PV System Design Principles Flashcards

When sizing a PV array for a battery-based off-grid system, which factor most directly determines the minimum array size?

Answer: Peak sun hours at the site

Peak sun hours represent the equivalent hours of full irradiance and directly determine how much energy the array can produce per day.

A PV system is designed with modules having a temperature coefficient of Pmax of -0.35%/°C. If STC is 25°C and the cell temperature reaches 65°C, by what percentage does output power decrease?

Answer: 14%

The temperature rise is 65 - 25 = 40°C, and 40 × 0.35% = 14% power reduction.

In a grid-tied PV system, the primary function of the inverter is to:

Answer: Convert DC power from the array to AC power for the grid

The inverter converts the DC output of the PV array into AC power compatible with the utility grid.

Which NEC article primarily governs the installation of photovoltaic systems?

Answer: Article 690

NEC Article 690 specifically covers solar photovoltaic systems and their installation requirements.

The 'fill factor' (FF) of a PV module is best described as:

Answer: The ratio of maximum power to the product of Voc and Isc

Fill factor = Pmax / (Voc × Isc) and measures how close the I-V curve approaches an ideal rectangle.

When designing a string of PV modules for a string inverter, the maximum string voltage must not exceed:

Answer: The inverter's maximum DC input voltage rating

The maximum string open-circuit voltage at minimum expected temperature must stay within the inverter's rated maximum DC input voltage.

Which shading scenario causes the greatest power loss in a series-connected PV string?

Answer: One module completely shaded

In a series string, one fully shaded module becomes a current-limiting bottleneck that can reduce the entire string's output drastically.