Solar Heat for Shop

[Brian Harnett]

When I built my new shop in 2010 I had solar hydronic heat in mind. So I ran 6 heating zones of 500' each of pex pipe before I poured the slab.

Last weekend I finally hooked up my first hot water solar panel to the system. It works better than I expected with just one 20'x8' panel I have it hooked to my center two zones a 20x40 area, the slab in the two days of sun this week went from 52 to 64 at an average temp of 59 not bad for just two days. The slab is 6" thick with 3/4 foam insulation under and 2" around the perimeter would have liked to go 2" all the way but the cost for 2400 sq feet was to much.

The absorbers for the panels are pool solar heat panels fairly cheap and quick to install the glazing is twinwall lexan the stuff used on greenhouses, the pumps are brushless dc running off a 100 watt photovoltaic panel the whole system is independent of external power we usually lose it for a week in the winter.

In the summer I will pump the heat into my wood kiln

I plan on making two more for the shop and for hot water in the house next.

For an existing shop without floor heat radiators could be used for heat transfer

Since those pictures I have taken down the trees that were shading except for one.

http://i.imgur.com/2Iow3jR.jpg

http://i.imgur.com/LoaCxrF.jpg

http://i.imgur.com/juBbv6j.jpg

[scottp55]

Nice Brian!
3,000sf slab here with 4,000' tubing(house and shop) went 6" slab like you except 12" in 33x8' Greenhouse(or "plant torture chamber:)" ). Didn't go solar because I wanted the trees for summer. Even with 118K propane boiler it takes 24hrs to go up 12F, but lost power for 3 days in '98 and temp only dropped 5F, so it's a good thing to have thermal mass.
I wouldn't worry about the 3/4" underneath, the important part is the thermal break from slab to frost wall. If you insulated all the way to the footing, then you simply added about 3.5' of thermal mass:)
I threw an hour worth of heat into the floor yesterday at 6 AM, and had 25F night and it was still 65F this morning. Sun is pretty low in the sky now, so very encouraging---By March you'll be opening the doors a crack like I have to do in the greenhouse to keep from overheating:)

[Brian Harnett]

Scott I like having trees, I have plenty behind the shop and we have them all around the house just down the hill, the shop is r 38 with good venting stays cool in the summer 3/4 of the south roof has 9 KW of photovoltaic panels on it shading the roof and producing my power.

I put more on the grid in the summer than I use, the house is also running off them.

[scottp55]

Brian, Solar engineer who designed my trusses wanted me to go active solar, but kind of liked the phrase "Passive Solar-Active Owner" :)
Besides, I can always cut them down- so left them up. Good thing I did or I would wicked overheat as I never got the water tubes and storage tanks installed in greenhouse for mass.
Good on R-38 as insul is key, used overstuffed 2x6 and 2x4 Canadian "Wrap and Strap" walls an 24"blown in ceiling.
Just wish I could change my Oaks into Maples with a magic wand so they wouldn't be the last trees to bud and last trees to shed(acorns on greenhouse glass can be a distraction too:)
Solar hydronic is the way to go if you can! Even burning propane, people are surprised at the energy savings. Now if I could just figure out how wheelchair shovel the snowbank that builds at the kneewall and prevents the snow from sliding all the way off the glass after a few storms:)
68F this morning and only 2 hours of 82F water pumped through floor so far.
What temps are you getting on on your feed and return?
How close are you to Solar South on that wall?
Congrats on your work!
scott

[Brian Harnett]

Scott it is almost perfect solar south I had that in mind when I put the buikding up. With 2 zones of 500' 1/2 pex running temp is 80-90 in the tank and floor input, the floor return was 60 same temp as floor so all the heat is getting absorbed.

The panel outlet temp is anywhere from 100 to 115.

I bet if I had it done two months ago the floor would be nice and toasty

November is usually a cloudy month here it usually starts clearing in mid dec though feb besides the snowstorms

[scottp55]

Good on South---Most don't plan, had to kitty-corner house 6 degrees east to follow code for well and septic here. Sounds like 2 good days will get you to 70F if tubing is at bottom third of the slab. Insulated storage tank? 1/8hp circulating pump?
Yup, return is low-so she's sucking it up:)
Output sounds about right for a hot tub for after those long days:)
If properly covered and insulated not much loss-just keep covered as humidity caused me problems in the greenhouse wood if I didn't.
nice thing about vertical is no brushing snow off:)

[scottp55]

Oh, With whole floor heating--if floor was "Toasty" you'd cook!!
Only place my floor is warm is the first few feet of concrete before tubing reaches the 2" foam it was stapled to.
Otherwise it's comfortably cool to skin-somewhere around 72F.

[Brian Harnett]

Don't have a storage tank just the mixing tank on the wall the whole system is about 12 gallons water antifreeze mix, I plan on a diverter pump to go into the wood kiln when it gets too warm.

I am running 4 3 gallon per minute brushless dc circulator pumps, they run off a 100 watt photvoltaic panel right under the thermal panel, when the sun shines they run, I have a temperature snap switch that turns the zone pumps on when the tank hits 80.

Two pumps for the panels and one pump per zone.

[scottp55]

Diverter good idea. 8 zones here and you can see caps off flow valves (shut Off) as they got the least travel so got too hot, and heat transfer from the rest of the slab turns out to be sufficient for those rooms. You can see shop loop was a last minute deal as they put a staple through the the first 20' of hose so had them toss it into shop(Glad I did now:)
Grundfos runs almost continuously to even out the heat as the Usonian Red concrete really soaks up the sunshine and the North rooms never get any(Sun Tubes for light).
You can probably start running the tank at less than 80F and still get a lot of benefit.
Don't overshoot your temps or you'll be sweating in a tshirt for days:)
My mixing valve is hooked to exterior thermometer through a sensor that figures out the DeltaT and moderates it.