PV Modules, Arrays, Characterization and Reliability

Introduction and Context

A photovoltaic (PV) system converts sunlight directly into electricity through semiconductor devices. Although the solar cell is the fundamental energy-conversion unit, practical systems are designed around modules, strings, arrays, power-conditioning equipment, mounting structures, and protection devices. The electrical behavior and long-term reliability of a PV plant depend not only on the rated power of individual modules but also on interconnection, operating temperature, irradiance, mismatch, shading, environmental stress, and maintenance practice.

This chapter develops the engineering basis for evaluating PV modules and arrays. It explains current–voltage characteristics, datasheet interpretation, standard test conditions, series and parallel configurations, bypass and blocking diodes, mismatch and partial shading, hot-spot formation, degradation, reliability, warranties, and certification. The emphasis is on analysis useful to an electrical engineer selecting, designing, commissioning, or diagnosing a PV installation.

Learning Objectives

After studying this chapter, the reader should be able to:

1. Explain the electrical characteristics of a PV cell, module, string, and array.
2. Interpret module datasheets and distinguish rated values from operating values.
3. Analyze series and parallel array configurations, including voltage, current, and power limits.
4. Explain the purposes and limitations of bypass and blocking diodes.
5. Evaluate mismatch, partial shading, hot spots, and their effects on energy yield.
6. Calculate basic performance indicators such as fill factor and performance ratio.
7. Describe degradation mechanisms, reliability tests, warranties, and certification requirements.
8. Apply these concepts to practical system selection and fault diagnosis.

1. From Solar Cell to Array

1.1 The solar cell

A solar cell is a semiconductor p–n junction designed to produce a photocurrent when exposed to radiation. Under illumination, absorbed photons generate electron–hole pairs. The internal electric field of the junction separates these carriers, producing a current through an external circuit.

The illuminated cell is commonly represented by a current source, a diode, a series resistance, and a shunt resistance. A simplified single-diode equation is:

Here, I is terminal current in amperes, V is terminal voltage in volts, I_ph is photocurrent, I₀ is diode reverse saturation current, q is electronic charge, n is the diode ideality factor, k is Boltzmann’s constant, T is absolute temperature in kelvin, R_s is series resistance, and R_sh is shunt resistance. The equation assumes a lumped, steady-state model and is used for electrical characterization and simulation. More detailed models may include recombination, spectral effects, and multiple diodes.

At short circuit, V = 0 and the current is approximately the short-circuit current I_sc. At open circuit, I = 0 and the voltage is the open-circuit voltage V_oc. Between these points lies the maximum power point (MPP), defined by (V_mp, I_mp).

1.2 Modules, strings, and arrays

A module contains interconnected solar cells protected by encapsulant, front glass, a backsheet or rear glass, a frame, junction box, and cables. Cells are connected in series to obtain useful voltage. A module may contain half-cut cells, which reduce current in each cell path and can lower resistive losses. Modern modules commonly use monocrystalline silicon cells, although thin-film technologies remain important for particular applications.

A string is a series-connected group of modules. An array is a group of one or more strings connected in parallel, usually through combiner equipment or directly to an inverter.

For N_s identical modules in series:

The string current is approximately the current of one module:

For N_p identical strings in parallel:

and

These ideal relationships assume identical operating conditions and negligible wiring and conversion losses. In practice, the current and voltage depend on irradiance, temperature, mismatch, cable resistance, inverter control, and protection-device characteristics.

2. PV Electrical Characteristics

2.1 The I–V and P–V curves

The current–voltage (I–V) curve describes the current delivered by a module at each terminal voltage. At zero voltage, the current is near I_sc. As voltage increases, current remains relatively constant until the knee of the curve; after the knee, current falls rapidly toward zero at V_oc.

The power–voltage (P–V) curve is obtained from:

where P is electrical power in watts. The P–V curve has a maximum at the MPP. A maximum-power-point tracker (MPPT) in an inverter adjusts operating voltage so that the array operates near this point.

Important characteristic quantities are:

The fill factor is:

It is dimensionless. The formula applies to a measured I–V curve under a specified condition. A higher fill factor generally indicates lower resistive and recombination losses, but it is not by itself a complete measure of module quality.

2.2 Irradiance and temperature effects

Irradiance primarily affects current. Over a practical operating range, short-circuit current is approximately proportional to irradiance:

where G is irradiance in W/m² and the subscript “ref” identifies the reference condition. The approximation is most useful for crystalline-silicon modules over moderate irradiance ranges; low-light behavior is not perfectly linear.

