Solar Tubs

How Do Solar Vacuum Tubes Work?

01 Nov 20 - 23:19

A solar collector works like an engine of any solar water heating system. Solar vacuum tubes are very much efficient in producing solar powered systems. The vacuum tubes work similarly like the coffee thermos.

The vacuum tubes comprise of two glass layers with vacuum in between the layers. The outer layer of the tube is made from Borosilicate glass, which has very low iron content. The Borosilicate glass allows around 98% light energy to enter. The second layer is applied with special coating.

However, there are two types of solar vacuum tubes used in solar water heating systems like: Open Vacuum Tubes (Non Pressurized) and Heat Pipe Vacuum Tubes (Pressurized).

How Does Non Pressurized Vacuum Tubes Work?

These heat tubes use open vacuum tubes. Water fills up the inner vacuum tube and gets heated internally by the sun likewise liquid in a thermos. Generally, warm water is lighter than cold water. That’s why it rises up to the top of the tube where it fills the collector.

The heavier cold water goes to the bottom of the vacuum tube to take the place of heated water which will be heated again by the solar energy. This is a natural phenomenon, known as thermo-siphoning. The main reason behind using this heat system is that no expensive copper piping is used, making open tubes much more cost effective.

One disadvantage is that they can be used only in an open loop system and controlled by atmospheric pressure. This type of heating tube is ideal for swimming pools as water flows directly into the tubes. However, non pressurized vacuum tubes are used in applications above freezing. As a result, they can withstand small amounts of pressure and can’t be used in the most closed loop applications like residential hot water and space heating.

How Does Pressurized Vacuum Tubes Work?

Pressurized vacuum tubes are considered as high performance heat tubes that extend the possibilities of water heating through solar power. Its working principle is same like the open solar vacuum tubes. Only difference is that water doesn’t enter the vacuum tube physically.

However, the specially designed hollow copper heat pipes are inserted to the vacuum tube. Copper is an excellent thermo conductor as it conducts heat efficiently. The heat pipe contains pure water residing within vacuum.

Water will boil at less than 30 degrees. The hot vapor rises quickly to the top into the condenser tube. The condenser bulbs start transferring heat to the manifold (heat sink) in contact with it. They are specifically designed to attain temperatures of 200 degrees Celsius or more.

High temperature inside the heating tube results in higher efficiencies. The condenser bulbs are inserted into a copper heat transfer manifold by using multiple tubes. These manifolds can be able to withstand around 116 PSI pressure.

Remember that, the water present inside the heat pope system enters the vacuum tube. It means, this heating tube can be used in systems in colder climates. If a vacuum tube breaks down, the system continues functioning without any hassle.

The heat pipe solar tubes can be used for different applications like hot water tanks, radiators and in-floor heating. The copper collector carries a small amount of liquid and can be used with any heat exchanger by using glycol mixture to prevent freezing.

Bottom Line –

Are you thinking to use solar vacuum tubes? If yes, then you should definitely look no further than Northern Lights Solar Tubs. For professional help with the purchase, feel free to reach out to us at  +1 (800) 317-9054.


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