# Solar hot water



## TnAndy (Sep 15, 2005)

So my little hoophouse we got a start on late last year, we decided to finish it off this year with a concrete floor, pex tubing in the floor and in the new center raised bed.

Last year, we got the main structure done in the fall, with raised beds around the outer edges. We grew cool weather crops like lettuce, spinach, broccoli, cabbage, etc all winter, but we had to cover them with frost blankets when the weather got in the low 20's and below......which was a lot of nights here.
























Still did pretty good, but was a lot of effort to keep stuff from freezing out.










So, this summer, poured a concrete floor with pex in the floor, and where the center bed will be.....plus went back and buried a loop in the outside bed as well.



















Center bed built, and full of green beans and broccoli....about the end of Sept, 2014.











Photo limit hit. Continued in post 2 below


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## TnAndy (Sep 15, 2005)

Continued....

Built a frame out of 2" galvanized pipe, and 2x2 galvanized angle to hold the collectors. Bought 3 - 16 tube collectors and plumbed them in series.











Here is the completed collector with 48 vacuum tubes, plumbed into the wall of the hoophouse.










Just inside, 120gallon SS tank. Has dual exchange coils inside, I'm only using the one for the collector loop. (black insulated line with silver tape stripes is the "in" from the collector)

The heated water comes off the top of the tank, down into that red Bell&Gosset 1/12hp circulation pump, into the floor pex pipe, and back into the bottom of the tank. Right now, I've just got it controlled with a simple single pole switch. The controller that came with the hot water system does have a relay set up to control a separate pump like this, so once I get a little more down pat as to my heat production, I'll switch the pump over to that so I can set it up automatically.











The 'working station' (green pump) that comes with the system, and the differential thermostat. Measures the collector out temp (T1) and compares it with the temperature in the lower-mid part of the tank. If the collector is 8 degrees C higher, the pump runs (factory default, you can field set to what you want).











JUST got it all hooked up this morning, and the collector loop fill with antifreeze mix. Naturally, we had almost no sun today, so the tank temperature only went from 59C to 65C by the end of the day. Rest of the week is forecast to be a lot better, so we'll see how much heat I can get out of it.


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## ckrv (Jul 3, 2010)

Excellent! This is exactly what I'd like to do, except with a 500 - 1,000 gallon storage tank. I'll be watching for more updates - thanks!

Can you tell me about your hoop frame? I haven't seen that design before. DIY? Plans?

Chuck


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## TnAndy (Sep 15, 2005)

ckrv said:


> Excellent! This is exactly what I'd like to do, except with a 500 - 1,000 gallon storage tank. I'll be watching for more updates - thanks!


I think you'll need a LOT more tubes if you go with that much storage. After a few days, which have been lousy solar days (partly to full clouds), the collector outlet has only hit about 140 degrees max, and the tank about 100. I am flipping the floor pex loop pump on every evening....figuring 100 degree water is still above ground temp, so why not.

But I'm thinking I may have to add more collectors. I'll wait for a few real sunny days to decide.




ckrv said:


> Can you tell me about your hoop frame? I haven't seen that design before. DIY? Plans?
> 
> Chuck


My plans are usually "well, that oughta work"....."and heck, if it doesn't, we'll try something else"......ahahahaaaaa

The hoop frame is simply some 1/2" x 3" strips of white oak I sawed on my mill, laminated them in pairs (screws and glue....Titebond III), put a small block every so often, then added another pair of strips. I built a work table, out of sawmill 2x6's and CDX plywood, in the yard, laid the arch out on it with a string/pencil to suit me, then built them to the line (screwing blocks down for a jig along the pencil line).































They DID have a tendency to push my short knee walls outward after I took the temporary braces off the outside, so I got some 3/16" cable at the local big box store, and looped it inside the arch up about the 9' off floor level. I put the longest turnbuckle I could find, and cranked it to about C sharp (  )....that plumbed the outside walls up nicely. If you look close in the pic below, you can see them. (also in last pic in post #2 above)

Also put a foil faced bubble wrap insulation (4'x25' rolls) on the northeast end, and the northwest kneewall. Wasn't gonna get a sunlight thru that anyway, and the light that does reflect off that aluminum foil REALLY brightens things up inside.

