Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AEROPONICS SYSTEM
The present invention relates to an aeroponics system, in particular an
aeroponic
propagator for the cultivation of plants.
Aeroponics is a development of hydroponic methods. Hydroponics is the
technique
of growing plants in water-based solutions of nutrient salts. Although known
over 100 years
ago it was not used extensively until the Second World War, when it was used
to provide
troops with green vegetables in parts of the world where normal methods of
cultivation were
impractical. Hydroponics has since been widely used in many countries and has
proved
particularly popular in oil producing countries with desert climates.
A hydroponic system known as the nutrient film technique (NFT) was developed
during the 1960s at the UK's Glasshouse Crops Research Institute by Dr. Alan
Cooper.
Although widely acclaimed as a significant advance in hydroponic growth
techniques it has
a number of drawbacks. The main ones being that - though simple in concept -
it tends to be
expensive to install and often has been difficult to operate profitably
because of disease and
nutrient control problems. In spite of these limitations, NFT's appeal to
growers is such that
it has been used in more than 70 countries.
Aeroponics has gained much publicity over recent years. It is defined by the
International Society for Soil-less Culture as "A system where roots are
continuously or
discontinuously in an environment saturated with fine drops (a mist or
aerosol) of nutrient
solution". The method requires no substrate and entails growing plants with
their roots
suspended in a chamber (the root chamber), with the roots periodically
atomised with a fine
mist or fog of nutrients, a process which uses significantly less water than
alternative
growing techniques. Since their inception some 30 years ago, aeroponic
techniques have
proved very successful for propagation and are widely used in laboratory
studies of plant
physiology, but have yet to prove themselves on a commercial scale. Aeroponics
could also
have applications in crisis situations as an aeroponics system can be designed
to work in the
event of such things as reduced solar radiation levels (e.g. due to high
levels of fine volcanic
ash particles in the atmosphere) or floods.
However, there are two main limitations associated with commercial aeroponic
systems: high equipment costs and low equipment reliability.
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The present invention aims to at least partly overcome these limitations,
desirably by
at least partly fulfilling one or more of the following objectives;
a) increasing productivity by:
= at least increasing by 50% the growing surface per unit of land covered
by the
system
= improving nutrient uptake in the root areas
= producing faster growth
= improving growth through foliar feeding in leaf areas
= less waste due to disease
= less waste due to insect attack
b) cutting costs by:
= simplifying the way the plants are protected from bad weather, insect
attack etc.
= providing easy access to the root areas (e.g. so potatoes can be picked
only when
they reach a particular size)
= cutting the level of fertilizer needed
= cutting or eliminating the need for insecticides
= reducing or eliminating the need for herbicides
= significantly reducing the water requirement compared to other
cultivation methods
= using simple and reliable equipment to monitor and control growing
conditions
= minimising use of permanent structures, concrete foundations, ground
levelling, etc.
= collecting and storing rainwater and dew in-situ.
According to one aspect of the present invention there is provided an
aeroponic
propagator for the cultivation of plants, the propagator preferably
comprising: two end
frames; a first support member extending between the two end frames; and a
substantially
opaque sheet for supporting plants to be cultivated, wherein the substantially
opaque sheet is
suspended from the first support member to form at least one sidewall of a
chamber between
the end frames for roots of plants supported on the opaque sheet.
Advantageously, such an aeroponic propagator is both reliable and
comparatively
cheap to construct. The propagator is simple in construction, meaning that
there are only a
limited number of parts that could go wrong. Further, because the limited
number of parts is
individually simple, there is little opportunity for the propagator to fail.
The simple
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construction also means that the propagator is particularly useful on sloped
land, because the
propagator could be erected without the need for terracing the land first.
The substantially opaque sheet preferably blocks at least 75% of light from
passing
through the sheet, more preferably at least 85% of light, even more preferably
at least 90%
of light, and still more preferably at least 95% of light.
The propagator is easily customisable. For example, the overall length of the
propagator can be easily adjusted by moving the end frames closer or further
apart, and the
supporting member can be lengthened and shortened accordingly. This is
especially
advantageous when the supporting member is a rope or line, because they may be
easily
adjusted in length. This means that the propagator can be easily adjusted to a
particular use.
The aeroponic propagator can comprise an end panel arranged to close an end of
the
root chamber. Such a panel can be provided at both ends of the root chamber.
The end
panel can comprise a vent flap, which can be remote controlled. Accordingly,
the inside of
the propagator can be effectively sealed from the outside, thus providing an
enclosed space
which can be provided with a controlled environment. The use of vent flaps
allows the
internal environment to be vented to the outside, in the event that the
internal environment
becomes undesirably hot or pressured for example.
The aeroponic propagator can comprise a repositioning device to reposition the
first
support member to tilt and / or fold the root chamber. The repositioning
device can be a
means for tilting and / or folding the two end frames. Accordingly, the
propagator root
chamber, which forms the main bulk of the propagator, can be repositioned.
This is useful
when two or more propagators are arranged in close proximity, such as in
farming
conditions. Repositioning of the root chamber allows for access between the
propagators,
for example for observation, maintenance or harvesting.
The substantially opaque sheet is preferably reflective, and can comprise UV-
stabilised plastics and/or a waterproof paper layer. Accordingly, the sheet
reflects back
sunlight incident on the sheet towards the foliage of plants supported on the
sheet. This
provides the plants with additional light for photosynthesis and thus helps
increase the rate
of plant growth. The provision of UV-stabilised properties for a plastics
sheet and
waterproof properties for a paper layer ensure that the sheet is durable in
all weather
conditions and improves the reliability of the propagator.
The aeroponic propagator can comprise a second support member extending
between
the end frames, wherein the substantially opaque sheet is suspended from both
the first and
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second support members. The use of two, rather than one, support members
provides a
trapezoidal shape, rather than a triangular shape, to the root chamber. As
such, there is
increased space between the plants on either side at the top of the root
chamber, which may
preferable when growing certain plants, for example those with large root
systems.
The aeroponic propagator can comprise a tensioning mechanism, preferably a
winch,
for tightening the first and/or second support members, when they are flexible
(for example,
when the support members are ropes or lines). This allows for the adjustment
of the tension
in the support members that can be used to alter the height of the root
chamber, for example.
In addition, this makes it easier to change the length of the propagator (for
example by
moving the end frames) because it is then a relatively simple operation to re-
adjust the
support members to the correct tension. The first and/or second support
members can be
lines such as an ultra high molecular weight polyethylene rope or recombinant
silk, because
this is durable and therefore appropriate for use in all weather conditions.
The chamber can be suspended above the ground. As such, the root chamber can
be
totally separated from the ground, which can be desirable in outside
locations, for example,
to keep the plant crops away from animals or where the ground is not level.
The suspended
root chamber also allows for other equipment associated with the propagator to
be stored
under the root chamber.