Temperature has a strong effect on voltage. Increasing cell temperature usually decreases V_oc and V_mp, while I_sc increases slightly. Datasheets give temperature coefficients, often in %/°C or absolute units such as V/°C and A/°C. The power coefficient is generally negative.

For a first-order estimate:

where γ_P is the power temperature coefficient in per °C, T_cell is cell temperature in °C, and T_ref is the reference cell temperature. This linear approximation is valid near the reference range and should not replace a validated model for extreme conditions.

3. Standard Test Conditions and Datasheet Interpretation

3.1 Standard Test Conditions

PV module nameplate power is normally reported at Standard Test Conditions (STC): irradiance of 1000 W/m², cell temperature of 25 °C, and a defined reference spectrum, commonly AM1.5. STC is a reproducible comparison condition, not a typical outdoor operating condition. A module rated at 550 W will rarely produce exactly 550 W continuously because irradiance, cell temperature, spectrum, soiling, orientation, and system losses vary.

Datasheets may also provide values at Nominal Operating Cell Temperature (NOCT) or a related operating-temperature condition. Such values represent a more realistic thermal condition but still depend on wind, mounting, and installation geometry.

3.2 Essential datasheet fields

A professional review should examine at least the following:

• Rated maximum power, P_max or P_mp.
• Voltage and current at maximum power, V_mp and I_mp.
• Open-circuit voltage and short-circuit current, V_oc and I_sc.
• Power, voltage, and current temperature coefficients.
• Maximum system voltage and maximum series-fuse rating.
• Module dimensions, mass, connector type, and mounting restrictions.
• Operating-temperature range and fire classification.
• Bifaciality factor, if applicable.
• Product warranty and linear performance warranty.
• Applicable IEC or other national certification.

The maximum system voltage is not the same as the module’s operating voltage. Cold-weather V_oc must be used when checking the highest possible string voltage. Conversely, hot-weather V_mp must be checked against the inverter’s minimum MPPT voltage.

Worked Example 1: String voltage limits

A module has V_oc = 49.5 V, V_mp = 41.5 V, and a voltage temperature coefficient of −0.29%/°C. A designer proposes 20 modules in series. Assume the coldest cell temperature is −10 °C and the hottest cell temperature is 70 °C. Use the simple linear coefficient for an initial check.

At −10 °C, the temperature difference from 25 °C is −35 °C. The fractional voltage increase is:

0.0029 × 35 = 0.1015, or 10.15%.

Thus, the estimated cold open-circuit voltage per module is:

49.5 × 1.1015 = 54.52 V.

For 20 modules:

V_string,oc ≈ 20 × 54.52 = 1090.4 V.

At 70 °C, the difference is 45 °C and the voltage reduction is 0.0029 × 45 = 0.1305. The estimated hot maximum-power voltage per module is:

41.5 × (1 − 0.1305) = 36.08 V.

For 20 modules, V_string,mp ≈ 721.6 V. The designer must compare 1090.4 V with the permitted DC system voltage and 721.6 V with the inverter’s MPPT operating range. The calculation is preliminary because actual cell temperature, coefficient definitions, and manufacturer models should be used for final design.

4. Array Configuration and Protection

4.1 Series and parallel design

Series connection raises voltage and parallel connection raises current. The designer must simultaneously satisfy:

1. Maximum cold-weather string V_oc below the inverter and equipment voltage rating.
2. Minimum hot-weather string V_mp above the inverter’s MPPT lower limit.
3. Array current within inverter input and conductor ratings.
4. Parallel-string fault current within fuse, combiner, connector, and switch ratings.
5. Similar orientation, tilt, and shading conditions for modules sharing an MPPT input.

Modules connected to the same MPPT should have compatible electrical characteristics and similar irradiance. Combining differently oriented roof sections on one tracker can produce avoidable energy loss unless the inverter architecture is designed for it.

4.2 Bypass diodes

A bypass diode is connected antiparallel across a group of cells, usually within a module junction box. Under normal operation it is reverse-biased. If a cell group becomes strongly shaded while current is forced through the module by unshaded series-connected cells, the diode can conduct and provide an alternate path around that group.

The diode limits reverse voltage across shaded cells and reduces the probability of hot-spot damage. It does not restore the power of the shaded section: the bypassed cells no longer contribute normal voltage. A diode may also introduce forward-voltage loss and thermal stress.

