Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
The present invention relates to a method of operating
a ho-thouse and a hothouse adapted to carry the method into
practice.
Elothouses are known to consume large amounts of
energy. Numerous suggestions have already been made in an
attempt to reduce the energy requirement of ho-thouses and/or to
obtain the energy required in part or entirely from natural
sources of energy such as solar energy or groundwater. In
certain cases it is necessary to operate hothouses during
certain seasons only, particularly where special crops are
involved. At any rate, lt cannot be avoided that a fraction
only of the energy to be expended can be used efficiently for
the crops and their growth. By large the major part of the
energy to be provided is lost without serving a useful purpose,
ei-ther through the soil in the hothouse or through the walls and
roofs of the hothouse.
It is known that it is possible to accelerate the
growth of plants in a hothouse while simultaneously saving
energy by adjusting carbon dioxide content of the hothouse
atmosphere in a predetermined manner. Fertilization by carbon
dioxide (CO2) produces particularly favorable effects in
2~7
zones or during seasons in which only small amounts of light
are available to the crops.
Several proposals have already been made to enable such a
control of the carbon dioxide content of hothouse atmospheres
to be effected by introducing thereinto waste gases produced
by heating processes, particularly through the combustion of
gases.
However, both the construction and the operation of means
permitting this method to be adopted are so expensive that
their use can only be contemplated where installations of
very large size are involved. Another factor to be taken
into consid~ration is that the time patterns of heat and
carbon dioxi~e requirements are not congruent. Moreover~ it
is difficult to select the correct concentration of C02 because
an excessively high C02 may be detrimental to both crops and
humans. More in particular, it is extremely difficult as
well as expensive to introduce C02 and to control the distri-
bution of the gas in a hothouse because the major part of thegas introduced cannot be utilized by the cropsr
Still another problem is posed by the necessity of controlling
animal and vegetable tfungus) pests and diseases, the develop-
mellt of which is particularly encourased by the atmosphereexisting in a hothouse. Large amounts of work must be ex
pended in order to sort out diseased plants and to check
propagation of diseases by the application of chemical means.
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~L5;~
The present invention provides a method and a hothouse
of the aforeindicated kind which are adaptecl to avoid the
problems described earlier. The present invention also enables
the operation of a hothouse to be optimally matched with various
types of crops and their different requirements. The present
invention further enables old and uneconomical hothouses to be
operated more efficiently and economically and to increase the
yield also in newly constructed hothouses. Finally, the pre-
sent invention reduces or even entirely avoids the necessity of
employing insecticides and herbicides.
According to the present invention therefore there isprovided in a method of using a greenhouse, wherein individual
cultivating areas within the greenhouse are spacially and ther-
mally insulated relative to the ground and the inside of the
greenhouse, and heat and moisture is supplied in a controlled
manner to the insulated areas alone, the improvement in which
the individual cultivating areas are insulated against an ex-
change of gas with the surrounding atmosphere of the green-
house, and pure carbon dioxide gas is supplied intermittently to
~ an insulated cultivating area for a limited period of time in
each case in a quantity which is sufficient to destroy oxygen-
consuming pests, and furthermore pure carbon dioxide is supplied
in quantities such that a C02-concentration is maintained in the
atmopshere of the insulated cultivating area which is sufficient
for fertilising the plants and which is higher than the normal
concentration in the air.
According to the invention spatial and thermal
insulation are provided between individual crop areas within a
hothouse towards the subsoil and towards the interior of the
hothouse and the insulated areas are supplied only in a pre-
determined manner with th~e required amounts of heat, humidity
and carbon dioxide.
C - 3 -
~L~152 ~,t;~
Wi-thirl the hothouse the individual planting zones are
insulated from one another. This implies both separation in
space and insulation as regards the supply vf heat, humidity
and carbon dioxide gas requirements. Each insulated cultiva-
tion area is independent of all other cultivation areas within
the same hothouse. Thus, it is possible to select optimum
conditions in each insulating cultivation area for the crops
being cultivated therein. This is applicable -to heat, humidity,
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52~
fertilizer and carbon dioxide requirements.
