solar thermal savings

scott markle_2

Bob,

I can see how a radiant slab or other low temperature emitter could be used to extract heat from an evac. collector in diffused sunlight winter conditions. The problem I see is how to combine this low temperature water with other sources of heat.

Obviously a few square meters of collector on a cloudy winter day will only contribute a small fraction to the heat load for even a very well insulated house. I agree with the idea of using every btu, but how does one integrate this contribution. I could imagine a slab that is dedicated to solar alone, but I can't see how we can leverage the delta if we are putting heat into this slab from another source simultaneously. I would be interested in your solution to this.

I'm really not sure why people are so interested in using this equipment for heating. It seems to me that DHW is really the best application. From what I'v read I'm convinced that Solar heating is better accomplished through passive techniques. Deep overhangs, south-facing windows, thermal shades etc. The inconvenient truth is that a structures highest thermal requirements coincide with the period of lowest solar radiation. At what point is the handful of btu's you can extract from a collector on a cold cloudy day worth less than the energy required to run the pump or manufacture the equipment required to "USE" those solar btu's ?

singh

Second week of

October I finally made the final connections to my Viessman evac. tubes. ( It took six months for me to install )
I just received our utility bill for Nov. '07 and used 74 kwh average daily for the month. ( I have an electric tankless)
Last Nov. ' 06 I used 139 kwh average daily for the month.
The average daily temp last month was 37* Last year Nov.'s average daily temp was warmer at 44* . This I have to factor in since I also heat with an electric boiler.
So I used 47% less electric than last year (average daily for the month), and it's also been colder this year. And we really did not have alot of sunny days, but the solar still has had some impact. (Light's,TV, computer, etc the same use, not burning candles or anything like that ; )
I even got a refund from the electric co, as I overpaid !

I can't wait til SUNNY Spring and Summer !

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hot_rod

nice, welcome to the club

I'd like to see how you piped it in to the heat, etc.

hot rod

singh

Thanks HR

I forgot to mention this is only for domestic. I'm using the Viessmann pump station into (Buderus ST 200) storage tank which pre heats the tankless.
I want to tie into the radiant, but ran out of time. Maybe next season.
I'll try to post a pic later , just looked and realized I don't have any interior piping pics.

Devan

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Bob Gagnon plumbing and heating

Looks good on the roof

Singh. When you tie it into the heat I think you will be able to harvest even more energy because you can collect the solar energy down to about 80 degrees, when you are using it for heating. Thanks for going solar, Bob Gagnon

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escaseadjug1793177

Very interesting, where could I find out more information on those systems and pricing?

Thanks,
Milan

Paul Pollets

Solar

the best sites and products for DHW solar recovery are at

www.thermomax.com or

http://www.viessmann.us/web/canada/ca_publish.nsf/Content/SolarSysteme_ca_english

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Theealchemist

Racking?

Is that a Viessmann racking extrusion or someone else's?
Looks Great!

singh

Rack

That is the Viessmann rack for flat roofs. I had originally planed on doing a side wall install on the south side,and piping was closer inside, but I forgot to tell the wife. She did not want to look them.
With a little modification to the racks, I put them on the roof, piping to and from was more, plus I spent a little more $$ than I had to on the racks. I did not want to expose the piping like that on the roof. I also had a real tuff time finding UV resistant insulation 3/4" wall.

Bob, I am going to tie into the heat, but I question the amount of savings, our cold cloudy northeast winters probably would only yield another 5% energy savings. This morning it was covered in snow.
It is only a 20 tube , more than DHW enough for our small family .

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Bob Gagnon plumbing and heating

Cloudy cold weather

That's what I am talking about. There are a lot of cloudy cold days when the collector will make 80 to 120 degree water, if your domestic tank is warmer than the temps the collector can make, you won't be able to collect anything. I have two collectors and two tanks, there are a lot of times when my domestic tank with evac tubes won't collect anything, but my lower temp tank that I use for heating collects lower temp water, 80 to 120 degrees, all day with a flat box collector. Don't leave any BTU'S on the table. Bob Gagnon

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Paul B_5

Interesting Observation Scott M. Yes in my local due north of rochester NY. My winter solor gains are real low ( less than 15% overall for the yearly total).Even with 60 Evac. tubes I just don't get the brightness or the Sun to do any active heating with this. Not all locations are like this of course so you might be OK but I am not . Paul

singh

Well said Scott

And I do agree with you. I'm only going to tie mine into the heat for two reasons,
1) Because I can. - However ,if I had a paying client with my exact same house, I would advise against it. I try to only work cheap on my own house.
2)Shoulder seasons may be of more value with solar thermal heat than deep winter conditions. For that matter , same goes for solar DHW. So I don't see much need to run additional pumps, just for a few degrees/btu's.
Viessmann does not advocate their collectors for heating , btw.


On a side note: I was thinking about my savings, and I wonder how much of that is because instead of straight 50* well water going into the tankless, I now have a tank, and even if the sun was'nt shinning, that tank now is sending warmer (maybe room temp) water to the tankless. I also remembered after, that I got rid of the water softner, I'm sure I saved some KW's on that. I will keep track of the savings though.

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