Advance Diploma Solar Semester Two Paper 2 Exam Section C

SECTION C – Long Answer Question Bank

50 Questions with Answers (5–6 Lines Each)

(Advanced Diploma Solar Technology – Semester 2 | Paper 2)

1. Explain the working principle of a solar photovoltaic system.

Answer:
A solar photovoltaic system converts sunlight directly into electricity using solar cells. When sunlight falls on the semiconductor material, electrons are released and create DC current. Multiple cells form modules and arrays. The DC power is sent to an inverter, which converts it into AC power. This AC power is used by loads or supplied to the grid. PV systems are clean and renewable.

2. Describe the main components of a solar power plant.

Answer:
The major components are solar modules, mounting structure, inverter, cables, combiner boxes, ACDB/DCDB, earthing system, and monitoring unit. Modules generate DC electricity from sunlight. The structure supports modules safely. Inverters convert DC to AC. Protection devices ensure safe operation. Monitoring systems track plant performance.

3. Explain the difference between on-grid, off-grid, and hybrid solar systems.

Answer:
An on-grid system is connected to the utility grid and usually works without batteries. An off-grid system works independently and uses batteries for backup. A hybrid system combines solar panels, batteries, and grid supply. On-grid systems are economical, while off-grid systems suit remote areas. Hybrid systems provide backup and energy savings.

4. Explain net metering and its advantages.

Answer:
Net metering allows consumers to export excess solar electricity to the utility grid. A bidirectional meter records imported and exported units. Consumers receive bill credits for surplus energy. It reduces electricity bills and improves solar investment returns. It also avoids the need for large battery storage. Net metering promotes rooftop solar adoption.

5. Describe the role of a solar inverter.

Answer:
A solar inverter converts DC electricity generated by panels into AC electricity used by appliances and the grid. It also synchronizes output with grid voltage and frequency. Modern inverters include MPPT, fault protection, and monitoring features. They improve system efficiency and safety. Inverters are one of the most critical components of PV systems.

6. Explain why site assessment is important before solar installation.

Answer:
Site assessment checks the technical suitability of a location for solar installation. It includes shading analysis, roof strength, land condition, grid availability, and sunlight potential. It helps determine plant capacity and design. Proper assessment prevents future technical issues. It also improves generation and project feasibility.

7. Discuss the importance of panel orientation and tilt angle.

Answer:
Correct panel orientation and tilt angle maximize sunlight absorption. In the Northern Hemisphere, south-facing panels generally perform best. Tilt angle depends on site latitude and local climate. Incorrect angle reduces energy generation. Proper design improves annual yield. Seasonal adjustments may further improve output in some systems.

8. Explain the construction and use of mounting structures.

Answer:
Mounting structures are metal frameworks used to support solar panels on rooftops or ground. They are commonly made of GI, aluminium, or steel. Structures must withstand wind load, rain, and corrosion. Proper alignment ensures good panel placement. Strong structures improve safety and plant life. They also allow maintenance access.

9. Describe the function of a combiner box in a PV plant.

Answer:
A combiner box combines the output of multiple solar strings into a single DC output. It contains fuses, SPD, disconnect switches, and terminals. This reduces wiring complexity and improves safety. It allows easier maintenance and troubleshooting. Combiner boxes are commonly used in medium and large plants.

10. Explain the importance of earthing in solar systems.

Answer:
Earthing provides a low-resistance path for leakage and fault currents. It protects people from electric shock and prevents equipment damage. Structures, inverter bodies, and panels are properly grounded. Earthing also helps in lightning protection. A well-designed earthing system increases plant safety and reliability.

11. Explain the purpose of Surge Protection Devices (SPD).

Answer:
SPDs protect solar equipment from sudden voltage surges caused by lightning or switching operations. These surges can damage inverters and electronics. SPDs divert excess voltage safely to ground. They are installed on both AC and DC sides. Their use improves equipment life and reduces downtime.

12. Explain preventive maintenance of a solar plant.

Answer:
Preventive maintenance includes regular inspection and servicing to avoid faults. It involves cleaning modules, checking cables, tightening terminals, inspecting earthing, and inverter checks. It increases energy generation and reduces breakdowns. Scheduled maintenance lowers repair costs. It also extends system life and improves safety.

13. Describe the process of cleaning solar modules.

Answer:
Solar modules are cleaned using soft water, cloth, or approved cleaning tools. Dust, bird droppings, and dirt should be removed carefully. Cleaning is usually done during morning or evening hours. Abrasive materials must be avoided. Regular cleaning improves sunlight absorption. This increases plant output.

