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WorksheetsPV System Design and Calculation Worksheet
Total questions: 60
Worksheet time: 2hrs 46mins
A PV module has a Pmax of 288W, 40.0V open circuit, 9.5A short circuit, when connected to loads, the voltage and current at production are 32V and 9.0A respectively at STC. As the design engineer in charge of the project, your design prompts you to plan an array of 6 modules and 4 strings. What is the expected system KWp, maximum power array voltage and current of system at STC?
5.76KWp, 240V, 38A
5.76KWp, 240V, 38A
6.912KWp, 192V, 9A
6.912KWp, 192V, 36A
7Kwp, 192V, 36A
For a grid-tied system, a designer wants daily energy 40 kWh and average irradiance 5 peak sun hours. Accounting system losses 25% total, what PV array STC power is needed?
13.333 kW
8 kW
9.411 kW
133.33 kW
10.667 kW
A rooftop 5 kW STC system has performance ratio (PR) of 0.78. If annual reference insolation corresponds to 1500 kWh/KWp, estimate annual yield (kWh).
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. How does system performance compare to string inverter with same shading?
Microinverters suffer more loss.
Microinverters limit loss to that module only; string sees whole string loss.
Both identical.
Microinverters cut whole system to 50%.
None of the above.
A PV array with Voc per module 48 V is connected 10 in series, 8 strings parallel. Maximum possible string Isc at STC 9.0 A. What is maximum short-circuit current that the combiner fuse must handle instantaneously (select nearest)?
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 array layout decisions (orientation, stringing, and shading mitigation)?
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 autonomy and DoD = 80%. What is the approximate total battery bank capacity (at 48 V)?
1500 Ah
1200 Ah
800 Ah
625 Ah
In hot, humid tropical climates, which PV mounting decision will most improve long-term yield and reduce BOS (balance-of-system) 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 in single-axis trackers.
A 48 V solar charge controller must handle an array of 4 parallel strings (Imp = 9.5 A per string). What minimum controller current rating should be used, account for safety margin of 25%?
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, what is the optimal high-level strategy?
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. What is the actual AC output if DC input power is 4.2 kW?
3.57 kW
4.0 kW
4.2 kW
3.8 kW
3.5 kW
A system needs 48 V nominal battery bank to supply 4 kW continuous for 8 hours at 80% DOD. What Ah capacity (approx) is required (neglect efficiency)?
667 Ah
500 Ah
1000 Ah
416 Ah
833 Ah
Using lead-acid battery round-trip efficiency 85% and the bank in Q13, what real Ah must be installed to account for efficiency to deliver required usable energy?
1000 Ah
800 Ah
900 Ah
1100 Ah
1200 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 (kWh)?
10.0 kWh
11.7 kWh
12.5 kWh
9.5 kWh
13.2 kWh
A BMS limits charge current to C/2 for 48 V 200 Ah battery. What is 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 current per battery and time to 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 2 days with daily draw 20 kWh and battery DoD 80%, what bank energy required?
50 kWh
32 kWh
40 kWh
60 kWh
A lead-acid battery self-discharge 3%/month. If stored at 50% SOC for 6 months, approximate SOC remaining ignoring other effects?
50%
32%
40%
18%
0%
A battery bank of 48 V nominal is monitored; voltage drops 2 V under a 200 A load. Estimate internal resistance of bank.
10 mΩ
1 Ω
0.1 Ω
0.02 Ω
0.001 Ω
A DC-coupled inverter charges battery with 95% efficiency. If PV provides 5 kW at noon for 3 hours into battery, how much stored energy added (kWh)?
10 kWh
15 kWh
13.5 kWh
15.79 kWh
14.25 kWh
For a 24 V system, designer wants to use 6 × 3.2 V Li-ion cells in series. If each cell capacity 100 Ah, what is nominal bank energy (kWh)?
2.4 Kwh
24 kWh
0.24 kWh
12 kWh
4.8 kWh
A 5 MWh lithium-ion BESS records the following system-level losses during charge/discharge: Inverter efficiency = 96 % DC/DC converter efficiency = 97 % Battery cell efficiency = 98 % What is the overall round-trip efficiency of the system?
A. 88 %
B. 90 %
C. 91 %
D. 92 %
E. 94 %
A 2.5 MWh containerized BESS experiences occasional high-frequency noise spikes (20–40 kHz) on 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 sensors, temperature probes, 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 into 230 V AC. For 4 kW AC output and inverter 94% efficient, what DC current drawn from battery?
88.7 A
80 A
17.4 A
200 A
48 A
An off-grid inverter 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 runs at 1.5× for 0.1 s. If inverter overload curve allows 10 kW for 1 s, is starting sequence safe?
Not safe — initial 8× likely exceeds surge capacity.
Safe — surge within 12 kW for 10s.
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 will operate with a PV string Vmp 520 V. What is the expected behavior?