Modern modules may use several bypass-diode sections, often associated with cell substrings. The exact arrangement must be confirmed from the manufacturer’s design rather than assumed from module appearance.

4.3 Blocking diodes

A blocking diode is placed in series with a string or array branch to reduce reverse current from a higher-voltage branch, battery, or parallel source into a lower-voltage branch. It is particularly relevant in some battery-coupled or independently operated systems. In grid-connected systems, string fuses and inverter architecture often provide the required protection, and a separate blocking diode may not be necessary.

Blocking diodes cause forward-voltage and power losses, generate heat, and can fail short or open. They should therefore be used only when their protective function is required and when their ratings are properly selected. A blocking diode must withstand the branch current, reverse voltage, surge conditions, and thermal environment.

5. Mismatch, Partial Shading, and Hot Spots

5.1 Electrical mismatch

Mismatch means that series or parallel-connected devices do not have identical electrical characteristics. Causes include manufacturing tolerance, different aging rates, soiling, temperature differences, orientation, shading, and degradation.

In a series string, current is constrained by the weakest module or cell path. In parallel branches, voltage tends to be common, so branches with different voltage–current characteristics exchange current or operate away from their individual MPPs. The total power is consequently less than the sum of the individual ideal maximum powers.

Mismatch can be classified as:

• Design mismatch: different module types, orientations, or string lengths.
• Manufacturing mismatch: normal variation in rated power and electrical parameters.
• Environmental mismatch: shade, dirt, snow, temperature gradients, or unequal irradiance.
• Aging mismatch: unequal degradation, connector resistance, or localized defects.

Sorting modules by measured current or power can reduce mismatch, but it cannot compensate for poor layout or changing shade.

5.2 Partial shading

Partial shading may arise from trees, nearby buildings, poles, parapets, overhead cables, dirt, bird droppings, or snow. Because cells are series-connected, a small shaded region can affect a disproportionately large part of the module’s output. Partial shading can create multiple local maxima on the array P–V curve. The inverter’s MPPT algorithm must distinguish the global maximum from local maxima; not all algorithms do this equally well.

Design responses include shade analysis, module-level power electronics, optimized string layout, separate MPPT inputs, physical trimming or relocation of obstructions, and regular cleaning where economically justified. Module-level electronics can improve energy harvest under complex shade but add cost, electronics, and additional failure points.

5.3 Hot spots

A hot spot occurs when a shaded or defective cell is driven into reverse bias by current from other cells. Instead of generating power, the cell dissipates electrical power as heat. Local temperatures may become high enough to damage metallization, encapsulant, solder joints, backsheet, or the cell itself.

Hot-spot risk is influenced by reverse-bias characteristics, shaded-cell area, string current, bypass-diode operation, thermal dissipation, and defect geometry. A bypass diode reduces the stress on a shaded cell group but cannot prevent every hot spot. Infrared thermography under suitable operating conditions is a useful diagnostic method, although interpretation requires attention to wind, emissivity, reflections, and load state.

6. Characterization and Performance Assessment

6.1 I–V curve tracing

An I–V tracer sweeps the module or string through operating points while measuring voltage, current, irradiance, and temperature. A useful test record includes equipment calibration, plane-of-array irradiance, module temperature, wind conditions, test time, wiring configuration, and uncertainty.

Measured data may be compared with datasheet values after correcting for irradiance and temperature. The comparison must be made cautiously: spectral mismatch, angle of incidence, sensor error, unstable irradiance, and temperature nonuniformity can produce apparent deviations that are not module faults.

Characteristic signatures include:

• Reduced current with approximately normal voltage: soiling, shading, or irradiance loss.
• Reduced voltage with normal current: series resistance, cell loss, or excessive temperature.
• Rounded knee and reduced fill factor: increased series resistance or shunt leakage.
• Multiple steps in the I–V curve: partial shading, bypass-diode conduction, or unequal submodule behavior.
• Near-zero current or voltage: open circuit, short circuit, connector, or wiring fault.

6.2 Performance ratio

The performance ratio (PR) compares actual energy yield with the theoretical yield based on reference irradiance. A common formulation for a grid-connected system is:

where Y_f = E_AC/P₀ is the final yield in hours, E_AC is AC energy delivered during the period in kWh, P₀ is installed DC rated power in kW, and Y_r = H_POA/G_ref is the reference yield in hours. H_POA is plane-of-array irradiation in kWh/m² and G_ref is reference irradiance, conventionally 1 kW/m².

