SEIDO2 is a direct flow evacuated tube. Configuration and appearance are similar to SEIDO1 and SEIDO5 but the heat pipe is replaced by a coaxial set of copper tubes. The heat transfer from the absorber to the heat circulation is performed applying direct flow. The heat transfer liquid flows through a concentric tube integrated into the absorber picking up thermal energy by direct heat exchange. The cold liquid is inducted through the inner tube. It flows back in the gap between the inner and outer tube. The inlet and outlet tube of each collector tube are connected to the manifold. All tubes are connected in parallel.
This system allows for installation of the module at angles between 0° and 90° allowing the absorber surface being adjusted to the optimum position towards the sun. The operating principle permits horizontal installation on flat roofs or integration into the facade of buildings.