The root chamber can further comprise a chamber base, for carrying an energy
crop
or mushrooms for instance. The root chamber base can be supported by third and
fourth
support members, each extending between the two end frames below the first
support
member. The root chamber sidewalls are releasably secured to the third and
fourth support
members, and the third and fourth support members can be repositionable to
alter the shape
of the root chamber. The base of the root chamber can thus be held in a fixed
shape or
repositioned according to the need, and access to the insides of the root
chamber can be
obtained through releasing the sidewalls from the third or fourth support
members.
The aeroponic propagator can comprise a drainage point positioned at the
lowest
point in the root chamber base for draining the energy or mushroom crop. This
allows
cultivation of algae, for example, in the base that can be easily removed and
used for
example as a bio-fuel.
The ground, which may be any surface on which the propagator is positioned
(e.g. a
roof-top), can form the base of the root chamber or directly support the base
of the root
chamber when the base comprises, for example, a sheet of plastic. As such, the
root
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chamber is not suspended, and is thus simpler in construction. The
substantially opaque
sheet can be releasably anchored to the ground at the base of the sidewalls,
so forming the
root chamber without the use of extra support members such as rigid or semi-
rigid tubes, or
flexible support members such as ropes or lines. Optionally, the sidewalls can
be anchored
via the use of water-containing tubes (i.e. tubes filled or partially filled
with water). The
tubes can be flexible. When the tubes extend along the length of the
propagator, this
arrangement can provide a seal between the opaque sheet and the surface on
which the
propagator is provided, thereby sealing the foliage chamber from the outside
environment.
The aeroponic propagator can comprise a fogging system to supply a fog to the
root
chamber. The fogging system can be arranged to collect moisture from the root
chamber
and re-circulate the moisture in the fog. This allows for roots in the root
chamber to be
provided with nutrients in the most efficient manner, and minimises wastage by
recycling
unabsorbed water and nutrients.
The aeroponic propagator can further comprise a substantially transparent
sheet
arranged over the substantially opaque sheet, so as to form at least a partial
enclosure around
the root chamber. As such, a space or gap is formed between the two sheets, in
which
foliage can grow and which can be referred to as a foliage chamber. The second
sheet thus
protects the foliage from the surrounding environment, for example preventing
birds from
eating the crops and further reducing the need for insecticides, herbicides
and fungicides.
The aeroponic propagator can comprise a blocking device for blocking a gap
between the root chamber and the transparent sheet. In particular, at the base
of the
propagator the gap between the lower edges of the two sheets can be blocked
and preferably
sealed to contain the atmosphere in the space between the two sheets.
The aeroponic propagator can comprise a vent in the transparent sheet above an
uppermost point of the root chamber, and can further comprise a blocking
device for
blocking the vent in the transparent sheet. This allows for regulation of the
environment
within the space between the sheets by blocking and unblocking the vent,
controlling the
flow of air and/or gas and/or fog into the space between the sheets.
Preferably, the blocking devices each comprise an inflatable tube. This is
simple and
cheap to construct and operate, whilst also providing a cushioning effect that
helps ensure as
good a seal as possible.
The aeroponic propagator can comprise a fogging system to supply fog, with a
median droplet size of 1 to 60 microns, to the space between the root chamber
and the
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partial enclosure, i.e. the foliage chamber. Preferably the median droplet
size is 20 microns
or less, more preferably 10 microns or less and still more preferably 5
microns or less. This
allows for the use of foliar feeding, which increases the growth rate of the
plants being
cultivated. Similarly, the aeroponic propagator can comprise a system for
supplying carbon
dioxide rich air and / or temperature controlled air (which can include air
that has been
heated or cooled) to a space between the root chamber and the partial
enclosure, i.e. the
foliage chamber, once again to increase the plant growth rate. The fog and /
or carbon
dioxide rich air and / or temperature controlled air can be applied to both
the root and foliage
chambers simultaneously.
According to another aspect, there is provided a kit of parts for an aeroponic
propagator for the cultivation of plants, the kit comprising two end frames, a
first support
member and an opaque sheet for supporting plants to be cultivated.
According to another aspect, there is provided a method of cultivating plants
using
an aeroponic propagator of the first aspect, the method comprising: supporting
plants on the
opaque sheet so that the plant roots project into the root chamber and the
plant foliage
projects outside the root chamber; and supplying a nutrient-containing fog to
the root
chamber for absorption by the plant roots.
The method can further comprise supporting plants on the opaque sheet so that
the
plant roots project into the root chamber and the plant foliage projects
outside the root
chamber; and supplying at least one of a nutrient containing fog or carbon
dioxide rich air or
temperature controlled air to the space between the root chamber and the
partial enclosure,
i.e. the foliage chamber, for absorption by the plant foliage.
According to another aspect, there is provided an aeroponic propagator for the
cultivation of plants, the propagator comprising: a substantially opaque sheet
for supporting
plants to be cultivated; and wherein the substantially opaque sheet comprises
at least one
pleated section for supporting the plants. The pleats make it easy for plants
to be provided
on the sheet and help support the plant during growth and additionally provide
means of
increasing space between plants by stretching out the pleats as the plants
grow, hence
increasing the usable area.
The present invention will be described with reference to exemplary
embodiments
and the accompanying Figures in which;
Fig. 1 is a schematic perspective view of an aeroponic propagator;
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Fig. 2 is a side view of the end of an aeroponic propagator;
Fig. 3 is an end view of the aeroponic propagator of Fig. 2;
Fig. 4 is a perspective view of the end of another aeroponic propagator;
Fig. 5 is a cross-section through a propagator with inflated vent seals;
Fig. 6 is a cross-section view of the propagator of Fig. 5, but with deflated
vent seals;
Fig. 7 shows three views of propagators in different tilted and folded
positions;
Fig. 8 shows cross-sections through propagators that are not suspended above
the
ground;
Fig. 9 shows similar propagators to those in Fig. 8, but with a double-layer
construction;
Fig. 10 shows the arrangement of a fogging system and the end of a propagator;
Fig. 11 shows the arrangement of a fog return pipe and condensate sump at the
opposite end of a propagator to that shown in Fig. 10;
Fig. 12 is a schematic plan view of a covered system of propagators.
Fig. 13 is a schematic perspective view of another aeroponic propagator;
Fig. 14 is an end view of the end of the aeroponic propagator of Fig. 13;
Fig. 15 is a plan view of two aeroponic propagators similar to those shown in
Fig.
13;
Fig. 16 is a perspective view of a section of a propagator using a pleated
sheet
covering;
Fig 17 depicts a supporting framework for a pleated sheet such as depicted in
the
Fig. 16;
Fig. 18 is a detailed view of how a pleat may be formed and supported;
Fig. 19 depicts how several pleats may be held in place; and
Fig 20 depicts alternative pleat arrangements, Fig. 20a showing how a seed
stick can
be supported in a pleat and Fig. 20b showing how netting may be used to form
the pleat.
