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UPMSP High School Solar Repair study materials
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UPMSP High School Solar Repair practice questions

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Question 1Solar Photovoltaic Fundamentals and System Types

In a grid-connected rooftop solar plant installed under net metering, what is the main function of the inverter?

  1. Track the sun so the modules stay perpendicular to the rays
  2. Protect the modules from reverse current during night hours
  3. Store excess energy chemically so it can be used after sunset
  4. Convert the DC output of the PV modules into AC synchronized with the grid supply Correct answer.

Explanation

The inverter is the power-conditioning unit of a grid-tied system: it converts module DC into utility-grade AC and synchronizes voltage, frequency and phase with the grid. Storage and sun tracking are separate functions performed by other equipment. Blocking diodes, not the inverter alone, handle reverse current at night in most small designs.

Question 2Solar Photovoltaic Fundamentals and System Types

A solar module is marked 100 W peak at standard test conditions. Which set of conditions defines that rating?

  1. Irradiance 800 W/m2, cell temperature 40 C, air mass 1.0 spectrum
  2. Irradiance 500 W/m2, cell temperature 25 C, air mass 1.5 spectrum
  3. Irradiance 1000 W/m2, cell temperature 25 C, air mass 1.5 spectrum Correct answer.
  4. Irradiance 1000 W/m2, ambient temperature 50 C, air mass 2.0 spectrum

Explanation

Standard test conditions fix irradiance at 1000 W/m2, cell temperature at 25 C and the reference spectrum at air mass 1.5. These three values must all be quoted together because module power falls when cell temperature rises or irradiance drops. Any other combination describes a different operating point, not the nameplate rating.

Question 3Solar Photovoltaic Fundamentals and System Types

Which semiconductor material is used in the majority of solar modules sold worldwide today?

  1. Crystalline silicon Correct answer.
  2. Gallium arsenide
  3. Amorphous germanium
  4. Cadmium telluride

Explanation

Crystalline silicon, both monocrystalline and polycrystalline, dominates commercial module production because of mature manufacturing, stable supply and good efficiency. Cadmium telluride and gallium arsenide are used in thin-film and high-cost specialty cells respectively. Amorphous germanium is not a mainstream PV absorber material.

Question 4Solar Photovoltaic Fundamentals and System Types

A small off-grid home needs power at night. Which system type is required?

  1. A stand-alone system with a battery bank and charge controller Correct answer.
  2. A grid-tied system with a net meter only
  3. A direct-coupled pump system without storage
  4. A grid-tied system without any battery

Explanation

Night-time use without a utility connection requires stored energy, so a stand-alone system must include a battery bank and a charge controller to regulate charging. A grid-tied system supplies loads only when the grid is present. A direct-coupled pump runs only while the sun shines and has no storage.

Question 5Solar Photovoltaic Fundamentals and System Types

What is the primary purpose of a bypass diode in a solar module?

  1. Prevent the battery from discharging back through the modules at night
  2. Increase the open-circuit voltage of the module in full sun
  3. Provide an alternate current path around a shaded cell string to limit hot-spot heating Correct answer.
  4. Convert the module DC output into grid-synchronized AC

Explanation

When a cell or substring is shaded, it can be forced into reverse bias by the current from illuminated cells and overheat. A bypass diode provides a parallel path so current bypasses the shaded substring, limiting hot-spot damage and power loss. Voltage boosting, night-time blocking and inversion are performed by other components.

Question 6Solar Photovoltaic Fundamentals and System Types

Which instrument reading is used to measure the short-circuit current of a PV module during a field check?

  1. An insulation resistance tester applied between terminals and frame
  2. A voltmeter connected across the open terminals with no load
  3. A wattmeter connected to the inverter AC output
  4. A clamp meter or ammeter connected across the module terminals with the module in sun Correct answer.

