I have a 50X37X13 foot garage, 2X8 walls and it is insulated and sheet rocked. I have the opportunity of buying 3 older 4X8 foot water solar panels, my question is if I ran a length of baseboard heat in the garage with an expansion tank and a circulator pump , would it add some heat during the winter? It takes very little oil to heat the barn for the winter but at the cost of oil I would like to only use it when I want to work in the garage. I just want to keep it above freezing. Any idea how much heat you can get out of the old style solar panels?? Panels will cost me about $50.  each and may include pump, expansion tank and thermostat.
I am located in the Hudson valley in NY, its cold!

You're going to need a whole lot more heat for a building that size than you'll be able to squeeze out of 125 square feet of flat plate. Most older flat plates are still pretty efficient, but you don't have nearly enough for it to be useful. (You could do a pretty good job with those on a well sealed well-insulated ~300sf room though.)

To know your real needs you'd have to do a manual-J type heat loss analysis to find the true order of magnitude (there are several freeewares out there- google 'em.)

Assuming you have a reasonable southerly exposure, you'll get a lot more bang per buck out of a large integrated thermosiphoning air panel system:

http://www.builditsolar.com/Projects/SpaceHeating/SolarBarn.pdf

This type of system is still the cheapest way to add a lot of glazed-area for heating large open spaces. It's not thermostatically controlled- you'll cook some days if you don't open some doors & windows, but if it's an otherwise tight building you won't need to spend a fortune on freeze-control or space heating.

Thx. I looked at the barn link you posted, I could not cut up my finished building, just no way. My walls are line with storage cabinets, sounds like I need to find more solar panels.

I would say go ahead and buy them and start experimenting. It won't get you a lot of heat, but more than nothing and it is a way to get your "feet wet" in solar hot water. Although that might be a bad thing leading you down a path buying more and more solar items :) But seriously for the cost you can experiment, see what you get and how it works. Most of it will be your time and learning as you go.

To have any chance at all, the garage needs to have well sealing & insulated garage-doors, and an insulated slab (at least at the edge) makes a huge difference too. But you may be able to freeze-control the place with 125square feet of collector area, if not exactly heat it up to human-comfort temps in the middle of winter.

Since you don't want to cook the place in summer, DON'T mount them at the pitch usually recommended for solar HW heating (since that's the pitch for maximal annual gain, which happens mostly in the summer, while you're looking for the maximal WINTER gain, or close to it.) For most of the NE, mounting them vertically on a due-south facing exterior wall is close to optimal, and you don't end up with losses from snow cover (really anything over 60 degrees from horizontal will shed snow well, but vertical is guaranteed, even at low temps.)

See:

http://www.hawaiirdp.org/hetl/AdvisoryGroup/tilt-az-paper-3z13.pdf

Look at Fig 9 the chart labeled L-w 36 is most-appropriate for the Hudson Valley. Note that even if mounted vertically (90 degrees) the annual capture is only degraded only ~30%. But in winter the sun is much lower, and the snow reflection radiation much higher- the degradation in performance is likely to be under 10% for when you need/want it the most. (And most degraded when you don't want ANY heat, eh?)


The simplest possible system would be a glycol-loop directly through your hydronic radiation (probably baseboard- lots of it!) and a differential thermostat to kick on the pump whenever the panel output is greater than ~10-20F above the return water temp.

Flat panels lose efficiency pretty rapidly with increasing delta-T between the water temp and the outdoor ambient temp:

http://www.builditsolar.com/References/Measurements/Collec1.gif

At dawn, when the temperature of the panel is about the same as the outdoor temp it's scavenging 70% or better of the incident radiation, but if you need 100F water and it's 0F outside, you'll be only collecting 40%. The key to getting efficiency out of it is keeping the operating temp as absolutely low as possible. Ten degrees can make as much as a 25% difference in performance when you need it the most(!)

Delivering the heat to the inside at low water temps is an issue- for lowest temps (= highest collector efficiency) an insulated radiant-floor slab is the best option, but I'm going to assume that isn't happ'nin' here. Fin tubed baseboard is designed to work with water 70-120F above the room air temperature, but by doubling or tripling the amount you'd normally use in space heating (typically designed for 160-180F water, 70F room temp) you can still get a reasonable heat transfer out with water temps under 50F over room temp. (So, when it's 40F in the room, 80F water still delivers some heat.)