The sèparation of individual cultivating areas within a
hothouse from the remainder of the interior of the hothouse
makes is possible to reduce not only the amount of heat re-
quired but also the amount of carbon dioxide necessary to a
large extent because the individual volumes to be heated and/
or supplied with carbon dioxide are extremely small as com-
pared to the total interior volume of the hothouse and are
separated therefrom.
Thus, according to this invention, it is possible for the
first tirne to nip in the bud the occurrence of animal and
vegetable (fungus) pests and diseases in a simple and
ecologically completely harmless manner without creating any
health hazard. For this purpose, the insulated cultivating
areas are supplied~ during limited periods, with carbon
dioxide in a concentration which exceeds a multiple of the
rnaximum concentration employed where the crops are fertilized
by means of carbon dioxideA For example, where the maximum
carbon dioxide content employed for fertilization amounts to
approximately 0.15 per cent by volume, it is possible, for
a short time, to supply the crops with carbon dioxide gas in
such a quantity that the concentration within these limited
areas will reach between 10 and 100 times the said amount.
Experience has shown that, as a rùle, such concentrations
will not be a hazard to the crops. On the other handt however,
pests reqùiring oxygen and, with humidlty being suitybly ad-
~usted, also fungi will be destroyed by such a carbon dioxide
shock. The ernployment of conventional chemical pesticides
can be dispensed with~ The employment of carbon dioxide is
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~..,'~3 5Z~'~
ecologically harmless, simple and reliable.
In order to introduce yaseous C02 into the insulated culti-
vating area it is advisable that a gas containing carbon
dioxide be transported by means of a carrier fluid into the
immediate vicinity of the surface of the soil in the hothouse
where the gas is set free in such a way as to form a stable
gas layer in the vicinity of the soil surface. In doing this~
it is possible to employ as a carrier fluid a tempered ~ater-
ing liquid, particularly water prepared in a predetermined
manner .
Thus, with the aid of the method of the invention, it ispossible for the dioxide gas, particularly that employed as
a fertilizer, not to be employed in its gaseous form, for
of
example in the form/combustion waste gases or the li~e which
are transported by means of blowers or the like, but physical-
ly combined with water and partly in chemical combination,
so that the gas can be distributed in the cultivated areas
in a predetermined manner and within the desired areas so
that the gas is released in the immediate vicinity of the
soil surface. Thus, the major proportion of the gas is only
set free immediately above the soil surface by the carrier
fluid. Accordingly, also due to the insulation of tile
individual cultivating areas, large amounts of fertili~ing
gas will be savedO
At the same time, the carbon dioxide layer remainlng near the
s~il surface affords strong protection against the dcvelop-
rnent of yeast or mildew with the result that the necessity
~z~5Z27
of employing special chemical pesticicles is reduced to a
minimum .
The method of the invention malces it possible, insteadof employing larye quantities of peat, to obtain the necessary
acidification of the soil in a simple and inexpensive manner
because part of the carbon dioxide gas chemically combines with
the wa-ter, such gas being introduced into the soil together with
-the water so as to influence the pH value accordingly.
This method of introducing the gas makes it possible
lG to reduce expenses to a considerable extent by employing CO2
supplied in high-pressure cylinders or tanks without the neces-
sity of providing expensive apparatus. It is also possible in
most cases to make use of existing overhead irrigation equip-
ment. It is further possible to utilize other gas sources
containing C02, for example, waste gases produced by gas-fired
heat pumps, by collecting such gases in a pressure vessel where
such gases are placed under the impregnating pressure by apply-
ing thereto the pressure prevailing in a cylinder containing
pressurized C02.
The present invention also provides a greenhouse for
carrying out the method of the present invention having a
plurality of individual cultivating areas arranged within the
greenhouse, which are each spacially and thermally insulated
relative to the ground and the inside of the greenhouse, each
cultivating area comprising a trough-shaped insulation for
receiving the cultivating soil and a hood-like cover made of
light-permeable, heat-insulating material, and being connec-
table to a supply arrangement for supplying heat and water via
ducts, the improvement in which the hood-like cover of each
insulating cultivating area is formed by a double layer hood,
which overlaps the edge ~of the soil trough and engages in a
gastight manner with its lower edge in a channel which is
C
~ Lz~s2~t~
associated with the soil trough and which is filled with fluid,
and each insulated cultivating area can be connected to supply
arrangement for supplying pure C02 gas and for water impregnated
with pure C02.
