Redhouse – System Test 1

I may have built up my own excitement, but the redhouse (geo-thermal “smart” greenhouse) is really coming together.  In theory, I can put my overgrown bathtub tomato plants tomorrow.  This makes me extremely excited.  On to the test.

This test will see if the pump, the piping in the beds and the irrigation system all work.  These are the questions this test was hopefully going to answer:

  • Will the pump have enough pressure to water both beds?
  • Will the holes drilled in the irrigation PVC spray acceptable water?
  • Are there water leaks?
  • How much can I water with a 7 gallon reservoir?

Most of the answers can be found in this video:

The short version of the test is:

  • Enough pressure? Yes
  • Holes? Acceptable
  • Leaks?  Yes.  Around the valves and in the pump box
  • 7 gallon enough?  Maybe not.

The reservoir is the biggest disappointment.  I quickly ran out of water in the 7 gallon barrel during this test.  Further, it fills up slower from the rain water store than I can put into the soil beds.  This will likely limit my watering to only a couple minutes at a time.  I will also have to be careful not to run out of rainwater.  If I need 14 gallons per day of water, I’ll only have 7 days in the store (two 55 gallon tanks).  It is possible to use my brothers two barrels.  That will give me a couple weeks and worse case I can fill up the tanks with house water.

Next test should be hooking up the controller.  We should be able to start getting some measurements to see the benefits of the geothermal system.

Redhouse (previously “geohouse”) – Construction

Over the past few weeks a lot of progress has been made on the redhouse.  First, the name of the project changed.  As we got the frame built, my son who is 8 started calling it the “redhouse” instead of greenhouse because of the red burgundy paint we used.  I liked the name.

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After painting we built the arches that will act as the equivalent to a Mittleider t-frame.  The reason there is no “t” in the frame is because we are maximizing wood usage.  The outer bed will also act as the support wall for the greenhouse film.  The benefit is, I can fit two beds in the redhouse.  The drawback is, the plants will be very close to the wall.  After building each arch, we put the arches in the ground from 12-15″.  The ground we are working with has a slope.  To make the arch level, one side is more shallow in the ground than the other.

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Oregon is rainy, so instead of using dirt or worse: cement to secure the posts, we used 1/4″ and 3/4″ crushed rock to allow for more drainage.

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Once both arches were up, we painted and laid the 2×10 boards that will become the garden bed.

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We also painted and installed some 2×4″ boards at the top to support the pvc hoops.

Once that was done, I created a base for the inner-bed tubing.  I used a 36″ x 2.5″ 12 guage aluminum sheet as the base and used zip ties to secure the tubing to the base.  Over the tubes in strategic location I put thin sheets of aluminum that are typically used with pex for radiant heating applications.

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Under the aluminum and tubes I put a sheet of reflective insulation.  I probably could have gone thicker, but this is okay for now.

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I put two holes in the board and attached braided tube for the inlet and outlet.  PEX tubing is not UV protected.  So I don’t want it exposed to the sun.  It’s also not very flexible.  So the braided tubing is great for in between the pex, the pump and the earth.

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Now that the inner tubes are installed and in place, time for the soil.  Following the Mittleider pattern, I’m using bark dust.  Normally the Mittleider system calls for traditional sawdust.  This fine dark hemlock dust, however, looks great and looks could help with heat absorption because of the dark color.  I mixed with about 30% sand and dumped it in the bed.

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For this 12 ft x 18″ bed, I used 400lbs of dust and close to half a cubic yard of hemlock dust.

Irrigation plumbing time.  Nearly following the Mittleider system by the book, I got thin wall 3/4″ pvc and drilled tiny boles in it for water to come out.  I also installed some ball valves so I can adjust the pressure and also close off the second bed if needed.  A bit about the second bed.  I’m assuming for the moment that I will not be able to heat/cool the second bed.  I’m being conservative.  If the first bed’s temperature is easy to maintain, I will add the second bed to the system next season.

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The redhouse.is coming together nicely.  Once I test the irrigation system and install the controller, I’ll transplant some bathroom tomatoes that are getting too big for the bathtub.  The only thing left after that is to attach the greenhouse film.

 

 

 

Geohouse – Heat pump and irrigation system explained

Here’s an explanation on how the pumping system will handle both the irrigation and the heat exchanging through the geo exchange.  It involves two relay-controlled valves: one normally open for the geo exchanger and one normally closed.  They will be hooked up to the same relay so that when the open one is closed, the closed valve will open and water will immediately be pumped into the irrigation pipes to water the plants.

This allows me to use the same water, water which is being temperature regulated, and the same pump for both irrigation and regulating the soil and air temperature.

 

 

Using yocto combo layers and adding a new layer

It’s easy to add your own layer using the combo layer system.