Explanation

Short-circuit current is measured with the module terminals shorted through a suitable ammeter or clamp meter while the module is illuminated. Open-terminal voltage measurement gives open-circuit voltage, not current. Insulation testing checks leakage to the frame, and AC output measurement belongs to the inverter side.

Question 7Solar Photovoltaic Fundamentals and System Types

At the same rated power, how does a monocrystalline module generally compare with a polycrystalline module?

  1. It has a lower efficiency and a distinctly blue mottled surface
  2. It cannot be used in rooftop systems because of its weight
  3. It has slightly higher efficiency and a more uniform dark appearance Correct answer.
  4. It requires a battery to operate in a grid-tied array

Explanation

Monocrystalline cells are cut from a single crystal, giving higher efficiency and a uniform black appearance. Polycrystalline cells show visible grain boundaries and a blue mottled look with slightly lower efficiency. Both types work equally well in rooftop and grid-tied arrays and need no battery.

Question 8Solar Photovoltaic Fundamentals and System Types

A module datasheet lists a temperature coefficient of power of -0.40 percent per degree C. On a hot day when the cell temperature is 55 C, what approximate change in power from STC should be expected?

  1. About 12 percent lower than the STC rating Correct answer.
  2. No change, because only voltage is affected
  3. About 12 percent higher than the STC rating
  4. About 40 percent lower than the STC rating

Explanation

The cell is 30 C above the 25 C STC reference, so the loss is 30 times 0.40 percent, which is about 12 percent. The coefficient is negative, so power falls as temperature rises. A 40 percent figure would require a 100 C rise, which is unrealistic in the field.

Question 9Solar Photovoltaic Fundamentals and System Types

Two 12 V nominal, 100 Ah batteries are connected in series. What is the resulting bank voltage and capacity?

  1. 24 V and 200 Ah
  2. 12 V and 100 Ah
  3. 12 V and 200 Ah
  4. 24 V and 100 Ah Correct answer.

Explanation

Series connection adds voltages while the ampere-hour capacity stays the same as a single unit. So 12 V plus 12 V gives 24 V, and the capacity remains 100 Ah. Parallel connection would instead give 12 V and 200 Ah.

Question 10Solar Photovoltaic Fundamentals and System Types

A charge controller rated for 30 A is used with a 24 V battery bank. What is the maximum PV array power it can handle, ignoring losses?

  1. 720 W Correct answer.
  2. 360 W
  3. 240 W
  4. 1440 W

Explanation

For a PWM-style controller the current rating applies at battery voltage, so power equals 30 A times 24 V, which is 720 W. Doubling to 1440 W would require 48 V, and halving to 360 W would require 12 V. The 240 W figure corresponds to only 8 A, which is not the rating given.

Question 11Solar Photovoltaic Fundamentals and System Types

Why must a grid-tied inverter with no battery be fitted with an anti-islanding function?

  1. To prevent the modules from overheating in strong sunlight
  2. To boost the array voltage to the grid voltage level
  3. To balance the state of charge between parallel battery strings
  4. To disconnect the inverter when the grid fails so it does not energize lines being repaired Correct answer.

Explanation

If the utility supply fails while the inverter keeps energizing the local wiring, a dangerous island is formed that can injure line workers. Anti-islanding detection trips the inverter within a defined time when grid voltage or frequency goes out of range. Voltage boosting, thermal protection and battery balancing are unrelated functions.

Question 12Solar Photovoltaic Fundamentals and System Types

In a series string of ten modules, one module is completely shaded while the others are in full sun. What is the most likely effect?

  1. Only the shaded module stops producing, and the string current is unchanged
  2. The whole string produces full power because voltage is unaffected
  3. The string current is limited and the shaded module may heat up unless bypass diodes act Correct answer.
  4. The string voltage doubles to compensate for the shaded module

Explanation

Modules in series carry the same current, so a shaded module restricts the whole string unless its bypass diode conducts. Without bypass action the shaded cell can be driven into reverse bias and develop a hot spot. The string cannot maintain full power, and voltage does not double to compensate.

