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1999-03-01
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Grant, J., Staunton, L., Integrated environmental control in mushroom tunnels, End of Project Report, Teagasc, 1999.
Abstract
The main objective of this investigation was to achieve improved
control of the micro-climate around the mushroom crop. The work was
based on two approaches. One, which required the greater part of the
work, was gaining an understanding of the characteristics/physics of the
climate control system as a whole within mushroom tunnels and the other
was the application of modern control strategies to manipulate more
effectively the conditions at the cropping surface.
The work showed that the influences of the operation of the air
conditioning on the crop micro-climate was far greater than the expected
adjustment of, say, temperature and that novel systems and improved
measurement of the micro-climate were required in order to optimise the
control of air conditions.
The operation of the heating system caused a load dependent, i.e.
seasonal, variation in the average drying power of the air at the crop.
While heating (on/off control) was in operation, air flow effectively
ceased at the cropping surface and the effect persisted for the duration of
the heating and a recovery period afterwards. Various simple strategies
could be implemented to minimise these effects but a novel design for air
distribution provided a means of eliminating the effect.
Because of the complex relationship between the delivery of
conditioned air and the consequent flow at the cropping surface,
improved feedback from the crop micro-climate was found to be essential
for improved control. A new sensor was developed in conjunction with
the Department of Electronic Engineering, NUI Galway that provided a
low cost measurement of the very low air speeds used in mushroom
growing.
The Irish mushroom-growing system (bags and tunnels) offers
more potential for accurate control than other, tiered, growing systems.
The goal of the second aspect of this project was the provision of an
accurate and robust control system for mushroom tunnels. Work focused
on the control relationships between inputs and outputs of the system. A
Teagasc Walsh Fellowship supported the early work which was carried
out in conjunction with the Department of Electronic Engineering at NUI,
Galway. Initial work prior to this project, with control specialists in DIT,
Kevin Street College of Technology, was extended to provide a
mathematical/control model of the main physical processes involved. A
second Walsh Fellowship supported a link with the control systems group
in the Department of Electronic Engineering, Dublin City University and
allowed further control studies in mushroom tunnels.