Vacuum tubes

First of all, vacuum tubes are a much better insulator. The heated water flowing through these tubes will retain its heat much better. Especially in cold weather, the difference between a conventional solar collector and vacuum tubes is obvious.
A second advantage of vacuum tubes is their great freedom of placement. The sun will always shine optimally on the tubes, in contrast to a flat surface. Thus, even in the morning as in the evening, the sun will always shine optimally on the solar collector.
A third advantage is the great resistance to wind. Multiple vacuum tubes are placed next to each other, but still provide space in between for the wind. A final advantage is high serviceability. After all, all vacuum tubes work separately from each other. If a tube fails, you can easily replace it.