Question 13Solar Photovoltaic Fundamentals and System Types

A PV module has an open-circuit voltage of 22 V and a temperature coefficient of Voc of -0.3 percent per degree C. What is the approximate Voc at a cell temperature of 5 C?

  1. About 25.0 V
  2. About 23.3 V Correct answer.
  3. About 22.0 V
  4. About 20.7 V

Explanation

The cell is 20 C below the 25 C reference, so the voltage rises by 20 times 0.3 percent, which is 6 percent of 22 V, or about 1.3 V. Adding this to 22 V gives roughly 23.3 V. Cold conditions raise Voc, which matters when checking inverter maximum input voltage.

Question 14Solar Photovoltaic Fundamentals and System Types

Which mounting arrangement best describes a pole-mounted module used for a small street light?

  1. A stand-alone module charging a battery that runs the lamp at night Correct answer.
  2. A grid-tied array exporting power through a net meter
  3. A direct-coupled array driving an AC pump during daylight
  4. A rooftop array connected to a string inverter

Explanation

Street lights must operate after dark, so a pole-mounted module typically charges a battery through a charge controller and the battery runs the lamp at night. There is usually no grid connection or net meter. An AC pump and a string inverter describe different system types.

Question 15Solar Photovoltaic Fundamentals and System Types

What is the main reason for using an MPPT charge controller instead of a simple PWM controller in an off-grid system?

  1. It removes the need for a battery in the system
  2. It physically tracks the sun across the sky
  3. It operates the array near its maximum power point, extracting more energy when array voltage is well above battery voltage Correct answer.
  4. It converts the battery DC into grid-quality AC for export

Explanation

An MPPT controller continuously adjusts the operating voltage to hold the array near its maximum power point, which yields more energy especially when the array voltage is much higher than the battery voltage. A PWM controller simply clamps the array to battery voltage. Neither type removes the battery or performs inversion or mechanical tracking.

Question 16Solar Photovoltaic Fundamentals and System Types

A technician measures 0 V across a module's terminals in full sun and finds the junction box lid loose with water inside. What is the most probable cause?

  1. The module is operating normally at its maximum power point
  2. The bypass diode is boosting the voltage too high
  3. The inverter is limiting the array current
  4. An open circuit in the module wiring or a failed internal connection at the junction box Correct answer.

Explanation

Zero volts at the terminals in good sunlight indicates an open circuit somewhere in the module or its leads, and water ingress at a loose junction box commonly corrodes or breaks the internal connections. A healthy module would show roughly its open-circuit voltage. Bypass diodes and the inverter cannot reduce terminal voltage to zero in this way.

Question 17Solar Photovoltaic Fundamentals and System Types

Which condition would cause a grid-tied inverter to display a grid fault and stop exporting power?

  1. Grid voltage rising above the permitted upper limit Correct answer.
  2. Battery state of charge reaching full
  3. Array open-circuit voltage remaining within the input window
  4. Module irradiance increasing on a clear afternoon

Explanation

Grid-tied inverters monitor voltage and frequency and trip when either moves outside the permitted window, so an over-voltage condition produces a grid fault. Higher irradiance simply raises input power. State of charge applies only to systems with batteries, and an input voltage inside the window is a normal condition.

Question 18Solar Photovoltaic Fundamentals and System Types

What distinguishes a hybrid solar system from a standard grid-tied system?

  1. It includes a battery bank and can supply selected loads during a grid outage Correct answer.
  2. It operates only at night
  3. It uses no inverter at all
  4. It exports all generated energy and supplies no local load

Explanation

A hybrid system combines grid connection with battery storage, so it can keep critical loads running when the grid fails. A standard grid-tied system has no storage and shuts down during an outage. Hybrid systems still use an inverter and can serve local loads while the grid is present.

Question 19Solar Photovoltaic Fundamentals and System Types

A module's I-V curve shows current nearly constant until the knee, then falling steeply to zero at Voc. What does the point at the knee represent?