In the Figures, like parts are identified by like reference numbers.
Figs 1-3 show various views of an aeroponic system, which is an example of an
aeroponic propagator 1. The system of Figs 1-3 comprises a root chamber 14
that is
suspended over the ground. The ground may be the earth, in a field for
example, or another
surface such as a roof-top. The suspended configuration simplifies
installation and avoids
the need for the ground levelling associated with hydroponic systems that
operate under
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glass or polytunnels. Therefore, the surface need not be totally flat. The
suspended
arrangement is also advantageous in arid environments, as it allows dust and
sand to be
blown under the root chamber 14, instead of being blown against the side of
the root
chamber 14. This prevents the accumulation of dust and sand against the sides
of the root
chamber 14, and allows for easy access along the length of the propagator 1 to
be
maintained.
For normal operation, the root chamber may be suspended up to about lm above
the
ground, and preferably about 0.5m to 0.7m above ground level to enable ease of
use, for
example allowing easy reach to the plants 16 during harvesting or cultivation.
However, the height of the root chamber may be adjustable, for example by the
use
of supporting end frames 11 that can extend (e.g. by means of a telescoping
mechanism), so
that the root chamber can be raised in the event of a flood, for example.
In Figs 1-3, at each end of the propagator 1, a strong triangulated tubular
structure 11
is supported on tubular steel screw piles driven to the required depth for
local ground
conditions. These are examples of end frames. However, end frames 11 may have
other
constructions, and need not be triangular or constructed from tubular
materials or supported
on piles. Where there is little or no soil, i.e. on bare rock, the end frames
11 could be set on
plates attached to the ground with expanding bolts (as for example, in Fig.
4). That is, the
end frames 11 may be supported by any means suitable for the terrain.
Although not shown, the propagator 1 may additionally include one or more
supporting frames between the two end frames 11. This construction may be
desirable when
the propagator is especially long, to provide extra support for the supporting
member 12 and
the sheets 13, 35.
Fig. 4 shows an alternative propagator 1, with a different end frame 11 to
that shown
in Figs. 1-3. In Fig. 4, the end frame 11 comprises a substantially upright
post with a spar
connected cross-wise to the post. The spar and the post are connected at pivot
point 45.
Figs. 13-15 show another alternative propagator 1. In this case, end frame 11
is a
mast, which is braced against the ground (or other surface underlying the
propagator 1). The
mast 11 can be attached to the ground via a base plate 131 (as shown in Figs.
13-15). The
mast 11 can be positioned so that the base plate 131 is positioned underneath
the root
chamber 14, and is held in position by the suitable arrangement of lines 12
and 31, which act
as support members and which may be tensioned using winches or turnbuckles 21
for
example, and which may further be terminated by screw pile caps 101 for
example. A rope
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frame 132 can also be used to provide a suitable shape to which to attach the
lines 12 and
31. Of course, other arrangements of lines to those shown in Figs. 13-15 may
be used.
Fig. 15 shows how two propagators similar to those shown in Figs. 13 and 14
may be
arranged next to each other. In the arrangement shown, the propagators 1 are
immediately
adjacent each other at the gutter position 151 between the two ridgelines 12.
However, a
space between the propagators 1 may be opened up through tilting and/or
folding methods
as described in greater detail below.
As is clear in Fig. 15, the films or sheets 13, 35 can extend all the way to
the point at
which the mast 11 meets the support member 12. That is, the mast 11 can be
within the root
chamber 14. In that case, the sheets 13, 35 can extend all the way to the
frame 132, and the
frame 132 can be covered by a closer panel 34, such as those discussed in more
detail below.
In the propagators 1 of Figs 1-4 and 13-15, to keep the structures that
enclose the
plants 16 as simple and cheap as possible, they are made of either one or two
sheets or films
- an inner sheet 13 and an outer sheet 35. These films or sheets 13, 35
preferably have good
tear, UV light and/or weather resistance characteristics. However, the inner
sheet 13 may
have different characteristics to the outer sheet 35.
Either one or both of the inner and outer sheets 13,35 can comprise a single
layer of
material or two or more layers of material. For example, it may be desirable
to have two or
three layers to provide extra insulation for the propagator 1, thereby
protecting the plant
roots and/or foliage from frost in cold climates, for example.
The external face of the inner film 13 is preferably substantially opaque (so
that the
root chamber 14 is kept dark). The root chamber 14 is desirably kept as dark
as is required
for normal growth of the particular crop being cultivated, and the inner film
13 is desirably
sufficiently opaque to achieve this. The inner film 13 is also desirably
sufficiently opaque to
prevent the growth of algae on the plant roots inside root chamber 14.
The substantially opaque sheet preferably blocks at least 75% of light from
passing
through the sheet, more preferably at least 85% of light, even more preferably
at least 90%
of light, and still more preferably at least 95% of light.
The inner film 13 carries the full weight of mature plants 16. The plants 16
can be
attached to the inner film so that they pass through a hole in the inner film
13, so that the
plant roots are within the root chamber 14 and the plant foliage is outside
the root chamber.
The plants 16 may be attached by any suitable means, for example being simply
supported
by a resilient plastic or paper grommet around the hole in the inner sheet 13
or the use of
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some form of clip to hold the plant to the inner sheet 13. Netting or
stretchable membranes
around the plants 16 and/or the holes in the inner sheet 13 may also be used.
Such netting or
membranes could be arranged in the form of a pouch or pocket around the hole
in the inner
sheet 13. It is preferable that any such netting or membrane is porous.
The inner film 13 is preferably made of a limited stretch, rip resistant, UV-
stabilised
plastics film. For example, the inner film 13 may be made nanocellulose (also
called
microfibrillated cellulose). Nanocellulose can be produced with high energy
efficiency, for
example using processes developed by Innventia AB of Stockholm, Sweden.
Alternatively,
strong waterproof paper with a stretch plastics film (that is UV-stabilised)
outer surface
could be used. In all cases, it is preferable that the outer face of the inner
film 13 is
reflective, and preferably white. This reflective face helps keep the root
chamber 14 cool in
strong sunlight, and reflects light back into foliage supported on the inner
film 13 to boost
photosynthesis and therefore growth rates.
The inner film 13 forms at least the sidewalls of the root chamber 14. The
inner film
13 may be a continuous piece of material forming both sidewalls of the root
chamber 14, or
may be separate pieces of material (for example, each forming a different
sidewall or part of
sidewall). Further, the base 15 of the root chamber 14 may also be part of a
continuous
sheet 13 forming the sidewalls of the root chamber 14. Alternatively, the base
15 may be
made from a separate piece of material.
In the Figures, the overall weight of plants 16 and the film 13 is carried by
a
centrally positioned rope or line 12, which may be made of a metal such as
steel or
Dyneema (RTM) (ultra high molecular weight polyethylene), or equivalents. The
line 12
may be tightened and loosened via a lever operated winch 21, for example, as
shown in Fig.
