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Short note: Solar water heater

Short answer

A solar water heater uses a collector and insulated tank. Water heated in the collector rises by thermosiphon to the tank, providing water at 50-70°C. It saves electricity/fuel and is widely used in Nepalese homes and hotels. An electric backup may be added.

Write a short note on solar water heater.

A solar water heater (SWH) uses solar radiation to heat water for bathing, washing and industrial use, which saves electricity, LPG or firewood.

Main parts

  • Collector: flat-plate collector (black absorber plate with copper tubes, glass cover, insulation) or evacuated tube collector.
  • Insulated storage tank for hot water.
  • Pipes, a cold-water inlet, and a hot-water outlet.
  • Optional electric back-up heater for cloudy days.

Working

Sunlight passes through the glass and is absorbed by the black plate, heating the water in the tubes. Hot water, being lighter, rises to the tank and cold water from the bottom of the tank enters the collector. This thermosiphon circulation needs no pump (the tank must be higher than the collector). Large systems use a pump (forced circulation).

   Hot water out
      ^   [ Tank ]
      |    ^    |
   rising | hot  | cold falls
      |   [Collector]<--sun
   Cold water in

Water temperature reaches 50–70 °C. It is widely used in Nepal (urban houses, hotels, hospitals). Advantages: free energy, low running cost, no pollution. Limits: lower output on cloudy days, scaling in hard water, and freezing in very cold regions unless an antifreeze loop is used.

✓ Answer checked by Claude Opus 5.5 (high effort)

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