In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
"Steamback" is the word now being used to describe what happens to closed-loop solar systems during stagnation. If you correctly size your expansion tank and relief valve, the fluid in the solar panels will vaporize and push all the liquid out of them, thereby protecting the glycol from high temperatures.
Siggy's first article on the design criteria for these systems was published in PME a few months ago, but the original research was done in 2003 in Germany by Hausner & Fink.
Besides protecting the glycol, it provides an elegant means of overtemperature protection, and eliminates the need for inelegant "heat dumps". The controller simply lets the panels stagnate, and the excess heat is thereby rejected before it is collected.
I think I know why we didn't think of this way back in the 80's: We were used to thinking of solar panels as boilers and were scared to death at the thought of "dry firing".
1. Has anyone done a system like this, and are you satisfied with it?
2. Who was the person who coined the term "Steamback"?
Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments