Regularly redisplay this web page to keep up on the progress of the YMCA Solar Greenhouse.
Official ground breaking for the YMCA Solar Greenhouse
Slide Show about the YMCA Solar Greenhouse
Roanoke Times article about the YMCA Solar Greenhouse
Roanoke Times blog about the YMCA Solar Greenhouse
Many people think that any greenhouse is a solar greenhouse. That is not correct. A solar greenhouse has the ability to store much more energy from the Sun than does an ordinary greenhouse. The energy is usually stored in water or rocks inside the greenhouse, taking up floor space. See Solar Greenhouses for more information.
A solar greenhouse (SGH) differs from a standard greenhouse in that energy is collected from the Sun and stored for use when the Sun is not shining. Greenhouses tend to get too hot when the Sun is shining and too cold during winter nights. A SGH stores energy in some medium other than the air and the soil during sunny weather. The best SGH cools the air as needed when the Sun is shining as well as heats the air when needed. This process of cooling and heating needs to be done with a minimum of energy input from external sources other than the Sun.
The YMCA Solar Greenhouse uses a new way to store energy collected from the Sun, in a subterranean heat sink of soil/rocks/water under the planting beds. This system is called the Subterranean Heating and Cooling System (SHCS).
Global Warming and Peak Oil require that humans acquire their food from local farmers or grow it themselves. In climates with cold winters, such as at Blacksburg, Virginia where Virginia Tech is located, acquiring local food in the winter time requires the existence of solar greenhouses. Of course, one could preserve summer crops by canning and drying, but fresh vegetables in winter months would make a healthy diet more likely.
The YMCA at Virginia Tech has managed a community-gardens area on property of the Town of Blacksburg for several years. A new 8-acres area at the end of Maywood Street (215 Maywood Street) off of North Main Street in Blacksburg is being developed into a larger YMCA-at-Virginia-Tech Community Gardens. It will be called the Hale-YMCA Community Gardens.
An 18'x32' SGH utilizing the Subterranean Heating and Cooling System (SHCS) is being built as part of the Hale-YMCA Community Gardens. As far as is known, this will be the first SGH using the SHCS in the United States east of the Mississippi. Plans are to have the SGH built in time that planting can be done for the winter of 2008-9. It is called the YMCA Solar Greenhouse (YMCA SGH or YSGH).
A model of the YMCA SGH, made by Dave Nickerson, is in a display case inside the front door of the YMCA Center at 1000 North Main Street in Blacksburg VA.
YMCA SGH Steering Committee consists of Pat Bixler (chair), Tim Colley (architect), Gail Billingsley (YMCA of VT), Arlean Lambert (land owner), Justin Boyle & Jason Boyle (Green Valley Builders, Inc.) & Dave Roper.
The site plan was made by Anderson & Associates. The original rough sketch of the YSGH was made by L. David Roper. The architectural drawings were made by Tim Colley and Travis Rookstool . Engineering calculations were done by Truesdell Engineering. The construction is being managed by Justin Boyle of Green Valley Builders, Inc.
Several businesses have donated time and materials to build the YMCA solar greenhouse.
The best orientation is with the glazing toward geographical south. In Blacksburg VA magnetic north is about 6.5 degrees west of geographic north, so magnetic south is about 6.5 degrees east of geographic south.
 Not shown is a 2'x2' vent Marvin awning window high on the east end. Initially the window will only open by a hand crank (with a built-in ladder to reach it). Later it may have an electric opener actuated by a thermostat |
 Not shown is a 2'x2' vent Marvin awning window high on the west end. Initially the window will only open by a hand crank (with a built-in ladder to reach it). Later it may have an electric opener actuated by a thermostat. Later it may have a fan to pull air inside. |
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 The rows should be planted north-south instead of east-west as shown here, in order to get more equal sunlight on the plants. |
The computer model was made by Tim Colley and Travis Rookstool of Colley Architects PC. Anyone wishing to obtain detailed plans for this SGH or a revision for a different size of SGH should contact Colley Architects.
Dave Nickerson made a physical model, which is on display in the YMCA Center at 1000 North Main Street in Blacksburg VA.
The below-ground walls are made from ICF (insulate concrete forms) filled with concrete. The R value is 32 (ft²·°F·hour/Btu). The above ground walls are 2"x6" wood studs on 2' centers filled with foam insulation. The inside and outside finish is a fiber-cement panel (HardiePanel).
The north roof is 2"x10" wood rafters on 2' centers filled with foam insulation; its inside finish is a fiber-cement panel (HardiePanel) and the outside finish is architectural shingles. The south roof is 10-mm x 4' double-walled polycarbonate on 4"x10" rafters on 4'3/4"-4'1" centers. The polycarbonate sheets are attached to the rafters using the Base and Cap system.
The rafters connect at the top to a 34' long 4"x14" beam.
Polycarbonate panels:
Polycarbonate crate: |
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All ground water must be excluded from entering the heat sink. This is done by the following systems:
Two 36" Action-Aire ceiling fans, actuated by a switch and a Ranco adjustable digital thermostat will be hung from the SGH peak centered between the center post and the two walls. Their purpose is to keep hot air from accumulating at the peak.
