Solar Energy Applications
Solar Energy Applications
This domain tests the main uses of solar energy beyond simple rooftop lighting: thermal systems, pumps, street lights, dryers and hybrid systems.
Core rules
- Solar thermal systems convert sunlight to heat; efficiency is thermal, not electrical. Flat-plate collectors suit low-temperature water heating; evacuated tube collectors reduce heat loss.
- Solar PV systems convert sunlight directly to electricity; applications include home lighting, street lights, pumps, telecom and rooftop grid-tie.
- Solar pump sizing depends on head, flow rate, and hydraulic energy: P_hyd = ρgQH. The PV array must be larger than P_hyd divided by pump and motor efficiency.
- Solar street lights use a PV module, charge controller, battery and LED luminaire; autonomy and duty cycle set battery size.
- Hybrid systems combine PV with grid, DG or wind to improve reliability.
Worked example
A solar pump lifts water through 20 m head at 10 m³/h. Hydraulic power = 1000 × 9.81 × (10/3600) × 20 = 545 W. With pump efficiency 0.5 and motor efficiency 0.8, shaft input ≈ 545/(0.5 × 0.8) = 1363 W. A 1.5 kW PV array is a reasonable starting point before cable and controller losses.
Traps that cost marks
Using electrical efficiency for a solar water heater; sizing a pump by motor rating without head and flow; ignoring pump efficiency; assuming a street light runs all night at full power; mixing thermal and PV energy units.