PR is dimensionless. It incorporates temperature, soiling, mismatch, wiring, inverter, availability, and other losses. It should be reported with the period, irradiation source, system boundary, and treatment of downtime clearly stated. PR is not the same as capacity factor and should not be compared across systems without considering climate, orientation, tracking, and measurement practice.

Worked Example 2: Performance ratio

A 500 kWdc plant delivers 720,000 kWh AC in one year. The measured plane-of-array irradiation is 1,650 kWh/m², and G_ref = 1 kW/m².

The final yield is:

Y_f = 720000/500 = 1440 h.

The reference yield is:

Y_r = 1650/1 = 1650 h.

Therefore:

PR = 1440/1650 = 0.8727 ≈ 87.3%.

This value does not mean that the modules are 87.3% efficient. It means that 87.3% of the irradiation-normalized ideal energy yield, within the stated system boundary, was delivered as measured AC energy.

7. Reliability, Degradation, and Failure Mechanisms

7.1 Degradation

PV degradation is the gradual reduction of power or other performance parameters over time. A simple linear model is:

where P₀ is initial power, r is annual degradation rate expressed as a fraction per year, and t is time in years. This model is useful for estimation but does not capture early-life degradation, nonlinear aging, or repair and replacement.

A more realistic warranty model may specify an initial degradation allowance followed by a lower annual rate. For example, light-induced degradation can occur early, followed by approximately linear degradation. Actual rates depend on cell technology, encapsulation, climate, installation, and measurement uncertainty.

7.2 Common failure mechanisms

The same visual symptom may have different causes. Diagnosis should combine visual inspection, electrical tests, infrared imaging, insulation testing, electroluminescence, and review of environmental and operational history.

7.3 Reliability testing and certification

Certification tests are intended to demonstrate conformity with defined safety, construction, and performance requirements; they are not a guarantee that every module will survive every climate or installation error. Common international frameworks include IEC 61215 for design qualification and type approval of terrestrial PV modules and IEC 61730 for module safety qualification. Exact editions and national adoptions should be verified before procurement.

Qualification testing can include thermal cycling, damp heat, humidity-freeze, UV exposure, mechanical load, hail impact, bypass-diode operation, wet leakage, and electrical insulation tests. Extended or climate-specific tests may be required for coastal, desert, high-humidity, high-altitude, or high-snow environments.

Quality assurance should also evaluate factory process control, traceability, sampling plans, electroluminescence inspection, flash-test consistency, incoming inspection, and field-service capability. A certificate confirms compliance with the scope of the test; it does not eliminate the need for engineering due diligence.

7.4 Warranties

A product warranty generally covers defects in materials and workmanship for a specified period. A performance warranty specifies a minimum retained power after stated years. Engineers should examine exclusions, allowable measurement uncertainty, claim procedures, transferability, labor and transport coverage, company financial strength, and the definition of a valid measurement.

Warranty percentages should not be interpreted as a direct prediction of every module’s output. They are contractual thresholds, often measured under defined conditions and subject to sampling and tolerance rules. Independent reliability data and supplier history are valuable complements.

8. Applied Case: Diagnosing Low Yield in a Commercial Rooftop System

Background

This illustrative case concerns a 250 kWdc rooftop array commissioned in a warm, dusty climate. Six months after commissioning, the owner observes that energy yield is approximately 12% below the modeled value. The inverter reports no major alarms.

Problem

The plant’s monthly PR is 74%, whereas comparable nearby systems report approximately 82–85% under similar irradiation. The owner initially suspects defective modules.

Analysis

The engineering team first validates the irradiation sensor and energy meter. The plane-of-array sensor is found to be clean and correctly oriented. The team then compares inverter MPPT voltages and currents. Two MPPTs show normal voltage but 8–10% lower current than expected.

A daytime visual inspection identifies dust accumulation and several bird-dropping patterns. Thermal imaging reveals narrow hot regions on three modules near a parapet. An I–V test on the affected strings shows a stepped curve and reduced current, consistent with partial shading and bypass-diode activation. Electroluminescence inspection later identifies cell cracks in one module, probably caused by installation handling.

The string layout also reveals that modules on two roof planes with different shading profiles were combined on the same MPPT. During morning and afternoon shade, this arrangement increases mismatch.

