Photovoltaic (PV) System Design Flashcards

An off-grid home uses 6 kWh/day and needs 3 days of autonomy with a 50% maximum depth of discharge on a 48 V battery bank. What is the required capacity?

Answer: 750 Ah

6 kWh × 3 days ÷ 0.5 = 36 kWh, and 36,000 Wh ÷ 48 V = 750 Ah.

What is a key advantage of an MPPT charge controller over a PWM controller?

Answer: It can run the array at a higher voltage than the battery and convert the extra voltage into charging current

MPPT controllers step down array voltage with a DC-DC converter, recovering energy that a PWM controller would waste.

Which site factor has the biggest effect on energy gain from bifacial modules?

Answer: Ground surface albedo

The rear side collects reflected light, so a high-albedo surface such as white gravel or snow greatly increases bifacial gain.

How is ground coverage ratio (GCR) defined for a row-based array?

Answer: Collector width (slant length) divided by row pitch

GCR is the collector's width along the slope divided by the row-to-row pitch, so a higher GCR means denser rows and more inter-row shading.

Which standard is typically used in the US to determine wind and snow design loads on PV array structures?

Answer: ASCE 7

ASCE 7 sets minimum design loads, including wind and snow, which the building codes reference for PV structures.

How is a PV cell's fill factor defined?

Answer: Pmax ÷ (Voc × Isc)

Fill factor compares actual maximum power with the product of open-circuit voltage and short-circuit current, showing how 'square' the I-V curve is.

Compared with a fixed-tilt array, about how much more annual energy does a single-axis tracker typically produce at a sunny US site?

Answer: 15–25%

Single-axis trackers usually add about 15–25% annual energy by following the sun from east to west.