14. Explain thermal imaging and its use in solar plants.

Answer:
Thermal imaging uses infrared cameras to identify hot spots in modules, cables, and connections. Hot spots may indicate loose terminals, damaged cells, or faults. It helps in preventive maintenance. The test is fast and non-contact. Early detection reduces failures and energy loss.

15. Explain performance ratio in solar plants.

Answer:
Performance ratio (PR) compares actual energy generated with theoretical expected energy. It indicates how efficiently the system is performing after losses. PR considers temperature, inverter losses, dust, and wiring losses. Higher PR means better operation. It is an important performance indicator for PV plants.

16. Describe the steps involved in commissioning a solar plant.

Answer:
Commissioning starts after installation completion. It includes visual inspection, polarity checks, insulation tests, grounding tests, inverter startup, and performance verification. Safety devices are also checked. If all tests are satisfactory, the system is energized. Commissioning ensures readiness for commercial operation.

17. Explain the importance of cable sizing in solar projects.

Answer:
Correct cable sizing reduces voltage drop and overheating. Undersized cables waste energy and may become unsafe. Cable selection depends on current, distance, temperature, and installation method. Proper sizing improves efficiency and reliability. It also ensures compliance with standards.

18. Explain DC and AC sides of a solar system.

Answer:
The DC side includes modules, strings, combiner boxes, and cables up to the inverter input. Solar panels generate DC power. The inverter converts this into AC power. The AC side includes inverter output, ACDB, loads, transformer, and grid connection. Both sides need proper protection.

19. Describe the role of monitoring systems in solar plants.

Answer:
Monitoring systems collect real-time data such as voltage, current, energy generation, and inverter status. They help detect faults quickly. Remote monitoring reduces manual inspection effort. Historical data supports performance analysis. Monitoring improves uptime and maintenance planning.

20. Explain the concept of load profile study.

Answer:
Load profile study records electricity demand over time, usually hourly or daily. It identifies peak load and consumption patterns. This helps size solar systems and batteries properly. It improves self-consumption planning. It is very useful for commercial and industrial consumers.

21. Explain the difference between string inverter and microinverter.

Answer:
A string inverter handles power from multiple modules connected in series. It is economical and common in many plants. A microinverter is installed on each module individually. It performs better under shading conditions. Microinverters offer module-level monitoring but cost more.

22. Discuss the importance of PPE in solar installations.

Answer:
PPE includes helmets, gloves, shoes, goggles, and safety harnesses. It protects workers from falls, electric shock, cuts, and injuries. PPE is essential during rooftop and construction work. It reduces accidents and legal risks. Safety culture improves project quality.

23. Explain roof load capacity test for rooftop systems.

Answer:
A roof load capacity test checks whether the building roof can support panel and structure weight. Engineers inspect materials, age, and structural strength. Weak roofs may require reinforcement. This prevents cracks and failures. It is a necessary pre-installation step.

24. Explain soil investigation for ground-mounted solar plants.

Answer:
Soil investigation determines soil type, strength, moisture, and bearing capacity. It helps design pile foundations and supports. Poor soil may need deeper foundations. It prevents settlement and structural instability. This study is important for large solar parks.

25. Explain the significance of Gantt chart in project management.

Answer:
A Gantt chart shows project tasks against time in bar chart form. It helps track start dates, finish dates, and progress. Dependencies between activities can be managed. Delays are identified early. It is widely used in solar EPC execution.

26. Explain Bill of Materials (BOM) in solar projects.

Answer:
BOM is a detailed list of all materials required for the project. It includes modules, inverter, structures, cables, breakers, and accessories. Quantities and specifications are clearly mentioned. BOM helps procurement and budgeting. It prevents shortages and planning errors.

27. Explain procurement process in solar projects.

Answer:
Procurement includes vendor selection, quotation comparison, ordering, inspection, and delivery of materials. Good procurement ensures quality equipment at the right cost. Timely delivery avoids project delays. Contracts and warranties are also managed. It is vital for successful execution.

28. Explain ROI in solar investments.

Answer:
ROI means Return on Investment. It measures how much financial benefit is earned from the solar system compared with total cost. Savings on electricity bills improve ROI. Subsidies and net metering also help. Shorter payback period means better investment.

29. Explain why solar energy is environmentally beneficial.

Answer:
Solar energy produces electricity without burning fossil fuels. It reduces greenhouse gas emissions and air pollution. It also lowers dependence on coal and diesel. Water use is lower than many conventional plants. It supports sustainable development goals.

30. Explain bifacial solar panels and their benefits.

Answer:
Bifacial panels generate electricity from both front and rear surfaces. The rear side uses reflected sunlight from the ground. This increases total energy generation. They are useful in open areas with reflective surfaces. They can improve project returns.