Solar hydronic heating, via evacuated tubes


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Old 02-15-08, 09:15 PM
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Solar hydronic heating, via evacuated tubes

Hello, for some time now I've been looking into various alternative systems of which can be used to heat living spaces.
The most promising I've seen so-far happens to be the Evacuated glass solar tube system. That this system works on the principle of solar radiation being converted to heat (reportedly tubes can reach an inner temp of 300f.) by the vacuum tubes, thus heating a closed-loop purified-water system, that it turn heats the circulating radiator/hydronic heat system already piped in the house via a modified heat-exchange tank.

Now, see, I understand the science quite nicely (sun makes things hot, duh... ), and I've read oh-so many fine (praising!) examples of this system type being used for domestic tap water heat...
However I've read conflicting reports on its effectiveness as a system for heating of living space. Even though some praising reports were from Finland (a very cold place), some people have cautioned to not used this system in cold/harsh climates. Quite the disparity, that...

My plan is quite simple: to start off small by piping my detached garage that is nearly 800sqft. but very well insulated via foam, 2 layers sheathing OSB and HardiPlank siding, plus interior layer of OSB(fire rated)paneling. I live in a region of The USA Midwest that tends to stay between 20f and 40f for most of the winter with very little in the way of snow accumulation. But usually semi-overcast and rather constantly wet... "dreary" sums it up nicely.

Now before I go and take the (expensive) plunge and invest time (MONEY!) and effort (MONEY!)... or even more research (MONEY!)... I'm throwing this out there to you all, to ask what you're personal knowledge/experience has been with such a system of similar.

Just to reiterate, I'm only looking into hydronic-heat vacuum tubes, not photovoltaic panels or shingles. (whenever I ask anyone locally about ANYthing solar, all they seem to know about solar is the antiquated bulky voltaic collection boxes that sit in sticks on roofs) bleh...

Thanks to anyone that has any insight.


handy little info page with pictures!
http://www.reuk.co.uk/Evacuated-Tube...er-Heating.htm
 
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Old 02-17-08, 03:44 PM
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Quote "dreary sums it up nicely" I've installed a solar air heater and it works but no sun no heat. In Wisconsin, in the last 2 months maybe 5 days were sunny. I'm happy though because I built it myself investing $300 for 96 sq. ft of panel. True the evacuated tubes produce more heat per sq ft but how about per dollar? Wouldn't the water freeze and bust everything? Preheating hot water could be used year round and still lower fuel bills. Let's face it seasonal depressive disorder comes from no sun in the midwest winter.
 
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Old 02-17-08, 08:01 PM
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Solar "air" heaters are rather inefficient, from what I've gathered, they fail to expound on all potential heat energy, even on dreary days. And then lose much heat value as the heat is transitioned into the space.

As far as tubes, I've not yet worked out a cost/value ratio, I have worked out that each tube captures approximately 80-150 watts or 300-450 BTU/HR, depending of the reflector area and available direct or filtered light.
And no, the glass tubes do not hold any liquid, the metal rods inside the tubes may contain either purified water, glycerin, or anti-freeze. Basically any liquid that can conduct heat and be pumped will work. So there's little to no chance of breakage as far as I can see.
 
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Old 02-18-08, 01:24 PM
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Difficult to determine the efficiency of my simple solar panels. The 4x8ft house panel has south windows helping. When it's really really cold it's sunny. On a -10 day with a 20 mph Canadian dry wind, the furnace doesn't kick in between 9 and 6. The 8x8ft panel kept the insulated 30x46 garage about +40 all of Jan. Not ideal working temperature but it's easier to heat to 70 from 40 than from 10. On cold overcast day they do heat but barely. To date -10 days cost less than + 25 days. They work best when needed the most. Now if only I could store some heat for the evening. Thinking the same design but with coolant lines weaved in the black sheet metal behind the insulated greenhouse polycabonate glazing. I could store that
 
 

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