A solar water heater is a device that uses solar energy (sunlight) to heat water for domestic, commercial, or industrial use. It converts solar radiation into heat energy using a solar collector. Solar water heaters reduce electricity bills significantly and are eco-friendly. They are promoted by the Indian government through MNRE (Ministry of New and Renewable Energy).
Solar water heater uses solar energy to heat water via flat plate or evacuated tube collectors.
Two types: Flat Plate Collector (FPC) and Evacuated Tube Collector (ETC).
ETC is more efficient in cold/cloudy weather; FPC is cheaper.
100 LPD system saves 1,500–2,500 units of electricity per year.
Payback period: 3–5 years; low maintenance; eco-friendly.
NCERT Class 10 Science Chapter 14 — Sources of Energy.
Working Principle: • Solar collector (flat plate or evacuated tube) absorbs sunlight • The absorbed solar energy heats water or a heat transfer fluid in the collector tubes • Hot water rises and moves to a storage tank (due to thermosyphon effect — natural convection) • Cold water from the tank flows down to the collector to be heated • Hot water from the tank is available for use
Types of Solar Water Heaters:
Flat Plate Collector (FPC): • Most common type for homes • A flat metal absorber plate (painted black) in an insulated glass-covered box • Good for moderate temperatures (up to 80°C) • Cheaper than evacuated tube type
Evacuated Tube Collector (ETC): • Glass tubes with vacuum between inner and outer tubes • Vacuum reduces heat loss significantly • More efficient in cloudy/cold weather • Higher temperature achievable (up to 200°C) • More expensive but better performance
Components: • Solar Collector (FPC or ETC) • Insulated Storage Tank • Pipes and fittings • (Optional) Pump for forced circulation systems
Capacity: • 100 LPD (Litres Per Day) system: suitable for 3–4 family members • 200 LPD: 6–8 members • Commercial: 500 LPD to several thousand LPD
Benefits: • Saves 1,500–2,500 units of electricity annually (for 100 LPD) • Reduces electricity bill by ₹2,000–₹5,000 per year • Eco-friendly — no CO₂ emissions • Low maintenance • Payback period: 3–5 years
Government Support (India): • MNRE (Ministry of New and Renewable Energy) provides subsidies • PMSY scheme — promotes solar water heating • BIS standard: IS 12933 for solar water heaters
Limitations: • Works best in sunny regions • Not effective on cloudy/rainy days without backup • Large space required for installation
NCERT: Class 10 Science Chapter 14 — Sources of Energy
A solar water heater absorbs sunlight through a solar collector (flat plate or evacuated tube), which heats the water inside. Hot water rises to an insulated storage tank by natural convection (thermosyphon effect), while cold water flows down to the collector. Two types: Flat Plate Collector (FPC) — cheaper, good for moderate temperatures; Evacuated Tube Collector (ETC) — more efficient, works in cold/cloudy weather. A 100 LPD system saves 1,500–2,500 electricity units annually.
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