2. However, instead of a rope or line, an alternative supporting member 12 may
be used.
For example, the supporting member may be rigid or semi-rigid (for example
having hinged
portions) and could be a steel or plastics tube for example. One or both ends
of the
supporting line 12 may be further secured to the surface on which the
propagator 1 is
situated.
The sheet 13 may be secured to the supporting member 12 via any appropriate
method, such as strong acting clips similar to large plastics clothes pegs or
by using the
deadweight of water, such as in water-filled tubes 39 in Fig. 3 for example.
As shown in Fig. 3, each end of the root chamber 14 is provided with a closer
panel
34. Preferably the closer panel 34 is rigid and blocks the end of the root
chamber 14, and
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more preferably forms a seal. At one end of the root chamber 14 the closer
panel 34 may
have holes in it through which fog nozzles can discharge fog into the root
chamber 14. It
may also have further holes, through one of which a ventilating fan blows air
into the root
chamber 14 and through another of which recycled fog is exhausted into the
rear of a
ventilating fan housed in the fogger/control unit 23. The fogger/control unit
23 is discussed
in more detail below.
At the other end of the root chamber 14, the closer panel 34 may have a vent
flap 36
that allows air and fog to escape to the open air. The vent flap 36 is
preferably remote
controlled and may be activated in the event of overheating problems occurring
in the root
chamber, during hot weather for example, and additionally to maintain the
desired or ideal
growing conditions in the root chamber. Activation of the vent flap 36 or
other control
mechanisms can be automated by the use of temperature, carbon dioxide, leaf
turgor and/or
humidity sensors provided, for example, within the root chamber 14 or the
foliage chamber
55. For example, when the sensors register an unacceptable set of conditions
within the root
chamber 14, the control unit 23 can activate the vent flap 36 to allow
external air to mix with
the atmosphere inside the root chamber 14. Once the atmosphere inside the root
chamber 14
has returned to acceptable conditions, the control unit 23 can close the vent
flap 36. The
specific parameters for operating the control system will depend on the most
suitable
conditions for the plants 16 being cultivated.
The vent flap 36 may be part of a system for supplying air to the root chamber
14
and/or foliage chamber 55. The system may comprise a control unit that
controls the system
in response to the use of oxygen monitors within the root chamber 14 or
foliage chamber 55.
For example, if the oxygen monitors detect that the level of oxygen in the
root chamber is
too low, the vent flap 36 is automatically opened to allow flow of air into
the chamber to
increase the oxygen levels. The flow of air into the chamber may be further
assisted, for
example, by the use of a fan. Once the level of oxygen in the root chamber 14
returns to a
suitable level, the vent flap may be automatically closed. As such, the
conditions inside the
root chamber 14 can be maintained for optimal growth. Once again, the specific
parameters
for operating the control system will depend on the most suitable conditions
for the plants 16
being cultivated.
In some cases it may be desirable for the system supplying air to the root
chamber to
comprise a filter to filter any air coming into the root chamber 14, to ensure
that the
conditions inside the root chamber are sterile. This would also be desirable
when growing
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pharmaceutical crops. The air can be filtered to remove micro-organisms such
as fungal
pests, for example.
In some cases (see, for example, Figs. 7 and 8) the outer sheet 35 may not be
required. For example, if foliar feeding of plants 16 is not used and insect
or bird attack and
disease are not problems for the particular crop being cultivated and local
conditions, the
outer sheet 35 may be omitted. This allows for further simplification of the
propagator 1.
As for the inner film 13, the outer film 35 is preferably made from a UV-
stabilised
plastics film or a nanocellulose material. The outer cover sheet 35 is
preferably substantially
transparent to visible light to allow the maximum amount of light to reach the
leaves of the
plants 16.
In particular, the cover sheet 35 is desirably transparent enough to allow the
plants
16 to grow and photosynthesise normally. It is particularly preferable that
the cover sheet
35 is transparent to red and blue wavelengths. For the red light, the cover
sheet 35 is
desirably transparent at a wavelength of approximately 660 nm, more preferably
transparent
over the range of 645 to 700 nm and more preferably transparent over the range
of 630 to
740 nm. For the blue light, the cover sheet 35 is desirably transparent at a
wavelength of
approximately 460 nm, more preferably transparent over the range of 450 to 475
nm and
more preferably transparent over the range of 440 to 490 nm.
Desirably, the cover sheet 35 is transparent enough to allow illumination of
100 to
200,000 lux at red and blue wavelengths.
The outer film 35 is supported by lines 37 and 38, which can be of similar
construction to line 12 and may be separately tensioned and positioned.
Support members
37 support the outer film 35 from the top of the propagators, whilst support
members 38
support the outer sheet towards the bottom of the root chamber 14 and hold the
outer sheet
35 away from the inner sheet 13. The film 35 may also be weighed down at the
bottom, for
example using compartmented water-, soil- or stone-filled tubes 39.
The area between the outer sheet 35 and the root chamber 14 provides an outer
foliage chamber 55 for the foliage of plants 16 supported on the inner sheet
13. This outer
root chamber may be blocked, and preferably sealed, at the bottom by the
provision of an
inflatable vent seal 33, for example. This is shown in Fig. 3, and is further
demonstrated in
Figs. 5 and 6 that show cross-sections through a propagator using inflatable
vent seals 33.
In Fig. 5, the vent seals 33 are inflated, whereas in Fig. 6 the vent seals 33
are deflated.
Similarly, the outer sheet 35 may be provided with a vent at the top of the
propagator 1. As
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such, the outer sheet 35 may be one continuous sheet, or it may comprise two
or more
separate parts. As shown in Figs. 3, 5 and 6 the upper vent may be blocked,
and preferably
sealed, via an inflatable vent seal 32 similar to the lower vent seals 33. The
upper inflatable
vent seal 32 can attach to the propagator 1 via any suitable connecting
mechanism 32a.
As with the vent flap 36, the operation of the inflatable seals 32, 33 may be
controlled automatically by the use of feedback from sensors, e.g.
temperature, humidity,
leaf turgor or gas sensors. For example, by using temperature sensors in the
outer foliage
chamber 55 to detect when temperatures rise in the outer foliage chamber 55 to
levels where
plant growth is affected, the control unit 23 can be activated to deflate the
seals 32 and 33.
As shown by the arrows in Fig. 6, this allows external air to flow through the
outer foliage
chamber 55, which reduces the temperature in the outer foliage chamber 55.
Once the
temperature is returned to acceptable levels, the control unit 23 can re-
inflate the seals 32, 33
to maintain the desired temperature.
To provide access to the propagators 1 the end frames 11 can be temporarily
tilted
and/or folded inwards - thus releasing space for access between parallel rows
of propagators
1. In Figs. 1-4 and 13-15 the bottoms of the root chamber 14 are held apart by
tensioned
ropes 31 that bear the weight of the ground sheet or root chamber base 15. The
root
chamber 14 can be tilted or folded by pulling on ropes, or other suitable
supporting
members, 31. This tilting and/or folding operation creates a temporary access
space for field
workers between the propagators 1.