  1. Edit conf/combo-layers.conf and add a section for your layer.
  2. cp conf/combo-layers-local-sample.conf to conf/combo-layers-local.conf and add a section for your new layer
  3. run scripts/combo-layer init
  4. after you have a build directory (by sourcing oe-init-build-env) edit build/conf/bblayers.conf and add your layer
  5. bitbake as per normal

 

Geohouse – Risks

I feel like the geohouse project is something unique that carries lots of risks.  What I’m doing has been done, but not quite the way I’m doing it.  What if my assumptions are wrong?  What are the costs?  This post hopes to answer those questions.  First, what components will this geohouse have?

  • Solar Power System – $2,000 (5 panels, 4 batteries, charger)
  • Pump and tubing system – $140
  • Greenhouse plastic – $170
  • Wood – $250
  • PVC pipes – $120
  • LED grow lighting – $120

The worst case scenario is that I cannot keep plants alive during the coldest months (Nov – Feb).  This system gives me at least 3 months extra growing and production in the absolute worst case.  Best case is that I get 12 months of production.  Here’s a short list of other things that can go wrong:

  • Not enough sun to power solar array (North West sun hides for substantial parts of the year)
  • Too much heat loss
  • Not enough sun to add energy to system
  • Not enough heat storage (geo-battieries)
  • Components break (power supplies, pump, etc).

Geohouse – The geo-exchange heated smart green house

Once my first raised bed garden is happy producing food I started planning the next raised bed.  It was to be an 18 inch wide and up to 16 feet long bed in the Mittleider tradition.  However, while watching youtube videos about people using the Mittleider method, I became inspired to try and extend my growing season -perhaps even year round by using the earth as an energy storage system (aka, a battery).

Each gram of wet soil can hold 0.35 calories of heat energy.  At depths from 4ft to 6ft, the soil is far enough down to be insulated from the air above and maintains a year-round temperature from 55 to 60 degrees F.  Many residential and commercial buildings utilize this almost free energy and feed it into heating and cooling systems that would normally be pulling from less optimal sources such as trying to cool air from outside during the summer time or trying to heat cold air during the winter.

I started researching methods of accessing this geo energy.  After digging around on youtube some more, I found several systems that blow air through the ground via tubes and back into the greenhouse.  The air would be heated by the sun and then some of that energy would be transferred into the ground where it can be used during the night.  Air, however, is a poor conductor of energy at about 1/4th the specific energy as water and less than the soil itself.  So I wondered if there was a better way.

Water has one of the highest specific heat properties of any medium.  At first I thought about pumping water through a radiator and warming or cooling air via that method.  However, it occured to me that the system could be much simpler.  During warm days, a common method of cooling the plants is to water them.  The plants, via the roots then become cool.  The same principle should be possible with heat as well.  If the soil temperature is maintained, we may be able to keep the plants happy.  Can water be used to heat/cool the soil directly?  Yes!

An efficient way of heating businesses and homes has been in-floor radiant heating.  The method pumps hot or cold water through PEX tubing in the flooring system.  The warm/cool floor then heats or cools the ambient air in the room.

To make a long discovery process short, I decided to combine these methods.  I will pump water into the earth and cool a 12 ft by 18 inch bed directly at the root level.  To insulate the bed, I’ll put a double layer 6mm green house film around it.  The hope is that I can keep the temperature around 50-60 degrees all year (+20 degrees in the winter).  Can it be done?  Let’s find out.

Auto-irrigation Raised Garden – Part III: Rainwater

Another important part of this automatic irrigated raised garden project is rainwater gathering.  Instead of using expensive house-water, we can gather and use “free” rainwater from the sky.  Untreated rainwater is more health for the plants.

I’m using two 55 gallon drums that I was able to find on craigslist for about $20 a drum.  I got an extra two drums for my brother.

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All four drums fit snugly in my minivan for transport back home.

After getting them home, I need a support structure to put them on.  A friend of mine offered me a pre-built structure that his mother was using.  I accepted and with a few modifications, this is the result:

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This is situated right around the corner from the first raised garden.  It will not take much tubing to get the water there.  Also, the top of the drums is 7 feet.  This will give me about 3 PSI of pressure (assuming 2.3 ft/PSI).  That should be enough pressure.

Update: this post has been over a month in the making.  During that time I’ve had no rain to fill the drums.  I have water now and it works!  Part IV we will look into hooking up the Edison and making a schedule.

Auto-irrigation for raised garden – Part II: The raised garden

Quick update on the raised garden project.  The first garden bed is built!  This is a 6 x 3 ft bed with 5 x 3 ft of growing space.  I used cedar outdoor wood and I think it looks pretty nice.

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Shortly after building, I did a bit of research on the Mitleider gardening method.  In order to do vertical gardening, I need taller posts which I initially thought I would just use for grapes or other vine plants.  I may end up redoing the post system or at least modifying it so I can vertically grow my tomatoes and melons in order to maximize space.

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This bed is also equipped with an equipment box.  This is where most of the auto-irrigation system will go (valves, Edison module, panel charger, energy storage, etc).

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Finally I’ve mounted my 10 watt solar panel.  After observing, I don’t like this position.  It should go on the back pillar to avoid casting shadow on my other solar panels: the plants below.

Next Part: Rainwater gathering