----- Original Message -----
Sent: Saturday, February 24, 2007 3:15
AM
Subject: Re: [Livingontheland] growing
oranges in Nebraska: the PitGreenhouse link
Bobby,
I dont have any experience with underground structures,
but Im not sure that youll get enough sun-exposure if you
cover your greenhouse with an earth-roof. It may be OK to
dig the N, NNW, and NNE directions partly or completely
into the ground; however, anymore than that is likely to
result in one-sided growth.
Personally, I have been thinking about a passive-heated
greenhouse for a number of years, but so far havent had
the time to put it into practice.
My thinking goes in the direction of using the principle of the
trombe wall for building a greenhouse base of black stones
on a South-facing slope. Specifically, I would create a level
base on the slope by building a base of black stones that
would extend beneath the entire width of the greenhouse,
thereby warming the soil from below. A glass pane provided
at a distance in front of the South-facing base of black stones
would increase the amount of heat energy first stored by the
black stones during the day and then gradually released during
the night.
The only thing I havent figures out is if the black stones would
need to be in one piece across the width of the greenhouse,
or if the heat would be transmitted from one stone to another
if these touch each other or if they are bound by some sort of
medium, like sand for example. Any ideas?
Regards,
Dieter Brand, Portugal
PS: Geothermal heat pumps can be tricky. A neighbour who got
a very fancy geothermal system for heating the house installed
at great expense, finally got a wood stove after freezing for 3
winters.
On 2/23/2007 at 12:01 PM Bobby G
wrote:
>http://www.earthtoys.com/emagazine.php?issue_number=03.08.01&article=finch
>
>While
growing oranges in Nebraska is a bit more of a
>novelty than this list
is all about, it does show the
>value of this type of greenhouse
design.
>
>i am thinking that the earth-sheltered
greenhouse
>would be definitely among the first-year projects
our
>land co-op would undertake. not to grow oranges
in
>Wisconsin, but because of the huge advantage
in
>season-extending combined with the intensive
>mini-agriculture
approach.
>
>almost all the greenhouses in our area are
the
>above-ground structures that gobble energy like crazy.
>the
goal i have in mind would be a greenhouse that
>allows for (almost)
year-round growing PLUS only
>"sips" energy.
>
>what i'm
thinking is, it should be dug down into the
>earth quite a ways, with
only the SSE, S, and SSW
>sides exposed to the sun. the trench system
for
>geo-thermal heat-pumping is a great feature, but i
>fear it
would add enormously to the costs of such a
>greenhouse. the idea is to
start netting profit from
>use of a greenhouse almost right from the
beginning,
>not to invest huge amounts in sunk costs,
literally.
>
>if there is no hillside on the land we end
up
>acquiring, the second notion i've had is to use
the
>excavation dirt from a pond which is excavated, to
>create an
artificial "hill" to shelter the
>earth-sheltered
buildings.
>
>am i thinking in the right direction here?
i'll
>probably keep drifting in these directions unless
>y'all
knock me on the head by showing me where my
>thinking is
daft...
>
>bobby g
>
>
>
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