In this pic, I hadn't finished burying the PEX over on the right side bed, because I was waiting the wife to be done with those tomatoes in the back corner. They produced from early May ( a full two months before our outside ones) until late Sept, the date of this photo.


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## myheaven (Apr 14, 2006)

I'm in love with the hoop house.


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## interceptor (Jun 19, 2014)

TnAndy said:


> I think you'll need a LOT more tubes if you go with that much storage. After a few days, which have been lousy solar days (partly to full clouds), the collector outlet has only hit about 140 degrees max, and the tank about 100. I am flipping the floor pex loop pump on every evening....figuring 100 degree water is still above ground temp, so why not.
> 
> But I'm thinking I may have to add more collectors. I'll wait for a few real sunny days to decide.
> 
> ...


A rule of thumb for glazed flat plate collectors is 1.5 to 2 gallons of storage per square foot of collector. I don't know if that applies to vacuum tubes, but you should be able to find a similar rule. The optimum ratio will also depend on the site conditions and desired water temp.


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## ckrv (Jul 3, 2010)

Wow.

TnAndy - great workmanship! I believe I'll follow your lead in the spring. Get any winds where your greenhouse is set up? That's an issue I'll have to deal with. That and not having any oak to work with ;-)

What I do have is lots of sun - like 280 days...and at 7,500' elevation there is not as much of that pesky atmosphere to interfere with the solar gain so I think a small collector will produce more for me.

Thanks again for the description and photos!!


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## used2bcool13 (Sep 24, 2007)

How absolutely beautiful! You do spectacular work, and so precise. How did you learn to build greenhouses? Did you use any reference books?

Thanks for those pictures.


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## michael ark (Dec 11, 2013)

That is a super sweet set up.:rock:


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## tab (Aug 20, 2002)

What do you use for soil in your raised beds? I have used garden soil in the containers in my greenhouse and it isn't quite right, not like the garden. at all. What do you think you have tied up in your heat system, time and money? Isn't it nice to have fresh veggies that you grew yourself in December?


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## TnAndy (Sep 15, 2005)

ckrv said:


> Wow.
> 
> Get any winds where your greenhouse is set up? That's an issue I'll have to deal with. That and not having any oak to work with ;-)


No wind to speak of here....we're tucked in under the eastern side of a mountain the prevaling west wind blows over the top.

Regular metal hoops are probably the way to go anyway....I just wanted to try this to see how it would work out. I'd probably buy metal framing if I did another.


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## TnAndy (Sep 15, 2005)

tab said:


> What do you use for soil in your raised beds? I have used garden soil in the containers in my greenhouse and it isn't quite right, not like the garden. at all. What do you think you have tied up in your heat system, time and money? Isn't it nice to have fresh veggies that you grew yourself in December?


Regular soil, which here tends to be heavy in clay. To that, we mixed coarse vermiculite and peat moss, and made up a Jim Dandy mixture.

Cost in the heating system ? In the $3500 range.


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## TnAndy (Sep 15, 2005)

used2bcool13 said:


> How absolutely beautiful! You do spectacular work, and so precise. How did you learn to build greenhouses? Did you use any reference books?
> 
> Thanks for those pictures.


I kinda make things up as I go. Most construction is simply common sense, and you just sorta build it in your head first, then go do it.


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## Tarheel (Jan 24, 2010)

So you going to grow matter's all winter ?

Looks really good, maybe a road trip in our future.

It's amazing how much better growing under cover makes. Ours out produced the field big time.

Good job my friend !


ETA- went back and looked over the pics, why 2 expansion tanks ? 1 for the collector & 1 for the tank ?


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## TnAndy (Sep 15, 2005)

Tarheel said:


> So you going to grow matter's all winter ?
> 
> Looks really good, maybe a road trip in our future.
> 
> ...


Thanks ! Take that road trip ! Wife is retired now, you get to meet her this time around.

On the tanks: Separate systems. The collector loop is only a couple gallons, and doesn't really need a 2 gallon expansion tank, but it was the smallest one Lowes carried. The collector loop is a 50/50 mix of water and antifreeze. 

The larger tank (5 gal) is for the tank, which is 120gal + the amount in the floor loops (maybe another 4-5 gallons). Probably little over sized as well, but it was only few bucks more.