Thus for the purpose of carrying the above-described
method into practice, this invention provides a hothouse
~greenhouse) which is closed towards its exterior and is pro-
vided with heat insulating means disposed between the sub-soil
and -the cultivated soil layer, the individual cultivating areas
within the hothouse being insulated toward the interior of the
structure by means of structures which, in turn, resemble hot-
houses, said
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insulated cultivating areas being connected by distributing
means to devices adapted to supply heat, ~Jater and carbon
dioxide Conveniently, each insulated cultivating area within
the hothouse has associated therewith an individual tub-shaped
bottom insulating arrangement the periphery of which extends
above the surface of the cultiv~ting soil within the hot-
house In connection with this, it is convenient for each
tub-shaped bottom insulatin~ means within the hothouse to
have associated therewith an individual hothouse-like arrange-
ment extending over the periphery of the insulating means.
In cases in which the teaching of the present invention isemployed, it will, as a rule, be possible to avoid the neces-
sity of providing means for heating the hothouse in its
entirety Because the heat losses of the hothouse are re-
duced to a large extent, it may be necessary, sometimes only
temporarily, to heat the hothouse in order to maintain a
relatively small increase in temperature.
For the purpose of providing insulation towards theinterior
of the hothouse, individual cultivating areas or all areas
are insulated by means of double-skin transparent hoods,
enclosures and/or covers.
Said hood-shaped covers are conveniently provided with sus-
pension cords so as to be capable of being raised and lowered
as desired so as to facilitate ad~ustment of the air volume
within the insulated cultivating areas to the vertical ~rowth
of the crops and thus to maintain this volume always as small
as possible. This arrangement affords optimum utiliæation
3 ~5~
of heat energy and C02 and the possibility of accurately
controlling all parameters influencing the atmosphere wlthin
the insulated area~
The said insulation of individual culti.vating areas in re-
lation to the interior of the hotnouse affords the additional
advantage that it is possible in conditioning the air in the
hothouse also to adjust the humidity in the individual culti-
vating areas to the desired values~ it being important in
this connection to counteract the formation of condensate
on the separating surfaces constituting the insulating means.
Such condensation of water might occur during overhead irri-
gation, surface irrigation or sprinkling while there is a
corresponding difference in temperature between internal and
external air.
Since the cover structure is of twin-wall construction, the
influence of a large difference in temperature at the inner
surface of the inner wal.l is reduced so that there is also
less danger of condensate formation. However, complete re-
moval of surplus humidity by condensation may be obtained by
means of an air recirculating system which is associated
either with a set of insulated cultivating areas or with
individual such areas, such a system comprising~ in addition
to air circulating means, one or a plurality o~ sulated
cultivating areas, a cooling heat exchanger serving to remove
humidit~ by condensation and at least another heat exchanger
serving to heat the dried air, the said units being arrang~d
in series. With the hothouse having a cooling room connected
there~ith, it is possible in a simple manner to employ such
3L2~5Z~7
a room for removing by condensation the humidity entrained
by the circulating airflow, such condensate being then em-
ployed fcr watering the cultivating areas~ For this purpose
it is possible, for example, to employ the primary side of
a heat pump. However, it is also possible to employ the
cold of external air. It is advisable, prior to reintro-
ducing air cooled in this manner into the insulated culti-
vation areas in order to aid in drying the walls, ayain
slightly to reheat this air by means of a heat exchanger to
the temperature prevailing in the insulated cultivating area.
For this purpose, it is also possible to flow the recirculated
air over the surface of a heat storing boiler or the surface
of a heating boiler.
The cover means of the insulated cultivating areas may also
be constructed in such a manner that the lateral enclosure
is made up of enclosure elements which are, for example,
adapted to be telescoped in relation to one another and in
relation to end enclosure elements, this being made pos-
si~le by arranging for the said elements to be slidably sup-
ported by the periphery of the bottom tub, said elements being
adapted to cooperate in a gastight manner with the peripllery
of the tub and in relation to one another at least in tllc
vicinity of the tub periphery, said elements, on the one
?5 hand, a~fording the necessary access to the crops and, on
the other, defining enclosures for the crops, said enc~osures
having as small an internal air volume as possible.
