University of Missouri – Kansas CityRyan Walsh - Advanced Geographic Information Science

Ward County, North Dakota and Potential wind turbine sites

An analysis of the most appropriate sites in western Ward County, North Dakota for wind turbine construction.

PurposeIn a previous study, the best possible locations for the construction of new wind turbines in North Dakota were determined. Areas of the state with the best wind power classes (WPC 5 and 6) have the highest average wind speeds. Figure 1, shown below, is a map displaying the location of these wind power classes. The best possible locations for constructing new wind turbines are within the highest power wind capacity areas. The orange diamonds represent existing wind turbines. Undeveloped prime areas appear to be in the south-central, north-central, and north-western parts of the state.

The area that appears most ideal for a utility-scale find farm is the western part of Ward County, near the city of Minot. Wind farms already exist south of the city, so Ward County and the city of Minot has already demonstrated the ability to accommodate and maintain the infrastructure.

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Figure 1

Study Area

Our study area of western Ward County, shown below in Figure 2, has many variables to consider. Prevailing winds, physical challenges of the terrain, and accessibility of the site area will all affect the choice of site placement. As one can see, the navy blue outline in the map below shows where the best wind can be harvested. Existing wind turbines, represented by the flame-red diamonds, are only in the southern part of Ward County. Plenty of potential development is available west of Minot, near Berthold and Des Lacs. This is the area where we need to examine the concerns and variables regarding wind turbine site selection.

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Figure 2

Prevailing Winds

In order to select the optimum location for wind turbine construction, prevailing winds have to be a major consideration. Prevailing winds are different for each geographic area and time of year. The placement of the new wind turbines greatly depends on what the prevailing winds are for the considered region.

According to NOAA’s National Climatic Data Center, prevailing winds for the Minot Air Force Base come from the northwest throughout most of the year with an average speed of 9 MPH and a peak gust 85 MPH.1 The spring brings prevailing winds more from the north and the summer has more westerly winds. With this information, it can be determined that the placement of the turbines needs to be able to maximize the capture of northwesterly winds.

Water Features

There are various streams, lakes, and ponds in the study area. The proposed sites for construction will need to avoid any major water features. Avoidance of all water features is an option, but the drainage of the smaller bodies of water could also be considered.

Accessibility of Wind Turbine Sites

The western part of Ward County, just west of the city of Minot, is chosen as the general area for site considerations. A display of the population centers around the potential wind turbines will be needed. In addition, transportation to the wind turbine site area from Minot and other population centers must be available. A major highway connecting cities and towns within the region would be ideal.

Data and Metadata (Datums and Projections in Parenthesis)Datasets used in the initial study that are also being used in this study include the following:

1) North American Wind Turbines – (USGS) United States Geological Survey (NAD 1983 Datum and Albers Projection)

Data is used for the “Existing Wind Turbines” point feature class.

2) North Dakota and South Dakota Wind – (NREL) National Renewable Energy Laboratory (WGS 1984)

Data is used for the “Highest Power Wind Capacity” polygon feature class.

3) North Dakota Counties – ESRI Online (NAD_1983_StatePlane_North_Dakota_South_FIPS_3302_Feet)

Data is used for the “County Borders” polygon feature class.

1 NOAA. National Climatic Data Center. “Climatic Wind Data for the United States.” (1996) http://www.ncdc.noaa.gov/sites/default/files/attachments/wind1996.pdf

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New datasets used to conduct the following include all those listed below:

1) Elevation Raster – a Digital Elevation Model downloaded from the National Elevation Dataset via the United States Geological Survey (NAD 1983)

2) Elevation Contour – a shapefile downloaded from the National Elevation Dataset via the United States Geological Survey (GCS_North_American_1983)

3) Proposed Wind Turbines – a new feature class created from points added during an edit session (NAD_1983_StatePlane_North_Dakota_South_FIPS_3302_Feet)

The datasets below were obtained from the North Dakota government GIS Hub website.

4) Rivers and Streams – derived from a lines feature class within a hydrography feature dataset (GCS_North_American_1983)

5) Water Bodies – derived from a polygon feature class within a hydrography feature dataset ((GCS_North_American_1983)

6) County Roads – derived from a line shapefile (NAD_1983_StatePlane_North_Dakota_South_FIPS_3302_Feet)

7) State and Federal Roads – derived from a line shapefile (NAD_1983_StatePlane_North_Dakota_South_FIPS_3302_Feet

8) Cities – derived from a point shapefile (NAD_1983_StatePlane_North_Dakota_South_FIPS_3302_Feet)

All other data layers not listed were created using geoprocessing processes that were derived from the datasets listed.

Methods and Procedures (* Denotes Advanced GIS Method)Building a geodatabase*

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Figure 3

The site analysis needed a well-organized geodatabase to properly store all imported and geoprocessed data. I created a file geodatabase named “North Dakota Wind Turbine Site Analysis.gdb” to be the default geodatabase for the project. The “Hydrography” and “Transportation” feature datasets were created to store their respective related feature classes. Most of the data are standalone rasters and feature classes. The geodatabase can be seen in Figure 3 above.

