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Insights Nutr Metab 2017
Volume 1 Issue 3 Nutrition World 2017
Page 68
September 11-12, 2017 Edinburgh, Scotland
15 th World Congress on
Advances in Nutrition, Food Science & Technology
Greenhouses for food production and the
environment
Abdeen Omer
Environmental Research Institute, UK
Agreenhouse 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 chapter. 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 chapter 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.
Insights Nutr Metab 2017