Solar evacuated tube or vacuum tube collector comprises a number of rows of parallel transparent glass tubes connected to the header pipe and where the heat transfer fluid (generally 50% Propylene Glycol) circulates and absorbs heat generated by the tubes. 

The glass tubes have a cylindrical shapes. You should always choose the collectors that provide the optimal combination of thermal performance, quality, and cost. That’s why solar evacuated tube collectors are superior to flat plate

Generally, a solar vacuum tube is perfect for applications like heating water and space in the Northern climates. Solar evacuated tubes work really well for solar pool heating purposes as they can be able to heat the pool even if the weather is cloudy. They provide enormous heat energy for heating pool, water and space even when the outside temperature is minus 40 degree. 

However, solar vacuum tube water heating kits are used to harness the solar energy and turn it into hot water for your home