Hoosac Wind Turbine Sound Monitoring

by Chris Kapsambelis

Power/Noise discrepancy

This graph shows blue diamonds highlighting values from the Hoosac noise testing report (plotted from the table on the left below) to represent the power output during testing. The  red boxes come from the published power curve of the GE 1.5 sle wind turbine. The expected power output related to wind speed is shown in the table on the right below.
In comparing the recorded power output to the published power curve data, it is clear that the wind turbines were not operating normally. The power output was as much as 33% less than normal which would mean that the sound power level was also substantially reduced.

This casts a shadow on the integrity of the sound study and needs a plausible explanation.

Attention is called to the data points inside the box between 8 and 12 meters/second. This is the range where the noise level is most likely to be in violation. At wind speeds less than 8 m/s the noise level is too low to overcome the 10 dB(A) above ambient limit. And above 12 m/s the sound power from the wind turbine flattens out while the wind is creating excessive ambient noise.

The study contains weather data sets for 13 monitoring periods.  Each data set contains wind speed data and average turbine output power per turbine.

These data* were copied into a table used to plot power output as a function of wind speed. The field labels:

• “BS/AS” Refer to the original fields “WT + Background  Before Shutdown, WT + Background  After Start.”
• The field “WD” refers to “Met Tower 50 meter Wind Direction (degrees).”
• The field “WS” refers to “Met Tower 62 meter wind speed (m/s).”
• The field “WT Power” refers to “Average Turbine Output (kW per turbine). “  
• The field “Date” is taken from the title of each Weather Data table.

*The data is contained in tables 8. 10, 12, 15, 17, 20, 22, 24, 26, 29, 31, 33, and 36 titled “Weather Data.”