The inverter will not track maximum power point and may not operate efficiently.
The inverter will operate at maximum efficiency.
The inverter will shut down due to overvoltage.
The inverter will operate normally within the MPPT range.
A hybrid inverter accepts AC charge current from generator rated 50 A at 230 V single-phase. What maximum battery charging power is available (neglect conversion losses)?
11.5 kW
5 kW
23 kW
1.15 kW
0.5 kW
Inverter idle consumption is 20 W. For a system with average night hours 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 required inverter VA rating at minimum?
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 feeding unbalanced loads sees phase A 20 kW, phase B 10 kW, phase C 0 kW. If inverter has balanced current limit, which is correct statement?
It will distribute equally.
It will supply all loads fine.
It may trip for imbalance — must derate.
It will send all power to phase A.
None.
A 5 kVA 48 V inverter is operating at 85% efficiency, supplying 4.25 kW AC load. Determine the DC input current drawn from the battery bank.
78 A
86 A
104 A
92 A
110 A
An inverter manufacturer recommends DC:AC ratio of 1.3 for southern latitude. For 100 kW inverter, recommended the DC array size?
130 kW
77 kW
100 kW
200 kW
113 kW
A customer complains that his fan hums loudly and his fridge 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
An inverter rated 3 kVA (with a power factor of 0.8) powers a load of 1.8 kW including a refrigerator with starting surge 3× its running current. What happens if a second fridge starts at the same time?
Inverter will continue normally.
Only one fridge will start; the second will wait automatically.
Inverter may trip on overload.
Inverter will reduce its voltage automatically.
Nothing—surge current doesn’t affect inverter.
An inverter operates at 90% efficiency when delivering 1.5 kW. What input DC power does it draw from the battery?
1350 W
1450 W
1500 W
1667 W
1700 W
Two 5 kVA hybrid inverters (48 V) are installed in parallel to supply a total 7 kW load. Each inverter has max AC output of 4 kW continuous. If one inverter fails, what happens?
Load continues normally
Both shut down immediately
Remaining inverter carries 7 kW temporarily
Remaining inverter shuts down on overload
Load reduces automatically
A DC combiner box has 8 strings each Isc=10 A. What minimum fuse rating per string to carry Isc and avoid nuisance blow under 1.25× derating? Choose nearest.
10 A
12 A
13 A
15 A
During maintenance, a technician activates equalization at 15.5 V per 12 V block for 1 hour. What is the primary purpose of this process?
Rapidly charge the battery
Increase electrolyte evaporation
Balance cell voltage and reduce sulfation
Boost inverter efficiency
Cool the battery
A 12 V 200 Ah battery measures 12.2 V at rest (no load or 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 200 Ah bank. What max charge power at 48 V?
4.8 kW
2.4 kW
1.2 kW
24 kW
A system uses a MPPT controller with 98% efficiency. PV produces 5.5 kW MPP; battery receives how much?
6 kW
5.5 kW
5.0 kW
4.5 kW
5.39 kW
A controller supports two MPPT inputs: MPPT1 3000 W max, MPPT2 2000 W max. If PV arrays provide 2500 W and 2200 W respectively, what happens?
MPPT1 accepts 2500 W Comfortably; MPPT2 will accept 2000 W and distribute the remaining 200 W with MPPT1.
Both accept full power.
Both clip.
MPPT1 accepts 2500 W comfortably; MPPT2 will clip at 2000 W dropping 200 W.
System shuts down.
A PV system's expected degradation rate is 0.7%/yr. After 15 years, the performance relative to its initial value is ?(approximate your answer):
90%
70%
50%
100%
A designer chooses to oversize inverter by 20% relative to expected peak household load 4.5 kW. The Inverter rating chosen should be?
10 kW
4.5 kW
6 kW
3.6 kW
5.4 kW
In Nigeria (latitude ~6°–10° N), which tilt 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. Which is the most likely cause?
Low sunlight
Panel degradation
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 surge of 7 kW. What’s the 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 (e.g., compressors, welders)?
High frequency inverter
Transformerless inverter
Low frequency inverter
String inverter
Micro-inverter
You design a 3 kW PV array (8 × 375 W modules). Each module gives 40 V, 9.4 A. You want ~80 V to charge a 48 V system through an MPPT. How should the array be configured?
(a)
A 550 W PV module has dimensions 2.3 m × 1.1 m. What is the module efficiency at standard test conditions (STC = 1000 W/m²)?
18.7 %
20.1 %
21.7 %
22.5 %
24.0 %
A panel rated 21% efficiency and 2.0 m² area receives 950 W/m² 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 beauty
To reduce voltage
To protect from UV, abrasion, and rodents
To increase power output
A 24 V, 200 Ah battery runs a 1 kW load through an inverter at 90% efficiency. 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 remain 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
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
