Solar Heating of the soil in High Tunnels

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Solar Heating of the soil in High Tunnels

• Dallas Flynn
• Terrance Nennich
• Thaddeus McCamant

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Project Sponsors

• Minnesota Department of Agriculture Sustainable
  Agriculture Grant
• University of Minnesota Extension
• Nothland College Specialty Crop Program

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Project Purpose

• To heat the soil in high tunnels using
• passive solar heat for year around
• production with minimal fossil fuels

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Project Progression

• The size of the tunnel was a 30 X48 X 12
• FarmTek
• Double plastic was used
• Extra purlins were added for strength

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Step one

• The Soil was dug out to a depth of four feet

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Step one

• The soil was dug out to a depth of four feet

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Step Two

• Erect four foot wall and insulate
• Bottom two feet of the wall has two inch
  styrofoam insulation
• Top two feet of the wall has four inch styrofoam
  insulation

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Step three

• Two inch styrofoam insulation on the bottom

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Step Four

• Twelve inches of sand was placed on the two inch
  floor styrofoam
• Four inch non-perferated drain tile was placed on
  the sand with a spacing of 16 inches between the
  tile
• The bottom is referred to as zone one

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Step five

• 12 inches of sand was used to cover the tile of
  zone 1

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Step Seven

• Zone two tile was layed at a 90 degree angle to
  the tile of zone one

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Step Eight

• 6 inches of sand was brought in to cover zone 2
  tile and the tile was put through the outside wall

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Step Nine

• 18 inches of top soil was brought in for the
  growing medium

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Step ten

• The high tunnel was erected at this time

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Step Eleven

• Installation of duct work and solar panels
• Two 4 X10 foot solar panels and one 4X8 solar
  panel were used

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• 2X12 White Oak was used for the perimeter of the
  high tunnel and the two outside raised beds

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• Air leaves the solar panels at about 125-175
  degrees depending on the amount of sun
• Air leaves the soil at 50 75 degrees to be
  recirculated through the solar panels (this is a
  closed system )

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Results to Date

• Soil temperatures have been kept at minimum of 52
  degrees even though outside temperature have been
  well below 10 degrees.
• At this temperature cool season crops are doing
  very well

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Soil Temperature
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Air temperature
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Data we will be collecting

• Winter time soil temperatures
• Best crops for winter production
• Early spring growth of warm season crops
• How late in the year can warm season
• crops be produced.

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