Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to systems for ~electively controling heat
losses photDperiods and te~peratures in a greenhouse.
Increased fuel cost and scarcity of so~e fuels have emphasi~ed the
need for energy cDnservatjon in greenhouses. Heat 1~55 is usually decreased
by eliminating unnecessary air leaks in the greenhouse roof and side walls,
covering the greenhouse with an inflated double layer of pDlyethylene~ or
installing opaque screens that are draw between the plants and the
translucent surface at night. However, it bec~nes evident that those
technigues give poor econo~ical performances when applied in cold-te~perate
area~. As a consequence, the agricultural approach of the ~orthern United
State and ~anada producers is tD operate si~ple greenhouses for only ~-7
~onths/years. For these areas, it has been estimated that during cold
months~ a total of about 4000 acres of greenhouse floors are left
uncultivated; because of the uncumpetitive heating cost that would be
involved.
The need for efficient m~bile thermal barriers in qreenhouses i5 ~ell
reflected by the density o~ the literature available on this subject. One
approach involve the use of flexible sheets o~ insulating material which are
deplDyed at night and stored during sunny days by a suitable ~echanical
çyste~. Different co~binations of such devices are described in Canadian
Patent Nos. 1,003,~41; 1,158,~S4; 1,14S,741 and in U.S. Patent no.
4~0~4,~48. The disadvantage of these systems is the co0plexity of their
~echanical par~s, which maka them susceptible tD fail on long term use~
especially during cold weathar.
~ any çystems have been proposed to cnntrol the temperature and the
photoperiod within greenhouses. The commDn practices to control these varia-
bles involve the use of an opaque cloth which is pulled over the cultivated
areas by a suitable mechanical syste~. In addition to heing expensive and
~o~plex, this method has been associated with heat build-up problen~ under
the cloth, during sunny days, Different ~,ystems for contrDlling the photope-
riod in greenhDuses are described in Canadian Patent Nos. 942 "426;
17,04~,070; as weel as in U.S. Patent Nns 3,2~4,150; 41062,146 and
4 " 108,373. In additon to their high CDst, these devices are relatively
fragile and not strong enough to support efficiently the hard wheater condi-
tions of ~inter.
It i5 known that for maxioum transmissiDn of radiant energy, thY ideal
architectural for0 for a greenhDuse is the hemispherical dome. The angles
in incidence of light and the orientations of the translucent surfaces are
optimum at all hours of the day and at all seasons of the year. E~i~tiny
henispherical greenhouse are intr3nsically li~ited in size because of the
strength limitations of their structural arches and Df their low diameter :
hei~ht ratio (2:1). Thus, although it i5 an ideal for0 in term~ of radi~nt
energy transmission, the hemispherical dome is unpractical for large-scale
greenhouse production.
Sum~ary of the inyent3on
The advantages of geodesic desing, that is predictability, precisiDn
and solidity have been applied in the conception of a greenhouse with a high
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~2~85
diameter:height ratio labout ~ hat can be operated economically 12
months/year. The main feature of this qreenhouse i5 that the translucent
surface area can be adjusted using an inner mobile ther~al barrier providing
a partial of a total insulation of the greenhouse atmosphere from outside
conditians.
The qreenhouse of the present invention includes:
~ main geodesic structure of a high diameter.height ratio, with a signifi-
cant portion covered with a suitable jnsulating material and oriented full
North.
~n inner geodesic structure slidin~ ~n a rail system around a central pole,
sized so that it can be juxtaposed exactly with remaining translucent por-
tion of the s3id main geodesic structure.
cable-pulley system which drive the said inner geodesic structure.
Dne or ~ore triangular panels setis) that can be temporarily (or perm3nen-
tly) fixed on the said mobile inner structure. During winter, panels com-
posed of an efficient thermal insulating material can be used. Duringsummer, panels composed of a suitable shading material can be installed to
redure light intensity or heat flux whenever desired.
The combination of this mobile inner structure ~used either as a thermal
barrier or as a shadinq system) with the solid ~ain structure, permits the
exploitation of large culture surface areas 12 months~year with relatively
low heating and maintenance demands.
Brief des_ipt1on of the dra~ings
Fig. I is an exploded view uf the major elements of a greenhouse embodying
the teaching of the present inventionu
Fig. 2 is a schematic showing some eiements and some of the various pos~ible
configurations of the Fig. 1 greenhouse.
Fig. 3 i5 a detail of the emoodiment of Fiq. l and Fig.2 showing a side
elevational view of the inner geodesic structure traction unit.
Fig. 4 i5 a detail of the 2mbodiment of Fig. I and Fig. 2 showing d
transverse cross section of the rail-cable-pulley system which drives the
inner geodesic structure.
Fig. S is a vie~ uf one isoca of the inner geudesic structure of the
embodiment of Fig. I and Fig. ~ showing the po~ition~ of the insulating ~or
shaùing) panels.
Z0 De_aile_ desc_~ption of _he ~nv_ntion
The geodesic structures involved in this inYention have been developed
from computer readout generated by programs written by JØ Clindon under a
N~SA-sponsored research grant: "~dvanced Structural Desing Concepts for
Future Space Missiuns"t Final Report, March 1~70l N~S~ contract NG~ 14-008-
002. The datas, principles and ~athematics involved in geodisic desing can
be found also in several popular publications on this subject.
