VA Alternative Energy System Contracting Exam Questions
and Answers| Latest Update| Pass Guaranteed
Q1. What is the primary effect that allows a photovoltaic (PV) cell to generate
electricity from sunlight?
A) The Seebeck effect
B) The photovoltaic effect
C) The piezoelectric effect
D) The Hall effect
Answer: B) The photovoltaic effect
Rationale: PV cells convert light energy directly into electrical energy through the
photovoltaic effect, in which photons striking a semiconductor (typically silicon)
knock electrons loose, creating a flow of current across a p-n junction.
Q2. Which material is most commonly used as the semiconductor in
conventional PV cells?
A) Copper
B) Silicon
C) Aluminum
D) Gallium
Answer: B) Silicon
Rationale: Silicon, doped to create p-type and n-type layers, is the dominant
semiconductor used in commercial PV cells due to its abundance, stability, and
well-understood manufacturing processes.
Q3. A PV module's rated power output (in watts) is measured under what
standardized condition?
A) Nominal Operating Cell Temperature (NOCT)
B) Standard Test Conditions (STC)
C) Peak Sun Hours (PSH)
D) Real Operating Conditions (ROC)
Answer: B) Standard Test Conditions (STC)
,Rationale: STC specifies 1000 W/m² irradiance, 25°C cell temperature, and an air
mass of 1.5, providing a consistent baseline so modules from different
manufacturers can be compared.
Q4. As PV module temperature increases above 25°C, what generally happens
to the module's voltage output?
A) Voltage increases
B) Voltage decreases
C) Voltage stays constant
D) Voltage becomes unpredictable
Answer: B) Voltage decreases
Rationale: Crystalline silicon modules have a negative temperature coefficient for
voltage; open-circuit voltage drops as cell temperature rises, which is why
designers must calculate low-temperature voltage limits for string sizing.
Q5. When sizing a PV string's maximum voltage for cold-weather conditions,
which value should the installer use?
A) The average annual low temperature
B) The record low temperature for the site per ASHRAE/local data
C) The manufacturer's STC rating only
D) The NOCT rating
Answer: B) The record low temperature for the site per ASHRAE/local data
Rationale: NEC 690.7 requires that maximum system voltage be calculated using
the lowest expected ambient temperature for the site, since Voc rises in cold
weather and could exceed inverter or conductor voltage ratings.
Q6. What does 'peak sun hours' represent when calculating PV array output?
A) The number of daylight hours in a day
B) The equivalent number of hours per day at 1000 W/m² irradiance
C) The hours between sunrise and sunset
D) The hours of direct sunlight only, excluding diffuse light
Answer: B) The equivalent number of hours per day at 1000 W/m² irradiance
Rationale: Peak sun hours condense the day's total solar irradiation into an
equivalent number of hours at the standard 1000 W/m² intensity, allowing
,simplified energy production estimates (kWh = array kW x peak sun hours x
efficiency factors).
Q7. In Virginia, what is the general orientation and tilt recommendation for
maximizing annual solar PV production?
A) North-facing at a steep tilt
B) South-facing at a tilt roughly equal to the site's latitude
C) East-facing at a flat tilt
D) West-facing at a 45-degree tilt
Answer: B) South-facing at a tilt roughly equal to the site's latitude
Rationale: For most of the continental U.S., including Virginia (roughly 37-39
degrees N latitude), true south orientation with tilt near the site latitude
maximizes annual energy capture, though production-weighted tilts are often
flatter.
Q8. What is the primary purpose of a maximum power point tracker (MPPT) in a
PV system?
A) To ground the array for lightning protection
B) To continuously adjust the electrical operating point so the array delivers its
maximum available power
C) To disconnect the array during grid outages
D) To convert AC to DC
Answer: B) To continuously adjust the electrical operating point so the array
delivers its maximum available power
Rationale: An MPPT algorithm continuously searches for the voltage/current
combination on the array's I-V curve that yields maximum power output,
compensating for changes in irradiance and temperature.
Q9. Which of the following best describes a string inverter configuration?
A) Each module has its own dedicated inverter
B) Multiple modules are wired in series into a single inverter input
C) The inverter is mounted on the roof beside each panel
D) Inverters are only used for battery charging
Answer: B) Multiple modules are wired in series into a single inverter input
, Rationale: A string inverter aggregates a series string (or several strings) of
modules into one central inverter, as opposed to microinverters, which convert
power at each individual module.
Q10. What is a key advantage of microinverters compared to a central string
inverter?
A) Lower initial equipment cost
B) Module-level shading has less impact on overall system output
C) They eliminate the need for AC disconnects
D) They operate only on DC current
Answer: B) Module-level shading has less impact on overall system output
Rationale: Because each microinverter operates independently at the module level,
shading or a fault on one panel does not drag down the performance of the entire
string, unlike a series-string design.
Q11. What is the function of bypass diodes within a PV module?
A) To increase the module's voltage output
B) To provide a path for current around a shaded or faulty cell to prevent hot-
spot damage
C) To convert DC to AC within the module
D) To ground the module frame
Answer: B) To provide a path for current around a shaded or faulty cell to
prevent hot-spot damage
Rationale: Bypass diodes allow current to flow around a shaded or
underperforming cell string, preventing that cell from being forced into reverse
bias and overheating (hot-spotting), which could damage the module.
Q12. A blocking diode in a PV source circuit primarily serves to:
A) Increase array wattage
B) Prevent reverse current flow from the battery or other strings back into the
array
C) Step down system voltage
D) Filter AC ripple
Answer: B) Prevent reverse current flow from the battery or other strings back
into the array
and Answers| Latest Update| Pass Guaranteed
Q1. What is the primary effect that allows a photovoltaic (PV) cell to generate
electricity from sunlight?