Fig. 7 demonstrates how the tilting and folding operation may occur. The left-
most
propagator 1 in Fig. 7 is arranged in the normal configuration for growing
plants 16. The
central propagator 1 has been configured so that the root chamber 14 is folded
or collapsed
upon itself by drawing the supporting members 31 towards each other. As such,
the inner
sheet 13 has been re-positioned and the base 15 has been folded. In the right-
most
propagator 1 in Fig. 7, the propagator 1 has been tilted. In this example, the
relative
positions of the supporting members 12 and 31 remain unchanged, so that the
tilted root
chamber 14 has the same cross-sectional shape as the untilted root chamber 14.
However, in
some embodiments, it may be desirable to both fold and tilt the root chambers
14 at the
same time.
To assist in the tilting and folding, the end frames 11 may also be configured
to
move position. For example, the Fig. 4 propagator 1 allows the tilting of the
root chamber
via the pivoting of the spar around pivot point 45 on the upright post. In
addition, the spar
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may contain a slot for the pivot point 45, so that the spar may move laterally
as well as
rotationally. Similarly, the position of the supporting members 31 on the spar
may be re-
positionable so that they can be brought closer to each other and therefore
allow the folding
or collapsing of the chamber 14.
The tilting and folding mechanism allows propagators to be positioned close to
each
other, and therefore increased productive surface area to be obtained per unit
area in plan
view. Desirably, the growing surface of the propagator is at least 1.5 times
the footprint (i.e.
the width of the base 15) of the propagator, and more desirably at least 2
times the footprint,
even more desirably up to 3 times the footprint, and still more desirably up
to 4 times the
footprint. In a preferred example, the growing surface is around 2.5 times the
footprint.
As shown in Fig. 4, when the supporting members are ropes or lines, the
tilting and
folding of the propagator can be achieved using re-positionable anchor posts
46 for the lines
12 and 31. In addition, lines 41 and 42 which are used to control the position
of the spar
relative to the post of the end frame 11 may also be attached to re-
positionable anchor post
46. As well as the anchor posts 46 being re-positionable, the relative
tensions in the lines
12, 31, 41 and 42 can be adjusted, preferably using turnbuckles or block and
tackle
arrangements 43 on the various lines. Similar methods could be used with the
propagators
of Figs. 1-3, rather than the winch 21.
In the embodiments of Figs. 1-3, the end frames 11 are constructed with an A-
frame
configuration. In this case, the diagonal sections of the A-frame may be re-
positionable
and/or hinged to the horizontal member of the A-frame, in order to allow the
diagonal
members to be re-positioned. As such, the diagonal members of the A-frame may
be
repositioned along with the chamber 14. In Figs. 1-3, the relative tensions in
the lines 12
and 31 can be controlled using the winch 21.
In the configurations of Figs. 1-4, the height of the lines 31 and the base 15
of the
chamber 14 can be adjustable to take account of the local terrain and field
worker access
requirements. As such, the space between the base 15 and the ground may be
varied. This
space may be used for fog return tubes 24 and rainwater storage bags, for
example, which
may can in direct contact with the ground. However, it is desirable that the
fog return tubes
24 are elevated above the ground (as shown clearly in Fig. 5 for example), in
order to avoid
creating condensation traps at dips in the ground. That is, by suspending the
fog return
tubes 24, the formation of local dips along the length of the fog return tube
24 can be
avoided, thus avoiding the collection of condensation in the pipe.
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The floor 15 of the root chamber 14 can, optionally, be used to grow mushrooms
or
algae varieties, or other energy crops 53, which grow in the dark when fed for
example with
suitably warm sugar-rich water solutions. Periodically the algae can be
drained off through
a remotely controlled valve outlet positioned in the root chamber floor 15.
Preferably,
where the root chamber floor 15 is entirely suspended from lines 31, for
example, the valve
outlet is positioned substantially centrally in the middle of the root chamber
floor 15. This is
because the suspended floor forms a catenary along its length and width so
that the outlet
will always be at the lowest point in the root chamber 14 (in an unfolded or
untilted
configuration).
The propagator 1 may be provided with grow lights. Grow lights are designed to
emit wavelengths of light necessary for the normal growth of plants. In
particular the grow
lights preferably emit red and blue wavelengths. For the red light, the grow
lights desirably
emit light at a wavelength of approximately 660 nm, more preferably
transparent over the
range of 645 to 700 nm and more preferably transparent over the range of 630
to 740 nm.
For the blue light, the grow lights desirably emit light at a wavelength of
approximately
460 nm, more preferably transparent over the range of 450 to 475 nm and more
preferably
transparent over the range of 440 to 490 nm.
The grow lights may be attached to beams 51, (see Fig. 5) which rest on power
cables 22, provided above the propagator, and can be spaced according to the
type of lamps
used. The power cables 22 may be supported by the end frames 11, as shown in
Figs. 1-3.
Preferably the grow lights are provided in the form of low voltage DC lamps.
The position of the grow lights is preferably adjustable so that, in use, the
light from
the grow light falls on the outer film 35 at or near a right angle to the
outer sheet 35 surface,
for example in the range of from 60 to 120 to the surface to the outer
sheet, although the
angle may need to be outside this range at the base of the outer sheet 35.
This allows as
much of the light as possible to be transmitted through the outer sheet 35,
instead of being
reflected away by the outer sheet 35. This in turn means the plants 16 in the
propagator 1
receive as much light as possible for photosynthesis. The position of the grow
lights may be
adjustable, for example, by being provided on a movable joint such as a ball
and socket
joint.
Figs. 5 and 6 illustrate the use of collection gutters 52 on the outer film
35.
Aeroponic systems create high humidity environments that will sometimes lead
to
condensation on the inside of the plastics film enclosures. Gutters 52 provide
a means for
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collecting this water, which can then be recycled. Similarly, the gutters 52
can be used to
collect rain water and dew from the outer surface of the outer film 35, and
this may also be
collected and stored, for example, in plastic flexibags which are laid on the
ground below
the propagators 1.
The propagator 1 could also be built on levelled ground where the chamber 14
is not
suspended above the ground. Figs. 8 and 9 show examples of such propagators.
Fig. 8 shows two propagators 1 that do not have an outer sheet 35. The right-
most
propagator 1 has a single upper support member 12, whilst the left-most
propagator 1 has
two upper support members 12. As such, the right-most propagator 1 has a root
chamber
with a triangular cross-section, whilst the left-most propagator 1 has a root
chamber 14 with
a trapezoidal cross-section.
Compared with the propagators 1 depicted in Figs. 1-7, the propagators of Fig.