Read up a bit on hydronic heating design and solar design- figure out what you can get out of craigslist surplus fin-tube & solar collectors- I'm sure you can figure out a way to get SOME useful heat out of the collectors.

Thx lots of great info! Sora sounds like fun too, will keep my eys open for more panels. Barn is TIGHT with insulated door (2"blue foam And two 2x8 foot single glased windows, the rest is r30 and rocked.

It's worth starting with the Keep-It-Simple-Stupid (KISS) approach with the panels you've already lined up.  If your collector area grows to greater than 10% of the floor area of the building you'll likely need a more sophisticated control strategy (and possibly some thermal storage.)  If your goal is freeze control and bumping up the baseline temp indoors to save oil, the KISS approach will probably get you there with the panels you have.  With twice as much panel area you may develop overheating issues on the warmer sunny days, particularly in the fall.

You may want to do the math, figure out the optimal heating radiation per unit glazed area is.  If the panels are SRCC rated you can probably get more precise performance data, but otherwise assume that with a decent single-speed hydronic heating circulation pump (not some tiny solar hot-water tank sipper) you can keep the temps low enough on the solar panels to suck in more heat into your cool-to-chilly space for freeze control on cold but sunny days.  (Hopefully the building coasts on it's internal thermal mass OK overnight, doesn't drop from 60F to 40F even on 0F nights?) 

The not very well researched gut feel (and I've not designed & built anything quite this crude, mind you) is that it'll be somewhere between 8-12" of fin tube baseboard per square foot of collector area.  (At retail of ~$12/ft that's not cheap, but surplus/used etc. it can be had for less- a LOT less.) Scratching on the back of the napkin, figure the fin-tube is probably capable of delivering something like ~100BTU/hr per linear foot with water ~40F above the indoor air temp (more with bigger delta-T, less with less).  But look it up, eh?  (Most won't spec it below 140F, but some do. Graph it from the 140-180F numbers that are all based on 70F room temps and guesstimate what it'll deliver for smaller delta-Ts to your cooler space.)  On a clear bright sunny January day with maximal snow reflection you may be lucky enough to have ~250BTU/square foot shining on the collector (probably never much more than that), but the first 30% will be lost to reflection & re-radiation out the glazing, and more is lost from heat conducted off the panel when it's wicked-cold out, so figure on being able to deliver something like 40% of those 250BTU,  or ~100BTUs per square foot of glazing to your radiation (order of magnitude) as 80-100F water on a 0F sunny day.  (Shoot me if I'm off by 50%, eh? :-)  Use yer OWN dang napkin! :-D )  You need sufficient radiation dump into the room to keep the output of the collector under 100F or the collector efficiency just won't cut it enough to be useful.

Of course, as the room warms up the warmer the water needs to be to keep delivering that heat, which cuts down on the collector efficiency.  But as it warms up outside the collector efficiencies go up too.  You can drive yourself nuts and model it against some panel & fin-tube manufacturers' specs along with regional weather & insolation data, but that's the order of magnitude.

Dana1 thx again, the barn holds heat like a ice box, 45 inside at night -6F outside and 40 inside in the morning, I have allot of heavy mass in the barn so it takes a long time to warm it up but it takes a long time to cool down. Now another question for you, can I just shut off the circulator pump  for the summer? I do not want to add heat in the summer, if I can not just shut it down is it OK to drain the system for the summer?

Unfortunately you can just shut it off because it can actually start to boil the water and crack and break things. Maybe if you used something that wouldn't boil at higher temps but I wouldn't recommend it. Your best be it to somehow cover the panels, it wouldn't take much, an old sheet, a painters tarp, a thin piece of plywood. The other option would be to tilt the panels so they are not exposed to the sun or face down.

Good to add heat to the barn, two thoughts on temperature control, best add a drain down tank, now you can cycle your heat on your terms, you wont need as much glycol, system will sty off in summer. More cost, $4-500. easy to expand on.
Plan B place panels on a south wall and extend the overhang, natural shade in the summer.
still may need to drain in the summer.
Consider a radiant wall or slab for heat mass.
Dan

If they're mounted vertically, the drop in gain during the late spring/early summer will be significant, if not as significant as the seasonal drop in heating load.  You'd still need to put in an over-temp thermostat (cheap line-voltage snap-disc types work) in parallel with the differential thermostat, turning on the pump when the panels hit ~200F or so to keep it from boiling & popping it's cork on a sunny day by dumping heat into the system.   (Snap-discs usually have 20-25F of hysteresis, so the pump will run several minutes at a time, but won't short-cycle & burn up.  Be sure to use one with sufficient current ratings to handle the pump's startup surges.)  You don't say what you're using for a differential thermostat, but it's possible to get something with an overtemp setpoint as well.

