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WorksheetsProfessional Solar Energy Installations training Examination
Total questions: 60
Worksheet time: 2hrs 43mins
A PV module has Pmax 288 W, Voc 40.0 V, Isc 9.5 A. At STC when loaded, Vmp = 32 V and Imp = 9.0 A. You must design an array of 6 modules in series and 4 strings in parallel. What is the expected system kWp, array voltage, and current at STC?
5.76 kWp, 240 V, 38 A
5.76 kWp, 240 V, 38 A
6.912 kWp, 192 V, 9 A
6.912 kWp, 192 V, 36 A
7.0 kWp, 192 V, 36 A
For a grid‑tied system, the designer needs 40 kWh/day with average irradiance 5 peak sun hours and must account for 25% total losses. What PV array STC power is required?
13.333 kW
8 kW
9.411 kW
133.33 kW
10.667 kW
A rooftop 5 kW STC system has a performance ratio (PR) of 0.78. If the annual reference insolation is 1500 kWh/kWp, estimate the annual energy yield.
585 kWh
7500 kWh
5850 kWh
6750 kWh
7.5 kWh
A system uses microinverters per module. Shading reduces a single module to 50% of its MPP. Compared with a string inverter under the same shading, what happens to system performance?
Microinverters suffer more loss.
Microinverters limit the loss to that module only; a string inverter sees the whole string loss.
Both systems are identical.
Microinverters cut the whole system to 50%.
None of the above.
A PV array with Voc per module = 48 V is connected 10 in series, with 8 strings in parallel. The maximum possible string Isc at STC is 9.0 A. What is the maximum short‑circuit current that the combiner fuse must handle instantaneously (nearest value)?
72 A
90 A
9 A
72 mA
8 A
When designing a utility‑scale PV array for minimal degradation over time, which module characteristic should most influence orientation, stringing, and shading mitigation decisions?
Nameplate STC efficiency
Low‑light performance
Temperature coefficient of power and voltage
Aesthetics of module frames
Manufacturer warranty length
A mini‑grid with 30 kWh daily load requires 2 days of autonomy. If allowable depth of discharge (DoD) is 80%, estimate the total battery bank capacity at 48 V (approximate).
1300 Ah
1560 Ah
900 Ah
800 Ah
2000 Ah
In hot, humid tropical climates, which PV mounting decision will most improve long‑term yield and reduce BOS maintenance?
Minimizing roof ventilation under modules
Installing modules flush to roof to reduce wind uplift
Painting module backs to reflect heat
Using ventilated elevated mounts with corrosion‑resistant fasteners
Using only glass‑back modules
When integrating bifacial modules into a mixed plant, what is the primary planning consideration to preserve expected bifacial gain?
Install at the tallest possible tilt without regard to land use.
Ignore albedo and ground conditions; bifacial gains are stable.
Model and control ground albedo, row spacing, and elevation to manage rear irradiance.
Place bifacial modules only east‑west.
Use bifacial modules only on single‑axis trackers.
A 48 V solar charge controller must handle an array of 4 parallel strings, each with Imp = 9.5 A. With a 25% safety margin, what minimum controller current rating should be selected?
38 A
45 A
50 A
60 A
80 A
For a PV plant attempting to achieve the highest capacity factor in a region with significant seasonal sun-angle variation, which high-level strategy is optimal?
Fix all arrays at local latitude tilt and ignore seasonal variance.
Use tracking systems (single or dual axis) only if LCOE gains justify complexity and added O&M risk.
Use only east–west mounted panels in a dense fixed array.
Mount panels vertically to reduce tilt losses.
Oversize inverters massively.
A 5 kW inverter runs at 85% efficiency under partial load. If DC input power is 4.2 kW, what is the actual AC output?
3.57 kW
4.0 kW
4.2 kW
3.8 kW
3.5 kW
A system requires a 48 V nominal battery bank to supply 4 kW continuously for 8 hours at 80% depth of discharge (DoD). Neglecting efficiency, what approximate Ah capacity is required?
667 Ah
500 Ah
1000 Ah
416 Ah
833 Ah
Using a lead-acid battery with round-trip efficiency of 85% and the bank sizing from the previous scenario (ignoring efficiency gave 667 Ah), what real Ah must be installed to deliver the required usable energy?
1000 Ah
667 Ah
900 Ah
785 Ah
720 Ah
A designer wants 10 kWh usable daily from a Li-ion bank with 90% DoD allowed and battery efficiency 95%. What nominal energy capacity must the bank have?
10.0 kWh
11.7 kWh
12.5 kWh
9.5 kWh
13.2 kWh
A BMS limits charge current to C/2 for a 48 V, 200 Ah battery. What is the maximum charge power?
9.6 kW
2.4 kW
4.8 kW
480 W
48 kW
Two 12 V, 100 Ah batteries in parallel supply a load drawing 50 A. Assuming equal sharing, what is the current per battery and the time to reach 50% DoD?
50 A total; 2 h
50 A each; 1 h
12.5 A; 4 h
25 A each; 4 h
25 A each; 2 h
For autonomy of 2 days with a daily draw of 20 kWh and allowable battery DoD of 80%, what total bank energy is required?
