Heat pipe evacuated tube solar collectors contain a copper heat pipe, which is attached to an absorber plate, inside a vacuum sealed solar tube. The heat pipe is hollow and the space inside is also evacuated. Inside the heat pipe is a small quantity of liquid, such as alcohol or purified water plus special additives. The vacuum enables the liquid to boil at lower temperatures than it would at normal atmospheric pressure. When sunlight falls the surface of the absorber, the liquid in the heat tube quickly turns to hot vapor and rises to the top of the pipe. Water or glycol, flows through a manifold and picks up the heat. The fluid in the heat pipe condenses and flows back down the tube. This process continues, as long as the sun shines.

Since there is a "dry" connection between the absorber and the header, installation is much easier than with direct flow collectors. Individual tubes can also be exchanged without emptying the entire system of it's fluid and should one tube break, there is little impact on the complete system.

Heat pipe evacuated tube solar collectors must be mounted with a minimum tilt angle of around 25