Still, shade works, eh? ;-)  Unlike evacuated tube collectors- flat panels shed heat pretty well once you take the direct sun away.  It doesn't have to be perfectly dark or 99% reflective, just enough to cast a good shadow.

It'll likely be overheating enough by mid-May that you might want to cover half (or all) of the collectors with something.  The shade design need not be elaborate- a simple tarp will do, just be sure it's secure enough that it doesn't blow away during a thunderstorm the first day you're out of town on a 2 week trip, so you won't come back to a 140F barn that you're unable to get down to temp for the rest of the summer. :-) )  If you're feeling extravagant, a lightweight sliding door will let you easily adjust the available collector area.  Whatever the method, just be sure that the overtemp-sensed panel gets shaded last.

OK, the panels will not be vertical but very steep, I plan to install them on a 13.5-12 pitch roof, no snow will stay on panel.
I stood next to barn with compass, it indicates the wall is facing due south or real close to it. But at noon I held up a pencil and noticed the shadow was not centered behind it, not sure what that means, I thought 12 noon = no side shadow, "only the shadow knows" (had to say it). Have not picked up panels yet,so do not know what type of control is on unit.
Can not cover panels as my neighbors would bitch, they hate the idea that I am installing panels that they will see.

Barn stays beautifully cool in summer, I do not want to add heat to it then, so I hope to just drain system for summer, unless anti freeze will be enough to keep over temp from occurring in summer.
Draining panels will be pretty easy for me, so I hope this has no negatives associated with this practice.

Draining a system isn't that tough, but filling & air purging it annually can be a pain in the butt. Also, if  you drain it and let it stagnate hot it'll be VERY hot (a few hundreds of degrees) tilted at an angle in the summer sun. It may/may not damage the panel, but it's a thermal stress, nonetheless. I strongly advise against it, particularly if they're mounted on your pitched roof.

In a space-heating application putting them on the roof is counter-productive at 42-44 degrees latitude  They will have lower gain when you need the most amount of heat, and blast away during October & April.

Read & comprehend the various aspects and consider what you need in a space heating application:

http://www.hawaiirdp.org/hetl/AdvisoryGroup/tilt-az-paper-3z13.pdf

Mounted with 40 degrees of tilt facing due south you give away a huge amount of snow-scatter gain in January, as well as a some portion of direct solar gain during most of the mid winter-day.  Most of the day the sun will be low enough that a large fraction will be reflected off the outer surface of the glazing.  Tilted collectors only make sense when you're looking to maximize total annual output (the bulk of which happens between May & August).  This is reasonable for HW heating (or photovoltaic), but just plain WRONG for space heating. With a vertical mount you're close to ideal for maximizing the output during the HEATING season. Mounted vertically there will be 2 performance peaks, one in the early fall (when you may not need it much) the other in late winter (when you probably DO need it) and mid winter will be about as good as it can be done with a flat panel, plus you can get a significant snow-scatter bonus. Mounted on the roof you take the most signficant performance hit (from an already small gain) when you need the heat the most.  Mounted vertically you take the biggest hit in gain when you don't need it AT ALL.

Many active solar space heating systems are mounted at an angle in order to meet the language for some ill-considered solar subsidy clauses more appropriate for hot-water heating. Nearly all of those systems need active summertime heat-dumping to avoid system damage. This is something you'd rather not have to design in if you don't have to (and you don't REALLY have to if you're willing to add/subtract shade during the off season.)

Reference:

http://solarairheating.org/pages/intro-to-solar-heating.php

"Figure 3 graphs the incident radiation on a horizontal, vertical and a 60° sloped surface in Ottawa and illustrates that a vertical collector performs close to that of a sloped collector without any ground reflectance. When ground reflectance is included, a vertical wall will produce from 15% to 30% more heat than a collector at a 60 degree angle. For heating of buildings in northern latitudes, a vertical wall is therefore the preferred surface for mounting solar collectors."

