| dc.description.abstract | Adoption of greenhouse technology in hot and arid areas in north-west India
is impeded by lack of good quality water. Besides irrigation, evaporative cooling uses
large amounts. Provision of natural ventilation and coupling the house to earthtube-heat-exchanger
(ETHE) is being tried as alternative measures for
environmental control, specially cooling. The experimental facility, located in arid
region at Kothara (ϕ 23° 14 N, λ 68° 45 E, at 21 m a.s.l.), is a single span saw-tooth
greenhouse (20 X 6 X 3.5 m) coupled in closed- loop to ETHE buried 3m deep
directly below. ETHE provides 40 air changes per hour. For natural ventilation,
there are three continuous (closable) vents - two along the base of long sides and one
on the roof. A retractable shading cover is provided over the roof. The aim was to
determine (a) the extent to which ETHE and natural ventilation meet the need for
environmental control and the associated costs (b) the extent to which the yields
increase and cropping season extended. ETHE was able to heat the greenhouse
easily from 9°C to 22-23°C in half hour in the cold winter nights. Natural ventilation
along with roof shading was effective for day time control till February keeping the
temperature about 34°C inside. Subsequently, ETHE was operated. It limited the
greenhouse temperature to 36-37°C with top shaded. ETHE and natural ventilation
hold promise as environmental control measures. There is need to reduce
installation cost of the ETHE. A more easily scalable design than the present one is
also desirable. | |
