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Greenhouse (constructed in 2000)
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Greenhouse (constructed in 2003)
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Flooring
A heavy duty weed mat is used for flooring. It is porous
and allows moisture to penetrate which alleviates puddles
and avoids slipping.
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Greenhouse (constructed in 2000)
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Greenhouse (constructed in 2003)
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There are two layers below the roof
of the greenhouse which assist in maintaining optimum
light and temperature within the greenhouse.
Polythene screens
This has never been used in other greenhouses but has
been installed in the new greenhouse to keep the gas
heating in during winter. It is used to maintain the
heat in winter. Air mixers have not been installed because
of the in- built ventilation. Their requirement will
be monitored.
Aluminum screening
Alumunium screening is used to maintain the temperature.
At daytime it keeps the heat/light out and at night
it keeps the warm air in. It has a benefit in saving
energy. Screens allow up to 50% shading. When light
and temperature reach a set point the screen closes
( to keep it cool in summer for capsicums)
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Greenhouse (constructed in 2000)
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Greenhouse (constructed in 2003)
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The internal environment of the greenhouse
is controlled by 4 side windows and two roof vents per
bay which can open and close depending on wind, rain,
temperature and humidity. Force ventilation can be executed
on demand either by timer or sensors.
The polycarbonate roof blocks 100% of UV radiation (this
is no good if bees are required for pollination). It
lasts for 20 years (it comes with a 10 yrs guarantee
on light transmission). Plastic is not recommended because
of its 70% drop in light transmission over 3 years and
a consequent decrease in winter production. Plastic
is also a health hazard at time of construction. The
shape of the greenhouse gives maximum light at any time
of the day.
The top ventilation (double) gives maximum ventilation
at the highest part of the greenhouse and provides a
venturi system that sucks the air out of the opening.
The vent controls the amount sucked out, but is also
wind dependant.
The high roof gives enough volume of air to buffer the
environment.
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| Tanks that collect drainage from
gullies and through the control system, monitors electrical
conductivity in order to adjust the concentration of salts
(fertilisers) and water. |
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| Fertilisers are mixed in tanks and
added to the water depending on salt concentration in
the water. |
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Irrigation gullies in the new greenhouse
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| UV Sterilisation Unit |
Reverse Osmosis Unit |
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This unit sterilises up to 40,000
l per day. Sterilisation is fully automatic and includes
checking the UV screen, washing the filter and adjusting
the radiation level. It has an auto cleaning function,
alarms and needs to be checked only once per day. The
sterilisation unit is a Dutch product sold by Netafim.
The unit needs to be calibrated and the water quality
needs to be monitored.
The unit works well. Kill is controlled on a flow rate
of 50% kill at 5 cubic meters/hour and a 100% kill rate
at 3 cubic meters per hour.
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| This unit cleans the bore water for
use within the hydroponic system. It only removes salts
from the water prior to fertiliser injection. |
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