A) The Seebeck effect
B) The photovoltaic effect
C) The piezoelectric effect
D) The Hall effect
Answer: B) The photovoltaic effect
Rationale: PV cells convert light energy directly into electrical energy through the
photovoltaic effect, in which photons striking a semiconductor (typically silicon)
knock electrons loose, creating a flow of current across a p-n junction.
Q2. Which material is most commonly used as the semiconductor in
conventional PV cells?
A) Copper
B) Silicon
C) Aluminum
D) Gallium
Answer: B) Silicon
Rationale: Silicon, doped to create p-type and n-type layers, is the dominant
semiconductor used in commercial PV cells due to its abundance, stability, and
well-understood manufacturing processes.
Q3. A PV module's rated power output (in watts) is measured under what
standardized condition?
A) Nominal Operating Cell Temperature (NOCT)
B) Standard Test Conditions (STC)
C) Peak Sun Hours (PSH)
D) Real Operating Conditions (ROC)
Answer: B) Standard Test Conditions (STC)
,Rationale: STC specifies 1000 W/m² irradiance, 25°C cell temperature, and an air
mass of 1.5, providing a consistent baseline so modules from different
manufacturers can be compared.
Q4. As PV module temperature increases above 25°C, what generally happens
to the module's voltage output?
A) Voltage increases
B) Voltage decreases
C) Voltage stays constant
D) Voltage becomes unpredictable
Answer: B) Voltage decreases
Rationale: Crystalline silicon modules have a negative temperature coefficient for
voltage; open-circuit voltage drops as cell temperature rises, which is why
designers must calculate low-temperature voltage limits for string sizing.
Q5. When sizing a PV string's maximum voltage for cold-weather conditions,
which value should the installer use?
A) The average annual low temperature
B) The record low temperature for the site per ASHRAE/local data
C) The manufacturer's STC rating only
D) The NOCT rating
Answer: B) The record low temperature for the site per ASHRAE/local data
Rationale: NEC 690.7 requires that maximum system voltage be calculated using
the lowest expected ambient temperature for the site, since Voc rises in cold
weather and could exceed inverter or conductor voltage ratings.
Q6. What does 'peak sun hours' represent when calculating PV array output?
A) The number of daylight hours in a day
B) The equivalent number of hours per day at 1000 W/m² irradiance
C) The hours between sunrise and sunset
D) The hours of direct sunlight only, excluding diffuse light
Answer: B) The equivalent number of hours per day at 1000 W/m² irradiance
Rationale: Peak sun hours condense the day's total solar irradiation into an
equivalent number of hours at the standard 1000 W/m² intensity, allowing
,simplified energy production estimates (kWh = array kW x peak sun hours x
efficiency factors).
Q7. In Virginia, what is the general orientation and tilt recommendation for
maximizing annual solar PV production?
A) North-facing at a steep tilt
B) South-facing at a tilt roughly equal to the site's latitude
C) East-facing at a flat tilt
D) West-facing at a 45-degree tilt
Answer: B) South-facing at a tilt roughly equal to the site's latitude
Rationale: For most of the continental U.S., including Virginia (roughly 37-39
degrees N latitude), true south orientation with tilt near the site latitude
maximizes annual energy capture, though production-weighted tilts are often
flatter.
Q8. What is the primary purpose of a maximum power point tracker (MPPT) in a
PV system?
A) To ground the array for lightning protection
B) To continuously adjust the electrical operating point so the array delivers its
maximum available power
C) To disconnect the array during grid outages
D) To convert AC to DC
Answer: B) To continuously adjust the electrical operating point so the array
delivers its maximum available power
Rationale: An MPPT algorithm continuously searches for the voltage/current
combination on the array's I-V curve that yields maximum power output,
compensating for changes in irradiance and temperature.
Q9. Which of the following best describes a string inverter configuration?
A) Each module has its own dedicated inverter
B) Multiple modules are wired in series into a single inverter input
C) The inverter is mounted on the roof beside each panel
D) Inverters are only used for battery charging
Answer: B) Multiple modules are wired in series into a single inverter input
, Rationale: A string inverter aggregates a series string (or several strings) of
modules into one central inverter, as opposed to microinverters, which convert
power at each individual module.
Q10. What is a key advantage of microinverters compared to a central string
inverter?
A) Lower initial equipment cost
B) Module-level shading has less impact on overall system output
C) They eliminate the need for AC disconnects
D) They operate only on DC current
Answer: B) Module-level shading has less impact on overall system output
Rationale: Because each microinverter operates independently at the module level,
shading or a fault on one panel does not drag down the performance of the entire
string, unlike a series-string design.
Q11. What is the function of bypass diodes within a PV module?
A) To increase the module's voltage output
B) To provide a path for current around a shaded or faulty cell to prevent hot-
spot damage
C) To convert DC to AC within the module
D) To ground the module frame
Answer: B) To provide a path for current around a shaded or faulty cell to
prevent hot-spot damage
Rationale: Bypass diodes allow current to flow around a shaded or
underperforming cell string, preventing that cell from being forced into reverse
bias and overheating (hot-spotting), which could damage the module.
Q12. A blocking diode in a PV source circuit primarily serves to:
A) Increase array wattage
B) Prevent reverse current flow from the battery or other strings back into the
array
C) Step down system voltage
D) Filter AC ripple
Answer: B) Prevent reverse current flow from the battery or other strings back
into the array