Now for some pics of the biggest broccoli we have EVER grown ! (I think it's a combination of no bugs, good loose soil, fish fertilizer and good temps)(like you said, under cover is beating out in the garden all to pieces......I seriously considering another hoop house, a LOT bigger this time)


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## Ky-Jeeper (Sep 5, 2010)

Very very nice. had a similar idea on a much smaller scale.


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## tab (Aug 20, 2002)

That's one way to get away from "freezer dependency"!


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## Tarheel (Jan 24, 2010)

Bumping this back up for an update. 

How is it working out ?


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## TnAndy (Sep 15, 2005)

Not as well as I'd hoped.

For one thing, I think I put too much storage tank. I used a 120gal, and even though the collector loop hits 150 degrees, the tank never seems to get above 105-110.

I aimed the collectors due east, because it gets morning sun just as soon as the sun rises above a mountain to the east side of our valley. Unfortunately, with the low winter angle, the sun isn't hitting my collectors past about noonish, because we have a tall ridge with tall trees on our place to that side. I should have scouted the collector location better....but then I would have had to move it quite a ways back too, along with the associated pipe run.

Lastly, I think 48 tubes simply is NOT enough collector surface. I'd have to double it (or more) give the location/orientation. Lesson learned.

SO, my fix is gonna be this:
1. Not gonna add more collector.

2. I'm going to eliminate the tank from the system, and let the collector loop go directly into the floor PEX tubing. It's rated for 190 degrees, and so far, I haven't seen over 150 come out of the collector. The ground/floor temp is in the 50 degree range, so I think, based on a SWAG, that I'd simply be better off to take whatever heat I get out of the collector, and dump it in the floor directly, then let it radiate off as it will.

3. For extra cold nights, like the 10 degrees we had from the Polar Vortex last week, instead of using auxiliary propane, or frost blankets, I'm going to install a wood stove....to be fired up only on the nights it looks like the temps will dip in the low 20's or lower.

4. She MAY just have to let her tomatoes go, and go back to just cool weather crops.

It's all a grand experiment.....ahahahaaaaa


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## BohemianWaxwing (Sep 13, 2014)

I'm mostly posting to follow this thread because your ingenuity and persistence inspire me...  

I did wonder if I was understanding the picture of the PEX going in rightly. Did you just put it in the bare dirt under the concrete? No insulation under? And then build up a 2-3 foot bed over that to plant in? It seems like you're expecting a lot from the hot water in the tubes to get it to make much difference at the roots of the plants. Does the tubing go up into the planter bed?


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## TnAndy (Sep 15, 2005)

The PEX is in the bare dirt under the concrete. My theory is heat travels up at some point, what difference does it make. I'm not going for a 'toasty warm toes' floor. The PEX is far below the center bed, but in the outside bed, it's about 12" deep. The outside wall of the outside bed is insulated with 3/4" foam board.


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## superduty5.9 (Feb 6, 2013)

This is awesome. I would love to do this as I only eat a plant based diet. I wonder how well it would work in Ohio's cold winters?


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## TnAndy (Sep 15, 2005)

It will work anywhere if you build it right. 

For example, we have another small greenhouse built into the side of the mountain (south facing), and used triple wall polycarbonate panels for glazing. It never freezes inside with zero auxiliary or other heating methods.....total passive. Wife picked a tomato off the vines in there today. With just some auxiliary heat (solar, wood, whatever), I have no doubt we could keep it quite warm.

Zonewise, due to our location in the mountains of East TN, we are in the same climate zone as New York State.


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## Tarheel (Jan 24, 2010)

Andy I ended up cheating last winter during the solar vortex thing. I had over 135 tomatoes in the new house. It was designed for no heat except passive. I started out using row covers, then it started to really get cold so I added water barrels as a heat sink. That helped but some nights I was getting real close to freezing.

I ended up adding a wood heater for those teen and single digit nights. I would of lost it all if I had not done that. I'm going to build a heater this winter and may add a coil to heat some water for the barrels. I'm really not sure if I'll end up with too much condensation then. May even add another layer of plastic. Time will tell. Let us know how it does with out the tank in line.


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## TnAndy (Sep 15, 2005)

Yeah, I added a 2nd layer of plastic with an inflator fan (from Nolts, thanks !) as well.


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