NABCEP Module Technology 3 — Questions and Answers
Question 1: How does increasing the number of cells connected in series within a PV module affect its electrical output?
- Increases short-circuit current proportionally while voltage stays constant
- Increases open-circuit voltage proportionally while current stays approximately constant (Correct answer)
- Increases both current and voltage equally
- Decreases internal resistance without changing output voltage or current
Correct answer: Increases open-circuit voltage proportionally while current stays approximately constant
Series-connected cells add their voltages while sharing the same current, so more cells in series raises the module's Voc and Vmpp without significantly changing Isc.
Question 2: What is the function of the encapsulant layer (typically EVA) in a PV module construction?
- Provides electrical insulation between the junction box and the frame
- Optically couples the glass to the cells and protects cells from mechanical stress and moisture (Correct answer)
- Acts as the primary structural load-bearing component of the module
- Reflects infrared radiation to reduce cell operating temperature
Correct answer: Optically couples the glass to the cells and protects cells from mechanical stress and moisture
EVA (ethylene vinyl acetate) encapsulant bonds the glass, cells, and backsheet together, optically coupling light into the cells while protecting them from humidity, oxygen, and mechanical damage.
Question 3: A monocrystalline silicon cell is typically identified by which visual characteristic?
- Blue or gray speckled appearance from grain boundaries
- Uniform dark black or dark blue color with chamfered corners (Correct answer)
- Irregular brown coloration with visible crystal boundaries
- Red or orange tint from cadmium compounds
Correct answer: Uniform dark black or dark blue color with chamfered corners
Monocrystalline cells are cut from a single silicon crystal, giving them a uniform dark color and characteristic octagonal shape with cut corners to reduce silicon waste.
Question 4: Under NOCT (Nominal Operating Cell Temperature) conditions, what is the standard ambient temperature and irradiance used?
- 25°C ambient, 1000 W/m²
- 20°C ambient, 800 W/m² (Correct answer)
- 25°C ambient, 800 W/m²
- 20°C ambient, 1000 W/m²
Correct answer: 20°C ambient, 800 W/m²
NOCT is measured at 20°C ambient temperature, 800 W/m² irradiance, and 1 m/s wind speed with the module in open-rack mounting — conditions more representative of real-world operation.
Question 5: What does the fill factor (FF) of a PV module represent?
- The fraction of module area covered by active solar cells vs. total module area
- The ratio of actual maximum power to the theoretical product of Voc and Isc (Correct answer)
- The percentage of incident light converted to electricity at STC
- The ratio of module efficiency at NOCT versus STC conditions
Correct answer: The ratio of actual maximum power to the theoretical product of Voc and Isc
Fill factor = Pmpp / (Voc × Isc), representing how 'square' the I-V curve is; higher FF (closer to 1.0) indicates lower series resistance and better cell quality.
Question 6: Which type of PV module technology typically has the lowest temperature coefficient for power output?
- Monocrystalline silicon
- Multicrystalline silicon
- Amorphous silicon thin-film (Correct answer)
- PERC monocrystalline
Correct answer: Amorphous silicon thin-film
Amorphous silicon thin-film modules have a lower (less negative) temperature coefficient (~-0.20%/°C) compared to crystalline silicon (~-0.35 to -0.45%/°C), giving them a relative performance advantage in hot climates.
Question 7: What is 'soiling loss' in the context of PV module performance, and how is it typically quantified?
- Electrical degradation from contaminated soldering flux during manufacturing, measured in mΩ
- Power loss from dirt, dust, or debris on the module surface, expressed as a percentage of incident irradiance blocked (Correct answer)
- Corrosion of the aluminum frame reducing structural integrity, rated in years to failure
- Discoloration of the encapsulant reducing optical transmission, measured in transmittance percentage
Correct answer: Power loss from dirt, dust, or debris on the module surface, expressed as a percentage of incident irradiance blocked
Soiling loss is the reduction in power output caused by particulate matter on the glass surface blocking irradiance, typically expressed as a percentage loss per day or year depending on climate and tilt.
NABCEP Module Technology 3
How does increasing the number of cells connected in series within a PV module affect its electrical output?