SECTION C – Descriptive / Long Answer / Numerical Questions

(25 Questions)

1. Explain the need for renewable energy.

Model Answer: Renewable energy is needed because conventional sources such as coal, diesel, and gas are limited and polluting. Renewable sources like solar and wind reduce greenhouse gas emissions, improve energy security, support sustainable development, and help meet rising energy demand. The notes also highlight carbon emission concerns and the importance of cleaner power generation.

2. Explain the basic concept of current, voltage, and resistance.

Model Answer: Current is the flow of electrons through a conductor and is measured in amperes. Voltage is the force or potential difference that drives the current. Resistance is the opposition offered to current flow by a material, measured in ohms. Together, they define the behavior of electric circuits and are essential in solar system design.

3. Describe the working principle of a solar cell.

Model Answer: A solar cell works on the photovoltaic effect. When light falls on the semiconductor, photons transfer energy to electrons. This creates electron-hole pairs. Due to the internal electric field in the cell, electrons and holes are separated, producing a potential difference. When an external circuit is connected, current flows.

4. Explain the advantages and limitations of solar PV technology.

Model Answer: Advantages include no moving parts, low maintenance, satisfactory operation under beam or diffuse radiation, and suitability for different power requirements. Limitations include low efficiency, higher initial cost, and intermittent generation dependent on sunlight.

5. Explain how a solar PV module is formed from solar cells.

Model Answer: A single solar cell produces low voltage and small power. To get usable electrical output, many cells are connected in series and/or parallel. These interconnected cells are encapsulated using materials like glass, EVA, and backsheet in a frame to form a module. Modules can then be connected to form strings and arrays.

6. Describe the construction of a solar PV module.

Model Answer: A solar PV module typically consists of front glass, EVA encapsulant, solar cells, another EVA layer, backsheet material such as TPT/PVF/PET, frame, and junction box. These layers protect cells from weather, mechanical damage, and moisture while allowing sunlight to pass.

7. Explain the importance and functions of a solar charge controller.

Model Answer: A solar charge controller regulates current and voltage from the panel to the battery. It protects batteries from overcharging and over-discharging, prevents reverse current, improves charging efficiency, may provide temperature compensation, supports load control, and enhances system safety and battery life.

8. Explain why an inverter is essential in a solar PV system.

Model Answer: Solar panels and batteries provide DC power, but most household appliances and the electrical grid require AC power. The inverter converts DC into AC so that AC loads can be operated. In many systems, inverters also help in synchronization, system control, and power management.

9. Distinguish between rectifier, DC-DC converter, and inverter.

Model Answer:

• Rectifier: Converts AC to DC
• DC-DC converter: Converts one level of DC voltage to another
• Inverter: Converts DC to AC
  These converters are important in solar and electronic power systems.

10. Explain the basic construction and working of a battery.

Model Answer: A battery consists of anode, cathode, electrolyte, separator, and container. Chemical reactions inside the battery create a potential difference between terminals. During discharge, electrons flow from anode to cathode through the external load, providing power. During charging, the chemical process is reversed.

11. Explain the terms anode, cathode, and electrolyte in a battery.

Model Answer: The anode is the negative electrode that releases electrons during discharge. The cathode is the positive electrode that absorbs electrons. The electrolyte allows ions to move between electrodes and helps maintain charge balance inside the battery.

12. What is electrical load? Explain different types of loads with examples.

Model Answer: Electrical load is any appliance or equipment that consumes electrical power. Loads may be continuous, such as lighting or refrigeration, or intermittent, such as mixer or pump use. Some loads consume low power for long periods, while others use high power for short periods. Proper load understanding is necessary for solar sizing.

13. Explain the importance of solar site feasibility study.

Model Answer: A feasibility study evaluates whether a site is suitable for solar installation. It examines solar resource, site suitability, grid connectivity, land use, environmental impact, technical feasibility, regulatory issues, financial analysis, and risk. This helps avoid poor investment and ensures better project planning.

14. Write the key components of a solar site feasibility study.

Model Answer: Key components include solar resource assessment, site suitability, infrastructure and grid connectivity, land use and zoning, environmental impact assessment, financial analysis, energy yield estimation, technical feasibility, risk assessment, and regulatory considerations.

15. Explain solar resource assessment and its significance.

Model Answer: Solar resource assessment studies solar radiation, weather conditions, and historical climate data of a site. It is important because higher solar potential leads to better energy production, improved economics, better return on investment, and better system design.