Approach and solution

The corrective plan includes:

1. Cleaning the array under a controlled maintenance procedure.
2. Replacing the cracked module and testing neighboring modules.
3. Reconfiguring strings so roof planes with distinct orientations and shade patterns use separate MPPT inputs.
4. Removing a minor obstruction where permitted by site safety and property constraints.
5. Checking connector torque, polarity, insulation resistance, and bypass-diode behavior.
6. Establishing monthly PR review and quarterly thermal inspection during the first year.

Outcome

After cleaning and reconfiguration, the affected MPPT currents return close to expected values. The monthly PR increases to 84%, while a small residual difference is attributed to temperature, inverter conversion, and normal modeling uncertainty.

Learning points

The case demonstrates that low yield is not automatically evidence of widespread module failure. Accurate diagnosis requires separating irradiation measurement error, soiling, shading, mismatch, wiring, inverter behavior, and module defects. Array configuration and maintenance can be as important as nameplate module quality.

9. Professional Practice, Safety, and Contemporary Developments

PV circuits can remain energized in daylight even when the inverter is disconnected. DC arcs are difficult to extinguish, and incorrect connector mating can create high-resistance heating. Work should follow applicable electrical codes, lockout procedures, arc-flash controls, personal protective equipment requirements, and manufacturer instructions. Modules should not be disconnected under load unless the switching device is rated for that duty.

Procurement decisions should consider lifecycle energy yield, traceability, repairability, environmental conditions, recyclability, and supplier governance rather than rated watts alone. Responsible practice includes avoiding misleading warranty claims, documenting test uncertainty, protecting worker safety, and managing end-of-life modules and electronic equipment.

Contemporary developments include n-type silicon architectures, tunnel-oxide passivated contacts, heterojunction cells, larger wafers, half-cut and multi-busbar designs, bifacial modules, rear-side irradiance modeling, module-level power electronics, and automated inspection using drones, infrared cameras, and machine-learning image analysis. AI-assisted fault classification can prioritize inspections, but it should be trained on representative data and validated by qualified engineers. A thermal image or algorithmic label is not, by itself, proof of a failure mechanism.

Best practice is therefore a closed engineering loop: characterize the resource, design within electrical limits, select certified equipment, commission with measured tests, monitor performance, investigate deviations systematically, and use field evidence to improve future designs.

Chapter Summary

PV modules and arrays are engineered systems whose behavior depends on semiconductor characteristics, interconnection, temperature, irradiance, and environmental conditions. The I–V curve identifies short-circuit current, open-circuit voltage, maximum-power voltage, maximum-power current, and maximum power. Fill factor provides a compact indication of curve quality, while the single-diode model supports analysis and simulation.

Series connections increase voltage and parallel connections increase current, but practical design must satisfy cold-voltage, hot-voltage, current, MPPT, conductor, fuse, and equipment limits. Bypass diodes reduce reverse-bias stress during shading; blocking diodes prevent unwanted reverse current where required, but both introduce losses and failure considerations.

Mismatch and partial shading reduce energy yield and can create multiple power maxima and hot spots. Characterization through I–V tracing, thermal imaging, electroluminescence, insulation testing, and performance-ratio analysis enables systematic diagnosis. Degradation arises through optical, electrical, mechanical, thermal, moisture, and voltage-related mechanisms. Certification tests, warranties, supplier quality systems, and field evidence must be interpreted together.

Reliable PV engineering is not limited to selecting a high-rated module. It requires sound array configuration, environmental assessment, protection, measurement, maintenance, safety, and lifecycle evaluation.

Key Terms

Photovoltaic cell: Semiconductor device that converts light into electrical energy.

Module: Encapsulated and electrically interconnected group of PV cells.

String: Series-connected group of PV modules.

Array: One or more electrically interconnected PV strings.

I–V curve: Relationship between PV current and terminal voltage.

P–V curve: Relationship between PV power and terminal voltage.

Short-circuit current: Current delivered when terminal voltage is zero.

Open-circuit voltage: Terminal voltage when output current is zero.

Maximum power point: Operating point at which P = VI is greatest.

Fill factor: Ratio of maximum power to the product of open-circuit voltage and short-circuit current.

Standard Test Conditions: Reference conditions of 1000 W/m², 25 °C cell temperature, and defined spectrum.

MPPT: Control method that seeks the array’s maximum-power operating point.