8
have inner sheets 13 that reach all the way to the ground. The film 13 may be
in direct
contact with the ground, or there may be an intermediary layer 81 between the
sheets 13 and
the ground. The intermediary layer 81 may be some form of geo-textile ground
sheet or a
layer of gravel, for example.
In Fig 8, the film 13 is held in position against wind loads and the weight of
plants
16 inserted in it by tubes 82 filled, or partially filled, with loose soil or
water. Water is the
preferred medium in partially filled tubes 82 if regular access is required to
the root chamber
14. This is because the water may be easily removed and re-filled, and is
cheap. These
tubes 82, are preferably sufficiently flexible to conform to ground
irregularities and seal the
grow chambers against the impervious ground sheet 81 to prevent the loss of
pressurised air
and water fog or nutrient/water fog 54 from the root chamber 14. If desired
the tubes 82 can
be secured to the ground with metal or plastics pegs preferably with tops that
hook over the
tubes 82 when they are fully pushed down into the soil beneath the ground
sheet 81.
Preferably, tubes 82 are formed integrally with sheet 13.
Alternatively, rather than the tubes 82, other means of weighting the sheet 13
down
to form the chamber 14 may be used. However, any such means is preferably
releasable, to
allow access to the root chamber 14.
The propagators 1 in Fig. 8 may be tilted and re-shaped as previously
discussed for
the propagators 1 of Figs. 1-7, to allow access between propagators 1 and
additionally to
control the spacing of the plants relative to the ground. In addition, the
inner sheets 13 may
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be re-positioned so as to change the shape of the root chamber 14 to allow
easier access
between propagators 1 arranged in parallel.
In particular, in the propagators shown in Fig. 8, there is a particularly
advantageous
method of re-shaping the root chambers 14 when the tubes 82 filled with water
are used to
seal the sheet 13 against the ground. The propagators 1 may be arranged such
that there is
slack available in the support lines 12 when the propagators 1 are in the
configurations
shown in Fig. 8. In that case, when the line or lines 12 are further
tensioned, the inner sheet
13 will be raised. Preferably, the inner sheet 13 may be raised by around
50cm.
As this operation is carried out the fluid-filled tubes 82 holding down sheet
13 are
drained of water, and the lifting action causes the film 13 to swing inwards
towards the
centre line of the chamber 14 and hang substantially vertically. This
operation frees space
between closely spaced propagators 1, so aeroponic farmers have room to gain
access to
crops growing up the film 13 faces of the propagators 1. When access is no
longer required,
the film 13 can be lowered and stretched tight, to drop onto the ground sheet
81. After the
fluid is replaced in tubes 82, the chamber 14 is thus secured back in position
and the two
sloping faces of the chamber 14 are recreated.
In Figs. 1-7, the fog return tube 24 (part of the fogging system described in
more
detail below) is shown beneath the chamber 14. In Fig. 8 the fog return tube
24 rests on the
bottom of the root chamber 14.
As in Figs 1-7, the chamber 14 of the propagators 1 in Fig. 8 may be provided
with a
base, for example in the form of a tray resting on the ground or intermediate
layer 81. Such
a tray may also be used for the cultivation of an energy crop 53 or mushrooms
(as shown in
Fig. 6).
Fig. 9 depicts two propagators using the double-film construction (i.e. having
both an
inner film 13 and an outer film 35). As discussed before, such a configuration
may be
desirable in potentially hostile growing environments, and/or where it is
necessary to be able
to control growth conditions in order to optimise the speed of plant growth
and the quality of
produce (e.g. for the organic food market). As in Fig. 3, the outer sheet 35
is suspended
from lines 37. The outer sheet 35 is further weighted at ground level in a
similar way to the
inner sheet 13, for example using filled plastics tubes. Duckboards 91 may be
laid over
these tubes to allow farmers to move between propagators 1.
The outer sheet 35 creates a protected plant space in which the above ground
parts of
plants 16 can grow without being attacked by birds or insects, damaged by
dust, dirt, sand or
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hailstones, or to enable foliar feeding, or to protect from other
contamination such as
chemical or radioactive incidents, or additionally to house a flow of air past
sensors
positioned at the exit to the foliage chamber where the sensors would be in
communication
with a control system. As such, this configuration is of use in outside
conditions.
Of course, although Figs. 8 and 9 depict the propagators 1 on perfectly
levelled
ground, this is not necessary. The system will work on a brownfleld site,
sand, rooftop or
even potentially on water if suitable supporting frames are used.
As with the suspended propagators 1, power cables 22 and light beams 51 may
also
be provided for the non-suspended propagators of Fig. 8 and Fig. 9.
As already mentioned, the propagators of Figs. 1-9 are provided with fogging
systems to provide a fog within the chamber 14. This is now described in more
detail with
reference to Figs. 10 and 11.
A fog of water, preferably containing plant nutrients and enhancing additives
is made
in a fogger unit 23, which may comprise a nebuliser, for example. The fog may
be produced
by forcing nutrient-containing water through nozzles by a pump. The fog can be
passed into
the root chamber 14 and this fog is taken up by the roots, and/or can be
passed into the
foliage chamber 55 to allow nutrients to be absorbed by the foliage. Several
fogger units 23
may be required along the length of a propagator 1 if the propagator 1 is
long. The nutrient
composition in the fog can be changed to optimise growth. This is done by the
fogger/fan
control box 23, which also controls the pump/fans. The fog can optionally be
condensed
and returned to the fogger unit 23 in the return tubes 24. Preferably, to
maintain optional
growth conditions, the fogger unit 23 is provided with a backup power supply.
In some cases only a single fogger unit 23 is required for a single propagator
1. In
other cases, multiple fogger units 23 can be provided for a single propagator
1 or a single
fogger unit 23 can supply multiple propagators 1.
The fogger/fan control unit 23, see Fig. 10, may be in the form of a large
weather-
proof box containing a variable speed fan, water/nutrient pressure pump,
heater and/or
cooler, water and nutrient suction pump, grow light control unit, fog nozzles,
nutrient/water
tank, a water/nutrient degassing unit, and computer control system. As
previously
mentioned, the control system may be linked to sensors measuring growing
conditions
inside the root chamber 14, and a control system may also be linked to sensors
measuring
growing conditions in the foliage chamber 55 and where such sensors can also
provide
feedback control to the control system. Sensors can be used to monitor
conditions such as
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air temperature, air speed, leaf turgor, humidity, nutrient and water pH,
nutrient and water
levels in the storage taffl( and daylight levels. The control unit 23 may be
linked with RFID
(Radio Frequency Identification) chips attached to the plants 16 to monitor
and control the
growth of the plants 16. The control unit may be linked to a two-way radio
communication
system, for remote aeroponic system control and system failure alarm
functions.
The fog return tube 24 is preferably located centrally. Although shown
suspended in
Fig. 10, it may also rest either beneath or on the bottom of the root chamber
14 (as shown in
Fig. 11). The fog return tube 24 is preferably made from plastics film. The
fog return tube
24 is used for recycling excess fog and air from the far end of the root
chamber 14 (see Fig.
