Solar Site and Shading Analysis Flashcards
7 cards from real NABCEP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Solar Site and Shading Analysis flashcards as text
When measuring roof azimuth with a compass for solar site assessment, which correction must be applied to obtain the true azimuth?
Answer: Apply magnetic declination correction for the geographic location
Compass measurements read magnetic azimuth; applying the local magnetic declination (adding for westerly, subtracting for easterly) converts the reading to true geographic azimuth needed for accurate solar modeling.
An array installed at 35°N latitude uses a fixed tilt equal to the site latitude (35°). To maximize annual energy production, what would be the optimal adjustment to this tilt for a summer-peak load application?
Answer: Decrease tilt to approximately 20–25° to better capture high summer sun angles
A tilt lower than site latitude (roughly latitude minus 10–15°) optimizes for summer when the sun is high; latitude tilt optimizes for annual average, not specifically summer production.
A homeowner's neighbor plants a row of fast-growing Leyland cypress trees. What site assessment tool or documentation should a solar professional recommend creating NOW, before the trees grow?
Answer: A baseline shading analysis report documenting current solar access percentages by month
Documenting current shading conditions creates a legal and technical baseline to demonstrate future shading impact if the trees grow and reduce energy production, supporting any dispute or easement claims.
In NREL's PVWatts calculator, the 'Array Type' input that accounts for single-axis tracking of the modules affects which output parameter most directly?
Answer: Annual AC energy production (kWh)
Selecting single-axis tracking in PVWatts increases the modeled annual AC energy production because the array follows the sun's east-west daily motion, capturing more irradiance throughout the day.
A ground-mount array is designed with row spacing to prevent self-shading at a specific 'design sun altitude.' Which sun altitude angle is the NABCEP standard practice for limiting inter-row shading in the continental US?
Answer: Solar altitude at 10 AM on the winter solstice (approximately the lowest critical sun angle)
NABCEP best practice uses the winter solstice at 10 AM (and 2 PM) as the design sun angle for row spacing to prevent self-shading during the period of lowest sun angles in the year.
What is the primary limitation of using only GHI (Global Horizontal Irradiance) data from a nearby weather station for a tilted array simulation?
Answer: GHI must be decomposed into direct and diffuse components and transposed to the plane of array, introducing modeling uncertainty
GHI must be mathematically decomposed into beam (DNI) and diffuse components using a model (e.g., Erbs), then transposed to the tilted plane of the array (POA), each step adding potential modeling error.
A PV system simulation in SAM (System Advisor Model) shows a 'self-shading loss' of 3.1%. This loss specifically represents:
Answer: Energy lost when one row of modules casts shadows onto an adjacent row at low sun angles
Self-shading (or inter-row shading) loss in SAM represents the reduction in energy output caused by the front rows of a multi-row ground-mount or flat-roof array casting shadows onto the rows behind them.