7 / 11
allied
academies
Page 31
Journal of Nutrition and Human Health | Volume 3
J Nutr Hum Health, Volume 3
November 21-22, 2019 | Singapore
Clinical Nutrition and Fitness
17
th
International Conference on
Greenhouse gardening for food production and the environment
Abdeen Mustafa Omer
Energy Research Institute (ERI), UK
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 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
belowa specified value, thewater begins to circulate acting as
heat transfer surfaces heating the air in the greenhouse. This
chapter describes various designs of lowenergy 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 greenhouses.
e
:
abdeenomer2@yahoo.co.uk