50 kWh
40 kWh
25 kWh
80 kWh
100 kWh
A lead-acid battery self-discharges at 3% per month. If stored at 50% state of charge (SOC) for 6 months, approximately what SOC remains, ignoring other effects?
50%
32%
40%
18%
0%
A 48 V nominal battery bank shows a voltage drop of 2 V when a 200 A load is applied. Estimate the internal resistance of the bank.
10 mΩ
1 Ω
0.1 Ω
0.02 Ω
0.001 Ω
A DC-coupled inverter charges a battery with 95% efficiency. If PV provides 5 kW for 3 hours into the battery, how much stored energy is added?
10 kWh
15 kWh
13.5 kWh
15.79 kWh
14.25 kWh
For a 24 V system, a designer uses 6 × 3.2 V Li‑ion cells in series. Each cell is 100 Ah. What is the nominal bank energy (kWh)?
2.4 kWh
24 kWh
0.24 kWh
12 kWh
4.8 kWh
A 5 MWh lithium‑ion BESS has these efficiencies during charge/discharge: inverter 96%, DC/DC converter 97%, battery cell 98%. What is the overall round‑trip efficiency?
88%
90%
91%
92%
94%
A 2.5 MWh containerized BESS shows occasional 20–40 kHz high‑frequency noise spikes on the DC bus voltage. What condition does this most likely indicate?
Cell balancing activity
Normal inverter switching ripple
Harmonics from grid voltage fluctuations
Arc fault due to loose terminal or cable degradation
Internal BMS communication interference
A 10 MWh LFP BESS container includes smoke, temperature, and hydrogen sensors integrated via the BMS. If gas concentration exceeds 4% H2, what should occur first?
Activate fire suppression system
Isolate power electronics and open air dampers
Shut down ventilation fans
Increase inverter cooling speed
Trigger audible alarm only
A 48 V battery feeds an inverter to 230 V AC. For 4 kW AC output and inverter efficiency 94%, what DC current is drawn from the battery?
88.7 A
80 A
17.4 A
200 A
48 A
An off‑grid inverter is rated 6 kW continuous with surge capacity 12 kW for 10 s. A motor with locked‑rotor draws 8× rated running current for 0.5 s, then falls to 3× for 2 s, then 1.5× for 0.1 s. The inverter overload curve allows 10 kW for 1 s. Is the starting sequence safe? Choose the best option.
Not safe — initial 8× likely exceeds surge capacity.
Safe — surge within 12 kW for 10 s.
Safe — because average below.
Safe only if power factor low.
Not safe — must use soft‑start.
An inverter with DC input 600 V and MPPT range 200–500 V is connected to a PV string with Vmp = 520 V. What is the expected behavior?
Not optimal; inverter may not start MPPT; must reconfigure.
Perfect operation.
MPPT extends to 600 V automatically.
System will shut down permanently.
Nothing happens.
A hybrid inverter accepts AC charge current from a single‑phase generator rated 50 A at 230 V. Neglecting conversion losses, what maximum battery‑charging power is available?
11.5 kW
5 kW
23 kW
1.15 kW
0.5 kW
Inverter idle consumption is 20 W. With average night hours of 10 h, what is the yearly idle energy (kWh)?
7.3 kWh
73 kWh
730 kWh
20 kWh
200 kWh
A battery‑backed inverter must supply an inductive load with PF = 0.6 lagging and apparent power 10 kVA. What real power and minimum inverter VA rating are required?
6 kW; 6 kVA inverter
6 kW; 10 kVA inverter
10 kW; 6 kVA inverter
16 kW; 10 kVA inverter
6 kW; 16 kVA inverter
A three-phase inverter is feeding unbalanced loads: phase A = 20 kW, phase B = 10 kW, phase C = 0 kW. The inverter enforces a balanced current limit. Which outcome is most likely?
It will distribute power equally to all phases.
It will supply all loads without issue.
It may trip for imbalance and must be derated.
It will send all power to phase A.
None of the above.
A 5 kVA, 48 V inverter operates at 85% efficiency while supplying a 4.25 kW AC load. Estimate the DC input current drawn from the battery bank.
78 A
86 A
104 A
92 A
110 A
An inverter manufacturer recommends a DC:AC ratio of 1.3 for a site in the southern latitudes. For a 100 kWac inverter, what is the recommended DC array size?
130 kW
77 kW
100 kW
200 kW
113 kW
A customer reports that a fan hums loudly and a refrigerator’s compressor overheats when powered by an inverter. Which inverter feature is most likely missing?
Low idle current draw
Pure sine wave output
Low battery protection
PWM charging
High surge rating
An inverter rated 3 kVA at power factor 0.8 supplies 1.8 kW, including a refrigerator with a starting surge current 3× its running current. If a second refrigerator starts simultaneously, what is the likely outcome?
Inverter continues normally.
Only one fridge starts; the second waits automatically.
Inverter trips on overload.
Inverter reduces output voltage automatically.
Surge current does not affect the inverter.
An inverter delivers 1.5 kW at 90% efficiency. What DC input power does it draw from the battery?
