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IrC
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Endimion17 you sound pessimistic about DIY. Living for over 30 years in Arizona I saw many, these setups numbered in the thousands. Radiators were
loved in these, in the era of the 70's you could collect many for very low cost and flat black paint was cheap. One I knew of used crushed granite for
near zero cost from an open pit Cu mine. He had a setup with pipes running through rock for storage, a little bleach in the water stops mold. Not to
mention a percentage of antifreeze and rust inhibitor from Checker Auto was also unfriendly for bacteria. Or have you never slept for years on a water
bed with the same water in it. No it never got moldy. He never turned on heat in the winter his system did it all. Decently warm showers and never the
need for a furnace. In January it typically gets to 19 at night but back to the 60's in the day with strong solar radiation normal every day. In a
quarter century I don't recall any times he was out repairing things nor did I ever hear complaints about maintenance. That was one of his bragging
points, he never had to muck with it much at all ever. I cannot fathom where you are getting all your negative waves about home built solar in the
desert it has been popular for decades.
"Science is the belief in the ignorance of the experts" Richard Feynman
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GreenD
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Good points.
If you use water from your pipes, why would the water be any different than if it were coming from your faucet?! If you build the setup correctly,
there should be no more "Stink" or "mold" than from your kitchen sink.
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White Yeti
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As a side-note, I compared my original jar filled with sticks and it was getting much warmer than my control set-up. I wondered why...
As it turned out, the warmth was due to the anaerobic digestion of the sticks in a warm environment. The sun was providing the "activation energy",
but the decomposition that was happening inside was what held the internal temperature close to 28-30C while the external temperature was 10 degrees
centigrade.
I wonder if this would be a controllable way to harness biomass energy on small scales. If you get a biomass-sun hybrid system to heat you house, the
sun heats the biomass and all the bacteria, those bacteria produce useful co-products, heat, biogas and fertiliser.
That way, you can break down wood more efficiently than if you burned it in a fireplace. Here's a more extreme example of heat generation from biomass.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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Endimion17
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Quote: Originally posted by IrC  | Endimion17 you sound pessimistic about DIY. Living for over 30 years in Arizona I saw many, these setups numbered in the thousands. Radiators were
loved in these, in the era of the 70's you could collect many for very low cost and flat black paint was cheap. One I knew of used crushed granite for
near zero cost from an open pit Cu mine. He had a setup with pipes running through rock for storage, a little bleach in the water stops mold. Not to
mention a percentage of antifreeze and rust inhibitor from Checker Auto was also unfriendly for bacteria. Or have you never slept for years on a water
bed with the same water in it. No it never got moldy. He never turned on heat in the winter his system did it all. Decently warm showers and never the
need for a furnace. In January it typically gets to 19 at night but back to the 60's in the day with strong solar radiation normal every day. In a
quarter century I don't recall any times he was out repairing things nor did I ever hear complaints about maintenance. That was one of his bragging
points, he never had to muck with it much at all ever. I cannot fathom where you are getting all your negative waves about home built solar in the
desert it has been popular for decades.
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I'm pessimistic for a reason. Of course, you can build it yourself correctly, but the price jumps up the better you do it.
There are essentially two ways you can do it - with and without secondary heat loop. AFAIK, only the latter systems give you potable water.
The main issue is the local climate, of course. I can totally see DIY one-loop systems working (and paying off in a few years!) in my area, and that's
why I'm planning to do it one summer.
Two-looped DIY systems... I'd say the time to pay it off would be short enough in the equatorial zone. Mediterranean area and Florida, I hardly
think so. That's why people buy them, and yet it's still expensive.
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Dr.Bob
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There is some confusion around the original question. If you live in FL or Hawaii, you can just paint a tank black and put it on the roof. But if
you live in most places, it would freeze and burst at night, or at least lose most of the heat to the cold air. So most people put in a heat
exchanger solar system, and since that requires a fair amount of pumping, piping, and other stuff, the costs go up.
