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Full Length Research Paper
Constructions, applications, food preservation and the
environment of Greenhouses
Abdeen Mustafa Omer
17 Juniper Court, Forest Road West, Nottingham NG7 4EU, UK
Email: abdeenomer2@yahoo.co.uk
Received 06 January 2012; Accepted 28 January 2012
A
greenhouse is essentially an enclosed structure, which traps
the short wavelength solar radiation and stores the long
wavelength thermal radiation to create a favourable
microclimate for higher productivity. The sun’s radiation
incident on the greenhouse has two parts: direct radiation
and an associated diffuse sky radiation. The diffuse part is
not focused by the lenses and goes right through Frensel
lenses onto the surface of the absorbers. This energy is
absorbed and transformed into heat, which is then
transported via the liquid medium in copper pipes to the
water (heat) storage tanks or, if used, open fish tanks. In
this way, an optimal temperature for both plant cultivation
and fish production can be maintained. Stable plant growth
conditions are light, temperature and air humidity. Light
for the photosynthesis of plants comes from the diffuse
radiation, which is without substantial fluctuations and
variation throughout most of the day. The air temperature
inside the greenhouse is one of the factors that have an
influence on the precocity of production. The selective
collector acts in a more perceptible way on extreme air
temperatures inside the greenhouse. Hence, the system makes
it possible to avoid the excessive deviation of the
temperature inside the greenhouse and provides a favourable
microclimate for the precocity of the culture. Sediment and
some associated water from the sediment traps are used as
organic fertiliser for the plant cultivation. The present
trend in greenhouse cultivation is to extend the crop
production season in order to maximise use of the equipment
and increase annual productivity and profitability. However,
in many Mediterranean greenhouses, such practices are
limited because the improper cooling methods (mainly natural
or forced ventilation) used do not provide the desired
micro-climatic condition during the summer of a composite
climate. Also, some of these greenhouses have been built
where the meteorological conditions require some heating
during the winter, particularly at night. The worst scenario
is during the winter months when relatively large difference
in temperature between day and night occurs. However,
overheating of the greenhouse during the day is common, even
in winter, requiring ventilation of the structure. Hence,
several techniques have been proposed for the storage of the
solar energy received by the greenhouse during the day and
its use to heat the structure at night. Reviews of such
techniques are presented in this study. Air or water can be
used for heat transport. The circulating water is heated
during the day via two processes. The water absorbs part of
the infrared radiation of the solar spectrum. Since the
water is transparent in the visible region, they do not
compete with the plants that need it. Alternatively, the
water exchanges heat with the greenhouse air through the
walls. At night, if the greenhouse temperature goes down
below a specified value, the water begins to circulate
acting as heat transfer surfaces heating the air in the
greenhouse. This communication describes various designs of
low energy greenhouses. It also, outlines the effect of
dense urban building nature on energy consumption, and its
contribution to climate change. Measures, which would help
to save energy in greenhouses, are also presented. It also
enabled the minimisation of temperature variation and, hence
avoided the hazard of any sudden climatic change inside the
greenhouse.
Keywords:
Greenhouse environment, energy efficient comfort,
ventilation, humidity, sustainable environmental impact.
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