  1. The maximum power point, where the product of current and voltage is greatest Correct answer.
  2. The short-circuit current point, where voltage is zero
  3. The reverse-breakdown region of the cells
  4. The open-circuit point, where current is zero

Explanation

On the I-V curve the knee is the maximum power point, where the current-voltage product peaks and the inverter or MPPT controller aims to operate. The short-circuit point lies on the current axis at zero volts, and the open-circuit point lies on the voltage axis at zero current. Reverse breakdown occurs at negative voltages.

Question 20Solar Photovoltaic Fundamentals and System Types

An array of four identical modules in series feeds an MPPT inverter. If one module is removed and the string is reconnected with three modules, how do string voltage and current at the maximum power point change?

  1. Voltage stays the same while current falls to three quarters
  2. Voltage rises because the load per module increases
  3. Both voltage and current fall to three quarters
  4. Voltage falls to about three quarters while current stays approximately the same Correct answer.

Explanation

In a series string the voltages add while the current is set by each module, so removing one module reduces string voltage in proportion to the count. Current at the maximum power point remains essentially unchanged because the remaining modules are identical. Power therefore falls to about three quarters.

Question 21Solar Photovoltaic Fundamentals and System Types

A 3 kW grid-tied array in a location with 4.5 peak sun hours per day is expected to generate about how much energy daily, before losses?

  1. About 13.5 kWh Correct answer.
  2. About 45 kWh
  3. About 3 kWh
  4. About 0.67 kWh

Explanation

Daily energy equals array rating times peak sun hours, so 3 kW times 4.5 h gives about 13.5 kWh before losses. Dividing instead of multiplying gives 0.67, and using the rating alone ignores the sun hours. The 45 kWh figure would require 15 peak sun hours, which is not physically possible in a day.

Question 22Solar Photovoltaic Fundamentals and System Types

A string inverter has a maximum input voltage of 600 V and the modules have a cold-condition Voc of 41 V each. What is the largest number of modules that can be connected in series with a safe margin?

  1. 16 modules
  2. 14 modules Correct answer.
  3. 15 modules
  4. 12 modules

Explanation

Fifteen modules at 41 V would reach 615 V, above the 600 V limit, so the string must be limited to 14 modules, giving 574 V. Fourteen also leaves a small margin for measurement tolerance. Twelve is unnecessarily conservative, and 16 would clearly exceed the limit.

Question 23Solar Photovoltaic Fundamentals and System Types

Why does a crystalline silicon module's power output fall more steeply than its current when cell temperature rises?

  1. The bypass diodes begin to conduct and short the string
  2. Current falls markedly while voltage stays fixed
  3. Both current and voltage rise equally with temperature
  4. Voltage falls markedly with temperature while current rises only slightly Correct answer.

Explanation

Rising temperature reduces the bandgap voltage of the cells, so Voc drops noticeably while the small increase in current does not offset it. The net effect is a fall in power, described by the negative power temperature coefficient. Bypass diodes do not conduct merely because the module is warm.

Question 24Solar Photovoltaic Fundamentals and System Types

A technician finds that an off-grid battery bank is not reaching full charge although the array is clean and unshaded. Which measurement sequence best isolates the cause?

  1. Replace the battery first, then check the modules
  2. Increase the load until the battery discharges fully
  3. Compare array open-circuit voltage, charge-controller input and output current, and battery terminal voltage under load Correct answer.
  4. Measure only the inverter AC output

Explanation

A logical sequence checks each stage from array to battery: array Voc confirms the source, controller input and output current show whether the controller is passing charge, and battery voltage under load reveals battery condition. Replacing parts before measuring wastes effort. Inverter output and forced discharge do not diagnose a charging problem.

Question 25Solar Cell, Module and Panel Construction and Rating

In a standard photovoltaic module datasheet, what does the term 'open-circuit voltage' (Voc) refer to?

