The
Crestone Eagle, February 2008:
A frost-free community solar greenhouse
by Paul Shippee
In these days of peak oil, resource depletion
and wars, and worries about the economy, a community needs
to learn how to grow its own food, especially in winter. The
San Luis Valley is an agricultural community that exports
and sells elsewhere most of the food grown here. Mosca and
Crestone and a few other areas have organic food growing operations,
and some families have successful food gardens in summertime.
We in the Crestone community are located at the end of a
long highway and may be vulnerable to interruptions in food
supplies, especially low-priced, good quality organic vegetables
in the winter season. For this reason I have taken an interest
in finding how we can grow our own fresh vegetables in the
winter. Naturally, I thought of a solar greenhouse to serve
this purpose. Therefore, in December and January I traveled
around the northern Valley visiting solar greenhouses that
might qualify as models for a good frost-free winter design.
I didn’t find much that was impressive or successful
in this regard.
Yes, the commercial greenhouses at the Sand Dunes swimming
pool in Hooper, the solar greenhouse dome at Joyful Journey
Hot Springs, and Erwin Young’s greenhouse building at
the Alligator Farm all sport exotic plants and flowers and
vegetables in winter. But these free-standing solar structures
are mainly heated by warm geothermal water flowing up from
deep in the ground and piped under the growing beds or into
the tilapia fish ponds. While the sun provides light for the
plants to grow, these designs are not adequate to provide
enough solar heat to support survival through the winter.
Observations I made at other free-standing solar greenhouses,
such as the various grow domes and Hanna’s greenhouse
in the Baca, Lillian’s Green Earth Farm solar greenhouse
in Saguache, and the Haidakhandi Ashram greenhouse, all are
vulnerable to below freezing temperatures in winter.
Although these types of free-standing solar greenhouses are
great for extending the growing season for all plants, they
are not adequate for growing a variety of vegetables through
the winter unless supplied with an auxiliary source of heat.
In other words, they are not designed properly for a frost-free
100% solar winter operation in our climate. In technical terms
these solar structures have too much heat loss (due to their
shape), do not have nearly enough thermal mass, and their
glass is not at the correct angle or high enough R-value.
Also in technical terms, in contrast to this, it definitely
is possible to make a 100% solar-heated greenhouse for winter
vegetables.
It is worth mentioning that the type of solar greenhouse
that is attached to the south side of a private home is quite
capable of producing winter vegetables when designed correctly.
This is mainly because the north side is coupled to the home
and loses no heat, but rather can gain heat from the house
when needed to keep temperatures above 40°F.
 However,
having exhausted the available resources for a free-standing
frost-free solar greenhouse winter design in our northern
valley I did not stop there. By some good fortune I remembered
hearing about a successful model of such a greenhouse built
in 1977 in Wyoming. When a solar friend in Alamosa mentioned
that the Cheyenne Community Solar Greenhouse was still thriving,
and was still operated under the original designer/director,
I called Shane Smith and arranged a tour in early January.
Arriving in Cheyenne on a sunny Monday morning I was at last
introduced to a frost-free, free-standing, 100% solar-heated
greenhouse that was blooming with orchids, bougainvilla flowers
and many green vegetables. The building, which also gets 50%
of its electricity from the sun, is now called the Cheyenne
Botanic Gardens (http://www.botanic.org ) and is run by the
city. There are six employees including a horticulturist,
a development officer, the managing director, Shane Smith,
and many volunteers composed of seniors, disabled folks, and
troubled youth who help care for, harvest and distribute the
yield.
I asked Shane Smith many questions about the design and performance
of this wonderful solar asset. Heated 100% by the sun in the
harsh Wyoming climate, the greenhouse never gets below 40°F
(except for a very occasional 38°F) in any windy winter
weather, cloudy or not. I had finally found what I was looking
for: a model winter solar greenhouse that really works! The
transparent south roof angle is 45° and Shane confirmed
that he has never found a reason to modify or change it. This
critical shape lets maximum full sun into the greenhouse in
winter, but not too much in summer, while providing enough
sunlight for year-round growing. The north roof is also 45°
and covers an interior north walkway, two stories of office
and library space, as well as access to a full basement under
the middle third of the building.
The key to the superior winter performance of this solar
gem is the very large amount of thermal mass arranged along
all of the north walls and also the lower portion of the south
glass wall. These are 55-gallon barrels full of water stacked
three-high and also many tall plastic columns of colored water
as well. In a quick eyeball observation I estimated the thermal
mass volume to be at least two cubic feet of water for every
square foot of south glass. The east and west walls are solid
with no windows. Two large fans high up on the north wall
are necessary to exhaust warm air in summer.
This free-standing solar model would certainly lend much
confidence to the design, financing and construction of a
frost-free 100% solar, winter food-producing greenhouse for
our Crestone community, as well as demonstrate the necessary
details required for surrounding San Luis Valley communities.
Toward this end I have been advocating such a project to potential
stakeholders such as Shumei International and other interested
parties who will join together and help make this vision a
reality.
| Looking for a solar CEO!
Qualified business-type persons interested in food
sustainability in Crestone and the surrounding San Luis
Valley are invited to submit inquiries to the author
via the website http://www.crestonesolarschool.com.
This position would require major business startup skills
and energetic initiative for tasks such as forming a
community corporation and board of directors, networking
with and coordinating stakeholders, land acquisition,
writing grants and other fundraising activities until
retail food sales become self-supporting. |
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