16. Numerical: Calculate power if voltage is 12 V and current is 5 A.

Answer: 60 W
Model Answer:
P = V × I
P = 12 × 5 = 60 W

17. Numerical: A bulb of 100 W operates for 5 hours per day. Calculate daily energy consumed.

Answer: 500 Wh or 0.5 kWh
Model Answer:
Energy = Power × Time
= 100 W × 5 h
= 500 Wh = 0.5 kWh

18. Numerical: A fan of 75 W runs for 8 hours daily. Find daily energy consumption.

Answer: 600 Wh or 0.6 kWh
Model Answer:
Energy = 75 × 8 = 600 Wh = 0.6 kWh

19. Numerical: If a home uses 6 kWh per day and average sun hours are 5 hours, calculate DC solar system size using the formula

DC size = [Daily kWh / Average daily sun hours] × 1.15
Answer: 1.38 kW
Model Answer:
DC size = (6 / 5) × 1.15
= 1.2 × 1.15
= 1.38 kW

20. Numerical: Ten solar cells each of 0.5 V are connected in series. Find the total voltage.

Answer: 5 V
Model Answer:
Total voltage in series = 10 × 0.5 = 5 V

21. Numerical: A load of 200 W operates for 3 hours daily. Find daily energy consumption in kWh.

Answer: 0.6 kWh
Model Answer:
Energy = 200 × 3 = 600 Wh = 0.6 kWh

22. Numerical: A module gives 24 V and 8 A. Calculate output power.

Answer: 192 W
Model Answer:
P = V × I = 24 × 8 = 192 W

23. Numerical: A student lists the following loads: 2 LED bulbs of 10 W each for 5 hours, 1 fan of 75 W for 8 hours, and 1 TV of 100 W for 4 hours. Calculate total daily energy consumption.

Answer: 1.1 kWh
Model Answer:
LEDs = 2 × 10 × 5 = 100 Wh
Fan = 75 × 8 = 600 Wh
TV = 100 × 4 = 400 Wh
Total = 1100 Wh = 1.1 kWh

24. Numerical: A battery has two terminals. Name them and state the polarity.

Answer: Positive terminal and negative terminal
Model Answer: A battery has a positive (+) terminal and a negative (-) terminal.

25. Numerical / Applied: Explain what will happen if a battery in an off-grid solar system is connected without a charge controller.

Model Answer: Without a charge controller, the battery may get overcharged or over-discharged. This can generate heat, reduce battery life, damage the cells, allow reverse current, and make the system unsafe. Therefore, charge controllers are essential in off-grid battery-based solar systems.

26. Explain different types of energy sources with examples.

Model Answer: Energy sources can be broadly classified into conventional and non-conventional sources. Conventional sources include fossil fuels and nuclear energy, while non-conventional or renewable sources include solar, wind, biomass, geothermal, and tidal energy. Renewable sources are cleaner and sustainable, while conventional sources are limited and polluting.

27. Explain the role of renewable energy in reducing environmental impact.

Model Answer: Renewable energy reduces dependence on fossil fuels, lowers greenhouse gas emissions, decreases air pollution, and supports sustainable energy generation. It also helps meet energy demand with reduced ecological damage and improved long-term energy security.

28. Describe conductors, insulators, and semiconductors.

Model Answer: Conductors allow many electrons to move freely and therefore carry current easily. Insulators allow very few free electrons and strongly resist current flow. Semiconductors have conductivity between the two and can be controlled under certain conditions, making them useful in electronics and solar cells.

29. Explain the importance of voltage, current, and power in solar electrical systems.

Model Answer: Voltage is the driving force, current is the flow of charge, and power is the rate of electrical work done. In solar systems, these quantities determine module output, wire sizing, load demand, and inverter/controller ratings. Power is commonly calculated using P = V × I.

30. Write a note on the history and development of solar cells.

Model Answer: The photovoltaic effect was discovered by Edmond Becquerel in 1839. Later developments included selenium cells, Einstein’s work on photoelectric effect, Bell Labs’ practical silicon cell in 1954, and further progress in efficiency through thin-film, silicon, cadmium telluride, and silicon-perovskite tandem cells. This history shows steady improvement in solar cell performance over time.

31. Explain the working of a solar cell with reference to photon absorption and charge separation.

Model Answer: When light strikes the semiconductor, photons are absorbed and transfer energy to electrons. This creates electron-hole pairs. The internal electric field separates these charges, driving electrons toward one side and holes to the opposite side. This creates a potential difference, and when connected externally, current flows through the circuit.

32. Explain why modularity is important in solar PV systems.

Model Answer: Modularity allows solar systems to be built from small cells into modules, modules into strings, and strings into arrays. This helps scale the system according to power need, makes installation flexible, simplifies maintenance, and supports applications from small devices to large power plants.

33. Explain the main materials used in solar module construction.

Model Answer: Solar modules generally use front glass for protection and light transmission, EVA as encapsulant, solar cells for power generation, backsheet materials such as TPT/PVF/PET for rear protection, frame for structural support, and junction box for electrical connections. These materials help ensure durability and performance.