Study Area and Extent Area

After data was collected and input into ArcMap, the study area needed to be represented. The study area map, shown previously in Figure 2, required 2 data frames. For those familiar with the past study I have done (“North Dakota Wind Capacity and Potential Wind Farm Sites”), it is important to show where the potential site construction is to be located within the whole of North Dakota.

Hillshade Raster*

In order to better visualize the elevation layer, it was helpful to create a hillshade layer. Using the Hillshade geoprocessing tool in the Spatial Analyst toolbox, I computed a hillshade raster with an illumination set at a 315 degree azimuth and a 45 degree angle of altitude.

Shaded Relief Effect

After computing the hillshade layer, the elevation layer was draped over it. The elevation surface was given a multi-colored symbology with a transparency of 40 percent. This created a shaded relief effect where both the elevation and landform shapes could be displayed simultaneously. The aesthetically-pleasing display adds valuable depth to the map.

Aspect Raster*

We know that the prevailing winds for Minot, North Dakota and the surrounding area are generally northwesterly (sometimes more northerly or westerly at certain times of the year). Therefore, it is preferred that the wind turbines be on northwest facing slopes in order to capture the prevailing wind. An aspect raster was generated from the elevation raster to show the direction that the hillsides face. An area was identified about 24 miles west/northwest of Minot and 4 miles southwest of Berthold. Many northwest facing hillslopes are found here along a crest represented in pink.

In order to better visually capture this area. A rectangle was drawn around the perimeter of the area bordered by the county roads. This can be seen in the screenshot Figure 4 on the next page (the county roads layer has been turned off in the image).

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Feature Class of Wind Turbine Proposals

After determining the best area to place new wind turbines, a new point feature class named “Proposed Wind Turbines” was created in the default geodatabase. Using an edit session, new point features (white circles with dots) of the feature class were placed on the pink areas inside the rectangle. These can be seen in Figure 4 above. The points represent where the most suitable places for wind turbine construction are located.

Kernel Density for Population of Cities*

With the proposed wind turbine sites determined, a population density raster was generated to confirm an available population in nearby cities. The Kernel Density tool was used to determine the point density of cities in western Ward County, weighted by their 2010 population census data. A 5 mile (26,400 feet) radius was used around the points and the extent was limited to the elevation layer area. The quantile symbology method was chosen to represent the population. Otherwise, cities and towns other than Minot would have been poorly represented in the display.

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Figure 4

Maps and Results

In Figure 5 above, the elevation of the study area is shown. We can see that the elevation tends to increase the farther west one travels, until you leave the area of highest wind capacity. Clearly, there is a relationship between the best areas to capture wind and the elevation of the landscape. The potential wind turbine sites will be placed somewhere above 700 feet and within the outline for “Highest Power Wind Capacity.”

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Figure 5

The area in Figure 6, shown above, shows the slope aspect for the terrain. Areas of red (north), pink (northwest), and royal blue (west) represent the best hill sides for capturing prevailing winds. However, the pink areas are ideal. The rectangle drawn above is around an area identified as having many of the northwest facing hillsides. It is an area approximately 4 miles southwest of Berthold. The width of the rectangle is about 1 mile and the length (north to south) is about 2 miles.

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Figure 6

Here, in Figure 7, you can see 51 white circles with black dots representing placement for potential wind turbines. They are all located on northwest facing hillslopes. Although, there are plenty of west facing and north facing slopes to be considered if necessary.

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Figure 7

The above picture, Figure 8, is a screenshot of the proposed site area, but without an elevation or aspect raster behind it. Instead there are contours used to give some idea of the terrain. Lakes, ponds, and streams are displayed in this image as well. With these features in place, we can confirm that the proposed sites do not sit on any bodies of water and appear to follow the hillsides as well.

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Figure 8

The final map, Figure 9, pans our view out to see most of western Ward County. This time a population density raster is display with county, state, and federal roadways layered on top. The quantiles symbology of the kernel density raster allows each population center (no matter how small) to have representation on the screen. Minot is easily the only major population center here, but Burlington, Surrey, and even Berthold are significant enough to warrant darker colors.

The wind turbine site area is very close to US Highway 2, which Berthold, Burlington, Minot, and Surrey would all use to access the site area. The site area is border by 324th St. to the east, 353rd St. to the west, 62nd Ave to the north, and 30th Ave to the south. All are currently gravel roads.

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Figure 9

Conclusion of Results

After reviewing the produced maps and data associated with them, it appears that the potential wind turbine site area is an ideal location for constructing new turbines. First, the turbines fall within the high wind power class area and can catch prevailing winds at high elevations from the northwest. There are west and north facing hill slopes to also consider for additional turbines. Second, no bodies of water conflict with the development sites, and our previous study already ruled out the site location having an impact on protected areas. Finally, the wind turbine site is accessible. The nearby population centers, and the major US highway connecting them to the site area, allow for a nearby workforce to construct and/or maintain the wind farm.

If Ward County considers adding additional wind farms, then this site area should be strongly considered for wind farm development.

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