It's all Plain to Sea

[randy]

I am planning a small commercial hydroponic greenhouse operation which will include several very interesting ideas brought together around the use of the SHCS. This will be a family owned business, part hobby and part secondary income. We hope to grow a small variety of vegetables and market them in a modified "community supported agriculture" model.

I thank Mr. Hobbit for his generous sharing, great common sense and inspirational commentary. In opening this subject I invite all to share in their knowledge and imagination as I enter the final stages of planning and begin construction of this project at first opportunity in the spring of 2009.

I have a purchase agreement for the land, financing from the USDA and have made it through Planning and Zoning. I have to make it past the city council and obtain a USACE wetland permit and we are off to the races. I see no great impediment to these last two milestones.

I have selected the worst possible 7 acre parcel I could find for my project. About half is a certifiable palustrine wetland with springs, directly under the footprint of the proposed greenhouse, actively depositing travertine at the surface. There isn't two feet of soil over the travertine anywhere on the parcel. The site is in Southeast Idaho at about 5,500 feet with protracted winters and heavy snow fall.

Infrastructure will consist of a 48' x 24' headhouse with a 45' x 25' x 15' half quonset section attached to the south wall of the headhouse and a 70' x 42' 15' full quonset section off one end. This will provide a little over 4,000 sq. ft. of greenhouse floor space.

Excavation, drainage and backfilling of a suitable material with the SHCS installed will be difficult and costly.

I am setting myself up for a onslaught of critical comments and probing questions. As I attempt to defend this project and answer the tough questions I am hoping to troubleshoot and polish the final design while time and opportunity remains.

[randy]

...financing is in place, the land is purchased, a well is drilled, USACE wetland permit secured and construction will begin as soon as weather permits.

The USACE wetland permit is required because I am purpously building on top of springs. These springs are outgassing CO2 and also have a water temp of 60d F. I plan to utilize both of these resources.

The greenhouse dimensions: 85 x 42 ft. The internal air volume: 40,290 ft^3. The SHCS will require 5,580 ft of tubing. Auxilary heating will include 2 ea 5 ton water/water heat pumps and a hydronic floor heating system. I estimate my costs for heating will be ~25% of a conventional system. Payback on the SHCS will be about 3.33 years. The payback period is a little long because of an elaborate plenum system in my design.

There will be an upper plenum and a parallel lower plenum of 12" HDPE corrugated, perforated pipe run across the width of the house. 4" HDPE corrugated, perforated tubing will be inserted at 1.5' intervals along the length of the lower 12" plenum, run out perpendicular 15', looped back to run 15' perpendicular into the upper 12" plenum. This configuration will form an elongated horizontal U loop on either side of the two plenum pipes a total tubing length in each loop of 30'. Each set of parallel 12" plenum pipe will carry 60 of these 4" tubing loops. The house will rquire three such plenum systems.

The plenum system will allow three modes of operation: recirculate, cooling and heating. Intake for the system will be near the peak of the house (15 ft). Output will be distributed across the width of the house, through perforated poly vent tube at the base of each row or at 5 ft intervals. Air flow will be from floor to ceiling and replace the need for horizontal ventilation. When no heating, cooling or humidity control is needed air will circulate through a bypass (recirculate). When heating is the required mode air will circulate first through the lower plenum and exit through the upper plenum. When cooling is the required mode the flow will be reversed. This will take advantage of the 60d F water and ground temperature at the bottom of the SHCS.

I will install a liner under the SHCS to collect condensate for reuse. Anyone have any idea what % of the water might be captured/recycled this way?

[Hex]

Hi Randy
Thats a huge project, the bonus of having warm springs on tap is enviable
Regarding the water collection from condensation you should be able to get a rough idea from the thesis and scale it to your greenhouse size. It may turn out to be a lot of water.
I like the idea of the 3 seperate shcs systems, it should give you plenty of flexibility and help keep the fan requirements within bounds. By my reckoning three blowers capable of 5000cfm @ 260Pa could provide around 20 air changes an hour.
It`ll be interesting to see the results when its finished

[mrhobbithhnet]

Randy,

Good thinking on your design! You'll be the first one I've heard of in a commercial scale doing a recirculate plan. Did you post your SHCS Calculator at Numsum? I'd like to take a look at it.

I am not entirely clear on your piping runs, got a sketch?