11) back to the fogger/control unit 23. This recycled fog is blown down the
fog return tube
24 by a variable speed fan 111, for example, located near to the end closer
panel 34 most
distant from the fogger/control unit 23, as shown in Fig. 11.
As previously mentioned, the closer panel 34 at the end of the propagator 1
that is
connected to the fogger/control unit 23 (as shown in Fig. 10) can contain
holes through
which fog can be discharged from the fogger unit 23 into the chamber 14, and
through
which the fog return pipe 24 can return recycled fog to the fogger unit 23.
The
fogger/control unit 23 may also be provided with ventilating fans that blow
air into the root
chamber through one or more further holes in the closer panel 34, and/or into
the foliage
chamber 55.
As also previously mentioned, the end panels 34 may be provided with a vent
flap
36. The vent flap 36 is preferably provided at the end of the propagator 1
opposite the
fogger/control unit 23. However, a vent flap may be provided at either or both
ends
depending upon how it is desired to control the environment within the chamber
14. The
vent flaps 36 may be remotely controlled, as previously described. However,
the vent flaps
36 may also be mechanically free to open if the pressure inside the root
chamber 14
becomes too high. For example, the vent flaps 36 may be suitably weighted so
that they
automatically open due to the pressure inside the root chamber 14 when that
pressure
becomes too high. The provision of vents 36 in this way allows for the root
chamber 14 to
be maintained at the correct conditions, whilst making it difficult for
insects to enter the
chamber 14.
The fog return pipe 24 may be suitably arranged so that flow back through the
pipe is
assisted by the variable speed fan 111. In addition, the fog return pipe 24
may be suitably
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angled so that flow of any condensed liquid towards the fogger/control unit 23
is assisted by
gravity.
Any liquid that does not advance into the fog return pipe 24 may be captured
in a
dew/condensate sump 112 that is connected to a suction pump on the fan/fogger
control unit
23.
The end frames 11 in Figs. 10 and 11 are shown attached to screw pile ground
anchors 101. However, the end frame members 11 may be secured to the ground by
any
suitable method. Figs. 10 and 11 also show grow lights 102 connected to power
cable 22.
The fogger/control unit 23 shown in Figs. 10 and 11, or alternatively a second
fogger/control unit, may also be used to supply a fog to the foliage chamber
55 between the
inner sheet 11 and the outer sheet 35 when the outer sheet 35 is present. The
control unit 23
can be arranged to supply water fogs containing water-soluble plant foods to
accelerate plant
growth to the foliage chamber 55. By creating a high humidity in the foliage
chamber 55,
the stomata of the plant foliage in the foliage chamber 55 are encouraged to
open. As the
stomata open, the plants 16 may absorb the nutrients from the fog in the
foliage chamber 55
at the same time as absorbing nutrients via their roots from the fog in the
root chamber 14.
It may be preferable to use a separate fogger/control unit 23 to differentiate
the size
of the fog droplets between the root chamber 14 and the foliage chamber 55.
Foliar feeding
is preferably conducted using fine fogs with median droplet sizes at least 1
micron up to 60
microns. The droplet size is desirably 20 microns or less, more preferably 10
microns or
less and still more preferably 5 microns or less. In contrast, root systems
prefer slightly
coarser droplet sizes and so a larger average droplet size may be desirable in
the root
chamber 14. To allow control of the droplet size, although this is not
necessary, energy-
efficient systems such as the Mist (RTM) Platform Technology by Swedish
Biomimetics
3000 Limited, of Stockholm, Sweden, can be used.
As with the root chamber 14, the pressure, temperature, humidity, etc, in the
foliage
chamber 55 may be monitored using sensors and the readings from the sensors
may be used
to control the supply of fog to the root chamber 14 and / or the movement of
air in the root
chamber 14.
Pure water fogs may also be supplied to the foliage chamber 55 for use as a
screen,
to protect the plants 16 from strong sunlight. Pure water fogs may also be
used to protect
the plants 16 from frost, by reducing radiation heat losses and allowing water
vapour in the
saturated air to condense onto leaves and release latent heat of fusion. This
is much more
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efficient than providing frost protection by direct heating, for example.
Protecting an acre
(approximately 4050m2) of orchard from frost by heating involves burning 20-40
gallons
(approximately 90-180 litres) of fuel an hour. Water fogs can produce the same
level of
frost protection using 0.05-0.15 gallons (approximately 0.2-0.7 litres) of
fuel (or electricity
equivalent) an hour per acre. These figures relate to fogs with median
particle diameters
ranging from 10-40 microns.
The control of the environments in the root chamber 14 and foliage chamber 55
may
desirably be performed in a closed loop system. That is, moisture and
nutrients from the fog
return tubes 24 may be re-cycled as fog again, with suitable nutrient
enrichment, and air
within the propagator could be recycled with suitable oxygen and/or carbon
dioxide
enrichment. Heat levels could be actively controlled using heating and cooling
units. Such
systems would be desirable when it is necessary to isolate the inside of the
propagator from
a contaminated external environment, for example after a chemical release or
nuclear
contamination.
It may be desirable to provide propagators 1 inside a larger covered
structure. In that
case, the propagators 1 can be configured without the second outer sheet 35.
However, it
may still be desirable to provide the outer sheet 35 for foliar feeding. Fig.
12 shows a
schematic plan of a covered installation comprising five propagators 1
arranged substantially
in parallel. As can be seen in Fig. 12, each propagator 1 is provided with its
own
fogger/control box. Arrow A indicates the direction of airflow within root
chambers 14 of
the propagators 1. Arrow B indicates the direction of airflow within the fog
return tubes 24
of the propagators 1. The propagators 1 are inside an overall cover 120, which
may be a
polytunnel or a greenhouse for example. The covering structure 120 has doors
121 to allow
access for workers and has ventilating vans 123 and exhaust vents 136 to allow
airflow
through the structure 120.
The propagators 1 may be further supplied with temperature controlled air such
as
heated air (which may be obtained from a waste heat source such as a
manufacturing plant)
or cooled air, and / or air rich in carbon dioxide (i.e. having a higher
concentration of carbon
dioxide than standard air). This air may be supplied to either the roots or
the foliage.
Higher carbon dioxide levels are known to enhance plant growth, and so the
carbon dioxide
rich air will assist in the growing of plants 16 in the propagator 1.
The carbon dioxide rich air may be obtained from any source, including waste
sources such as cement production or power plants. If the waste source is
local to the
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propagator, the waste carbon dioxide could be piped directly into the gap
between the inner
13 and outer 35 layers (i.e. the foliage chamber) or into the root chamber 14.