  1. The voltage measured across the module terminals when no load is connected and no current flows Correct answer.
  2. The voltage at the maximum power point under standard test conditions
  3. The voltage when the module is short-circuited through an ammeter
  4. The voltage required to charge a 12 V battery bank directly

Explanation

Open-circuit voltage is the potential difference across the module terminals when the external circuit is open, so no current flows. It is the highest voltage the module produces and is measured under Standard Test Conditions for the datasheet. It is not the operating voltage at maximum power, which is lower.

Question 26Solar Cell, Module and Panel Construction and Rating

A solar cell is described as having a fill factor of about 0.75. What does the fill factor express?

  1. The ratio of the maximum power to the product of Voc and Isc Correct answer.
  2. The ratio of open-circuit voltage to short-circuit current
  3. The percentage of sunlight converted to heat rather than electricity
  4. The ratio of the module area covered by cells to the total module area

Explanation

Fill factor compares the maximum power the cell can deliver with the theoretical product of open-circuit voltage and short-circuit current. A higher fill factor means the I-V curve is closer to a rectangle and the cell is of better quality. Typical crystalline cells fall in the range of roughly 0.75 to 0.85.

Question 27Solar Cell, Module and Panel Construction and Rating

Which material is most commonly used as the absorber layer in the thin-film modules sold for large rooftop and utility installations?

  1. Monocrystalline silicon
  2. Cadmium telluride Correct answer.
  3. Polycrystalline silicon
  4. Amorphous silicon

Explanation

Cadmium telluride (CdTe) is the leading thin-film absorber material by installed volume, alongside CIGS. Monocrystalline and polycrystalline silicon are wafer-based, not thin-film. Amorphous silicon is a thin-film material but has a much smaller market share than CdTe.

Question 28Solar Cell, Module and Panel Construction and Rating

What does the 'STC' label on a module nameplate stand for, and what conditions does it specify?

  1. Steady Test Conditions: 600 W/m² irradiance, 25 °C ambient temperature, AM 1.5 spectrum
  2. Standard Thermal Conditions: 1000 W/m² irradiance, 45 °C cell temperature, AM 1.5 spectrum
  3. Standard Test Conditions: 1000 W/m² irradiance, 25 °C cell temperature, AM 1.5 spectrum Correct answer.
  4. System Test Conditions: 800 W/m² irradiance, 20 °C ambient temperature, AM 1.0 spectrum

Explanation

Standard Test Conditions fix irradiance at 1000 W/m², cell temperature at 25 °C and the air mass 1.5 reference spectrum. These values let manufacturers compare modules on a common basis. Real installations rarely match STC, so field output usually differs from the nameplate figure.

Question 29Solar Cell, Module and Panel Construction and Rating

A module datasheet lists a temperature coefficient of power of −0.40 %/°C. If the cell temperature rises 25 °C above STC, roughly how does the power change?

  1. It falls by about 10 % Correct answer.
  2. It rises by about 10 %
  3. It falls by about 40 %
  4. It stays the same because voltage and current offset each other

Explanation

Multiply the coefficient by the temperature rise: 0.40 %/°C × 25 °C = 10 %. Because the coefficient is negative, power decreases by roughly 10 %. This is why hot modules deliver noticeably less than their nameplate rating.

Question 30Solar Cell, Module and Panel Construction and Rating

Why are bypass diodes fitted inside a photovoltaic module's junction box?

  1. To provide an alternative current path around shaded cells and prevent hot-spot overheating Correct answer.
  2. To block reverse current from the battery at night
  3. To convert the module's DC output into AC for the inverter
  4. To raise the module's open-circuit voltage above its STC value

Explanation

When part of a module is shaded, the shaded cells can be forced into reverse bias by the current from lit cells. Bypass diodes route current around the affected substring, limiting power loss and preventing damaging hot spots. They are wired across groups of cells, not across the whole array.

