REP Solar Energy Systems 2 — Questions and Answers
Question 1: What is the primary function of a bypass diode in a photovoltaic module?
- Increase voltage output
- Prevent reverse current flow through shaded cells (Correct answer)
- Regulate charge to the battery
- Boost panel efficiency in low light
Correct answer: Prevent reverse current flow through shaded cells
Bypass diodes allow current to flow around shaded or damaged cells, preventing hotspot damage and maintaining power output.
Question 2: Which solar resource metric best represents the equivalent number of peak sun hours at a site?
- Global Horizontal Irradiance (GHI)
- Direct Normal Irradiance (DNI)
- Plane of Array (POA) irradiance (Correct answer)
- Diffuse Horizontal Irradiance (DHI)
Correct answer: Plane of Array (POA) irradiance
Plane of Array irradiance accounts for panel tilt and orientation and is the most directly relevant metric for estimating energy yield from a fixed PV system.
Question 3: A string of 12 PV modules each rated at 40V open-circuit voltage is connected in series. What is the maximum string open-circuit voltage?
- 40 V
- 240 V
- 480 V (Correct answer)
- 520 V
Correct answer: 480 V
Series-connected modules sum their voltages, so 12 × 40 V = 480 V open-circuit voltage.
Question 4: What does a solar inverter's 'anti-islanding' protection do?
- Prevents battery over-discharge
- Shuts down the inverter when grid power is lost (Correct answer)
- Maximizes power from the array
- Balances loads across phases
Correct answer: Shuts down the inverter when grid power is lost
Anti-islanding protection automatically disconnects the inverter from the grid during an outage to protect utility workers from unexpected energized lines.
Question 5: In a grid-tied PV system, what component is responsible for maximum power point tracking (MPPT)?
- Combiner box
- Disconnect switch
- Inverter or charge controller (Correct answer)
- Net meter
Correct answer: Inverter or charge controller
The inverter (in grid-tied systems) or charge controller (in off-grid systems) performs MPPT to continuously extract maximum power from the array.
Question 6: Which orientation yields the highest annual energy production for a fixed-tilt PV system installed in the continental United States?
- East-facing at 30°
- West-facing at 30°
- South-facing at latitude angle (Correct answer)
- North-facing at 20°
Correct answer: South-facing at latitude angle
South-facing at a tilt approximately equal to the site's latitude maximizes annual solar capture in the northern hemisphere.
Question 7: What is the purpose of a combiner box in a large PV array?
- Convert DC to AC power
- Combine multiple string circuits and provide overcurrent protection (Correct answer)
- Monitor inverter performance
- Regulate voltage to the utility grid
Correct answer: Combine multiple string circuits and provide overcurrent protection
A combiner box aggregates multiple PV strings into a single DC output and houses fuses or breakers to protect each string.
REP Solar Energy Systems 2
What is the primary function of a bypass diode in a photovoltaic module?