Quote:
Originally Posted by theunchosen
drem'd how exactly does your system work? I tried to find a note about it in the thread but its kind of long.
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The thread has gotten pretty darn long.
Fairly simple setup; Cold Water source(well) ->Batch heater(44 gallon tank in reflective box with doubble pane glass on top) -> tankless (heats the water from the solar heater up to desired thermostat temperature whenever the soar heater is unable to supply sufficient water temperature)-> House
Ideally I'd add a 4 way mixing valve so nobody burns themselves during the summer when the solar heater gets up in the 150+ range; but I just warn all of my house guest to be careful and it hasn't been an issue *yet*.
Currently my only "complication" is a valve I use to bypass the solar heater when it's freezing out.
Quote:
Originally Posted by theunchosen
Are you pumping the water to the roof heating it and bringing it down?
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No; everything operates in-line with my domestic water pressure being the only pump.
KISS
Well; in a way I guess my well pumps the water up to the roof . . .
Quote:
Originally Posted by theunchosen
Whats a much better setup us filling the pipes with anti-freeze and running that pipe outside the water as it comes in. So a wide pipe that runs anti-freeze and then your water pipe flows through that.
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That would require a lot more parts and I wanted it as simple as possable. This way I have no thermostats, pumps, heat exchagers, toxic fluids, etc to cause issues.
If I would do a new/ different setup I'd go with a drain back pretty much exactly like this one
The $1000 Soalr Water Heating System
What I actually want to do (eventually) is build a much larger version of that drain back system and use it as house heat + hot water . . ..
Quote:
Originally Posted by theunchosen
Technique 2 is easier, but requires a rather large tank. Run the anti-freeze pipes into something akin to the coil on the back of your fridge and pump water into the tank.
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I only see 1 tequnique above; I guess I'm just not following you.
Quote:
Originally Posted by theunchosen
The anti-freeze has a higher heat capacity than water
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False. I thought it was true until I got real technical with cooling on a road race Supra; most antifreezes reduce heat capacity/ mass by 10~20% per degree rise.
Quote:
Originally Posted by theunchosen
, a lower freezing point,
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True; but only an issue 5~7 nights a year at my location. If I lived someplace colder my setup would not be ideal . . . .
Quote:
Originally Posted by theunchosen
and more capable of energy transfer.
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False; Antifreeze reduces heat transfer. The only time that antifreeze will transfer more energy than pure water is when the hot surface being cooled by the water is exceeds the boiling point of water at the current pressure. (Basically water conducts heat VERY poorly as a gas; but VERY good as a liquid)
Quote:
Originally Posted by theunchosen
Also another thing the more coolant(anti-freeze) you have in the lines the more energy is stored.
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My batch heater holds 44 gallons (I *think* +-4 gallons). Bigger tank would be better, but this is typically sufficient. My big issue is that I have far to many feet of pipe from the 1 sunny spot on my roof back to my original hot water location.
Ideally that tank/ thermal mass would be in 1 lump with as few lines as posable (Pipes are difficult to insulate effectively and therefore loose more heat than anything).
Quote:
Originally Posted by theunchosen
If you can get a separate insulated tank for the anti-freeze(a very small tank only a few gallons) you can store that extra heat overnight.
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I can promise that you need more than just a few gallons to be useful for domestic hot water unless stored at very high temperature. Then there are a few drawbacks
1) more exotic materials for containment (must resist higher temps)
2) potentially more exotic storage medium Antifreeze is only good so high.
3) more insulation required to counter the higher delta between storage medium and ambient
4) naturally smaller solar window due to the higher temperature required which can be partially countered by solar trackers, but that adds cost and complexity.
Quote:
Originally Posted by theunchosen
With this system the best approach is to have the pump cut off overnight
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The best approach for a system like you are describing is a differential thermostat such as
SunEarth Differential Temp Control - Differential Temperature Controllers @ AltE
Quote:
Originally Posted by theunchosen
and have a pressure valve that doesn't open unless the pump is going(to keep from circulating the hot anti-freeze up to your roof and convecting it away).
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Why not shut off the pump? that eliminates the extra parts, and saves energy in not running the pump.
WOW that took almost an hour for a reply.
More questions are certainly welcome.