NABCEP Solar PV Fundamentals 3

Question 1

What is the purpose of a blocking diode in a PV string connected to a battery system?

Accepted Answer

To prevent battery current from flowing backward through the PV string at night

Answer

Blocking diodes prevent reverse current flow from the battery back through the PV modules when the array voltage is lower than battery voltage.

Question 2

An array has 4 strings of 10 modules each wired in parallel. If each module is rated at 8A Isc, what is the total array Isc?

Accepted Answer

32 A

Answer

In parallel strings, currents add: 4 strings × 8 A per string = 32 A total array Isc.

Question 3

What effect does partial shading of a single module in a series string have on overall string output without bypass diodes?

Accepted Answer

The entire string current is limited to the shaded module's reduced current

Answer

In a series string, all modules must carry the same current, so a shaded module limits the current for the entire string.

Question 4

Which of the following best describes the AM1.5 spectrum used in STC module ratings?

Accepted Answer

Sunlight passing through 1.5 times the atmosphere's thickness at a 48.2° angle

Answer

AM1.5 represents the solar spectrum when sunlight travels through 1.5 air masses (a path length 1.5× the zenith path), corresponding to a solar angle of about 48.2°.

Question 5

A PV module has a Voc of 40V at 25°C and a temperature coefficient of -0.3%/°C. What is the approximate Voc at 60°C?

Accepted Answer

35.8 V

Answer

ΔT = 35°C; voltage change = 40V × 0.003 × 35 = 4.2V decrease; Voc ≈ 40 – 4.2 = 35.8V.

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

NABCEP Solar PV Fundamentals 3