34. Describe the major functions of a solar charge controller in an off-grid system.

Model Answer: A charge controller regulates charging current and voltage, protects against overcharge and deep discharge, prevents reverse current, may provide temperature compensation, improves battery life, and may control connected loads. These functions are essential for safe and efficient off-grid battery charging.

35. Explain the importance of battery maintenance in solar systems.

Model Answer: Battery maintenance is important because batteries store energy and are sensitive to charging conditions. Proper maintenance improves service life, efficiency, safety, and reliability. Charge controllers help by adjusting charging parameters and protecting batteries from harmful conditions such as excessive charging and deep discharge.

36. Explain the different types of power converters used in solar-related electrical systems.

Model Answer: Common power converters include rectifiers, DC-DC converters, and inverters. Rectifiers convert AC to DC, DC-DC converters change one DC voltage level to another, and inverters convert DC to AC. These are used in computers, PV systems, batteries, and load supply arrangements.

37. Explain how batteries support continuity of supply in a solar PV system.

Model Answer: Solar panels produce power only when sunlight is available. Batteries store excess energy during charging and supply it to loads later, especially at night or during low sunlight periods. This improves system reliability and continuity of supply.

38. Discuss the role of anode, cathode, and electrolyte during battery discharge.

Model Answer: During discharge, the anode releases electrons through an electrochemical reaction and becomes the source of electrons in the external circuit. The cathode accepts electrons. The electrolyte enables ion movement within the battery to maintain internal charge balance and allow the reaction to continue.

39. Explain the process of electrical load calculation for a house.

Model Answer: Load calculation begins by listing all appliances, their watt ratings, quantity, and hours of daily use. Energy consumed by each load is found using Energy = Power × Time. Total daily energy demand is then summed. This total is used to size the PV array, battery bank, inverter, and controller.

40. Why is knowledge of appliance operating hours important in solar design?

Model Answer: Operating hours determine total daily energy consumption. Without knowing usage hours, accurate energy estimation is not possible, and solar system components may be under-sized or over-sized.

41. Explain the importance of feasibility study before installing a solar project.

Model Answer: A feasibility study ensures that the proposed site has adequate solar resource, suitable conditions, acceptable economics, regulatory compliance, grid access, manageable risk, and acceptable environmental impact. It helps avoid poor planning and improves project success.

42. Explain how solar potential assessment helps optimize energy production.

Model Answer: Solar potential assessment identifies sites with strong sunlight and fewer shading or climate issues. Choosing a better solar resource location increases electricity generation from the same installed capacity and improves overall project performance and return on investment.

43. Numerical: Calculate the current drawn by a 120 W load operating at 12 V.

Answer: 10 A
Model Answer:
P = V × I
I = P / V = 120 / 12 = 10 A

44. Numerical: A 60 W lamp runs for 6 hours daily. Calculate daily energy consumption.

Answer: 360 Wh or 0.36 kWh
Model Answer:
Energy = 60 × 6 = 360 Wh = 0.36 kWh

45. Numerical: A solar module has an output of 18 V and 5 A. Find its power.

Answer: 90 W
Model Answer:
P = V × I = 18 × 5 = 90 W

46. Numerical: Twelve solar cells of 0.6 V each are connected in series. Find the total voltage.

Answer: 7.2 V
Model Answer:
Total voltage = 12 × 0.6 = 7.2 V

47. Numerical: A refrigerator of 200 W operates for 10 hours per day. Find daily energy use.

Answer: 2000 Wh or 2 kWh
Model Answer:
Energy = 200 × 10 = 2000 Wh = 2 kWh

48. Numerical: Daily energy demand is 4.6 kWh and average sun hours are 4 hours. Calculate DC solar system size using

DC size = [Daily kWh / Average daily sun hours] × 1.15
Answer: 1.3225 kW
Model Answer:
DC size = (4.6 / 4) × 1.15
= 1.15 × 1.15
= 1.3225 kW ≈ 1.32 kW

49. Numerical: A home uses 3 LED bulbs of 9 W for 5 hours and 2 fans of 70 W for 6 hours. Find total daily energy consumption.

Answer: 975 Wh or 0.975 kWh
Model Answer:
LEDs = 3 × 9 × 5 = 135 Wh
Fans = 2 × 70 × 6 = 840 Wh
Total = 975 Wh = 0.975 kWh

50. Applied question: Why should a solar system designer estimate both technical feasibility and financial feasibility?

Model Answer: Technical feasibility ensures the system can work properly at the chosen site, while financial feasibility checks whether the project is economically practical and beneficial. Both are necessary for successful and sustainable solar implementation.