Which system to use?

[Core]

In Hong Kong, frost isn't a problem to worry about. In the rare case it should happen, the system will simply circulate water to keep it frost free.

There are other considerations, though, like overheating and boiling. To some extent, this can be solved by having the right dimension of expansion tanks, but a drainback type solar thermal system can entirely mitigate that challenge.

[Richard]

Hi, i'm a solar lover in the states, Texas i was wondering, because the weather here is crazy, most of the time hot in my area, do it still have to use anti freeze then? how does your system work?

[Core]

Hi, i'm a solar lover in the states, Texas i was wondering, because the weather here is crazy, most of the time hot in my area, do it still have to use anti freeze then? how does your system work?

What matters is whether or not it is likely to become freezing temperatures or not.

If there is any chance of freezing, there are several ways to protect your system. Which solution is better depends on how often, for how long, and how much below freezing it is likely to be.

1) Drainback system. If all the liquid drains back when the system is not in use, that is protection in itself. There won't be any (substantial) liquid in panels nor pipes, to cause any damage. Drainback systems need to be designed carefully, in order to ensure the liquid doesn't get stuck.

2) Anti-freeze. You can add more or less anti-freeze, typically glycol (Propylene glycol is the most common). Lowering the freezing point enough to ensure the liquid will never freeze.

3) For rare or light frost, the system could be designed to start circulation, sending heat the wrong way (back to the panels). This is counter-productive wrt to production of energy, but if the chance and severity of frost is low, it will not matter in the big picture. One disadvantage is that in case of power outage or system failure, the system might not be able to protect itself.

We are doing the drainback principle. We don't have a ready system yet, still in the development phase for the combined system.

Good luck, Richard.