NABCEP NABCEP Wind Energy Site Assessment 1 — Questions and Answers
Question 1: What is the primary measurement used to evaluate a site's wind energy potential?
- Average solar irradiance
- Mean annual wind speed at hub height (Correct answer)
- Prevailing temperature range
- Soil bearing capacity
Correct answer: Mean annual wind speed at hub height
Mean annual wind speed at the proposed turbine hub height is the critical parameter because wind power output scales with the cube of wind speed — small speed differences have large energy impacts.
Question 2: Why does wind power output increase with height above ground?
- Higher altitudes have less gravity
- Surface friction slows wind near the ground; wind speed increases with height due to the wind shear profile (Correct answer)
- Taller towers receive more sunlight
- Higher elevations always have lower temperatures
Correct answer: Surface friction slows wind near the ground; wind speed increases with height due to the wind shear profile
Ground surface friction creates a boundary layer that slows wind; wind speed increases with height following the wind shear power law, which is why taller towers capture significantly more energy.
Question 3: What is the Rayleigh distribution used for in wind resource assessment?
- To calculate turbine structural loads
- To statistically model the frequency distribution of wind speeds at a site when only mean wind speed data is available (Correct answer)
- To determine tower foundation depth
- To estimate solar irradiance correlation
Correct answer: To statistically model the frequency distribution of wind speeds at a site when only mean wind speed data is available
The Rayleigh distribution is a probability distribution commonly used to model wind speed frequency when only the average wind speed is known, enabling energy yield estimation.
Question 4: Which federal resource provides publicly available wind resource maps for the contiguous United States?
- USGS topographic database
- NREL Wind Prospector / Wind Resource Maps (Correct answer)
- NOAA hurricane track database
- FAA sectional aeronautical charts
Correct answer: NREL Wind Prospector / Wind Resource Maps
NREL's Wind Prospector and associated Wind Resource Maps provide publicly accessible modeled wind speed data at various heights across the US to support wind project siting.
Question 5: What does 'wind rose' data tell a site assessor?
- The electrical rose diagram of a wind turbine
- The frequency and speed distribution of wind from each compass direction at a site (Correct answer)
- The turbine rotor's swept area
- The site's solar azimuth throughout the year
Correct answer: The frequency and speed distribution of wind from each compass direction at a site
A wind rose is a graphical tool showing how often wind blows from each direction and at what speeds, helping assessors understand prevailing wind direction and optimize turbine orientation.
Question 6: What is 'turbine siting setback' and why is it required in many jurisdictions?
- A minimum distance from the turbine to the nearest electrical panel
- A minimum distance from a wind turbine to property lines, residences, or roads, required to protect against blade throw, noise, and shadow flicker (Correct answer)
- The minimum hub height required by the manufacturer
- The distance between turbines in a wind farm
Correct answer: A minimum distance from a wind turbine to property lines, residences, or roads, required to protect against blade throw, noise, and shadow flicker
Setback requirements protect neighbors from potential hazards including blade throw, noise pollution, and shadow flicker caused by rotating blades casting moving shadows on nearby buildings.
NABCEP NABCEP Wind Energy Site Assessment 1
What is the primary measurement used to evaluate a site's wind energy potential?