1350 W
1450 W
1500 W
1667 W
1700 W
Two 5 kVA (48 V) hybrid inverters, each with 4 kW continuous AC output, operate in parallel to supply a total 7 kW load. If one inverter fails, what happens?
The load continues normally.
Both inverters shut down immediately.
The remaining inverter carries 7 kW temporarily.
The remaining inverter shuts down on overload.
The load automatically reduces.
A DC combiner box has 8 strings, each with Isc = 10 A. What is the minimum fuse rating per string to carry Isc while avoiding nuisance blowing under 1.25× derating? Choose the nearest value.
15 A
12.5 A
10 A
20 A
5 A
During maintenance, equalization is activated at 15.5 V per 12 V block for 1 hour. What is the primary purpose of equalization in this context?
Rapidly charge the battery
Increase electrolyte evaporation
Balance cell voltages and reduce sulfation
Boost inverter efficiency
Cool the battery
A 12 V, 200 Ah battery measures 12.2 V at rest (no load and no charge for 4 hours). What is the approximate State of Charge (SOC)?
25%
40%
50%
60%
80%
A charge controller limits battery current to 0.25 C for a 200 Ah bank. What is the maximum charge power at 48 V?
4.8 kW
2.4 kW
1.2 kW
24 kW
A system uses an MPPT controller with 98% efficiency. If the PV array produces 5.5 kW at MPP, approximately how much power does the battery receive?
6 kW
5.5 kW
5.0 kW
4.5 kW
5.39 kW
A controller supports two MPPT inputs: MPPT1 max 3000 W and MPPT2 max 2000 W. If PV arrays provide 2500 W on MPPT1 and 2200 W on MPPT2, what happens?
MPPT1 accepts 2500 W; MPPT2 accepts 2000 W and shares remaining 200 W with MPPT1.
Both accept full power.
Both clip.
MPPT1 accepts 2500 W; MPPT2 clips at 2000 W dropping 200 W.
System shuts down.
A system’s expected degradation rate is 0.7% per year. After 15 years, what is the approximate relative performance?
90%
70%
50%
100%
10%
A designer oversizes the inverter by 20% relative to an expected peak household load of 4.5 kW. What inverter rating should be chosen?
10 kW
4.5 kW
6 kW
3.6 kW
5.4 kW
In Nigeria (latitude approximately 6°–10° N), which tilt generally gives the best annual solar energy yield for a fixed rooftop system?
0° (flat)
5° facing north
10° facing south
45° facing south
Vertical mount
When connecting PV modules in parallel, what is most important for safety?
All modules must have same current rating
Use separate fuses for each string
Use thicker cables only
Connect directly to battery terminals
Use any available connectors
A 400 W panel produces only 80 W at midday under clear skies. What is the most likely cause?
Low sunlight
Panel degradation
Partial shading or a loose connection
Temperature too low
Oversized inverter
A solar installer reports that a connector is melting. What is the most likely reason?
Too much voltage
Reverse polarity
Loose terminal crimp causing high-resistance heating
Water inside connector
Overcharging battery
A 5 kVA inverter powers a borehole pump rated 3.5 kW with a surge of 7 kW. What is the most probable outcome?
Pump runs normally
Inverter trips or restarts
Solar array burns
Battery overcharges
Voltage rises above safe limit
Which inverter type is best suited for running heavy inductive loads such as compressors or welders?
High frequency inverter
Transformerless inverter
Low frequency inverter
String inverter
Micro-inverter
You design a 3 kW PV array using eight 375 W modules. Each module is 40 V, 9.4 A. You want roughly 80 V to charge a 48 V system through an MPPT. How should the array be configured?
8 in series
2 strings of 4 in series (2S4P)
4 strings of 2 in series (4S2P)
All 8 in parallel
3 strings of 3 in series (3S3P)
A 550 W PV module has dimensions 2.3 m × 1.1 m. What is the module efficiency at STC (1000 W/m^2)?
18.7%
20.1%
21.7%
22.5%
24.0%
A panel rated 21% efficiency and 2.0 squared-meter area receives 950 W/squared-meter of solar irradiance. What is its instantaneous power output?
355 W
380 W
440 W
420 W
399 W
Why should DC cables between panels and controller be run in conduit or trunking?
For aesthetics
To reduce voltage
To protect from UV, abrasion, and rodents
To increase power output
To aid lightning flow
A 24 V, 200 Ah battery runs a 1 kW load through an inverter at 90% efficiency. What is the approximate runtime?
2 h
3 h
4 h
5 h
6 h
What is the recommended charging current for a 12 V 200 Ah deep‑cycle battery?
10 A
20 A
40 A
60 A
80 A
During equalization of a 48 V flooded lead‑acid bank, one 12 V battery rises to 16.2 V while others are around 15.2 V. What is the most likely cause?
That battery is newer and stronger
That battery has higher internal resistance or lower capacity
Charger fault
Normal variation during charge
Temperature compensation error
An installer notices heating at battery terminals. What’s the most likely cause?
High electrolyte level
Overvoltage
Loose terminal or undersized cable
Battery full
Inverter fault