The thermostat sensor will be placed near the peak, shielded from sunlight. It will be set to turn on at 90° F and off at 70° F. The thermostat could be in the same box as the thermostats for the heat-sink fan, with a long lead to the sensor near the top. The switch for the ceiling fans could be in the same box as the thermostats, out of range of prying eyes.
Here are some considerations for the electrical wiring of the YSGH:
Here are results of the soil tests for the SGH site:
Analysis: |
P (lb/A) |
K (lb/A) |
Ca (lb/A) |
Mg (lb/A) |
Zn (ppm) |
Mn (ppm) |
Cu (ppm) |
Fe (ppm) |
B (ppm) |
Soluble |
Result: |
7 |
46 |
1150 |
149 |
0.7 |
4.3 |
0.4 |
5.2 |
0.3 |
1 |
Rating |
L |
L |
M |
H- |
Suff |
Suff |
Suff |
Suff |
Suff |
L |
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|
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|
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|
|
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Analysis: |
Soil pH |
Buffer Index |
Est.-CEC (meq/100g) |
Acidity (%) |
Base Sat. (%) |
Ca Sat. (%) |
Mg Sat. (%) |
K Sat. (%) |
Organic Matter (%) |
|
Result: |
6.2 |
6.34 |
3.9 |
9.2 |
90.9 |
73.6 |
15.7 |
1.5 |
2.8 |
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lb/A = lbs per acre; Sat. = saturation; Est-CEC = estimated cation exchange capacity; g = gram, Suff = sufficient; ppm = parts per million; L = low; M = medium, H = high, meq = millequivalent |
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Fertilizer recommendations: Apply 4 lbs of 5-10-10 per 100 sq ft. |
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Soluble salts are not high enough to cause salt injury. |
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The National Sustainable Agriculture Information Service may be of help in preparing the SGH soil for planting:
Hydrologic Soil Group Descriptions:
A planters' committee (Abigail Convery, John Ogburn, Deborah Wiley and Holly Scoggins) are studying what to use for topsoil; e.g., whether it will involve the original topsoil or not. One option is growing mixes by SunGro.
Sun Gro donated 75 bales of Organic #1 Mix in 3.8 ft3 bales (which expands to 7 ft3 for a total of 525 ft3). This will be mixed with sand and worm castings to make the approximately 750 ft3 needed for the planting beds.
Under the 3'-wide walkway and the 5'x5' turn-around at the west end will be #57 stone (~8.5 tons) from the tarpaulin at the top of the heat sink up to about two inches below the top of the planting bed. It will be installed at the same time as the planting soil is added to the two planting beds on each side of the walkway. On top of the rocks will be a walkway made of 5/4"x6" Trex "boards" with Trex ribs under them to hold them together. (Eight 16' Trex boards.)
Two 1050-gallon Infiltrator Systems cisterns with their tops 2' below ground on the south side of the southeast corner of the SGH will store rain water that falls on the roof to be used for watering the plants. There will be filters to keep debris from entering the cistern. At the beginning town water will be hauled in to mostly fill the cisterns.
The water will be pumped out of the cisterns by an F&W EK05S 1/2-hp (373 watts) shallow well jet pump into a pressure tank behind the center post of the SGH. There will be two water faucets for each bed, one at each end of the walkway.
The problem is that some water and heat needs to be stored in the heat sink below the planting bed before vegetable greens are planted in the SGH. In normal operation that water and heat comes from the 90% transpiration of water from plant leaves that comes from watering the plants in the soil. So, it is a “chicken and egg” quandary.
Here is a possible procedure to solve the quandary: After water is hauled in to mostly fill the cistern at the start, some of that water is sprayed into the SGH air and placed in pans on several consecutive sunny days, so that the SHCS can start to work by pulling humid air into the heat sink. Then watch the temperature and humidity for some cold days to see if the heat sink is working. Some lettuce starts will be quickly planted.
Also, the heat-sink fan's rheostat needs to be adjusted for the correct air flow in the heat-sink pipes. The HOBO U10-003 temperature and humidity data sensors/loggers at the heat-sink inlet and outlet pipes will be used to determine the correct air flow to yield the biggest difference in temperature and humidity at those two locations on sunny days.
After a week or two of testing, hopefully confidence will be built so that plants can be planted. Soil-heating cables may be used to help plants get started growing.
Soil heating cables may be used to get plants started.
YMCA SGH Steering Committee consists of Tim Colley (architect), Pat Bixler (chair), Jason Boyle (Green Valley Builders, Inc.), Arlean Lambert (land owner), Dave Roper, Gail Billingsley (YMCA of VT), ), Justin Boyle (Green Valley Builders, Inc.), in the order left to right in the picture below.
For the remainder of the winter of 2008 the YSGH will be divided into two parts, separated by a north-south line through the center post. The east half will be planted and cared for by students of Blacksburg New School and the east half will be planted by a group of gardeners organized by John Ogburn and Deborah Wylie.
L. David Roper, http://arts.bev.net/RoperLDavid/; roperld@vt.edu
06-Jan-2009
