Evacuated Tube Collector

The Latest in Solar Water Heating!

Do you want hot water around the whole year? Then an Evacuated Tube Collector is what you need to get free hot baths the whole year.

These Evacuated Tube Solar Collectors have an array of glass tubes instead of a simple flat – plate collector. These resemble the Flat – plate collectors only in one way. They heat water by using solar energy.

Photo By Chris

The Glass tubes are a major component in such systems. Every single evacuated tube has two glass tubes. The tube on the outside is made of extremely strong and transparent borosilicate glass. This tube can withstand impact of up to 25mm hail stones. Now That’s truly durable!

The Inner tube is also made from borosilicate glass and is given a special coating which exhibits excellent properties of sunlight absorption and minimal heat reflection properties. Air is removed from the space between the two glass tubes thereby creating vacuum between them. This Vacuum acts like an insulator and also helps in reducing the radiant heat losses.

What happens inside?

Inside the evacuated glass tube a copper heat pipe is installed. This heat pipe acts as a medium of heat transfer to its tip. This tip is connected to the collector’s heat exchange system. As water passes through this heat gets transferred to the water. The Heat transfer system is securely insulated in an aluminum enclosure.

How does the Heat get transferred to the water?

The arrangement for heat transfer is rather simple. The copper heat pipe is hollow and is filled with acetone. The hollow centre of the heat pipe is vacuum and hence even at temperatures as low as 40°C the acetone vaporizes (i.e. it boils). This vapor then rises to the tip of the heat pipe where the heat is transferred to the water in the heat exchange system.

Now as the heat transfer process continues the vaporized acetone condenses and simply flows back down the heat pipe and the process keeps on repeating.

The process of heat transfer is more efficient to that of conventional flat-plate collectors and solid copper rods. Thus heat transfer takes place more effectively from the evacuated glass tube to water.

Heat Transfer Mechanism


  • As compared to any other solar collector system the evacuated tube collector provide excellent results on cloudy days. Wind and low temperatures have minimal effect on the working of the evacuated tubes due to the insulating property of vacuum.

  • No water flows through the tubes and to add to it the tubes are hermetically sealed. Due to this evacuated tube solar collector doesn’t suffer from corrosion problems as compared to other solar collector systems. Hence more life of the collector.

  • As the tubes are round, the sunrays incident on the evacuated tubes are always perpendicular thereby reducing reflection.

Now that you know the benefits of an evacuated tube collector, you may decide to buy your own. Go for It!

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