Understanding Turbines - Honing on Renewable Nature

Turbine in the Wind Teacher Guide

Objective: To understand the effect wind plays on the structural response of wind turbines, two important questions will be explored: 1) How does wind vary with change in height, 2) How does wind speed effect turbine blades (rotors)?

Background: Data has been collected on a Micron 65/13M wind turbine by Sandia National Laboratories in Bushland, Texas. The data will be used to determine the structural response of the turbine under measured wind speeds (wind loads).

Mission: Your team of engineers (wind and structural specialists) has been hired by Sandia Laboratories to analyze wind data measured in Bushland, Texas. Sandia has requested graphs of time versus wind speed and graphs of time versus flap and edge bending moments of the rotors. Each team is assigned a different set of data to analyze.

The files are saved under Data: Students on the WE-Tex website. They can be downloaded or used directly from the site. Open file and review the data with your students.

Group 01: STR - 120 Seconds (Wind Speed at Top/Middle/Bottom)

Group 02: 120 - 240 Seconds (Wind Speed at Top/Middle/Bottom)

Group 06: STR - 120 Seconds (Edge Bending Moment)

Group 07: 120 - 240 Seconds (Edge Bending Moment)

Group 08: 240- 360 Seconds (Edge Bending Moment)

Group 09: 360 - 480 Seconds (Edge Bending Moment) Group 10: 480 - 600 Seconds (Edge Bending Moment)

Group 11: STR - 120 Seconds (Flap Bending Moment)

Group 12: 120 - 240 Seconds (Flap Bending Moment)

Procedures:

Continue to use the file as an example for the students. If your students have limited experience with EXCEL you may want to guide them through the procedures one step at a time.

To create a graph of the data, follow the procedures below.

1) Open the file designated for your group (i.e. Group One). 2) Find the mean (average), maximum value, and minimum value for each column. Click in the first unknown box (mean???). Type =average(E17:E137), or type =average( - highlight the desired column with the mouse - ). Follow the same procedure for column F and column G – for a quicker solution Edit: Copy cell E-14 and paste into both cell F- 14 and G-14. To find the maximum value and minimum value, follow the same procedure as for average using the following equation- maximum value =max(E17:E137) and minimum value =min(E17:E137)]. 3) Highlight the cells D to G from row 17 to row 137. 4) From the top toolbar, click Insert: Chart. 5) Chart Type: Scatter. 6) Chart Sub-Type: Scatter with data points connected by smoothed lines without markers. 7) Click Next. 8) Click Next. 9) In Chart title, type: Time versus Your Group Data [wind speed, edge bending, or flap bending] 10) In Value (X) axis, type: Time (seconds) 11) In Value (Y) axis, type: Your Group Data [wind speed (m/s), edge bending (kN-m), or flap bending (kN-m)] 12) Click Finish. 13) Right click the new chart and go to Source Data. 14) Click the tab at the top for Series. 15) Name the series: Top, Middle, and Bottom. 16) Click Ok. 17) The graph is complete. 18) Print just the chart by selecting it, then go to File-Print. 19) Write the names of your group members on the chart and turn in.

(You could also have them save the charts to a read-only folder in your name.)

After collecting the charts from all groups, use a transparency or project the four charts from the data key in the Teachers section of the WE-Tex site. The first chart illustrates the difference in wind speed due to height (top, middle, and bottom of the rotor’s circular path). You should point out that the line representing the top is often the highest. Ask students why they think this is true. A normal wind profile shows an increase in wind speed with an increase in height.

The second chart shows edge bending of the rotors from the data collected by all groups. Edge bending is an up and down movement (perpendicular to the ground) caused by wind loads. Edge bending can cause fatigue, which can lead to a rotor (blade) breaking.

The third chart shows flap bending from data collected by all groups. Flap bending is a sideways motion (parallel to the wind – like a flag in the breeze) caused by wind loads. Flap bending can also cause fatigue (like bending a paperclip until it breaks), which can lead to a rotor breaking.

The fourth chart is a histogram of the wind data collected by all groups. The histogram is based on the number of observations in each wind speed category. It again shows that the peak (top) of the rotor’s circular path often encounters the highest wind speed.