Accurate control of temperature within the individual culti-
vating areas can be effected by directly connecting sald
_4_
lzl5z27
Areas to heat and cold sources~ It is not necessary to pro-
vide sunshades of the type conventionally employed with hot-
houses, with the result that the available light can be utilized
in an optlmum manner for the promotion of plant growth.
It is also possible, for insulating the bottoms of individual
separated cultivating areas, to employ commercially available
surface heating elements which are provided with heating units
which are integrated in heat insulating elements of sheet form.
Such elements may be disposed in the soil at a suitable depth
under the respective cultivating areas and may simultaneously
serve to insulate the soil from its surroundings and for
selective heating of the soil.
In order to permit a gastight connection to be established
between said lateral enclosure and the periphery of the bottom
tub~ it is possible to employ a tub having a rim of gutter
shape~ said gutter being adapted to receive, in addition to
the guide means for said slidable lateral enclosure elements,
a liquid~ particularly water for the purpose of establishing
said gastight connection in an extremely simple manner. In
order to prevent the gutter from losing water due to overflow,
the gutters are conveniently provided with overflow weir
sections adapted to direct overflowing water to the interior
?5 of the tub.
In order even further to reduce the consumption of carbon
dioxide gas and heat energy~ it is of advantage to provid~
for the individual soil-containig tubs associated with lndi-
vidual cultivating areas disposed side by side to be movable
_10--
~2~5Z'~7
in a lateral direction, i.e. transversely of their longitudinalaxes, so as to permit, if desired~ to combine all tubs dis-
posed side by side into a compact block. This makes it pos-
sible, particularly during the night, drastically to reduce
the heat transfer surface between the interior of the culti-
vating areas and the interior of the hothouse. In order to
permit this scheme to be put into practice, the soil tubs
are provided with flexible conduits enabling the tubs to be
connected, as requiredS to a heat source, a watering source,
the carbon dioxide gas source, and/or an air circulating system
as well as a coolant source.
Each individual cultivating area may have associated there-
with sha~ing means which, however, are not employed for the
purpose of keeping away sunlight but are intended for use
during the nig~t in order considerably to-reduce h~at losses
of the cultivating areas during growth intermissions. For
this purpose, the shading means, with are constructed as roller
or Venetian blinds, are adapted to be withdrawable or adjust-
able in a horizontal plane above the upper cover of eachcultivating area, and their width is larger than the width
of the appertaining cultivating area. ~here this arrangement
is employed, the soil tubs are pushed together in the evening,
and the shading means are closed, said shading means being
adapted to overlap one another so as to form a tight heat
insulating str~cture on top of the block.
The employment of the features of the invention enables such
a high amount of energy to be saved that it is also possible
d~ring the cold season continually to operate the hothouse.
~5Z~7
By employing plain glass panes in the external shell of the
hothouse~ light losses are reduc~d to a minimum, and unavoid-
abie light losses are further compensated for by the con-
tinuous introduction of C02. As regards the tunnel sections~
5 whiCh for the most part consist of twin-wall transpatent material,
it is, of course, also possible to employ artificial light
sources. It is further possible to install in outdoor areas
the entire system or parts thereof, such as the tunnel coversO
Furthermore it is possible to employ shading means which, in-
stead of being individually associated with said tubs, con-
stitude a panel covering the entire arrangement and provided
with light transparency adjusting means so as to resemble
a swimming pool roof.
~Jhere it is intended individually to condition the air in
the cultivating tunnels, it is also possible, for supplying
warm or cold air, also to employ enclosed cavities provided
in the non-transparent part of the lateral enclosure with the
result that an additional insulating effect is obtained.
