DigitalFoodDesert
Uploaded on Nov 20, 2011
Aquaponic greenhouse 12ft deep x 8ft wide x 8ft high constructed of wood, cow fence wire and 6 mil plastic film.
A
greenhouse (also called a
glasshouse) is a building in which
plants are grown. These structures range in size from small sheds to industrial-sized buildings. A miniature greenhouse is known as a
cold frame.
A greenhouse is a structural building with different types of covering materials, such as a
glass or
plastic
roof and frequently glass or plastic walls; it heats up because
incoming visible solar radiation (for which the glass is transparent)
from the sun is absorbed by plants,
soil,
and other things inside the building.
Air warmed by the heat from hot
interior surfaces is retained in the building by the roof and wall. In
addition, the warmed structures and plants inside the greenhouse
re-radiate some of their thermal energy in the infrared spectrum, to
which glass is partly opaque, so some of this energy is also trapped
inside the glasshouse.
However, this latter process is a minor player
compared with the former (convective) process. Thus, the primary heating
mechanism of a greenhouse is
convection.
This can be demonstrated by opening a small window near the roof of a
greenhouse: the temperature drops considerably.
This principle is the
basis of the
autovent
automatic cooling system. Thus, the glass used for a greenhouse works
as a barrier to air flow, and its effect is to trap energy within the
greenhouse. The air that is warmed near the ground is prevented from
rising indefinitely and flowing away.
Although heat loss due to
thermal conduction through the glass and other building materials occurs, net energy (and therefore temperature) increases inside the greenhouse.
Types
Greenhouses can be divided into glass greenhouses and plastic greenhouses. Plastics mostly used are
polyethylene film and multiwall sheets of
polycarbonate material, or PMMA
acrylic glass.
Commercial glass greenhouses are often high-tech production facilities
for vegetables or flowers. The glass greenhouses are filled with
equipment such as screening installations, heating, cooling and
lighting, and may be automatically controlled by a computer.
Netherlands
The
Netherlands
has some of the largest greenhouses in the world. Such is the scale of
food production in the country that in 2000, greenhouses occupied 10,526
hectares, or 0.25% of the total land area.
[citation needed]
Greenhouses began to be built in the
Westland
area of the Netherlands in the mid-19th century. The addition of sand
to bogs and clay soil created fertile soil for agriculture, and around
1850, grapes were grown in the first greenhouses, simple glass
constructions with one of the sides consisting of a solid wall.
By the
early 20th century, greenhouses began to be constructed with all sides
built using glass, and they began to be heated. This also allowed for
the production of fruits and vegetables that did not ordinarily grow in
the area. Today, the Westland and the area around
Aalsmeer have the highest concentration of greenhouse agriculture in the world.
[citation needed]
The Westland produces mostly vegetables, besides plants and flowers;
Murno Gladst is noted mainly for the production of flowers and potted
plants. Since the 20th century, the area around
Venlo and parts of
Drenthe have also become important regions for greenhouse agriculture.
Since 2000, technical innovations include the "closed greenhouse", a
completely closed system allowing the grower complete control over the
growing process while using less energy. Floating greenhouses
[clarification needed] are used in watery areas of the country.
The Netherlands has around 9,000 greenhouse enterprises that operate
over 10,000 hectares of greenhouses and employ some 150,000 workers,
efficiently producing €4.5 billion worth of vegetables, fruit, plants,
and flowers, some 80% of which is exported.
[citation needed]
Young tomatoes in an industrial-sized greenhouse in the Netherlands
Source: Wikipedia
TTFN
CYA Later Taters
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Donnie/ Sinbad the Sailor Man