The cost of the actual collector is not that much wholesale (under $1000 each, most areas would need 2 for enough hot water for 4 people), so that
part you can save money on, but the quality won't be as good. If you already have a lot of copper tubing and such, you can build one, but that won't
save so much. The largest cost is the labor of installing the rooftop part, running the pipes, and connecting it all to a water heater tank, which
will cost about $500-700 or more itself, for one with a heat exchanger built in. But the parts are getting cheaper to buy pre-built everyday, even
for decent quality.
On the other hand, a heat pump water heater is more appropriate for some areas with mild climates, and can be either stand alone, or part of a
geothermal heat pump system. I have three friends with these systems and they are interesting solutions.
One has the stand alone heat pump water heater, which is in his garage in a warm climate, so it actually air-conditions his garage while moving the
heat into the water tank. That is a great solution. The other two people bought whole house geothermal heat pump systems, and one has broken even
(compared to natural gas, which is available in his area, and prices are falling), and the other; who lives in an all electric neighborhood, is seeing
a large cost savings over his old heat pump, which was already 15 years old and needing replacement. It provides cooling and heating to the house,
as well as pre-warmed water for his water heater. That aspect only works really well in the summer, the rest of the year it does not provide
substantial preheating.
I have also seen a number of solar thermal installations. They pay off quickest when you have a large hot water consumption, as they are cheap to
scale up. So if you have a large family, solar thermal hot water will pay off. If you are single, it might not make any sense to do anything,
unless you take really long showers, and for 2 people, the stand alone heat pump water heater is probably the best solution.
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497
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No need for copper tube for DIY setups. That crap is expensive.
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White Yeti
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If you'd make it out of anything, galvanised steel. I agree copper tubes are waay too fancy for this kind of thing.
Would PVC deteriorate under the heat? That's the cheapest tubing material I can think of.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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Endimion17
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| Quote: Originally posted by White Yeti |
If you'd make it out of anything, galvanised steel. I agree copper tubes are waay too fancy for this kind of thing.
Would PVC deteriorate under the heat? That's the cheapest tubing material I can think of. |
No, it wouldn't deteriorate from the heat. But it would deteriorate. UV rays would degrade it a lot after just one season.
Copper is expensive, though I'd use it in some parts of the system, just to give a hard time to any bacteria inside. If you use steel only, iron
bacteria would proliferate.
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Dr.Bob
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PVC would not do great in the heat that can occur in a solar thermal system, they can easily get over 180F in the summer, and that is getting to be
way above the reasonable working temp for PVC. As well, iron or steel pipe heated to 140-180F exposed to water will corrode very fast. There is a
reason that most solar collectors use copper, and that is because it will last years, even if allowed to overheat or build up pressure.
http://www.harvel.com/pipepvc-sch40-80-derating.asp:
"THE MAXIMUM SERVICE TEMPERATURE FOR PVC IS 140°F."
While it is not difficult to build a decent solar water heater, it is not trivial, and I have friends who have spent a lot of effort fixing systems
built by home owners or even some "professionals" which were built cheaply or poorly, and they failed quickly, many from freezing or a leaking pipe.
A water leak in your attic or walls can cost way more to fix the damage from than a well built system. If you want to build on, just buy one of the
better books on the subject and read it well.
Depending on your climate, there are a few various design choices, but if you buy the parts as a kit, you can build a good system for $2000-4000
yourself, and get one that will last a lifetime as well as provide hot water nearly year-round. But I would still suggest a heat pump design unless
you have a large family, based on my analysis of the payback and costs. Of course tax credits and rebates can change that dramatically.
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497
National Hazard
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Iron bacteria in glycol? That would impressive. Corrosion of steel is not impossible to prevent if you try. http://onlinelibrary.wiley.com/doi/10.1002/jctb.5010091103/a...
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Endimion17
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When did you mention glycol?
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497
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A closed loop system may be cheaper, and prevent freezing corrosion, etc. Why not use a closed loop? The heat exchanger isn't that hard.
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