Drain Back, Low Flow Solar Combi Systems: Design, Monitoring and Simulation

Drain Back systems with ETC collectors are tested and analyzed in a Danish - Chinese cooperation project. Experiences from early work at DTU, with drain back, low flow systems, was used to design two systems:
1) One laboratory system at DTU and 2) One demonstration system in a single family house in Sorö Denmark. Detailed monitoring and modelling of the system in the DTU lab is done to be able to generalize the results, to other climates and loads and to make design optimizations.
The advantage with drain back, low flow systems, is that the system can be made more simple with less components and that the performance can be enhanced. A combination of the drain back- and system expansion vessel was tested successfully. Small initial problems with installation and proposals for design improvements to avoid these in practice are described in the paper. Installer education and training is an important step to have success with drain back systems.