In a prefered embodiment, the main structure is made fram five
identical four freguency isocas linked together to form a dome-like
~z~ s
structure with a high diameter:height ratio. The inner structure i5 ~ade
Df three fDur-frequency isDcas. It will be obviDus that different isDcas
frequencies can be applied in the ge~desic dQsing without departing fro~
the spirit Df the invention. ModificatiDns of some geodesic chord
factors should be perfor0ed to give a planar base to the 6tructure~.
Again~ the details of these modifications a5 well as of the different
geodesic structures building techniques can be found in several pDpular
publicatiDns.
It ~ill be obvious that different possible combinations in the
proporti~n; of the permanently and intermitently insulated parts of the
greenhou;e can be applied withDut departing fro~ the spirit Df the
inventi~n. The cDnditio~s described hereafter give good econD~ical
perfor~ances and are conse~uently cDmprise in ~ Frefered embodi~ent.
~ s seen in figure 1 and 2, the greenhDuse of this embDdi~ent cD~prises
a ~ain geodesic structure i supported on a circular foundation 11. T~o
isocas ~2/5 of the total surface area) of the ~ain geodesic structure 1 are
covered with ~n insulated surface 2 which i5 Driented full North. Three
isocas (3/5 of the total surface area) of the ~ain geodesic structure 1 are
covered with a translucent ~aterial to fDra the translucent surface 3. ~l5D
shown in figures 1 and 2, is the inner geodesic structure 5 which is ~ade of
three isDcas si2ed 5~ that it can be juxtaposed exactly with the translucent
surface 3 of the main structure 1. With such a co~bination~ the translucent
surface area ~f the greenhou~e roof c3n De adjusted fr~n 0 ta 2/5 ~f the
total roof surface are3.
As seen in figures 1, 3 and 4, the geodesic inner structure S i5
resting on a U-shaped circular support ~ on which wheels 8 are fixed at
point 7. This unit is gliding around an a~ial pole 4 ~n a circular rail 9
~hich is supp~rted by a serie of brakets 10 fixed on the foundations 11.
~ 5 best shown in figures 2, ~ and 4, the driving syste~ Df the inner
geodesic structure 5 comprises a traction unit 12 pulling a continuous cable
15 mDunted on a serie of pulleys 14 which are fixed on the brakets 10. The
continuous cable 15 is Lonnected tD the inner structure 5 by an articulated
braket 13 which should be nade of resistant materials. ~5 seen in fi~ure 3,
the traction unit 12 and the articulated braket 13 i5 done 50 that the inner
geodesic structure 5 have a maxi0um working path.
As it may be seen in figure 3 and 5, the insulating or shading panels
are fitted in the triangular frames fDr~ed by the studs lq compDsing the
inner geodesic structure 5 and are fixed in place with brakets 21.
Operation o~ th~ greenhouse i5 seen by referring to figure 2~
During cold sunny day~ the inner geDdesic ~tructure 5 equiped with thæ
insulatin3 panels set i5 moved in ~ront of the per~anently in~ulated
pDrtion 2 of the main structure 1, all~wing the s~lar radiant energy to
penetrate the qreenhDuse. ~s the sun passes over ~rDm East to ~2st
-Figures 2-~, 2~ and 2-C-, the said inner structure 5 is displaced 50
that the sDlar energy flux entering the greenhouse is maintained at a
maximum value at all hours of the day.
z~s
During the night -Figure 2-C-I the said inner stru~ture 5 i5 moved in
front of the translucent portion 3 of the main structure 1, which thermally
seals the greenhouse atmosphere and decreases drastically the heating
d ema n d .
During the su~mer, triangular shading panels are fixed on the inner
structure 5 53 that the temperature of the greenhouse environment can be
contrDlled ef~iciently with a relatively low ventilation demand.
It has been observed that in the worst condition, -i.e. in the ~iddle
of the summer at noon, when the altitude angle of the sun is 0axi~uo-
apprDxi~atively 1~4 of the floor surface of the of the greenhouse doe~ not
receive direct solar radiant energy. This shaded surface can be decreased
significantly by elevating the South face -that i5 the translucent pDrtion
3- of the main structure 1-. During winter, the altitude angle of the sun
is relatively low and consequently the shaded floor surface area is mini~um
and becomes negligible if the said greenhou~e elev3tion technique i 5
introdu~ed. This shaded area can be used as a working or stDrage space.
The shaded 5urface area in the greenhouse i~ reduced to an
insignificant proportion by the use of an inner structure articulated in tWD
~or threel separate panels which are moved and juxtaposed by 3 si~ple
~echanical apparatus. However, it should be noted that this approach
increase the ~aintenance demand and complicate the operation of the green
house~
B
~ prefered embodiment of the structural 3spects of this invention has
been set forth hereinabove. It will be obvious to one of ordinary skill in
the art that a number Df different changes and combination6, for e~ample, in
the type of insulating or shadin~ or translucent materials, the drive mean
of the inner structur2, the diameter-height ratio of the main geodesic
structure Dr the elevation angle of the greenhouse cDuld be made without
departing from the spirit o~ the invention. Consequently, it should be
understood that the pre~ent embodiment is purely illustrative and not
restrictive, and that the inventi~n is limited only by the following
claims;
A 9
