Yeah, I remember seeing that in my researches (very good site)... and thinking “Oh no! There’s got to be a better way!” LOL!
But for that kind of system it struck me as a very good design.
Can you quantify it’s performance and payback?
Or are you just satisfied that it makes a significant improvement in cost and comfort.
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Can you quantify it’s performance and payback?"
Cost recovery will very from one kind of build and climate to another. I only recently built up the PV solar electric system enough here to keep the computer on and connected to sensors for data gathering and analysis. Pretty busy around here for now.
But Gary Reysa, retired aviation engineer at builditsolar.com (site linked in one of my previous comments in this thread), posted some payback time info and other info about his systems at his site. Remember that these systems are built and modified in many ways to fit various situations (e.g., heavily insulated concrete tanks), but they'll work well just about anywhere.
The Solar Shed -- Using Solar Collectors Mounted on an Outbuilding for House Heatinghttp://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm
$1000 Solar Water Heater --Overviewhttp://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm (best tutorial to start with, in my opinion)
Look for the info on system sizing, BTUs (regarding the water storage tank), etc.
Gary's climate in Montana during winter (farther north, less sunny but lower elevation and generally warmer situation farther from peaks) is only a little warmer but slightly less sunny than mine.
The following might be useful when reading about the BTUs stored in a tank of water.
A BTU is the amount of energy needed to raise the temperature of a pound of water by 1 degree, Fahrenheit. A gallon of water weighs about 8.34 pounds at 62 degrees, Fahrenheit.
I was completely new to thermal tech. not long ago and am still not very educated in it.
All of that said, passive solar builds are generally much more cost effective than active ones. South-facing sun rooms with greenhouse vents can be very nice if well built.
The following is the first in a series of tutorials on building a collector that is great for modular/seasonal, quick-disconnect installs. Very light weight and easy to handle.
Hot and Cold: D.I.Y. Solar Hot Water Collectors (Part 1)
https://www.youtube.com/watch?v=QPxQVv1hmQE