The individual insulated cultivating areas may be inter-
connected and further connected to a central heat, sprinkling
water and carbon dioxide supply system which is adapted to
connect to the supply system either individual cultivating
areas or a plurality of such units, this enabling ~rowth
conditions to be easily adapted to different crops. More-
over, this arrangement affords the possibility of providing
automatic control in a simple manner, there being provided 7
at strategic points~ temperature, humidity and/or carbon
dioxlde sensors~
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Z7
According to the invention9 it is easily possible to modern-
ize old hothouses so as to permit them to be operated in a
profitable manner throughout the year~
In the manner described, it is possible fully to utilize the
heat energy expended to promote plant growth. Thus, it is
possible to operate a hothouse along modern lines employing
conventional heating methods, i.e. without utilizing natural
energy, operating costs being relatively low. Another feature
lo resides in the fact that accurate metering of the carbon
dioxide content of the air wlll result in the growth of
the crops being accelerated to a large extent particularly
also in low-light seasons, with the result that profitability
will also be in~reased by a considerable improvement in the
crop quantities
In summer, i.e. with sufficient amounts of light and heat
available, it is possible, depending on prevailing conditions,
to operate the hothouse in the conventional manner if this
should be desired by opening of removing the cover means.
During seasons in which less light is available, the hot~
house of the invention permits accurate control of heat,
humidity and C02 supply.
The conventional dimensions of crop bed enclosures employed
in hothouses may be retained for use with the soil insulating
tubs. The individual insulated sections are connected in
series or in parallel to a central supply system. Each
insulated area is provided with at least two inputs and two
outlets for the heating medium and, as desired~ for irrigatlng
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~L5;~7
water, nutritive solutions, C02-bearing water or C02 gas.
Where a surface irrigation system is available or can be
easily installed, the supply line may have a pressure im~
pregnating device associated therewith which is adapted to
be connected to a source of pressurized carbon dioxide~ e.g.
a pressuri~ed gas cylinder.
It is possible to employ a conventional carbonizer for im-
pregnating water with carbon dioxide gas. The cooled lmpreg-
nated water is first brought down to the irrigating pressure,
mixed with additional water until the proper temperature is
reached and then sprinkled gently over the soil.
However, it is also possible to enclose a supply of water
(without cooling) in a pressure cylinder or tank and to employ
the pressure of a carbon dioxide cylinder or tank for pres~
surizing and impregnating the water.
The gas pressure may be employed advantageously for circulating
the water and for irrigating the crops. It is possible to
employ, instead of water, nutrient solutions containing cer-
tain minerals and trace elements~ It is only when the irri-
gation water impinges on the soil that the physically combincd
gas will be released to form a C02 layer over the 5011 wlth
the chemically combined carbon dioxide being introduced into
the soil together with the water for the purpose of regulating
the pH value. A quant1ty of approximately 0.1% H2C03 may be
introduced into the soil by the water supplied to it.
3~
-14-
~Z~5~7
BRIEF D~SCRIPTION OF THE DRAWINGS
The invention and further particulars will be described
more speci~ically hereinafter with reference to a preferred
embodiment shown in the drawings, in which:-
Figure 1 shows a partially broken-away perspective view of
of an e~bodiment of a hothouse according to the
invention; and
0 Figure 2 sho~s an enlarged cross-sectional view of a single
insulated cultivating area located wlthin the hot-
house.
The hothouse 1 shown in Figure 1 may be of conventional con~
struction, i.e. it may be a frame structure and glazed with
single panels. It may also be an existing hothouse which has
been adapted to suit the purposes of the invention.
Disposed within the hothouse 1 are a plurality of individual
cultivating areas which are separated ar,d insulated from other
cultivating areas, from the interior of the hothouse and from
its floor, said areas being separated both spatially and
as regards the heat to which they are exposed. In the cmbodi-
ment shown, two sets of such insulated cultivating areas are
provided~ith said areas of one of said sets being oriented
transversely of the longitudinal axis of the hothouse com-
prising side walls 3 and a roof surface 2, whereas thc other
set of areas is oriented in the direction of the longitudinal
axis. Thus~ there are provided a plurality of individual
cultivating areas 4~
_15-
~s shown in Figure Z, each cultivating area 4 cornprises a
thermally insulated soil tub ~, the interior 9 of which is
intended to receive the cultivating soil. It is, of course,
also possible directly to place the soil tubs on the 1Oor
of the hothouse or to bury them in the floor. Each soil tub
may also have embedded therein an insulated heating device.
