Table 1.
The specifications of the sensors used in the control system.
Fig 1.
The arrangement of the sensors in a sensor unit.
Fig 2.
Suggested arrangement of the sensor nodes inside a rectangular-shaped greenhouse.
Fig 3.
Power distribution plan of the system.
Fig 4.
The overall system architecture of the system.
Fig 5.
A few views of the IoT Dashboard: (a) Home screen (b) Current status view (c) Greenhouse sensor arrangement (d) Sensor data visualizer.
Fig 6.
Cross Sections of the Polytunnels used during the research (a) Polytunnel with the control system; (b) Polytunnel without the control system.
Fig 7.
View of the two polytunnels: (a) Polytunnel with the control system; (b) Polytunnel without the control system.
Table 2.
Comparison of the polytunnels used for the experiment.
Fig 8.
Variations of meteorological parameters among the eight sensor nodes in the polytunnel with the controlling system for three representative dates.
(a1) Temperature; (a2) Relative humidity; (a3) Light (RH) on 19 October 2020. (b1) Temperature; (b2) Relative humidity; (b3) Light (RH) on 17 November 2020. (c1) Temperature; (c2) Relative Humidity; (c3) Light (RH) on 15 December 2020.
Fig 9.
Temperature variations in the three levels during different tomato growth stages.
(a) Vegetative stage. (b) 50% Flowering stage. (c) Fruits set the stage. (d) Ripen fruit stage. Level 1, Level 2, and Level 3 are 0.4, 1.2, and 2.0 m in height from the floor level respectively.
Fig 10.
Relative humidity variations in the three levels during different tomato growth stages.
(a) Vegetative stage. (b) 50% Flowering. (c) Fruits set the stage. (d) Ripen fruit stage. Level 1, Level 2, and Level 3 are 0.4, 1.2, and 2.0 m in height from the floor level respectively.
Fig 11.
Daytime average variations of temperature and relative humidity in the two greenhouses throughout the selected trial period.
(a) Temperature (b) Relative Humidity.
Table 3.
Maximum time duration (hours) taken to control the temperature in the polytunnel by blower fan and misters.
Fig 12.
Average values of temperature and relative humidity with and without plants.
(a1) Temperature; (a2) Relative Humidity on a typical sunny day. (b1) Temperature; (b2) Relative Humidity on a typical rainy day. (c1) Temperature; (c2) Relative Humidity on a typical cloudy day. D, N, and 24hr are daytime, nighttime, and 24 hours, respectively; Avg denotes average. L1, L2, and L3 are the sensor levels.
Table 4.
Environmental conditions of three selective sunny days in different greenhouse conditions.
Table 5.
Environmental conditions of five selective sunny days in different greenhouse conditions with/without plants.