Initial ideas for this project came from material found on the Built it solar website.
Further inspiration came from Dr. Ben Graveley’s work on drain-back solar and thousands of installed systems. His excellent website is here. It is full of sensible advice gleaned from years of experience with real-world systems.
In this PhD thesis, Ruslan Botpaev of the Institute of Thermal Engineering, University of Kassel, provides much information on drain-back systems: in particular relating to hydraulic phenomena during the filling and operation processes, which you can find in chapters 5.2 and 6.2 respectively.
Grundfos kindly supplied a couple of excellent UPM3L OEM test pumps. These are PWM speed controlled, with flow rate feedback. They are the only moving part of our system!
BTE Solar custom-made the ‘all copper’ collectors.
As the project advances, we’ll release the source on GitHub. It will be free for non-commercial use, with a small royalty payable otherwise, which will help with further development.