In order to simplify operation and to facilitate the car~ of
the individual cultivating areas~ the individual soil tubs
8 are, for example, mounted on carriages 5 supported by floor
6 and movable to and fro in the direction of the double-
headed arrow 7 so as to make it possible, as shown in Figure 1,
to push the tubs together so as to form closed blocks and to
permit the tubs to be moved apart to permit the necessary
operations to be performed. This is applicable in an
analogous manner to stationary tables provided with table
tops which are arranged to be moved within certain limits.
In the embodiment shown, each soil tub is provided with an
apron 8a having a U-shaped cross section and opening in an
upward direction; it being possible to provide said apron
with a water filling 8b. In Figure 2T such an apron is shown
on one longitudinal side of a soil tub only. However, such
aprons are provided on both longitudinal sides of each soil
tub The end -faces of the soil tubs are convenlently pro-
vided with stationary end wall members 12. Towards thelon~ltudinal sides as well as in an upward direction, the
cultivating area is covered in the embodiment shown by means
of a U-shaped hood 10 whose lateral parts 13 telescopically
extend over the side walls of the soil tub 8 and are immersed
in tile water filling 8b of the aprons 8a of the soil tub
-16-
~5;2 ~7
so as to effect a seal in a simple manner. By means of sus-
pension cables or the like (not shown) it is possible, as
diagrammatically indicated at 15 in Figure 2, to lower and
raise the soll tub as desired in order to match the internal
volume of t~e enclosed cultivating area with the height to
which the plants have grown and thus to reduce said volume
to a minimum. The fact that the hoods 10 may be raised and
lowered is indicated in Figure 2 by the double-headed arrow
11. The end walls of the tub may extend upwardly beyond the
hood 10 so that a seal is effected therebetween regardless of
the elevation of the hood. Where necessary, it is possible
to provide suitable sllding seals between the respective com-
ponents. Both the end walls and the hood are made of twin-
wall transparent material, thus separating the interior there-
of from the interior of the hothouse and affording thermalinsulation. Each individual cultivating area is connected
by means of one or more flexible conduits or lines to a
heating device which may, for example, be connected thereto
at 16, further to a line 19 adapted to supply gaseous C02,
another line 20 permitting C02-impregnated irrigating water
to be introduced and still another line 21 permitting ir-
rigating water or a nutrient solution to be supplied to the
cultivating areas. Fertilization with C02 is effected by
means of irrigating water supplied via line 20, it being pos-
sible rapidly to supply large amounts of C02 via gas line 19.
Humidity control is conveniently effected with each individualcultivating area via a drying device 17 of compact design
which, by condensing excessive humidity~ also serves to obtain
irrigati~g water~ The drying device 17 may be connected to
-17-
~z~
an air circulating system ~ia line 18.
Wlth each cultivating area there may be associated a Venetian
blind 23 supported by rails 22 provided on the hood, said
blind normally remaining open during the daytime in order to
permit unrestricted entry of light. During the night, the
cultivating areas may be pushed together as shown in Figure 1
to form a block, with the result that the blind-like covers 23
which are then in their closed position will overlap mutually
so as to provide additional heat protection for the crops
towards the interior of the hothouse.
In Figure ~ one of said blocks bears the reference number 30.
The plants absorb the carbon dioxide primarily through slit-
shaped apertures present on the under sides of their leaves.
Alnong other things~ the rate of absorption strongly depends on
humidity. The closing capability of said apertures is de-
termined, among other things, by the water content of the
plants and by humidity in their s~rroundings. The dryer the
air and the plants, the smaller the water content of the closing
cells and the larger the extent to which the apertures will
close Thus, it is possible, by controlling humidity in the
manner described, additionally to influence the amount of C02
absorbed by the plants.
With the new arrangement it becomes possible - contrary to
common hot houses - to grow most different cultures of remarkably
different climatical needs in one and the same house.
Of the water contents of plants only two percent contribute to
the growing of cells while 92% of water evaporate, With the
new system for rontrolling the air humidity it is possible to
completely regain these 98% of evaporated water. This is of
advantage particularly in regions poor of water.
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