Design Principles Flashcards

The minimum number of modules per string is mainly set by which condition?

Answer: String Vmp at the highest cell temperature compared with the inverter's minimum MPPT voltage

Hot cells lower Vmp, so the string must stay above the inverter's minimum MPPT voltage at the highest expected cell temperature.

Per NEC 690.8, PV source circuit conductors are typically sized for what percentage of module Isc?

Answer: 156%

Maximum circuit current is Isc × 1.25 for irradiance, and conductor sizing adds another 1.25 for continuous duty, giving 156%.

For a fixed array in the Northern Hemisphere, which azimuth generally gives the most annual energy?

Answer: True south (180°)

Facing true south maximizes annual irradiance capture in the Northern Hemisphere.

At a site with 12° east magnetic declination, a compass reads 180°. What is the approximate true azimuth?

Answer: 192°

With east declination, true bearing equals magnetic bearing plus declination: 180° + 12° = 192°.

Which site factor most directly increases the energy gain of bifacial modules?

Answer: Higher ground albedo, such as white gravel or snow

Bifacial rear-side gain depends mostly on how much light the ground reflects onto the back of the module.

A typical horizontal single-axis tracker in the US works in which way?

Answer: Rotates on a north-south axis to follow the sun from east to west

Horizontal single-axis trackers have a north-south torque tube and tilt east to west through the day.

Which voltage drop target is a common design guideline for PV DC circuits?

Answer: 2% to 3% or less

Designers usually keep DC voltage drop at about 2–3% or less to limit energy loss, even though the NEC does not mandate a value.