Question 31Solar Cell, Module and Panel Construction and Rating

A module has 60 cells connected in series, each with an open-circuit voltage of 0.6 V. What is the module's approximate open-circuit voltage?

  1. 6 V
  2. 360 V
  3. 0.6 V
  4. 36 V Correct answer.

Explanation

Series connection adds voltages while current stays the same, so 60 × 0.6 V = 36 V. This is typical for a 60-cell module. Cell current would determine the module current, but voltage simply sums.

Question 32Solar Cell, Module and Panel Construction and Rating

Why are the cells in a module connected in series rather than in parallel?

  1. Series connection raises the voltage to a useful level while keeping current low, reducing resistive losses Correct answer.
  2. Series connection allows each cell to be removed without stopping the current
  3. Parallel connection would make each cell produce a lower voltage than it can physically generate
  4. Parallel connection cannot be used with crystalline silicon cells

Explanation

A single silicon cell produces only about 0.5 to 0.6 V, which is too low for practical systems. Connecting cells in series sums their voltages while keeping the current at the level of one cell, which limits I²R losses in wiring. Parallel connection would raise current instead of voltage.

Question 33Solar Cell, Module and Panel Construction and Rating

What does the IEC 61215 standard primarily certify for a crystalline silicon module?

  1. The measured energy yield of the module over a full year of field operation
  2. The maximum system voltage permitted by the local electricity authority
  3. Design qualification and type approval through a sequence of environmental and mechanical stress tests Correct answer.
  4. The fire resistance class of the module's mounting structure

Explanation

IEC 61215 sets out design qualification and type approval tests such as thermal cycling, damp heat and mechanical load. Passing it shows the design can withstand expected field stresses, not that a particular production unit performs to a measured energy yield. IEC 61730 separately addresses safety.

Question 34Solar Cell, Module and Panel Construction and Rating

A module's nameplate reads 450 Wp. What does the 'p' in Wp indicate?

  1. Peak wattage measured at Standard Test Conditions Correct answer.
  2. The wattage available at the maximum system voltage
  3. The wattage after temperature derating
  4. The average wattage over a typical day

Explanation

Wp means watt-peak, the power output measured at the defined STC reference conditions. It is a rating for comparison, not a promise of continuous output. Real output varies with irradiance, temperature and soiling.

Question 35Solar Cell, Module and Panel Construction and Rating

Which quantity does the short-circuit current (Isc) of a module most closely track as irradiance changes?

  1. The open-circuit voltage, which stays fixed
  2. Cell temperature, rising sharply as the module heats
  3. Irradiance, rising almost linearly with light level Correct answer.
  4. The module's series resistance, which falls with light

Explanation

Short-circuit current is generated by the photocurrent, which is nearly proportional to the number of photons arriving, so it tracks irradiance closely. Voltage, by contrast, changes only logarithmically with irradiance. Temperature has a small positive effect on current compared with the strong effect of light.

Question 36Solar Cell, Module and Panel Construction and Rating

Why does a module's maximum power voltage (Vmp) fall as cell temperature increases?

  1. Series resistance drops sharply when the module heats up
  2. The diode forward voltage of the cell junction decreases with temperature Correct answer.
  3. The photocurrent increases faster than the voltage can compensate
  4. The bypass diodes begin to conduct and clamp the voltage

Explanation

Heating a silicon cell reduces the junction's forward voltage for a given current, so the whole I-V curve shifts to lower voltage. Current rises only slightly, so maximum power falls. This is why the temperature coefficient of power is negative.

Question 37Solar Cell, Module and Panel Construction and Rating

In a half-cut cell module, each cell is split and the two halves are connected in a particular way. What is the main electrical benefit?

  1. The cell temperature coefficient becomes positive
  2. The halves are wired in parallel within the module, halving resistive losses and improving shade tolerance Correct answer.
  3. Each half produces double the voltage of a full cell
  4. The module no longer needs bypass diodes

Explanation

Half-cut cells are separated and the two halves connected so that current per half is halved and resistive I²R losses fall. The layout also allows the two halves to be managed in separate substrings, which improves tolerance to partial shading. The voltage per cell is unchanged.

