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Mike Jay wrote:Hi Jared, welcome to Permies!
So are you proposing a solar water heater collector inside the greenhouse to heat water tanks that are also inside the greenhouse? That's interesting and I'm not sure how much it will do. The greenhouse will only accept a given amount of sunlight (energy). Whether it hits the collector and goes into the tanks OR if it just hits the tanks directly (or the floor or plants), the same amount of energy was transferred into the thermal mass of the greenhouse. But, you may prefer it to be transferred to you tanks instead of the ground, since water is a better thermal mass. So if you goal is just increasing thermal mass energy accumulation, it should help. But day in and day out, the average temp of the greenhouse would remain the same (I think).
If the collector is outside the greenhouse and absorbing energy that wasn't going to hit the greenhouse, then I think you get a better boost.
Or if you want your thermal mass to be hidden on the North side of some banana trees where the sun can't hit it, this would be a way to transfer energy there without putting the tanks in the sun.
If your high tunnel runs E/W, you may want to consider making part of the North side of the tunnel out of an insulated material. Holding heat in would really help.
Walt Chase wrote:Is this going to be a NRCS high tunnel? If so, I imagine that what your are proposing would be "out of contract". If not, Look into solawrap covering. It is like bubble wrap for greenhouses. A bit spendy, but when we build our next house (already have the property) my GH will be covered with it instead of traditional GH poly. Supposedly will last for 20 plus years. If not that look at using a double layer of conventional GH poly and use a blower to inflate between the two layers. That coupled with more thermal mass in the HT and maybe even a wood stove could let you grow several extra months and possibly all winter depending on you climate and winter severity. I would suggest a RMH, but have no personal experience with them, especially in a GH. Could be a viable option as well.
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Jared Van Denend wrote:I read that 55 gallon drums often do not fully heat in greenhouses due to their size/thermodynamics. I figured the solar collector would circulate the water, fully heating it (and hopefully heating it more).
I'm not attempting to raise the daytime temperature of the greenhouse. I would like to simply add thermal mass for nighttime temps.
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Zone 5/6
Annual rainfall: 40 inches / 1016 mm
Kansas City area discussion going on here: https://www.facebook.com/groups/1707573296152799/
Mike Jay wrote:
Jared Van Denend wrote:I read that 55 gallon drums often do not fully heat in greenhouses due to their size/thermodynamics. I figured the solar collector would circulate the water, fully heating it (and hopefully heating it more).
I'm not attempting to raise the daytime temperature of the greenhouse. I would like to simply add thermal mass for nighttime temps.
I'm struggling with this in my mind as well. I've read that if you use one gallon water jugs for thermal mass they heat up fast and cool off fast so you lose the heat back to the greenhouse before the night is over. 10-20 gallon jugs were suggested to hold and release heat in about a day which would be perfect to offset the lack of sun at night. 55 gallon drums sound like they are more of a 3 day gain/loss so they can help out over cloudy stretches.
In my mind, it makes sense that circulating water into the drum from an efficient solar collector would boost the temp of the water and give you more heat to release at night. But "conservation of energy" is telling me that the amount of energy into the building is the same either way. So I'm guessing that with the solar collector inside the GH it would reduce your daytime temps slightly (by hiding that energy in the drums) and increase your nighttime temps by allowing the extra energy in the drums to come out then. Overall, average GH temp would be the same but it would help by leveling the daytime highs and nighttime lows.
Another thermal mass collection idea I had (and probably many others) is to put some black pvc pipe at the highest point of the greenhouse and circulate water from it to your tanks. All day the sun would hit that pipe (solar collector). Plus the rising heat of the greenhouse would thermally warm the pipe as well. That would let you store that heat before it escapes through the thin greenhouse plastic. At night you'd have to shut off that pipe so it doesn't work in reverse.
Insulation ideas:
If you do the double poly glazing with the blower, maybe you can insert some packaging peanuts between the layers on the North side. Or fasten some 1" styrofoam to the ribs between the layers.
You could fasten styrofoam to the inside of the ribs on the North side and cover them with a white or reflective material to bounce light back down to the plants.
Concrete curing blankets are another possibility. Just drape them over the GH on the North side and tie them down.
Vern Life wrote:Hi Jared,
how much space are you allocating for the solar water heater ( I guess the water storage/ transfer portion)? I'm moving towards the GH phase of our build and have been thinking of this as well. I've thinking of using the black barrel wall idea as a winter heat storage mass and summer drought water supply that will serve as a work bench of planter shelf (hoping the warmth will add additional seed germination awesomeness). For the water heat however I've been playing with two ideas, the solar gain ( basically the high pressure black hose on the roof, I already blew up the black garden hose) and the compost pile water coil. The compost pile heater coil has been on my mind for the past two years for emergency hot water and it's thermal properties while providing ample compost for the spring planting. I've seen compost piles in corners of greenhouses or in one section that keep the GH mild even in snow.
Follow along as we start an urban farm in our town. Currently designing and researching: https://www.wildernessmade.com/our-culture/category/urban-farm/
Dan Grubbs wrote:Here's a possible different approach.
I know running hot-water tubes through the planting beds may seem like a budget buster, but would be more efficient to focus on soil temperature than ambient temperature? One could collect solar heat in tubes in a panel or heat from a large compost pile and run the tubing through the bottom of planting beds so that you spend your energy only heating the places where the plants are and not all that cubic feet of air. In extreme low temperatures, use row covers to hold in heat and deter frost. A small solar powered pump can circulate your warm water through the system.
There are some other posts on permies.com that touch on this topic extensively.
Here is a video of a small high tunnel with double layer and small blower. The person in the video is showing about a 60 degree gain with the double layer. https://youtu.be/LlEczaE0-eg
Here are some interesting ideas presented here by Verge: https://www.youtube.com/watch?v=b1p-Dm1bUjs
Follow along as we start an urban farm in our town. Currently designing and researching: https://www.wildernessmade.com/our-culture/category/urban-farm/
Hans Albert Quistorff, LMT projects on permies Hans Massage Qberry Farm magnet therapy gmail hquistorff
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frank li wrote: and a (edit, minimum) ratio of 15 to 1 interior floor area to perimeter length
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Mike Jay wrote:
frank li wrote: and a (edit, minimum) ratio of 15 to 1 interior floor area to perimeter length
Hi Frank, can you explain this ratio? I've heard that a good ratio for passive solar greenhouses is a E/W length double the N/S width. I followed that on my greenhouse which is 40x20. That gives me 800 sqft. If the perimeter should be at most 1/15th of that, I calculate a maximum perimeter of 53 feet.
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Mike Jay wrote:Gotcha, so the only way to hit that ratio is to get commercially big. I just ran the numbers for my greenhouse and failed but I didn't scale it up. Thanks!
itsmesrd
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Jared Van Denend wrote:We are building a high tunnel in WA (zone 7b). The main purpose of the high tunnel is to get a whole bunch of starts rocking early spring... however if it is there we would like to grow whatever we can in it all winter. So we are looking at heating options.
We are going to build cold frames inside the greenhouse which we will remove and place over some beds in the spring. This got me to thinking if every layer of greenhouse material bumps the zone up... how about a solar water heater inside of a greenhouse.. heating up our barrels.
Has anyone done this? I know theoretically it should work, but I'm wondering if the juice is worth the squeeze. I haven't found any info about this type of setup on the web.
Aubrey at
PyraPOD.com
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Heat your home with the twigs that naturally fall of the trees in your yard
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