Evacuated Tube
Solar Hot Water Heater

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Evacuated tube is a solar collector for water heating that uses a vacuum glass tubes to absorb heat from the sun. These single collectors have two layers of glass, joined together, absorbing film, and vacuum between to prevent a heat loss from the absorber.

evacuated tubeThese single solar tubes are combined into groups, supported by the frame and manifold or water tank at the top.

Evacuated solar tubes are usually connected to the manifold in a way to allow easy installation and replacement (plug-and-play principle).

The main advantage of evacuated solar tube water heater is the ability to heat the water even during the cloudy days. Because of its cylindrical shape, the evacuated tube is facing the sun all the time and therefore is more efficient than other solar water heaters. As long as the sun shines the evacuated solar tube hot water heater can be in service all year round.

You can use this system even in cold climate, as the selective coating and vacuum layer prevents heat loss and ensures high energy absorption.

Since the heat pipes transfer heat in one direction only and within the collector, over 92% of the heat is absorbed and less than 8% is heat loss.

How it works

vacuum tubes

Pressurized Solar Water Heater with Vacuum Glass Tubes and Heat Pipes

When the evacuated solar tube is exposed to the sun, it absorbs the heat. The heat tube located within the evacuated glass tube gets warmer and the liquid (alcohol, acetone) in the heat tube quickly turns to hot vapor.

The steam, or hot vapor rises to the top of the heat pipe. Cold water or glycol that flows through the manifold picks up the heat.

The fluid in the heat pipe gets colder and condenses (turns into liquid) and goes down to the base of the heat pipe. The cycle starts all over again and continues till solar tube system has enough sunlight or diffuse light. Recommended tilt angle should be maintained.


  • The evacuated solar tube system provides a free solar water heating, reducing your utility bills significantly.

  • This solar water heater provides an easy DIY installation.

  • High efficiency as the heat is transferred only one way.

  • High transfer rate with copper tubes.

  • High absorption with using vacuum and special absorption film.

  • Can operate in colder climates.

  • Works great in overcast or in diffuse sunlight conditions.

  • Evacuated solar tube doesn't need maintenance.

  • Broken tubes can be easily replaced.

  • It is built to last.

(Photo credit to Amazon)

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