Materials & Methods
This section will discuss the equipment and methodology employed to assess the validity of post-mining wind power. Main topics include site selection, data collection, data processing, and financial analysis. One of the principle stipulations to ensure the validity of the feasibility study was to utilize industry-standard practices in all phases of analysis. The publications referenced to accomplish this goal are discussed in detail in the Literature Review section    .
The first phase of the wind assessment campaign was to select reclaimed or partially-reclaimed mine properties to evaluate. In the interest of only dealing with one set of state regulations, it was decided to limit the study to West Virginia. Candidate ANR sites were identified and their property boundaries entered into a Geographic Information Systems (GIS) map file using the ArcInfo GIS software suite. Wind potential and power transmission grid data were then obtained from NREL  and combined with the reclaimed property outlines provided by ANR engineering staff. In this way, all potential monitoring sites could be surveyed simultaneously at a basic level.
The publically-available wind potential data used in the initial GIS analysis is composed mostly of interpolations between scattered monitoring stations. A more sophisticated dataset encompassing the areas under investigation was purchased from AWS TrueWind in order to improve the quality of the study. These data are shown overlaying (and masking) the public data in all figures in this section.
The DOE classifies wind potential from Class 1-7, with 1 being poor and 7 being exceptional. These classes are based on the anticipated power density (measured in W/m2 – see Equation 1) of an area, which is a function of wind speed and consistency. Transmission line locations are also very important due to the large costs associated with building new high voltage lines; many locations with tremendous wind conditions are not economic because of their distance from transmission infrastructure. An initial query to ANR staff indicated that 21 properties would be available for consideration for monitoring. These are shown Figure 3.1 along with wind potential and power transmission infrastructure.
Many of the sites shown in Figure 3.1 were determined to be unsuitable for monitoring due to insufficient areas of reclaimed land or significant distance from desirable wind conditions. The 24 list of candidate sites was shortened to six properties: Seven Pines, Lost Flats, Pax South, White Flame #9, White Flame #10, and Pounding Mill. Their property outlines are shown, along with wind conditions and transmission infrastructure, in Figure 3.2.
Figure 3.3, Figure 3.4, Figure 3.5, and Figure 3.6 show zoomed-in views of all six properties. In these maps, wind conditions and property boundaries overlay a hillshade of local topography. Note that favorable wind conditions are located almost exclusively along ridgelines.
It should be stressed again that these data are the result of interpolation and numerical modeling based on scattered monitoring stations – not on comprehensive surveys. As such, areas shown as Class 2 may have sections of Class 3 or 4 (or vice-versa). The true conditions of a site cannot be known definitively until they have been measured directly. However, this general data can adequately serve as the basis for selecting the sites to be monitored.
All six candidate sites were visited in person and evaluated subjectively. Based on these considerations, site wind potential, and proximity to transmission infrastructure, the Lost Flats, Pax South, and White Flame #10 sites were chosen for monitoring. These locations are pictured in Figure 3.7, Figure 3.8, and Figure 3.9, respectively.
Data Collection – Wind Assessment Campaign
The purpose of the wind assessment campaign was to empirically collect data characterizing wind conditions at each of the three selected monitoring locations. This section will explain the details of the monitoring equipment selected and how it performs its intended functions.
Three options exist for data collection: met-towers, SODAR, and LIDAR (see Literature Review for additional details). Met-towers were selected due to their proven success rate and the industry-wide acceptance of met-tower data.
Industry-standard practices call for the measurement of three properties at any given monitoring location: wind speed, wind direction, and air temperature. Wind speed data are utilized for predicting turbine electrical output, directional data are used in siting and orienting turbines, and temperature data are used in the calculation of air density. All quantities are to be sampled at 2.0 Hz and logged at time-stamped 10-minute intervals which include average, maximum, minimum, and standard deviation values. Except for wind direction, the average value is defined as the mean for all samples. For wind direction, the average is a unit vector. These data must be collected for a period of at least 12 months in order to properly quantify the seasonal variations in wind conditions, though additional time is preferable.
After a detailed review of multiple monitoring solutions, a preferred equipment system was identified in the NRG Systems 60m XHD. The package contains a 60m (197ft) thin-wall steel tube tilt-up tower, six pre-calibrated cup anemometers, two directional vane sensors, temperature sensor, barometric pressure sensor, data logger, solar panels, satellite uplink (for data transmission), and all assembly tools and instructions. In addition to precisely following industry-standard methodology, the system is self-powered and able to transmit data under any conditions. Two anemometers are present at each monitoring height of 60, 50, and 38m; directional sensors are located at 60 and 50m; and the temperature and pressure sensors are placed at the base of the tower at a height of 2m.
Three NRG 60m XHD units were purchased and assembled at the Lost Flats, Pax South, and White Flame #10 locations. The towers were assembled on the ground and then tilted up using a hydraulic winch and gin pole. The tensions in a series of guy wires were adjusted during the lift and are used to stabilize the structure after it reaches a vertical orientation. The White Flame installation was completed on April 30th, 2010; the Pax South installation was completed on August 12th, 2010; and the Lost Flats installation was completed on August 20th, 2010. Figure 3.10, Figure 3.11, and Figure 3.12 depict the White Flame #10 tower being lifted into its final position.
Wind Condition Quantification
The data gathered from the three monitoring locations were processed using the Professional Edition of the Windographer software, developed by Mistaya Engineering. Several quantities must be calculated from the raw data in order to conduct a site feasibility study. Wind speed and wind direction data are typically organized into bins and plotted as histograms. The Weibull probability density is then calculated from these data, given by the equation.
2. Background & Literature Review
2.1. Coal Mining in Appalachia
2.2. Sustainability, Communities, and Mining
2.3. Mine Reclamation
2.4. Wind Energy
2.5. Background & Literature Review Summary
3. Materials & Methods
3.1. Site Selection
3.2. Data Collection – Wind Assessment Campaign .
3.3. Data Processing
3.4. Financial Analysis Methodology
4.1. White Flame #10
4.2. Pax South
4.3. Lost Flats
5. Analysis & Discussion
5.1. Analysis Assumptions
5.2. Case Study: White Flame #10
5.3. Case Study: Pax South
5.4. Case Study: Lost Flats
5.5. Commercial-Scale Wind Development Discussion
6. Conclusions & Recommendations
6.1. Future work
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A Feasibility Analysis of Wind Power as an Alternative Post-mining Land Use in Surface Coal Mines in West Virginia