A liquid flat plate collector (LFPC) is a solar thermal device that absorbs solar radiation and transfers the heat to a liquid (usually water) flowing through tubes attached to an absorber plate.
Construction Details
- Absorber Plate:
- Made of copper, aluminium or steel (1–2 mm thick).
- Coated with black paint or selective coating to increase solar absorption and reduce heat loss.
- Tubes:
- Copper tubes (diameter: 1–1.5 cm) are soldered or bonded to the absorber plate.
- Tubes carry the liquid and transfer absorbed heat from the plate.
- Header Pipes:
- Larger pipes (2–2.5 cm diameter) connect all tubes at top and bottom for inlet/outlet.
- Transparent Cover:
- One or two layers of glass or plastic (thickness: 3–4 mm).
- Allows solar radiation to pass in, but blocks infrared heat loss — greenhouse effect.
- Insulation:
- Back and sides are insulated with glass wool, mineral wool, or fiberglass (5–10 cm thick) to prevent heat loss.
- Casing:
- Encloses the whole setup, usually made from metal or weatherproof material.
Working Principle
- Solar radiation passes through the transparent cover.
- It strikes the black absorber plate, which gets heated.
- The heat is conducted to the water (or antifreeze) flowing through the tubes.
- Heated water moves from the bottom to top header, then to the storage tank.
- Cooler water is re-circulated, creating a closed loop.
- Sloped mounting maximizes sunlight exposure.
Neat Sketch
Water flow in a Flat plate collector
Cross-section through liquid collector plates
Applications
- Domestic solar water heating
- Solar space heating
- Pre-heating for industrial processes
Advantages
- Simple, robust, and reliable
- Low operating cost
- Efficient for moderate temperature applications