Question 38Solar Cell, Module and Panel Construction and Rating

What is the purpose of the encapsulant (typically EVA) in a photovoltaic module?

  1. It provides the structural mounting points for the frame
  2. It reflects unused light back into the cells to raise voltage
  3. It bonds the cells, glass and backsheet together and electrically insulates them while protecting against moisture Correct answer.
  4. It conducts current between adjacent cells in the string

Explanation

The encapsulant laminates the module stack, holding cells in place and sealing them from moisture and contaminants. It is electrically insulating, so it does not carry current. Structural mounting is provided by the frame and the glass, not by the encapsulant.

Question 39Solar Cell, Module and Panel Construction and Rating

A module's I-V curve shows a noticeable 'step' or kink. Which condition most likely explains this?

  1. The cell temperature is exactly 25 °C
  2. The irradiance is above 1000 W/m²
  3. The module is operating at exactly its maximum power point
  4. Part of the module is shaded or has a faulty cell substring, activating a bypass diode Correct answer.

Explanation

A step in the I-V curve typically appears when a bypass diode turns on to route current around a shaded or faulty substring. The curve then shows two distinct regions. Normal operation at any irradiance or temperature does not create a kink.

Question 40Solar Cell, Module and Panel Construction and Rating

Two identical modules are connected in parallel. How do the combined voltage and current compare with a single module?

  1. Voltage halves and current doubles
  2. Both voltage and current double
  3. Voltage stays the same and current doubles Correct answer.
  4. Voltage doubles and current stays the same

Explanation

In a parallel connection the voltages across the branches are equal, so the array voltage equals one module's voltage. The currents from each branch add, so the total current doubles for two identical modules. This is the opposite behaviour to a series connection.

Question 41Solar Cell, Module and Panel Construction and Rating

A crystalline silicon module is rated 400 W at STC with a temperature coefficient of power of −0.35 %/°C. Its cells reach 60 °C in operation at 1000 W/m². What is the approximate power output?

  1. About 260 W
  2. About 400 W
  3. About 449 W
  4. About 351 W Correct answer.

Explanation

The cell temperature is 35 °C above STC, so the loss is 0.35 %/°C × 35 °C ≈ 12.25 %. Applying this to 400 W gives roughly 351 W. The calculation assumes irradiance stays at 1000 W/m² so only temperature derating applies.

Question 42Solar Cell, Module and Panel Construction and Rating

A module's datasheet gives a NOCT of 45 °C. Under which conditions is NOCT defined?

  1. 600 W/m² irradiance, 35 °C ambient air temperature and 2 m/s wind speed
  2. 1000 W/m² irradiance, 20 °C ambient air temperature and no wind
  3. 800 W/m² irradiance, 20 °C ambient air temperature and 1 m/s wind speed with the back open-mounted Correct answer.
  4. 1000 W/m² irradiance, 25 °C cell temperature and AM 1.5 spectrum

Explanation

Nominal Operating Cell Temperature is measured at 800 W/m², 20 °C ambient, 1 m/s wind with the module open-mounted on its back. It estimates the cell temperature a module reaches in realistic conditions. It is deliberately not the STC set of conditions.

Question 43Solar Cell, Module and Panel Construction and Rating

An installer must choose a module for a site where partial shading of one cell string is unavoidable each afternoon. Which design feature most directly limits the resulting power loss and hot-spot risk?

  1. A thicker aluminium frame around the laminate
  2. Multiple bypass diodes dividing the module into independent substrings Correct answer.
  3. A larger junction box with more cable glands
  4. A higher open-circuit voltage rating for the whole module

Explanation

Bypass diodes across separate substrings let current detour around the shaded group, so only that substring's contribution is lost and reverse-bias heating is avoided. More substrings mean finer granularity of shade tolerance. Frame thickness and junction box size do not affect electrical shade behaviour.

