Solar Power Your Garden Dome
How to harness the power of the
sun - Use the suns radiant solar energy to heat your dome
As with all greenhouses, dome greenhouses make excellent
solar collectors. One reason why a dome can make more efficient use of solar
energy is due to the round shape; one or more dome triangles is always on
a nearly straight direct path to the sun overhead. There is a more consistent,
even warming effect through out the day. Inside the dome air circulates
more freely bottom to top for more ventilation and healthy plant life. For
best ventilation use a cupola top with windows and exhaust fans or one or
more fans attached to the dome frame. Use thermostat controlled fans, heaters
and cooling system. A computer with special software can regulate the temperature
and operate and monitor irrigation, humidity and other factors. Thermal actuators
such as the Uni-vent can automatically operate windows.
Passive Solar Collectors
I use 55 gallon drums filled with water for my solar collectors.
The are flat black plastic, previously used for detergent for car washes.
The flat black absorbs more of the suns light energy, don't use a shiny black
as it reflects the light. I have 9 of them in my 15 ft. Garden Dome 2 with
the Base Option, and more would do well in climates further north. The top
of the drum gets the hottest. When the temperature warms up I put plants and
shelves on the tops of the drums. Also the water can be easily poured or
siphoned out, and the drums taken out too. I live in north Texas so the freezes
aren't that regular, and I need only a small electric heater with thermostat
control to keep the dome temperature around 55-60 degrees F when it is around
32 outside. Any dark colored jugs filled with water will absorb heat during
sunny days and dissipate heat at night inside the dome.
Another solar collector is rock. I've noticed rocks inside
my dome get hot on sunny days. If they are dark colored they will get even
hotter. This method of passive solar collection is a valid option to water
containers. One way to do this is to make a cage of fence material to stack
your rocks in, located in a position to receive maximum sunlight. A fan on
the rocks will circulate the heat given off at night.
Rigid foam insulation inserted into the north triangular
faces of the dome will help retain heat during winter. The silver lined
type will reflect light back into the dome. Press to fit panels are easily
installed and removed. For cutting them out, try making a triangle template
with large cardbourd or plastic film, and marking the outline on the foam
board.
I have a ceiling fan to circulate air and blow warm air
down as the dome height is about 10 feet. The fan is attached on a pentagon
shaped piece of 1/2" plywood, that is screwed onto the five top struts of
the dome. For greatest floor area and least height, the Garden Dome 3 is best.
Winter observations from my own Garden Dome 2 that
I use as a workable demonstration dome.Inside the dome there's no wind,
circulation must be created when the windows are closed. I use the ceiling
fan and an excersize bike that has a fan incorporated. I have only ornamental
plants of many types, but the carbon dioxide I put out is important to them.
It can be very windy outside but calm inside the dome. There's no wind chill
factor. If it is 30 and windy outside and snow on the ground, it's 50 inside
the dome on a cloudy morning and that's without using the small electric heater.
I'm not using the foam insulation, only super poly and my dome is 98% sealed
from outside air flow. We had a "mild" winter.
Summer observations. The dome was getting too hot
inside (110+ degrees F) so we added some misters, window, shade cloth and
an extra fan. Some of the plants were baking while others (succulents) have
adapted quite well to the heat. I constructed a hinged triangle frame window/vent
and placed it on a top triangle. Then spray atomizer misters ( Misty Mate brand)
were attached to upper dome struts, and a Y connector for a water hose in
the dome (misters are plugged right into a garden hose). Next a square piece
of shade cloth was stapled inside the dome to reduce afternoon heat on the
herb growing area; an an extra fan to supplement the ceiling fan. We've had
a period of unusually record breaking hot days and little to no cloud cover
or rain for 3 weeks. June '98
Some pre-engineering of you dome foundation can bring more
passive solar heat by using the ground as the solar collector. Here are
some ideas of how to do this:
1. Where your dome floor will be dig down about 2 feet.
Here you will insulate from the ground up. Put in hard foam board insulation
right on the dirt.
2. Tubes below your dome floor will bring the heat collected
in the soil into the dome with a circulation fan. Array these tubes strategically
spaced on top of the foam insulation. Connected pvc tubes will work well
and support the weight of the dirt on them. A blower will circulate the warm
air from the conducting tubes into the dome. Your insulated dirt floor makes
an excellent solar collector. And you can still grow plants right in the soil
without interference. Plants will do well with a warmer ground temperature.
