczke

Items one needs to consider with a single wind turbine or a whole wind farm were outlined for the Otter Tail County Board Tuesday by Otter Tail Power consultant Bryan Morlock.

In Minnesota, the standard is to have 25 percent of the state’s electricity coming from renewable energy sources by 2025, according to Morlock.

Morlock said he was willing to share Otter Tail Power’s experience as the commissioners continue to learn about wind energy, but encouraged them to learn about wind energy from other sources as well.

Otter Tail Power has about 400 megawatts of wind turbines north of Valley City, N.D., according to Morlock. The company has received two complaints about their wind farm, one from a bed and breakfast owner regarding the view of the turbines and a second from a sled dog owner regarding the noise impact on the dogs, according to Morlock.

Wind speeds

A turbine needs a wind speed of 8 to 9 miles per hour to start. Full energy output occurs at 27 to 29 miles per hour, according to Morlock.

If wind speeds hit 55 to 57 miles per hour, the turbine’s computer system that controls the blades will automatically shut down the system and turn it out of the wind, Morlock said. The turbines can sit in dead mode in wind speeds of up to 130 miles per hour without sustaining damage, he added.

Critical to wind energy potential is wind power.

Wind power is defined as the air density times the wind speed squared. When the wind speed is increased, the power of the wind dramatically increases, Morlock said.

A tower’s height also matters — the taller the tower, the higher the wind power, Morlock said.

Variability also factors into the wind’s power. Wind that changes speeds has more power than wind that blows at a constant speed, which is why average wind speeds aren’t very critical to a wind energy project, according to Morlock.

On the larger wind turbines, the blades are so long that there can be differing wind speeds at different points of the blade, he said.

Characteristics of a turbine

How much energy a land owner will get from a wind turbine depends on the turbine.

As an example, if a 1.5 megawatt turbine outputted 100 percent of its capacity, it would be outputting 1.5 megawatts.

A small turbine outputs about 25 percent or less of its total capacity, Morlock said. The larger wind farms in southwestern and western Minnesota typically output 35 to 37 percent of their total capacity. In North Dakota, where output is considered good, wind turbines can output 42 to 45 percent of their total capacity, Morlock said.

Location decisions

Wind farms are rarely laid out in perfect formation and instead typically follow ridges and hills, Morlock said.

Morlock added that Otter Tail Power’s wind farm had 15 different layout possibilities.

When deciding on where to place the turbines, data on wind speed and direction at three different heights is saved in increments throughout the year, Morlock explained. Three years of data is preferred.

That data then goes to a meteorologist to check and review to ensure its correct, he said.

Spacing guidelines also need to be taken into consideration when deciding on the location of the turbines. Guidelines call for the space between rows to be equal to 10 rotor diameters and the space between the turbines to be four rotor diameters, Morlock said.

The spacing helps reduce turbulence problems, which Morlock called “the death of turbines.” A turbine can cause wind gusts to slam into a turbine placed behind it, he said.

Obstructive vegetation and buildings on the ground can cause turbulence twice as high as the obstruction. An obstruction, such as a tree, can cause turbulence behind it for a distance of 20 times the height of the obstruction, Morlock said.

He noted that smaller turbines sometimes are placed next to buildings because its the most convenient on the parcel of land rather than what is best for the turbine.

Also studied for turbine placement is the terrain, archeology of the area, environmental and wildlife impacts and possible airplane radar problems, Morlock said.


By the time a large wind energy project reaches the Minnesota Public Utilities Commission (PUC) for permitting, the project owners have put hundreds of thousands of dollars into the project, Morlock said.

Money has usually already been spent on wind monitoring, analysis and wind rights purchases. The interconnection request to go into the energy transmission system costs $500,000, a majority of which is requested to be paid up front, he said.

The PUC has siting jurisdiction for any projects of 5 megawatts or more. Counties can assume siting jurisdiction for wind farms between 5 and 25 megawatts if they assume responsibility and give notice to the PUC, Morlock said.

Some issues addressed in the permitting process are noise and setbacks.

Minnesota’s noise requirement is no more than 50 decibels, according to Morlock. Noise can be caused by the gear, machines and blades, and a thumping noise that can be caused by the blade passing the tower, Morlock said.

Setbacks also need to be in place in case the turbine loses a part. Setbacks also help eradicate wind rights infringement, which is when a wind farm is placed in front of another wind farm.

Hazards also need to be considered.

The most significant issue is a loss of control of the blades if the system malfunctions. The blades can get going too fast, causing them to bend and hit the turbine.

Also an issue are fires at the top of the machine and “all you can do is let the thing burn,” Morlock said.

Other issues include ice being thrown from the blade, turbine blades being thrown from the machine and oil leaks, Morlock said.

A discussion among Otter Tail County commissioners has been a possible permit requirement of a decommissioning plan for turbines no longer in use.

Morlock noted that standing unused turbines are seen more with the smaller turbines due to larger companies having millions of dollars invested into the turbines, which means they are more likely to repair them.


Construction of a wind farm can cause road damage, delivery of several semi-truck loads a day and the pouring of 35 cement trucks worth of cement.

Wind farms are typically located in rural areas where the roads aren’t designed to handle the load.

“Very significant road damage will occur,” Morlock said.

A 50 wind turbine wind farm can need around 400 truckloads or more, according to Morlock.

Multiple semi-trucks will visit the site to unload the parts a day, according to Morlock. The towers come in three segments. The blades are loaded two per truck. The nacelle comes one per truck, as does the hub.

Each tower has more than 20 tons of rebar and 350 yards of cement, Morlock said.

Three different sizes of cranes are needed to construct the turbines. The largest crane takes 25 trucks to transport it to the construction site, according to Morlock.

Contractors typically control the dust caused by the traffic and fix the roads if damaged, he said.

During construction, security firms are usually hired to patrol due to the expensive equipment and copper involved in the project.


Incentives for wind turbine owners exist at both the state and federal level.

At the federal level, people can apply for an upfront rebate from stimulus funding once their wind turbine is up and running. Another option is the production tax credit, which reduces the cost by about 33 percent, Morlock said. The problem with the tax credit is that Congress typically renews it for a year or two at a time and sometimes it expires before it’s renewed again, he pointed out.

North Dakota has the best incentives in this part of the country, according to Morlock. North Dakota’s incentive package reduces the cost by about 10 percent. A combination of federal and North Dakota incentives is the reason Morlock said he expects to see more development in North Dakota.