Bypass diode: Antiparallel diode that provides a current path around a shaded cell group.

Blocking diode: Series diode that limits unwanted reverse current.

Mismatch: Loss caused by unequal electrical or environmental conditions among connected devices.

Hot spot: Localized overheating caused commonly by reverse-biased shaded or defective cells.

Performance ratio: Irradiation-normalized measure of delivered system energy.

Degradation: Reduction in performance with time.

Potential-induced degradation: Voltage- and environment-related loss of PV performance.

Design qualification: Standardized testing intended to demonstrate module durability and safety under specified conditions.

Review Questions

Short Answer Questions

1. Distinguish V_oc from V_mp.
2. Why does increasing irradiance mainly increase PV current?
3. State the purpose of a bypass diode.
4. Define mismatch in a PV array.
5. Why is STC power not the same as continuous outdoor power?

Long Answer Questions

1. Explain the operation of a PV module using its I–V and P–V characteristics, including the significance of the maximum power point.
2. Describe how temperature and irradiance affect module voltage, current, and power.
3. Explain the design checks required when selecting the number of modules in a string.
4. Discuss the principal degradation and failure mechanisms in crystalline-silicon PV modules.
5. Explain how I–V tracing, infrared thermography, and performance-ratio analysis can be combined for fault diagnosis.

Analytical / Application Questions

1. A module has V_oc = 48 V at 25 °C and a voltage coefficient of −0.30%/°C. Estimate its open-circuit voltage at −15 °C using a linear approximation, and explain why the result must be checked against the inverter’s maximum DC voltage.
2. A 100 kWdc plant produces 142,000 kWh during a period with plane-of-array irradiation of 350 kWh/m². Calculate its performance ratio using G_ref = 1 kW/m², and identify two losses that may be represented in the result.
3. A string shows normal voltage but substantially reduced current, while neighboring strings are normal. Develop a diagnostic sequence that distinguishes soiling, partial shading, connector resistance, and module failure.

Multiple Choice Questions with Answers

Question 1

Which quantity is measured when the terminals of a PV module are open and no current flows?

A. Short-circuit current

B. Open-circuit voltage

C. Maximum-power current

D. Fill factor

Correct Answer: B. Open-circuit voltage

Question 2

For identical modules connected in series, which quantity primarily increases?

A. Array voltage

B. Array current

C. Irradiance

D. Module temperature

Correct Answer: A. Array voltage

Question 3

What is the principal function of a bypass diode in a PV module?

A. Raise the module open-circuit voltage

B. Prevent all shading losses

C. Provide an alternate path around a shaded cell group

D. Convert DC power to AC power

Correct Answer: C. Provide an alternate path around a shaded cell group

Question 4

Under Standard Test Conditions, the reference irradiance is:

A. 100 W/m²

B. 500 W/m²

C. 800 W/m²

D. 1000 W/m²

Correct Answer: D. 1000 W/m²

Question 5

A PV module has V_oc = 50 V and I_sc = 10 A. If V_mp = 40 V and I_mp = 9 A, its fill factor is:

A. 0.72

B. 0.80

C. 0.90

D. 1.25

Correct Answer: B. 0.80

Question 6

What is the usual effect of increasing cell temperature on crystalline-silicon module power?

A. Power increases substantially

B. Power remains exactly constant

C. Power generally decreases

D. Current and voltage both become zero

Correct Answer: C. Power generally decreases

Question 7

In a series-connected PV string, a strongly shaded module most directly limits:

A. The string current

B. The grid frequency

C. The inverter AC voltage

D. The module frame mass

Correct Answer: A. The string current

Question 8

A performance ratio of 0.85 most appropriately means that:

A. The modules are 85% electrically efficient

B. The system delivered 85% of its irradiation-normalized reference yield

C. The array operates at 85 °C

D. The inverter is rated at 85 kW

Correct Answer: B. The system delivered 85% of its irradiation-normalized reference yield

Question 9

Which condition is most directly associated with a hot spot?

A. A shaded or defective cell driven into reverse bias

B. A module operating at open circuit in darkness

C. A clean module at uniform irradiance

D. A correctly sized AC transformer

Correct Answer: A. A shaded or defective cell driven into reverse bias

Question 10

Which standard is primarily associated with PV module safety qualification?

A. IEC 61730

B. IEC 60034

C. IEEE 802.11

D. ISO 9001 only

Correct Answer: A. IEC 61730