[ldjessee]

The high temps (and to keep it from freezing as easily) was why they used the new antifreeze/coolant (propylene glycol). Infact, I would have assumed that this substance is what is used down into some kind of heat exchanger that would be in the attic or basement or what have you.

If you could put a bigger tank, that was well insulated, then you could have a heat 'battery' for hot water use into the night.

I also found another misconception I had, that being that the pipes in the evacuated tubes are not flow through, but dead ends. I thought that cold fluid would be pumped up from the bottom, through the tubes, then hot would come out the top. The pump would be controlled by temp difference of the cold vs hot (and obviously minimums and maximums). But, being dead ends, they need to rely on convection to let heat rise to the top. I still think a loop would be more efficient, even if it was just down the 'back' side in the tube.

I also see that many have little solar panels (assume to run the pumps), but if they work well on cloudy days, then would they draw on other electric sources to run the pump if the system started to overheat?

I have asked a company to come out and evaluate my 'site' (roof/front yard), as solar hot water is not as expensive as PV.

Wonder if anyone ever made a Stirling engine run from excess heat produced during the day, when most people are at work? They supposedly run quietly and if you could stick it just below the panel with maybe a automatic valve that once your storage tank is at temperature and maintaining it, then run a stirling engine to produce electricity?