However, the
most benefit would be obtained by directing the carbon dioxide rich air to the
foliage
chamber 55. Desirably, the supply of carbon dioxide rich air is controlled in
response to the
-- carbon dioxide level detected by carbon dioxide monitors within the foliage
chamber. For
example, if the carbon dioxide monitors detect that the level of carbon
dioxide in the foliage
chamber is too low, the supply of carbon dioxide rich air into the foliage
chamber may be
automatically increased to increase the carbon dioxide levels. Once the level
of carbon
dioxide in the foliage chamber returns to a suitable level, the supply of
carbon dioxide rich
-- air may be automatically reduced. As such, the conditions inside the
foliage chamber can be
maintained for optimal growth. Once again, the specific parameters for
operating the
control system will depend on the most suitable conditions for the plants 16
being cultivated.
The control unit 23 may be further configured to control the supply of the
carbon
dioxide. Alternatively, a separate control mechanism for the supply of carbon
dioxide may
-- be supplied.
The propagator 1 may also make use of waste heat from local sources. Once
again,
waste heat may be piped between layers 13 and 35 (i.e. into the foliage
chamber 55) or
directly into the root chamber 14. Once again, the control of the supply of
waste heat could
be performed by the control unit 23, or a further control mechanism. The
supply of the
-- waste heat can be controlled in response to temperature sensors within the
propagator, to
avoid overheating the plants 16.
In some cases it may be desirable for the inner sheet 13 to have a pleated
arrangement. This is described below with reference to Figs. 16-20.
Fig 16 is a schematic perspective view of the pleated arrangement. As such,
the
-- structural supporting elements of the overall propagator 1, such as the end
frames 11, are not
shown. However, the pleated arrangement may be used with any of the structural
configurations of the propagator 1 previously discussed.
As can be seen, the inner sheet 13 is provided with pleated sections 161
running
lengthwise along the propagator 1. That is, the pleats 161 run substantially
parallel to the
-- supporting members 12 and 31.
The pleats 161 form lengthwise pockets or slits in the inner sheet 13, which
are open
on the outer surface of the inner sheet 13. That is, the pleats 161 hang
inside the root
chamber 14.
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Fig. 17 depicts one way in which the pleats 161 can be formed and supported.
Two
'C' channels form a structure 171, which forms part of a framework on which
pleat-
supporting members 175 can be provided. In some arrangements, the end frames
11 may act
as structures 171, as part of the pleat-supporting framework.
The structure 171 of Fig 17 can be anchored to the ground and/or supported by
support members 31 and/or attached to certain elements of the end frame. A
joint 172 can
be formed between the two 'C' sections at support member 12. The joint 172 can
be a
hinge, for example a fabric hinge, which may be notched to enable support
member 12 to
slide above or adjacent to it into the desired location. The two sections of
the structure 171
can be locked into position relative to each other by a locking means 174 such
as a bolt that
extends through both 'C' sections.
The pleat-supporting members 175 can be ropes or lines or any other suitable
supporting member as previously described with reference to support members 12
and 31.
In Fig. 17, ropes or lines 175 extend between at least two structures 171,
only one of which
is shown, and each line 175 passes through a hole in the depicted structure
171. The end of
each of the lines 175 is attached to a weight 176 to keep the line 175 in
tension. A similar
arrangement may be used at the other end of each line 175.
Alternative tensioning methods could be used. For example, a line 175 can be
wedged in place with a peg through the hole in the structure 171. In some
cases, for
example when using three structures 171 spaced so that one structure 171 is in
the middle of
the propagator 1, it may be desirable to fixedly attach (e.g. via a knot when
using a rope or
line) the line 175 to the central structure 171.
In Fig. 18, the pleat-supporting members 175 are provided in pairs. This
allows the
formation of a pleat 161 in the inner sheet 13 by pulling or pushing a section
of the inner
sheet 13 through the gap between the pair of pleat-supporting members 175. In
effect, a
pocket of the material of the inner sheet 13 is created inside the root
chamber 14, so that the
pocket opens to the outer surface of the inner sheet 13.
One way to hold the pleats 161 in place is to use clips or some other
fastening means
at suitable intervals to attach sheet 13 to the pleat-supporting members 175.
Fig. 19 shows
an example in which a tape 162 is used to fasten across multiple pleats 161.
The tape 162 is
attached by a means such as welding, gluing or stitching to the sheet 13. By
applying the
tape 162 across the pleats 161, the pleats 161 are held in position and do not
fall out if a
lower section of the sheet 13 is pulled or weighted down with plants 16, for
example.
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An alternative configuration to that depicted would be to provide an inner
sheet 13 in
which the pleats 161 are pre-formed. For example, the sheet 13 could be
manufactured with
the pleats 161 formed and held in place by a means such as welding, gluing or
stitching at
periodic intervals along the pleat 161, or with tape 162 already in place. In
such a case, the
pleat-supporting members and the structures 171 may be omitted from the
propagator 1 if
the pleats 161 are held together strongly enough.
The pleated arrangement has several advantages.
As shown in Figs. 20a and 20b, the pleats 161 can act as a channel for
locating seeds,
seedlings or seed or plant-bearing porous media (such as a cellulose fibre
seed stick 201), or
as a channel where the roots or tubers of root crops such as potatoes or
carrots can be
carried. The support of the pleat 161 helps avoid the roots and tubers pulling
on the rest of
plant 16, as may happen if they hang free in chamber 14. Alternatively, the
roots / tubers
can be located in the root chamber 14, with only the foliage located in the
pleat 161.
The pleats 161 can also help to collect rainwater 191 (where there is no outer
sheet
35) and dew or condensed fog. This is shown in Fig. 19.
To allow access between the pleats 161 and the root chamber 14 (i.e. so that
the
nutrient fog 54 in the root chamber can still be absorbed by plants 16 whose
roots are
supported in the pleats 161), there are various possibilities. The pleats 161
may be formed
from a material that allows the transmission of the moisture and nutrients.
The pleats 161
can be provided with perforations 192 on the bottoms and / or sides of the
pleats 161, as
shown in Figs 18 and 19. Such perforations would still restrict or prevent
light penetrating
into the root chamber, so as to maintain the inner sheet 13 as being
substantially opaque and
thus preventing algae growing on plant roots (which would use water and
nutrients
otherwise available to plant roots), and also would still inhibit the escape
of fog.
Alternatively the pleat 161 may be made of a different material to the bulk of
the
inner sheet 35 such as a netting material 202 as shown in Fig. 20b. One
advantage of using
a fibrous seed stick 201 in such a situation (which could be made from various
materials, for
example cellulose, as mentioned above) is that it helps fill the pleat 161 and
therefore assists
in preventing light from reaching the root chamber when the pleat 161 material
is not itself
opaque. Alternatively, the inner sheet 35 may be maintained as providing a
substantially
opaque covering for the propagator by providing only a narrow opening for the
pleat 161 on
the outer surface of the inner sheet 13.
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The present invention has been described above with reference to specific
embodiments. It will be understood that the above description does not limit
the present
invention, which is defined in the appended claims.