Question 44Solar Cell, Module and Panel Construction and Rating

A 72-cell module and a 60-cell module use the same cell type and are compared at STC. Which statement about their open-circuit voltages is correct?

  1. The 60-cell module has a higher Voc because it has fewer cells
  2. Voc depends only on irradiance and not on cell count
  3. Both modules have the same Voc because cell type is identical
  4. The 72-cell module has a higher Voc because series cell voltages add Correct answer.

Explanation

Series-connected cells add their voltages, so a 72-cell module produces about 20 % more open-circuit voltage than a 60-cell module of the same cell type. Current is set by cell area and type and is essentially the same for both. Cell count therefore changes voltage, not current.

Question 45Batteries, Charge Controllers and Energy Storage

A solar home system uses a 12 V lead-acid battery. Which nominal voltage setting must be selected on the charge controller before connecting the array?

  1. 48 V
  2. 24 V
  3. 12 V Correct answer.
  4. 6 V

Explanation

The controller's battery-voltage setting must match the nominal voltage of the battery bank, which here is 12 V. Selecting a higher setting would apply charging voltages meant for a larger bank and could overcharge the battery.

Question 46Batteries, Charge Controllers and Energy Storage

Which battery chemistry is most commonly paired with a low-cost PWM charge controller in small solar home systems because of its tolerance to simple constant-voltage charging?

  1. Nickel-cadmium
  2. Lithium iron phosphate
  3. Flooded lead-acid Correct answer.
  4. Lithium cobalt oxide

Explanation

Flooded lead-acid batteries accept the simple on/off constant-voltage charging that a PWM controller provides and are the traditional pairing in low-cost systems. Lithium chemistries need stricter voltage and current control than a basic PWM unit gives.

Question 47Batteries, Charge Controllers and Energy Storage

What is the main advantage of an MPPT charge controller over a PWM controller in a solar repair job?

  1. It allows the battery to be connected in reverse polarity
  2. It removes the need for battery overcharge protection
  3. It converts excess array voltage into additional charging current Correct answer.
  4. It eliminates the need for a blocking diode

Explanation

An MPPT controller tracks the array's maximum power point and steps the higher array voltage down to battery voltage while increasing current, recovering power a PWM unit would waste. This matters most when array voltage is well above battery voltage.

Question 48Batteries, Charge Controllers and Energy Storage

A charge controller is rated at 30 A. What does this rating primarily limit in the system?

  1. The maximum current the controller can pass to or from the battery Correct answer.
  2. The maximum wattage of each individual module
  3. The maximum number of batteries in the bank
  4. The maximum open-circuit voltage of the array

Explanation

The ampere rating of a controller defines the highest current it can handle on the battery side, which sets the array size it can support at a given battery voltage. Exceeding it risks overheating and failure.

Question 49Batteries, Charge Controllers and Energy Storage

During equalisation charging of a flooded lead-acid battery, what is the intended purpose of the controlled overcharge?

  1. To lower the battery's internal resistance permanently
  2. To mix the electrolyte and reduce stratification Correct answer.
  3. To convert the positive plates to a different alloy
  4. To reduce the battery's water consumption

Explanation

Equalisation deliberately raises the voltage to cause gassing, which stirs the electrolyte and evens out acid concentration between top and bottom of the cell. It also helps break up soft sulphation on the plates.

Question 50Batteries, Charge Controllers and Energy Storage

A technician measures a fully charged 12 V lead-acid battery at rest and reads 12.1 V. What does this indicate?

  1. The battery is only partially charged and needs charging Correct answer.
  2. The battery is being overcharged
  3. The battery has a shorted cell
  4. The battery is fully charged and healthy

Explanation

A healthy 12 V lead-acid battery at rest and fully charged reads about 12.6 to 12.8 V. A reading near 12.1 V corresponds to roughly half charge, so the battery needs charging and testing.