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PV System Design Principles Flashcards

7 cards from real NABCEP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 PV System Design Principles flashcards as text

  1. In a battery-based PV system, the depth of discharge (DOD) limit for lead-acid batteries is typically set at 50% to:

    Answer: Extend battery cycle life and prevent sulfation damage

    Limiting DOD to 50% significantly extends lead-acid battery cycle life by reducing sulfation and plate degradation.

  2. Which performance ratio (PR) range is considered typical for a well-designed, operational grid-tied PV system?

    Answer: 0.75 to 0.85

    A performance ratio of 0.75–0.85 accounts for typical real-world losses including temperature, wiring, inverter efficiency, and soiling.

  3. The 'clipping' loss in a PV system occurs when:

    Answer: The array's DC output exceeds the inverter's maximum AC output capacity

    Clipping happens when irradiance is high enough that the array produces more DC power than the inverter can convert, causing the inverter to limit output.

  4. The DC-to-AC ratio (also called inverter loading ratio or ILR) of 1.2 for a PV system means:

    Answer: The DC nameplate capacity is 1.2 times the inverter's AC output rating

    An ILR of 1.2 means the array's STC DC capacity is oversized by 20% relative to the inverter's rated AC output, which is common to optimize annual energy yield.

  5. An azimuth angle of 180° for a fixed-tilt PV array in the northern hemisphere indicates the array faces:

    Answer: Due south

    In the northern hemisphere, true south (180° azimuth) maximizes annual solar irradiance for a fixed-tilt array.

  6. Which type of mounting system is most appropriate for flat commercial rooftops to minimize roof penetrations?

    Answer: Ballasted racking systems

    Ballasted racking uses weight (concrete blocks or the racking weight itself) to hold arrays in place without penetrating the roofing membrane.

  7. When using PVWatts or similar simulation tools, the 'system losses' input of approximately 14% typically accounts for:

    Answer: Wiring, soiling, shading, mismatch, inverter, and other real-world efficiency losses

    The default ~14% system losses in PVWatts aggregates multiple derate factors including soiling, wiring resistance, mismatch, shading, inverter efficiency, and availability.