(emphasis mine)

Anywhere in the Hudson valley, vertical mount is what you want/need (Albany is just 3 degrees south of Ottawa.)  In non-snowy climes latitude +15 degrees is often used of a rule of thumb for space heating, but that too is wrong, most of the time- a theoretical guesstimate based solely on solar geometry, zero scatter input and an assumed heating season begin/end.  Even in the desert SW in the middle of the summer nearly half the gain through the windows is from reflected heat(!). Latitude +30 degrees is probably a better rule of thumb, and the further East or West of due south you're looking, the steeper you need to be.

Dana1, holy cow,I HAD IT BACKASSWORDS,I thought it was better to mount on roof at an angle! I can mount them on my side wall, vertically with no problem at all, the wall is 12 foot high x 50 feet long and not a window on it, this will make installation and adding more panels sooo simple compared to the roof deal. I will be able to make covers for the panels and install and remove them with ease. I never considered snow reflecting on the panels giving me more heat, can you tell I am new at this? I will look at the sites you listed , thank you very, very much. I just converted my house to Geothermal heat and can not get over how well its working so the barn and solar panels are my new project, I would see panels all over the place 15 years ago, now I wish I could find 10 more of them. I assume you live in Ottawa , is your weather about the same as lower Hudson valley or allot colder?

If you plan to do the installation yourself, then you might benefit by knowing about this web site:  www.quickflashproducts.com

I think it is important that the lines from the wall mounted collectors be flashed well so there will not be any leaks.

That is what I was talking about as well. I recently was talking with the people at Thermal dynamics in Nova Scotia and they have a solar wall, 30 4x8 panels vertically mounted, on the South wall, heating 8,000 sq ft, solar PV pump and glycol system that they do not drain out in summer, they simply turn it off. to cool.
This is a commercial curtain wall look, very attractive. In your application you can add on as you find collectors.
I find what Dana found about vertical wall in heating very solid and supported by logic as well, very good Dana,
This is among the directions society needs to be looking.
Dan

Dan thanks, I did not put it together in my mind from your first note, until I read Dana
's note. Now I would love to find a bunch of panels (cheap), as it does not sound like three will do a whole lot, not that I need a whole lot, I will take what ever they put out. pictures attached showing barn and 50'wall, panels would be on wall next to RV, plan would be run baseboard long that wall under wall cabinets that were not installed at the time this picture was taken.

I live in central MA (about the same latitude & weather as Albany), but the website reference talking about the snow-boost was referring to idealized angles for Ottawa, which is why I pointed out the similarity of latitude.

For your barn project if you go over ~200square feet of glazed area you may have to put in more sophisticated controls (or tweak the shading more often :-) ) to keep from overheating- particularly in the fall.  As long as you have overtemp controls on the panels overriding other controls to avoid the steam-explosion potential you can put a setpoint thermostat in series with the differential thermostat. 

You can still use the hydronic baseboard loop as the heat dump and not run a huge risk of overheating the barn, since the panels are re-radiating a large amount of the heat:  When the panels are cooking at the 200F+ overtemp trigger on a 50F day that's a 150F delta-T, where the collector is only musters ~25% efficiency- literally half what you'd pull in with 100F collector temps (which is where it might be running when you're still wanting to add heat on a 50F day to get it up to 60F+ inside.)  You'll likely know the week when it's time to start shading the panels though.

Have you done a full solar survey of the southern horizon?  I see some trees in the pics, but there may be other features to deal with as well.  Plug in your zip code here, and start measuring/plotting with your back to the S wall of your barn.

http://solardat.uoregon.edu/SunChartProgram.php

I took the liberty of entering an Albany zip code to spit out these:

http://solardat.uoregon.edu/download/temp/30893256.pdf

http://solardat.uoregon.edu/download/temp/65629247.pdf


Which should be close enough.   Try to measure your offset from due south carefully too, eh?  Plot the high points of your obstacles directly on the chart to see roughly what date they start cutting into your direct solar input.

Deciduous trees don't genrally cut much out during the heating season, but conifers do.  If you find you're getting less than 75% of full sun during the heating season you'll have to start adding panel area to keep the performance up.  But first shot, if it's sunny this weekend, go out and observe the side of the barn in question at several points during the day- is there more than 10%  shading at any point during the day? All day? If not, don't sweat it- if it's roughly south, it'll do just fine.

Thx will do all of the above.