a) Flat Plate Collector
b) Photovoltaic (PV) Cell
Solar Energy (Intro)
Solar energy is the energy received from the Sun in the form of light and heat. It is clean, abundant, and renewable, and can be converted into useful electrical or thermal energy using appropriate systems.
There are two main types of solar energy conversion:
- Solar Photovoltaic (PV) – Converts sunlight directly into electricity
- Solar Thermal (Flat Plate Collector) – Converts sunlight into heat for thermal applications
a) Flat Plate Collector (Solar Thermal Conversion)
Construction (Diagram Description):
- A flat rectangular box with:
- Black-coated absorber plate on top (glass cover to trap heat)
- Copper/metal tubes placed below the plate
- Cold water inlet at the bottom
- Hot water outlet at the top
- Connected to a storage tank
(Sketch Description: A rectangular box with zig-zag copper tubes, black absorber plate, cold water in at bottom left, hot water out at top right, and a glass cover on top.)
Working Principle:
- The collector is placed at an azimuth angle to receive maximum solar radiation.
- Solar radiation enters through the transparent glass and gets absorbed by the black absorber plate.
- The absorber plate heats up and transfers this heat to the water flowing in tubes.
- Cold water enters from the bottom, gets heated as it flows through tubes, and exits as hot water from the top.
- This circulation continues until the water in the tank and tubes reach the same temperature.
Applications:
- Water heating for domestic use (solar geysers)
- Agricultural drying
- Space heating systems
b) Photovoltaic (PV) Cell (Solar Electrical Conversion)
Construction (Diagram Description):
- Two semiconductor layers:
- N-type (top) – has excess electrons
- P-type (bottom) – has electron holes
- Between them is the depletion region
- External wires connect both layers to complete the circuit
(Sketch Description: A sandwich-like layer with sunlight falling on N-type layer, arrows showing electron flow from N-type to P-type through the external circuit.)
Working Principle:
- When sunlight (photons) falls on the N-type semiconductor, it excites electrons and breaks the equilibrium at the junction.
- These excited electrons flow from N-type to P-type via the external circuit.
- The movement of electrons creates direct current (DC) electricity.
- The generated electricity can be used immediately or stored in batteries.
Applications:
- Powering homes, street lights, calculators
- Solar power plants
- Off-grid and rural electrification
Summary:
| Component | Conversion Type | Output | Working Principle |
|---|---|---|---|
| Flat Plate Collector | Thermal (Helio-Thermal) | Heat (Hot water) | Heat absorbed by tubes, heats water |
| PV Cell | Electrical (Helio-Electrical) | Electricity (DC) | Photons excite electrons in N-type semiconductor |