Water collection... here's a chart you can use to read off the # of lbs of water in air at different temps and RH. Just hypothesize your input and output numbers, and subtract the amount of water going in from the amount coming out to get your total water weight gain for any one volume of air. Multiply that poundage by about 950 BTU's and you also have the amount of heat extracted for that given volume of air reduced in temp and RH.

I typically went from 90 deg/80% input to 60 deg/85-90% out. If I recall right, that could be over a lb of condensate per 1000 cuft of air that is run through the system with that delta T/RH. At 5kcuft a min, you'd be looking at close to half a gallon minute, 30 gal/hr, 100-150 gallons/day. Of course that only happens if you are putting that much into the air! No magic here, just some interesting consequences.

The heat pumping idea has always seemed a no brainer to include somewhere in a comprehensive system. Package plants are creeping into 500% efficiency range now, and 20-25 year life spans to boot.

Oh, and do keep in mind that if you don't have enough light to heat the place, you probably don't have enough to grow anything in the winter either. Degree days and tech hardly trumps nature when it's short on light!!! Light is actually going to be a much, much bigger deal in the decades ahead. We are, as of 2004 readings I believe, down to only 75% the light we got in the 70's. Turns out the Greenhouse Gases may be keeping more in than we thought. It's heating up even though there is less light hitting the ground!
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[Hex]

Hi Randy
Is there any chance of a drawing to show the layout, i can picture the 12" lateral tubes with the 4" tube loops etc but i`m not sure about recirculation feature.

Like John, i assume it creates a semi close-circuit of the shcs input and output causing a percentage of the air to continually loop around the shcs tubing?
With hindsight, as you mention "bypass", it may be that it simply bypasses the underground tubing entirely so the shcs fan doubles as a HAF/recirc fan to move the air around in the gh when no cooling or heating is required?

[randy]

I have images in several forms (AutoCAD,pdf,wmf,bmt) but I do not know how to attach them to a post. I could e-mail them.

[Hex]

Hi Randy
I use freebie online photo albums for pictures, something like photobucket.com or imagecave.com
The only downside is when they have an upgrade or similar revamp they tend to lose them which messes up the links

[randy]

Link to the SHCS general layout. Let me know if this does not work.

http://i204.photobucket.com/albums/bb26/duren67/GH/VentLayout.jpg

[Hex]

Hi Randy
The picture link works but i`m none the wiser to be honest

[randy]

Sorry!

The plan view is at the upper right, the side view is at the left, the end view is below the plan view and below that is an exploded detail of the distribution box components as well as some other stuff.

The 12" and 4" tubing should be recognizable from the drawing. The floor of the greenhouse is the upper dashed line in the side and end views. The greenhouse frame and poly cover is solid green in the plan and end views. The confusing part would be the distribution box. I will do a larger scale detail of that showing air flow and add some labeling.

New image added to photobucket.

[Hex]

Hi Randy
Thanks for the pic update. The new details make it easier to see the different paths for recirculation, heating and cooling.

It will be interesting to see how much of a bias you get towards heating or cooling depending on whether the flow goes through the upper tubes first or the lower ones.

[randy]

I am getting ready to contract a full semi-trailer of used 2'x4'x1.5" extruded polystyrene board for insulation. This will be doubled-up to 3" thickness and placed 3' below grade around the perimeter of the greenhouse as well as the interior of the head house and the headhouse foundation. The north side of the greenhouse will have a wall which extends 6' above grade, this too will be insulated.

[mrhobbithhnet]

First an apology for not being abreast of Randy's posts. phpbb is not behaving again... I should be getting a posting notice, but I'm not.

Hex, you were able to post pictures to a remote server, yet we could seen them in your post. How did that work? It's probably clear if ferret though some old posts, but maybe you could walk us through that.

In the meantime, I've got some server space kicking around, maybe I should make a folder available on line for registered users to upload to... assuming I can set it up that way.

I know I can do that with other online bb software, alas, it looks like not with this version of phpbb.

Randy's plan looks interesting.

I can see the basic layout, but I wonder if you could outline the air flow paths under your plan and the circumstances that prompt each flow pattern.
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[Hex]

Hi John
Posting images is very easy.
Upload a pic to the online photo album such as photobucket.
Below the pic you`ll find a box marked "IMG CODE".
With other album websites it may be have a different label..look for the line that begins with [IMG]
Copy and paste that line into your post.

[mrhobbithhnet]

Copy that, 10-4 Hex.
_________________
Just because it looks that way doesn't mean the Universe is about us, you or me. It's about Life.

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