Your growing medium/soil can be replaced conveniently as necessary.
Below your dome frame base perimeter, a cinderblock retainer
wall can be placed in the ground when you are excavating for placement of
the foam insulation and tubes. This will also allow you to insulate the below
ground block wall with foam board insulation.
3. Fill the hole back up with the excavated soil. This
is your solar collector so you might plan on where no shadows are likely
to be.
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Some more ideas about using your Garden Dome
for growing
- Retain heat in winter with insulating techniques and solar collectors
- Ventilate in summer with windows and fans.
- Use thermometer to regulate temperatures Shade Thermometers,
place away from direct sunlight for most accurate readings
- Store water for heat collectors in black containers; flat black
paint may be used
- Clear jugs may be used; add black paint to the water to make
it opaque.
- Situate water heat collectors next to north side foam board
insulation panels to avoid blocking light on plants
- Use weather stripping at doors and windows and rubber sealant
to minimize air infiltration
- Grow plants/vegetables suitable for the season and temperature
- Wind, clouds, sun, growing zone and other factors determine
growing invironment-dome air and soil temperature
- In winter heat the water in the drums (or one that is centrally
located) with a submersable heater 800 - 1000 watt; or space heater near
the drums
- Use shade cloth during summer to reduce heat; it works best
installed on the outside
- Use windows with screens, for cross ventilation
- Use an exhaust fan
- Monitor temperatures more closely in Spring and Autumn when
temperature variations may be greater
- A thermal actuated automatic window opener works well
- Clean the covering once a year. Use biodegradable detergent
- Use double layers of film, and silver backed foam board for
insulation.
- Make removeable triangle panels that are covered with the horticultural
film such as our Super Poly. These can be installed in winter for heat retension
and removed in summer. Or attach shade cloth to reduce heat in summer. 1"
x 2" wood will make a good frame for the removeable triangles.
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Resources:
- Sunset- Garden and
Patio Building Book (by Sunset Books and Magazine Copyright
1969). Old but usefull, lots of good illustrations.
- Growing Solar Food In Greenhouses
(by Delores Wolfe, Copyright 1981, Doubleday & Company, Inc., ISBN 0-385-17603-1)
"A month-by-month guide to raising vegetables, fruits, and herbs under glass"
1st Edition, 192 pages.
- How to Build and Use Greenhouses
(by Ortho Books, Copyright 1978, ISBN 0-917102-74-6) Lots of nice color photos,
charts and drawings; 95 pages.
- The Complete Greenhouse Book (by
Peter Clegg & Derry Watkins, Copyright 1978, Garden Way Publishing,
ISBN0-88266-142-6) "Building and Using Greenhouses from Coldframes to Solar
Structures" More thorough and technical, 280 pages.
- The Big Book of Gardening Skills
(Copyright 1993, by the editors of Garden Way Publishing, Storey Communications
Inc. ISBN 0-8826-796-3) Good book about gardeing in general with one chapter
dedicated to greenhouses. 346 pages
- Add-On Greenhouses and Sunspaces
(by Andew M. Shapiro, Copyright 1985, Rodale Press, ISBN 0-87857-507-3) "Planning,
Design, Construction" Very thorough, 355 pages. Mostly pertains to adding
to an existing structure.
- Greenhouses, Cloches
and Frames (by Peter McHoy, Copyright
1984 Blandford Press UK, ISBN 0-7137-1244-9) All aspects of flower and vegetable
greenhouse gardening 128 pages w/ color photos
- Building a Solar Heated
Pit Greenhouse (by Greg Stone, Garden
Way Publishing Bulletin A-37, Copyright 1980) 28 page booklet with plans
to build a partially sunken greenhouse that uses the earth and sun for heating.
- Building and Using a Solar Heated Geodesic
Greenhouse (John Fontanella and Alvis Heller, Garden Way Publishing,
1979) Very informative but the dome building technique is difficult
and primitive.
On the World Wide Web:
Solar Power as Alternate
Energy
Greenhouse
Heating Checklist
Garden and Greenhouse
Home Page
Environmental Guidelines
for Greenhouse Growers
The Greenhouse -
Ohio State Univ.
Solar Links
from Sierra
American Solar Energy
Society
Florida Solar Energy
Center
Go Solar!
Research
in Environmental Architecture (good article on solar greenhouse by architect
Raold Gunderson)
Garden
Web - Greenhouses and Structures Forum
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